Methods for Insulation Test LHC Superconducting Magnets

Operation Methods

Date: 28-01-2004

Prepared By Checked and Approved By Ramkumar Narayanan, BARC, Mumbai Dr Vinod Chohan Department of Atomic Energy, India AT/MTM Jackie Mazras CERN CERN, Switzerland.

Operation Methods are used for testing the LHC Magnets in Cryogenic Conditions in building 2173 (SM18) and are the working documents produced for that purpose only. These Methods are step-by-step procedures that may be followed by the Shift Operators of SM 18 for carrying out different power- tests of the superconducting magnets.

Ref: Procedure for the AC Transfer Function Measurement by F.LAURENT, RAVINDRA MARATHE, AT June 3, 2003

2/23 REF: Procedure for the AC Transfer Function Measurement – For Cluster C

Keywords: Transfer Function, Promit.

This note describes the measurement procedure for obtaining AC transfer function of the cryo- magnets. Two types of measurements are carried out for the magnet :  The impedance of the magnet  The capacitance with respect to the magnet-ground.

The dipole magnets of LHC also have corrector magnets on their ends. Some magnets have Sextupole correctors, while others have Octopole and Decapole correctors in addition to that. This procedure includes the steps for measuring the AC Transfer Function of all these magnets.

In each measurement, a sinusoidal voltage is fed across the magnet terminals at different frequencies from a Programmable Signal Generator. An Analyzer measures the resultant voltages across various parts of the magnet through the voltage-taps. The PROMIT software calculates and plots Gain and Phase curves and tabulates the Impedance and Quality Factor values at different frequencies.

Required material :

- SOLARTRON Programmable Signal Generator and Analyzer (connected to PC). - Personal Computer with PROMIT Software running on Windows platform. - One floppy disk to copy the measurement data from the PC, for putting it on the Server - \\Srv5_div\MATEST\RAW_DATA\DIPOLES\MB\pre_ser\XXX. - A crocodile clip for proper connection with magnet-ground (body). - Test-Box with banana sockets and cable connected to this box with male Fischer connector at the other end. This serves as intermediate unit for connecting the SOLARTRON with different voltage-taps of the corrector magnets. This is not needed for the test on main dipole magnet. - One pair of cables of few meters length, with banana pins on both ends for connection between SOLARTRON Generator’s output and the terminal panel in rack MY05.C.SMTP at the Power-Test-Racks, which is further connected to either the main or the corrector magnet terminals through another cable. - Two reference resistances -10  and 22 k (Resistance Box in the Test rack). - Few flexible cables of different lengths with banana-pins at both ends.

These components are stacked in a closed mobile rack, which is usually kept near the magnets. If it is not there, it must be brought and stationed near the Magnetic-Measurement-Racks of Cluster C, before starting with this test procedure.

3/23 Preparations for AC Transfer Function Measurement : Follow these steps in sequence ---

1. At Cluster C, there is only one Power Converter and one set of data acquisition electronics. Therefore, the first step is to select the correct test-bench and test. This is done at the console sunmta19 (in Rack MY12.C.SMTP) in the Magnetic-Measurement-Racks. Follow the sequence given next : --- On sunmta19, click on the button PLCSE Control, on the small PC Server window that is running for communicating with the Power Converter. --- On the next window, click on the SELECT TEST TYPE button. --- In the next window, select the test-bench Tbx1 or Tbx2, by using the Bench Selector button. ( Tbx1 for C1 bench and Tbx2 for C2 bench) --- In the same window, select proper test type from the scroll-down list of tests. For this test, choose ‘AC Transfer Function Test at 300 K or at 1.9 K’ and then click OK. You will automatically return to the previous window. --- In this window, check for interlocks PC OK, PLCSE OK, test-bench selection, rotary-switch position and temperature. Check faults list by clicking on CHECK FAULTS buttons at the bottom of this window. This list shows the faults relevant to the selected test type. --- Make sure that the faults are cleared and all interlocks are OK. For this, you may need to follow the rest of this procedure. Do that and check the faults and interlocks again. --- At the lower part of the Rack MY04.C.SMTP, at the Power-Test-Racks, check the Inter-conn. Panel, for the status of the test-bench and test-type selection. It must show red lamp for the selected test-bench and green lamp for the other test-bench. There are three types of tests defined and the yellow glowing lamp in the vertical row on the right end of this panel shows the selected type. For this test, QCD lamp must glow for the selected test-bench (Tbx1 or Tbx2).

