flash: the first soft x-ray fel operating two undulator ... filesiegfried schreiber | pitz...

FLASH. Free-Electron Laser

in Hamburg News from FLASH

FLASH: the first soft X-ray FEL operating two undulator beamlines simultaneously

Siegfried Schreiber, DESY

PITZ Collaboration Meeting Zeuthen, Nov 24-25, 2015

FLASH1 FLASH2: 1 pulse

0 50 100 150 200 250

Maximum

Actual

Average

FLASH1: 250 pulses

Bunch number

Ener

gy (μ

J)

Siegfried Schreiber | PITZ Collaboration Meeting | Nov-24, 2015


in Hamburg FLASH 2015: Year of Celebrations

> 15 years of FEL lasing at DESY First lasing (109 nm) of Tesla Test Facility on Feb-22, 2000

> 10 years of SASE at FLASH First lasing (32 nm) of FLASH on Jan-14, 2005

> 10 years of FEL user operation at FLASH User operation started in summer 2005 as the first

FEL user facility in VUV wavelengths worldwide

> 5 years of SASE in the water window at FLASH Lasing at 4.12 nm on Sep-25, 2010

> 1 year of simultaneous operation First lasing of FLASH2 (~ 40 nm) on Aug-20, 2014,

FLASH1 lasing simultaneously with 250 pulses

Lasing with three beamlines simultaneously, with the same bunch in sFLASH and FLASH1 in August 2015



in Hamburg FLASH Layout

> TESLA type superconducting accelerating modules 1.3 GHz > FLASH1 fixed gap undulators > 3rd harmonic sc module 3.9 GHz

> Normal conducting 1.3 GHz RF gun > Ce2Te cathode > Two Nd:YLF based ps photocathode lasers

> FLASH1 Experimental Hall

> Extraction to FLASH2 > FLASH2 variable gap undulators

315 m

5 MeV 150 MeV 1250 MeV

Bunch Compressors

450 MeV

Accelerating Structures RF Stations

Lasers RF Gun

Soft X-ray Undulators sFLASH

FEL Experiments

Photon Diagnostics

Beam Dump

THz FLASH1

> FLASH2 Experimental Hall

Albert Einstein

Kai Siegbahn



in Hamburg FLASH1 Parameters 2014 / 2015

> more than 220 publications on photon science at FLASH, many in high impact journals

FEL Radiation Parameters

Wavelength range (fundamental) 4.2 – 52 nm Average single pulse energy 10 – 500 µJ Pulse duration (FWHM) < 50 – 200 fs Peak power (from av.) 1 – 3 GW Pulses per second 10 – 5000 Spectral width (FWHM) 0.3 - 2 % Photons per pulse 1011 – 1013 Average Brilliance 1017 – 1021 B* Peak Brilliance 1029 – 1031 B*

* photons/s/mrad2/mm2/0.1%bw

Ene

rgy

(µJ)

Bunch number



in Hamburg

38 nm 80 nJ

Cascaded SASE in sFLASH and FLASH1 + FLASH2

> A big step towards seeding in sFLASH truly parallel to FLASH1 operation

20 nm

13.7 nm 75 µJ

> SASE lasing achieved at the same time in all three beamlines

> Cascaded lasing in sFLASH and FLASH1



in Hamburg FLASH operation June – September 2015

Scheduled weekly maintenance 1.3% 36 h

User runs 55.0% 1572 h

Studies 43.7% 1248 h

SASE delivery 72.4% 1138 h

Tuning + Set-up 19.8% 311 h

Down 4.1% 65 h

26.05.2015 - 21.09.2015 (119 days = 2856 hours)

Repair personnel interlock system (broken due to a lighting strike) 3.7% 58 h



in Hamburg Downtime June – September 2015

0

5

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40

22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

Downtime

Dow

ntim

e (%

)

Personnel interlock system broken due to a thunderstorm (lightning strike)

