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Micro Stirling Mechanical Cryo-cooler teardown by Fraser

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MrSheep:
Hey Fraser,

Can you unscrew the screw on the side of the cryocooler that is used for filling the pressurized helium. Just curious to see what kind of screw/ seal they use. I believe the port is here circled in pink (see attached).

Thanks

Fraser:
Sadly not possible at the moment. The camera is rebuilt and buried in the spares donor store.
From memory, the Helium gas fill hole is nothing exciting. Just a flat sealing seat at the bottom of the threaded hole with a indium seal that is crushed by the flat faced threaded screw slug. No special seal recesses or strange sealing surface profiles. When it comes down to it, the is is just a flat faced machine screw crushing a ‘donut’ shaped seal against a sealing flange. The actual gas fill hole at the bottom of the threaded orifice is very small. Less than a mm in diameter.

Fraser

MrSheep:
Ah yeah that is understandable. yeah I figure it was something like that. I am guessing it is something similar to this seal just with a smaller plug:
https://hydrogen.wsu.edu/2016/02/09/making-a-cryogenics-compatible-o-ring-seal/

Maybe one day when one of my rotory ones stop cooling. I'll do a tear down. I do have a few units with the Ricor K508 in them. To service them if I recall was around $5500. Not terrible considering the cameras that use the cooler cost a lot more. $50-100k. I think the FPA is probably the most expensive part in a cooled camera system.

I might disassemble my other Non-working Amber Radiance 1 cryocooler. It has a plastic screw over the actual fill port on the Hughes Cryocooler. This particular unit rattles (metallic sound) a little bit on startup but quiets down after a few minutes. I not entirely sure there is damage or it's just like that because of a lack of helium.

MrSheep:
Also do you have any idea what kind of solder they used on the housing and vacuum pinch off tube? I wonder if they used some kind of soldering iron rather than a torch that you would use when brazing copper pipes.

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