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Latest Results on HXRSS at LCLS
Franz-Josef Decker 4-Feb-2013
1. Seeding with 004, 220 and over-compression
2. Tuned beam with slotted foil cutting horns
3. Energy spread energy jitter undulator acceptance
4. Up to 300,000 counts on FEE spectrometer (0.7 mJ)
with multiple spikes
2Insert Presentation Title in Slide Master
Hard X-Ray Self-Seeding at LCLS (HXRSS)
Bragg 004
Laue 220
3Latest Results on HXRSS at LCLS
Different Mode of Operation
1. Blue: “Background” SASE with delay, crystal out
2. Red: Seeded 220 (tuned)
3. Green: Seeded 004
4. Magenta: Seeded 220
over-compressed
(less SASE?)
Typical:
220: 0.8 eV
004: 0.5 eV
220 o-c: 2.0 eV
SASE: 20.0 eV (Spectrometer cuts to 11.0 eV)
4Latest Results on HXRSS at LCLS
To avoid tuning up on the horns: Cut them with Slotted Foil
Foil out Foil in (tuned)
100 shots
SASE
1 shot
Additional peak
5Latest Results on HXRSS at LCLS
Gas detector: FEL intensity vs time
• Slotted foil: out and in
• 0.2 to 0.70 mJ 0.0 to 0.4 mJ
(SASE) or multiple spikes ?
6Seeding with Slotted Foil in
Correlation Plot Data with Spectrometer Profile (Foil in)
• Peak (= area/sigma*2.5)
vs x (= photon energy)• Peak vs x (= e-beam
energy)
7Insert Presentation Title in Slide Master
Three Different Energy “Widths”
• DL2 wire scan: 0.040%• DL2 energy jitter: 0.036%• Undulator acceptance: 0.032%
all about the same
Need to reduce E-jitter or increase acceptance (0.22-0.042% ?)
0.040%
Warning: “smoothed” data
8
Gain: Seeded / SASE: 3.4 / 2 / 0.7 = 2.4 (0.7 FEE spectrometer throughput)
Latest Results on HXRSS at LCLS
Seeding vs. SASE with Si(111) in XCS (Aymeric Robert)
Seeded up to 1mJ, 11-Jul-2012
9
Summary
• Seeding with 004, 220, and over-compressed beam• Cutting horns with BC2 slotted foil, • Up to 300,000 counts peak on spectrometer single shots • Up to 140,000 counts average (100 shots) • Multiple spikes might be cause for elevated gas detector• Energy spread, energy jitter, undulator acceptance: 0.035%• Laser heater is necessary (or: <10% FEL intensity)
Latest Results on HXRSS at LCLS
10Insert Presentation Title in Slide Master
Backup Slides
• Six double pulses in a row, what causes the shifts?
11Seeding with Slotted Foil in
Spectrometer peak show different picture
• Gaussian peak of fit:• Foil out: 130,000 counts Foil in: 170,000 counts
12
SASE plus start of seeding
Latest Results on HXRSS at LCLS
• Seeded light is about one sigma off in x (y here)• There is generally
some offset with
SASE lines too,
looking at the lower
half and trying to
guess the upper
part is flawed
Seeded
13Seeding with Slotted Foil in
BSA Jitter Data, and more
• Gas detector (FEL intensity) versus DL2 e-beam energy
starts to show elevated middle
• Spectrum Energy FWHM versus BC2 peak current
14Latest Results on HXRSS at LCLS
a) “User” energy: here spectrometer: 8.45 keV
b) Beam energy to read 8.45 keV
(and SASE in screen, full power not documented)
c) Crystal Bragg angle scan
Peak at 55.113º or 55.15º,
where to tune up?
Optimize horns or center
of longitudinal distribution?
Getting Three Energies Right
15Seeding with Slotted Foil in
Some Tuning of Spectrum Peak
• Peak on L1S phase• Peak (+FWHM) on beam energy
Beam Energy
16Latest Results on HXRSS at LCLS
Where to start tuning?
• Bragg angle at• 55.113 deg (horn?) 55.150 deg (E more
centered)
DL2 energy DL2 energy
17Latest Results on HXRSS at LCLS
To avoid tuning up on the horns: Cut them
• Slotted foil in to widest place (-10500 um)
18Seeding with Slotted Foil in
Procedures: RF kicks measurements
• “Amount of RF
Foil out Foil in
1 shot
100 shots
SASE