Test Program and Results Guram Chlachidze for FNAL-CERN Collaboration September 26-27, 2012 Outline Test program Quench Performance Quench Protection Magnetic Measurements Summary

MBHSP01 Test at VMTF MBHSP01 - the first 11T demonstrator dipole magnet was tested at Fermilab’s Vertical Magnet Test Facility (VMTF) in June-July 2012 VMTF was designed for testing magnets up to 4-m length and 0.6-m diameter at temperatures between 1.8 K and 4.6 K – 30 kA power system – 30 kA/1 kV DC rated dump resistor (15 mΩ – 120 mΩ) – Two 15 kA/1 kV DC rated solid-state dump switches 60-mΩ dump resistor was used for the stored energy extraction Guram Chlachidze, FNAL-CERN Collaboration2

MBHSP01 instrumentation Voltage tap system covers the inner and outer coil layers, pole turn, multi- turn and splice sections. There are 10 voltage taps on the inner layer and 9 voltage taps on the outer layer Guram Chlachidze, FNAL-CERN Collaboration3

Magnet instrumentation (cont’d) Each coil was equipped 2 pairs of protection heaters. Each pair covers 28% of the total coil surface 1-layer or 2-layer 5-mil (125 µm) Kapton insulation was placed between the heaters and the outer-layer coil block Guram Chlachidze, FNAL-CERN Collaboration4 PH-1L (1 layer) PH-2L (2 layers) PH-1L (1 layer) PH-2L (2 layers)

Magnet instrumentation (cont’d) 64 strain gauges (SG) were installed on shell, coils and bullets for monitoring mechanical strain and coil stresses during the magnet construction and testing 4 resistive temperature sensors (RTD) were mounted at top, middle and bottom of the magnet outer skin No quench antenna was available for this 60-mm aperture magnet Guram Chlachidze, FNAL-CERN Collaboration5

MBHSP01 Test at VMTF Cold test program included quench training, ramp rate dependence study, protection heater study and field quality measurements both at 4.5 K and 1.9 K Temperature dependence study, RRR and splice resistance measurements also are part of our standard test program. AC loss measurement was not included in the test program The original test program was modified due to limited magnet performance – Quench training at various ramp rates – Additional tests to investigate magnet stability – Field quality measurements at a maximum current of 6500 A – Heater study at a maximum of ~ 65% of SSL Long test with several interruptions Guram Chlachidze, FNAL-CERN Collaboration6

Quench Performance Guram Chlachidze, FNAL-CERN Collaboration7 1.9 K 4.5 K TC K 1.9 K TC K Unscheduled thermal cycle at the very end of the test

SG data: cool-down Guram Chlachidze, FNAL-CERN Collaboration8 Pole gauges in coils 2 (top) & 3 (bottom)

SG data: cool-down Guram Chlachidze, FNAL-CERN Collaboration9 LE BulletsRE Bullets LE and RE Skin Strain gauges on shell (skin) and bullets

Ramp rate dependence Guram Chlachidze, FNAL-CERN Collaboration10 SSL: 4.6 K13 kA 1.9 K15 kA Possible conductor damage in the mid-plane block may be reason for a limited magnet performance 10.4 T or 78% of SSL No quench when ramping down from 8 kA at a ramp rate of 120 A/s

Quench locations Guram Chlachidze, FNAL-CERN Collaboration11 2b2_b1 splice segment picks up a signal from the quenching 2b3_b2 Segment (mid-plane block) - checked for a PH induced quench Upper limit of b2_b1 splice resistance estimated as <2 nΩ Heater induced quench 2b2_b1 x 10

Quench Locations Guram Chlachidze, FNAL-CERN Collaboration12 Coil-2/3 IL/OL MP: A2-A3, B2-B3 Coil-2/3 IL: A4-A5, A5-A6 Coil-2/3 OL: B3-B4, B5-B6 Only few training quenches in pole turns

Holding quenches Ramp to a pre-set current at 20 A/s and hold this current until quench All holding quenches initiated in the mid-plane block of coil 2 OL (B2-B3) – Zero holding time is a regular quench at 4.5 K or 1.9 Reproducibility test, tests at different ramp rates were not done Guram Chlachidze, FNAL-CERN Collaboration13

Test with DC powered heaters Instability test - reducing J c in the mid-plane area Small DC current through the protection heaters – PH cover also multi-turn pole block No improvement in quench performance when DC current in PH is ON Guram Chlachidze, FNAL-CERN Collaboration Name 14

Temperature Dependence 50 A/s ramp rate in most quenches. All quenches at intermediate temperatures were initiated in the mid-plane block of coil 2 OL (B2-B3) Magnet showed temperature dependence of quench current, but exhibited degradation and instability Guram Chlachidze, FNAL-CERN Collaboration15 SSL

RRR measurement Guram Chlachidze, FNAL-CERN Collaboration16 Average RRR ~ 100 (lowest 80, highest 118) Same segments in different coils have similar RRR Coils with RRP 108/127 strand TQ coil 34: 185 HQ coil 14:80 LQ coil 14 (RRP 114/127): 180

More tests: voltage spikes, quench propagation speed Guram Chlachidze, FNAL-CERN Collaboration17 Quench propagation speed was estimated in ramp # 5 (Iq 9.4 kA) : ~27 m/s Voltage Spike Detection System captures half-coil signals at a sampling rate of 100 kHz

Summary on Quench Performance Magnet showed limited quench performance and reached only 10.4 T or 78% of SSL at 1.9 K. Magnet did not reach quench plateau Most quenches at low ramp rates, as well as holding quenches and quenches at intermediate temperatures were initiated in the mid-plane block of the outer-layer coil Only few training quenches occurred in the high field area at the very beginning of test at 4.5 K and 1.9 K Plan to have a quench antenna for a better quench localization Quench location, ramp rate and temperature dependences and additional tests indicate magnet degradation and related instability. Possible conductor damage in the mid-plane area (presentation by F. Nobrega) could be a reason for this degradation Guram Chlachidze, FNAL-CERN Collaboration Name 18

