Sep 8 14:38:35 2000 To: jdotson@belmont.astro.nwu.edu Subject: questions Jessie: You have to heat the charcoal to 30 K to get the He-3 off of it. The other question I found to be rather challenging. But after a half-hour of studying the books on your desk, this is what I have come up with: All gasses that are not too near their 'critical points' or 'triple points' - behave pretty much like ideal gasses, so the specific heat is calculable. For example, according to your book by Keeler, the specific heat (constant volume) of He-4 at temps of 10-50 K and pressures that vary from 1 atm to several orders of magnitude greater is almost constant and equal to what theory predicts for all monatomic gases: 3 J/g So I think that He-3 would be the same. To calculate heat load on pumped pot you also need latent heat of He-3 which is 8 J/g. Presumably, we want to have a strong thermal link to 4K somewhere along the bellows that runs between the charcoal pump and the pumped pot. This way the pumped pot will have to cool the He-3 gas from 4 K down to liquid, and not from 20 K down to liquid. Hope this info helps. I'm going to get back to the final touches on Sgr B2 now. Erik has the a/d reading using his basic program. cheers, Giles