Accelerator Handbook

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playground:pulsing

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playground:pulsing [2009/03/04 15:46] – external edit 127.0.0.1playground:pulsing [2026/06/25 16:12] (current) – external edit 127.0.0.1
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 === Accelerator Start-Up - Chopping and Bunching === === Accelerator Start-Up - Chopping and Bunching ===
 +
  
 ** Starting and Tuning Pulsed and Bunched Beam ** ** Starting and Tuning Pulsed and Bunched Beam **
  
-   1. Start up source and described in the [[playground:sputter|Sputter Source]] or [[playground:alpha|Duoplasmatron Source]] instructions. +   - Start source as described in the [[playground:sputter|Sputter Source]] or [[playground:alpha|Duoplasmatron Source]] instructions. 
-   2. With the low energy cup in, tune for maximum current using the inflection magnet, two einzel lenses, and the steerers 2X, and 2Y.   +   - With the low energy cup in, tune for maximum current using the proper tuning devices for the given source.   
-   3. Set auxiliary width at maximum. +   - Set auxiliary width at maximum (100). 
-   4. Turn on oscillator -- beam current will drop.   +   - Turn on oscillator -- beam current will drop. 
-   5. Turn 2Y down -- look for peak in pulsed beam (its easier to find the correct peak if the auxiliary width is large).    You should normally expect to find the peak somewhere around 4.0  if you start from  5.0 .    If you reduce 2Y (after a D.C. tune-up) , the first peak you see is the correct one. +   - Switch to f/1 
-   6. Adjust 2X for maximum current for the maximum current.   You usually need to adjust both 2Y and 2X together to find the maximum. +   - Turn "chopper power" on. 
-   6. Change  to f/2. Adjust the chopper phasing for maximum current.  The beam current should drop by a factor of 2 if you are on the proper peak.   For best current tune both the 2X and chopper phasing. +   - Turn buncher on. 
-   7. Adjust chopper phase for maximum current on the Output Meter. +   - Turn 2Y down -- look for peak in pulsed beam.  When you see 10% rise in LE current, adjust chopper phase for maximum LE current then continue dropping 2Y until first maximum is seen in LE current.  You should normally expect to find the peak somewhere between 5.0 and 3.0 .    If you reduce 2Y (after a D.C. tune-up) , the first peak you see is the correct one.  If you continue to reduce 2Y you will see the retrace peak.  You should return to the first peak if you locate the second (lower 2Y) peak. 
-   8. Turn "chopper power" on. +   - Adjust 2X for maximum current for the maximum current.   You usually need to adjust both 2Y and 2X together to find the maximum. 
-   9. Turn buncher on. +   - Check the list of previous chopper and buncher settings that is kept on the right side of the alphatross source monitor terminal.  If there exists a set of previous buncher and chopper settings that are similar to your experiment, set them in the controls now. Change to f/2. Adjust the chopper phasing for maximum current.  The beam current should drop by a factor of 2 if you are on the proper peak.   For best current tune both the 2X and chopper phasing. 
-  10. Bring amplifier plate to 1 keV for for deuteron or protons, 0.2-0.4 keV for He-3 and He-4, and 0.5-0.75 keV for Li-7. +   - Bring amplifier plate to 1 kV for for deuteron or protons, 0.2-0.4 kV for He-3 and He-4, and 0.5-0.75 kV for Li-7. 
-  11. Adjust buncher phase for maximum current. +   - Adjust buncher phase for maximum current. 
-  12. Peak buncher output current with "buncher output" by cranking the tuning knob. +   - Adjust buncher tuning for peak output current by cranking the tuning knob. 
-  13. Get high energy end of the accelerator going. +   - Proceed to the high energy cup and tune beam. 
-  14. Adjust low energy steerers to maximize the beam.  Try to run the steerers as low as possible and avoid doglegs. +   - Adjust low energy steerers to maximize the beam.  Try to run the steerers as low as possible and avoid doglegs. 
-  15. Adjust the "GRIDDED VOLTAGE TUBE LENS" to maximize the current.   Note that this has a slow response time. +   - Adjust the "GRIDDED VOLTAGE TUBE LENS" to maximize the current.   Note that this has a slow response time. 
-  16. Get beam through the analyzing magnet following steps in the Machine Setup steps 11-13 above. +   - Send the beam on thru the Pick Off you intend to use. 
-  17. Make sure proper doors are closed, and target cooling, etc. are on and take the beam into the target area. +   - Adjust H.E. steering, quads, tweaking magnet, etc. to maximize beam current. 
-  18. Adjust H.E. steering, quads, tweaking magnet, etc. to maximize beam current. +   - Adjust auxiliary width for beam current; this will affect both beam current and timing and will need to be set when the final timing is set.   
-  19. Notice beam pick-off repetition rate;  if you have adjusted the chopper and buncher properly it should read 500,000 at f/1. +   - Examine beam pick-off repetition rate;  if you have adjusted the chopper and buncher properly it should read the proper frequency for the f/n you are using.  [[See the repetition rate list]]. 
-  20. Put the cup in, then put gold foil in, then take out cup.  Look at TAC output.  Adjust chopper phase, buncher phase and amplifier plate to obtain best time tune. +   - Send the time-tuned beam to target 
-  21. Take out gold foil.  Run time-tuned beam.+   - Make final adjustments as necessary using detector timing if needed 
 + 
 +{{playground:pulsing.pdf|Original HVEC Pulsing and Bunching instruction manual.}} 
 + 
 +{{playground:chopper_howo.pdf|Instructional diagram about chopper operation}} 
 + 
 +{{playground:buncher_howto.pdf|Instructional diagram about buncher operation}}
  
 +{{playground:bpo.pdf|Instructional diagram about beam pickoff operation}}
  
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