| At line 0 added 4 lines. |
| + !!Orange Cryostat Cooldown Procedure |
| + |
| + For some general remarks on cryogenic handling at the Neutron guide hall [see|http://lns00.psi.ch/sinqwiki/Wiki.jsp?page=CryogenicHandling]. |
| + |
| At line 1 added 1 line. |
| + This is normally done by a sample environment technician |
| Line 16 was replaced by line 21 |
| - * Increase the temperature of the heat exchanger to 100 K. |
| + * Increase the temperature of the heat exchanger to 100 K. (The better part of air will not condense at this temperature) |
| Lines 20-26 were replaced by lines 25-51 |
| - * Pump down and flush again with He gas, then pump down to a pressure between 10 and 50 mbar. |
| - |
| - !Cool down |
| - |
| - There are two possibilities, each has advantages and drawbacks. |
| - |
| - *With He pump |
| + * Pump down and flush again with He gas. To remove all contaminants you should repeat this procedure an infinite number of times (at least 2x). |
| + * If you cannot reach 0 mbar (or -1 bar) on the mechanical gauges you might be faced with a leak into the sample chamber or with an offset on the gauge. |
| + * Pump down to a pressure between 10 and 50 mbar. |
| + |
| + !Cool Down |
| + |
| + # Connect helium pump to the pumping port (P). Switch on the pump and wait until |
| + the pressure stabilizes (should be less than a few millibars). Make sure that |
| + the warm valve (W) is closed, open cold valve (C) a little, the pressure at the |
| + pump should not exceed 20 mbar (30 on a maxi cryostat). |
| + In SEA, this could be done by switching the needle valve control to automatic |
| + and set 20 - 30 for the flow maximum. |
| + # Put a setpoint of 10 K on the heat exchanger. |
| + # When the heat exchanger is at 10 K and the sample near 10 K, reduce the pressure |
| + by closing the cold valve gradually until the heating power the temperature controller |
| + needs to keep 10 K has reached a value between 100 and 200 mW. |
| + With SEA, the regulation of the needle valve is done automatically, but the value |
| + for "flow set" should be optimized if not known from an earlier run. |
| + # Put the temperature setpoint to zero. The cryostat should cool to 1.6 K within 10 minutes. |
| + If the base temperature can not be reached or the "nv_Set" is oscillating, most probably |
| + the value for "flow set" was not determined properly, and must be increased slighly. |
| + |
| + ''Cool Down with warm valve'' |
| + |
| + In principle there is the possibility to cool down with the use of the warm valve, |
| + without He pump. As this is not recommended, it is mentioned only for information. |
| + Make sure that the warm valve is always closed except for preparation. |
| Removed lines 28-44 |
| - ** Connect helium pump to the pumping port (P). Switch on the pump and wait until |
| - the pressure stabilizes (should be less than a few millibars). Make sure that |
| - the warm valve (W) is closed, open cold valve (C) a little, the pressure at the |
| - pump should not exceed 40 mbar (20 on the ILL cold valve controller). |
| - ** Put a setpoint of 10 K on the heat exchanger. |
| - ** When the heat exchanger is at 10 K and the sample near 10 K, reduce the pressure |
| - by closing the cold valve gradually until the heating power the temperature controller |
| - needs to keep 10 K has reached a value between 100 and 200 mW. Wait half an hour |
| - and check or change the cold valve setting again. |
| - ** Put the temperature setpoint to zero. The cryostat should cool to 1.6 K within 10 minutes. |
| - |
| - *With warm valve |
| - |
| - ** Open cold valve (C), open warm valve (W) by about 3 turns. Close the valve (R) going |
| - to the He recovery. |
| - ** When the heat exchanger and the sample temperature have stabilized around at 4.2 K, |
| - close the warm valve and reopen a little bit, just enough to held 4.2 K. |
| Line 52 was replaced by lines 60-75 |
| - * Dry the sample stick. |
| + * Dry the sample stick with a hair blower (not a hot gun!) |
| + |
| + !He Flow Schematics |
| + |
| + [OrangeCryostatCooldownProcedure/NeedleValveControl.png] |
| + |
| + !Automatic Cryostat Control and Monitoring |
| + |
| + All our cryostats are monitored and controlled with [SEA|http://lns00.psi.ch/sinqwiki/Wiki.jsp?page=Sea].\\ |
| + All instruments are equipped with a temperature controller (Lakeshore 340) for the temperature control \\ |
| + and a cryostat control unit (CCU) for the control of pressures, levels and valves.\\ |
| + The CCU will only work with a correctly configured SEA instance. It can read the pressure in the Helium gas pumping line and set the needle valve accordingly.\\ |
| + It reads the analog output of AMI Helium level meters and serves as a level indicator for our 2 point liquid Nitrogen level meter.\\ |
| + The Unit is used to energize the electromagnetic valves involved in the automatic Nitrogen/Helium refill. |
| + |
| + [CCU|CCU.png] |
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