Impact of Humidity on Deformations Offr-4 Based Detector

Impact of Humidity on Deformations of FR-4 Based Detector Elements in the ATLAS New Small Wheel

Yanwen Hong

Supervisor: Prof. Dr. Ulrich Landgraf Dr. Stephanie Zimmermann

Fakultät für Mathematik und Physik Albert-Ludwigs-Universität Freiburg

This dissertation is submitted for the degree of Master of Science

Abteilung Prof. Dr Gregor Herten July 2019

Abstract

The discovery of the Higgs boson in the ATLAS and CMS experiments showed the necessity of high luminosity in discovering new physics. The LHC is undergoing upgrades of the collider, accelerator chain and detectors for the High-Luminosity LHC project in several phases. The inner endcap of the muon spectrometer in the ATLAS detector will be replaced by the New Small Wheel. The two technologies used in the NSW are sTGC and MicroMegas, which can achieve a high spatial resolution in muon tracking and better angular resolution in trigger performance by implementing strip-structured detector modules. FR-4 grade PCBs are one of the crucial components of the detectors. Mechanical deformations caused by a humid environment were observed during the single layer detector element machining and detector module assembly processes. These deformations will lead to strips misalignment and furthermore have a direct impact on resolution of the detectors. In order to evaluate the impact of these deformations on the performance of the detector, a designed humidity study is conducted in this thesis. The maximum and residual strip misalignment of three detector elements at an extremely humid environment and after the air-drying process is determined by measurement data. Considering the machining and manufacturing process, the values of mechanical tolerances of the detector modules are compared to the maximum and residual strip misalignment.

Contents

1 Introduction 1

2 New Small Wheel Project in Phase-I Upgrade of the ATLAS Experiment 3 2.1 Large Hadron Collider and the ATLAS Detector ...... 4 2.1.1 The Muon Spectrometer ...... 6 2.1.2 Trigger System ...... 7 2.2 The New Small Wheel Upgrade Project ...... 8 2.2.1 Motivation of the NSW ...... 9 2.2.2 Detector Technologies of the NSW ...... 10 2.3 Operating Environment and Construction of the Investigated Elements . . . 13

3 Experimental Setup 17 3.1 The Humidiﬁcation Chamber ...... 17 3.2 The Gas Input System ...... 19 3.3 The Thermo-Hygrometer ...... 20 3.4 The Mechanical Coordinate Measurement Machine ...... 22 3.5 Choice of Reference Spheres’ Positions and Measurement Coordinate System 24

4 Deformations of Production Line Detector Elements 29 4.1 Introduction of the Experiment ...... 29 4.2 Results of sTGC Strip Cathode Board S1 Module ...... 30 4.3 Results of MM Readout Panel with Stereo Strips SM2 Module ...... 43 4.4 Results of MM Readout Anode Boards with Eta Strips SE6, SE7, SE8 Modules 53

5 Summary 63

Appendix A Figures of the Results 65

Appendix B Technical Drawing and Data Sheets 69 Contents

References 75

List of Figures 77

List of Tables 81

vi Chapter 1

Introduction

The High-Luminosity Large Hadron Collider (HL-LHC) project aims to reach a peak instantaneous luminosity of 7.5 1034cm 2s 1 [1] to increase the potential of discovering · − − new physics, with operation beginning at 2026. To cope with this, the LHC is undergoing extensive upgrades of the collider, accelerator chain and detectors in order to achieve data collection with high statistics in a short timescale. The ﬁrst phase of the upgrade is planned during the Long Shutdown (LS2) in 2019-2020. One of the multipurpose detectors, the ATLAS is now undergoing upgrades of all sub-systems for a new trigger and data acquisition architecture. For the muon spectrometer, besides the power system and electronics, the innermost endcap Small Wheel (SW) will be replaced by New Small Wheel (NSW). The NSW will be able to reduce the fake trigger rate and perform a precision track measurement of muons at a high radiation background. This leads to great improvements in the investiga- tion of the leptonic signatures of the Higgs Boson, as well as for super-symmetric particles (SUSY), and in the search for heavy and beyond standard model (BSM) particles.

The NSW utilises two detector technologies: small-strip Thin Gap Chamber (sTGC) for a precise trigger signal and Micro Mesh Gaseous Detector (MicroMegas, MM) to obtain a high spatial resolution in the muon tracks. These demanding goals are achieved by a complex construction of the detectors. Readout boards, which are one of the crucial parts of detector layers, are based on FR-4 material with copper readout strips. FR-4 is a grade designation for glass fabric reinforced epoxy laminate material. FR stands for ﬂame retardant, which is commonly used in Printed Circuit Board (PCB) production [2]. The readout boards in the NSW project are multi-layer materials with regular FR-4 PCBs produced in companies. Nu- merous studies have been done for the mechanical, electrical and physical properties of FR-4, for example ﬂexural strength and moisture absorption. However, the deformations of the FR-4 based detector elements caused by humidity exposure have not been precisely studied

1 yet. Mechanical deformations were observed during the single layer detector machining and detector module assembly processes. These deformations misplace the readout strip pattern and furthermore have a direct impact on the spatial resolution of the detector.

The aim of this thesis is to determine the shapes and dimensions of the deformations caused by a humid environment on the FR-4 based multi-layer detector elements in the NSW. To achieve this, a relatively gas-tight humidiﬁcation chamber and a gas input system for exposing the materials in a controlled humid environment were developed. Several reference spheres are glued on the surface of the detector elements according to speciﬁc patterns, to trace the geometry information. A mechanical Coordinate Measurement Machine (CMM) is used to give precise position values of the reference spheres up to a micrometer range. The 3D surface geometry model of each detector element is reconstructed from the position values to study and analyze the deformations.

The thesis is structured as follow. Chapter 2 gives a general introduction to the LHC, ATLAS detector, muon spectrometer and the two detector technologies of the NSW, as well as discusses the construction and operating environment of the three detector modules to be studied in this project. These are sTGC strip cathode board S1 module (FR-4 with copper strips and plane), MM readout anode boards with eta strips SE6, SE7 and SE8 modules (FR-4 with copper strips and Kapton foil), and MM readout panel with stereo strips SM2 module (FR-4 with copper strips and aluminum frame). Chapter 3 illustrates the experimental setup and explains the choice of measurement methods with the CMM machine. Chapter 4 describes experimental procedures and presents the results of observed deformations of the three elements, and gives reasonable evaluation of the maximal and residual deformations for further simulation and determination of the performance of the detectors.

2 Chapter 2

New Small Wheel Project in Phase-I Upgrade of the ATLAS Experiment

The Large Hadron Collider (LHC) colliders protons or ions to near the speed of light at a centre-of-mass energy √s = 13 TeV and an instantaneous luminosity of 1 1034 cm 2 s 1 × − − (2016). The ATLAS (A Toroidal LHC ApparatuS) experiment is one of four detectors at the LHC to identify the particles emerging from these collisions. Different detector subsystems and magnet systems are arranged in layers around the interaction point, aiming for the reconstruction of the paths, momentum and energy of the particles. The high- resolution muon spectrometer is the largest subdetector system. It provides with stand- alone triggering and momentum measurement capabilities over a wide range of transverse momentum, pseudorapidity, and azimuthal angle [3]. In order to cooperate with the higher particle rates at the High-Luminosity LHC (HL-LHC), LHC is will undergo upgrade in several phases. Phase-I upgrade of LHC will take place during the second long shutdown (LS2) in 2019/2020. The ﬁrst station of the ATLAS muon end-cap system (Small Wheel, SW) needs to be replaced. The New Small Wheel (NSW) will have to operate in a high background radiation region of up to 15 kHz/cm2 while reconstructing muon tracks with high precision as well as contributing for the Level-1 trigger [4]. The NSW uses two chamber technologies: small-strip Thin Gap Chambers (sTGC) are primarily devoted to the Level-1 trigger function, as well as to measure ofﬂine muon tracks with good precision; while MicroMegas detectors (MM) are primarily dedicated to precision tracking.

3 2.1 Large Hadron Collider and the ATLAS Detector

2.1 Large Hadron Collider and the ATLAS Detector

In the LHC, two beams of up to 1011 protons per bunch travel inside 26.7 kilometers circum- ference beam pipe at close to the speed of light, guided by superconducting electromagnets. They collide 11 thousands times per second at designed centre-of-mass collision energy √s = 14 TeV and instantaneous luminosity 1 1034cm 2s 1. The four collision point are × − − equipped with detectors. They are ATLAS and CMS (Compact Muon Solenoid), as general purpose detectors, ALICE (A Large Ion Collider Experiment), and LHCb (Large Hadron Collider beauty). To cover the full solid angle, the ATLAS detector uses a cylindrical conﬁguration around the collision point with a central barrel and end-caps on either side. It has a diameter of 25 m, a length of 44 m and weighs approximately 7000 t. The overall ATLAS detector layout is shown in Figure 2.1.

Fig. 2.1 Illustration of the subsystems in the ATLAS detector. Figure taken from CERN Document Server.

The coordinate system and nomenclature used to describe the particles of the experiment are illustrated in Figure 2.2. The origin of the coordinate system is deﬁned as interaction point (IP). The z-axis is the beamline, while the xy-plane is transverse to it. The positive orientation of x-axis points from the IP to the center of the LHC ring; while the positive y-axis points vertically upwards. In terms of the cylindrical coordinate system, the transverse

4 New Small Wheel Project in Phase-I Upgrade of the ATLAS Experiment plane is often described as r-φ coordinates. The azimuthal angle φ is measured from the x-axis around the beam. The radius r measures the distance from the beamline. The polar angle θ is defined as the angle from the z-axis. The polar angle is often also given in terms of the pseudo-rapidity, defined as η = ln tan(θ/2). Along the beam axis, the polar angle − is zero while the pseudorapidity value approaches to infinite. In the case of massive objects such as jets, the rapidity y is used. It is defined for a particle with energy E, momentum p and longitudinal momentum pL = p sinθ along the beam as: | | 1 E + p y = ln L 2 E pL −

The transverse momentum pT, the transverse energy ET , and the missing transverse energy miss ∆ ET are deﬁned in the xy-plane. The distance R in the pseudorapidity-azimuthal angle space is deﬁned as ∆R = »∆η2 + ∆φ 2.

Fig. 2.2 Cartesian and cylindrical coordinate system of the ATLAS experiment. Figure taken from [5].

The ATLAS detector is a complex machine consisting of many different subdetectors with different tasks in particle reconstruction and identification. The inner detector (ID) around the IP is immersed in a 2 T solenoidal field. Trajectories of charged particles get bent by the magnet field, which allows momentum measurement in the transverse plane of the detector. Besides, pattern recognition, vertex measurements, and electron identification can be achieved with a combination of a few discrete high-resolution semiconductor pixel detector layers. The next layer is calorimeters. It consists of the electromagnetic and the hadronic calorimeter. Electrons and photons are stopped in the electromagnetic section to measure the energy, while the hadronic section is needed to determine the energy of hadrons. High granularity liquid-argon (LAr) technology with excellent performance in energy and position resolution is used in the electromagnetic calorimeter and the hadronic end-caps calorimeter.

5 2.1 Large Hadron Collider and the ATLAS Detector

The barrel region of the hadronic calorimeter is made of a novel scintillator-tile. The overall miss calorimeter system provides good jet and ET performance. Since the muons behavior as minimum ionizing particles, most of them penetrate the calorimeters and reach the outermost part of the detector: the muon spectrometer.

2.1.1 The Muon Spectrometer

The muon spectrometer measures the tracks and momenta of muons, and at the same time provide fast information to the ﬁrst trigger level. A large toroidal magnet and four different kinds of chamber technologies are applied. The toroidal magnet ﬁelds provide bending powers of 3 Tm in the barrel and 6 Tm in the end-cap regions. Figure 2.3 shows the layout of a quadrant of the muon spectrometer in yz-plane. Combined with Figure 2.1, one can see the barrel chambers form three cylinders concentric to the beamline. The end-cap chambers are arranged as disk shape perpendicular to the beamline on both sides of the cylinder. All chambers offer complete coverage of the pseudorapidity range 0 < η < 2.7. | |

MDT chambers 12 m Resistive plate chambers

Barrel toroid coil 8

Thin gap 6 chambers

4 End-cap toroid

2 Radiation shield Cathode strip chambers 0 20 18 16 14 1210 8 6 4 2 m Fig. 2.3 Side view along the beamline of a quadrant of the muon spectrometer. Figure taken from [3]

Monitored Drift Tubes (MDT) are used in the barrel region and also in the outer end-cap regions for the precision measurement of muon tracks. Cathode Strip Chambers (CSCs) are employed for the same purpose in the innermost station of the end-caps. The trigger function in the barrel is provided by three stations of Resistive Plate Chambers (RPCs); they

6 New Small Wheel Project in Phase-I Upgrade of the ATLAS Experiment are mounted on the MDTs. In the end-caps, the trigger is provided by three stations of Thin Gap Chambers (TGCs) located near the middle MDT station.

2.1.2 Trigger System

With an interaction rate of 109 Hz at a luminosity of 1034 cm 2 s 1 in the LHC, the ∼ − − detectors are producing an enormous amount of data, and it is beyond the reach of the capabilities to store it. Online event selection of the trigger and data-acquisition system are essential. The ATLAS trigger system consists of a hardware Level-1 and a software-based high level trigger (HLT) [6]. The rate of selected events after the high level trigger must be reduced from 40 MHz to a few hundreds Hz for permanent storage. The Level-1 trigger uses front-end electronics to determine Regions-of-Interest in the detector. The Level-1 trigger reduces the event rate from the LHC bunch crossing rate to 100kHz.

Fig. 2.4 Schematic layout of the ATLAS trigger and data acquisition system in Run-2. Figure taken from [6]

7 2.2 The New Small Wheel Upgrade Project

Input data of Level-1 trigger system are received from the muon trigger chambers and from

the calorimeters. High pT muons are identiﬁed by trigger chambers. They are RPCs in the barrel, and TGCs in the endcaps. The muon trigger receives as input the pattern of hit strips in RPCs, and wire groups in the case of the TGC detectors in the muon trigger chambers.

2.2 The New Small Wheel Upgrade Project

Luminosity is an important indicator of the performance of an accelerator: it is proportional to the number of collisions that occur in a given amount of time. Enhanced luminosity allows the LHC experiments to provide more accurate measurements of Standard Model (SM) particles, enable observation of rare processes. This is the main motivation of the High Luminosity LHC project (HL-LHC), where the luminosity is planed to increase to 7.5 1034cm 2s 1 [1]. · − − In order to beneﬁt from the expected higher luminosity performance, a subsequent of upgrade of the LHC is planned. An overview of different upgrade stages is presented in Figure 2.5. During the second long shutdown (LS2) in 2019/2020, the Phase-I upgrade will take place. The ATLAS experiment has to maintain its capability to trigger on moderate momentum leptons under more challenging background conditions than present. For the muon spectrometer, the inner station of the ATLAS muon end-cap system (Small Wheel, SW) will be replaced as the New Small Wheel.

Fig. 2.5 Programme of the upgrade plans for the LHC baseline. Figure taken from [7]

8 New Small Wheel Project in Phase-I Upgrade of the ATLAS Experiment

2.2.1 Motivation of the NSW

The current SW mainly has two issues which limit the performance of the ATLAS. The ﬁrst one is, the efﬁciency and resolution of tracking performance degrade with increasing background rate in the inner end-cap station.

