Difference between revisions of "UITF Notes"

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−
== Random ==
+
== 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
  
−
* Harp axis calibration does not matter: It only changes the measured emittance but not alpha/beta, and its effect does not depend on the quad in use.
+
== keV beam time ==
−
* Adding reasonable quadrupole moments to correctors is not enough to explain the inconsistency. It would need an extra quad with K1 ~ 5.
+
* LVQE scan at different voltages. Expect same result, provided different laser powers at same voltage give same result (avoid SCL).
−
* At dp/p = 1e-3 (which is higher than what we observe unless the measurement is flawed), seeing significant inconsistencies in the quad scans needs a dispersion of many cm. In y, the only dispersion in this part of the lattice should come from the earth's field; this gives about 8 mm at the harp, much too low to see anything.
+
** 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 [https://logbooks.jlab.org/entry/4022870 mains-harmonic BPM signals] as a function of parameters (buncher etc.)
 +
* Measure bunch length upstream (chopper or Brock)
  
−
== For future study ==
+
== Random things to change when it makes sense ==
−
* Provided the BPMs work at all, we can use the 701 and 702 BPMs to better measure the momentum jitter. The CW waveforms give time-domain data in 900-microsecond-long windows with 16384 samples each, i.e., ~ 18 kHz sampling rate, 9 kHz analog bandwidth. More than enough to see all peaks, maybe even a little much to resolve them well. The only problem is, we can only run 100 nanoamps CW into that line. See if that's enough to see anything.
 
  
−
== Take home ==
+
* The way MFQK403 is supposed to focus into both Aperture A4 and the booster is flawed for multiple reasons:
−
* Current picture of ITVM703 to make sure width/height is still what it was
+
** 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.
−
* 703 harp file, e.g., /cs/data/harpData/IHAM703/IHAM703.10262021_18:....
+
** 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.
−
* using 703 harp, measure momentum spread vs. something interesting, e.g., buncher amplitude
+
** 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 13:43, 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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