Week

User Block 1 User Block 2 User Block 3

> 26.05.2015 - 21.09.2015: 2820 operation hours

Total down: 233 h (8.3%), of which 97 h due to lightning strike (broken personnel interlock system); Downtime w/o lightning strike: 136 h (4.8%)



in Hamburg Downtime

0

5

10

15

20

CW 22 CW 24 CW 27 CW 28 CW 29 CW 30 CW 36

13121110987654321

1 LLRF (mainly RF-gun, in CW 22 also cooling problems of rack ACC139 ) 2 Technical problem of vacuum valve 4EXP 3 RF-4 and RF-5 off due RF leakage interlock (caused by window teststand RF-station) 4 MPS modul (BIS gateway) blocks beam (Output Module of BIS plc mechanically damaged) 5 RF-2 Flow HVP (fuse for FUG PS broken) 6 Waveguide system of RF-gun 7 Photon diagnostics (movement of YAG screen) 8 RF-5 (SPS) 9 Water cooling RF-2 and RF-3 (wrong action during cooling-tower maintenance) 10 Master oscillator 108 MHz; reason found to be a broken cable 11 Cryo compressor failure 12 RF-39 Modulator interlock switch error (difficult to find the problem) 13 Miscellaneous

Dow

ntim

e (h

ours

)

LLRF LLRF LLRF MO Cryo Ph. Diag. MPS

RF39

Waveg. Gun

RF-5



in Hamburg

FLASH 2 FLASH1

Many slides on FLASH2 from B. Faatz



in Hamburg FLASH2 Undulator Beamline

> 12 variable gap undulators period 31.4 mm

K-value 0.5 – 2 (rms)

segment length 2.5 m



in Hamburg

Spectrum Profile

Beam position Intensity

Beam Position

FLASH2 Photon Diagnostics Beamline

> Final version of photon diagnostics beamline in FLASH2 tunnel installed 3 months interruption of FLASH2 operation in January – April 2015 Basic photon beam diagnostics (GMD, spectrometer) are now working Beamline construction in the hall started



in Hamburg FLASH2 Experimental Hall – Kai Siegbahn Hall

> Installation of photon diagnostics and first two beamlines in 2015/16

first installations



in Hamburg FLASH2 with SASE record

> 600 µJ reached @15 nm – a new record for FLASH

> Studies on tapering the undulators

> We observed a kink in the undulator beamline → survey next week



in Hamburg Realization of Simultaneous Operation

> Fast kicker and Lambertson septum to extract a part of bunch train to FLASH2

> Two injector lasers: FLASH1 and FLASH2 bunch pattern and bunch charge selected independently

> Flexible RF-system: amplitude and phase adjusted - in certain limits - independently for FLASH1 and FLASH2

FLASH1

FLASH2

RF-pulse amplitude

300 μs 450 μs

FLASH1

RF-pulse flat-top 800 μs

30 μs (kicker) 99 ms (10 Hz rep.rate) FLASH1

FLASH2



in Hamburg Control system (status November 2014).

Main tuning panel



in Hamburg Control system (status May 2015).

New: Slow RF Feedback Charge Feedback

Main tuning panel



in Hamburg Control system (status November 2015).

New: Online Energy Monitor LLRF learning FF

Main tuning panel



in Hamburg Undulator Control (status November 2014).

Set undulator gaps based on beam energy and desired wavelength. All undulators characterized individually.



in Hamburg Undulator Control (status May 2015).

Set undulator gaps and automatically adjust phase shifters to match, including orbit correction.



in Hamburg Undulator Control (status November 2015).

Added tapering (in different groups) and global phase change.



in Hamburg Tunability.

FLASH1: 13.57 nm for users




FLASH1: 13.57 nm for users FLASH2: large variation in intensity from 350 to 1 µJ




0

50

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300

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400

10 20 30 400

100

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400

Puls

Ener

gy (m

J)

Wavelength (nm)

FLASH1: 13.57 nm for users FLASH2: Wavelength scan from 40 to 10 nm



in Hamburg

RF Gun



in Hamburg

RF gun controlled by a MTCA.4 based LLRF system since Jan 2015

RF Guns operated at FLASH since 2004

2004

2009

1/2010

6/2010 9/2011

6/2012

Gun2: 5 Hz, 3.5 MW, 350 µs, 5 kW, 680 GJ Window: G29

Gun4.2: 10 Hz, 3.9 MW, 400 µs, 15 kW, 1200 GJ

Window break down; → G67 Window break down; → G29

Window: Gxx

Gun4.1: 10 Hz, 4 MW, 550 µs, 21 kW, 930 GJ

3/2013 Window: G29 Gun3.1: 10 Hz, 5 MW, 550 µs, 27 kW, 1700 GJ(*)