The second issue is, the high fake trigger rate of high pT Level-1 muon in end-cap region. The Level-1 muon trigger decision in the end-cap region is based on the track segments in the TGC chambers of the middle muon station located outside the end-cap toroid magnet.

The pT of the muon is determined by the angle of the segment with respect to the direction to the interaction point. Low energy particles, mainly protons, hit the end-cap trigger chambers at an angle similar to that of real high pT muons, and thus produce fake trigger signal. Figure 2.7 shows a comparison between the number of triggered muons and the number of muons being accepted in the offline reconstruction. The numbers compile to a fake trigger rate of about 80%–90%. The figure displays the η distribution of Level-1 muon signal (pT > 10 GeV); and the subset of muon candidates coincident to an offline well reconstructed muon within ∆R < 0.2 (combined inner detector and muon spectrometer track with pT > 3 GeV); as well as offline reconstructed muons with pT > 10 GeV.

Fig. 2.6 Illustration of the fake trigger rate. Figure taken from [4]

In order to identify fake muons, hits of the inner station are used. It requires that the inner station track segment points to the IP, and match the middle station measurements. The NSW trigger will reduce fake triggers in the end-cap, as shown in Figure 2.7. As mentioned above, the fake triggers are introduced by low energetic particles produced between the SW and the EML. Real time trigger information from the NSW will be used to reject those fake triggers. In the ﬁgure, it compares the current contribution of the muon spectrometer to the Level-1

9 2.2 The New Small Wheel Upgrade Project

trigger with the new ones from the NSW. Tracks C and B are rejected, because the NSW does not ﬁnd a track coming from the IP that matches the Big Wheel candidate. While track A is accepted, it comes from the IP and is conﬁrmed by both the Big Wheel and the NSW. For the old trigger system, all three would have been accepted, since they have the same angle in the EML.

Fig. 2.7 Illustration of fake trigger segments information in the end-cap region of the muon spectrometer. Figure taken from [4]

2.2.2 Detector Technologies of the NSW

There are two New Small Wheels locate on both forward and backward region of the ATLAS detector. Each wheel has an arrangement of 8 large and 8 small pie-slice sectors, as shown in Figure 2.8a. Each sector consists of four wedges. The outer two are sTGC detectors, while the inner two are MM detectors. Each wedge comprises four single technology detection layers, grouped into quadruplets. The radial segmentation of the sTGC wedges consists of three quadruplets while the wedge of MM consists of two. The module names of the quadruplets from the center to the edge of the wheel for sTGC are S1, S2 and S3, while for MM are SM1 and SM2 in small sections. Same rule applies for the large sections as illustrated in Figure 2.8b. The MM LM2 and SM2 readout plane are segmented with three readout boards, while LM1 and SM1 have ﬁve.

10 New Small Wheel Project in Phase-I Upgrade of the ATLAS Experiment

Large Sector

L3 Small Sector

S3 L2 S2

L1 S1

(a) Schematic diagram of the small and large sTGC sectors. Drawing taken from CERN Draw- (b) Explosion drawing of a large sector. A sand- ing Directory wich conﬁguration of sTGC-MM-MM-sTGC is . applied [8]. Fig. 2.8 Construction of the NSW detector layers. small-strip Thin Gap Chambers

The sTGC is primarily devoted to the Level-1 trigger, as well as to provide precision tracking in the radial direction. For triggering, the sTGC detectors are required to identify each muon’s bunch crossing and to measure its trajectory with an angular resolution of less than 1 mrad for 1.3 < η < 2.7. For tracking, the chambers are required to have a position resolution | | better than 100 µm at impact angles up to 30°. To achieve these goals, the sTGC detectors are constructed in the following ways. Each layer of quadruplet consists of two cathode boards and a grid of wire groups between them. The wire grid is made of 50 µm diameter gold-plated tungsten wires held at a potential of 2.9 kV with a 1.8 mm pitch. The cathode boards are located at a distance of 1.4 mm from the wire plane, as shown on the left of Figure 2.9. The cathode boards are made of a graphite-epoxy composite material namely FR-4, it is a common material for printed circuit boards (PCBs). It has a typical surface resistivity of 100 or 200 kΩ m. On the one side of one cathode board · are copper pads used for fast trigger purposes, which determine the timing of the collision and group of strips to be used for trigger. While for the other cathode board, one of the sides are with copper strips, aligned perpendicular to the wires for precise position measurements. The strips have a 3.2 mm pitch, much smaller than the strip pitch of the TGC, hence it has the name "small-strip TGC". Each sTGC quadruplet consists of four pad-wire-strip planes, with alternative orientation as shown on the right of Figure 2.9.

11 2.2 The New Small Wheel Upgrade Project

Fig. 2.9 Construction of a single layer (left) [9] and a quadruplet (right) [10] of the sTGC detector .

MicroMegas Technology

The MicroMegas stands for "micro mesh gaseous detector". The MM detector is required to provide better than 100 µm for all particle incident angles in the NSW for precision tracking.

Cathode Mesh Pillars

Resistive strips

R/O strips

Fig. 2.10 Illustration of the working principle of the MM technology (left) and assembled MM quadruplet (right). A sketch of the orientation of the eta and stereo strips is shown [9].

The working principle of the MM technology is illustrated on the left of Figure 2.10. There is an anode with metallic strips with a pitch of a few hundreds micrometres. Special pillars are placed on the surface of the strip plane sustain a stretched thin metallic mesh at typically 100–150 µm distance from the anode, creating the amplification gap. The electric field in the amplification gap is held at a large value of 40–50 kV/cm. The gap of a few millimetres ∼ thickness between drift electrode and the mesh is acting conversion and drift Gap; its electric

ﬁeld is much lower at few hundred V/cm. A gas mixture of Ar:CO2 is ﬁlled in both gaps. Charged particles traversing the drift space ionize the gas. The electrons liberated by the

12 New Small Wheel Project in Phase-I Upgrade of the ATLAS Experiment ionization process drift towards the mesh. Due to the electric field in the Amplification Gap much stronger than in the Drift Gap, more than 95% of the electrons can drift to the mesh, and pass in the amplification gap, where the avalanche takes place, and finally the signal is collected by the readout strips. Contrary to the electrons, the ions that are produced in the avalanche process are moving back to the amplification mesh. The pitch of the strips is 450 (425) µm for the panels in the large (small) sectors. During assembly of the MM quadruplet, the anode readout boards are applied to both side of two stiffening readout panels with an aluminum honeycomb internal structure back to back. One of them is equipped with strips parallel to the bases of the trapezoid (eta strips) for the measurement of the precision coordinate, while the other one’s strips are tilted by 1.5°(stereo strips) for the measurement of the second coordinate (azimuthal). One central ± double sided drift panel and two external drift panels supporting the stainless steel mesh are coupled to the two readout panels to form the four gas gaps, where a gas mixture of Ar:CO2 with a ratio of 93:7 is filled.

2.3 Operating Environment and Construction of the Inves- tigated Elements

Environmental parameters of temperature and humidity in the ATLAS cavern during operation time of the LHC are obtianed from Detector Control Systems Data View, they are listed in Table 2.1. The time considered is from 1st of April, 2017 to 1st of December, 2017 and from April 1, 2018 to September 13, 2018.

Temperature mean [◦C] Min [◦C] Max [◦C] Top 25.11 23.75 26.55 Beam 24.12 22.55 24.95 Bottom 22.43 21.35 23.05 Barrel 23.01 21.45 23.45 Humidity mean [%] Min [%] Max [%] Top 32.31 17.5 36.5 Beam 34.44 17.5 39.5 Bottom 39.50 20.5 49.5 Barrel 34.92 17.5 43.5 Table 2.1 Environmental parameters of the ATLAS caverns during the operation time in year the 2017 and 2018.

13 2.3 Operating Environment and Construction of the Investigated Elements

The variation of the temperature between 22°to 24°and the relative humidity between 32% and 39 % is considered during the decision of humid conditions for the investigated detector elements, see section 4.1.

sTGC Strip Cathode Board S1 Module

The ﬁrst object in this humidity study is the sTGC strip cathode board S1 module. The cathode board consists of 1.2 mm thick FR-4 material with copper readout strips between FR-4 laminate (100-200 µm) prepreg and a whole copper plate as the ground plane, as illustrated in Figure 2.11. Later, a graphite mixture will be sprayed on the surface of prepreg. Internal support spacers with a thickness of 1.4 mm will be glued on both sides of the wire frame. Vacuum is applied on both sides of this spacer-wire frame-spacer planes during a single layer assembling. During quadruplet assembling, stiffening honeycomb frames are glued between layers, in precise statement, on the copper ground plane side of the cathode

boards with epoxy lacquer [11]. The chamber is ﬁlled with a gas mixture of 55% CO2 and 45% n-pentane.

Spacer

Prepreg

Fig. 2.11 Construction of the sTGC strip cathode board. Figure taken from [12] with modiﬁcation.

MM Readout Anode Boards with eta strips SE6, 7, 8 Modules

The construction of the readout anode board is shown in Figure 2.12. The resistive protection layer is a 50 µm Kapton foil with screen-printing resistive strips. It is glued under high pressure and temperature on top of the readout copper strips on FR4 material with a 25 µm

14 New Small Wheel Project in Phase-I Upgrade of the ATLAS Experiment thick layer of glue. On the top of the readout strips, a double layer of coverlay is photo- lithographed to form pillars. The steps of the readout board production can be found in the thesis [13].

Fig. 2.12 Construction of readout board of MicroMegas. Kapton foil with resistive strips is glued on a FR-4 PCB with copper strips. Figure taken from [12]

Each board can be divided into an active area, suitable for particle detection, and rim areas on the left and right side of each board and additionally on the top/bottom side on the SE8/SE6 board [14], as shown in Figure 2.13. The FR-4 material is the base of the board. 1022 copper readout strips of 300 µm width and a pitch of 425 µm cover only the active area. There are six interconnection holes located in the active area of the three boards with diameter 13 mm. Readout strips are routed around the holes. Interconnections are installed through the holes of all the panels during quadruplet assembly to limit the deformations of the panels when the detector is operated under gas overpressure [15]. The rim area is reserved for cooling channels with electronics and HV supply. Precision targets are marked in the rim area in an interval of around 100 mm for the alignment during panel assembly. A layer of Kapton foil with resistive strips follows the pattern of the readout strips cover the active area and around 30 - 50 mm width in the rim areas. During quadruplet assembly, mesh frame, O-ring, and gas gap frame with ﬁxation holes will take over the rim area.

MM Readout Panel with Eta Strips SM2 Module

MicroMegas readout anode boards are glued back to back on both sides of a 10 mm thick aluminum honeycomb web surrounded by a 10 mm thick and 30 mm wide aluminum frame, as shown in Figure 2.14. A vacuum is applied during the gluing process. Each side of the panel has three anode board segments: namely SE6, SE7 and SE8. The detail of how the

15 2.3 Operating Environment and Construction of the Investigated Elements

Fig. 2.13 Drawing of a MicroMegas anode PCB (left) and picture of the ﬁnalized board (right). The location of active and aim area as well as the interconnection holes are shown. Figure taken from [14].

readout anode boards are glued to the honeycomb frame can be found in [13].

Fig. 2.14 Construction of readout panel of MicroMegas. Two readout boards are glued back to back to a aluminum honeycomb frame. [13]

The panels are assembled vertically to quadruplets to reduce the effect of gravity. One readout board is assembled with two external drift boards on each side. Laser arm planarity measurements are done to check the ﬂatness of the readout and drift boards. A gas mixture

of Ar:CO2 is ﬁlled between the readout and drift panels.

16 Chapter 3

Experimental Setup

The goal of this experiment is to understand the detector modules’ behaviors in controlled environments with different humidity density. A humidification chamber is designed and built to create a relatively gas-tight space that can fit sample modules and provide sufficient support. A gas input system is designed and constructed to obtain user-controlled humidity density in the gas flow to the chamber. A reasonable way to precisely measure the deformation of the detector modules is to obtain the information of specific positions on the surface of the module boards. Therefore, several stainless steel spheres with aluminum bases are glued according to specific patterns on the surface of the boards, whose position can be measured by large scale mechanical Coordinate Measurement Machine. One can then use the values of the positions to reconstruct the 3D surface geometry of the board and further analysis can be done.

3.1 The Humidiﬁcation Chamber

To understand the board’s behaviors in the environment with different humidity, one hase to place it in a relatively gas-tight "box". The "box" should have dimensions suitable for all the modules that will be studied in the future. The three objects we planned to study are sTGC strip cathode board S1 module, MM readout panel with stereo strips SM2 module and MM readout boards with eta strips SE6, SE7 and SE8 module (the construction of the modules can be found in subsection 2.3). The dimensions of the "box" are decided according to the dimensions of the largest module, and the necessity that one can place in and take out the modules from the "box" easily by hands. Due to the large dimension of the "box", it also needs to have the possibility to be transported and to store some equipment for the experiment.

17 3.1 The Humidiﬁcation Chamber

adapter plate lid ventilator support 2 m frame

0.24 m humidification chamber

for gas input/output for Thermo- 1.6 m hygrometer

General Tolerances Form Tolerances Edge Dimensions Surface Scale: Quantit table DIN ISO DIN 7167 DIN 7168-m DIN 6784 - - 1302 - - Date Name Drawn 24.01.2019 hong Checked Standard

Physikalisches Institut Universität Freiburg Assembly Hermann-Herder-Str. 3 State Changes Date Name File Name: C:\Users\hong\Documents\Inventor files\Assembly.idw

Fig. 3.1 Technical design drawing of the humidiﬁcation chamber. The humidiﬁcation chamber is built in the form of a wagon with a lid along with it and a table underneath it. The dimensions of the chamber and the accessories are labeled.

According to the prerequisites mentioned above, a big wagon made of aluminum alloy plates and bars from the company Item is designed and built as shown in the Inventor drawing 3.1. The wagon has a humidification chamber and a table underneath. The humidification chamber has a dimension of 2080 1630 240 mm, and a lid with it. On each short side of the × × chamber, four holes with a diameter of 13 mm are placed equidistantly apart from each other for gas input or output. On each long side of the chamber, special-shaped holes are made for a thermo-hygrometer and electric wires. Four ventilators are installed in the four corners inside the humidification chamber. They are all installed facing clockwise with alternate heights, so that air inside the chamber can be well circulated. One long Item bar ( 2 m) ∼ with a width of 40 mm is assembled in the middle of the chamber to give primary support to the sample materials. Besides, six short Item bars ( 0.8 m) are assembled between the long ∼ bar and the construction bars of the chamber, with three on each side, for the same purpose. These seven bars constitute to support frame. The support frame prevents the contact of the sample materials with a large area of aluminum plates. They connect to construction bars of

18 Experimental Setup the chamber with adapter plates. There is about a 60 mm gap between the support frame and the bottom of the chamber to provide good air circulation under the sample materials. One can adjust the height of the support frame in the range of 20 mm. The support frame can be slide along the construction bars to adjust the distance between each other according to the size of the board that needs to be measured.

3.2 The Gas Input System

A gas input system with a user controlled humidity output is built. Nitrogen gas and pressurized air are accessible in the laboratory. Relatively inert nitrogen gas is used instead of pressurized air to reduce the damage of oil that may be contained in the pressurized air on the sample material. The schematic diagram of the setup is shown in ﬁgure 3.2.

Fig. 3.2 Schematic diagram of the gas input system.