This step is mandatory; because the data-acquisition and protection electronics would otherwise, show fault condition for wrong magnet and trigger some un-wanted measures like firing of quench heater power-supplies and data-acquisition.

2. Make sure the power supplies to the main dipole and auxiliary magnets (correctors) are in OFF position. It is mandatory, that the rotary switches are put in short circuit (CC) position or to the other bench (the one not under this test). At the CFB platform, there are five rotary switches. Two are for the dipoles and the rest three for the correctors. For the dipoles, one rotary switch is for selecting one of the two test-benches (dipoles) or CC option and the other for selection of polarity. For the correctors, there is one rotary switch for selecting one of the two CD correctors (of the two benches), one for selecting one of the two EF correctors (of the two benches) and the third for connecting the Corrector P.S. to the reference magnets.

4/23 3. Discharge all (four) high field (HF) quench heater power supplies by pressing the RED button on the corresponding (two left-most) cards in the Safety Matrix crate and switch the supplies OFF. This is to avoid the accidental discharge of these power supplies into the magnet’s quench-heater strips, while disconnecting the voltage-tap cables.

4. Switch OFF both high frequency and low frequency acquisition applications at the data acquisition console (PC). This is to avoid the unwanted data acquisition by the triggers generated while disconnecting the voltage-tap cables. Alternately, one can disable the (two right-most) cards corresponding to high frequency and low frequency data acquisition in the Safety Matrix crate.

5. If the magnet is at cold, disable the card corresponding to quench valve, in the safety matrix crate, to avoid the unwanted venting of Helium gas to the balloon, by the triggers generated while disconnecting the voltage-tap cables.

6. From the LF data acquisition window “LF OnlineWeb.vi”, note-down the temperature inside the main magnet (TT821). This is to be done before disconnecting the cables from the distribution box.

7. Do not disconnect anything at the BC (as done for Cluster A) for the test on main dipole. When testing correctors, disconnect cable from A6 and connect another long cable, with burndy-connector at the other end, to A6 to bring the corrector-voltage-taps to the Test Box of the Mobile-Rack.

8. Disconnect two voltage-tap cables RVLA and RVLB located on the two current leads the main dipole magnet (at CFB). Their connectors are smaller than the similar ones at CFUs of Cluster A.

9. Disconnect two voltage-tap cables on the two current leads of corrector CD (at CFB). Their connectors are smaller than the similar ones at CFUs of Cluster A.

10.Disconnect two voltage-tap cables on the corrector EF current leads (at CFB). Their connectors are smaller than the similar ones at CFUs of Cluster A.

11.Disconnect another cable (with a bigger connector) labeled “V Clamp 600A / C1 (or C2)”, located next to the EF current leads.

12.If the magnet is at cold, check the cryogenic system supervision window to make sure that the liquid helium level inside the magnet (LE106) is more than 80%. If it is at warm, make sure there is no helium gas inside the magnet.

Now follow the procedure given below, for obtaining AC Transfer Function of the main dipole magnet.

5/23 Part A. MAIN DIPOLE MAGNET : Measurement of magnet impedance:

Each LHC Dipole cryo-magnet is made up of four parts : Dipole 1 – Upper Coil and Lower Coil and Dipole 2 – Upper Coil and Lower Coil.

To analyze the “health” of a dipole, it’s important to measure the impedance of each of these parts separately. These parts are illustrated below:

Trajectoires des protons

D1 = D1Lower Coil + D1Upper Coil (same for D2) WM (Whole Magnet) = D1 + D2

To test each part of the magnet, a total of 7 measurements are to be made in this test. Table - 1 given on Page 7, gives the correspondence between the Test Box sockets and magnet voltage- taps for measuring voltages across various parts of the magnet. !!! Do not connect any diode bridge !!!

Now, follow these instructions :

- Refer the following block-diagram and make all interconnections as shown.

- Lay the few meters-long twisted-pair cable from mobile-rack to the rack MY05.C.SMTP at the Power Test Racks and connect both its banana pins to the two banana sockets 6/23 labeled as AC Signal / C1 or AC Signal / C2, depending on the bench under test. Do not connect the other end of this cable at the mobile-rack at this stage. Two cables have been laid from this panel to the two CFBs. At the relevant CFB, connect the AC-cable to either Dipole-magnet terminals or Corrector terminals, as per the need. Holes have been drilled on the terminal blocks for this purpose.

- Use the 10 Ohms resistor of the resistance-box provided in the mobile-rack.

