Wednesday, 23 June 2010
My CCD imaging camera is a cooled Yankee Robotics Trifid 2 6303. Last year YR ceased trading so I was left with an unsupported camera. What was worse was that the camera's cold chamber was leaking, leading to moisture ingress and frosting of the CCD. With no hope of service I was faced with either effecting the re-gassing process myself or possibly having the 6303 chip rehoused in a supported camera. I consulted with YR who advised how to remove the cold chamber window - Thanks Daniel! This was a laborious process of hacking away at the bitumastic gloop that sealed in the window; a bit like putty. This got a bit hairy with the window removed. The chip has no coverslip so anything dropping on the CCD active area spelled disaster. Having gone through the process the thought of doing this all over again in a couple of years was not appealing. Other cameras use ports to purge and fill the chamber with dry air or Argon. I got thinking, and came up with a plan which involved drilling through the wall of the cold chamber and adding threaded access ports. I had to be careful not to get any swarf on the CCD, but it actually went quite well. I used 1/8" BSP fittings that are used for air brush lines to provide an sealeable means of maintaining the environment within the cold chamber. The purging gas is filtered by an inline molecular sieve air filter. Again this was sourced from an Airbrush supply website.
I found through experimentation that purging the chamber with Argon prevented frosting, but the gas got damp or escaped, requiring regular re-gassing. Not a problem, but I wanted something more consistent and less labour intensive. Another stripdown revealed the window seal to be inefficient. Fortunately I had kept the original putty, so i bit the bullet and sealed the window with a more permanent solution. I also devised a means of drying the gas in the cold chamber with a silica gel canister fashioned out of a tiny jam jar, another airbrush fitting and a non-return valve. So far this system is working satisfactorily.
Eventually I will get the chip moved into a new casing from an established vendor. Though this will cost there will be advantages such as air cooling and improved readout noise. At least I'm now getting some use out of the camera, so I'm happy.