From jdotson Sat Jul 13 15:15 CDT 1996 Date: Sat, 13 Jul 1996 15:15:14 -0500 From: jdotson (Jessie Dotson) To: novak@clark.phys.nwu.edu Subject: pumped pot work at yerkes 7/9-7/12 Cc: samuel@irastro.gsfc.nasa.gov Giles, Samuel and I installed a calibrated GRT on the pot and successfully cooled down the dewar. We came up with a crude test to look for plugs at both room temperature and at LN2 temperature. We pumped on the reservoir while applying a back pressure of helium to the capillary. We were able to confirm the line was open by briefly eliminating the back pressure and observing the decrease in the reservoir pressure. Hopefully we can develop this test further so that we can quantify the capillary impedance in both temperature ranges (which would allow us to diagnose partial blockages as well as complete blockages). We successfully cooled the dewar to He4 without blocking the capillary and ran the pumped pot. After Samuel left for Madison I heated the pot and observed the resulting temperature range. The results were somewhat surprising - the temperature responded weakly for a large range of input powers. We didn't have enough helium to keep the dewar cold over the weekend so the dewar is slowly warming up. Over the weekend I'm going to do the calculations suggested by friday's test. I'll send you a summary when I'm done. Monday Samuel and I will start working on a plan of action incorporating what we learned from last week's test and what Samuel learns from his visit to Madison. More cryogens should be delivered monday afternoon so we can do another run. I think we will want to seriously consider setting up to log temperatures, pressures and heater voltages on computer. I think we'll also want to revisit the method of attaching the capillary to the reservoir. An indium seal rather than a threaded expoxy seal would greatly increase our ability to investigate systems with varying flow impedance. We may even want to redesign the pot slightly to allow for better heat sinking to thermometers and heaters. cheers Jessie