Molecular Structure Laboratory Instrument Operation

1. Older-style generator (P31, P32)
2. Simply turn the knobs below the kV and mA meters counter clockwise.
3. Newer-style generator (P51)
4. This is done by holding Mode button down and hitting the down (or up) arrow until either the "kV =" or "mA =" display appears; then release the Mode button and hold the Edit button while hitting the down arrow until the desired value is entered.

1. Older-style generator (P32, P31)
   1. Check that the voltage and current adjustments are at their lowest settings. (20 kV, 5 mA)
   2. Turn on the power to the X-ray generator.
   3. Slowly increase the voltage and current settings until the appropriate values are reached. Alternate increases between voltage and current. If the X-ray tube has not been used recently allow at least 15 minutes between each voltage/current change. If the tube has been used recently, 2 minutes should be sufficient each between voltage/current change. If the needle on the current meter fluctuates between adjustments, then the X-ray tube is gassy, and the voltage/current changes should be made with at least 10 minute intervals between adjustments. The product of the final voltage and current should not exceed the maximum power load marked on the top of the tube. The recommended voltage and current values are shown on each X-ray generator.
   4. If the X-ray generator will not turn on check the following:
      1. Hold the X-ray On button in until the voltage needle increases to 20 kV.
      2. If the voltage meter does not change after 1 minute, there is a serious problem with the generator--get help.
      3. If the current meter reads 0 mA there is a serious problem with the system--get help.
      4. If the voltage meter returns to 0 kV when the X-ray On button is released, there is a problem with the safety circuit. Check that the X-ray On lamps on top of the tube and in the cabinet door interlock are working. Check that the lamps in the voltage and current meters are working. Check that the spinner in the water flow meter next to the instrument is spinning.
      5. If the tube power, as shown on the meters, does not increase to the values shown on the adjustment dials, there is probably a problem with the voltage regulator--get help.
2. Newer-style generator (P51)
   1. Turn the key on the generator control panel to the "I" position.
   2. On the generator control panel, depress and hold the heater button for at least 5 seconds or until the green ready lamp is lit. The heater button is the black button between the Off and On buttons.
   3. Push the On button on the generator control panel. Note that the LCD display should now read "kV = 20 ; mA = 5".
   4. Slowly increase the voltage and current settings until the appropriate values are reached. This is done by holding Mode button down and hitting the down (or up) arrow until either the "kV =" or "mA =" display appears; then release the Mode button and hold the Edit button while hitting the up arrow until the desired value is entered. Alternate increases between voltage and current. If the X-ray tube has not been used recently allow at least 15 minutes between each voltage or current change. If the tube has been used recently, 2 minutes should be sufficient between each voltage or current change. The product of the final voltage and current should not exceed the maximum power load marked on the top of the tube. The recommended voltage and current values are shown on each X-ray generator.

Turn on the gaseous nitrogen flow to the low-temperature device. The nitrogen flow should be set to about 12 SLPM for the four-circle goniometer instruments and to about 20 SCFH for the platform goniometer instrument.

Fill the small Dewar with liquid nitrogen. See specific instructions for filling Dewars at http://cic.chem.wisc.edu/crystal/notes/LN2fill.html

Turn on power to the low-temperature controller on top of the goniometer cabinet. For the instruments with four-circle goniometers, adjust the nozzle heater dials on the controller to the marked positions.

After about 30 minutes, the temperature should be stabilized, and the instrument may be used. Be sure to follow the liquid nitrogen filling instructions above to maintain the temperature during the experiment.

Turn off power to the low-temperature device controller. On the instruments with four-circle goniometers, turn the dial for the nozzle heater counter clockwise to its lowest setting.

Turn on the electrical power to the General Goniometer Control System, GGCS. Power to the GGCS should remain on at all times when possible.

Turn on the electrical power to the PC computer monitor and the computer itself. Power to the computer and monitor should remain on whenever possible.

For the instruments with charge-coupled device, ccd, detectors, turn on power to the supplemental cooler and the camera electronics unit, CEU. The FTS cooler on the instrument P32 takes about 30 minutes to achieve its running temperatures. The Neslab cooler on the instrument P51 takes about 10 minutes to achieve its running temperatures. When at proper running conditions, the CEU on P32 should show that the temperature is about -55 degrees, and the CEU on P51 should show that the temperature is about -45 degrees.