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The fast+slow pre-cooling allows us to reduce the slow pre-cooling time by initially fast pre-cooling the first part of the transfer line and then transit to the slow pre-cooling. Figure 2 (right) shows an example of the Tank T behavior of a slow pre-cooling that followed a fast pre-cooling. It is observed that the Tank T temperature drops significantly faster when a fast pre-cooling is initially performed reducing the slow precooling time to about 1 to 2 hours. This initial fast pre-cooling consumes 4 additional liters of LHe on the Liquifier.
Figure 2: Tank T temperature behavior for slow pre-cooling (left) and fast+slow precooling (right) procedures.
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The different pre-cooling procedures are given below. Please confirm with the target expert the pre-cooling mode to be conducted.
Slow
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Pre-cooling:
1. Enable the Flow PID control of the Magnet Return Bypass at 65 slm.
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Note: Liquifier A/B should be on Liquify mode. If at the time of starting the slow pre-cooling the Liquifier A/B is on Idle mode, start the slow pre-cooling and when 4L are consumed on the Liquifier then change it to Liquify mode.
Proceed to fill the magnet filling steps anytime after the transfer lines are cold. The system is sufficiently cold once the Tank T temperature decreases after opening VJVT (about 5 4 hours). The figure below shows an example of the Tank T behavior during a slow pre-cooling.
Fast
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Pre-cooling:
1. Open VJVA/B (ensure VPC is already opened).
2. Wait for TX1 temperature to drop bellow 100K (~ 4 min with GV02 fully opened).
3. Enable Enable the Flow PID control of the Magnet Return Bypass at 65 slm.
24. Open VJVA/B, open VJVT and close VPCVJVT and wait for magnet pressure to increase to 6 PSI.
5. Close VPC and proceed to the filling steps.
Fast+Slow pre-cooling:
1. Open VJVA/B (ensure VPC is already opened).
2. Wait for TX1 temperature to drop bellow 100K (~ 4 min with GV02 fully opened).
3. Enable the Flow PID control of the Magnet Return Bypass at 65 slm.
4. Open VJVT and close VPC.
Proceed to the filling steps anytime after the transfer lines are cold. The system is sufficiently cold once the Tank T temperature decreases after opening VJVT (about 1 hour).
Filling
1. Open the MagRetBypass valve fully by pressing the "Full Open" button on "MagRetBypass_Main.vi" in CCP and wait until you can see it is fully open on the CCP panel. The magnet pressure will start decreasing. The FMR may spike momentarily.
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