Author

HY

Notices for the Liquid-nitrogen supply for the cryogenic production target

You have to keep watching (at least once in 1-2 hours) the temperature of the F0 gas target and the liquid-N2 level in the dewar on top of the target. If you do not put a new bottle for several hours after the expiration, you will probably have a low-intensity beam and the target foils can be broken by the warmed gas.

Temperature of the F0 gas target is shown at the right-upper side in the monitor near the control panel of CRIB, at J1 room.

• It should be around -170 degree. (In some conditions, it may show -130 to -180 degree, but still no problem.)
• You may have to turn off the room light to see it clearly.
• Lq. N2 level is also shown in the same the monitor, at near the center.
  
  • The level should be in between 1.0 and 2.0.
  • When the Lq. N2 dewar is empty, the level goes down, and displayed as "0.0". After 2-3 hours, the temperature starts to increase.
  • The level sensor should be set correctly (the bottom needs to go down for a certain depth.)
  • The sensor may stop working when ice particles get into the pipe. Use another sensor, stored in the shelf. The sensor possibly be revived when it is dried.
• We have two sizes of Lq. N2 dewars. Large one is 250 l, and small ones are 120l. We have 1 large, and 2 small bottles.
  • The large bottle should last for about 40 hours, and small one 20 hours.
  • When the circulation is turned on, the consumption rate will be faster. (760 Torr gas and 50 slm flow will make twice consumption as the case of no flow.)
  • If the supply of the Lq. N2 terminates much before than the expected time, you may try to open the pressurize valve more.

The exchange of the bottles should be done by the experienced persons, who had the training of liquid nitrogen (at RIKEN). The operation of the crane also needs a licence for that.

How to exchange the Lq. N2 bottle

When the Lq. N2 level shows a value lower than the set value "B" (2.0 @ 2012 Apr.), but the supply is still stopped, the Lq. N2 bottle should be empty. We should exchange the bottle with a filled one.

The bottle has 3 valves:

1. [P] Pressurize ("Ka atsu"), where the pipe is coming back to the bottle.
2. [G] Gas leak ("Gas housyutsu"), black one.
3. [N] Lq. N2 out ("Toridashi").

Procedure:

1. Change the setting of the automatic-supply control box. "Auto" to "Close", and make sure the "Fill" lamp is turned off.
2. Close [P], close [N], remove connections from [G] and [N].
3. Replace the bottle. (Needs the crane.)
4. Attach what removed in 2. to the new bottle.
5. Automatic-supply control box should be "Auto", and see "Fill" is turned on.
6. Open [N] and [G] fully.
7. Adjust [P] (~half rotation is enough) and the dial connected to [G], and keep the pressure ~0.05 MPa.
8. If you see the supply is working, close E7, and restart the measurement.
9. Fill Lq. N2 to the empty bottle.