| Line 1 was replaced by line 1 |
| - * fill the cold trap with liquid nitrogen and make sure that |
| + * Fill the cold trap with liquid nitrogen and make sure that |
| At line 2 added 53 lines. |
| + * Make sure that all tubes are connected correctly |
| + |
| + * On the Variox or Magnet VTI, open the needle valve more than |
| + normally in order to fill the pumping volume with some |
| + amount of liquid helium. Put "flow" of 20 mbar until the |
| + 1 K pot temperature is stable below 3 K. Then close |
| + the needle valve until a "flow" of about 10 mbar is reached |
| + (the pressure decreases only slowly). Then regulate the |
| + valve at about 10 mbar. This value must not be obeyed exactly, |
| + the idea behind the needle valve settings is the following: |
| + ** A lower flow is better for consumption (a "flow" of more |
| + than 10 mbar increase substatnitally the He consumption, but |
| + during the process of condensing it might be o.k.). |
| + ** The flow should be high enough to hold the 1 K pot temperature |
| + low (over long term: about 2 K with the Variox and about 2.5 K |
| + with the MA09). During the condensing phase, the 1 K pot temperature |
| + might increate to 3.5 K for a short time, when pushing the |
| + mixture quickly. |
| + |
| + * Open the 3 valves in the pumping line and the 2 valves in |
| + the condenser line. |
| + * Open the green valve marked "out" below the dump. The dump is the |
| + grey cylinder in the center of the gas handling system rack. |
| + * Open valve 9 (while pressing on the black valve button, press |
| + RAISE). |
| + * The reading on G2 is proportional to the amout of mixture in the |
| + dump. It should read something around 660 mbar. |
| + * Open valves 1 and 6 (Valve 6 is a motor valve, while pressing |
| + the red valve button, press RAISE until a value of 99.9 is shown). |
| + * Open a little valve 12A (4.0 % to start). |
| + * While the pressure reading on G1 should always be below about 400 mbar, |
| + Valve 12A can bae opened gradually, and opened completely, when the |
| + reading on G2 drops below 350 mbar. |
| + |
| + * After some time (about 30 min when using the Variox) the pressure on |
| + G1 falls below 150 mbar, and it is time to pump out the dump: close |
| + valve 9, and open valve 14 for a short time (close it when P1 raises |
| + above 50 mbar). As soon as the pressure on P1 drops down, you might open |
| + and close valve 14 again, but make sure that the pressure on G1 does |
| + not increase above 350 mbar. |
| + * At some stage, when opening valve 14, the pressure on P1 does no longer |
| + raise above 50 mbar. Leave the valve open until the P1 drops below 0.1. |
| + * The temperature in the mixing chamber goes down in steps during the |
| + condensation process. It takes some time until the temperatures start |
| + to move downwards, and goes then quickly below 1 K. Then it stays there |
| + or decreases slowly to about 0.8 K, for about half an hour or more, before |
| + going down by more than 0.01 K per minute. |
| + |
| + * Once the temperature has stabilized in the region of 0.1 K or less, |
| + the flow on the condenser line might falls below 100 (black display below |
| + the valve panel). |
| + Setting the still heater to a power of 3-5 mW, the flow can be increased |
| + back to about 100, and the temperature should go down more. Good luck! |
LIN