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LQ Test and Future Plans Giorgio Ambrosio, Guram Chlachidize Fermilab

LQ Test and Future Plans Giorgio Ambrosio, Guram Chlachidize Fermilab. BNL - FNAL - LBNL - SLAC. LARP Collaboration Meeting 13 Port Jefferson Nov. 4-6, 2009. Long Quadrupole. Main Features: Aperture: 90 mm magnet length: 3.7 m Target: Gradient: 200+ T/m Goal:

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LQ Test and Future Plans Giorgio Ambrosio, Guram Chlachidize Fermilab

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  1. LQ Test and Future PlansGiorgio Ambrosio, Guram ChlachidizeFermilab BNL - FNAL - LBNL - SLAC LARP Collaboration Meeting 13 Port Jefferson Nov. 4-6, 2009

  2. Long Quadrupole Main Features: Aperture: 90 mm magnet length: 3.7 m Target: Gradient: 200+ T/m Goal: Demonstrate Nb3Sn magnet scale up: Long shell-type coils Long shell-based structure (bladder & keys) 1st Long Quad test by the end of 2009 2nd Long Quad test in Spring 2010 LQ Design Report available online at: https://plone4.fnal.gov/P1/USLARP/MagnetRD/longquad/LQ_DR.pdf G. Ambrosio - Long Quadrupole

  3. J in copper = 2900 A/mm2 at 13.9 kA (4.3 K SSL) Test Preparation • Quench Detection System with Adaptive Thresholds • To allow using low threshold at high current avoiding trips due to voltage spikes at low current • Both DQD and AQD • Symmetric Coil Grounding • To reduce peak coil-ground voltage • LQ needs larger dump resistance than TQ magnets (60 vs 30 mOhm) • Reconfiguration of the Magnet Protection System • Additional Heater-Firing-Units for all LQ heaters (16) • Modified Strain Gauge Readout System • To reduce noise and sampling time • All new systems tested all together two weeks ago • Upgrades passed LQS01 Test Readiness Review G. Ambrosio - Long Quadrupole

  4. LQS01 Status • LQS01 is connected to the VMTF top-head • Electrical check-out is in progress • Cool down start: this weekend or early next week LARP CM13 – BNL – Nov. 4-6, 2009

  5. Test GOALS - I • Achieve target gradient 200 T/m • Understand limiting coil/section  Cause? (repairs, stress, …) • Compare gradient at 4.5K plateau with target • Compare gradient at 4.5K plateau with TQS02-series • Understand training • Are training quenches concentrated in a coil/section?  Coil design, fabrication; magnet pre-stress, assembly… • Compare training at 4.5K with TQS02a • Understand if changing one coil could improve “significantly” performance • By looking at plateau q. + training q. + Ramp-Rate study G. Ambrosio - Long Quadrupole LARP CM13 – BNL – Nov. 4-6, 2009

  6. Test GOALS - II • Understand if limitation is due to mechanics and/or coils • By temperature dependence study • 3K should be enough, and may be even better based on TQS02a/c • Memory after thermal cycle • Warm up, cool down and retraining at 4.5K • Understand behavior at 1.9K • Erratic or plateau quenches? Max quench current? • Compare with TQS02 series • Effects of bubbles on IL quench heater insulation? • Could cause coil-heater shorts! • Could reduce the number of usable protection heaters G. Ambrosio - Long Quadrupole LARP CM13 – BNL – Nov. 4-6, 2009

  7. 1.9K Test • “Bubbles” are a possible cause for coil-heater shorts • Electric arc? Note: we never had heaters on inner layer

  8. LQS01 Test Plan - I Room temperature preparation and cool down (10 days) • Magnetic measurements (z-scan) at VMTF 1st Thermal Cycle (10 days) Test at 4.5 K • Cold electrical checkout • Magnetic measurements • Quench training • Ramp rate study Cool down to 3 K • Quench Training • Magnetic measurements • Ramp rate study • Temperature dependence study Warm up to 4.5 K • Verify quench plateau at 4.5 K G. Ambrosio - Long Quadrupole

  9. LQS01 Test Plan - II Warm up to 300 K (4 days) • RRR measurements Cool down (4 days) 2nd Cold Test (10 days) Test at 4.5 K • Quench training  Memory Cool down to 1.9 K • Verify operation of protection heaters • To avoid possible damage after first few quenches we will do hi-pot (coil-heaters) and low current trips to verify proper operation of heaters • Quench Training • Magnetic measurements • Ramp rate study • Temperature dependence study G. Ambrosio - Long Quadrupole LARP CM13 – BNL – Nov. 4-6, 2009

  10. LQS01 Test Plan - III Warm up to 4.5 K • Verify quench plateau • Protection heater study • Spot heater study Warm up to room temperature (6 days) • Magnetic measurements (z-scan, use warm-finger of full length) G. Ambrosio - Long Quadrupole LARP CM13 – BNL – Nov. 4-6, 2009