The nitrogen gas source (datasheet see Appendix B) has around 3% relative humidity (RH). Then it splits into a wet and a dry path. Each path has a switch, a valve and a ﬂowmeter. One

19 3.3 The Thermo-Hygrometer can use the switch to completely let through or shut down the flow in the path and adjust the valve to achieve different flow in the particular path. The flowmeters are initially designed for ethane at 20 ◦C at 1 bar, and have a unit of liter / hour. However they are still applied since identical flowmeters for both paths are used. In the wet path, nitrogen gas goes through a bubbler. There is a certain amount of water inside the bubbler, that can add moisture to the gas flowing through it. The bubbler is also connected to a temperature control device from the company LAUDA. This equipment can keep the water inside the bubbler at a certain temperature with an accuracy of 1 C. The temperature of the LAUDA can be set higher ± ◦ than the room temperature, so that the water inside the bubbler could be heated up in order to release more moisture to the gas flowing through it. Later the two paths are merged and connect to the humidification chamber. The probe of the thermo-hygrometer is placed inside the chamber to collect real-time temperature and relative humidity data every 2 seconds. The details of the thermo-hygrometer will be discussed in the next section.

3.3 The Thermo-Hygrometer

The thermo-hygrometer is purchased from the company OMEGA [16], it is shown in figure 3.3. Model iTHX-W3 iServer MicroServer thermo-hygrometer monitors and records temperature, relative humidity and dew point over a 10/100BASE-T Ethernet LAN with a standard RJ45 connector directly connected to a PC. It sends data in standard TCP/IP packets. A simple web interface is used to present the current values delivered by the iServer. Then a network protocol analyzer Wireshark is used to capture live data, the data is exported to plain text and later offline analysis can be done. On the left in figure 3.3 is the main part of the thermo-hygrometer. The three LED lights that light up from top to bottom indicate 100 megabits per second data flow in the network, good network link and network activities and sensors are connected and can take readings. The temperature/humidity wand-shape probe is shown in the right. On the top side of this stainless steel "wand" are four hollow circles covered with wire mesh. The combination of a stainless steel cylinder shield and the wire mesh can protect the sensor from mechanical damage and also make sure that the sensor has good interaction with the environment. The specifications of the thermo-hygrometer taken from the device’s manual [17] are listed in table 3.1.

20 Experimental Setup

Sensor inside

Fig. 3.3 Main part of thermo-hygrometer (left) and the probe (right).

Table 3.1 Technical speciﬁcations of the thermo-hygrometer.

Relative Humidity (RH) Temperature (T) Accuracy at 10 - 90 % 2 % Accuracy at 5 - 45 °C 0.5 °C Hysteresis ± 1 % Response Time± 5 - 30 s Non-linearity ± 3 % Repeatability 0.1 % Response Time± 8 s Resolution± 0.1 °C Repeatability 0.1 % Resolution± 0.1 %

An example of the humid environment achieved in the humidiﬁcation chamber is presented in Figure 3.4.

The blue line in the plot indicates the relative humidity values over time inside the humidification chamber. The deviation in x in the plot is one hour; the RH value inside the humidification chamber trends to be stable around 2 hours, and it stays in a good stabilisation at the rest of the exposure time to the detector elements. The gas input system and the humidification chamber function well.

21 3.4 The Mechanical Coordinate Measurement Machine

Fig. 3.4 An example of the temperature and achieved RH inside the humidiﬁcation chamber.

3.4 The Mechanical Coordinate Measurement Machine

The mechanical Coordinate Measurement Machine is used to give precise information about positions in a large scale. The CMM is manufactured by the company "Wenzel" [18]. It is able to measure positions in three dimensions within micrometers range. The axes of the CMM are made of granite stones, to provide necessary mechanical stability. The electrical motor is used to power the movements of the axes with the support of air bearings. The CMM is located in a room with stabilized temperature and humidity This minimizes expansions of the granite as well as of the measured work pieces. The granite tables with a ﬂatness of less then 10 µm are used for the placement of the work pieces. An overview over the setup of the CMM is given in ﬁgure 3.5.

The precise measurements are achieved by a probe head manufactured by the company RENISHAW, which is able to rotate around the polar and the azimuthal axis. The probe tip is made of ruby with a diameter around 3 mm. A picture of the probe head with a tip is shown in figure 3.6. As mentioned at the beginning of this chapter, in order to observe specific points’ behaviors of the board, stainless reference spheres with aluminum bases are glued on the surface of the boards according to specific patterns. Later, a 3D surface geometry model of the board can be reconstructed from the position values of the center of the reference spheres measured by the CMM. The reference spheres have a diameter of a quarter inch. The dimension details and working principle of the measurement are illustrated in figure 3.7. The probe tip of the CMM touchs

22 Experimental Setup

Ventilation system

CMM arm Probe tip

Sample detector module

Fig. 3.5 Overview of CMM setup in the climate room.

Fig. 3.6 Probe head of the CMM with a probe tip. [19] the surface of the spheres six times. Two times are on the top of the spheres; while the positions of the rest four times are located equidistantly to adjacent ones on a circle on the upper part of the sphere. The cone formed by this circle and the center of the sphere has an angle of 120°. The center of the sphere is calculated by built-in program of the CMM from these six touches. With the knowledge of the shape of the workpiece, its parameters are reconstructed by ﬁtting the analytic parametrization of the shape to the measured points. The x, y and z values of each sphere’s center are listed in the output ﬁles. For convenience, the term position measurement is used for this obtainment process about positions of center of reference spheres. The term CRS is used for center of reference sphere in the following text.

The CMM is controlled by a software called “Metrosoft” [20]. It provides the possibility to create fully automated measurement programs after manually pre-programming and to deﬁne workpiece associated coordinate systems. In addition, it handles the calibration of the

23 3.5 Choice of Reference Spheres’ Positions and Measurement Coordinate System

∅3

120°

ä ∅6.35 P6,35

3.003 4 4.00 90°90°

General Tolerances Form Tolerances Edge Dimensions Surface Scale DIN ISO DIN 7167 DIN 7168-m DIN 6784 - 1302 - Date Name ∅6.006 Drawn 25.01.2019 hong P Checked Standard

ä Fig. 3.7 Illustration of the measurement principle. The upper half surface of the reference sphere is touched by the probe tip. The center of the sphere is reconstructed by CMM. probe tip and the data storage in a local database. The manual steering of the CMM via a remote control unit and the error handling are also possible.

3.5 Choice of Reference Spheres’ Positions and Measure- ment Coordinate System

There are two assumptions of possible deformations of sTGC cathode boards concluded from observation during the machining and transportation process. One is the board might elongate in its own plane. The second is a deformation might occur perpendicular to the board plane, and it might be in the shape of a hat. In order to study these two kinds of possible deformations, the shapes of the boards need to be reconstructed and the elongation of the boards in the directions of parallel and perpendicular to the strips need to be understood. Thus, the following rules for choosing the positions of the reference sphere are applied. The spheres and bases are aligned to certain lines 1) along the edges of the boards, 2) parallel or perpendicular to the strips, 3) on the diagonal lines of the boards; 4) the distance between two adjacent positions is better less than 200 mm for an efﬁcient data collection. The position of each reference sphere marked in number and the coordinate system of the measurement of the sTGC cathode board are shown in ﬁgure

24 Experimental Setup

3.8. The side with strip structure of the board is chosen, for directly measuring the strip misalignment.

X 339 340 341 ̥Z

334 338 ä 335 336 337

329 330 331 332 333

323 324 325 326 327 328

317 318 319 320 321 322

310 311 312 313 314 315 316

305 306 307 308 309 Y 300 301 302 303 304 (0, 0, 0) Fig. 3.8 Layout of the pattern of the reference spheres and schematic diagram of coordinate system of the measurement for sTGC strip cathode board.

The coordinate system of the measurement is a three dimensional Cartesian coordinate system. We usually apply the following rules to choose our coordinate system of the measurement: 1) the board plane as the xy-plane; 2) the long side of the board as the x-axis; 3) the middle point in one of the short edges of the board as the (0, 0, 0) point. The positive direction of the z-axis is defined towards the side where the reference spheres are glued. The CMM first measures the sphere 302, 300 and 340 (marked in red in figure 3.8) to set up the coordinate system; then measures the remaining spheres in a "S"-shaped routine from negative to positive y and in the direction of positive x. Layout of positions of reference spheres and the coordinate system of SM2 readout panel and readout board SE6, SE7 and SE8 are presented in figure 3.9 and 3.10 respectively. Considering the delicate high-cost manufacturing process of the MicroMegas readout panel, only 6 reference spheres and bases are glued on the surface of the readout board with strips

25 3.5 Choice of Reference Spheres’ Positions and Measurement Coordinate System structure besides on the PCB located on the top of the aluminum frame. These six speciﬁc positions are at the markers of the interconnection holes (see ﬁgure 2.14). Later holes will be drilled in these position during assembly of the quadruplets, so that no damage causing from the glue and mechanical press is done to the readout board surface. The choice of the reference spheres’ positions and the coordinate system for MM readout boards SE6, 7 and 8 follows the rules mentioned above. Around 27 to 29 reference spheres are glued on each readout board for a better interpretation.

X ̥Z 414419 415 420 416

410 411 412 413

409

406 407 405 408 404

Y 401 417402 418 403 (0, 0, 0) Fig. 3.9 Layout of positions of the reference spheres and schematic diagram of coordinate system of the measurement for SM2 module. Ä

26 Experimental Setup

̥Z 5122 5123 5124 5125 5126 5127 5128

5119 5120 5121 5112 5113 5114 5115 5116 5117 5118 5110 5111 5107 5108 5109 Y 5100 5101 5102(0, 0, 0) 5103 5104 5105 5106 X 5222 5223 5224 5225 5226 5227 5228

5219 5220 5221

5212 5213 5214 5215 5216 5217 5218 5210 5211 Y 5207 5208 5209 5200 5201 5202(0, 0, 0) 5203 5204 5205 5206 X 5320 5321 5322 5323 5324 5325 5326 5319 5317 5318

5310 5311 5312 5313 5314 5315 5316 5307 5308 5309

Y 5300 5301 5302 (0, 0, 0) 5303 5304 5305 5306

Fig. 3.10 From the top to bottom are the layouts of positions of the reference spheres and schematic diagrams of coordinate system of the measurement for MM SE6, SE7 and SE8 modules.

Chapter 4

Deformations of Production Line Detector Elements

The experiment aims to determine the shapes and dimensions of the deformations on the FR-4 based multi-layer materials detector modules which are used in NSW by exposing them in an environment with high humidity. sTGC strip cathode board S1 module, MM readout panel with stereo strips SM2 module and MM readout anode boards with eta strips SE6, SE7, SE8 modules are studied in two different humid conditions and one air drying process separately. The procedure and the choice of the humid conditions are described in the ﬁrst section 4.1. The results are discussed in the following sections. The deformation in z-axis and the elongation in xy-plane are presented separately. A series of analysis is done to evaluate the values of the maximum deformation in the humid environment and residual deformation after the air drying process in the climate room.

4.1 Introduction of the Experiment

The procedure of the experiment is divided into two steps. The first step is to expose the detector elements to an environment with controlled relative humidity (RH) for a certain time in the humidification chamber. The next step is to perform the position measurement (see section 3.5) to the modules at the CMM. The modules are placed against three reference aluminum plates which fixing the position of three out of four edges of the module on the granite table, to ensure the modules have the same position for each measurement. After the measurement, the modules are transported back to the humidification chamber for the next step humidity study.

29 4.2 Results of sTGC Strip Cathode Board S1 Module

There are three different humidity conditions in this study: 65%, ⩾90%, and relative dry environment with 55% RH, all in room temperature. The decision of the three conditions is described as follows. First the temperature and RH of the ATLAS cavern listed in section 2.3 is taken into consideration. Because of laboratory conditions and climate restrictions, one could not control the temperature factor. The reason 65%RH is chosen to be the first condition is that, it is slightly higher than the ambient RH. The modules sometimes can encounter such environment, for instance, during the transportation on some rainy days. Secondly, one generated an environment with an extreme RH value: 90% or higher in order to push the limit of the maximum deformations that could possibly happen. At last, the modules are placed on the granite table in the climate room. The climate room has a stable environment that is relatively dry and close to the regular contact of the module: 55% RH and 22 °C. During each condition period, one regularly takes the modules out and perform the position measurement to monitor the change of the deformations, in order to determine the optimal rate of the measurement and the length of the time for each condition. A 3D surface geometry model of the module, generated from x, y, z values of the CRSs (see section 3.4), is used to show the result in the z-axis, while a two-dimensional plot with arrows according to the length and direction of the elongation on each CRS is used to show the result in xy-plane. Systematic uncertainties of the measurements of the coordinates along z-axis and in xy-plane are also given respectively. A set of comparative measurements was done either in the beginning or at the end of all measurements to define systematic uncertainties with the same procedure and transportation methods as the actual measurements. To do so instead of doing two comparative measurements immediately one after another without moving the modules, is to take into account of mechanical disturbing during the transportation and uncertainty of manual placement of the modules. Before the three conditions are performed, a reference measurement is done; the subsequent plots compare a particular measurement with this reference measurement. Coefficient of linear humid elongation (CLHE) is introduced for analysis of evaluation of the maximum and residual deformation of the modules.

4.2 Results of sTGC Strip Cathode Board S1 Module

Trapezoid-shaped sTGC strip cathode board S1 module has a thickness of 1.3 mm. The dimensions and construction of the module can be found in section 2.3. Table 4.1 lists the dates and and environment conditions of the measurements. Phase ① ② ③ are used to name the three conditions for a convenience reason.

30 Deformations of Production Line Detector Elements

Table 4.1 Measurements of sTGC Strip Cathode Board S1 Module

Environment Date Duration Condition Climate Room Reference Measurement Oct. 23, 2018 ~ 55% RH 22 °C with plastic wrapper Oct. 23, 2018 - Humid Phase ① 12 days ~ 65% RH 23 °C Nov. 2, 2018 Environment Nov. 2, 2018 - Phase ② 10 days ~ 90% RH 23 °C Nov. 14, 2018 Dry Nov. 14, 2018 - ~ 2.5 Climate Room Phase ③ Environment Feb. 2, 2019 months ~ 55% RH 22 °C

Deformation in z-axis

First, the systematic uncertainty of the measurement in z-axis in the range of the sTGC strip cathode board S1 module is determined. Between the two comparative measurements, the module was place inside the humidification chamber with closed lid for 20 hours at room temperature and RH. This is to imitate the routines of actual measurements. The result is presented in Figure 4.1 as a 3D surface geometry model. The perspective of the plot is looking down from above the module. The z-axis is z values of each CRS of the second comparative measurement subtracted the first one, while x and y values of the first measurement are used. The color scale is attached on the right side. The red color indicates that the module is deformed in the positive direction of the z-axis; in contrast, the purple color indicates the negative direction. The maximum and minimum values and the difference between the two are shown in the legend on the upper left corner. The difference is defined as

∆Z Zmax Zmin. It has a value less than 0.1 mm. A unique serial number generated based ≡ − on dates, times, and numbers of the two involved measurements is marked in the bottom of each plot, for tracking the information. The ﬁgure on the right side gives the information of the mean value and standard deviation of z values. The absolute mean is taken as the systematic uncertainty of the measurement in z-axis in the range of sTGC S1 strip cathode board:

σz_S1 = Z = 27µm (4.1) The results in z-axis of Phase ① and ② are shown in Figure 4.2. The z-axis is the z values of each CRS from the last measurement in the particular phase subtracted the reference measurement, while x and y values of the reference measurement are used. After the module is immersed in an environment of 65% RH and 23 °C for 12 days, a convex deformation is

31 4.2 Results of sTGC Strip Cathode Board S1 Module

Z max = 0.058 mm Subtracted in Z-axis Z min = -0.019 mm

X (mm) Z ∆ Z = 0.077 mm 3 Entries 42 1200 Mean 0.02706 0.05 Z (mm) Std Dev 0.01898

1000 0.04

800 0.03 2

0.02 600

0.01 400 1

0 200 −0.01

0 0 300 200 100 0 −100 −200 −300 0 0.02 0.04 0.06 0.08 0.1 20181023111701:21 - 20181022150519:20 Z (mm) Y (mm) Fig. 4.1 Systematic uncertainty of the measurement in z-axis in the range of S1 module of sTGC strip cathode board. A 3D surface geometry model with an overhead view is presented and the mean value of z is determined.

observed as shown in Figure 4.2a. The plot indicates an arched convexity in z-axis on the upper part of the board with a height of

∆ZP1 = 0.7mm (4.2)

Figure 4.2b is the result after the board is immersed in 90% RH and 23 °C environment for 10 days. The arched convexity moves to the lower part of the module with a larger height:

∆ZP2 = 3.9mm (4.3)

The convexity with a height of almost 4 mm can be observed with the naked eye. That makes the systematic uncertainty trivial, thus it is not shown. Through the description of the construction of the board in section 2.3 and physical properties of FR-4 material, a possible cause is that, the rate of moisture absorption of copper is less than the FR-4 material. On the back side of the board (the side facing the granite table) is a whole piece of copper plane, while the upper side (the perspective of the ﬁgure) are copper strips covered by a thin layer of FR-4 prepreg (see Figure 2.11). That makes the back side of the board has less strain to deform than the upper one, a upper arched convexity is therefore occurred.

