Difference between revisions of "Thermal Equilibrium Measurement Procedure"

Revision as of 02:00, 16 March 2012

This procedure was created for GEN, and must be updated to reflect changes in the target for g2p.

TO aid in the TE calculation, use the "te_getter.pl" script in the g2p_te folder on poltarg2p2.

Changes for g2p: Set the run valve to a reasonable value, close to the setpoint chosen by the PID. 65% to 90% is a bit too much for this fridge.

Software

To aid in the TE calculation, use the "te_getter.pl" script in the g2p_te folder on poltarg2p2. This script reads the last 'x' data entries before unixtime 'y' (default is current time). It produces a datafile for these points and asks if you'd like to use them in a TE measurement. Then it performs the TE calculation and returns the results.

Assumptions:

• NMR System is tuned
• Magnet is at full field, persistent mode, leads are ramped down
• Nose is full, run valve in manual mode

Prepare Fridge:

• Stop RB3, RB2, and RB1 (wait 2 mintues between each), if necessary
• Put Run Valve, EV91120, in Manual Mode
• Establish a STEADY Nose level somewhere between 50-65%
• Try 0.17 on the run valve.
• If needed only make slight changes to Run Valve for rest of TE (+/- 0.05 each 10 min)

Take a Baseline:

• Hit "Unlock Magnet Controls" button
• Type the full-field current in the box labeled "Setpoint" (eg: 60.882)
• Type 3.00 into "Setrate" box, if necessary
• Hit "To Setpoint" Button
• Wait for leads to reach full current (approx 1 min)
• Hit "Hold"
• Check that leads current and magnet current are equal
• Hit "Heater On" button
• Wait for the 30 second timeout to expire
• Type the baseline current into the "Setpoint" box (eg: 59.882)
• Hit "To Setpoint" to start the magnet sweeping
• Wait for magnet to reach baseline current (approx 6 min)
• Hit "Hold" button
• Put NMR into pause mode if necessary
• Hit the Baseline button
• Select "Create New Baseline", dialog box should then disappear
• Change sweeps to 2000 if necessary
• Double check that all NMR settings are where you want them
• Hit "One Point" button to take a single nmr measurement
• Wait for timer to count down
• Hit Baseline button
• Select the baseline you just took from the list of timestamps
• Document the details of the baseline in the logbook:
  • Date Time, #Sweeps, MagCurrent, Top/Bottom, Gain, RFFreq, RFMod
• Type full-field current into "Setpoint" box (eg: 60.882)
• Type 3.00 into "Setrate" box, if necessary
• Hit "To Setpoint" button
• Wait for magnet to reach full current (approx 6 min)
• Hit "Hold" button
• Hit "Heater Off" button
• Wait for 30 second timeout to expire
• Hit "To Zero" to ramp the leads down
• Hit "Lock Magnet Controls" button

Take TE measurements:

• Make sure ladder is in desired target position
• Make sure NMR is on desired channel (AND in agreement with target position!)
• Set sweeps to 1000, if necessary
• Hit "Take Data" button
• Wait for timer to count down
• Make sure you have a STEADY Nose level with roughing and bypass valve closed
• Use ~0.17 on the run valve (watch the nose temps.)
• Write the following in the logbook for the next 10 measurements:
  • Time, NMR Area, 4He Press, 4He Temp, 3He Press, 3He Temp, Nose Level
• Watch data until it flattens out, if in good warm steady state ~1.5K for a while should be less than 30 minutes.
• calculate the TE calibration constant using poltar@poltarg2p2~/g2p_te$./te_getter.pl 15
• Put new Cal. Const. in under Sweeps in PDP and move on to prepare fridge for polarization