Check CCD Temperature

Type this command in MOP:

mt> cc 0 tcheck
CAMERA 0

LN2 TEMP
NOMINAL 77 K MEASURED 89 K

CCD TEMP
DAC SET AT 115 = -0.52 V = -90 C MEASURED -94 C


mt>


The "measured" temperatures are taken at the CryoTiger cold head (89 K in the above example) and at the the CCD (-94 C above). The temperatures are fairly stable, sitting within a few degrees of the above numbers. If the LN2 temp gets close to 100 K something is wrong or will soon go wrong. The cause should be investigated (call Jon Brinkmann).

The CCD will function normally and observing can continue so long as the CCD temperature remains equal too or cooler than -80 C. Because of the margin of safety built into the design, the CryoTiger temperature can vary widely, rising up to roughly 140 K, without affecting the CCD temperature at all.

The "cc" command sends the string "0 TCHECK" to the CCD controller. The PT is assigned CCD (camera) number 0, and the TCHECK command returns the CCD temperatures.

The "nominal" LN2 temp value of 77 K is for liquid nitrogen. The CryoTiger cold end doesn't get that cold so the measured temperature will always be somewhat warmer.

The CCD has a heater that keeps it at the right temperature. The DAC (digital to analog converter) setting controls the temperature setpoint, in this case -90 C. The heater isn't powerful enough to warm the CCD up to -90 C so it sits a few degrees below that most of the time. If the heater shuts off (for example, if you turn off the CCD controller box), the CCD temperature drops to something like -120 C.

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