Liquid He Transfer

Now that you have filled the IVC and MB with He gas, you can transfer LHe to the MB. This will allow the system to cool to 4.2 K. You need to order 100 L of liquid He for this transfer at least a day ahead of time which can be done through Bill Voje or Praxair via Kevin Roberts. The preference is to get the LHe from Bill. If he's gone, then we order it from Kevin. ~~Also, be prepared in terms of manpower - to do the transfer, two people are needed.~~ For every transfer you should wear gloves and goggles. There are a lot of instances where your skin can come in contact with cold metal and helium boil-off, and you require protection from this. Depending on when you're performing the LHe transfer (i.e. if it's the first transfer or a subsequent one) and what type of detector testing you are conducting, you will have to follow a slightly unique process for that transfer. Getting down to a proper base temperature to test detectors with phonon channels is not easy. There are several factors that contribute to this, one of them being evacuating the IVC sufficiently of He-4 exchange gas. If the exchange gas is not pumped out before the tower temperature reaches 4.2 K, it will begin to liquefy. This is a problem because if the He becomes a super-fluid, it can cause electrical shorts.

First Transfer (Testing Phonon Channels)

During this first transfer, you have to be mindful of several things:

Tower temperature - Before the tower temperature reaches 4.2 K, you MUST pump out the He exchange gas from the IVC or it will begin to liquefy. If testing phonon channels in this run, take note: The first transfer will take ~ 9 hours. This is because we let the main bath cool to 4.2 K using the natural pressure of the dewar instead of applying external pressure with He-4 gas from the gas tank. We want the system to cool slowly enough so that we can pump out the exchange gas in time.
Helium Recovery Line - When the transfer stick is entered into the main bath with He-4 boil-off flowing through it, open the top black helium recovery valve and the orange valve above the gas meter on the He recovery line.

You are going to use the two piece transfer stick to transfer LHe into the MB. Pump the transfer stick (if need be) so that it maintains its vacuum. The stick should not feel cold to the touch during the transfer (see instructions to evacuate transfer stick)

- Attach to the bottom of the short end of the transfer stick a brass nozzle with a circular hole. This is important for the first transfer because we want the LHe to be directed downwards when it's being transferred so that it cools the bottom of the MB.

If you ordered a dewar from Praxair, you need to attach a nozzle to the gas supply port on the LHe dewar. This is necessary for when we want to pressurize the dewar with He-4 gas via a clear hose. Use PTFE tape to secure the connection. Dewars from Bill already have this connection fastened.
Close the pressure-release valve - this will help to build pressure in the dewar, which is necessary to facilitate the transfer of LHe through the transfer stick.
You need to position the dewar appropriately by the platform such that both pieces of the transfer stick meet when inserted into the proper ports.
1. One person needs to climb the ladder to position the short end of the transfer stick above the middle exhaust port of the MB. They should hold this such that the stick is perfectly vertical (or as close as possible).
2. The other person holding the longer end of the transfer stick should position this end. above the dewar exhaust port. If it's not completely vertical, adjust the position of the dewar until this end of the transfer stick is also perfectly upright (or as close as possible).
Now you need to enter the transfer stick into the main bath and the dewar. The process is below:
1. Uncap the top port of the LHe dewar and enter in the long end of the transfer stick.
2. Open the valve on the exhaust port.
3. Slowly push the transfer stick down a few inches; place the black binder clip around the transfer stick flush against the top of the exhaust port to keep the stick from sliding down.
4. Every minute or so push the transfer stick into the dewar a couple of more inches - as you do so you're cooling the stick progressively.
5. If there is sufficient pressure in the dewar, the person on top of the platform should be able to feel some gas coming out of the short end of the transfer stick. If gas isn't coming out of the end, the dewar is probably not pressurized very well.
  - As the transfer stick is lowered into the dewar, there will be more LHe boil-off, which will contribute to the pressure inside of the dewar.
  - The natural pressure inside of the dewar should be sufficient for the beginning of the transfer. Eventually, after the transfer stick has been pushed to the bottom of the dewar and you want to initiate the transfer of liquid helium, you can provide additional external pressure to the helium dewar by using the He-4 gas supply. These steps will be provided later.
6. Continue to push the transfer stick by a few inches at a time into the dewar. As the stick cools, the gas inside the stick will cool as well. At some point you will hear the transfer stick sputter like a train, and this sound will alternate a bit with the soft “swoosh” of gas flow. For this first transfer, you've reached a sufficient point to enter the transfer stick into the MB (next step).
7. Unplug the middle exhaust port (with a gloved hand!) and enter in the transfer stick. For the first transfer, this is where you open the orange valve above the gas meter on the helium recovery line. Do this immediately!
8. Push the transfer stick down into the port by applying pressure on top of the stick - DO NOT WIGGLE IT IN. The transfer stick has a slight kink on it, so at one point you will notice that it becomes difficult to push the transfer stick in further. Whoever is on top of the platform, if they aren't already sitting on it, needs to climb up there and push down harder to get the stick to move in further.