32 Deformations of Production Line Detector Elements

Subtracted in Z-axis Subtracted in Z-axis Z max = 0.554 mm Z max = 3.056 mm Z min = -0.119 mm Z min = -0.875 mm X (mm) X (mm) 3 Δ Z = 0.674 mm Δ Z = 3.931 mm 1200 0.5 1200 Z (mm) Z (mm) 2.5

1000 0.4 1000 2

800 800 0.3 1.5

600 600 1 0.2

0.5 400 400 0.1

0 200 200 0 −0.5 0 0 300 200 100 0 −100 −200 −300 300 200 100 0 −100 −200 −300 20181102101059:39 - 20181023111701:21 20181114132624:55 - 20181023111701:21 Y (mm) Y (mm) (a) Deformation in z-axis at the end of Phase ①. (b) Deformation in z-axis at the end of Phase ②.

Fig. 4.2 Deformation of S1 module in z-axis in a humid environment. A arched convex deformation in the middle of the board is observed. The convexity moves in a higher RH environment.

The results of Phase ③ in z-axis are shown in Figure 4.3. The ﬁgure on the left is the result of drying the module for 4.5 hours. Despite the relatively short drying time, ∆Z is reduced by around 0.6 mm, with ∆ZP3.1 = 3.4mm (4.4) here the superscript "P3.1" means the ﬁrst result shown here in Phase ③. The plot on the right shows the result after 8 days. It is quite apparent that the arched convex deformation moves from the lower back to the upper half of the module and ∆Z is reduced to less than 1 mm: ∆ZP3.2 = 0.9mm (4.5)

A plot of ∆Z values over time is shown as black dots in the Figure 4.4. The data come from the 8 measurements were done regularly during the first 8 days in Phase ③. Looking at the trend of the data points, the fit function is determined as a transcendental natural exponential function, which is commonly used in many growth or decay processes. The form of the p p x exponential function is chosen to be f (x) = e 0 1 + p2, (p0 1 2 R ) according to the − , , ∈ + decreasing trend and offsets in x- and y-axis. The fit result is shown as the red curve in the plot. The uncertainty in x-axis is asymmetric with only in the direction of lower x-axis; it is determined from the time duration of the position measurement. For S1 module, it is around

33 4.2 Results of sTGC Strip Cathode Board S1 Module

Subtracted in Z-axis Subtracted in Z-axis Z max = 2.647 mm Z max = 0.628 mm Z min = -0.715 mm X (mm) Z min = -0.271 mm Δ Z = 3.362 mm X (mm) 2.5 Δ Z = 0.900 mm 0.6 1200 1200 Z (mm) Z (mm) 0.5 2 1000 1000 0.4 1.5 800 800 0.3

1 0.2 600 600

0.1 0.5 400 400 0 0 200 200 −0.1

−0.5 0 0 −0.2 300 200 100 0 −100 −200 −300 300 200 100 0 −100 −200 −300 20181114175506:60 - 20181023111701:21 20181122101246:74 - 20181023111701:21 Y (mm) Y (mm) (a) Deformation in z-axis after air drying for 4.5 (b) Deformation in z-axis after air drying for 8 hours. days.

Fig. 4.3 Result of z-axis in a relative dry environment. The arched convex deformation gets lower and moves back along the time of drying.

0.5 hour. The uncertainty in y-axis comes from the systematic uncertainty (see Equation 4.1). The asymptote value of this exponential function is (0.92 0.03)mm, which is much larger ± than the systematic uncertainty. It can be considered as the residual deformation of board after exposure in a extreme humid environment. A measurement is done after 2.5 months air-drying process in the climate room, it will be discussed later.

Elongation in xy-plane

Before looking at the results in xy-plane, one should first contemplate whether the convex deformation in z-axis would affect the results in xy-plane. In the schematic sketch Figure 4.5, one can see that the arched convex deformation in z-axis does have a direct impact on the result in xy-plane. One assumes that the module is relatively flat for the first measurement.

The distance from CRS to (0, 0, 0) point projected on y-axis is measured and labeled as y1 in the ﬁgure. This is the actual vertical distance from the CRS to the x-axis. y2 is measured in the second measurement when the board has an arched convex deformation. The height from CRS to the bottom of the base (h) make one falsely believe that, y2 is the new vertical distance from the CRS to the x-axis. However, the length of the curve AB is the actual new ˜ distance should be taken into account. In order to obtain the length information of AB, some ˜

34 Deformations of Production Line Detector Elements

∆ Z ~ t χ2 / ndf 19.51 / 5 3.5 p0 0.9726 ± 0.01641 p1 0.0253 ± 0.001154 3 p2 0.9224 ± 0.02949 Z (mm) ∆ 2.5

1.5

0.5

0 0 50 100 150 200 250 300 time (hour) Fig. 4.4 ∆Z over time in the first 8 days in Phase ③ with a fit of a natural exponential function. weights are placed on the module avoiding the reference spheres, as shown in Figure 4.6. Available weights in the lab are four 6.3 kg bar-shaped iron weights, several 500 g and 200 g round-shaped brass weights with V-shaped notch. The weights are placed from heavier to lighter, one by one after each other diagonally from the corner marked as "P" in the figure. If one does not start from the corner "P", where the two sides against the reference aluminum plates and blocks intersect, the deformed module could not spread freely on the table, and this reduces the elongation value in xy-plane.

h A

90° 2nd measurement

4 y2

4 P6

B B 5 y1 h 90° ̥X (0, 0, 0) 1st measurement Y board surface

Fig. 4.5 Schematic sketch of the effect of convex deformation in z-axis on the measurement result in xy-plane.

In this case, two measurements were performed each time. One without weights, the output will be used for analyzing the deformation in z-axis; once with for the xy-plane. The results in xy-plane is illustrated in a 2D plot with vectors corresponding to the direction and length

ä 4.2 Results of sTGC Strip Cathode Board S1 Module

Fig. 4.6 Weights are placed during the measurements used to obtain information in xy-plane. of the elongation. Same, the systematic uncertainty of the measurement in the xy-plane is determined first, the result is shown in Figure 4.7. The orientation of the coordinate system is rotated 90 degrees clockwise with respect to the previous figures. The centre point is defined as CRS No. 320 (see Figure 3.8) considering it is roughly the center of gravity. It is marked as O′ in figure, as well as the new coordinate system X’Y’. The centre vector −→O′ is defined as displacement of centre point between the two comparative measurements:

m2 m1 m2 m1 −→O′S1 (x x , y y ) (4.6) ≡ 320 − 320 320 − 320 m1 and m2 refers to the first and second measurement of the two comparative measurement. m1 m1 The black points are CRSs at the first measurement: (xn , yn ), with n = 300-341 (see Figure 3.8). The red arrows are elongation vectors −→Dn with a scale factor C, so that they can be visible in this scale of coordinate system. They are defined as pointing from the CRSs of the first to second measurement but subtracted by the centre vector:

m2 m1 m2 m1 C(−→Dn) CÄ(x x , y y ) −→O′ä (4.7) ≡ n − n n − n − this is in order to give a clear and direct vision of how the board expands outwards. This rule applies not only to the systematic uncertainty measurement but also to all the measurement that will be presented later. The red arrow in the legend corresponds to a certain length, so

36 Deformations of Production Line Detector Elements that one can easily compare the length of the arrows in the plot with it.

Scale factor= 12000 Reference measurement l Length corresponding to 10 µm 3 Entries 42 Mean 3.232 300 Y′ Std Dev 2.038 Y (mm)

200

100 2

0 O′ X′

−100 1

−200

−300

0 200 400 600 800 1000 1200 0 X (mm) 0 2 4 6 8 10 20181023111701:21 - 20181022150519:20 20181023111701:21 - 20181022150519:20 l (µm) Fig. 4.7 Schematic diagram of systematic uncertainty of the measurement in xy-plane in the range of sTGC strip cathode board S1 module. Arrows correspond to the length and direction of the displacement of each CRS between the two comparative measurements. The mean value is determined.

2 The length of the elongation vector, denoted as l = (−→Dn) , describes the displacement of each CRS between the two comparative measurements.q The mean value of l is takne as the systematic uncertainty of the measurement in xy-plane in the range of sTGC strip cathode board S1 module:

σxy_S1 = l = 3µm (4.8) which is satisfactory for the xy-plane measurement.

Figure 4.8 presents the elongation in the humid environment of Phase ① and ②. Figure 4.8a shows the result after 12 days in 65% RH and 23 °C environment. Here, the elongation m vectors −→Dn compare a certain measurement to the reference measurement, which means m2 = 0: m m 0 m 0 −→D (x x , y y ) −→O′ (4.9) n ≡ n − n n − n − The red arrows in the ﬁgure have a scale factor of 12000. There is an obvious displacement happened to the CRSs, but there is no clear pattern. Whereas one can clearly see an outwards expanding pattern in Figure 4.8b. The largest displacement is at No. 341 CRS:

P2 P2 l = D−−→ max = (37 3)µm (4.10) max | 341| ± 37 4.2 Results of sTGC Strip Cathode Board S1 Module

Scale factor= 12000 Scale factor= 5000 Reference measurement Reference measurement Length corresponding to 10 µm Length corresponding to 20 µm

300 300 Y (mm) Y (mm)

200 200

100 100

0 0

−100 −100

−200 −200

−300 −300

0 200 400 600 800 1000 1200 0 200 400 600 800 1000 1200 X (mm) X (mm) 20181102104752:40 - 20181023114628:22 20181114135828:56 - 20181023114628:22 (a) Elongation in xy-plane at the end of Phase ①. (b) Elongation in xy-plane at the end of Phase ②.

Fig. 4.8 Schematic diagram of the elongation in xy-plane in the humid environment. One can see a clear outwards elongation pattern at the end of Phase ②.

This elongation gradually increases from the centre point to the edges of the board. In order to determine if the length of the elongation vector (l) is proportional to the distance to the centre point (d), a plot of l over d is made, as shown in Figure 4.9. d in mathematics form is:

0 0 2 0 0 2 d = (xn x ) + (yn y ) (4.11) − O′ − O′ q The data points of l over d at the end of Phase ② are in a linear distribution. That means the elongation of the strips are homogeneous in the board plane. To continue and complete this thought, one deﬁnes coefﬁcient of humid elongation as:

l ϵ = (4.12) d it is dimensionless, but for a better interpretation, it is in an order of µm/m. This coefﬁcient here describes how the dimensions of the module changes with a change in humidity. From section 2.3, one knows the strips are aligned parallel to the y-axis in our coordinate system. The change of the strip pith of sTGC cathode board has a directly impact on performance of trigger precision. Hence, the length of the elongation in x-axis is more interesting for later detector performance analysis. Coefﬁcient of linear humid elongation (CLHE) is introduced to describe uniaxial length of elongation over the vertical distance to the centre point with

38 Deformations of Production Line Detector Elements

l ~ d

0.04 l (mm) 0.035

0.03

0.025

0.02

0.015

0.01

0.005

0 0 100 200 300 400 500 600 700 800 d (mm)

20181114135828:56 - 20181023114628:22 Fig. 4.9 The data points of l over d at the end of Phase ② are in a linear distribution. the form as: lx ly ϵx = , ϵy = , (4.13) dx dy

One could draw ϵx and ϵy achieve from linear fit over time and fit the data with natural exponential function with a form of f (x) = ep0 p1x + p2, (p0, p1, p2 R ) separately, for − − ∈ + estimate the maximal elongation in humid environment. The uncertainty of time combines 2.5 0.5 hours for the gas in the humidification chamber to reach a stable RH value (see ± section 3.3), and 0.5 hour of the position measurements at the CMM. The uncertainty of CLHE is achieved from the respect linear fit. However, due to insufficient time of the exposure in a humid environment, the data obtained could not be fitted. The evaluation by the fit could not be reached.

The values of ϵx and ϵy achieved from linear ﬁt of each measurement beside with the ∆Z in Phase ② are listed in the Table 4.2.

Time (hour) 46 74 94 234 257 279 ϵx (µm/m) 25 22 25 38 35 37 ϵy (µm/m) 34 41 40 50 48 48 ∆Z (mm) 3.0 2.9 3.2 4.4 4.0 3.9 Table 4.2 The value of the coefﬁcient of linear humid elongation parallel to x- and y-axis and ∆Z of each measurement in Phase ② over the time.

39 4.2 Results of sTGC Strip Cathode Board S1 Module

The rate of moisture absorption of FR-4 grade PCB can be found in Appendix A, it indicates the absorption of the moisture of the FR-4 PCBs with a thickness in a millimeter range is a relatively slow process. It is possible that the data achieved in the 10 days with a certain value of uncertainty are not precise enough to be ﬁtted. At this stage, the maximal value of CLHE in the direction of strip pitch of S1 module during 10 days exposed in an environment of ~ 90% RH 23 °C is 38µm/m.

Then, the results of Phase ③ in xy-plane are shown in Figure 4.10. They all have the same scale factor of 5000. The two plots are the elongation of the board being air dried for 4.5 hours (Phase 3.1) and 8 days (Phase 3.2) respectively. The largest displacement is reduced to

lP3.1 =(32 3)µm (4.14) max ± and lP3.2 =(24 3)µm (4.15) max ± It is evidently the elongation is shrunken. The moisture absorbed by the board is evaporating over time.

Scale factor= 5000 Scale factor= 5000 Reference measurement Reference measurement Length corresponding to 20 µm Length corresponding to 20 µm

300 300 X (mm) Y (mm)

200 200

100 100

0 0

−100 −100

−200 −200

−300 −300

0 200 400 600 800 1000 1200 0 200 400 600 800 1000 1200 Y (mm) X (mm) 20181114182604:61 - 20181023114628:22 20181122105032:75 - 20181023114628:22 (a) Elongation in xy-plane after air drying for 4.5 (b) Elongation in xy-plane after air drying for 8 hours. days.

