[Sneap] adjusting vertical beam exit angle on AN-2500

[Walter Augustyniak]

adjusting vertical beam exit angle on AN-2500Stuart,
    In addition to checking the source alignment at the accelerator tube head, usng the special jig, 
here is what I have to offer. I found that in our AN2500 (and likely as in yours) that the base of
the accelerator tube is mounted onto the tank base using a thick rubber gasket, which is firmed
down using 6 (I believe) L shaped "dogs" & bolts. There is never a metat to metal contact. And one can
readily "aim" the beam trajectory by favoring the tightness of some dogs over the others.
    Your problem suggests that you have tightened the upper dogs much more than the lower.
    If you believe that you have firmed all bolts to the max, then you must loosen the appropriate
ones, that is those on the top. It seems crude, but these are sensitive adjustments. On our last tube 
change ~10 years ago, I tightened just enough to get a good vacuum, then added a little more, seeing
that the head of the acc tube looked comfortably centered inside the channel provided in the 
column. However, some time later, I noticed that we were having to deflect the beam downward
with the steering plates more than usual, in order to be in the mid range of the steerers. There had been a change,
and we found that the cantilevered weight of the tube compressed the thick gasket at the base, causing 
the source end to drop and thus aiming the trajectory upwards. This implied that I was originally stingy in 
cranking down the dog bolts. 
    You can easily gauge how much you've made a change by observing the centering of the souce end in the
column structure.
    
    An added remark concerning the tank dolly. We always leave our dolly loose (barely firm) after a 
tank opening, since a very firm dolly supporting the tank will deflect the beam downwards. We can
always tell if someone has failed to loosen the dolly supports, when we note that our steerer voltages
are suddenly different. 

    Hope this helps

            Walt Augustyniak

  ----- Original Message ----- 
  From: Van Deusen, Stuart B 
  To: sneap at daytona.tunl.duke.edu 
  Sent: Thursday, November 16, 2006 1:00 PM
  Subject: [Sneap] adjusting vertical beam exit angle on AN-2500


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  Hello SNEAPers 

  I find that I need to adjust the vertical angle that the beam exits my horizontally configured AN-2500 (after some extensive repairs including re-mounting the accelerator tube, we've discovered that the beam now exits the accelerator with a downward angle greater than the beam deflectors can correct).  Adjusting the angle of the base plate with the floor mounting bolts on each leg looks pretty easy, but I'm a little concerned about getting the trolley cradles properly adjusted to accommodate the tank.  They currently bear a significant amount of the tank's weight even with the tank bolted to the base plate.  I can align the tank to the base plate the next time I open the accelerator, but I need to make the angular adjustments now, while the tank is pressurized, so that I can run a beam (after the adjustment) to check that the beam alignment.  Can anyone offer me any advice based on their experiences making similar adjustments?

  Thanks in advance. 



  ----------------------------------------------------------- 
  Stuart B. Van Deusen 
  Radiation Solid Interactions and Processing 
  Dept. 1111, M/S 1056 
  Sandia National Laboratories 
  P.O. Box 5800 
  Albuquerque, NM  87185-1056 
  PH (505)844-7782 
  FAX (505)844-7775 
  e-mail:  sbvande at sandia.gov 



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