The PandaX-III experiment Xenon high pressure gaseous TPC in search for neutrino-less double-beta decay Damien Neyret on behalf of the PandaX-III collaboration CEA Saclay IRFU/SPhN 23/05/2017

Physics The PandaX-III collaboration The high-pressure gaseous Xenon TPC Detector studies Prospects

CEA DSM Irfu Neutrino: Majorana particle ?

Dirac or Majorana fermions Majorana: particle and antiparticle are the same Could be observed on neutrinos (neutral particles)

Implications of Majorana neutrinos Violation of conservation of lepton number → path to explain matter- asymmetry in universe ? Neutrino mass scale

May be observed in double- beta decays Neutrino annihilation in double-beta decay reaction Two neutrino mass hierarchy scenarios

CEA DSM Irfu 23 May 2017 The PandaX-III experiment Damien Neyret MPGD 2017 2 Neutrinoless double-beta decays

Double-beta decays with Neutrinoless double-beta neutrinos decays 2 e⁻ and 2 νν emitted 2 e⁻ emitted only Observed in several nuclei (136Xe, Not foreseen by Standard Model 76Ge, 130Te,...) Sign Majorana neutrinos 2nd order process → very low Fixed electron energy Qββ = 2.46 MeV decay probability (2.3.10²¹ y) Double-beta decay study requests

Excellent energy resolution: 1-3% at Qββ Very low gamma contamination → radiopurity Event topology reconstruction

γ background

2β signal 2.5MeV CEA DSM Irfu 23 May 2017 The PandaX-III experiment Damien Neyret MPGD 2017 3 The PandaX-III collaboration

Particle AND Astrophysical Xenon Follows PandaX-I and II experiments on search for with dual- phase Xenon China: Shanghai Jiao Tong University (SJTU), University of Science and Technology of China (USTC), , China Institute of Atomic Energy, , Sun Yat-Sen University, Central Chinal Normal University USA: University of Maryland, Lawrence Berkeley National Laboratory Spain: University of Zaragoza France: Commissariat à l'Energie Atomique (CEA) Thailand: Suranaree University of Technology

CEA DSM Irfu 23 May 2017 The PandaX-III experiment Damien Neyret MPGD 2017 4 Major characteristics of the PandaX-III experiment

Search for neutrinoless double-beta decays in 136Xe TPC with 10 bar Xenon gas mixture Direct read-out of ionization electrons, no scintillation read-out Effort to deeply reduce gamma source Yalong river contamination JinPing underground laboratory in Sichuan (China), world deepest laboratory (~1µ/m²/week) 5 TPC modules 200kg Xe each Goal: 1 ton Xenon in 2022, first module 2018

CEA DSM Irfu 23 May 2017 The PandaX-III experiment Damien Neyret MPGD 2017 5 High pressure TPC modules

5 TPC modules In 10m-deep highly-purified water pool 200kg 10 bar gaseous Xenon mixture with 1% tri-methyl amine (TMA) Copper structure for low radioactivity 2 half TPC, 1.5m diameter and 2 m long in total Read-out on both end-caps

1st module Read-out by Microbulk Micromegas for good energy and spatial resolution 1.5m ~40 detectors of 20x20cm² per end-cap Expected to be ready for 2018

2 * 95cm

CEA DSM Irfu 23 May 2017 The PandaX-III experiment Damien Neyret MPGD 2017 6 Read-out with Microbulk detectors

Principle Micromegas with a copper clad 50µm-thick kapton foil 50µm diameter holes Top face → mesh Bottom face → read-out plane Studied by IRFU and Zaragoza Used in CAST, n_TOF (at CERN) Advantages Constant kapton foil thickness → very good gain homogeneity → best energy resolution for MPGDs Excellent radiopurity ~0.1 µBq/cm² for 214Bi and 208Tl Characteristics X and Y read-out on same board 20x20 cm large detectors, 3mm pitch

CEA DSM Irfu 23 May 2017 The PandaX-III experiment Damien Neyret MPGD 2017 7 Focusing of electrons to active area

Goal: to not loose electrons between two Microbulks Initial solution: guard wires under the kapton layer Under study: Voltage applied on copper back plate

CEA DSM Irfu 23 May 2017 The PandaX-III experiment Damien Neyret MPGD 2017 8 Mounting of the read-out planes

Preparation of detectors Gluing on a copper plate Kapton flat cable part of the detector, bent toward the end-cap Cable-cable connection to decouple the detector from the vessel pass-through

View of the surface of a detector

Detector positions Direct cable to on the 1.5m- cable connection diameter end-cap

CEA DSM Irfu 23 May 2017 The PandaX-III experiment Damien Neyret MPGD 2017 9 Read-out electronics of 1st module

