Closed-Cycle Cooler experience

[fhh at nofs.navy.mil]

At Flagstaff we have run one CCD with Closed-Cycle Cooler (CCC) to the death
of the cooler, and have experimented with a second cooler.

The first system used a cooler from Cryodynamics; the company is now out of
business or we would gladly have bought a replacement unit.  The cooler was
NOT Sterling cycle, did use Helium for its working fluid, used a rotary motor
with bevel gears to turn cranks to power the pisotns of compressor and
regenerator.  Including two brushless-DC fans for the heatsinks, the cooler
(housed in a package that mimics an LN2 dewar) consumed 22W and had no trouble
taking a Cassini CCD to -90 to -115 C.  Life of the unit rant to something
near 2200 hours estimated.

The experimental unit is a small Sterling-cycle dual-linear drive CCC from
Hughes.  An external drive electronics box feeds the sealed compressor unit
with opposed synchronized linear-drive pistons, so vibration is minimal.
However, the (nominal) square-wave piston drive radiates from the compressor
(electrostatically for sure, electromagnetically possibly) and was found to
invade the CCD electronics with spikes from the edges of the square waves
equivalent to many tens of electrons equivalent signal.  Since that initial
test this CCC has been put on the shelf until its priority comes up in the
queue again.  Power consumption for this unit ia also around 20 Watts or so.

If memory serves me, a talk at the recent San Jose SPIE conference mentioned
in passing the retrofit of a CCC into a package nominally shaped as the LN2
dewar being used; might this have been Satoshi Miyazawa's talk from U of
Hawaii?  Gerry, are you out there to set me straight?

Cheers,

Fred Harris
US Naval Observatory Flagstaff Station