Log entry time 18:06:48 on April 06, 2012

Entry number 370851

The attached figure shows the magnet's temperature (TI), pressure (PI), flow (FI), and liquid level (LL) prior to and during today's quench. The quench appears to have occurred at 09:52, based on the pressure and level spikes at that time.

The magnet was not being filled with LHe prior to the quench, so the boil-off flow (haFI91115) is low. However, there is a noticeable flow spike about 7 minutes before the quench, and a second much larger spike (greater than 200 slpm) about a minute later. I believe this indicates that the coils were being hit by the beam or by beam spray, and I estimate at least 15 Watts of power were deposited into the coils. Two magnet thermometers, both on the bottom, show significant heating during the quench, to about 20 K.

During the next Moller tuning, I recommend that MCC and the TO monitor the magnet flow meter (haFI91115) and shut off the beam if the flow increases more than 30 lpm above its quiescent value. The flow meter always reads overscale when the magnet is being filled with LHe, so make sure the magnet is full before the beam is tuned.

Magnet quench