Hello Everybody:
Here is an updated list of old magnets. The oldest in this list is a 200 MHz Oxford magnet which was first installed in the Chemistry Department of Heriot-Watt University on October 1, 1982. Although the magnet did quench once during a helium refill, the seal has never been changed. The LHe boil-off has not changed since it was installed. It was believed that the best way to keep the seals in good condition is to make sure they don't get wet.
I would like to take this opportunity to thank Jerry Hirschinger, David VanderVelde, Debbie Shalev, Edward Waali, and Szalontai Gábo for sharing their experience on pumping a magnet. When the helium boiloff rate was significantly higher than normal, they could bring the helium boiloff rate back to normal by pumping the vacuum of the magnet. However, the boiloff slowly increases again after the pumping, especially after each helium refill. It takes about a year or so for the helium boiloff rate to reach significantly higher level again.
Thanks,
Weixing Zhang
1982
200 MHz Oxford [hw.ac.uk] The LHe boil-off has not changed since it was installed.
1983
300 MHz Oxford [sri.org] (original seal) Helium and Nitrogen boil-off is identical as the original specs.
360 MHz Oxford [uic.edu] resealed when updated in 2001. works great, no change in N2 or He boiloff
1984
500 MHz Oxford [berkeley.edu] installed 1984, at field since 1985
hold time and He boil-off rates have not measurably changed.
1985
500 MHz Oxford [chem.ucla.edu] dewar refurbished 1993 due to relocation, no problem before the refurbishment. no increase in boil-off
360 MHz Oxford [wisc.edu] obtained used in 85, rebuilt 1999; same as installed
500 MHz Oxford [wisc.edu] rebuilt 1999; same as installed
400 MHz Oxford [columbia.edu] all boil off rates are normal.
400 MHz Bruker [ucalgary.ca] Original seal, moved cold in 1990
300 MHz Oxford [ineos.com] Reenergized for different reasons in 1995, 1996, and 2000; seals replaced on one of those occasions. Has high LN2 boiloff due to internal adjustments (not seal-related) but LHe boiloff is still in spec.
300 MHz Spectrospin [lubrizol.com] very similar He, N2 boil off as when installed.
500 MHz Oxford [ohio-state.edu] refurbished (due to a move) in 1998.
500 MHz Bruker [unsw.edu.au] refurbished in 2006 due to relocation, working well before and after relocation.
1986
500 MHz Oxford [chem.ucla.edu] dewar refurbished 1993, due to relocation, no problem before the refurbishment. no increase in boil-off
