Under the unfortunate circumstances that there is target material in the fridge that needs to be kept cold but we are low in LHe to keep filling the fridge we can use the QT system to keep the fridge cold directly using the following approach. The starting point here assumes that you are below the U-tube seam but not by much. If you are far below the seam the setup may change a bit. This mode should only be setup by someone who has done it before and in general we should do our best to avoid having to use this mode.
A.) Move the target to lower limit position to keep the material close to LHe. Keep the fridge in Hold Mode for as long as you can. Once the LHe is starting to get low set the magnet pressure higher at 6 or 6.5 psi (whatever the QT dewar you will use is set to).
B.) Once the fridge is completely out of LHe then open the gate valve and close the gv-bypass. Turn on the roots pumps one by one to try to keep the nose more vacuum insulated. Close the Magnet Return bypass and start sending the boil-off from the magnet through the separator. Set the separator to at least 30 slm for several minutes. Watch the magnet pressure and make sure it doesn't go below 0 during this preparation. After cooling the separator for at least 15 minutes you can start to open the run and bypass valves of the fridge and close the separator flow so that you are cooling the target material. You can start at 0.5 turns on the run valve and 1 turn on the bypass. Monitor the Cernox 7 and 8 temps and try to keep them not much over 50K in this phase. Once the magnet pressure starts to get close to 0 you have gone as far as you can.
C.) Once you have gone as far as you can with this configuration you must switch to slow precooling from one of the QT dewars. Close VPC and open the VJVT and VJVA/B so that the magnet pressure returns to the same as the QT dewar (~6.5 psi). In the beginning you will have to open the run and bypass more (2.0 on each). To stabilize the pressure in the magnet you should try to flow as much as you can through the Main flow alone. If you need to increase the separator flow from 0 to 20 slm for a bit that is also OK. After magnet pressure stabilizes set separator back to zero and reduce run and bypass to 1.5 turns each and set the magnet return bypass flow PID to between 20-15 slm. Balance the flows as needed as you have about 60 slm to work with. 45 slm through the fridge and 15 slm through the magnet with 0 through the separator should hold the temperature of the target material less than 70K for some time. If the initial conditions are different these numbers can differ a bit but the idea is to keep the level in the liquefier steady while we cooling the target material just below the level of concern. The target material will be fine with no changes to the paramagnetic complex if its stays under 80K. At 100K you are able to stay for 30 minutes which would count as an anneal with no damage. At 120K damage can occur if held longer than 15 minutes. If the only goal is to prevent the material from sublimating then you should try not to let it get much above 180K.
D.) If the dewar you have slow precooling from has enough LHe to afford using some you can cool much better my increasing the flow to the fridge which will still be quite slow if you keep the total flow below 80 slm. This will allow you to produce more LHe in the other dewar as needed for the next transfer. Generally, you should go as long as you can in C.) before having to consume more LHe in the QT dewar but if and when the level of cooling needs to be increase to delay the next fill you can do this as needed. You should also pay close attention to the magnet temperatures. Tank T and Tank B should not get too high otherwise you will need to spend additional liquid to cool them down again before the next fill otherwise the fill will not be efficient. Increase the magnet return bypass flow as need to keep these below 50K until you are ready for filling. Also watch the two coil temperatures. If you see Coil T go to 5.0K or above, its time for a magnet fill.
E.) Prepare to do a magnet fill by increasing the flow to the magnet to cool the tank off as much as possible. This may require at least 100 slm through the magnet return bypass for several minutes to bring Tank T and Tank B down below 20K. Once you've done this, you can prepare to switch from the slow precooling QT dewar to the one with the most liquid you intend to transfer. Set the PID on the magnet pressure to a value slightly higher than the current pressure (~6.7psi) and start the fast pre-cooling from the Dewar you will use to fill the magnet by opening VPC, close VJVT and VJVA/B whichever was used for the slow-precool and open VJVA/B that will be used for the fill. Fast-precool until TX1 is below 100K (~ 2 mins). Then, open VJVT and close VPC. Start the fill by fully opening the Magnet Return bypass. Increase the flow to the fridge and magnet return bypass as needed to keep the needed pressure difference. This should start at about 4 psi and will average around 3.5 psi. You can open up the separator from 10-70 slm if you need to increase the pressure difference at any time. Once you have been filling a while and think you are getting close to the seam you should close the bypass valve to 0 and close down the run valve to 1 or just pay very close attention to the fridge sensors to make sure you don't overfill the fridge (don't go above top heat exchanger). If not already done, open the separator flow to about 30 slm for about 15-20 minutes once you are at the seam. You can fill the fridge while you continue to finish filling the magnet. When its time you will see the temp of the Cernox drop down and the fridge sensor start to get cold (above 1400 at low fridge pressure). You can open the bypass to 3 turns until the fridge is completely full as needed. Once done you would normally set system back into hold mode to produce more liquid in the QT dewars.