Accelerator Handbook

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    playground:alphatross

    NEC Alphatross RF Source Instructions

    START UP

    In the Vault
    1. Verify LE Extension Vacuum - indicated by Ion Gauge controller with orange displays on magnet.
    2. Verify Source Vacuum - indicated Ion Gauge controller with blue displays in 19“ rack.
    3. Unground alpha source and hang shepherd's hook on concrete wall conduits
    4. Close Alphatross gate and verify interlocks OK by observing indicator light.
    5. Set buncher tube selector switch - see Buncher Setup and Use
    6. Unground sputter source [optional], hang shepherd's hook on gate.
    7. Close Sputter source 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. Pressing “6” followed by “Call” will move and zoom the camera appropriately.
    2. If not already present, launch the Alphatross software (Version 6.0) on the source computer.
    3. Press the “on” button for Water Cooling. The water cooling system:
      1. operates independently of the source and the HV interlocks.
      2. contains a flow switch that must be closed in order to start the source.
      3. provides heat to prevent Rb freezing.
      4. provides cooling to the magnet in the source.
    4. In prompt succession press the “on” buttons for: 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. A dim neon light will illuminate behind the Faraday screen on the source box.
      3. After 60 seconds the RF power starts. This:
        1. gives a reading on the meter above the Faraday screen
        2. may ignite the plasma giving an intense white glow.
    5. Raise the Magnet to 4 A (may ignite the plasma).
    6. If the plasma has not ignited
      1. Raise the gas flow until the plasma ignites. This should be less than 1 SCCM in most instances.
      2. Quickly lower the gas flow back to 0.350 SCCM (or your desired operating rate).
    7. Set the probe voltage by:
      1. Monitoring the Ion Gauge pressure.
        1. it should remain less than 4 x 10-6 Torr.
        2. Operating range is around 2 x 10-6 or less.
      2. Raise the Probe Voltage to 3 kV.
        1. Check probe current to insure that it is less than 4 mA.
      3. Continue raising the probe voltage to 6kV.
        1. Maintain probe current less than 4mA. High probe current may indicate:
          1. Source is still grounded.
          2. Source is dirty and requires service.
    8. Set the Oven Voltage to 80 V.
    9. Set Extractor Voltage to 5kV.
    10. Set Bias Voltage to a value that gives desired injection energy. Typical values are at least 53keV.
      1. Injection energy is displayed in the upper window.
      2. Injection energy is the sum of Probe, Extractor, and Bias voltages.
      3. Beam yields improve above 30 keV.
    11. Set the Focus Voltage to 5.5 kV
    12. Set the Faraday cup meter to position 7 (Alphatross cup).
    13. Tune for maximum stable beam.
      1. Primary adjustment at this stage seems to be focus voltage.
      2. Current may be on the order of 30 μA.
    14. Set Einzel Lens to 20 kV.
    15. Wait until the Oven Temperature is at least 160 C, 10 - 20 minutes.
    16. Tune for maximum stable beam using
      1. Focus Voltage
      2. Mass Flow - optimum around 0.25 SCCM.
      3. Verify injection energy is at desired value.
    17. Open source gate valve.
    18. Take our source Faraday cup.
    19. Move FC selector switch to position 1 (LE cup)
    20. Tune beam into FC
      1. Set inflection magnet (typical values are around 1.2 A)
      2. Typical beam currents at this stage are around 500 nA.
    • Oven Voltage can be increased to give additional beam current. It IS possible to boil all of the Rb out of the oven. When this happens, the oven temperature will rise and the chamber temperature will fall. Decrease the oven voltage and allow Rb to accumulate within the oven.

    SHUT DOWN

    1. Click the software button “Automatic Shutdown”
    2. Confirm you wish to quit by answering “y”
    3. Walk away.
    4. Do not open the source gates until the process is finished
      1. This process puts in the cup, closes the gate valve, and shuts down the source as things cool to proper levels.
      2. The automated process can be stopped by clicking the “Automatic Shutdown” again.
    playground/alphatross.txt · Last modified: 2022/06/08 09:05 by leblanc

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