X-Message-Number: 11019 From: Date: Sun, 3 Jan 1999 10:23:33 EST Subject: higher temp cryostats Thomas Donaldson has asked for renewed discussion of cryostats operating at higher temperatures than that of liquid nitrogen; he is uneasy about systems depending on mechanical refrigeration. It might be possible to get mechanical refrigeration systems with sufficient reliability or redundancy, and some have been discussed years ago. However, Cryonics Institute has a tentative design for a passive cryostat, using liquid nitrogen but nevertheless allowing the storage chamber to maintain any desired higher temperature. The design isn't secret, and I have outlined it before. (None of our work is secret.) Basically it just uses four concentric cylinders instead of two. The inmost cylinder holds the liquid nitrogen. The first annular space holds insulation. The second annular space is the storage chamber, large enough for several patients. The third annular space again holds insulation. The storage chamber is lined with heat conducting material (maybe copper or aluminum) , to maintain a reasonably constant temperature over the height of the chamber. The thicknesses of the two insulation layers are adjusted to maintain the desired temperature in the storage chamber and to minimize nitrogen boiloff. Variations could use cold nitrogen vented from the liquid to recirculate through part of the system, or around it. Compared to the "cold room" discussed elsewhere, there would be both certain obvious advantages and disadvantages. Capital cost would be greater than for LN2 temperature storage, but nitrogen use would be reduced. The main advantage, of course, would be the biological result, if the vitrification work proves out. Obviously, feasiblity/desirability will depend on the results of actual tests. This project will be activated at CI at a time that seems appropriate to us. Robert Ettinger Cryonics Institute Immortalist Society http://www.cryonics.org Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=11019