Spectrometer Magnets Cryogenics

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The HMS has 4 superconducting magnets, Q1, Q2, Q3 and the dipole. The SHMS has 5, the horizontal bender, Q1, Q2, Q3 and the dipole.

The control screen for these magnets is started from the cdaq account on any counting house computer with the command

 % go_cmagnets

The OSP authorizing user operation of these magnets is ENP-17-65751-OSP.

This OSP includes the guidance below.

When to call the cryo group?

From P. Brindza, March 2, 2017. Will be integrated into manual.

There are just a few items on the ESR Data page that are most relevant to good Hall C cryogenic operations. The following table has the relevant data points, good nominal values and the operating points where a phone call to cryo is in order.

ESR Data Nominal best setting tolerable Call trigger
4K supply valve(1) 100% 91 % 90 %
4K supply pressure(1) 3.2 Atm 2.8 Atm P < 2.8 Atm
4k Return valve 106 % 104 % 100 %
4K return pressure(5) 1.2 Atm 1.2 Atm P rising
N2 supply valve(2) 50 % 50 % % < 50%
N2 supply pressure(6) 3.2 Atm 3.2 Atm P falling
Quench line pressure(3) 1.1 Atm 1.3 Atm P rising
Lead line pressure(4) 1.1 Atm 1.1 Atm P rising

Note 1: the 4K supply valves is sometimes regulated to close if Hall C takes too much flow from ESR. If Hall C has priority this should not happen. A small reduction is tolerable during ESR recoveries. The 4 K supply pressure will drop during recoveries from an ESR trip when the Hall C magnets are refilling. This is normal. If the 4 K supply pressure is dropping when all the magnets are near their liquid level hold point it could mean the 4 K supply valve has partially closed. If the pressure stays in the good range there is no real concern. If the 4K supply pressure is persistently low then it could mean that the 4K supply valve has been partially closed to maintain ESR health or it could be an oversight by the operator ie. Left over from an ESR recovery.

Note 2: The N2 supply valve is locked at 50 % due to Hall C ODH safety.

Note 3: The quench line pressure will rise after an ESR outage when Hall C magnets go on warm return to re-cool. This is normal. If all Hall C magnets are on cold return and the Quench line pressure is still high then this could indicate a trip of the CHL helium recovery system.

Note 4: The lead line pressure regulates current lead cooling in Hall C. If the lead line pressure is higher than normal this could cause current lead cooling trips of the Hall C Magnets. If the pressure is high it could mean that the local ESR helium recovery system has tripped off. All three Halls share this system and can communicate transients from Hall to Hall.

Note 5: The 4 K return pressure is regulated by the ESR pressure drop thru the heat exchangers and the ESR compressors. This never changes unless ESR trips off.

Note 6: The LN2 pressure is regulated by the large LN2 storage dewar. This can change during refilling. The Hall C magnets hold enough LN2 for 24 hours so short up to a few hour changes in this pressure do not matter.