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CM-26 Cooler and Lead Te st 1 Tests of a PT415 Cooler with HTS Leads in the Drop-in Mode Michael A. Green Lawrence Berkeley Laboratory, Berkeley CA 94720, USA
CM-26 Cooler and Lead Test 1
Tests of a PT415 Cooler withHTS Leads in the Drop-in Mode
Michael A. GreenLawrence Berkeley Laboratory, Berkeley CA 94720, USA
CM-26 Cooler and Lead Test 2
The Purpose of Cooler and Lead Test
• The cooler performance was to be measured as a function of the first stage heat load and the second stage heat load.
• Re-condensation was tested. Without re-condensation there is no cooling of the MICE magnets.
• The heat leak down the copper leads was measured at zero current and at 275 A. The lead performance was measured for two different lead IL/A’s.
• The temperature drops across the cooler drop-in joint, the intercepts for heat the room temperature leads and the copper between the leads and the cooler were measured.
• The test provided a measurement of the system time constant as a response to changes.
CM-26 Cooler and Lead Test 3
First PT-415 Drop-in Cooler Test Photos
1st Stage heater and Tapered Plate
2nd Stage heater and CondenserPT-415 Drop-in Cooler
CM-26 Cooler and Lead Test 4
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Schematic Diagram of the Lead Test
CM-26 Cooler and Lead Test 5
Lead Test Assembly Photos
CM-26 Cooler and Lead Test 6
Photos of the Lead Test with a PT415 Cooler
CM-26 Cooler and Lead Test 7
1.61.41.21.00.80.60.40.20.0
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.6
4.8
Dewar Pressure (bar)
Saturation Temperature (K)
y = 2.1978 + 4.0759x - 3.5897x^2 + 1.9306x^3 - 0.41073x^4 R^2 = 1.000
The saturation temperature of the helium in the tank can be determined by the tank pressure. The temperature sensor on the tank is not very accurate so the tank sensor was calibrated using the temperature calculated from the tank pressure.
T = 2.1978 + 4.0759 P-3.5897 P2 + 1.9306 P3 -0.41073 P4
T is given in K.P is given in bar
Helium Temperature is determined by Pressure
CM-26 Cooler and Lead Test 8
5.04.84.64.44.24.03.8
3.4
3.6
3.8
4.0
4.2
4.4
4.6
Measured Temperature T1 (K)
Actual Temperature T1 (K)
y = - 1.1045 + 1.4738x - 7.3300e-2x^2 R^2 = 0.964
Calibration of the Tank Temperature Sensor
€
Tact = −1.1045+1.4738Tmeas − 0.0733Tmeas2
CM-26 Cooler and Lead Test 9
706560555045403530
2.5
3.0
3.5
4.0
4.5
5.0
5.5
T2 (Q1=0)
T2 (Q1=21W)
T2 (Q1=42W)
T2 (Q1=63W)
T2 (Q1=84W)
Lead 1a
Lead 1b
First Stage Temperature (K)
Second Stage Temperature (K)
Q2 = 0
Q2 = 0.5 W
Q2 = 1.0 W
Q2 = 1.5 W
Q2 = 2.0 W
Q2 = 2.5 W
Q2 = 3.0 W
Lead 1a
I = 0
1= 275 A
I = 275 A + 20 W
Lead 1b
I = 0
I = 275 A
I = 275 A + 30 W
Lead 1a
IL/A = 5.3x10^6
Lead 1b
IL/A = 3.1x10^6
Cooler Performance with Two IL/A Leads
Not in Equilibrium
CM-26 Cooler and Lead Test 10
706560555045403530
2.5
3.0
3.5
4.0
4.5
5.0
5.5
T2 (Q1=0)
T2 (Q1=21W)
T2 (Q1=42W)
T2 (Q1=63W)
T2 (Q1=84W)
Lead 1b
Lead 2
Lead 3
Lead 4
First Stage Temperature (K)
Second Stage Temperature (K)
Q2 = 0 W
Q2 = 1.0 W
Q2 = 2.0 W
Q2 = 3.0 W
Tests of 4 Identical Leads, an Example of the Test not being in Equilibrium
For T2, the time to come equilibrium is ~10 hours.For T1, the time to come equilibrium is ~1.5 hours.
CM-26 Cooler and Lead Test 11
Observations Concerning the Cooler Tests• The copper leads used in the previous magnet 2 had a heat
leak that was too high. The IL/A for these leads was 5.3x106 A m-1. Is was clear that this IL/A was too large. The second leads tested had an IL/A = 3.1x106 A m-1.
• The ICST calculations for IL/A suggest that the copper lead IL/A should be 3x106 A m-1 for copper leads with an RRR = 10. The RRR of the cable used for the leads was unknown. IL/A is an important design feature for the leads. It appears that an IL/A of 3 x 106 A m-1 is about right.
• The time to come to equilibrium (four time constants) is long for the experiment (~10 hrs). The magnet equilibrium time constant is proportional to the helium mass and inversely proportional to the number of coolers and the cooling power per cooler at 4.2 K.
CM-26 Cooler and Lead Test 12
Cooler Test Observations continued
• From the operating diagram it is clear that the cooler first stage temperature should not be greater than 45 K. This means that the first stage heat load should be less than 50 W.
• The HTS lead lead current is limited by temperature and magnetic field. The temperature drop between the top of the HTS leads and the cooler first stage is very important. The T in the drop-in joint was 1 to 2 K. The T from the leads to the copper plate was about 1 K. In the experiment, the copper plate that carried heat from the lead heat intercept to the cooler had the largest T.
• The copper plates for all of the MICE magnets should be thicker and the distance from the leads to the coolers must be minimized.
