User name stevensm
Log entry time 10:54:43 on June 1,2004
Entry number 124322
keyword=Q2 arbitrary helium level excursionOver the weekend we experienced several events where Right Q2's liquid helium level arbitrarily dropped and tripped the magnet's helium level interlock. Close review of the instrument plots we had running revealed that both of the liquid helium supply valves for that magnet were going completely shut for several hours immediately precedeing the event. This allowed the corresponding magnet U-tube to warm up. When a normal drop in liquid helium level did finally occur, the warm gas in the U-tube caused a rapid warming in the magnet with the resultant liquid helium level excursion. I asked Cryo (Pete Knudsen) to "prop open" one of Q2's supply valves 1 or 2 per cent, and he agreed. You can see the event below, note that the valves have an offset at zero, and are capable of some small movement without that movement being seen in the controls.
FIGURE 1