- At the rack MY12.C.SMTP at the Magnetic-Measurement-Racks, just above the Console PC, there is one panel with two graphic-layouts of the Dipole magnet with all the V-Taps indicated and numbered. There are banana sockets on these layouts for outputs from all the V-Taps of the main dipole. These are provided for two groups of tests. Use the banana-sockets of the layout for QCD & RRR Outputs for making the connections for the AC Tr. Function test of Main Dipole magnet.

- Using flexible cables, make the connections as shown in the block-diagram below.

- Switch on the PC and SOLARTRON Generator / Analyzer provided in the mobile-rack.

- On the PC, “Windows Loading….” appears, followed by a Message Box – “Welcome to Windows”. Click “Cancel” on this box.

- Click “OK” on the next message - “NICE Authentication Failed”. No need to connect to the network. - Click “OK” on the next Message - “NICE Welcome. The PC is in standalone mode….”. - Start the software PROMIT by double-clicking its icon on the desktop.

- Fill up this next screen ‘Login.vi’ that appears, as shown : 7/23 Enter the Operator’s value of the name reference resistance “10”

Choose the type of measurement “Impedance” Name of the Name of the CFU + Dipole Temperature of the magnet

- Click ”OK”, and following new window ‘Main Program.vi’ will appear.

- Select “Single Freq” in the selection-box ‘Type of sweep’ at the upper left of this window.

- In the “Sweep Setup” box, put the amplitude to 0 V,

8/23 - Click “Start Sweep”. This is done for making the output of the generator, zero, before any connection with the magnet.

- Wait until a new screen appears.

- Now connect the few meters long cable, coming from the panel in MY05.C.SMTP, to the SOLARTRON as shown in the block-diagram. Follow the polarity convention.

- Check all the connections (Refer Tabla-1 next). + - Voltage Tap On Test Voltage On Test Measure Name Box Tap Name Box WM EE112 2 EE212 5 TABLE - 1 D1 EE112 2 EE113 3 D2 EE211 4 EE212 5 D1lc EE112 2 EE119 7 D1uc EE119 7 EE113 3 D2uc EE211 4 EE219 8 D2lc EE219 8 EE212 5

It’s important to respect the polarity (for the low frequency).

- Now, select “Compl.Sweep”, in the ‘Type of sweep’ box.

- Fill the “Sweep Setup” as given next :

- Start the measurement by clicking “Start Sweep”.

- Wait till the measurement is being carried-out. This is indicated by another window, saying ‘Sweeping, Patience s.v.p’, on top of the earlier window. - Then this window disappears and curves are displayed on the existing window.

- Check the curves and the values of impedance against the following:

9/23 At Warm

Part of Inductance Capacity for the for 10 Hz 10 kHz magnet In mH  2 mH In nF  70 nF

WM 99 160 D1 49 320 D2 49 320 D1lc 25 850 D1uc 25 500 D2uc 25 500 D2lc 25 850

- At low frequency, the gain is constant - Then, the gain increase per 20dB per decade from 1Hz to 5kHz - Phase start from +15 to  -90 - There is a resonance frequency at high frequency

At Cold

Part of Inductance for Capacity for 10 the 10 Hz (mH)  kHz (nF)  70 magnet 2 mH nF WM 76 120 D1 38 250 D2 38 250 D1lc 19 600200 D1uc 19 350 D2uc 19 350 D2lc 19 600200

- The slope of the gain is +20dB/ decade from 1Hz to 9kHz - Phase start from +90 to  -90 - There is a resonance frequency at high frequency

- Click “save” button that is below the graph on the right side.

- Following screen appears (with blank ‘comments’ window) :

10/23 - Enter following information concerning the measurement in the ‘comments’ window : “Name of the magnet” “part of the magnet under measurement” “voltage-tap numbers” “Magnet Temperature” “Ambient Temperature and humidity” … An example : 1008 D1lc EE112-EE119 1.9K 310K 50% …

- Put data in an proper folder of the PC. Create it, if not present. For example : Folder : C:\PROMIT\HCMBB_A001-01000008 (name of the magnet)  Folder : Before-Quench (History of the magnet)  Folder : Cold (temperature of the magnet)  File : D1lc-1008-1.9K.dat

- Now, if

o You need to measure impedance of another part of the same magnet,

- Change the connection on the Test-box – refer Table - 1.

