energy jitter, etc. - stanford university · 3 june 18th: sxr jitter testing new longitudinal linac...
TRANSCRIPT
Energy Jitter, etc.
Tim Maxwell, Lanfa Wang, Jim Welch, Jim Turner, et al.
June 26, 2014
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Outline
1. SXR Jitter Reduction Study on June 18th
1. Change linac config
2. Log impact on jitter and beam
2. Tweaks and issues on HXR jitter for HXRSS June 19th
1. L3 phasing impact
2. L1S Amplitude issue
3. Double Slotted Foil IH (XTCAV)
1. Preview per Yuantao’s, more to come w/ Diling
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June 18th: SXR Jitter
Testing new longitudinal linac config to reduce σδ
1) BC2 Energy
5 GeV → 3 GeV
2) BC2 R56
-24.7 mm → -27.2 mm
220 MeV, 230A 5 GeV, 1.5 kA
3) φL3
0° → -15°
4 GeV, 1.5 kA
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1) LEM’ing down L2 energy
Stepped L2 energy, LEM’d at each step
Final energy kept at 4 GeV
Stations removed along way, σδ improves
Note: First LEM (5 to 4.8 GeV) gave BC2
mag settings that did not agree with
chicane GUI. Used GUI to rescale.
Subsequent LEMs all agreed with GUI.
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2) BC2 R56 change
BC2 R56 w/ GUI: -24.7 mm → -27.2 mm
No apparent jitter impact
Corresponding φL2 observed (still 1.5 kA)
Note: CUD then displayed 3.15 GeV for
BC2 energy and -24.7 mm R56.
Calculating from 6x6 Amps/Phases says
BC2 energy = 2.9 GeV (?)
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3) L3 phase to -15°
Change L3 phase to (normal) -15°
No impact on jitter
E-loss: we’ve gone from 1.3 mJ to 1.0 mJ
(no tuning at new config)
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4) L2 phase tweak
Lanfa noted L2 phase not same as initial
After change, peak current reads 1.1 kA
(has otherwise been 1.5 kA all shift)
No noticeable impact on jitter (or GDET)
Average jitter:
σδ = 0.11% → 0.08%
27% improvement
(Goal = 0.051% @ 720 eVJ)
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Jitter Pie
Reduced sensitivity to L1S Phase and L0A Amp
More sensitive to LI29 PhaseJ
Before After
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Effect on beam: XTCAV (Lasing Suppressed)
Similar final phase space, stronger “horns”
Before After
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Effect on beam: XTCAV (With Lasing)
Similar final phase space, stronger “horns”
Before After
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Effect on beam: LTU Wire scans
Recorded and “Log Booked”, but not logged/saved (?)
Qualitatively: FWHM E-spread reduced,
significantly more “pedestal” in E profile
Consistent with horns observed w/ XTCAV
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HXR Jitter Reduction – HXRSS June 19th
Avg. jitter vs. L3 phase, σδ = 0.032% → 0.024%
25% improvement (Goal 0.027%)
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L1S Amp. trouble
Noted jitter growing over shift, from <0.03 to >0.045
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L1S Amp. trouble
1:1 corr. bad shots of L1S amplitude, “goes away” at ~2pm
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Correlating K-mono w/ beam energy
Odd correlation, Jim W. re-centers K-mono:
No noticeable E-
jitter intensity dep.
K-mono RMS
Fluct. = 37%
(avg. 2.7 Mcounts)
← (saturating)
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Jitter Summary
SXR:
• 27% improvement, primarily from BC2 energy reduction
• Additional horns seen in final beam, no big perform. hit
• No time for further optimization during shift
HXR:
• Typ. 25% jitter reduction, E-jit nominal
• HXRSS intensity appears stabilized (K-mono fluct)
• Intermittent L1S Amp. issue needs addressing
• Can monitor, but big hit to stability!
• Also appears in klys. mod. V data
• Debate of whether thyratron timing / 16 ns jitter issue
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Double-slotted foil: XTCAV
• Comparing performance to spectrometer & testing new XTCAV scripts (for DAQ data)
• Double-slotted foil (pos. = -22 mm), see foil selects diff. part of beam at diff. energy:
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Reconstructions
XTCAV analyzed, more to show after events are matched to HXR spectrometer
Wide slots Skinny slots