Injection system of the 4GLS light source

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Injection system of the 4GLS light source

• B.L. Militsyn
• on behalf of 4GLS team
• ASTeC
• STFC Daresbury Laboratory

ERL07 Workshop, Daresbury, 21.05.2007-25.05.2007
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Outline

• Introduction
• 4GLS light source
• Injection system of 4GLS
• XUV-FEL normal conductive RF photoinjector
• VUV-FEL High Average Current DC NEA photocathodes
  based injector
• 4GLS laser system
• IR-FEL thermionic injector
• Status and perspectives
• Conclusion

B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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4GLS Layout
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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XUV-FEL branch of 4GLS
Beam energy 750 MeV
Photon energy range, eV 8-40 35-100 Peak
power, GW 3-5 1-3 Photon pulse length,
fs 22 Repetition rate, kHz 1
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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XUV-FEL injector
Beam parameters at the entrance of main
linac Bunch charge, nC 1.0 Bunch repetition
rate, kHz 1.0 Beam energy, MeV 210 Normalised
emittance, pmmmrad lt2 Uncorrelated energy
spread, lt0.05 RMS bunch length (s ), ps 2
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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Normal conductive 1.5-cell RF photocathode gun
Distribution of accelerating RF and focusing
magnetic field in the gun
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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ASTRA simulation of the RF gun
Simulation parameters Laser spot diameter,
mm 4 Spatial laser spot distribution Uniform Tem
poral laser pulse shape Flat-top Laser pulse
length, ps 20 Rise time, ps 2 Initial rms beam
energy spread, V 0.4 Maximum RF accelerating
field, MV/m 40
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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ASTRA simulation of the XUV-FEL injector
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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ASTRA simulation of the XUV-FEL injector
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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Laser for the XUV-FEL injector
Required energy of laser pulse is given by
For an CsTe2 photocathode Qe1 at l262 nm
Wavelength, nm 262 Repetition rate,
kHz 1.0 Pulse shape Flat top Maximum rise
time, ps 2 Pulse length, ps 10 Laser pulse
energy, µJ 1
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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VUV-FEL branch of 4GLS
Beam energy 550 MeV
Photon energy range, eV 3-10 Peak power,
MW 350 Photon pulse length, fs 64 Repetition
rate, MHz n4.33
Maximum photon energy, eV 80 Average flux,
1/s/0.1 bp 1.01015 Repetition rate, GHz 1.3
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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VUV-FEL injector
Beam parameters at the entrance of main
linac Bunch charge, pC 77 Bunch repetition
rate, GHz 1.3 Operation mode CW Beam energy,
MeV 10 Normalised beam emittance, pmmmrad
lt 2 Uncorrelated energy spread, lt 0.1 Bunch
length, ps 5
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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High voltage DC photocathode gun
Parameter of the photocathode gun Gun voltage,
kV 500 Average beam current, mA 100 Bunch
repetition rate, GHz 1.3 RMS laser pulse length,
ps 20 Laser pulse shape Gaussian Estimated
operational life time, hours 27 Estimated rms
transverse emittance, pmmmrad 2.8 Estimated
rms bunch Length, ps 30
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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Photocathode preparation set-up

• Required photocathodes
• NEA III/V semiconductor
• Transmission mode
• High quantum efficiency
• Fast response
• High emission current density

B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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Photoemission from thick NEA photocathodes
Photoemission from thick NEA photocathodes
illuminated by green light
Energy distribution of electrons emitted from
bulk GaAs photocathodes according to measurements
made at Max Planck Institut für Kernphysik
(MPI-K), Heidelberg, Germany.
by the courtesy of A.S. Terekhov
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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Photoemission from thin NEA photocathodes
Data from Mainz experiment, diffusion model
if dL? - thermalization length hot
photo-electrons increase transverse energy spread
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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Beam dynamics in the VUV-FEL injector
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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Laser for VUV-FEL injector
For GaAs photocathodes llt850 nm, for l520 nm
Wavelength, nm 520 Repetition rate,
GHz 1.3 RMS pulse with, ps 10 Average laser
power for Qe10, W 2.3 Average laser power for
Qe1, W 23 Average laser power for Qe1,?0.7,
W 33 Timing jitter, fs 100
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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Time structure of the beam in the main linac
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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4GLS laser system
by the courtesy of G. Hirst
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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IR-FEL branch of 4GLS
Beam energy 25-60 MeV
Wavelength, mm 2.5-25 20-200 Repetition rate,
MHz 13 Peak power, MW 3-20 Photon pulse length,
ps 0.8-2.4 Switch yard frequency, Hz 100
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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IR-FEL injector
Bunch charge, pC 200 Bunch repetition rate,
MHz 13 Peak current, A 8 to 80 Energy,
MeV 25 to 60 Normalised emittance, pmmmrad lt
10 RMS energy spread, lt 0.1 RMS bunch length,
ps 1 - 10
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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Thermionic emitter
Grid modulated 6 mm LaB6 emitter
Formation of the grid voltage
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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ASTRA simulation of a 400 kV thermionic gun
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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Beam in the transverse and longitudinal phase
spaces
B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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Status and perspectives

• XUV-FEL injector RD
• VUV-FEL injector
• Photocathode gun Drawing room
• Preparation facility Drawing room
• Photocathodes RD
• Laser system RD
• High voltage power supply RD
• Test beam line ERLP test beam line
• IR-FEL injector RD

B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007
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Conclusion

• Injection system of 4GLS requires state of the
  art and beyond electron sources, laser and
  synchronisation devices
• Though requirements for injector for XUV-FEL very
  close to the parameters of BESSY-PITZ project
  some research are required in thew derection of
• High power gun cavity
• High repetition rate low jitter laser system
• Injector for VUV-FEL requires additional research
  in the direction of
• Photocathode development
• Photocathode preparation and manipulation
  technique
• Very high voltage photocathode gun design
• High frequency high power laser system
• IR-FEL injector may be build on the bases of well
  known grid modulated thermionic gun

B.L. Militsyn, ERL07 Workshop, Daresbury,
21.05.2007-25.05.2007