Maker Stuff

Selected things we’ve created:

Sub-THz Mirror/Polarizers for simple pass-through Fabry-Pérot Cavity :

Until now, conventional confocal Fabry-Pérot cavities in the sub-THz region have not existed because of a the lack of dichroic mirrors. Our solution was to create concave wire-grid polarizers that act like dichroic mirrors. The link above will take you to a poster on the setup and resulting signals which demonstrate a cavity Q on the order of 100,000 at 75 GHz. This is despite the visible flaws in the mirrors, since the defects are smaller than the wavelength.

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Low Cost Helium Recycling:

Helium is becoming ever more expensive. It is a non-renewable resource that is literally evaporating into outer space. Normal recycling efforts require expressive compressors to recompress the recaptured helium back up to original tank pressure. If your application does not require high pressure helium above 120 psi you can simply use a $250 oil-free dental compressor to collect the helium into 100 liter propane tanks you can buy at your local hardware store. The larger tank volume here offsets the lower pressure. Backstory: In our lab we have a liquid helium cooled closed cycle cryostat that cools our mm-wave detector down below 4 Kelvin. In order to isolate the detector from vibrations we purchased a vibration-free cryostat from ColdEdge Technologies which uses normal helium gas (not closed cycle) to transfer heat from the detector chip to the cryostat cold head. This helium collects/pools in the heat exchanger and builds up. It simply gets vented away if there is a power failure or other problem (all too often). We built this system to monitor the pressures and control the cryostat compressor and then recollect any helium when there is a system failure. Two propane regulators (also from the hardware store) deliver the helium at .5 psi back to the cryostat when needed. We have not published this but if you want advise we are happy to share with you what we have done using an Arduino to monitor pressures and other fault conditions then controlled a pneumatic valve, and the cryostat and dental compressors to backfill the large propane storage tanks.

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