- Repeat steps of the Procedure – starting at

o You need to measure the impedance of the corrector magnet,

- Refer to Procedure - after going through Part B next.

o You need to measure the capacitance of dipole magnet with respect to magnet- ground (after completing the 7 measurements for the impedance),

- Refer to Procedure - after going through Part C.

o You have completed all the measurements and need to disconnect the magnet :

- Click “single Freq.”

11/23 - Enter 0 V in the “Sweep Setup” box

- Click “start sweep”

- Wait until the screen “Sweeping” disappear.

- You can now disconnect the magnet cable from SOLARATRON.

- Go to at the end of this procedure for normalizing all the connections.

Part B. CORRECTOR MAGNETS : Measurement of magnet impedance:

These measurements are carried out only when magnet is at 1.9 K.

There are three types of corrector magnets - Sextupole, Octopoles and Decapoles.

MBA type Dipole magnets have the following layout for the correctors :

MBB type Dipole magnets have the following layout for the correctors :

12/23 The above layouts show that, the MBA type magnets have all three correctors, while the MBB type magnets have only Sextupole correctors. Accordingly, the measurements for MBB type magnets are a subset of those for MBA type magnets. This is explained below. For MBA type Magnets : A total of 4 measurements are to be made. Next table gives the correspondence between the Test Box sockets and magnet voltage-taps for measuring voltages across various parts of the magnet. + - Voltage Tap On Test Voltage On Test Measure Name Box Tap Name Box With ac signal fed across CD terminals at CFU Table - 2 Sextupole External EE831 1 EE951 6 Decapole Internal EE951 6 EE931 2 Decapole External EE851 4 EE831 1 With ac signal fed across EF terminals at CFU Octopole External EE841 3 EE941 5

For MBB type Magnets : Only one measurement is to be made. Next table gives the correspondence between the Test Box sockets and magnet voltage-taps for measuring voltages across various parts of the magnet. + - Voltage Tap On Test Voltage On Test Measure Name Box Tap Name Box 13/23 With ac signal fed across CD terminals at CFU

Sextupole External EE831 1 EE931 2 Table - 3

It’s important to respect the polarity (for the low frequency).

Now, follow those instructions :

- Select “Single Freq” in the ‘Type of sweep’ selection box.

- In the “Sweep Setup” box, put the amplitude to 0 V,

- Click “Start Sweep” and wait until the screen “Sweeping” disappears. This is done to make the generator output ‘zero’, before any change in the connections with the magnet.

- Now disconnect the cable from magnet (dipole or correctors) terminals.

- Refer the following block diagram and make all interconnections as shown. - Connect the 25 meters-long cable’s banana pins to the two corrector-magnet terminals, C and D or E and F, as the case may be. Refer the layouts given before. Do not connect the other end of this cable at the mobile-rack at this stage. - Use the 10 Ohms resistor of the resistance-box provided in the mobile-rack, as before.

- Disconnect the Test-box cable connector from RBA8 and connect it to RDA8 at the DB. Connect A6 and disconnect A4 at the BC. Thus, the voltage-taps of corrector-magnets are brought to the Test-box through A6 and RDA8.

- Use the flexible cables with banana pins for the remaining connections. For these connections, refer Table - 2 and Table - 3, as the case is.

- No diode bridge is needed for corrector measurements.

14/23 - On the PROMIT window on the PC, click “Back to Login”.

- In the ‘Login.vi’ window, that appears, change only the panel “device under test” to –“MCS-name of magnet” and click “OK”. Use MCO or MCD in place of MCS, as the case may, if the magnet under test is not a Sextupole.

- In the window ‘Main Program.vi’, select ‘Quick Sweep’ in the ‘Type of Sweep’ box and fill following values in the ‘Sweep Setup’ and do a quick measure by pressing ‘Start Sweep’:

- Check the curve and the values against the following : (NOT COMPLETE YET)

- Sextupole (Single Pole) :-

15/23 At Warm

Normal Inductance Values in mH Frequency 10 100 1000 10000 (Hz) Inductance 22 22 15 12 (mH)

At Cold

Normal Inductance Values in mH Frequency 10 100 1000 10000 (Hz) Inductance 575 8 7 5 (mH)

- Octopole (Single Pole) :-

16/23 At Warm

Normal Inductance Values in mH Frequency 10 100 1000 10000 (Hz) Inductance ? ? ? ? (mH)

- Decapole (Single Pole) :-

At Warm

Normal Inductance Values in mH Frequency 10 100 1000 10000 (Hz) Inductance ? ? ? ? (mH)

- If the curves seem good, don’t save this file, but perform another measurement by putting following values in the “Sweep Setup” after selecting ‘Compl.Sweep’

- The measurement takes about 20 minutes.

