Ion Source

Background

Herein should be a general intro to ion sources, negative ion sources and our source. A set of links should include one to National Electrostatic Corporations page on their SNICS.

Operation

Preparation

• Checks: DI water, Vacuum, Gates
• Isolating vacuum and preparing Turbo to be off
• Switching AC Power source
• Restoring vacuum
• Turning on power supplies at Table, Magnet and Source stations
• Closing the Cage
• Opening LE Tube Valve
• Turning on Cathode, Extraction and Glassman (table/injection/pre-accel power supply)

Start-up

This section has been written. We'll find it .... Or slap out a quick and dirty version:

• Ensure that the ion source drive shaft is on, vacuum is good, power supplies are on, gate is closed, LE Tube valve is open
• Ensure that the control system is running. On MasterRT.vi front panel do the rest.
• Ensure that the LE Faraday Cup is in (Green, as of 8/21/2010) and that the selector switch sends that current to the electrometer
• Ensure that the Extraction Voltage is ~15 kV, the Inflection Magnet is near a useful ion mass (1, 12 or 16 are good choices).
• Raise the ionizer voltage to 8V gradually over a few minutes. Do not exceed 22 Amps. You will observe the heating of the Tantalum by an increase in the resistance of the ionizer. OK, at the very end you may exceed 22 amps if required to reach 8V.
• Set other parameters to likely values:
  • Einzel Lens to 3 kV
  • Variable Steerer to same as Fixed Steerer
  • Ground Station Triplet X to 1.1KV and Y to 1.2KV
  • LE Steerer H to -700V and V to +1100 V (note, these units are bogus as of 8/2010)
• Once the ionizer has 8V (~175 Watts) raise the Cathode Voltage slowly. If you see rapid changes to the Extraction Voltage/current or cathode current or a decrease in the ionizer current there may be sparking. In this case, lower the cathode voltage below the sparking point and wait. Increase slowly. A good first value will be 2 kV.

Tuning

• Observe the LE Faraday Cup current on the electrometer. Note that it should be negative. Recently we have found that one must wait 15 minutes for current to appear: Don't Panic. Once current appears you can tune all of the above mentioned parameters (not the ionizer, however!).
  • If there is no current, note your starting value and scan the Inflection magnet. Hint: mass 16 will be present for any sample unless there is something wrong with the set-up.

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