[Esr-users] Hall C dipole shms magnet

[Steve Lassiter]

Hi

The Hall C SHMS dipole magnet tripped off this afternoon at about 4 PM.
The dipole trip caused the rest of the SHMS magnets to trip one after the other probably due to lead flow interlocks.

The dipole on line data evidence shows that this was a normal fast discharge.
A fast discharge of this magnet causes some coil heating due to eddy currents and this results in pressure and temperature rise in the coil.
Helium is usually vented by opening the warm return to keep Helium out of Hall C.
The warm return did not open fast enough and the pressure rose in the magnet reaching finally 5 atm.
The primary relief appears not to have opened at all or if it did open, it did not open far enough or long enough to limit the pressure.
The rupture disc worked as expected and vented the magnet and limited the pressure to 5 Atm.
When we entered the hall and inspected the SHMS dipole magnet the rupture disc was heavily frosted and still venting at a low rate while the mechanical relief valve was warm to the touch and dry.

The SHMS dipole was completely isolated and the rupture disc replaced.
We have set up a low rate ie. few grams per sec. ~ 80 K Helium purge thru the SHMS dipole to measure contamination levels overnight.

Cheers

Paul