1. HXRSS operation experiences at LCLS
Shan Liu, Torsten Wohlenberg
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Self-seeding Project Meeting, Shan Liu,

2. HXRSS set-up procedure and operation schemes
Outlines
HXRSS set-up procedure and operation schemes
Undulator radiation damage
Tunnel visit and technical discussions (see Torsten’s talk)
Summary and future plan
Host at LCLS: Jim Welch;
Discussions with Juhao Wu, Kun Fang, Jim Turner, Franz-Josef Decker, Alberto Lutman, Heinz-Dieter Nuhn, Yuantao Ding, Yiping Feng, John Amman, Patrick Krejcik, Mario Santana Marc Guetg, et al.;
Slides mainly from Alberto Lutman and Heinz-Dieter Nuhn.

3. HXRSS GUI Bragg reflected x-ray beam (1.49 Å) Zoomed (40 mm rms)
Courtesy of Paul Emma
Bragg reflected x-ray beam (1.49 Å)
Zoomed (40 mm rms)
Bragg angle calculation tool
(taken into account crystal calibration)
Any way to increase the image resolution?
500 hours to develop this GUI

4. HXRSS crystal calibration
9.1 keV – 7 lines crossing,Yaw = 0.8 deg, Pitch Scan
Experiment
Theory
Courtesy of Alberto Lutman
In the analytical formula have been introduced :
An initial rotation of the diamond in the crystal holder
A tilt of the rotation axis of the yaw and pitch stages
Offsets between readouts and actual machine angles
Roll = 4.25°, Yaw = 0.014°;
Pitch_y = 1.05°, Pitch_z = -0.95°,
Yaw_x = -2.5°, Yaw_z = °;
offset_pitch= 0.12°, offset_yaw= 0.59°.

5. HXRSS Crystal GUI HXRSS Crystal gui allows to:
- select the desired reflections
Calculate pitch and yaw angles to have the desired reflections (one or two) at the desired photon energies
Sets angles in the machine
- Change the crystal calibration parameters
Calibration was measured once
in January 2013 and never changed. Gives any seeded photon energy within 2 eV.
Courtesy of Alberto Lutman

6. HXRSS set-up procedures
Standard SASE tuning with taper without crystal
Tune on electron beam phase space by looking at XTCAV with wakefield backtracking to U16
Flat phase space distribution at U16 after undulator tuning

7. HXRSS set-up procedures
Turn on chicane, steer to reference orbit, check undulator pointing for bent crystal spectrometer.
Insert crystal, set crystal angle and find seeding on spectrometer
Kick at U16 and use energy vernier to adjust e- energy to get SASE at the desired photon energy
Take crystal out and maximize intensity before U16
Insert crystal again tune the signal after U16
Optimize delay (scan with 5 fs/step)
Tune on taper + standard tuning (OCELOT/Quad…)
minimum 20 min. setup time
Spectrum vs energy bpm
Spectrum vs energy bpm
Energy BPM
Energy BPM
SASE
Crystal in
(seeding on 1 color)

8. Chicane Residual Field
In phase-shift mode the effect from residual field is corrected by orbit steering (using x and y correctors upstream )

9. Undulator Tapering Quadratic taper is normally used in operation
On-line taper optimization program for self-seeding with measured energy distribution under development by Juhao Wu and Kun Fang.
Figure shows a regular quadratic taper for seeding starts around und #26

10. Different Schemes for Operation
Single bunch self-seeding
Single bunch two-color self-seeding (separation within amplification bandwidth)
Twin bunch two-color self-seeding (increases achievable separation)
Two bunch two-color SASE/self-seeding
Single bunch fresh slice two/three-color (self-seeding) FEL with dechirper

11. Single-Crystal Two-Color HXRSS Manipulating the yaw angle
pitch
First undulator section
Second undulator section e -
Diamond
crystal ψ θ
Courtesy of Alberto Lutman
pitch angle θ range [45°,90°] *
yaw angle ψ range [-2.5°,2.5°]
Beam propagation
The yaw angle controls the energy separation for the double lines -> important! Larger yaw angle can increase the separation of the two lines!
(004)
(-1,1,3)
(1,-1,3)
*Lutman, A. A., et al. "Demonstration of single-crystal self-seeded two-color X-ray free-electron lasers." Physical review letters (2014):

12. Twin-bunch HXRSS increases achievable separation
L1S
L1X
DL1
BLM1
BLM2 L0
Gun
Undulator
E-BPMs
2-color spectrum
Pulse Stacker
Few ps
delay
Tens of fs delay after compression
Cathode laser
*A. Marinelli, et al. ”Twin-bunch two-color FEL at LCLS." Proceedings of IPAC 2016, TUZA02.

