Difference between revisions of "UITF Notes"

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== Opportunistic tests and long-term ideas off the top of my head ==
+
== MeV beam time ==
 +
* Test IHAM505
 +
* TM beam to 703 to see RF drift (full shift)
 +
* Verify optics setup for HKDL
 +
** To produce small beam at M703, first measure Twiss at 501 and then optimize beta_x with Elegant: try to make it small in the dipole AND at the harp if possible (keep the dipole from focusing)
 +
* Repeat buncher study, booster crested, 8 MeV, multiple scans per point
 +
** It may be interesting to do the buncher study with the 7-cell off.
 +
** This reduces microphonics impact, but optics of the low-energy beam are a problem
 +
** Crank 2-cell up?
 +
* Buncher power vs. GSET
 +
** Once correct buncher power is found, measure displacement at +/- 90 degrees on K501 again
 +
* Test booster off crest, scan buncher if results good
  
−
* Make sure we know which peak is which in the harp scans (make beam spot asymmetric and compare with viewer).
+
== keV beam time ==
−
* Readjust buncher amplitude by minimizing p spread on 703?
+
* LVQE scan at different voltages. Expect same result, provided different laser powers at same voltage give same result (avoid SCL).
−
* Measure p spread on 703
+
** Results are different, don't know if related to instrumentation (battery resistance etc.) or physics. If it's physics:
−
* Float gun-energy beam to 703 to verify MDLM601 calibration. Not sure if possible, but worth trying. Detune both cavities, use BPMs liberally.
+
*** CST: Does thermal energy affect collection efficiency?
−
* Have the intermittent RF instabilities fixed
+
*** Ion current? probably too low to matter
−
* Measure how much juice the BPMs need for reliable positions, particularly in the keV region
+
*** Try adjustable bias voltage source (Keithley)
−
* Is there anything we can learn from the BPMs / correctors to supplement the gun kick study at CEBAF?
+
* HVQE scan at different voltages. Expect different result.
−
* Implement QE tool per Joe's request. Got shopping list from Michele
+
* High current to FC2 for 12+ hours, check if drift is gone. Check with buncher ON and buncher OFF.
−
* It would be nice to have an extra corrector before the booster to get a nicer axis through both cavities. Prefer the duct-tape variety to nothing at all
+
* Look at [https://logbooks.jlab.org/entry/4022870 mains-harmonic BPM signals] as a function of parameters (buncher etc.)
−
* Permanently incorporate prep chamber stuff into EPICS
+
* Measure bunch length upstream (chopper or Brock)
−
** stalk heater PS, temperature readback, ion pump current, anode current. Consider protection logic to disable heater if pressure or temp gets too high. Add oven timer. It should automagically post a completion notice to UITFLOG.
 
−
** maybe also an EPICS-switchable DC voltage for the auxiliary laser diode (replaces manual "beam shutter")?
 
−
** have a second PS for the dispenser; could be remote-controlled or not, don't really care... we can't automate the whole process anyway because of the manual valve
 
−
* Can we get decent, auto-aligning corrector mounts throughout the machine? The multipole moments are currently uncontrollable, presumably large, which is a bigger deal than one might think because the beam line alignment also looks terrible.
 
  
−
== Preparation for HKDL ==
+
== Random things to change when it makes sense ==
  
−
* The keV emittance can be measured at 501 provided intrinsic energy spread is negligible (buncher off).
+
* The way MFQK403 is supposed to focus into both Aperture A4 and the booster is flawed for multiple reasons:
−
* qsUtility lacks harps to directly measure the optical functions prior to M601, especially directly before and after the booster. Need to measure them at M601 for a few suitable beam energies and backpropagate to M401 in preparation for simulations of the HKDL optics.
+
** The lens would need to produce multiple waists (DP can, A4, Brock cavity, RM11), so the focal length is a compromise. But interestingly, it is the same at CEBAF.
 +
** The orbit needs to be very straight for the beam to make it all the way downstream, but to adjust this, we need both upstream correctors, 401A and 402, so centering in the lens at the same time is very difficult.
 +
** We should do a GPT study and play with a potential extra lens, but I would intuitively suggest something like this:
 +
*** Remove Brock cavity, not needed
 +
*** Add corrector between MFQK403 and A4
 +
*** I think having the beam converge slowly into the booster is good, so I like that the lens is far away. Maybe the aperture should just be closer to the booster? At the very least, put it behind the BPM so we can see where we're at.
 +
* MFAK303 has a similar problem. Being single-wound, it is supposed to be equal and opposite to MFAK301, but this fixes its focal length, while it is supposed to focus in both the buncher and the dipole. This issue does not seem critical, but it could be pondered sometime.

Latest revision as of 14:43, 12 November 2022

MeV beam time

  • Test IHAM505
  • TM beam to 703 to see RF drift (full shift)
  • Verify optics setup for HKDL
    • To produce small beam at M703, first measure Twiss at 501 and then optimize beta_x with Elegant: try to make it small in the dipole AND at the harp if possible (keep the dipole from focusing)
  • Repeat buncher study, booster crested, 8 MeV, multiple scans per point
    • It may be interesting to do the buncher study with the 7-cell off.
    • This reduces microphonics impact, but optics of the low-energy beam are a problem
    • Crank 2-cell up?
  • Buncher power vs. GSET
    • Once correct buncher power is found, measure displacement at +/- 90 degrees on K501 again
  • Test booster off crest, scan buncher if results good

keV beam time

  • LVQE scan at different voltages. Expect same result, provided different laser powers at same voltage give same result (avoid SCL).
    • Results are different, don't know if related to instrumentation (battery resistance etc.) or physics. If it's physics:
      • CST: Does thermal energy affect collection efficiency?
      • Ion current? probably too low to matter
      • Try adjustable bias voltage source (Keithley)
  • HVQE scan at different voltages. Expect different result.
  • High current to FC2 for 12+ hours, check if drift is gone. Check with buncher ON and buncher OFF.
  • Look at mains-harmonic BPM signals as a function of parameters (buncher etc.)
  • Measure bunch length upstream (chopper or Brock)

Random things to change when it makes sense

  • The way MFQK403 is supposed to focus into both Aperture A4 and the booster is flawed for multiple reasons:
    • The lens would need to produce multiple waists (DP can, A4, Brock cavity, RM11), so the focal length is a compromise. But interestingly, it is the same at CEBAF.
    • The orbit needs to be very straight for the beam to make it all the way downstream, but to adjust this, we need both upstream correctors, 401A and 402, so centering in the lens at the same time is very difficult.
    • We should do a GPT study and play with a potential extra lens, but I would intuitively suggest something like this:
      • Remove Brock cavity, not needed
      • Add corrector between MFQK403 and A4
      • I think having the beam converge slowly into the booster is good, so I like that the lens is far away. Maybe the aperture should just be closer to the booster? At the very least, put it behind the BPM so we can see where we're at.
  • MFAK303 has a similar problem. Being single-wound, it is supposed to be equal and opposite to MFAK301, but this fixes its focal length, while it is supposed to focus in both the buncher and the dipole. This issue does not seem critical, but it could be pondered sometime.
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