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--- playground:alphatross [2020/06/16 15:52]
carter
+++ playground:alphatross [2022/01/31 11:57]
leblanc Typos
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-==== NEC Alphatross RF Source Instructions ====
+====== NEC Alphatross RF Source Instructions ======
-**  __START UP__ **
-** In the Vault **
+=== START UP ===
-  - LE Extension vacuum must be good as evidenced by Ion Gauge controller with orange displays on magnet.
+== In the Vault ==
-  - Source vacuum must be good as evidenced by Ion Gauge controller with blue displays in 19" rack.
-  - Unground alpha source and hang shepherd's hook on concrete wall conduits, close gate.
-  - Go around and unground sputter source, hang shepherd's hook on gate, and close gate.
-** In the Control Room **
+  - Verify LE Extension Vacuum - indicated by Ion Gauge controller with orange displays on magnet.
+  - Verify Source Vacuum - indicated Ion Gauge controller with blue displays in 19" rack.
+  - Unground alpha source and hang shepherd's hook on concrete wall conduits
+  - Close Alphatross gate and verify interlocks OK by observing indicator light.
+  - Set buncher tube selector switch - see [[playground:buncher|Buncher Setup and Use]]
+  - Unground sputter source [optional], hang shepherd's hook on gate.
+  - Close Sputter source gate.
+== In the Control Room ==
   - Source camera must have a view of the faraday screen on the blue box of the source head.
     - To gain control of the source camera: On the joystick unit press "2" then "CAM" to specify the camera.
     - Use the joystick and "TELE" or "WIDE" to create a view of interest.
-  - If not already present, launch the Alphatross software on the source computer.
+  - If not already present, launch the Alphatross software (Version 6.0) on the source computer.
-  - In prompt succession press the "on" buttons for: Water Cooling, Source Power, and He4 Gas.
+  - Press the "on" button for Water Cooling.  The water cooling system:
+    - operates independently of the source and the HV interlocks.
+    - contains a flow switch that must be closed in order to start the source.
+    - provides heat to prevent Rb freezing.
+    - provides cooling to the magnet in the source.
+  - In prompt succession press the "on" buttons for: Source Power and He4 Gas.
     - These actions start a 60 second timer on the RF supply and set initial conditions on the Magnet and Mass Flow Controller.
-    - 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.
+    - A dim neon light will illuminate behind the Faraday screen on the source box.
-  - Plasma or not, raise the Magnet to 4 A, maybe the plasma will ignite.
+    - After 60 seconds the RF power starts.  This:
-    - 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.
+      - gives a reading on the meter above the Faraday screen
-    - Raise the Probe Voltage to 3 KV as a start, this might be enough to get the plasma going.
+      - may ignite the plasma giving an intense white glow.
-    - If there is still no plasma try raising the Mass Flow setting to as much as 0.5 SCCM to inspire ignition and then return to 0.35 SCCM.
+  - Raise the Magnet to 4 A (may ignite the plasma).
-    - **This is a pause point for source clean up, can run like this for days, should reduce probe current over time**
+  - If the plasma has not ignited
-    - Monitor the Probe Current, maintain 3 mA +/- 1 mA, and continue raising the Probe Voltage until it reaches 6.5 KV.
+    - Raise the gas flow until the plasma ignites.  This should be less than 1 SCCM in most instances.
-  - Set the Oven Voltage to 87 V, wait ten minutes.  After 10 minutes the Oven Temp should be around 150 C.
+    - Quickly lower the gas flow back to 0.350 SCCM (or your desired operating rate).
-  - 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.
+  - Set the probe voltage by:
-    - 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.
+    - Monitoring the Ion Gauge pressure.
-    - Beam yield will increase as Mass Flow is reduced, expect optimum yield at //around// 0.2 SCCM.
+      - it should remain less than 4 x 10-6 Torr.
-    - 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.
+      - Operating range is around 2 x 10-6 or less.
-  - Use software buttons to take out faraday cup and open gate valve.
+    - Raise the Probe Voltage to 3 kV.
-  - 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.
+      - Check probe current to insure that it is less than 4 mA.
-  - You may need to re-tune with Extractor, Bias, and Focus Voltages and Mass Flow setting.  Each voltage tune will affect the inflection magnet.
+    - Continue raising the probe voltage to 6kV.
-  - The maximum Oven Temperature is around 190 C, seems to be around 91 Volts.  At this point Rb begins to escape the chamber and the beam becomes twitchy.  If the beam is unstable briefly reduce the Oven Voltage until stabile beam and return Oven Voltage to a  slightly lesser value.
+      - Maintain probe current less than 4mA.  High probe current may indicate:
+        - Source is still grounded.
+        - Source is dirty and requires service.
+    - Set Extractor Voltage to 5kV.
+    - Set Bias Voltage to a value that gives desired injection energy.  Typical values are at least 53keV.
+      - Injection energy is displayed in the upper window.
+      - Injection energy is the sum of Probe, Extractor, and Bias voltages.
+      - Beam yields improve above 30 keV.
+    - Set the Focus Voltage to 5.5 kV
+    - Set the Faraday cup meter to position 7 (alphatross cup).
+    - Tune for maximum __stable__ beam.
+      - Primary adjustment at this stage seems to be focus voltage.
+      - Current may be on the order of 30 μA.
+==**DO NOT PROCEED UNTIL CHAMBER TEMPERATURE EXCEEDS 39°C**==
+  - Set the Oven Voltage to 80 V.
+  - Set Einzel Lens to 20 kV.
+  - Wait until the Oven Temperature is at least 160 C, 10 - 20 minutes.
+  - Tune for maximum stable beam using
+    - Focus Voltage
+    - Mass Flow - optimum around 0.25 SCCM.
+    - Verify injection energy is at desired value.
+  - Open source gate valve.
+  - Take our source Faraday cup.
+  - Move FC selector switch to position 1 (LE cup)
+  - Tune beam into FC
+    - Set inflection magnet (typical values are around 1.2 A)
+    - 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__ **
+===SHUT DOWN===
   - Click the software button "Automatic Shutdown"
-  - Confirm you wish to quit be answering "y"
+  - Confirm you wish to quit by answering "y"
   - Walk away.
   - ** Do not open the source gates until the process is finished **

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