Gun2 breakdown

Gun4.2 breakdown 5/2012

Window: Thales 5 4/2014 Window leak; → G64

Integrated RF-power

Gun 2

Gun 4.2

Gun 4.1

Gun 3.1

No breakdown events or other trips since 8-Jun-2014

(*) until 24-Nov-2015



in Hamburg RF Gun Low Level RF

> LLRF now based on MTCA.4 standard

> System identification performed Model found and controller designed

large loop latency compared to system bandwidth ~1.4 µs

> Runs smooth and stable

> Includes learning feedforward

Feedback gain currently not sufficient to achieve a phase stability of dφ < 0.01 dg

> Features additional protection mechanisms amplitude limiter, fast switch off

Regulation performance (rms)

Intra pulse (flattop )

Pulse to pulse (960 consecutive pulses)

Amplitude dA/A (%) 0.008 0.008

Phase dφ (dg) 0.007 0.076

Goal: < 0.01% in amplitude and < 0.01 dg (rms) in phase

OK



in Hamburg Cascaded Control Scheme for the RF Gun

1. Water temperature regulation

> Speed ~ Hz

PI feedback controller with PLC

Sensor: temperature at the iris

Actuator: cold water valves (combination of fast and slow)

2. Temperature regulation with RF

> Speed: MHz to Hz

MIMO feedback controller

Sensor: virtual probe (Vfwrd, Vrfl)

Actuator: RF power via Input to RF via vector modulator (pulse length)

S. Pfeiffer et al. Goal: Fast compensation of temperature drifts Fast Actuator Fast and precise temperature information



in Hamburg Long term data with cascaded feedbacks

> Phase sampled at 3

positions during flattop (700

μs, 900 μs, 1100 μs)

> Without and with RF based

feedback (pulse length)

flatto

p sa

mpl

ing

posi

tion

Large improvement w/o: dφ > 0.050 dg with: dφ <0.016 dg

15.9 mdg rms

10.9 mdg rms

9.6 mdg rms

52.8 mdg rms

31 mdg rms

21.3 mdg rms



in Hamburg

Cathode



in Hamburg Cs2Te Cathodes

> High initial quantum efficiency ~10 … 15 %

> Excellent lifetime > 1 year at FLASH

> Preparation systems at LASA, Milano and DESY, Hamburg

UHV transport boxes

> Requires UV laser 275 … 250 nm

Laser

e- -beam

Mo plug

Thin film of Cs2Te on Mo plug

16 mm

5 mm



in Hamburg QE map Cathode 73.3 at FLASH

> Cathode 73.3 inserted 4-Feb-2015, initial QE 12.4% 26-Jun-2013, LASA

> Similar QE pattern as previous cathode 618.3

4-Feb-2015 fresh QE=10.3 %

73.3 73.3 73.3

73.3 73.3

3-Mar-2015 QE=10.3 %

18-Aug-2015 QE=11 %

28-Sep-2015 QE=8.9 %

19-Nov-2015 QE=7.2 %

> Quick QE degradation in the center

> Rest follows slowly

> This time at a high 7% level

No vacuum issue as for 618.3



in Hamburg QE cathode 73.3 at FLASH

cw 26-Jun-2013

26-Jun-13



in Hamburg

Outlook



in Hamburg FLASH 2016

> Both FLASH1 and FLASH2 in regular user operation

> 2 user periods: January – June and July – December, 2016 As before: User blocks alternating with study blocks

> No major changes on the FLASH facility expected Resource demanding installations and technical works avoided

until installations of the European XFEL finished

> FLASHForward installations in FLASH2 tunnel (now, mid 2016, and end 2016) – electron driven plasma acceleration A. Aschikhin et al. NIMA 806 (2016) 175

flash: the first soft x-ray fel operating two undulator ... filesiegfried schreiber | pitz...

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