Cryostat
The two upGREAT cryostats are built by Cryovac low temperature technologies Inc. and integrate closed-cycle coolers, which are custom modified Pulse Tube coolers from transMIT in Giessen, Germany, type PTD-406.
These pulse tube coolers are suitable for this project as they can operate with ± 45 º tilt angles. They incorporate additional small Helium pot (200 cm3), which serves two main purposes:
- It damps the temperature oscillations from the cooler by a factor of ~15.
- It allows keeping the 2nd stage cold when switching off the compressor for long periods (up to 60 minutes). Such situations are necessary during operations onboard SOFIA, especially during the take-off period, as the acceleration and tilt angles of the airplane during that phase would pose a risk on the compressors lubrication, therefore requiring to switch off the compressors.
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LFA cryostat |
HFA cryostat |
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Cryostat |
Cryovac sn-1 |
Cryovac sn-2 |
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Pulse tube |
PTD-406 |
PTD-406 |
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Compressor |
Sumitomo CSA-71A |
Sumitomo CNA-31C |
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Compressor power consumption with 50 Hz supply |
6.5 kW |
3.4 kW |
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Cooling power at 4.2 K |
0.84 W |
0.53 W |
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Tilting impact on cooling power at 4.2 K |
10 % degradation |
10 % degradation |
Section view from one of the upGREAT cryostats.
Custom modified Pulse Tube with an additional Helium pot.