- Click “save” button that is below the graph on the right side.

- Following screen appears (with blank comments window):

- Enter following information concerning the measurement in the ‘comments’ window : “Name of the magnet” “part of the magnet under measurement” “voltage-tap numbers” “Magnet Temperature” “Ambient Temperature and humidity” … An example : 1008 MCS EE831-EE951 1.9K 310K 50% …

- Put data in a proper folder in the PC. Create it, if not present. For example : Folder : C:\PROMIT\HCMBB_A001-01000008 (name of the magnet)  Folder : Before-Quench (History of the magnet)  Folder : Cold (temperature of the magnet) Folder : Correctors File : MCS_ Ext-1008-1.9K.dat

- Note that the results should be saved in a file in a separate folder named ‘Correctors’.

- For MBA type magnets, go to step for performing next measurement on Correctors, by changing connections on the Test Box as per Table - 2 ,

18/23 - If all measurements on Corrector magnets are completed, then proceed to Part C given next in this procedure.

- For MBB type magnets, there is no more measurement needed, therefore proceed to Part C of this procedure.

o If you have completed all the measurements and need to disconnect the magnet :

- Enter 0 V in the “Sweep Setup” box

- Wait until the screen “Sweeping” disappear.

- You can now disconnect the magnet cable from SOLARATRON.

- Go to at the end of this procedure for normalizing all the connections.

Part C. MAIN DIPOLE MAGNET: Measurement of capacitance with respect to Magnet Mass :

This measurement is carried out by shorting the dipole magnet terminals and feeding the swept frequency signal between the magnet terminals and magnet mass (ground).

Measure the capacitor-Ground :

- Click “Single Freq.” in the already existing ‘Main Program.vi’ window

- Enter 0 V in the “Sweep Setup” box and click “start sweep”

- Wait until the screen “Sweeping” disappear and then click “Back to login …”

- Fill up the next screen, as shown : 19/23 Operator ‘s name Enter the value of the reference resistance “22000” Choose the type of measurement “Impedance to Earth” CAPA Name of the CFB + + Temperature of the magnet Name of the Dipole

- Click ”OK” and the usual ‘Main Program.vi’ window shall appear.

- Refer the following block diagram and make all interconnections as shown.

- Connect all cables as shown and use a crocodile clip to connect the ground. The Test-Box is not needed for this test, because the voltage tap signals are not needed. Use the 22 k Ohms resistor.

The diode bridge is useless

- On the ‘Main Program.vi’ window, click “Compl.Sweep” and fill “Sweep Setup” like this :

- Start the measurement by clicking “Start Sweep”.

- Wait until the measurement stops and the window “Sweeping” disappears and the curves of the measurement appear on the graph.

- Check the curve and the value of capacitance against the following : At Warm

- The slope of the gain is -20dB per decade from 1Hz to 10kHz

Normal values in nF for the capacitor-ground (30 nF) WM At 10 kHz 450

At Cold

- The slope of the gain is -20dB per decade from 1Hz to 10kHz

Normal values in nF for the capacitor-ground (30 nF) WM At 10 kHz 590

21/23 - Click “save” and fill the new screen as follows:

- Enter information concerning the measurement in the ‘comments’ window: “Capa” “Name of the magnet” “Magnet temperature” “Ambient Temperature and humidity” example : Capa 1008 1.9K 300K 50%

- Put data in a proper folder in the PC. Create it, if not present. For example : Folder : C:\PROMIT\HCMBB_A001-01000008 (name of the magnet)  Folder : Before-Quench (History of the magnet)  Folder : Cold (temperature of the magnet)  File : Capa-1008-1.9K.dat

- Enter an amplitude of 0 V (in the “Sweep Setup” box)

- Wait until the screen “Sweeping” disappears.

- Disconnect the magnet cable from SOLAROTRON.

- Disconnect all the connections made for this test.

- Refer the preparatory steps given at the beginning of this procedure for normalizing all the connections.

- Transfer all the data files of the test on the floppy disk provided for this purpose, before switching off the PC.

- Switch off the PC and SOLAROTRON and disconnect the power from the Mobile-rack.

- Transfer all the data files from the floppy-disk to the data-base by copying them in

\\Srv5_div\MATEST\RAW_DATA\DIPOLES\MB\pre_ser\XXX

22/23 - TEST COMPLETED.

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