  11. Present LQ FY10 plan Notes: • Coils #14 & #15 start after LQS01 feedback • Coil #13 may have delays because of conflict with HQ coils fabrication • Plan for success with budget = $1.4 M • Need contingency money in case of “problems” G. Ambrosio - Long Quadrupole LARP CM13 – BNL – Nov. 4-6, 2009

  12. LQS01 Test Scenarios Need analysis to understand cause of limitation May need 4 new coils (2 out of contingency) Need LQS02 and 3rd test  LQS02 (4 new coils) or LQS01b (1 or 2 new coils)  LQS01b (1 or 2 new coils), may need 3rd test 13 • Successful (G >= 200 T/m) • Limited (G < 200 T/m) by one or two coils • There is a flaw in all LQ coils design and/or fabrication technology • All coils are damaged during cooldown or test mechanics or quench protection failure, excessive pre-load, … G. Ambrosio – Long Quadrupole LARP CM13 – BNL – Nov. 4-6, 2009

  13. Conclusions • The test of the first Nb3Sn Long Quadrupole (LQS01) is starting • We planned the test in order to obtain as much information as possible • The present LQ FY10 plan is based on success • May need to use contingency in case of limited performance G. Ambrosio - Long Quadrupole

  14. Addendum

  15. Appendix G. Ambrosio - Long Quadrupole

  16. Test Preparation: Subsystem upgrades • Symmetric coil grounding • Strain Gauge Readout System • Reconfiguration of the Magnet Protection System • Quench Detection System with Adaptive Thresholds

  17. Symmetric Coil Grounding • The VMTF power system bus is grounded at one point to constrain voltage to ground and to detect electrical fault to ground of the coil • Old grounding was asymmetric - power system was grounded at the negative current bus via a 25 Ohm current limiting resistor • Started this summer symmetric coil grounding was implemented with 100 Ohm current limiting resistor • Peak coil to ground voltage for LQS01 test is reduced from ~900 V to ~450 V for 60 mΩ dump resistor 100 Ω 100 Ω Magnet PS 100 Ω 25 Ω

  18. Symmetric Coil Grounding • Maximum ground current through the fault also is reduced from ~40 A to ~ 6 A • Now equally sensitive to ground faults at positive or negative leads • We have more predictable voltage and current profiles after the quench • Symmetric coil grounding was tested for TQC02a, TQC02b and TQM02 magnets, permanently implemented in May 2009 • Special test performed with a 30 kA top plate to check symmetric grounding at higher currents (up to ~ 28.5 kA) • Passed safety and technical reviews at FNAL

  19. Test Preparation • Symmetric coil grounding • Strain Gauge Readout System • Reconfiguration of the Magnet Protection System • Quench Detection System with Adaptive Thresholds

  20. Strain Gauge System • LQSD test showed that FNAL SG system at the beginning had a much worse resolution wrt the LBL portable system • All SG in LQS are connected into a full-bridge circuit: one half-bridge used for the active gauges and the other for the T-compensator gauges • Dealing with very low voltage signals: FNAL SG system was able to provide max. 1.2 mA current against 5.0 mA in the LBL system

  21. Strain Gauge System Minor modifications improved FNAL SG system resolution: • One single SG slow scan replaced with 2 scans running in parallel - the maximum current increased to 1.5 A, at the same time scan period reduced • Voltage range in DMM HP-3458A was reduced from 10 V to 1 V - resolution increased which is important when reading very low voltage signals • Number of integration cycles in DMM increased

  22. Strain Gauge System improvements • Now running 4 SG scans in parallel - each equipped with an individual 8.5 digit DMM HP-3458A. We can read 64 SG in total. All DMM were recently calibrated • New 4-channel current source was built for the SG system • Magnet current signals from the Holec transductor are divided to allow the same 1 V readout range in DMM for both the SG and current signals • Up to 2 mA is provided to each SG scan

  23. Strain Gauge System improvements • Sampling rate is increased. Scan period is ~ 2-3 s for the SG slow scans and ~ 5 s for the RTD slow scan, which combined gives ~ 6-7 s of time period for the fast scan scribe • Modified SG system tested for TQM03 mirror magnet • LQS01 SG readout will be performed using both LBL and FNAL systems: • LBL system is used for measurements before and after the cold test, when magnet is in a horizontal or vertical position • FNAL system will be used for measurements during the cold test • Need consistent readings from these 2 systems

  24. Strain Gauge System improvements • Reference bridge was built at Fermilab to verify if FNAL and LBL readings are consistent • Vishay 350-Ohm precision resistors used • Platinum RTD installed for follow temperature change • Bridge first measured using a calibrated system • Reference bridge already used for LQSD: good agreement found between the LBL and FNAL systems