AGET read-out ASIC Charge sensitive preamplifier 120fC to 10pC dynamic range Analog filter 50ns to 1µs peaking time 64 channels sampled at 1 to 100MHz Multiplicity signal available ASTRE chip: evolution of AGET, up to 8µs peaking time 1st module read-out electronics Front-end cards (USTC) close to detectors, 1 card for 2 Microbulks (4 AGET chips) Back-end cards (Saclay) out of the TPC, optical fiber connection Data reconstruction, analysis and MC with REST package (cf. J. Trigger/Clock Module(s) GbE or Galan's talk) Electronics gas volume Copper 10 GbE (1 bar air or neutral gas) Shield Optical P-FEC fibers P-FEC P-FEC Data acquisition PC(s) Detectors P-FEC Copper Purified Air TPC gas volume water (1 bar) (10 bar 136Xe) (1 bar) CEA DSM Irfu 23 May 2017 The PandaX-III experiment Damien Neyret MPGDPower 2017 supply 10 Why Xenon + TMA gas mixture ?

Interest of trimethyl amine Quenching gas for electron amplification Decrease electron diffusion in TPC → better track reconstruction and background rejection Improves energy resolution (cf next slide) Suppress scintillation

Xenon + 2% TMA Pure Xenon

MC of double- beta decay at 10 bar ~50cm drift

Plot from T-REX project Amplitude at read-out plane

CEA DSM Irfu 23 May 2017 The PandaX-III experiment Damien Neyret MPGD 2017 11 Microbulk energy resolution

Low γ energy studies Zaragoza, Coimbra, Saclay γ 22 keV Conditions: up to 10 bar Xenon or Xe+TMA gas mixture Pure Xe At 22 keV (109Ag K line) ● Pure Xenon → ~30% FWHM ● Xe + TMA →~10% FWHM Xe + 1% TMA ● Extrapolated to 1% resol at 2.5 MeV Higher γ energy studies T-REX ERC project at Zaragoza, Xe + 1% TMA 20cm large prototype

CEA DSM Irfu 23 May 2017 The PandaX-III experiment Damien Neyret MPGD 2017 12 Studies on a TPC prototype

TPC prototype at SJTU Up to 50kg 10bar Xenon gas mixture Read-out with 7 Microbulks Already mounted with 1 Mbulks Mounting with 2 and then 7 Mbulks ongoing

78cm

66cm

CEA DSM Irfu 23 May 2017 The PandaX-III experiment Damien Neyret MPGD 2017 13 Energy resolution with the TPC prototype

TPC prototype Measurements with Tests ongoing at SJTU with different pressures 1 Microbulk only and gas mixtures 1 mounted Microbulk only → limits event size, thus initial X-ray maximum energy Very preliminary energy resolution measurements with different sources Measurements with 7 detectors foreseen soon

Energy resolution with Ar+5%iso 1bar 241Am source Mounting with 2 Microbulks ongoing 13.9 keV peak: 17.5% FWHM

Preliminary

Extrapolation to Qββ: 17.8 keV peak: 1.3% and 1.44% FWHM 17.1% FWHM

Plot from Shaobo Wang (SJTU)

CEA DSM Irfu 23 May 2017 The PandaX-III experiment Damien Neyret MPGD 2017 14 R&D for next modules: TopMetal

Direct read-out of ionization electrons Developed at LBNL & CCNU Electron detection with low noise chips on anode plane 30 e⁻ noise level without charge amplification Electrons focused with drilled electrode Good radio-purity

CEA DSM Irfu 23 May 2017 The PandaX-III experiment Damien Neyret MPGD 2017 15 R&D for next modules: MM with better energy resolution Microbulks with segmented mesh Anode → X, mesh → Y Energy read-out on each side Only one Kapton layer Already used in n-TOF Thin Microbulks 50µm thickness not optimal for high pressures Systematic measurements foreseen at variable thickness and pressure in order to determine optimal characteristics Limitation: 25 and 12µm-thick Kapton material barely available, a large quantity must be ordered at once Bulk Micromegas with improved electrodes Thin mesh (like 4µm thick electroformed mesh) to avoid gap variation of woven meshes Polished anode plane for homogenous surface amplification

CEA DSM Irfu 23 May 2017 The PandaX-III experiment Damien Neyret MPGD 2017 16 Conclusions

PandaX-III: search for neutrino-less double-beta decays Original approach ● high pressure gaseous Xenon 136 TPC ● direct ionization read-out ● gamma background rejection with event topology Important challenges ● energy resolution <3% FWHM, up to 1% ● Radiopurity < 10⁻ ³ c/keV/kg/year First 200kg module Pilot module for the full experiment (5 modules) Microbulk read-out with expected energy resolution better than 3% Read-out to be defined for the next modules, R&D in progress More details in the CDR Science China Physics, Mechanics & Astronomy, 60 (6) 061011 (2017) ArXiv 1610.08883

CEA DSM Irfu 23 May 2017 The PandaX-III experiment Damien Neyret MPGD 2017 17