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