* Note that as the longer end of the transfer stick gets pushed into the dewar, the short end can no longer stay vertical. To correct for this, extend the top part of the long end of the transfer stick by loosening the bolt (the person holding the longer end/ pushing it into the dewar will do this).

When the stick in the MB hits the transfer cone, lift it 1/8 inches and tighten the bolt.
If you look at the gas meter, you'll see that the hands on the bottom two dials are rotating. When they stop rotating, lower the long end of the transfer stick a few inches. The boil-off from lowering the stick should theoretically cause the dial hands to rotate again very slowly. If they are rotating too fast that means liquid is also entering the MB - that should not be happening at this time. Continue to lower the dewar little by little (few inches at a time) and let the boil-off continue to cool the system. If the dial hands rotate too quickly, stop lowering the stick and progress more slowly once the dial hands stop moving.
If the end of the transfer stick in the helium dewar hits the bottom of the dewar, raise the stick 2-3 inches so there are at least 4 liters of LHe left in the dewar at the end of the transfer. We want the to return the dewar to Bill with a few liters leftover.
Keep an eye on the temperature. It should dropping slowly because only the He-4 boil off should be cooling the main bath.
Record in the Helium Log book (it's blue, located on the lab notebook shelf) the gas meter reading, the helium liquid level, the start of the transfer, and the number of liters in the dewar. Skip a line in the log to differentiate between the previous run. Mark in the online run diary the start of the LHe transfer along with the initial liquid level.
Monitor the gas meter, helium liquid level and the tower temperature (on the LakeShore Bridge). At 10 K, pump out the exchange gas. Because the pressure is pretty low already (you entered < 0.1 mbar of He-4 gas into the IVC, and this lowers as the IVC cools), you can open the valve to the turbo pump pretty quickly (you should still monitor the pressure since the turbo shouldn't be overexposed to pressures > 10E-2 mbar). Thus, the scroll pump is not necessary here. Leave this line pumping overnight - the pressure should be < 10E-6 mbar in order to move on to the next stage of cool down.
Continue to monitor the temperature. Although you have pumped out the exchange gas, the temperature will still drop for some time. When the temperature finally levels off and stops decreasing (this should be above 4.2 K but below 10 K), you may begin applying external pressure to the helium dewar to facilitate transfer of the liquid helium.

Open the valve on the helium gas tank.
Open the helium (blue) valve on the gas line to let gas enter the clear hose. Tap on the open end of the clear hose to make sure gas is flowing out of it. The pressure of this gas should be 3 PSI. You can check this with the pressure gauge and adjust the pressure with the regulator on the gas tank if necessary.
Open the nozzle valve on the dewar such that some gas is escaping from the dewar. This should be sufficient flow for air not to enter the dewar.
Attach the clear hose to the nozzle port and close that valve partially such that the port is slightly open. Monitor the cycling of the gas meter and adjust the opening of the valve so that the dial hands are not rotating quickly.

