This EXO sub-project was to build a fixture that could lift and roll the inner cryostat out of the outer cryostat inside clean room 1. The inner cryostat needed to be removed to change some stainless steel bolts that were too radioactive for the experiment, to replace some teflon support pads, and to clean the space between the inner and outer cryostats.

The inner cryostat weighs about three tons and needed to be supported securely inside the clean room where space is very tight and people would have to work around it. For cleanliness, it was decided that any structural elements inside the inner cryostat could only be stainless or aluminum. Outside the cryostat the structure could be A36 or A500 Grade B steel.

The photos come from the EXO E-log and were taken at Stanford by those involved in the operation. (I would love to give individual credit, but with the masks I can't recognize anybody! If you see yourself and want to be named here, send me an e-mail.)

Click on any of the thumbnails to get an enlarged view. You are welcome to download any of the images. If they are used for other than private viewing, credit to the EXO collaboration and Bartoszek Engineering would be appreciated.

The design is roughly based on the concept of the type of cherry picker that is used to remove engines from cars. This one had to carry a much greater load, have a short vertical stroke, and ride on a rail with vee-groove wheels so that the inner cryostat could be returned precisely to the same location inside the outer cryostat.

Assembling the Cherry Picker around (and inside) the cryostat

The cherry picker had to be designed with bolted joints separating the structure into pieces that could reasonably be manually handled, brought into the clean room and assembled with minimal help from the overhead crane. Someone had to climb inside the cryostat to tighten bolts that supported the inner cryostat from the arm of the cherry picker.

Rolling out the Inner Cryostat

Once everything was ready, the inner cryostat was rolled out of the outer and the cleaning and re-furbishing began. The insertion operation was the reverse of the extraction.

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