Fig. 4.10 Schematic diagram of the residual elongation in xy-plane of the board in the air drying process in the climate room. The outwards elongation shrink over time.

The residual elongation of the board is attempted to determine as follow. The board is placed on the granite table for around 2.5 months. The result is shown in Figure 4.11. From the ﬁgure 4.11a of the result in z-axis , one could not see the arched convex deformation anymore;

40 Deformations of Production Line Detector Elements also the clear outwards elongation in the xy-plane disappeared. However, ∆Z is even larger than the result after 8 days; it is up to around 1.7 mm, and there are inward vectors on both short sides of the board. Mechanical issues may cause this unexpected phenomenon. Although the module was placed on the granite table most of the time, but it was also carried away due to the imitated available space on the table. Besides, some distance must be kept between the weights and reference spheres, so that the tip of the CMM has enough space to operate the position measurement. Apparently, even though there were weights around these reference spheres during the position measurement for xy-plane, it is not efﬁcient enough to balance out the plastic deformation on these two sides, where were hold by hands when carrying the board without caution.

Subtracted in Z-axis Scale factor= 5000 Z max = 0.497 mm Z min = -1.213 mm Measurement 0

X (mm) Δ Z = 1.710 mm length corresponding to 20 µm 1200 300

0.2 Z (mm) Y (mm)

1000 0 200

100 800 −0.2

−0.4 0 600

−0.6 −100 400 −0.8 −200

200 −1 −300

0 200 400 600 800 1000 1200 0 X (mm) 300 200 100 0 −100 −200 −300 20190201111257:76 - 20181023111701:21

Y (mm) 20190201114603:77 - 20181023114628:22 (a) Residual deformation in z-axis after air drying (b) Residual elongation in xy-plane after air drying for 2.5 months. for 2.5 months.

Fig. 4.11 Schematic diagram of the residual deformation in z-axis and xy-plane after the S1 module being stored in the climate for 2.5 months. The arched convexity and outward elongation disappeared. However, there are unexpected large ∆Z and inward vectors.

One excludes the eight data points (five and three data points from the longer and shorter parallel sides of the trapezoid-shaped board) which have inwards elongation and analyzes the remaining. ∆Z gets less with a value of around 1.3 mm. However, it is still larger than the asymptote value of the exponential fit function for the first eight days in the air drying process (see Figure 4.4). As for xy-plane, Figure 4.12 is used to determine the mean of l excluding the 8 data points mentioned above after 2.5 months air drying process. The maximum and mean value of the

41 4.2 Results of sTGC Strip Cathode Board S1 Module

length of the residual elongation vectors are:

P3.3 p3.3 l′ = (20 3)µm and l = (5 3)µm (4.16) max ± ′ ±

l 5 Entries 34 Mean 5.812 Std Dev 3.702

0 0 5 10 15 20 25

20190201114603:77 - 20181023114628:22 l (µm)

Fig. 4.12 The length of the elongation vector excluding the eight data points which have inwards elongation.

In Figure 4.11b, there is one elongation vector (at No. 333 CRS, see Figure 3.8) much larger than the rest. This may be due to the instability of the reference spheres caused by the aging of the glue from extremely high humidity environment, or mechanical disturbing from the repeated transportation process. This large value increases the mean value of the l. After all, the mean value is at the same order of magnitude with the systematic uncertainty of the measurement in xy-plane.

Conclusion

As a result, the arched convex deformation disappeared, but the deformation from mechanical disturbing remained in z-axis of the board. However, as mentioned in section 2.3, for the upper side of the board, a graphite mixture will be sprayed on the surface of the prepreg, and the vacuum is applied between the prepreg and the spacer-wire frame-spacer plane. For the bottom side, glue is applied on the copper ground plane to a stiffening honeycomb frame during quadruplet assembly. Deformation in z-axis can be extinguished by the application of the vacuum and gluing during the machining process of the module. As for xy-plane, the mean value (7µm) of the length of the residual elongation is at the same

42 Deformations of Production Line Detector Elements order of magnitude with the systematic uncertainty of the measurement in xy-plane (see Equation 4.8). Considering of the knowledge of the machining process of the module with application of vacuum and gluing, one could state that the elongation in xy-plane disappeared after 2.5 months stored in an ambient environment.

4.3 Results of MM Readout Panel with Stereo Strips SM2 Module

The construction and operating environment can be found in section 2.3. The dates and environment conditions of the measurements that were done for MM readout panel with stereo strips SM2 module are listed in Table 4.3 lists. A designed Phase ① environment with 65% RH and 23 °C was failed to maintain for five days. However the environment in the humidification chamber was alike in the climate room with 55% RH and 23 °C. The impact of the environment on the board during these five days can be neglected. In the air drying process of Phase ③, there were technical problems of the ventilation system in the climate room, temperature and RH were not well stabilized. Instead, the environment has in average ambient RH and room temperate of around 40% RH and 23 °C.

Table 4.3 Measurements of MM readout panel with stereo strips SM2 module

Environment Date Duration Condition Climate Room Reference Measurement Jan. 11, 2019 ~ 55% RH 22 °C Jan. 11, 2019 - 5 days ~ 55% RH 23 °C Humid Jan. 16, 2019 Environment Jan. 16, 2019 - Phase ① 15 days ~ 65% RH 23 °C Jan. 31, 2019 Jan. 31, 2019 - Phase ② 40 days ~ 90% RH 23 °C Mar. 12, 2019 Dry Mar. 12, 2019 - Phase ③ ~ 2 months Climate Room Environment May. 20, 2019

43 4.3 Results of MM Readout Panel with Stereo Strips SM2 Module

Deformation in z-axis

A set of comparative measurements for systematic uncertainty are done almost in the end of all measurement, imitating the actual routine of the transportation method. Between the two comparative measurements, the panel was placed inside the humidiﬁcation chamber for around 4 hours. The same kind of 3D surface geometry model of the panel is presented in Figure 4.13. The mean value of absolute Z is also taken as the systematic uncertainty of the measurement in z-axis in the range of MM readout panel SM2 model. ∆Z describes the total variation between the surface geometry models of the two comparative measurements, it is also given:

∆Z = 221µm, σz_SM2 = Z = 30µm (4.17)

Subtracted in Z-axis Z max = 0.068 mm Z min = -0.153 mm Z ∆ Z = 0.221 mm 5 Entries 20

X (mm) Mean 0.02906 0.06 Std Dev 0.03431

1200 0.04 Z (mm) 4 0.02 1000 0 800 −0.02 3 −0.04 600 − 0.06 2 400 −0.08 −0.1 200 1 −0.12 0 −0.14 − − − − 800 600 400 200 0 200 400 600 800 0 0 0.05 0.1 0.15 0.2 Y (mm) 20190402144126:42 - 20190402101506:40 Z (mm)

Fig. 4.13 Systematic uncertainty of the measurement in z-axis in the range of the MM readout panel with stereo strips SM2 model. 3D surface geometry model of the panel looking from positive to negative z-axis direction.

Next, the deformation in z-axis of Phase ① and ② are shown in Figure 4.14. Within the systematic uncertainty, no obvious deformation in z-axis was observed during the whole 55 days in the humid environment. ∆Z and the mean values of Z in Phase ① and ② are presented in Equation 4.18 and 4.19 with superscripts P1 and P2 respectively:

∆ZP1 = 136µm, ZP1 = 36µm (4.18)

∆ZP2 = 207µm, ZP2 = 39µm (4.19)

Compare to Equation 4.17; one can see that ∆Z and mean values of Z are at the same order of magnitude with the systematic uncertainty. This behavior is expected, as mention in

44 Deformations of Production Line Detector Elements

Subtracted in Z-axis Subtracted in Z-axis Z max = 0.062 mm Z max = 0.080 mm Z min = -0.074 mm Z min = -0.127 mm Δ Z = 0.136 mm Δ Z = 0.207 mm X (mm) 0.06 X (mm) 0.06 1200 Z (mm)

1200 Z (mm) 0.04 0.04

1000 1000 0.02 0.02 0 800 800 0 −0.02 600 600 0.04 −0.02 − 400 400 −0.06 −0.04 −0.08 200 200 −0.06 −0.1 0 0 −0.12 800 600 400 200 0 −200 −400 −600 −800 800 600 400 200 0 −200 −400 −600 −800 Y (mm) Y (mm) 20190131144617:12 - 2019011190803:6 20190312140938:21 - 2019011190803:6 (a) Deformation in z-axis at the end of Phase ①. (b) Deformation in z-axis at the end of Phase ②.

Fig. 4.14 Deformations in z-axis in a humid environment. No obvious deformation in z-axis was observed within the order of magnitude systematic uncertainty. section 2.3, the vacuum is applied during the gluing process between the FR-4 board and the stiffening aluminum honeycomb frame. As a metal, aluminum has less strain to deform, it stiffs the FR-4 board which tightly glued on it. This causes the deformation of the FR-4 board not free anymore, decreases the strain value of it.

Then, the results of Phase ③ in z-axis are shown in Figure 4.15. No matter the module is dried for 5 hours or around two months, ∆Z and the mean value of Z are still at the same order of magnitude with the systematic uncertainty of the measurement in z-axis. The values are presented as follow:

∆ZP3.1 = 283µm, ZP3.1 = 38µm (4.20)

∆ZP3.2 = 193µm, ZP3.2 = 30µm (4.21)

Although the mean value of Z after the panel being exposed in 90% RH 23 °C environment for 40 days (39µm) is slightly higher than the systematic uncertainty value (30µm), but they are at the same order of magnitude. At this point of view, one could still concluded that the way MM readout panels are machined can totally handle the deformation in z-axis caused by high humidity density.

45 4.3 Results of MM Readout Panel with Stereo Strips SM2 Module

Subtracted in Z-axis Subtracted in Z-axis Z max = 0.146 mm Z max = 0.113 mm Z min = -0.137 mm Z min = -0.080 mm Δ Z = 0.283 mm Δ Z = 0.193 mm X (mm) X (mm) 0.1 1200 Z (mm) 1200 0.1 Z (mm) 0.08

1000 1000 0.06 0.05 0.04 800 800 0.02 0 600 600 0

400 −0.05 400 −0.02

−0.04 200 200 0.1 − −0.06 0 0 800 600 400 200 0 −200 −400 −600 −800 800 600 400 200 0 −200 −400 −600 −800 Y (mm) Y (mm) 20190312190522:22 - 2019011190803:6 20190520134042:49 - 2019011190803:6 (a) Deformation in z-axis after air drying for 5 (b) Deformation in z-axis after air drying for 2 hours. months.

Fig. 4.15 Deformation in z-axis in the air drying process in the climate room. Still no obvious deformation was observed.

Elongation in xy-plane

Unlike sTGC cathode board, since MM panel does not deform in z-axis, there is no need to do a measurement correction for xy-plane. Each time the same measurement is used for data analysis in both z-axis and xy-plane. First the systematic uncertainty of the measurement in xy-plane is determined. The same kind of 2D plot as for sTGC cathode board is shown in Figure 4.16. The middle point of CRS No. 404 and 409 (see Figure 3.9) is defined as the centre point of the panel, again considering it is roughly the center of gravity of the panel. It is marked as O′ in the figure. So that the centre vector −→O′ in the range of the SM2 module is defined as the average of the displacement of CRS No. 404 and 409 between the two comparative measurements:

m2 m1 m2 m1 m2 m1 m2 m1 x404 x404 + x409 x409 y404 y404 + y409 y409 −→O′SM2 − − , − − (4.22) ≡ 2 2 ! m1 and m2 refer to the ﬁrst and second measurement of the two comparative measurements. The mean value of the length of the elongation vectors l (see Equation 4.7) are deﬁned as systematic uncertainty of the measurement in xy-plane in the range of MM SM2 panel:

σxy_SM2 = l = 3µm (4.23)

46 Deformations of Production Line Detector Elements which is at the same order of magnitude with the sTGC cathode board.

Y′ Scale factor= 30000 First measurement l Vector corresponding to 5 µm 4 Entries 20 800 Mean 3.43 Std Dev 2.224 Y (mm) 600 3 400

200

0 2 O′ X′ −200

−400 1 −600

−800 0 0 200 400 600 800 1000 1200 1400 0 2 4 6 8 10 12 X (mm) l (µm)

20190402144126:42 - 20190402101506:40

Fig. 4.16 Schematic diagram of systematic uncertainty of the measurement in xy-plane in the range of MicroMegas readout panel SM2 module. Arrows are corresponding to the length and direction of the displacement of each CRS between the two comparative measurements.

Figure 4.17 presents the results in Phase ① and ②. Elongation vector with the same deﬁnition (see Equation 4.9) with n = 401-416 is used here. The scale factor in the plot on the left of Phase ① is set twice as large as the plot on the right of Phase ② to have a clear view. The largest displacements of the elongation vectors in the two plots are:

lP1 = D−−→P1 = (34 3)µm (4.24) max | 419| ±

lP2 = D−−→P2 = (144 3)µm (4.25) max | 415| ± One can also see a clear outwards elongation vectors gradually increasing from O′ to the edges of the panel. The plot of the coefﬁcient of humid elongation (see Equation 4.12): l over d (see Equation 4.11) is presented here again to see the relation between the length of the elongation and the distance to the centre point, as shown in Figure 4.18.

One can see that the distribution of data points divided into several groups. The elongation in xy-plane is not homogeneous. One defines the coefficient of humid elongation vector −→H ; it has the same direction as the elongation vector, and the length of corresponding coefficient’s

47 4.3 Results of MM Readout Panel with Stereo Strips SM2 Module

Scale factor= 4000 Scale factor= 2000 Reference Measurement Reference Measurement Vector corresponding to 20 µm Vector corresponding to 100 µm 800 800 Y (mm) Y (mm) 600 600

400 400

200 200

0 0

−200 −200

−400 −400

−600 −600

−800 −800

0 200 400 600 800 1000 1200 1400 0 200 400 600 800 1000 1200 1400 X (mm) X (mm)

20190131144617:12 - 2019011190803:6 20190312140938:21 - 2019011190803:6 (a) Elongation in xy-plane at the end of Phase ①. (b) Elongation in xy-plane at the end of Phase ②.

Fig. 4.17 Schematic diagram of elongation in xy-plane in the humid environment. A clear outwards elongation pattern can be seen in both Phase ① and ②.

l ~ d m) µ l ( 140

120

100

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 d (m) 20190312140938:21 - 2019011190803:6

Fig. 4.18 The length of the elongation vector l over the distance to the centre point d. The data points are distributed into groups.

48 Deformations of Production Line Detector Elements value:

−→H −→D = −→H −→D (4.26) | | | | −→H = ϵ | | A same kind of 2D arrow plot, but with the length and direction of the corresponding coefﬁcient of humid elongation vectors is presented in Figure 4.19. The arrows are presented in green color to distinguish from elongation vectors. Each CHE value (in the order of µm/m) is also marked beside the corresponding arrow.