When the helium liquid level reads 90% remove the transfer stick from the main bath and plug the exhaust port.

Close the valve on the dewar where the external gas is being supplied.
You must be careful as you pull out the stick. DO NOT WIGGLE IT OUT. Pull directly from above, which may require the person doing so to stand on top of the fridge.
As the transfer stick is being pulled out of the MB, open the pressure release valve on the helium dewar.
As the transfer stick is being pulled out of the MB, the other end of the stick should be pulled out of the dewar at the same time (you will have to shorten the long end of the transfer stick as you pull it out or it will hit the ceiling).

Close off the helium gas supply on the gas line and the tank.
Return the dewar to the basement and weigh it so that you can record the appropriate number of liters in the log book. Each pound of LHe is 3.63 liters.
Record the second round of information in the log book and note the end of the transfer in the run diary.
At this point you can clean the He3-He4 mixture again (if you wish).
Go home and rest. It's been a long transfer.

First LHe Transfer (Testing Charge Channels Only)

During this first transfer, you have to be mindful of several things:

Tower temperature - Before the tower temperature reaches 4.2 K, you MUST pump out the He exchange gas from the IVC or it will begin to liquefy.
Helium Recovery Line - When the transfer stick is entered into the main bath with He-4 boil-off flowing through it, open the top black helium recovery valve and the orange valve above the gas meter on the He recovery line.

You are going to use the two piece transfer stick to transfer LHe into the MB. Pump the transfer stick (if need be) so that it maintains its vacuum. The stick should not feel cold to the touch during the transfer (see instructions to evacuate transfer stick).

