HEBT Tuning

HEBT setup/tuning may begin after beam development for the cyclotron is complete to FC2007. The primary goal is to establish a uniform, square beam on the external viewer D2197. This is done by transporting the beam to a copper foil located at D2069 which scatters the beam, using focusing elements to manipulate the beam size and uniformity, then inserting 4-jaw slits at D2174 to define the beam size.

These are recommendations for setting up the HEBT for a new beam (ie new cocktail). There may be more work necessary than is listed below

• Scale the HEBT from a previous cocktail.
• Sending beam to FC2192 and/or viewer at D2191 and tweak the HEBT dipoles to maximize the current/center beam position on viewer. It may be useful to open the 4-jaw slits to see the entire beam on the viewer.
• If possible, use vertical correctors in the HEBT section before the dipoles to adjust the vertical position of the beam

• It may be useful to quad center in the HEBT section before the dipole. The beam out of the cyclotron is not always at the same position or with the same angle.
  • One can use the D2002 and D2010 correctors to quad center while sending beam to viewer D2040. You can also send beam to the stub faraday cup D2065 and use the same correctors to maximize the current. This may help if the starting point is very far off.
  • After quad centering, send beam to D2191 viewer and use the HEBT dipoles and vertical corrector D2038 to re-center

• After centering is decent, evaluate whether focusing elements need to be adjusted.
  • Send beam to internal viewer D2191, open the 4-jaw slits (all 40mm), and observe the beam image. The beam should cover the majority of the viewer and be relatively uniform near the center. The edges of the beam may be much brighter, this will be cut away by the 4-jaw slits.
  • Adjust the focusing elements to produce good uniformity in the center. Beam should be roughly symmetrical in both directions. Recommend to start by adjusting quads in HEBT section, as it is expected that the beam out of the K500 may be slightly different.
  • It may be necessary to readjust correctors/dipole to re-center the beam due to quad steering

• Restore slit positions from a previous run. Measure the beam on FC2192 and calculate the flux. Adjust intensity as necessary to stay within safe flux levels through the window
• Send beam to external viewer D2197. Adjust the slit positions to produce the largest square possible without hitting the exit flange of the beamline. The flange is 50 mm diameter, so the square should be close to 35x35mm.
• Use Viola to measure the beam size and adjust slits accordingly. It can be useful to open the slits wide open to see the outer edge of the beamline, then insert slits one by one.

When changing between beams within a cocktail, the HEBT should require less adjustment. So far we have observed that the beam size and uniformity remains quite similar by leaving the focusing elements and slits unchanged. It is necessary to adjust the HEBT dipoles to recenter the beam horizontally, and to adjust vertical correctors. This can be done on the internal viewer while trying to maximize the uniformtiy.