Protection Heater Study Heat transfer from the heater to the outer coil layer and then from the outer-layer to the inner-layer coil helps to spread and absorb the magnet stored energy Temperature profile in the magnet after 48 ms (left) and 96 ms (right) from the PH induced quench at a nominal current of 11.8 kA Guram Chlachidze, FNAL-CERN Collaboration19 Experimentally verified for a PH induced quench at 8 kA with dump delayed for 120 ms After 65 ms quench starts in the outer coil layer and after 150 ms - in the inner coil layer - More tests expected with next 11T prototypes

Protection Heater Study (cont’d) PH-1L and PH-2L are heaters with one and two layer Kapton insulation respectively PH peak power 25 W/cm 2, HFU voltage decay time 25 ms PH-2L delay is large at low currents Guram Chlachidze, FNAL-CERN Collaboration20 PH-1L PH-2L

Protection Heater Study (cont’d) Guram Chlachidze, FNAL-CERN Collaboration21 Peak power in heaters only 25 W/cm 2 Compare to 50 W/cm 2 in LQ magnets

Summary on PH study Guram Chlachidze, FNAL-CERN Collaboration22 Heat transfer from the PH to the outer layer coil and then to the inner layer coil was experimentally observed. This effect helps to spread and absorb magnet stored energy More tests will be done with next 11T prototypes Protection heaters with different insulation were tested both at 4.5 K and 1.9 K Protection heater with 2 layers of 5-mil (125 µm) Kapton insulation found less efficient than PH with 1 layer of Kapton insulation Heaters with 1 layer of Kapton insulation will be used in next magnet for protection and heater study

Magnetic measurements Warm and cold magnetic measurements were performed at VMTF with the magnet in a vertical position Fast rotating coil magnetic measurement system based on a digital signal processor (DSP) was used for the measurements 250 mm long and 25 mm diameter tangential probe, as well as printed- circuit board (PCB) based 26 mm long and 130-mm long probes were used for measurements – 25-cm tangential probe was used only at room temperature and for few “cold” measurements at 4.5 K. This probe was rejected after signals were found noisy Guram Chlachidze, FNAL-CERN Collaboration23

Magnetic measurements (cont’d) All harmonics are presented at a reference radius of 17 mm Data measured with the tangential probe and 130-mm PCB probe are consistent Sign inconsistency was found for a 2 and other even-ordered harmonics – 180 degree phase shift between the probes – Absolute values are consistent – Currently under investigation Guram Chlachidze, FNAL-CERN Collaboration24 sign mismatch corrected

Impact of ramp rate Guram Chlachidze, FNAL-CERN Collaboration25

Impact of temperature Guram Chlachidze, FNAL-CERN Collaboration26 Only tangential probe data available for comparison We see about 3% decrease in strand magnetization at 1.9 K - 7% increase expected from the simulation (see next presentation by Mikko Karppinen) Need to verify with PCB probes during the next test

Impact of reset current Guram Chlachidze, FNAL-CERN Collaboration27 20 A/s loops

Accelerator cycle measurements Only tangential probe data available Maximum current of cycle 6500 A Reset current 100 A, ramp rate 10 A/s Injection plateau at 760 A, dwell time 900 s No snap-back or decay was observed Injection plateau close to the b 3 minimum Guram Chlachidze, FNAL-CERN Collaboration28

Stair-step measurements 130-mm long PCB probe data Stair steps up and down from 1000 A to 6500 A Dwell time at flattop 120 s Guram Chlachidze, FNAL-CERN Collaboration29

Summary The first 11T demonstrator magnet was assembled and tested at Fermilab Magnet showed limited quench performance and reached only 10.4 T or 78 % of SSL at 1.9 K Most quenches at low ramp rates, all holding quenches and quenches at intermediate temperatures initiated in the mid-plane block of the outer coil layer Quench location, ramp rate and temperature dependence studies indicate magnet degradation and related instability. Possible conductor damage in the mid-plane area during fabrication could cause the observed degradation Protection heaters (PH) with different insulation thickness were tested Guram Chlachidze, FNAL-CERN Collaboration30

Summary (cont’d) PH with 2 layers of 5-mil (125 µm) Kapton insulation found not efficient, therefore PH with 1 layer of Kapton insulation will be used in next magnet for protection and heater study Heat transfer from the PH to the outer layer coil and then to the inner layer coil was experimentally observed. This effect helps to spread and absorb magnet stored energy – More tests to be done Magnetic measurements were performed with tangential probe and PCB based probes – Need to investigate source of noise in signals from the tangential probe – Need to understand source of 180 degree phase shift in data from the tangential and PCB probes Measurements at two different facilities (FNAL and CERN) would be very useful First demonstrator test experience will be used in test preparation and test of next 11T magnets Guram Chlachidze, FNAL-CERN Collaboration31

Backup Slides Guram Chlachidze, FNAL-CERN Collaboration Name 32

SG data: cool-down in coil 2 Guram Chlachidze, FNAL-CERN Collaboration33 Coil 2

SG data: cool-down in coil 3 Guram Chlachidze, FNAL-CERN Collaboration34 Coil 3

Excitation SG data: Pole gauges Guram Chlachidze, FNAL-CERN Collaboration35

Excitation SG data: Coil gauges Guram Chlachidze, FNAL-CERN Collaboration36

Excitation SG data: Bullets Guram Chlachidze, FNAL-CERN Collaboration37