If you ordered a dewar from Praxair, you need to attach a nozzle to the gas supply port on the LHe dewar. This is necessary for when we want to pressurize the dewar with He-4 gas via a clear hose. Use PTFE tape to secure the connection. Dewars from Bill already have this connection fastened.
Close the pressure-release valve - this will help to build pressure in the dewar, which is necessary to facilitate the transfer of LHe through the transfer stick.
You need to position the dewar appropriately by the platform such that neither end of the transfer stick is bending when inserted into the proper ports.
1. One person needs to climb the ladder to position the short piece of the transfer stick above the middle exhaust port of the MB. They should hold this such that the stick is perfectly vertical (or as close as possible).
2. The other person holding the long piece of the transfer stick should position this end above the dewar exhaust port. If it's not completely vertical, adjust the position of the dewar until this end of the transfer stick is also perfectly upright (or as close as possible).
Now you need to enter the transfer stick into the main bath and the dewar. The process is below:
1. Uncap the top port of the LHe dewar and enter in the long piece of the transfer stick.
2. Open the valve on the exhaust port.
3. Slowly push the transfer stick down a few inches; place the black binder clip around the transfer stick flush against the top of the exhaust port to keep the stick from sliding down.
4. Every minute or so push the transfer stick into the dewar a couple of more inches - as you do so you're cooling the stick progressively.
5. If there is sufficient pressure in the dewar, the person on top of the platform should be able to feel some gas coming out of the short end of the transfer stick. If gas isn't coming out of the end, the dewar is probably not pressurized very well.
  - As the transfer stick is lowered into the dewar, there will be more LHe boil-off, which will contribute to the pressure inside of the dewar.
  - The natural pressure inside of the dewar should be sufficient for the beginning of the transfer. After the transfer stick has been pushed to the bottom of the dewar, if the flow rate seems to be decreasing (i.e. the rate of gas flow out of the end of the transfer stick, noted by the gas meter cycling, slows down), you can provide additional pressure using the He gas supply. These steps will be provided later.
6. Continue to push the transfer stick by a few inches at a time into the dewar. As the stick cools, the gas inside the stick will cool as well. At some point you will hear the transfer stick sputter like a train, and this sound will alternate a bit with the soft “swoosh” of gas flow. For this first transfer, you've reached a sufficient point to enter the transfer stick into the MB (next step).
7. Unplug the middle exhaust port (with a gloved hand!) and enter in the transfer stick. For the first transfer, this is where you open the orange valve above the gas meter on the helium recovery line. Do this immediately!
8. Push the transfer stick down into the port by applying pressure on top of the stick - DO NOT WIGGLE IT IN. The transfer stick has a slight kink on it, so at one point you will notice that it becomes difficult to push the transfer stick in further. Whoever is on top of the platform, if they aren't already sitting on it, needs to climb up there and push down harder to get the stick to move in further.
  - Note that as the longer end of the transfer stick gets pushed into the dewar, the short end can no longer stay vertical. To correct for this, extend the top part of the long end of the transfer stick by loosening the bolt (the person holding the longer end/ pushing it into the dewar will do this).
9. When the stick in the MB hits the transfer cone, lift it 1/8 inches and tighten the bolt.
10. If you look at the gas meter, you'll see that the hands on the bottom two dials are rotating. When they stop rotating, lower the long end of the transfer stick a few inches. The boil-off from lowering the stick should theoretically cause the dial hands to rotate again very slowly. If they are rotating too fast that means liquid is also entering the MB - that should not be happening at this time. Continue to lower the dewar little by little (few inches at a time) and let the boil-off continue to cool the system. If the dial hands rotate too quickly, stop lowering the stick and progress more slowly once the dial hands stop moving.
11. If the end of the transfer stick in the helium dewar hits the bottom of the dewar, raise the stick 2-3 inches so there are at least 4 liters of LHe left in the dewar at the end of the transfer. We want the to return the dewar to Bill with a few liters leftover.
12. Keep an eye on the temperature. It should dropping slowly because only the He-4 boil o should be cooling the main bath.
Record in the Helium Log book (it's blue, located on the lab notebook shelf) the gas meter reading, the helium liquid level, the start of the transfer, and the number of liters in the dewar. Skip a line in the log to differentiate between the previous run. Mark in the online run diary the start of the LHe transfer along with the initial liquid level.
When the dial hands on the gas meter stop rotating, it's time to apply external pressure to the dewar to facilitate the transfer.
- Open the valve on the helium gas tank.
- Open the helium (blue) valve on the gas line to let gas enter the clear hose. Tap on the open end of the clear hose to make sure gas is flowing out of it. The pressure of this gas should be 3 PSI. You can check this with the pressure gauge and adjust the pressure with the regulator on the gas tank if necessary.
- Open the nozzle valve on the dewar such that some gas is escaping from the dewar. This should be sufficient flow for air not to enter the dewar.
- Attach the clear hose to the nozzle port and close that valve partially such that the port is slightly open. Monitor the cycling of the gas meter and adjust the opening of the valve so that the dial hands are not rotating quickly.
Monitor the gas meter, helium liquid level and the tower temperature (on the LakeShore Bridge). At 10 K, pump out the exchange gas. Because the pressure is pretty low already (you entered < 0.1 mbar of He-4 gas into the IVC, and this lowers as the IVC cools), you can open the valve to the turbo pump pretty quickly (you should still monitor the pressure since the turbo shouldn't be overexposed to pressures > 10E-2 mbar). Thus, the scroll pump is not necessary here. Leave this line pumping overnight - the pressure should be < 10E-6 mbar in order to move on to the next stage of cooldown.
Continue to monitor the temperature. Although you have pumped out the exchange gas, the temperature will still drop for some time. The temperature should not drop below 4.2 K. Eventually, you should see the temperature start to rise slightly.
When the helium liquid level reads 90% remove the transfer stick from the main bath and plug the exhaust port.
1. Close the valve on the tank where the external gas is being supplied.
2. You must be careful as you pull out the stick. DO NOT WIGGLE IT OUT. Pull directly from above, which may require the person doing so to stand on top of the fridge.
3. As the transfer stick is being pulled out of the MB, open the pressure release valve on the helium dewar.
4. As the transfer stick is being pulled out of the MB, the other end of the stick should be pulled out of the dewar at the same time (you will have to shorten the long end of the transfer stick as you pull it out or it will hit the ceiling).
Close off the helium gas supply on the gas line and the tank.
Return the dewar to the basement and weigh it so that you can record the appropriate number of liters in the log book. Each pound of LHe is 3.63 liters.
Record the second round of information in the log book and note the end of the transfer in the run diary.
At this point you can clean the He3-He4 mixture again (if you wish) You should evacuate the IVC for about 5 hours before continuing on to the next step.

