Issues related to the Vector Fridge at the moment

Sorb Temp readout on Ch0

Ch0 may not be accurate...

Even after the sorb heater is turned on and set to 35-40mA, the temperature on Ch0 does not go up as it should...but stays at ~4K.

We know the sorb heater is working because the IVC pressure goes up when the heater current is turned on.

Also, probing the Fischer shows that the Resistor is working.

Grounding Issues

The cryostat is not isolated from the gas cabinet as its supposed to be...
  • Plugging in the 7-pin Fischer for the heaters grounds the cryostat
  • The Big Fridge line is not isolated fully from the cabinet, and the rubber insulation is actually 500 Ohms
  • The cabinet is also being grounded through the USB connection to the AVS47 computer interface (as well as being grounded through its own mains connection)

Vibration Issues

With the current probe design, vibrations from the room are picked up by the probe.

This could cause problems if the sample is moving within the field

Also, the sample may be picking up electrical noise due to vibrations which show up in sensitive measurements. eg. random jumps in resistance in SdH traces...

Magnet Issues

  • When sweeping the magnet, the shunt resistor has to be measured as well to get an accurate value of the field around
  • Hysteresis problems!

Other Issues

  • When condensing mixture, the program automatically turns the mixture compressor off as soon as the dump is empty without giving the fridge time to stabilise, so it crashes unless the compressor is manually turned back on quickly.

Access Control

Previously the default template was set up so that all pages were visible by the whole world, and we relied upon authors to use access control to limit access to sensitive pages. That hasn't worked, so now pages are by default only visible to QED group members. Delete the following line if this page is meant to be visible by the whole world. (commented out - visible to world * Set ALLOWTOPICVIEW = QedGroup)


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Topic revision: r3 - 30 May 2013, AlexHamilton
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