  25. Test Preparation • Symmetric coil grounding • Strain Gauge Readout System • Reconfiguration of the Magnet Protection System • Quench Detection System with Adaptive Thresholds

  26. Magnet Protection System • Each coil of LQS01 magnet is equipped with 4 protection heaters and 1 spot heater • Protection heaters are on both the outer and inner coil layers • All heaters of the same coil layer and side (LE or RE) will be connected in parallel

  27. Magnet Protection System • Heaters on the outer layer RE for both coil 7 and 9 will not be connected • Coils 7 and 9 are placed against each other in magnet • Dummy loads will be connected or different capacitance will be set for HFU with less number of heaters • Coil 7 heater on the outer layer LE will be connected only if cold hipot is successful • Polarity of heaters on outer and inner layers will be opposite • LE and RE heaters will be powered with opposite polarity _ coil 8 coil 9 + + _ coil 7 coil 6 Lead End View

  28. Magnet Protection System • New heater design, application to inner coil surface, operation at a high voltages and currents (300-400 V, ~250 A) suggested to test heater and HFU performance • LQ practice coil #5 heaters were tested at a liquid nitrogen temperature at Fermilab • HFUs successfully survived currents above 250 A (up to 450 V) at a capacitance of 19.2 mF and time constant ~ 30 ms • No difference was observed in performance of the heaters on the inner and outer coils. IB3 - Fermilab/TD

  29. Magnet Protection System • Existed magnet protection system was modified to accommodate large number of heaters in LQS01 • Re-designed magnet protection system includes 4 heater firing units (HFU) for protection heaters and 2 HFUs for spot heaters • Heater distribution box was re-designed to accommodate up to 8 strip heaters in total • We need only 4 for LQS01 Summing module

  30. Magnet Protection System • Summing module was designed to switch the magnet protection system from operation with 4 HFUs to operation with 2 HFUs. Usually 2 HFUs are used when testing magnets with a smaller number of heaters • Summing module consists of 3 channels: 2 for protection heaters and one for spot heaters. Each channel operates a pair of HFUs • All logic signals for QLM are obtained by adding the corresponding signals from both HFUs in each pair • Two HFUs in each pair also should have same bank capacitances

  31. Magnet Protection System • Currently all elements of re-designed magnet protection system are in place, spare HFUs are available • New system was tested with dummy loads for both 4-HFU and 2-HFU operation. Operational logic for different failure modes also was tested • Final test will be done for TQM03 magnet

  32. Test Preparation • Symmetric coil grounding • Strain Gauge Readout System • Reconfiguration of the Magnet Protection System • Quench Detection System with Adaptive Thresholds

  33. Quench Detection System with Adaptive Thresholds • Goal is to apply current dependent quench detection thresholds for half-coil signals • High threshold at low currents and low threshold at high currents will help to avoid low current trips due to voltage spikes observed in Nb3Sn magnets and keep MIITs low during quench training • Adaptive thresholds will be set by FPGA based quench management (QM) system • successfully used to test HINS solenoids at FNAL • FPGA code developed to set thresholds for 10 different current ranges. Threshold at 0 current will apply if current reading fails

  34. Quench Detection System with Adaptive Thresholds • Currently FPGA system works in addition to the VME QLM • FPGA signal is connected to VME AQD coils in “OR” mode • PXI data Loggers are triggered back from the VME system • FPGA system sends signal to the VME “change of status” module • In future both VME and FPGA systems will work in parallel, and FPGA QLM will be fully functional

  35. Quench Detection System with Adaptive Thresholds • VME module for AQD half-coils also was modified to set a current dependent threshold. This module was tested for TQM02 magnet • Most elements of the FPGA based QM system were tested for TQM03 magnet • Final checkout with all FPGA components will be done in next 2 weeks for TQM03 magnet

  36. Data analysis and storing • Quench data analysis will be done at Fermlab • Test summary will be released as a TD note • SG data collected with the LBL system temporarily are placed at a public area: http://tdserver1.fnal.gov/lqs01/ • SG data from FNAL system will be processed on-line to get strains • All necessary scripts are in place • Cron-jobs will run to upload voltage and strain data to the data storage area hourly • WebDat - new database for storing test data at Fermilab MTF • Password protected area:https://tiweb.fnal.gov/WebDat/ • FNAL SG data will be saved in WebDat area • SG data from the LBL system also will be moved to WebDat

  37. Cool Down • Temperature gradient along the magnet to be limited during the cool down • For LQSD the initial 50 K constraint on temperature gradient resulted in very slow cool down: after 15 hrs magnet top still was at ~300 K • Estimated cool down time for ΔT=150 K is 48 hrs. Since cryo-operator is involved cool down will take ~ 4 calendar days • LQS01 warm up also should take ~ 4 days to reach 300 K • LQSD was warmed up with GN2 in ~ 6 days LQSD cool down Magnet top Magnet bottom ΔT=50 K ΔT=150 K

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