Scale factor= 1000 Reference Measurement Vector corresponding to 100 µm/m 800 80

Y (mm) 63 600 77 72

400 166 65 168 133 200 213 181 181 0 194

−200 123 200 76 160 −400

−600 78 89 60 −800 91

0 200 400 600 800 1000 1200 1400 X (mm)

20190312140938:21 - 2019011190803:6 Fig. 4.19 Schematic diagram of coefﬁcient of humid elongation vector at the end of Phase ②. The length of the vectors, corresponding to the CHE values, are marked beside them in the order of µm/m

One can see larger value on both parallel edges, and smaller on both lateral edges of the trapezoid-shaped panel. From the construction of the panel (see Figure 2.14), two pieces of FR-4 PCBs are glued on both sides of the honeycomb aluminum frame with extra aluminum frames on the two lateral edges for supporting cooling channels. This structure of the aluminum frame gives compression to the elongation of the FR-4 material parallel to y-axis; whereas at the two straight edges of the panel, the stress of the elongation is relatively more

49 4.3 Results of MM Readout Panel with Stereo Strips SM2 Module

free. In other words, if we explain it in Young’s modulus, which describes the stiffness of a material: σ E = ϵ (4.27) where E is Young’s modulus; σ is the stress, or force per unit surface; ϵ is the strain, or proportional deformation (change in length divided by original length), or is the CHE. The stiffness of the panel at the edges with extra cooling channel support frame is higher than

the edges with only honeycomb frame: Elateral > Estraight. It leads to smaller CHE value on the two lateral edges of the panel. This indicates the strip is misaligned in a banana-shape respect to the center of the panel.

Due to time constraints, the module can not be exposed in a high humidity environment for unlimited time. The maximum elongation parallel to x-axis, which is in the direction of the strip pitch of the SM2 panel, is determined as follows. The CHLE (see Equation 4.13) parallel to x-axis of the 20 data points collected regularly in Phase ② are displayed over time as stars in the Figure 4.20a. The natural exponential function is again used here to ﬁt the data p p x with the form of f (x) = e 0 1 + p2, (p0 1 2 R ) according to the increasing trend and − − , , ∈ + the non-zero value of the ﬁrst measurement.

ϵ ~ time x 414 419415 420 416 600 m/m) µ 500 lx/dx (

400 410 411 412 413

409 300

200 406 407 405 408 404 100

0 0 200 400 600 800 1000 1200 1400 1600 1800 2000 time (hour) 401 417402 418 403 (a) CLHE parallel to x-axis of the 20 data sets with the (b) The 20 reference spheres are divided ② corresponding exponential ﬁts in Phase . They are into two groups for analysis.Ä Their num- marked with three different colors. bers are marked in different colors.

Fig. 4.20 Colour coding according to different Young’s Modulus values for ϵx over time in Phase ② with exponential ﬁts and the positions of the corresponding reference spheres of SM2 module.

Different colours are used to indicate the data sets with different Young’s modulus. The numbers of the corresponding reference spheres are also marked with the same colour coding

50 Deformations of Production Line Detector Elements in Figure 4.20b. The red and blue colours represent the data sets with lower and higher E, while the green colour represents the data sets in between. The uncertainty of time combines 3.0 0.2 hours for the gas in the humidiﬁcation chamber to reach a stable RH ± value (see section 3.3), and around 15 minutes of the position measurements at the CMM. 6 5 The uncertainty of CLHE is in the order of 10− - 10− due to the different unit of d achieved from error propagation. One can see two green curves with rapid increasing trend, they are No. 406 and 407. From Figure 4.19, the direction of the elongation is almost 45° to x- and y-axis, but the distance between the CRS to the centre point parallel to x-axis is much smaller than parallel to y-axis.

That leads to a large ϵx value. This indicates the elongation of the strips parallel to x-axis near the the center of the board is larger. The rest of the green curves and the red curves approach to their asymptotes within around 2000 hours. Some of the blue curves are the first, the curves already trend to be flat at around 800 hours; they are the data points from the two lateral edges. One can only see three red curves in the plot, that is because the fit curves from No. 404 and 409 are identical since one defines the centre vector as the average of these two elongation vectors (see Equation 4.22). One do not take the upper two red curves into account, they are from No. 402 and 415 data points, which define the (0, 0, 0) and x-axis of the coordinate system, and also the decreasing blue curve, it defines the x-axis. At the edge of the board, the curve has the largest asymptote value is from N0. 418 reference sphere data point, it approaches to:

ϵ max = (340 1)µm/m (4.28) x_SM2 ± This value indicate the maximal coefﬁcient of humid elongation of the strips in the strip pitch direction, respect to roughly the center of gravity of the panel in an extremely humid environment. Later a simulation could be done to calculate the exact misalignment of each strip of the MM panel.

Following, the results of Phase ③ are presented in the Figure 4.21. The two plots are the results of the panel being air dried for 5 hours (Phase 3.1) and 2 months (Phase 3.2) respectively. Apparently the elongation is shrunken over time. The largest displacement is reduced to

lP3.1 = D−−→P2 = (134 3)µm (4.29) max | 415| ± and lP3.2 = D−−→P2 = (39 3)µm (4.30) max | 418| ±

51 4.3 Results of MM Readout Panel with Stereo Strips SM2 Module

Scale factor= 2000 Scale factor= 4000 Reference Measurement Reference Measurement Vector corresponding to 100 µm Vector corresponding to 20 µm 800 800 Y (mm) Y (mm) 600 600

400 400

200 200

0 0

−200 −200

−400 −400

−600 −600

−800 −800

0 200 400 600 800 1000 1200 1400 0 200 400 600 800 1000 1200 1400 X (mm) X (mm)

20190312190522:22 - 2019011190803:6 20190520134042:49 - 2019011190803:6 (a) Elongation in xy-plane after air drying for 5 (b) Elongation in xy-plane after air drying for 2 hours. months.

Fig. 4.21 Residual elongation in xy-plane in a air drying process. The length of elongation vectors are getting smaller.

One plots the CLHE parallel to x-axis over time once again at the first 17 days in the air drying process with the same colour coding in Figure 4.20b. The result is shown in Figure 4.22. One can see the coefficients are decreasing over time. That means the elongation in x-axis is reducing in the air drying process after a extreme humid environment. Most of the curves approach to their asymptotes within around 600 hours. Some of the blue curves are the first, the curves already trend to be flat at around 450 hours. One set of data is not shown because it is not fitted, it is from CRS No. 413. From Figure 4.21, one can see the length of the residual elongation vector of N0.413 is shrunken, but the direction is also changing over time, the variation of the residual elongation vector parallel to x-axis is small. The fit curve is trend to be flat. The rapidly decreasing green curve is from data at CRS N0. 406. Among the 6 data source from reference spheres glued on the surface of the Kapton-PCB (see section 2.3), the curve has the largest asymptote value is from N0. 407 reference sphere data point, it approaches to: ϵ residual = (49 1)µm/m (4.31) x_SM2 ±

52 Deformations of Production Line Detector Elements

ϵx ~ time 250 m/m) µ

200 lx/dx (

150

100

0 0 100 200 300 400 500 600 700 time (hour)

Fig. 4.22 CLHE parallel to x-axis with the corresponding exponential ﬁts during the ﬁrst 17 days in air drying process. They are marked with three different colors indicating with different Young’s Modulus values.

Conclusion

In z-axis, no obvious deformation is observed, the combination of vacuum and gluing application in the machining process of the panel is in function. For xy-plane, the maximal elongation of the strips in the strip pitch direction in extreme humid environment is estimated from fitting by natural exponential function is (340 1)µm/m. ± However, after the panel lying in the climate room for an air drying process for 17 days, the maximal residual elongation is only (49 1)µm/m. This value can be compared to ± the mechanical tolerance of the single strip accuracy. The value can be found in GERBER file (the ASCI file used to define the nominal positions of the strips for PCB production), which is 30µm. The maximal residual elongation due to humid environment in the strip pitch direction is larger than the mechanical tolerance.

4.4 Results of MM Readout Anode Boards with Eta Strips SE6, SE7, SE8 Modules

In the previous section, a whole MicroMegas readout panel is studied. Young’s Modulus is introduced to explain the non-homogeneous elongation of the strips on the readout board in

53 4.4 Results of MM Readout Anode Boards with Eta Strips SE6, SE7, SE8 Modules

the panel. In this section, the similar modules with eta strips of the three readout boards that are used in the SM2 panel are studied separately. During the programming of position measurement of the boards, it is noticed that the materials already have irreversible plastic deformation. It may occur during the machining and transportation process. Besides, the material has a good quantity of ﬂexibility. Once the tip of the CMM touches the reference spheres on the surface of the boards, the material undergoes an instant elastic deformation, even the force from the tip of the CMM is marginal. This property of the material makes the work for measuring the deformation in z-axis impossible. In that case, the humidity study of the SE6, SE7 and SE8 modules can only focus on the elongation in xy-plane. For every measurement, one places the weights on the boards, just like the method imple- mented for the sTGC cathode board. Only the two different sizes of round-shaped brass weights are used here. They are heavy enough to balance out the plastic deformation. Table 4.4 lists the dates and environment conditions of the measurements. At each measurement, only one board is taken at a time and leaves the other two boards in the humidiﬁcation chamber with closed lid. This is done to minimize the exposure time of the board to the ambient environment, that will lead to evaporation of the moisture absorbed by the board, and this will cause distortion of the results. Due to the time restriction of the project, one directly exposes the boards in the ~ 90% RH and 24 °C environment. To keep in step with the humidity study with the other two objects, one still names it as Phase ②.

Table 4.4 Measurements of MM Readout Boards SE6, 7 and 8.

Environment Date Duration Condition Climate Room Reference Measurement Apr. 12, 2019 ~ 55% RH 22 °C Humid Apr. 12, 2019 - Phase ② 36 days ~ 90% RH 24 °C Environment May. 17, 2019 Dry May. 17, 2019 - Climate Room Phase ③ 26 days Environment June. 12, 2019 ~ 55% RH 22 °C

Figure 4.23 shows the displacement in xy-plane of each CRS between the two comparative systematic uncertainty measurements of the three boards respectively. From left to right in the ﬁgure, readout board SE8, SE7 and SE6 are presented. The centre points of each board

are marked as OSE8/7/6′ respectively. All elongation vectors in each plot are subtracted by the corresponding centre vector −→O′SE8/7/6 (see Equation 4.6). The y-axes of the three plots are set to the same range for a better interpretation.

54 Deformations of Production Line Detector Elements

Scale factor= 4000 Scale factor= 3000 Scale factor= 2000

First measurement First measurement First measurement

Length corresponding to 20 µm Length corresponding to 20 µm Length corresponding to 20 µm 1000 1000 1000 Y (mm)

500 500 500

0 0 0 ′ ′ ′ OSE 8 OSE7 OSE6

−500 −500 −500

−1000 −1000 −1000 0 100 200 300 400 0 100 200 300 400 0 100 200 300 400 X (mm) X (mm) X (mm)

20190411174340:7 - 20190411163524:6 20190411160146:6 - 20190411153621:4 20190411170400:3 - 20190411152114:2

l l l 4 Entries 27 2 Entries 29 3 Entries 29 Mean 10.03 Mean 12.03 Mean 27.23

Std Dev 8.993 Std Dev 8.914 Std Dev 13.31

3 2

2 1

0 0 0 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 40 0 10 20 30 40 50 60 l (µm) l (µm) l (µm) 20190411174340:7 - 20190411163524:6:SE8 20190411160146:6 - 20190411153621:4: SE7 20190411170400:3 - 20190411152114:2: SE6 Fig. 4.23 Schematic diagram of systematic error of measurement in xy-plane in the range of the MM readout anode boards SE6, SE7 and SE8. Arrows are corresponding to the length and direction of the displacement of each CRS between the two comparative measurements.

The scale factor in the most left plot from SE8 is adjusted to be the biggest, and all three arrows in the legend are corresponding to the same value 20 µm. To adjust so is to make the elongation vectors visible at a reasonable scale, and at the same time to make it easier to sense the difference among the three plots. Due to the different placement methods of the three reference aluminum plates, the probability of the boards staying in the same position for each measurement are different. One is able to place SE8 at the same position well, so that it has the smallest systematic uncertainty,

55 4.4 Results of MM Readout Anode Boards with Eta Strips SE6, SE7, SE8 Modules

followed by SE7, SE6 has the largest:

σxy_SE8 = lSE8 = 10µm (4.32)

σxy_SE7 = lSE87 = 12µm (4.33)

σxy_SE6 = lSE6 = 27µm (4.34)

Results in xy-plane in Phase ②

Almost 2 meters long and good property of ﬂexibility and softness of the material make it challenging to hold by hands during transportation. Unfortunately, several reference spheres were dropped from the boards. One could glue new spheres; however, it is impossible to glue the reference spheres to the original position with an accuracy in the range of millimeters. The reference spheres would lose their function in reference. On this account, one excludes them from the analysis in the following plots. Most unfortunately, one of the reference spheres on SE7 involved in deﬁning the coordinate system was dropped during one measurement in Phase ②. The result of placing the SE7 in 90% RH 24 °C environment for 13 days is shown in Figure 4.24a, while the result of the modules SE6 and SE8 in Phase ②, totally 36 days, are shown in the Figure 4.24b.

One can see a clear outwards elongation here again on each board. SE6 module is taken for an example in the following analysis since no reference spheres have dropped from it. l over d is plotted to see if CHE is homogeneous in the range of the board (see Equation 4.12), as shown in Figure 4.25a. Unlike the SM2 panel, a linear distribution of the data points is seen in the plot, so as the plots from SE7 and 8 (see Appendix A). For linear humid elongation, the length of the elongation parallel to x- and y-axis over the vertical distances to the centre

point are plotted respectively. One notices that lx and ly can be proportional to dx and dy respectively. In order to prove whether this hypothesis is true or not, one fits with function f (x) = ax, (a R). The red lines in the Figure 4.25b are the fit results, the slopes of the ∈ functions are the coefficients of the linear humid elongation in x- and y-axis respectively. The χ2 values of the two fits are inside the critical values at 95% probability. One would

accept the null hypothesis, the ϵx and ϵy values from ﬁt function can be taken to represent the coefﬁcient of linear humid elongation:

ϵP2 = (536 30)µm/m, ϵP2 = (477 11)µm/m; (4.35) x_SE6 ± y_SE6 ±

56 Deformations of Production Line Detector Elements

Scale factor= 300 Scale factor= 300 Scale factor= 300 Reference Measurement Length corresponding to 300 µm Reference Measurement Reference Measurement Length corresponding to 300 µm Length corresponding to 300 µm 1000 1000 1000

Y (mm) 800

500 600 500 400

200 0 0 0

−200

−500 −400 −500

−600

−1000 −800 0 100 200 300 400 X (mm) −1000 0 100 200 300 400 0 100 200 300 400 20190429162918:13 - 20190412123958:7: SE7 X (mm) X (mm) (a) Elongation in xy-plane of SE7 after 20190517100421:16 - 20190412113243:8: SE8 20190517105450:12 - 20190412132655:4: SE6 13 days in 90% RH 24 °C environment. (b) Elongation in xy-plane of SE8 and 6 in Phase ②.

Fig. 4.24 Elongation in xy-plane of the three modules in Phase ②. All the boards have clear outwards elongation.

lx ~ dx ly ~ dy 200 m) m) µ l ~ d Data µ 400 Data lx ( ly (

m) Fit Fit µ

l ( 400 150 300 350

100 300 200

250 50 200 100

150 0 p0: 535.8± 29.5 0 p0: 476.9± 10.7 100 χ2: 14.1 χ2: 10.0

50 0 0.05 0.1 0.15 0.2 0.25 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 dx (m) dy (m) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 d (m) 20190517105450:12 - 20190412132655:4: SE6 20190517105450:12 - 20190412132655:4: SE6

20190517105450:12 - 20190412132655:4: SE6 (b) Length of elongation vector parallel to x- and y-axis over (a) Length of elongation vector over dis- the vertical distance to the centre point, with linear ﬁt respec- tance to the centre point. tively.

