How to Perform an NMR Measurement

• Alert your shift leader you intend to take an NMR Measurement
• Tell MCC that you intend to perform an NMR measurement and they need to turn the beam off and mask FSD for the target. Wait for them to call back and say that the beam is off.
• If the transverse lasers are on, turn them off according to the ``How to turn the lasers on and off'' section.
• If the holding field is at 90 or 270 degrees, you have to rotate the field to zero degrees to do an NMR measurement. In 0 or 180 degrees no rotation is necessary. Please follow the directions in the 'How to Rotate the Holding Field section.' You can move the target into the Pick-Up Coils position while the field is rotating.
• Follow the procedure 'How to Move the target' to move the target to the Pick-up coils position.
• It is necessary that the temperature be stable for the NMR to be valid. If you are in longitudinal mode then this usually isn't a problem, since you can simply leave the lasers on through the whole process. If you have rotated from transverse, make sure you wait until the temperature stabilizes (around 15 minutes from the time you turned the lasers off).
• Once the target is in the Pick-Up Coils position and the field is in the proper direction and the temperature is stable, click on the button next to NMR Settings.
• The NMR Settings panel should appear. Fill out all the sections framed in yellow as follows:
  • Operator Name - Your Name.
  • Latest Run Number - The run number of the last run
  • Switches - Three switches must be set to take a good measurement. The rotation box switch (in the panel on the right of the control computer) must be ON. The field rotation chassis (also on the right, a couple of panels above the rotation box) should be in BYPASS (the left most switch, labeled bypass/through). The RF Capacitor Box (to the left of the computer on the bottom) should be set to NMR.
  • Pre-Amp Settings - The pre-amp is in the target area and can't be read by the computer. It settings can be read off the Pre-Amplifier camera by an expert or someone with very good eyes. It shouldn't change, so if you can't read it just leave it as the default.
  • RF Current Monitor - This is the measurement of the RF current and will be filled in by hand during the NMR measurement.
• Hit 'Ctrl-P' to print the NMR Settings screen and retreive the print out on cha2hp the printer in the backroom of the counting house.
• To close the NMR Settings screen hit the red stop sign on the left top, then click on the X in the top right hand corner. (or hit the soon to be implemented 'Exit' button.)
• Now the 'TO Screen' program should still be running. Now click on the button next to 'Perform NMR Measurement'.
• The NMR Measurement screen should appear. Click on the 'Go' button.
• The program will let you know its okay to leave the lasers on.
• You will be asked to check the green light on the HP3324A Funtion Generator. Its on the bottom right hand corner of the Function Generator which is located directly to the right of the the control computer. If its not on, simply put the Function Generator in local mode (by pressing the 'Local' button on the bottom left hand corner of the FG) and press the Signal On/Off button located right next to the green button. The green light should now be on.
• The program will then turn the RF Current on.
• Read the the oscilloscope above the RF Capacitor Box. The RF signal should be on Channel 2. Fill in the RF Current Monitor section of the NMR Settings printout by writing the number below 'Ch2 Pk-Pk' listed on the right of the oscilloscope screen . You may have to change the vertical and horizontal scale. The output should be a sine wave about 2V Pk-Pk.
• Once you write this number down, Click on 'Ok' and the NMR Sweep will begin. It takes about 45 seconds.
• The NMR Sweep should have two peaks in each channel (corresponding to the up and down sweeps). Don't worry if they are pointing up or down, only their size matters.
• Once the NMR sweep is completed, type 'CTRL-P' to print out the output.
• Click on 'Exit' to leave the screen.
• Now that the NMR measurement is done, move the cell back into the $^{3}$HE Target position. If you need to run in 90 or 270 degree mode rotate the field back into postion using the 'How to Rotate the Holding Field' procedure. These steps can be done simultaneously
• Alert your shift leader when the cell and field are in position.
• If you are in transverse mode, turn the lasers back on according to the 'How to turn the Lasers On and Off Procedure'.
• If applicable call MCC and tell them that the target is in position and