Cooldowns
of IRCamera
Current Cooldown
- 17 July 2005, CTI compressor 4182 hours
Previous Cooldowns
Below is a plot of the temperature monitored at the chip and at the cold
head, during cooldown after the most recent
re-mounting of IRCAM to the Thirty inch telescope (August, 2004).
Original Cooldown curves, before first mounting
The chip has not been mounted but preliminary cooldowns have been made. The
cooldowns were fit by a VERY primitive
program that attempts to model the thermal properties of what is inside.
Cool10
Below is the cooldown of the chip holder only.
The model fit has the following:
- strap resistance 10K/W
- extra resistance 10k/W
- emissivity or around 0.1 for holder
The ultimate temperature is a pathetic 130 K!
I don't understand why the parasitic resistance is so high.
Cool12
I then wrapped the chip holder in MLI as well as the cooling strap. The
screws connecting the strap to the cold head were tightened.
The model fit has the following:
- strap resistance 10K/W
- extra resistance 13k/W
- emissivity or around 0.02 for holder
The emissivities seem to have decrease, but the parasitic resistance
went up? Also the true temperature deviates suddenly from the model. The
ultimate temperature is 104K which is better.
IRCam Index
Last updated Sep 20, 2000