Layout of the cooling circuit of the magnet. The fridge turbines provide a temperature of about 10 K and the 2 JT valves reduce the temperature finally to 4.7 K. Heat exchangers take care that the large He flow is decoupled from the energy flow.
Cooldown of the magnet using the 12 year old TCF20 with
the internal JT valve disabled. Still going strong.
The second cooldown was faster (after a dull mistake was corrected).
Cooling water in experimental area switched off for about 6 hours.
Compressor stopped after 4 1/2 hours without cooling water. All liquid
He was evaporated and most of it went to the recovery waiting there for cleanup.
Quench with quench detector disabled.
Practically all the field energy (350 kJ) was deposited in coil E.
The strong increase of the pressure forced several relief valves to open and
about 200 m**3 He at 4.7 K temperature were blown into the cave. Consequently
it was raining liquid air for several short moments.
The fast logging shows that the relief valves fired 4 times.
Shortly after the quench the liquid Nitrogen supply pressure increased above the set point
of the relief valve (6b). It was caused by a refill of the Nitrogen vessel. About 14 tons of liquid
Nitrogen had to be cooled by app. 4 K in order to reduce the pressure by 1 bar. About 800 m**3 of
Nitrogen was blown into the air.
Quasi quench with quench detector enabled. The liquid He level rises after the quench,
since the 2.8 bar vessel expands its cold He into the 1.3 bar reservoir producing liquid via
the JT valve which controls the expansion. Most field energy was deposited in a quench resistor
which got quite hot.
Power supply shows some oszillations at large currents but no quench is initiated.
After the heater fires, the pressure increases, the inlet temperature decreases and the liquid He level increases even more.
Finally the heater wins and the level goes down.
Warm-Up takes several weeks