500 MHz Oxford [mbi.ucla.edu] refurbished 1993. The hold time/volume hasn't changed.
400 MHz Oxford [ineos.com] Original seal, Boiloff has not changed.
1987
400 MHz Oxford [berkeley.edu] hold time and He boil-off rates have not measurably changed.
500 MHz Oxford [uic.edu] resealed 1997, no change in N2 and He boiloff.
300 MHz Oxford [siu.edu] Since installation in 1987, cryogen consumption has not changed.
500 MHz Oxford [siu.edu] Since installation in 1987, cryogen consumption has not changed.
200 MHz Bruker [ut.ee] no remarkable cryogens consumption change
360 MHz Oxford [binghamton.edu] boiloff is normal
600 MHz Oxford dual can [colostate.edu] still up
300 MHz Oxford [colostate.edu] went soft in 2009
300 MHz [iastate.edu] still has the same boil off rate.
250 MHz Bruker [ohio-state.edu] refurbished in 1998.
1988
300 MHz Oxford (chem.ucla.edu) no increase in boil-off
500 MHz Oxford [wisc.edu] ca. as installed (maybe slightly higher boiloff over last year)
500 MHz Oxford [uoregon.edu] boiloff remains about the same as when new
300 MHz Oxford [selcia.com] He boil-off rate did increase slightly about 5 years ago
1989
400 MHz Bruker [berkeley.edu] hold time and He boil-off rates have not measurably changed.
250 MHz Oxford [unm.edu] (moved and seals changed 1998) boiloffs are close to original
500 MHz Bruker [ucalgary.ca] Original seal, has never been recharged in the past 20 years.
500 MHz Oxford [hawaii.edu] He and LN boil off rates have not changed in twenty years.
400 MHz Oxford [nmsu.edu] boil off rates for nitrogen (180) and helium (2-4) are normal.
360 MHz Oxford [uvic.ca] hold time and boil off rate do not seem to have changed.
1990
400 MHz, oxford [averydennison.com] boiloff same as usual with no big changes over the years
400 MHz Oxford [UTMB) no significant change on cryogen boil off
1991
250 MHz Oxford [unm.edu] boiloffs are close to original
2x 600 MHz Oxford [bms.com] no change in boil off rates
500 MHz Oxford [ineos.com] Original seal, boiloff has not changed.
2x 300 MHz Bruker [unsw.edu.au] moved cold in 2006, working fine.
1992
300 MHz Bruker [berkeley.edu] hold time and He boil-off rates have not measurably changed.
270 MHz Oxford [memphis.edu] LN2 20% remaing after one week (vs. 35% in 1992).
LHe 30% remaining after 3 months (vs 35% in 1992)
400 MHz Bruker [South Africa] Helium consumption is still at 3% per week as it was in 1992.
600 MHz [spcorp.com]
500 MHz Oxford [unmc.edu] still stable at field
400 MHz Oxford [rz.uni-leipzig.de]
1993
500 MHz Bruker [chem.ucla.edu] no increase in boil-off
2x 300 MHz Oxford [wisc.edu] same as installed
500 MHz Bruker [mbi.ucla.edu] hold time/volume hasn't changed since it was installed. It was a demo magnet for a year or to before installation in 1993.
1994
400 MHz Bruker [chem.ucla.edu] no increase in boil-off
300 MHz Bruker [unm.edu] boiloffs are close to original
300 MHz Bruker [poczta.fm] Boiloff is the same in 15 years.
500 MHz Bruker [columbia.edu] All boil off rates are normal.
1995
600 MHz Oxford [UTMB) no significant change on cryogen boil off
750 MHz Oxford [UTMB) no significant change on cryogen boil off.
400 MHz Bruker [uconn.edu] No change in boiloff in the last 8 years.
300 MHz Oxford [uoregon.edu] boiloff remains about the same as when new
600 MHz Oxford [unsw.edu.au] refurbished in 2007 due to relocation, working well before and after relocation.
1996
600 MHz Magnex [mbi.ucla.edu] hold time/volume hasn't changed since installation.
2x 300 MHz Bruker [columbia.edu] All boil off rates are normal.
600 MHz Oxford [uoregon.edu] boiloff remains about the same as when new
1997
600 MHz Oxford [bms.com] no change in boil off rates
600 MHz Oxford [stjude.org] boiloff is about the same
600 MHz Bruker [macbeth.ls.huji.ac.il] Helium boil-off is 40% more, N2 is about the same
1998
500 MHz Bruker [unm.edu] boiloffs are close to original
600 MHz Oxford [stjude.org] boiloff is about the same
2000
600 MHz Oxford [wisc.edu] same as installed
200 MHz Oxford [unsw.edu.au] moved cold in 2006, working fine.
2004
800 MHz US2 Bruker [mbi.ucla.edu]
400 MHz Bruker [poczta.fm] Boil-off ~2% per week and not changed.
300 MHz Bruker [uconn.edu] No change in boiloff.
500 MHz Bruker [uconn.edu] No change in boiloff.
600 MHz Bruker [uconn.edu] No change in boiloff.
2005
600 MHz Bruker [poczta.fm] Boil-off ~3% per week and not changed.
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Received on Mon Jun 22 2009 - 11:59:57 MST