Subsequent LHe Transfers

After the first helium transfer, you will monitor the liquid helium level in the MB. As it gets low (<20%) another transfer will have to be done. Since the MB is already cold and has LHe inside, 100 L is not necessary for each of the following transfers. 60 L should be sufficient. To get the LHe you can ask Bill Voje or order from Praxair via Accounting. Usually a transfer needs to happen every other day, but this depends on the performance of the previous transfers. Note for subsequent transfers:

~~The brass nozzle at the end of the transfer stick needs to be changed.~~
When you unplug the exhaust port on top of the MB to enter in the transfer stick, cold air will rush out. Wear gloves and goggles when you unplug the exhaust port.
You don't need to rely on the natural pressure of the dewar to supply helium to cool the MB in subsequent transfers. Now you are only concerned with making sure the transfer stick has sufficiently cooled before entering it into the MB so that we don't boil off helium. If the pressure of the dewar seems low, we can start applying external pressure with He-4 gas from the gas tank from the beginning of the transfer.

~~Switch out the nozzle with the circular hole at the tip for the one with side slits. Because the MB is already cold, you don't need to use the nozzle that directs the liquid helium downward.~~
If you ordered a dewar from Praxair, you need to attach a nozzle to the gas supply port on the LHe dewar. This is necessary for when we want to pressurize the dewar with He-4 gas via a clear hose. Use PTFE tape to secure the connection. Dewars from Bill already have this connection fastened.
Close the pressure-release valve - this will help to build pressure in the dewar, which is necessary to facilitate the transfer of LHe through the transfer stick.
You need to position the dewar appropriately by the platform such that the long piece of the stick will reach the short piece so the connection between the two pieces can be made.
1. One person needs to climb the ladder to position the short piece of the transfer stick above the middle exhaust port of the MB. They should hold this such that the stick is perfectly vertical (or as close as possible).
2. first person puts short piece in cryostat…
3. The other person holding the longer end of the transfer stick should position this end above the dewar exhaust port. If it's not completely vertical, adjust the position of the dewar until this end of the transfer stick is also perfectly upright (or as close as possible).
Now you need to enter the transfer stick into the main bath and the dewar. The process is below:
1. Uncap the top port of the LHe dewar and enter in the long end of the transfer stick.
2. Open the valve on the exhaust port.
3. Slowly push the transfer stick down a few inches; place the black binder clip around the transfer stick flush against the top of the exhaust port to keep the stick from sliding down.
4. Every minute or so push the transfer stick into the dewar a couple of more inches - as you do so you're cooling the stick progressively
5. If there is sucient pressure in the dewar, the person on top of the platform should be able to feel some gas coming out of the short end of the transfer stick. If gas isn't coming out of the end, the dewar is probably not pressurized very well.
  - As the transfer stick is lowered into the dewar, there will be more LHe boil-off, which will contribute to the pressure inside of the dewar.
  - The natural pressure inside of the dewar should be sufficient for the beginning of the transfer. After the transfer stick has been pushed to the bottom of the dewar, if the flow rate seems to be decreasing (i.e. the rate of gas flow out of the end of the transfer stick, noted by the gas meter cycling, slows down), you can provide additional pressure using the He gas supply. These steps will be provided later.
6. Continue to push the transfer stick by a few inches at a time into the dewar. As the stick cools, the gas inside the stick will cool as well. At some point you will hear the transfer stick sputter like a train, and this sound will alternate a bit with the soft “swoosh” of gas flow.
7. Soon you will uncap the top port of the MB. The person holding the short end of the transfer stick needs to be alert to a change in the gas consistency as it flows out of the stick. As a safety precaution, it necessary to keep your hands gloved because the gas will cool the stick and your hand as it flows out. When the train sound no longer returns and the visible gas is consistently flowing out of the stick, it is soon time for the stick to be entered into the MB. When the gas flow becomes a distinct, sharp flow (a “plume”, it's known to be called), you can enter the stick into the MB (next step!). Because the MB already has liquid helium in it, boil-off will rush out when the bung is pulled out. Again, this is why gloves and goggles are a requirement.
