Fill LN2 Cold Trap

To clean the He3-He4 mixture and to maintain cleanliness, the liquid nitrogen cold traps need to be full. Thus, they are to be lled twice a day. There are several ways to fill the cold trap.

1. Using the small 5 L dewar with the green cap, go to the gas tank room on the basement level of the building, located next to the space where liquid nitrogen and helium dewars are held.
2. For protection, wear the gloves and face shield provided.
3. Remove the green cap and insert the metal hose attached to the LN2 dewar.
4. Open the LN2 dewar and fill the 5 L dewar.
5. Close the LN2 dewar and remove the metal hose. Re-cap the 5 L dewar.
6. Fill out the sheet provided on the table next to the dewar to record how much LN2 you took. You will need to know the appropriate account number so that it can be charged for the LN2 taken.
7. Back in the lab, with the filled 5 L dewar, remove the stopper from the LN2 cold trap canister.
8. Insert the plastic funnel from the hole where you removed the stopper.
9. Remove the green cap and begin pouring the LN2 into the funnel. There will be some boil-off because the funnel is warm and depending on how much LN2 is already in the cold trap canister, it may need to cool down again.
10. Fill the cold trap full. One 5 L dewar should be sufficient. You'll know if it's done if you see LN2 spill out, or you can check by removing the funnel and shining a flashlight through the hole. If you can see the liquid clearly, it's sufficiently full.
11. Insert stopper again.

1. Using the 25 L 'bomb' dewar with the black plug cap, go to the gas tank room on the basement level of the building, located next to the space where liquid nitrogen and helium dewars are held. Bring with you the wheeled support for the bomb dewar because, once the dewar is filled, it will be quite heavy to carry
2. For protection, wear the gloves and face shield provided.
3. Remove the black cap and insert the metal hose attached to the LN2 dewar.
4. Open the LN2 dewar and fill the 25 L dewar.
5. Close the LN2 dewar and remove the metal hose. Re-cap the 25 L dewar.
6. Fill out the sheet provided on the table next to the dewar to record how much LN2 you took. You will need to know the appropriate account number so that it can be charged for the LN2 taken.
7. Lift the filled bomb dewar onto the wheeled support. Transport the dewar back to the lab by wheeling it to the elevator, and then use the elevator lift next to the lab to bring it down into the lab.
8. In order to get the LN2 to flow into the cold trap, nitrogen gas needs to pressurize the bomb dewar. There is a copper transfer tube that you will insert into the bomb dewar soon. First, attach a rubber hose to one end of the transfer tube.
9. Remove the stopper from the LN2 cold trap canister.
10. To the other end of the rubber hose attach a copper L-shaped tube and insert this tube into the hole where you removed the stopper.
11. Uncap the bomb dewar, and insert the copper transfer tube and make sure the rubber stopper attached to the transfer tube is lodged into the bomb dewar's opening. This will allow you to pressurize the dewar effectively when nitrogen gas is supplied. Note that when you insert the transfer tube into the dewar and latch it down that some gas will start boiling off and flow through the rubber hose.
12. Attach one end of a clear hose to the nitrogen gas copper line and the other end to the copper transfer tube.
13. Open the nitrogen gas tank and open the nitrogen gas valve that the clear hose is connected to. Very soon you should be able to see the rubber hose connected to the cold trap start to cool. This indicates the transfer has begun.
14. Fill the cold trap full. One 5 L dewar should be sufficient. You'll know if it's done if you see LN2 spill out.
15. When the cold trap is full, pull o the clear hose supplying the nitrogen gas to stop the transfer quickly.
16. Remove the transfer line from the cold trap and insert the stopper into the cold trap canister.
17. Turn off the nitrogen gas supply and close the valve on the copper line.

1. If you have a 160 L dewar at your disposal, you can use this to fill the LN2 cold trap.
2. Attach to one end of a long rubber hose an L-shaped metal tube.
3. Attach another L-shaped tube to the LN2 dewar. There is only one appropriate tube that can fit to the dewar's liquid outlet.
4. Connect the other end of the rubber hose to the tube you just attached to the LN2 dewar.
5. Remove the stopper from the LN2 cold trap canister.
6. Insert the free end of the rubber hose (with the metal transfer tube) into the LN2 canister.
7. Open the liquid valve on the LN2 dewar slowly so that the hose starts to cool. Once it cools you can open the valve further to increase the flow of LN2 into the cold trap.
8. Fill the cold trap full. You'll know if it's done if you see LN2 spill out. Shut the liquid valve on the dewar and pull out the transfer hose from the cold trap and stopper it.