Cryogenic Testing of Superconducting Corrector Magnets for the LHC Main Dipole

Transcription

1 Cryogenic Testing of Superconducting Corrector Magnets for the LHC Main Dipole A.M. Puntambekar SC Tech Lab, AAMD Div. Raja Ramanna Centre For Advanced Technology, Indore Workshop on Cryogenic Science & Technology, April 2006 Inter-University Accelerator Centre, New Delhi

2 Introduction Out line Magnet Specification Cryogenic testing Acceptance criteria 4.2 K Test facility Improving productivity Test Results

3 Sextupole Corrector Magnet (MCS) Decapole Corrector Magnet (MCD) Octupole Corrector Insert (MCO)

4 LHC String test assembly Spool correctors inside cold mass MCS and MCDO (Inside) Function To correct the systematic field errors of the LHC Main Dipole They Share the same cryostat as that of Main Dipole Their proper functioning is as important as Main Dipole

5 Sextupole Corrector Magnet (MCS) Qty 1232 nos MCS

6 Decapole Octupole Corrector Magnet (MCDO) Qty 616 Nos MCDO

7 Prototype Development at RRCAT, Indore Tooling Different Critical components Coil winding machine, Manual & Automatic Ultrasonic welding machine Prototype cryogenic test facility

8 Transfer of technology to Indian industry for series production SC Magnet production facility in an Indian industry Clean area 1000 Class Automatic coil winding machine Clean room Class

9 SC Magnet Cross Section Connection support plate mm Shrinking Cylinder Protection Resistor SECTION - AA SC Coil Magnetic shielding Scissor Laminations

10 MCS & MCDO Magnet specifications MCS MCD MCO Unit Nominal field along the X-axis (m) 1970 x 2 T/m x 10 6 x 4 T/m x 3 T/m 3 Overall length with shield mm Nominal operation current A Working temperature K Turns per coil 2 x 13 2 x Peak field T Theoretical quench current at 1.9K / 4.2K 1300 / / /195 (MCD set to I nom ) A Self inductance mh Mass ~5 ~ 4 Kg

11 Superconducting wire specifications Material Nb-Ti in copper matrix Dimension of insulated wire (mm 2) / x 0.38 ±0/-0.01 Insulation PVA Insulation thickness (mm) 0.06 ± ± 0.01 Dimensions bare conductor (mm 2) x 0.32 Filament diameter (µm) 7 φ 10 Twist pitch (mm) 14 ± 2 18 ± 2 Cu/SC ratio ± 0.1 RRR 100 > 70 Critical current {5T, 4.2K} (A) 650, , 110

12 Cryogenic testing at 4.2 K Training Measurement of Contact resistance Leakage current Hot spot temp. estimation Retraining after a thermal cycle to room temperature

13 Cryogenic Test Acceptance criteria Parameter MCS MCD MCO No training quench is allowed at nominal current 550 A 550 A 100 A In max. 5 training quenches magnet must reach ( 10 ) 850 A 800 A 150 A No Re-training quenches are allowed at or below (after a heat cycle to room temperature) 850 A 800 A 150 A Contact resistance ( at I nom ) nω <35 <30 <50 Leakage Current at 4.2 K, 1.5 kv < 3 µ A

14 PREPARATION OF INSERT LOADING INSERT INTO CRYOSTAT EVACUVATION OF LHe VESSEL PURGING OF He GAS TRAINING OF MAGNET LHe TRANSFER AT CONTROLLED /min LN 2 TRANSFER Over night cooling RETRAINING QUENCH FIRST QUENCH >550A FIFTH QUENCH>850A YES MAGNET PASSED QUENCH FIRST QUENCH >850A NO FAILED WARMING OF MAGNET TO RT YES Over night warming CRYOGENIC TRAINING PROCEDURE UNLOAD INSERT FROM CRYOSTAT

15 Prototype 4.2 K test facility of MCS and MCDO magnets at RRCAT Capacity 3 magnet/ 2days

16 4.2 K Cryogenic test station 2 Cryostats, 3 Inserts Testing Capacity > 100 Magnets/month LHe -200 Lit for 12 Magnets

17 TESTING SETUP He BYPASS LINE FIG-1 GAS BAG RECOVERY COMPRESSOR TO GAS BANK GHe RECOVERY LINE HEADER He TRANSFER LINE (72 SIGNALS) VENT TO ATMOSPHERE(GN ) 2 TMP GHe RECOVERY LINE QUENCH DETECTION SYSTEM HELIUM LEVEL INDICATOR TMP DATA AQUISITION PC FFL He GAS CYL. LHe DEWAR 100 LITRES. 950 POWER SUPPLY 1200A / 3V PENNING GAUGE TEMPERATURE INDICATOR FFL (INSERT HOLDING 6 Sc MAGNETS) PIT 940 Sc MAGNETS PIT CRYOSTAT Ø 350 SCHEMATIC LAYOUT OF CRYOGENIC TEST FACILITY OF Sc CORRECTOR MAGNETS AT 4.2K

18 Fig: 2 Vertical section of cryostat with instrumentatiion and wiring scheme ELECTRICAL WIRING SCHEME FOR TEST CRYOSTAT WITH RELATED INSTRUMENTATION TESTING OF Sc CORRECTOR MAGNET

19 Magnet Insert

20 Improving productivity Reduce helium boil off by minimizing Heat input through different sources 1. Improved sc-switch (by reducing the required power input) 2. Series testing (eliminating more current leads as needed in parallel testing)

21 SC-Switch Conservative Optimsed Magnets on the insert with SC switch for training & CR measurement Heater capacity is reduced from 18w to 5w (72 %). Volume of switch is reduced from 594cc to 75cc(87%). Sc switch inside bore of the magnet there by saving space for magnet positioning.

22 Increasing productivity of Cryogenic testing by series testing 7-current leads For Testing of 6 magnet 3 current leads for Testing of 12 magnets Conduction heat reduced by 57 %

23 Cryogenic test results A Typical quench record

24 HOTSPOT TEMPERATURE ESTIMATION Hot spot temp S Tmax 2 To C( T) dt ρ( T) = + t0 I( t) 2 dt T[k] MIITS [A2s] 0 T 2 T 4 T 6 T 8 T 10 T ka 2 Sec 2T Hot spot temp < 100 K

25 Typical Training & Retraining test result at 4.2 K Current (A) Training Retraining I Nominal P1 P2 P3 P4 P5 P6 Quench No.

26 MCS magnets assembled on 1.8 K test rig for cold tests at CERN

27 Training & Retraining of MCS at 4.2 K & 1.9 K at CERN

28 Contact Resistance Measurement of SC magnet Magnet is put in to persistent mode Current ( hall voltage) decay monitored Thermal budget/magnet < 10 mw At I Nom = 550 A CR < 30 n Ω Per joint < 4 nω

29 Qualification of ultrasonic welding by measurement of Contact resistance at 4.2 K Close loop Ultrasonic welded joint Inducing the current using heater Measuring decay current thru voltage signal of hall probe which is a function of loop resistance

30 Ultrasonic welding machine Very low contact resistance <4 nω per joint TYP

31 Cryogenic testing at 4.2 K 12 Behaviorof MCD in Contact Resistance 10 No of Magnets variation in CR 16 Behavior of MCO in Contact Resistance 14 No of Magnets MCO variation in CR

32 Thanks for your kind attention Successful completion of the supply 1146 MCS & 636 MCDO Contributions from SC Tech lab team magnet division & other divisions of RRCAT 32