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

Test Program and Results

Guram Chlachidze for

FNAL-CERN CollaborationSeptember 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 Collaboration 2

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


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


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


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


Quench Performance


1.9 K4.5 K

TC-1

4.5 K 1.9 K

TC-2

2.6-4.5 K

Unscheduled thermal cycle at the very end of the test

SG data: cool-down


Pole gauges in coils 2 (top) & 3 (bottom)

SG data: cool-down


LE Bullets RE Bullets

LE and RE Skin

Strain gauges on shell (skin)and bullets

Ramp rate dependence


SSL:4.6 K 13 kA1.9 K 15 kA

Possible conductor damage in the mid-plane blockmay 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


2b2_b1 splice segment picks up asignal 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

2b2_b1 x 10

Quench Locations


Coil-2/3 IL/OL MP: A2-A3, B2-B3

Coil-2/3 IL: A4-A5, A5-A6Coil-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 quenchAll 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 Collaboration

Test with DC powered heaters

• Instability test - reducing Jc 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

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


SSL

RRR measurement


Average RRR ~ 100 (lowest 80, highest 118)

Same segments in different coils have similar RRR

Coils with RRP 108/127 strandTQ coil 34: 185HQ coil 14: 80LQ coil 14 (RRP 114/127): 180

More tests: voltage spikes, quench propagation speed


Quench propagation speed was estimatedin 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

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


Experimentally verified for aPH induced quench at 8 kA with dump delayed for 120 msAfter 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/cm2, HFU voltage decay time 25 ms• PH-2L delay is large at low currents


PH-1L

PH-1L

PH-2L

PH-2L

Protection Heater Study (cont’d)


Peak power in heaters only 25 W/cm2

Compare to 50 W/cm2 in LQ magnets

Summary on PH 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 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


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 a2 and other even-ordered harmonics

– 180 degree phase shift between the probes– Absolute values are consistent – Currently under investigation


sign mismatch corrected

Impact of ramp rate


Impact of temperature


• 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


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 b3 minimum


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


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


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



Backup Slides

Name 32

SG data: cool-down in coil 2


Coil 2

SG data: cool-down in coil 3


Coil 3

Excitation SG data: Pole gauges


Excitation SG data: Coil gauges


Excitation SG data: Bullets


Documents

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