From MORSE@bnlarm.bnl.govTue Jul 9 11:04:46 1996 Date: Tue, 09 Jul 1996 10:19:44 -0400 (EDT) From: "William M. Morse" To: earle@buphy.bu.edu, monich@buphyc.bu.edu, varner@buphyc.bu.edu, OUYANG@buphyc.bu.edu, CAREY@buphyc.bu.edu, mapes@BNLDAG.AGS.BNL.GOV, krienen@BNLDAG.AGS.BNL.GOV, tallerico@BNLDAG.AGS.BNL.GOV, messier@buphy.bu.edu Subject: Minutes of Energy Extraction Meeting Resent-From: MORSE@bnlarp.bnl.gov Resent-Date: Tue, 9 Jul 1996 10:22:09 -0400 (EDT) Resent-To: stillman@stillman_a.ags.bnl.gov, woodle@ad1.ags.bnl.gov, YIM@INP.NSK.SU, dz@budoe.bu.edu Minutes of July 8, 1996 Full Current Energy Extraction Meeting We reviewed the events of July 3. At 10am we powered the storage ring magnet to half-field (2450A) and extracted the energy as a system test. The results were consistent with the last energy extraction at half-field in January. Although we haven't yet written a half-field energy extraction g-2 note, we have quantitative agreement with our quench model. By 11:30am we had cooled down again and powered the magnet to full current (5200A). We then ramped to 5300A at 1A/s, and recorded the strain gauge readings. Some of the readings changed significantly. We had planned to ramp from 5300 to 5350A, but decided to delay this until we have completed the strain gauge analysis. We then ramped down to 5200A and at 12:42pm extracted the energy. The outer temperature went to about 38K, the inner temperatures were lower, as expected. The outer cryostat pressure went up to the mid -4 Torr range, the lead pot and inner pressure was in the -7 Torr range. This is acceptable. We had cooled down to 5K again by 3:15pm; however, we had used all the liquid Helium in the Control Dewar. Then at 4:30pm we lost computer control of the cryo system! It was restored about an hour and half later; however, the system had started to warm up (the compressors and expansion engine were off for this time). At 8pm, the outer coil temperature was 23K, the inner temperature was 34K. The inner cryostat pressure went up to the mid -4 Torr range, lead pot to the mid -5 Torr range, and the outer -7 Torr. It took about one shift to cool-down to 5K again. What an eventful day! Due to several factors, we still haven't looked at the temperature files. Hopefully, we can do this tomorrow. The 5200A energy extraction coil voltages are not what we expected! I show below the voltages from the energy extraction at 2450A and 5200A at t=0, ie. when the contactor was opened: 2450A 5200A Outer Lower -5.6V -12V Outer Upper -5.6V -12V Inner Lower -4.8V -6V Inner Upper -4.9V -3V The outer coil voltages are consistent with what we expected. The outer lower coil went normal at about 1.5 seconds, the upper at about 2 seconds. The DCCT coil current is consistent with what we expected. However, the inner voltages and the magnet voltage (sum of all the coil and interconnect voltages) are too low. The magnet voltage divided by the nominal dump resistance value is inconsistent with the DCCT measurement of current until after 5s: time (s) DCCT (A) V/Rd (A) 0 5200 3950 5 3700 3900 10 2900 3200 Since the resistance of the dump resistor increases with temperature, we expect V/Rd to be somewhat higher than the DCCT current. One explanation of the effect would be that the contactor was not completely open until after 5 seconds! However, we would also have to assume that the inner coils went normal much earlier than the outer. We wouldn't expect this, and it didn't happen that way at lower currents. We are eagerly awaiting the temperature analysis, and will have another meeting later in the week. Respectfully submitted - Bill Morse.