13. (unpublished material)
Single bunch fresh slice two/three-color (self-seeding) FEL with dechirper
Courtesy of Alberto Lutman
(unpublished material)
Vertical
wakefield kicker
Horizontal
wakefield kicker
Head-tail kick on x
Head-tail kick on y
FEL Statistics: 746 +/- 125 mJ (250 on tail)
1.03 mJ
@710eV
Tail
Head
Tail Lasing
Pulse on tail ~ 4 fs ; Pulse on head ~ 17 fs
Head Lasing
Demonstrated:
Pulse duration control Nov (A. Lutman unpublished)
Fresh-slice two-color Jan 2016 (A. Lutman unpublished)
Fresh-slice self-seeding March 2016
Fresh-slice three colors (6 and 12 May 2016) (A. Lutman unpublished)
*C. Emma, et al. “High efficiency, high brightness X-ray free electron lasers
via fresch bunch self-seeding." Proceedings of IPAC 2016, MOPOW040.

14. HXRSS Scraping Test at LCLS
Courtesy of
Heinz-Dieter Nuhn
Observation: HXRSS chicane delays greater than 30 fs (3.14 mm offset) trips down stream Beam Loss Monitors (BLMs).

15. HXRSS Scraping Test at LCLS
40 fs
10 fs
Girder rotation used to “re-center” beams in the bellow thus extending the accessible delay range
Problem mitigated at LCLS by bellows replacement: from 9 mm diameter to 11 mm diameter
Center of chicane (dipole magnets, BPM and Monochromator)
Center of undulator system
(beam w/o seeding)
Max. offset of 15 mm
Our case at E-XFEL: no bellows -> minimum distance to vacuum chamber is 4.5 mm (with 15 mm offset)
Minimum distance to the diamond crystal needs to be studied by simulation (important for delay scan)

16. LCLS undulator dose Beam halo losses are main source of radiation
Integrated dose by thermoluminescent dosimiters
Slope of averages: -4.7×10-5 / Gy
Averaged over 1 Gy Intervals
Due to mono-chamber misalignment and small bellow aperture
Note: LCLS-II collimation is being designed to be orders of magnitude better than LCLS-I
* Nuhn, Heinz-Dieter, et al. Undulator Radiation Damage Experience at LCLS. No. SLAC-PUB
System
beam rate
pulse charge
beam power
E-time
<DK/KE>
±(DK/K)tol
E-time × (DK/K)tol / <DK/K E>
Times better than LCLS-I []
[Hz]
[pC]
[kW]
[GJ/d]
[d/GJ]
[10-4/GJ]
[10-4]
[days within tolerance]
LCLS
120
150
0.180
0.015
64.3
-0.16
1.5
586
1.0
SXR
300
0.144
0.012 80
3.0
1466
1,000
100
0.40
0.035 29
-0.091
1000
1.9
4,000
1.60
0.14
7.2
-0.023
7.6
1,000,000 30 10
0.10
569
HXR
322
-1.41
956
0.400
116
3.8
-0.435 15
0.39
1137
Beam halo losses are main source of radiation
LCLS-I collimation system is too short ( 3 radiation length) and their locations are not optimized-> remove and create halo at the same time
Significant particle losses from out-of-time electrons are (dark current) generated in the gun

17. Other discussions: radiation safety and aperture limit
Fluka simulation performed including whole undulator sections for miss-steered beam at LCLS.
Magnet damage experiment performed at LCLS -> scaling factor of 70 kGy/% obtained -> 700 Gy is the upper limit of radiation dose (with 0.01% tolerance for undulator) -> taken for collimation system design of LCLS-II.
Minimum gap of dechirper at LCLS-I: 1 mm -> plan for LCLS-II: dechirper with minimum gap of 2 mm?
Beam halo study is important to define the minimum aperture -> beam halo measurements may be performed at LCLS.

18. Summary and future plan
GUI and tools for HXRSS operation at E-XFEL may be developed in advance (based on the experience from LCLS);
Different operation schemes of HXRSS demonstrated at LCLS -> can be applied in the future at E-XFEL;
Undulator radiation damage measured at LCLS-I and estimated for LCLS-II can be taken as a reference for GEANT4 simulation.

19. Thank You!