8. Push the transfer stick down into the port by applying pressure on top of the stick - DO NOT WIGGLE IT IN. The transfer stick has a slight kink on it, so at one point you will notice that it becomes difficult to push the transfer stick in further. Whoever is on top of the platform, if they aren't already sitting on it, needs to climb up there and push down harder to get the stick to move in further. * Note that as the longer end of the transfer stick gets pushed into the dewar, the short end can no longer stay vertical. To correct for this, extend the top part of the long end of the transfer stick by loosening the bolt (the person holding the longer end/ pushing it into the dewar will do this).
9. When the stick in the MB hits the transfer cone, lift it 1/8 inches and tighten the bolt.
10. If you look at the gas meter, you'll see that the hands on the bottom two dials are rotating. When they stop rotating, lower the long end of the transfer stick a few inches. The boil-off from lowering the stick should theoretically cause the dial hands to rotate again very slowly. If they are rotating too fast that means liquid is also entering the MB - that should not be happening at this time. Continue to lower the dewar little by little (few inches at a time) and let the boil-off continue to cool the system. If the dial hands rotate too quickly, stop lowering the stick and progress more slowly once the dial hands stop moving.
11. When the end of the transfer stick in the helium dewar hits the bottom of the dewar, raise the stick 2-3 inches so there are at least 4 liters of LHe left in the dewar at the end of the transfer. We want the to return the dewar to Bill with a few liters leftover.
Record in the Helium Log book (it's blue, located on the lab notebook shelf) the gas meter reading, the helium liquid level, the starting time of the transfer, and the number of liters in the dewar. Mark in the online run diary the start of the LHe transfer along with the initial liquid level.
When the dial hands on the gas meter have significantly slowed down or stopped rotating, it's time to apply external pressure to the dewar facilitate the transfer.
- Open the valve on the helium gas tank.
- Make sure there is a clear hose attached to the He gas line
- Open the helium (blue) valve on the gas line to let gas enter the clear hose. Tap on the open end of the clear hose to make sure gas is flowing out of it. The pressure of this gas should be 3 PSI. You can check this with the pressure gauge and adjust the pressure with the regulator on the gas tank if necessary.
- Open the nozzle valve on the dewar such that some gas is escaping from the dewar. This should be sufficient flow for air not to enter the dewar.
- Attach the clear hose to the nozzle port and close that valve partially such that the port is slightly open. Monitor the cycling of the gas meter and adjust the opening of the valve so that the dial hands are not rotating quickly.
Monitor the gas meter and the helium liquid level. If the dial hands rotate too quickly, lessen the amount of external gas being supplied to the dewar by closing the valve on the dewar slightly.
When the helium liquid level reads 90% (you should be checking the level every 10 minutes or so) remove the transfer stick from the main bath and plug the exhaust port.
1. Close the valve on the tank where the external gas is being supplied.
2. You must be careful as you pull out the stick. DO NOT WIGGLE IT OUT. Pull directly from above, which may require the person doing so to stand on top of the fridge.
3. As the transfer stick is being pulled out of the MB, open the pressure release valve on the helium dewar.
4. As the transfer stick is being pulled out of the MB, the other end of the stick should be pulled out of the dewar at the same time (you will have to shorten the long end of the transfer stick as you pull it out or it will hit the ceiling).
Close off the helium gas supply on the gas line and the tank.
Return the dewar to the basement and weigh it so that you can record the appropriate number of liters in the log book. Each pound of LHe is 3.63 liters.
Record the second round of information in the log book and note the end of the transfer in the run diary.