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NEC Alphatross RF Source Instructions



In the Vault

  1. LE Extension vacuum must be good as evidenced by Ion Gauge controller with orange displays on magnet.
  2. Source vacuum must be good as evidenced by Ion Gauge controller with blue displays in 19“ rack.
  3. Unground alpha source and hang shepherd's hook on concrete wall conduits, close gate.
  4. Go around and unground sputter source, hang shepherd's hook on gate, and close gate.

In the Control Room

  1. Source camera must have a view of the faraday screen on the blue box of the source head.
    1. To gain control of the source camera: On the joystick unit press “2” then “CAM” to specify the camera.
    2. Use the joystick and “TELE” or “WIDE” to create a view of interest.
  2. If not already present, launch the Alphatross software on the source computer.
  3. In prompt succession press the “on” buttons for: Water Cooling, Source Power, and He4 Gas.
    1. These actions start a 60 second timer on the RF supply and set initial conditions on the Magnet and Mass Flow Controller.
    2. After 60 seconds the RF power starts, gives a reading on the meter above the faraday screen, and hopefully the plasma will ignite giving an intense white glow. It is bright enough to illuminate the faraday screen if not looking directly at it in the mirror.
  4. Plasma or not, raise the Magnet to 4 A, maybe the plasma will ignite.
    1. Monitor the Ion Gauge pressure, it should remain less than 4 x 10-6 Torr while setting the Probe. It should settle to around 2 x 10-6 or less when done.
    2. Raise the Probe Voltage to 3 KV as a start, this might be enough to get the plasma going.
    3. If there is still no plasma try raising the Mass Flow setting to as much as .5 SCCM to inspire ignition and then return to .35 SCCM.
    4. Monitor the Probe Current, maintain 3 mA +/- 1 mA, and continue raising the Probe Voltage until it reaches 6.5 KV.
  5. Set the Oven Voltage to 87 V, wait ten minutes. After 10 minutes the Oven Temp should be around 150 C.
  6. Set the Extractor Voltage to 5.5 KV and the Bias Voltage to a value that gives the desired injection energy less (6.5 + 5.5). Beam yield seems to increase with injection energy above 30 KeV. Suggest trying 41 or 53 KeV settings if pulsing.
    1. You may now be able to look at negative beam in the source faraday cup (#7 on the FC meter). Its not clear if this is a useful endeavor.
    2. Beam yield will increase as Mass Flow is reduced, expect optimum yield at around .2 SCCM.
    3. Optimize negative beam yield by tuning Extractor Voltage, Focus Voltage, and Mass Flow. Adjust Bis Voltage accordingly if an exact injection energy is required for P&B. Expect little or no Focus Voltage.
  7. Use software buttons to take out faraday cup and open gate valve.
  8. Set Lens A to 10 KV and source Einzel Lens to 15 KV initially and use the inflection magnet to pass beam on to the LE faraday cup. Tune both lenses and magnet for optimum conditions. The BPM may be useful too.
  9. You may need to re-tune with Extractor, Bias, and Focus Voltages and Mass Flow setting. Each voltage tune will affect the inflection magnet.
playground/alphatross.1584476082.txt.gz · Last modified: 2020/03/17 16:14 by jacobs