Before precooling, clean the capillaries of the VTI and the lambda-plate, or air freezing in the lines will cause blockages and operation of the VTI and of the lambda-plate won't be pssible.
If not already done, switch the large T valve of the Helium tank from the recovery line to air (follow the flux indicator on the valve). WARNING: when doing this, although the valve goes heavy, do not put any serious force and torque!! If you do, the IVS vacuum might become worse or broken! Always switch this valve carefully!
Close with a blind flange the exit to the air.
Open the VTI valve to the recovery line, if not already open.
Open the lambda-plate valve to the recovery line, if not already open.
Open both needle valves fully. (NOTE 1: these are “heavy duty” neelde vavles. There shaft is very thick and the “needles” are large. This means that they can be open/closed with relatively larger force than common needle vavlves. Furthermore, the VTI needle valve does feel particlularly heavy and hard. Don't be worried about this. NOTE 2: when opening the needle valves, a certain amount of turns is necessary beforeyou'll hear a clear “click” sound. After this sound open the vavlve further and fully till the end. When closing, you won't here the click sound. See the manufacturer manual for details of the constructionof the needle valves.)
Switch on the Helium pump (1 stage rotary pump (Leybold) in room 626, pump cabinet, top pump), with pump exaust to air.
Connect a Helium storage vessel or a Helium bottle to the recovery line.
Close the main He recovery line valve (on the top of the computer desk).
Check that the He transfer port plug is properly closed and sealed.
Close the Helium storage/He bottle valve. Pump out the He tank and the capillaries and the VTI, by opening the big red pumping valve on the pump panel. The pressure will decrease very slowly due to the large space (He tank) and narrow capillaries. Wait till the pressure is at least below 5 mbar and then close the puming red valve.
Open the Helium storage valve. Let the Helium flow for some time (it has to flow through the narrow capilalries).
Repeat the last 2 steps (pump and flush with He) at least 4 times. Now the lines should be cleaned and full of dry He.
Close both needle valves: be sure that they are closed, but do not force them.
Leave VTI and lambda-plate valves open to recovery. OPEN main Helium recovery line valve.
Take a liquid Nitrogen storage dewer, full.
Remove the blind flange from the He-tank exaust and temporarily close (with a ball of cotton or paper) the air exaust of the He tank.
If not already done, switch now the large T valve so that the He exaust goes to air: look on flow direction indicator (operate vavlve gently, no torque!).
Connect the liquid Nitrogen transfer rod (the one with white conical outlet at the bottom) to a flexible teflon tube, if not already connected. Connect the tube to the LN2 out of the storage dewer.
Remove the He tank plug and insert the rod fully (NOTE: the plug sits in a sliding seal. This seal might be the one normally used for He transfer. If too small for the nitrogen transfer rod, remove the seal first. Keep the seal for the end of the procedure.)
Pressurise the dewer and start filling (remove the cotton ball from exaust). Start with 400-500 mbar. When liquid will accumulate (boil off noise reduces) pump pu the pressure slowly, up to 1 bar. Filling can take 45 minutes. Filling must be stopped when the nitrogen overflows out from the exaust.
Close the LN2 dewer, release the pressure. You can leave the transfer rod inside the whole night.