Cryo Probe Station
Probe Station Procedure - DC Probes
Getting ready
Get the chamber to the atmosphere by opening the valve on the back a tiny bit until you hear hissing… let that happen until you are done. (see picture for valve location - circled in red)
Make sure the system is vented and remove the big heavy lid carefully using handles putting it down somewhere safe.
Move the probes out of the way.
If the radiation shield is on, unscrew in diagonals to reduce shear force on screws/shield.
Using gloves and tweezers, remove the sample that is inside the chamber.
Place samples in probe station and adjust probes to be close to it, carefully check that they can go all the way over the samples, but make sure they don’t touch the sample to avoid thermal shock and probe damage.
Put radiation shield on (be careful as the crystal lid comes off) and screw in diagonal.
Close the station by placing the lid back on and close the valve under the probe station (same one you opened to vent the system - in red circle on the picture below)
Bring the camera over to check the orientation of the sample.
Open the Basles pylon camera viewer on the OPA computer and move the camera window to the computer monitor display for better view. Turn on the light on the small box next to the monitor and ensure the camera USB is connected to the computer (otherwise, your camera won’t capture anything).
Turn on the white box temperature controller under the computer monitor. (On/off button is in the back.)
Starting Vacuum
Go to option 23 on the vaccuum pump and make sure the turbo (motor pump) is disabled (as in picture below)
If not off (but it really should!!), double press both arrows at the same time to get into turbo menu, press left/right arrow to the “off” option, double press both arrows again to exit menu.
Press the start button (rightmost button) and apply a bit of pressure to the lid so the vacuum seals it.
Check that the lid no longer moves. Double-check to make sure the probes are separated before; the vacuum action can push them together.
Wait until it reaches 4 - 4.6E0 and the top green light (in the picture above) comes up.
Can check the pressure by going to option 340 on the pump.
Let the chamber rough out by waiting about 20-30 mins before the next step.
Once roughed out, go back to option 23 and switch the turbo on.
You should see Hz in the 309 row go up 6-7 per update.
Wait until it settles around 1500 Hz.
If doesn’t reach 1500, can come back to rough for more time to let it get clear and rough a bit more. Monitor temperature of things, if they get too hot, spin it down and try again after roughing some more.
Want to hit 1E-2 pressure - another green light will come up on the pressure reader indicating High Vacuum.
Make sure the second green light is on, then turn on (valve) process cooling water return & THEN the supply (valve). (Might already be on depending on the state of the system and OPA
Cooling/Temp controller
Turn on the refrigerator (compressor) by flipping the switch on a big blue box & wait for this to cool the probe station all the way -> the analogy is that of a battery.
Monitor temperature: Temp A is in the cryohead and will get down around 8K, Temp B is the radiation shield, and temp C is stage/sample temp; that’s what we care about.
Allow to cool ~2 hours.
In the meantime make sure the DC probes are connected to the Keithley sourcemeter & connect your computer to the Keithley.
Once it is cooled down completely (~10K for temp C) you can run IVs
Do a dummy run with software before landing probes, just to make sure you are talking to Keithley.
Once the temperature is stabilized, wait ~5 minutes for the sample to stabilize at that temp as well.
Move probes over into position over desired device(s) - will see on camera. Lower them down until you see them start to slide forward, that is an indication that they are making contact. Do not let the probes hit each other!
Put on a small purple block over the window to take a dark measurement.
Take the measurement with the Matlab code. (Ask group members/or maybe will post it here).
To go to other temps, raise probes, then hit C, setpoint, enter your temp, enter, escape…, and set the heater to a high/or lower range if the desired temp is closer. You should also set B to the same temperature as well.
Again, once the temp stabilized, wait ~5 minutes for the sample to stabilize at that temp as well.
Repeat for as many measurements/temps as needed.
When Done
Turn off the compressor, then the water supply (valve), then the water return (valve).
Wait for the temperature to be above 273K before turning the pumps off (motor/turbo first and then roughing pump).
Water freezes at 0C = 273K & you don't want moisture freezing in there.
Let vacuum spin down, once spun down turn off the heaters.
Open valve under the probe station, remove the lid and radiation shield (store safely/put away in the cabinet)
Remove the sample and clean your station.