Fig. 4.25 Length of elongation vector over distance to the centre point and the x- and y-axis components.

57 4.4 Results of MM Readout Anode Boards with Eta Strips SE6, SE7, SE8 Modules

The elongation parallel to x-axis is larger than the one parallel to y-axis, this is consistent with

the length and direction of the arrows one can observe in Figure 4.24. ϵx_SE6 achieved from linear ﬁt of the 8 measurements during the Phase ② is plotted over time, the data are ﬁtted with natural exponential function in the form of f (x) = ep0 p1x + p2, (p0, p1, p2 R ) − − ∈ + to estimate the maximal elongation of the strips in an extremely humid environment. The result is shown in the Figure 4.26.

∈ x ~ time 600 m/m) µ 500 lx/dx (

400

χ2 / ndf 300 0.2751 / 5 p0 6.29 ± 0.08433 p1 0.003226 ± 0.0009373 200 p2 568.2 ± 51.67 Data 100 Fit

0 0 200 400 600 800 1000 1200 1400 1600 1800 2000 time (hour)

Fig. 4.26 ϵx over time in Phase ② of SE6 PCB board with a natural exponential ﬁt.

The asymptote value of the natural exponential ﬁt function is the maximal elongation of the strips parallel to x-axis in an extremely humid environment. The CLHE parallel to y-axis is also determined. We summarise that at 90% RH 24 °C environment, the maximal elongation of the strips parallel to x- and y-axis are respectively:

ϵmax = (568 52)µm/m, ϵmax = (498 17)µm/m; (4.36) x_SE6 ± y_SE6 ± The maximal coefficients of linear humid elongation of the SE7 and SE8 in an extremely humid environment are determined in a same way, the figures can be found in Appendix A, the result are presented in Table 4.5. All the three coefficients in x-axis direction, which is in the direction of strip pitch are larger than the one in y-axis direction, along the strips direction.

58 Deformations of Production Line Detector Elements

ϵmax ϵmax x (µm/m) y (µm/m) SE6 568 52 498 17 SE7 457 ± 36 493 ± 28 SE8 648 ± 29 557 ± 7 ± ± Table 4.5 Maximal coefﬁcient of linear elongation in x- and y-axis after the boards exposing in an extremely humid environment.

Results in xy-plane in Phase ③

The results of air drying process is presented in Figure 4.27. One compares the last measurement of Phase ② and reference measurement of SE6 and SE8 respectively. The displacement of each CRS gets smaller.

Scale factor= 500 Scale factor= 500 Reference Measurement Reference Measurement Length corresponding to 100 µm Length corresponding to 100 µm 1000 1000 Y (mm)

500 500

0 0

−500 −500

−1000 −1000 0 100 200 300 400 0 100 200 300 400 X (mm) X (mm)

20190612161308:26 - 20190412113243:8: SE8 20190606143707:21 - 20190412132655:4: SE6 Fig. 4.27 Residual elongation of the SE6 and SE8 after air drying around 20 days.

Both modules are shrunken after around 20 days in a relative dry environment. Module SE6 is still taken as an example to go into the details about how CLHE change over time. The results after drying SE6 for 20 days are listed below; compare to Equation 4.35, the CLHE

59 4.4 Results of MM Readout Anode Boards with Eta Strips SE6, SE7, SE8 Modules

shrink almost half of the size:

ϵP3 = (287 30)µm/m, ϵP3 = (252 11)µm/m; (4.37) x_SE6 ± y_SE6 ± In order to answer the question if the modules are able to go back to the original shape

as the reference measurement, ϵx_SE6 achieved from the 9 measurements in the air drying process are drawn over time, and ﬁtted with natural exponential function in the form of f (x) = ep0 p1x + p2, (p0, p1, p2 R ); the result is shown in Figure 4.28. − ∈ +

∈ x ~ time χ2 500 / ndf 0.8722 / 6 p0 5.494 ± 0.2411 m/m) 450 µ p1 0.004369 ± 0.002784 p2 ± 400 254.8 67.5 lx/dx ( 350 Data Fit 300

250

200

150

100

0 0 100 200 300 400 500 600 700 800 900 1000 time (hour)

Fig. 4.28 ϵx over time in Phase ③ of SE6 PCB board with a natural exponential ﬁt.

The asymptote value of the natural exponential ﬁt function is the CLHE value of the residual elongation after the board exposed in an extremely humid environment. The determined time of SE6 stops shrunken is around 700 hours. The same analysis is done to the y-axis, and also for SE8 board. Because lack of the coordinate system reference sphere, SE7 board could not be determined. The ﬁgures of the results can be found in Appendix A. The residual elongation values are summarized in Table 4.6.

Compared to the value obtained from the study of the SM2 panel, the residual elongation in xy-plane of a single PCB is much larger. This conﬁrms the signiﬁcance of the application of the vacuum and gluing during the machining process of the modules.

60 Deformations of Production Line Detector Elements

ϵresidual ϵresidual x (µm/m) y (µm/m) SE6 255 68 244 15 SE8 287 ± 21 274 ± 5 ± ± Table 4.6 The residual coefﬁcient of linear elongation in x- and y-axis after air drying process.

Conclusion

Due to already existing irreversible plastic deformation and the good property of flexibility of the readout boards material, the information in z-direction could not be determined. The residual elongation of the boards in the direction of strip pitch after the boards exposed in an extremely humid environment exists. The largest value is (287 21) µm/m, obtained ± from the study of SE8 PCB board. Compared to the value obtained from the study of the SM2 panel ((49 1)µm/m), the residual elongation in xy-plane of a single PCB is much ± larger. This confirms the significance of the application of the vacuum and gluing during the machining process of the modules. Tight packaging during the transportation could be taken into account.

Chapter 5

Summary

In order to study known mechanisms in detail and search for new physics, the LHC is undergoing several phases of upgrade for the purpose of high luminosity. For the muon spectrometer in the ATLAS detector, the innermost endcap Small Wheels (SW) will be replaced by New Small Wheels (NSW), for achieving high precision muon track reconstruction and better Level-1 trigger information. The NSW uses two detector technologies: small-strip Thin Gap Chambers (sTGC) and MicroMegas (MM). An angular resolution of better than 1 mrad will be obtained by strip-wire-pad structure in the sTGC detector layer, and a high spatial resolution of better than 100 µm will be achieved by the 0.5 mm strip pitch of the MM readout board. The deformation of the detector module and strip misalignment have a direct impact on the performance of the detector. Different causes can lead to the deformation; this thesis investigated the impact of humidity on deformations of detector modules in the NSW.

Deformation perpendicular to the module plane and outward elongation in the module plane are observed during the humidity study; they are illustrated and investigated numerically. However, the deformation perpendicular to the module plane can be reduced by application of vacuum and gluing in the machining process of the detector modules. The maximum and residual strip elongation in an environment with up to 90% relative humidity and after air- drying process is evaluated by measurement data. The value of the residual strip elongation of the MM SM2 panel (49µm/m) is at the same order of magnitude with the mechanical tolerance (30µm/m). The residual strip elongation of the sTGC cathode board and MM readout boards could be also reduced during the machining and manufacturing process of the detector modules.

As a future prospect, a simulation frame work can be set up to study impact of strip misalignment on the angular and spatial resolution of the detector modules. Humidity can be

63 taken into account as a parameter in the performance of the detector. The large scale of the humidiﬁcation chamber, the ﬂexible gas input system and the precise thermo-hygrometer can be utilized in the future for similar humidity study of different sorts of material.

64 Appendix A

Figures of the Results

l ~ d l ~ d m) 400 µ l ( 500 l (mm) 350

300 400

250

200 300

150 200 100

50 100 0

−50 0 0 0.2 0.4 0.6 0.8 0 0.2 0.4 0.6 0.8 1 d (mm) d (m)

20190429162918:13 - 20190412123958:7: SE7 20190517100421:16 - 20190412113243:8: SE6 (a) Length of elongation vector over distance to (b) Length of elongation vector over distance to the centre point of SE7 in Phase ②. the centre point of SE8 in Phase ②.

65 lx ~ dx ly ~ dy

m) 140 m) 400 µ Data µ Data lx ( ly ( 120 Fit 350 Fit

100 300

250 80

200 60

150 40 100 20 50 0 p0: 434.1± 14.5 p0: 392.5± 4.6 χ2: 41.6 0 χ2: 22.7 −20 −50 0 0.020.040.060.08 0.10.120.140.160.18 0.2 0.220.24 0 0.2 0.4 0.6 0.8 dx (m) dy (m)

20190429162918:13 - 20190412123958:7: SE6 20190429162918:13 - 20190412123958:7: SE6

Fig. A.2 Length of elongation vector parallel to x- and y-axis of SE7 over the vertical distance to the centre point, with linear ﬁt respectively

∈ ∈ x ~ time y ~ time

m/m) 500 m/m) 500 µ µ lx/dx ( ly/dy ( 400 400

300 χ2 / ndf 1.703 / 1 300 χ2 / ndf 0.4127 / 1 p0 6.185 ± 0.08889 p0 6.186 ± 0.0413 200 p1 0.006823 ± 0.00207 200 p1 0.003804 ± 0.0005177 p2 457.9 ± 35.51 p2 493.4 ± 28.35 Data Data 100 100 Fit Fit

0 0 0 100 200 300 400 500 600 700 800 900 1000 0 200 400 600 800 1000 1200 1400 1600 1800 time (hour) time (hour)

(a) ϵx over time of SE7 PCB board in Phase ② (b) ϵy over time of SE7 PCB board in Phase ② with a natural exponential ﬁt. with a natural exponential ﬁt.

66 Figures of the Results

∈ ∈ x ~ time y ~ time

700

m/m) m/m) 600 µ µ

600

lx/dx ( ly/dy ( 500

500 400 400 χ2 / ndf 12.68 / 5 χ2 / ndf 14.71 / 5 p0 6.434 ± 0.0365 300 p0 6.256 ± 0.01191 300 p1 0.00264 ± 0.0003201 p1 0.002952 ± 0.0001198 ± 200 p2 ± 200 p2 647.6 29.09 557 7.281 Data Data Fit Fit 100 100

0 0 0 200 400 600 800 1000 1200 1400 1600 1800 2000 0 200 400 600 800 1000 1200 1400 1600 1800 2000 time (hour) time (hour)

(a) ϵx over time of SE8 PCB board in Phase ② (b) ϵy over time of SE8 PCB board in Phase ② with a natural exponential ﬁt. with a natural exponential ﬁt.

∈ ∈ x ~ time y ~ time χ2 χ2 600 / ndf 3.577 / 6 500 / ndf 31.73 / 6 p0 5.488 ± 0.07644 p0 5.294 ± 0.02217 m/m) m/m) 450 µ p1 0.004328 ± 0.000944 µ p1 0.005506 ± 0.000383 500 p2 ± p2 ± 286.5 20.81 400 274.6 4.673 lx/dx ( ly/dy ( Data 350 Data 400 Fit Fit 300

300 250

200 200 150

100 100 50

0 0 0 100 200 300 400 500 600 700 800 900 1000 0 100 200 300 400 500 600 700 800 900 1000 time (hour) time (hour)

(a) ϵx over time of SE8 PCB board in Phase ③ (b) ϵy over time of SE8 PCB board in Phase ③ with a natural exponential ﬁt. with a natural exponential ﬁt.

Appendix B

Technical Drawing and Data Sheets

Data Sheet of the Input Nitrogen Gas

69 Data Sheet of the Standard FR-4 Production in Factory

Material Data Sheet THE GUND COMPANY Manufacturers & fabricators of engineered material solutions

Item: NEMA Grade FR4 Glass Epoxy Laminate Description: NEMA Grade FR4 materials are glass fabric reinforced laminates, bonded with ﬂame resistant epoxy resin. The material has the ability to maintain excellent mechanical, electrical and physical properties at elevated temperature to 130 oC. FR4 from The Gund Company is UL, RoHS, and REACH certiﬁed to ensure reliability, safety, and consistency (UL File No. E339275) Standards: NEMA LI-1: Grade FR4 MIL-I-24760/27 IEC 60893: EP GC 202 (sheet)

Availability: English Units (in) SI Units (mm) Thickness: 0.010 to 5.0 0.125 to 127 Laminate Sheets: Standard Sheet Size 48 x 120 122 x 305 FR4 convolute tubes are available from The Gund Company in nearly any custom size Convolute Tubing: of inside and outside diameter, per customer requirements The Gund Company custom fabricates insulation material to the exact speciﬁcations Fabricated Parts: and drawings of our customers.

Key Characteristics Units - English (SI) Typical Values Standard Color -- Green1 Speciﬁc Gravity lb/in3 (g/cc) 1.9 1 Custom colors are available upon request

NEMA LI-1 FR4 Required Properties Key Characteristics Test Method Units NEMA Required Typical Values Breakdown Voltage Condition A 45 min 66 ASTM D-149 kV (0.062”) Condition D-48/50 40 min 65 Permittivity @ 1 MHz Condition A 5.2 max 4.4 ASTM D-150 -- (0.062”) Condition D-48/50 5.4 max 4.5 Dissipation Factor @ 1 MHz Condition A 0.025 max 0.014 ASTM D-150 -- (0.062”) Condition D-48/50 0.035 max 0.015

Length-Wise ft-lb/in 7.0 min 13 IZOD Strength (0.062”) ASTM D-229 Cross-Wise Notched 5.5 min 12 Length-Wise 60.0 (414) min 80 (552) Flexural Strength (0.062”) ASTM D-790 ksi (MPa) Cross-Wise 50.0 (345) min 70 (483) Length-Wise 2000 (907) min 2,500 (1,133) Bonding Strength (0.500”) ASTM D-229 Lb (kg) Cross-Wise 1600 (725) min 1,900 (862) Moisture Absorption (0.125”) ASTM D-570 % 0.15 max 0.10

Flammability Rating UL94 Class V-I V-0

All of the information, suggestions and recommendations pertaining to the properties and uses of the products herein are based upon tests and data believed to be accurate; however, the ﬁnal determination regarding suitability of any material described herein for the use contemplated, the manner of such use, and whether the use infringes any patents is the sole responsibility of the user. There is no warranty, expressed or implied, including, without limitation warranty of merchantability or ﬁtness for a particular purpose. Under no circumstances shall we be liable for incidental or consequential loss or damage. TGCR1015

70 Technical Drawing and Data Sheets

Inventor Drawings Relevant to the Experimental Setup

8 7 6 5 4 3 2 1

F F

E E

3,00

D D

90n

0 ,0 C 4 C

6,00 B B

General Tolerances Form Tolerances Edge Dimensions Surface Scale: Quantity: 1 DIN ISO DIN 7167 DIN 7168-m DIN 6784 - - 1302 - - Date Name Drawn 19.07.2018 hong Checked A Standard A

Physikalisches Institut Universitt Freiburg ball holder 1 /1 A2 Hermann-Herder-Str. 3 State Changes Date Name File Name: C:\Users\hong\Documents\Inventor files\ball holder.idw 8 7 6 5 4 3 2 1

8 7 6 5 4 3 2 1

F F

90 5 10

0 1

E P5,5 E

0 1

D 0 D

0 1

C P8,5 C

0 2

B B 100

General Tolerances Form Tolerances Edge Dimensions Surface Scale: Quantity: 1 DIN ISO DIN 7167 DIN 7168-m DIN 6784 - - 1302 - - Date Name Drawn 09.08.2018 hong Checked A Standard A

Physikalisches Institut Universitt Freiburg connection 1 /1 A2 Hermann-Herder-Str. 3 State Changes Date Name File Name: C:\Users\hong\Documents\Inventor files\connection.idw 8 7 6 5 4 3 2 1

71 8 7 6 5 4 3 2 1

F F

1040

P E E P 30 170 200 20 P P 20

0 0

P 2 A12 A13 A14 A15 A16 A17 A18 2

P 0 A11 3 P P

P 0

7 1

P 0 4

D 1 D P P

P A9 A10 0 8

P 3 P

P 0

P 4

0 7 1 50

C C

3 0

A1A2 A3 A4 A5 A6 5 A7

2 2

20 200 20 30 170 200

B B

General Tolerances Form Tolerances Edge Dimensions Surface Scale: Quantity: 1 DIN ISO DIN 7167 DIN 7168-m DIN 6784 - - 1302 - - Date Name Drawn 24.07.2018 hong Checked A Standard A

Physikalisches Institut Universitt Freiburg plane front 1 /1 A2 Hermann-Herder-Str. 3 State Changes Date Name File Name: C:\Users\hong\Documents\Inventor files\plane front.idw 8 7 6 5 4 3 2 1

8 7 6 5 4 3 2 1

F F

P P P P P E E P 1630 P P 35 200 P 200 120 35 P 20 20

0 0 2 A14 A15 A16 A17 A18 A19 A20 A21 A22 2 P A23 A24 P

P 0

7 7 1 D 1 D P 13 P P 20 330 310 310 310 330 20

P A12 0 8

B1 B2 B4 A13 3 P B3

P 0

7 7 1 P 1 P

P A1A2 A3 A4 A5 A6 A7 A8 A9 A10 A11

0 2 P 2 C C P 20 20 P 35 200 200 120 35 P

B B

General Tolerances Form Tolerances Edge Dimensions Surface Scale: Quantity: 1 DIN ISO DIN 7167 DIN 7168-m DIN 6784 - - 1302 - - Date Name Drawn 24.07.2018 hong Checked A Standard A

Physikalisches Institut Universitt Freiburg plane left 1 /1 A2 Hermann-Herder-Str. 3 State Changes Date Name File Name: C:\Users\hong\Documents\Inventor files\plane left.idw 8 7 6 5 4 3 2 1

72 Technical Drawing and Data Sheets

8 7 6 5 4 3 2 1

F 1630 F 75 75 200 200 80

55 55

5 5

A20 A21 A22 A23 A24 A25 A26 A27 A28 A29 A30 5

0 0

E 2 E 2

A18 A19

D A16 A17 D

0 1

A14 A15

C C

A12 A13

1 1

B A10 A11 B

0 3

A1 A2 A3 A4 A5 A6 A7 A8 A9 0

1 1 200 15 15 200

General Tolerances Form Tolerances Edge Dimensions Surface Scale: Quantity: 1 DIN ISO DIN 7167 DIN 7168-m DIN 6784 - - 1302 - - Date Name Drawn 19.07.2018 hong Checked A Standard A

Physikalisches Institut Universitt Freiburg plane top-1 1 /1 A2 Hermann-Herder-Str. 3 State Changes Date Name File Name: C:\Users\hong\Documents\Inventor files\plane top-1.idw 8 7 6 5 4 3 2 1

8 7 6 5 4 3 2 1

F F

50 24,88 15,66 P 2 ,9 0 10,96 E E

0 R2,38 ,4

8 R2,43

12,13 16,96

D D

3 0

5 A7

C C

0 2

B B

P General Tolerances Form Tolerances Edge Dimensions Surface Scale: Quantity: 1 DIN ISO P DIN 6784 - - DIN 7167 DIN 7168-m 1302 P - - Date Name P Drawn 01.08.2018 hong Checked P A Standard A P P Physikalisches Institut Universitt Freiburg plane front1 1 /1 A2 P Hermann-Herder-Str. 3 State Changes Date Name File Name: C:\Users\hong\Documents\Inventor files\plane front 1.idw P 8 7 6 5 4 3 2 1 P P P P P P P P P 73

References

[1] Ivana Hristova. Future Plans of the ATLAS Collaboration for the HL-LHC. Technical Report ATL-PHYS-PROC-2018-015, CERN, Geneva, Mar 2018. [2] A.R. Djordjevic. Wideband frequency-domain characterization of fr-4 and time-domain causality. 43(4):662–667, Nov 2001. [3] ATLAS Collaboration. ATLAS muon spectrometer: Technical Design Report. Technical Design Report ATLAS. CERN, Geneva, 1997. [4] T Kawamoto. New Small Wheel Technical Design Report. Number CERN-LHCC- 2013-006. ATLAS-TDR-020. Jun 2013. [5] T Schörner-Sadenius. The large Hadron Collider: Harvest of run 1. Springer Interna- tional Publishing, 01 2015. [6] Aranzazu Ruiz-Martinez and ATLAS Collaboration. The Run-2 ATLAS Trigger System. Technical Report ATL-DAQ-PROC-2016-003, CERN, Geneva, Feb 2016. [7] The hl-lhc project, 8, 2017. [8] Fabian Kuger. Signal Formation Processes in Micromegas Detectors and Quality Control for large size Detector Construction for the ATLAS New Small Wheel. Aug 2017. [9] Mauro Iodice. Micromegas detectors for the muon spectrometer upgrade of the atlas experiment. Journal of Instrumentation, 10(02):C02026, feb 2015. [10] Estel Perez Codina. Small-Strip Thin Gap Chambers for the Muon Spectrometer Upgrade of the ATLAS Experiment. Technical Report ATL-MUON-PROC-2015-004, TRIUMF, Jun 2015. [11] Guan Liang. Construction of a stgc prototype for the atlas muon upgrade. Seattle, Feb IEEE 2014. Nuclear Science Symposium and Medical Imaging Conference. [12] Dimos Sampsonidis. The New Small Wheel Upgrade Project of the ATLAS Experiment and the Greek Contribution. Athens, March HEP 2018. Recent Developments in High Energy Physics and Cosmology. [13] Ourania Sidiropoulou. Characterization of the ATLAS-type Micromegas Detectors. PhD thesis, Aug 2018.

75 References

[14] F. Kuger. Production and quality control of micromegas anode PCBs for the ATLAS NSW upgrade. Journal of Instrumentation, 11(11):C11010, nov 2016. [15] Philipp Lösel and Ralph Müller. Design and Construction of Large Size Micromegas Chambers for the Upgrade of the ATLAS Muon Spectrometer. Technical Report arXiv:1508.02541, Aug 2015. [16] Omega gmbh, temperatur- und feuchtetransmitter mit webserver. [17] Omega gmbh, datenblatt ithx. [18] Wenzel präzision gmbh, 10, 2017. [19] Patrick Scholer. Simulation and Measurement of Position Inaccuracies in Large Mi- cromegas Chambers. PhD thesis, Octorber 2017. [20] Wenzel präzision gmbh, measuring software metrosoft cm, 10, 2017.

76 List of Figures

2.1 Illustration of the subsystems in the ATLAS detector...... 4 2.2 Cartesian and cylindrical coordinate system of the ATLAS experiment. . . . 5 2.3 Side view along the beamline of a quadrant of the muon spectrometer. . . . 6 2.4 Schematic layout of the ATLAS trigger and data acquisition system in Run-2. 7 2.5 Programme of the upgrade plans for the LHC baseline...... 8 2.6 Illustration of the fake trigger rate...... 9 2.7 Illustration of fake trigger segments information in the end-cap region of the muon spectrometer...... 10 2.8 Construction of the NSW detector layers...... 11 2.9 Construction of a single layer (left) [9] and a quadruplet (right) [10] of the sTGC detector ...... 12 2.10 Illustration of the working principle of the MM technology and assembled MM quadruplet...... 12 2.11 Construction of the sTGC strip cathode board...... 14 2.12 Construction of readout board of MicroMegas...... 15 2.13 Drawing of a MicroMegas anode PCB (left) and picture of the ﬁnalized board (right)...... 16 2.14 Construction of readout panel of MicroMegas...... 16

3.1 Technical design drawing of the humidiﬁcation chamber...... 18 3.2 Schematic diagram of the gas input system...... 19 3.3 Main part of thermo-hygrometer (left) and the probe (right)...... 21 3.4 An example of the temperature and achieved RH inside the humidiﬁcation chamber...... 22 3.5 Overview of CMM setup in the climate room...... 23 3.6 Probe head of the CMM with a probe tip. [19] ...... 23 3.7 Illustration of the measurement principle...... 24

77 List of Figures

3.8 Layout of the pattern of the reference spheres and schematic diagram of coordinate system of the measurement for sTGC strip cathode board. . . . . 25 3.9 Layout of positions of the reference spheres and schematic diagram of coordinate system of the measurement for SM2 module...... 26 3.10 From the top to bottom are the layouts of positions of the reference spheres and schematic diagrams of coordinate system of the measurement for MM SE6, SE7 and SE8 modules...... 27

4.1 Systematic uncertainty of the measurement in z-axis in the range of sTGC strip cathode board S1 module...... 32 4.2 Deformation of S1 module in z-axis in a humid environment...... 33 4.3 Result of z-axis in a relative dry environment...... 34 4.4 ∆Z over time in the ﬁrst 8 days in Phase ③ with a ﬁt of a natural exponential function...... 35 4.5 Schematic sketch of the effect of convex deformation in z-axis on the measurement result in xy-plane...... 35 4.6 Weights are placed during the measurements used to obtain information in xy-plane...... 36 4.7 Schematic diagram of systematic uncertainty of the measurement in xy-plane in the range of sTGC strip cathode board S1 module...... 37 4.8 Schematic diagram of the elongation in xy-plane in the humid environment. 38 4.9 The data points of l over d at the end of Phase ② are in a linear distribution. 39 4.10 Schematic diagram of the residual elongation in xy-plane of the board in the air drying process in the climate room...... 40 4.11 Schematic diagram of the residual deformation in z-axis and xy-plane after the S1 module being stored in the climate for 2.5 months...... 41 4.12 The length of the elongation vector excluding the eight data points which have inwards elongation...... 42 4.13 Systematic uncertainty of the measurement in z-axis in the range of the MM readout panel with stereo strips SM2 model...... 44 4.14 Deformations in z-axis in a humid environment...... 45 4.15 Deformation in z-axis in the air drying process in the climate room...... 46 4.16 Schematic diagram of systematic uncertainty of the measurement in xy-plane in the range of MicroMegas readout panel SM2 module...... 47 4.17 Schematic diagram of elongation in xy-plane in the humid environment. . . 48 4.18 The length of the elongation vector l over the distance to the centre point d. 48

78 List of Figures

4.19 Schematic diagram of coefﬁcient of humid elongation vector at the end of Phase ②...... 49

4.20 Colour coding according to different Young’s Modulus values for ϵx over time in Phase ② with exponential fits and the positions of the corresponding reference spheres of SM2 module...... 50 4.21 Residual elongation in xy-plane in a air drying process...... 52 4.22 CLHE parallel to x-axis with the corresponding exponential fits during the first 17 days in air drying process...... 53 4.23 Schematic diagram of systematic error of measurement in xy-plane in the range of the MM readout anode boards SE6, SE7 and SE8...... 55 4.24 Elongation in xy-plane of the three modules in Phase ②...... 57 4.25 Length of elongation vector over distance to the centre point and the x- and y-axis components...... 57

4.26 ϵx over time in Phase ② of SE6 PCB board with a natural exponential ﬁt. . . 58 4.27 Residual elongation of the SE6 and SE8 after air drying around 20 days. . . 59

4.28 ϵx over time in Phase ③ of SE6 PCB board with a natural exponential ﬁt. . . 60

A.2 Length of elongation vector parallel to x- and y-axis of SE7 over the vertical distance to the centre point, with linear ﬁt respectively ...... 66

List of Tables

2.1 Environmental parameters of the ATLAS caverns during the operation time in year the 2017 and 2018...... 13

3.1 Technical speciﬁcations of the thermo-hygrometer...... 21

4.1 Measurements of sTGC Strip Cathode Board S1 Module ...... 31 4.2 The value of the coefficient of linear humid elongation parallel to x- and y-axis and ∆Z of each measurement in Phase ② over the time...... 39 4.3 Measurements of MM readout panel with stereo strips SM2 module . . . . 43 4.4 Measurements of MM Readout Boards SE6, 7 and 8...... 54 4.5 Maximal coefficient of linear elongation in x- and y-axis after the boards exposing in an extremely humid environment...... 59 4.6 The residual coefficient of linear elongation in x- and y-axis after air drying process...... 61

Acknowledgements

I would like to offer my thanks to everyone who made my thesis a possibility: my project supervisor Prof. Dr. Ulrich Landgraf, whose door was always open when I ran into difﬁculties during experiments or had a question about an analysis. Dr. Stephanie Zimmermann, who proposed this interesting topic to me, ensured my experiments were properly set up and undertaken, and pointed out the right direction for the next stage of experiments. Prof. Dr. Gregor Herten, our group leader, unites the group by creating a friendly atmosphere and ensures the employees enjoy their work. Dr. Kim Heidegger, my daily advisor, and Dr. Thorwald Klapdor-Kleingrothaus, whose sincere and practical advice helped me both in life and study. I am also grateful for the valuable help given to me by colleagues Dr. Oleg Kuprash, Patrick Scholer, Vladislavs Plesanovs and Niklas Scheidtmann, without whom the project would not have gone as smoothly. I particularly wish to thank the technicians Bernhard Pfeifer and Jürgen Tobias, who played a signiﬁcant role for the entire duration of my project. I am indebted to their professional knowledge and devotion to their work.

Since the conception of a world-class physics research facility in 1949 after World War II, thousands of scientists worldwide have devoted considerable effort to creating the CERN we see today, whose main mission is to reveal what constitutes the universe and how it functions. It is an artwork encompassing all mankind and scientiﬁc and technological progress. At 10:28 am on the 10th September 2008, for the ﬁrst time, a beam of electrons is successfully steered around the Large Hadron Collider, one of CERN’s particle accelerator facilities, and the largest and most powerful accelerator in the world. This pivotal moment marks a new era of discovery at the high-energy frontier.

寄蜉蝣于天地，渺沧海之一粟。 This is a verse from the grand Chinese poet Su Shi, which says that man is like the mayﬂy in the expanse between sky and ground; like a millet ﬂoating on a vast sea. He is happy to be a tiny part of this world and do his job, as am I.

I sincerely dedicate this thesis to my mother, without whose selﬂess, unending and unconditional support, both spiritually and ﬁnancially, I would have been unable to achieve this. She has been such a great source of encouragement and inspiration to me throughout this whole process and I am so grateful to her.

Albert-Ludwigs-Universität Freiburg

Erklärung

Ich versichere hiermit, dass die vorliegende Masterarbeit selbstständig verfasst und keine weiteren als die angegebenen Hilfsmittel benutzt sowie die Stellen der Arbeit, die in anderen Werken dem Wortlaut oder dem Sinn nach entnommen sind, durch Angaben der Quellen sichtbar gemacht wurden. Außerdem versichere ich, dass die vorgelegte Masterarbeit nicht Bestandteil eines anderen Prüfungsverfahrens ist und war.

______(Ort, Datum) (Unterschrift)