Post on 28-Mar-2015
Injection system of the 4GLS light source
B.L. Militsynon behalf of 4GLS team
ASTeC
STFC Daresbury Laboratory
ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
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Outline
Introduction4GLS light sourceInjection 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 perspectivesConclusion
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
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4GLS Layout
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
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XUV-FEL branch of 4GLS
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
Photon energy range, eV 8-4035-100
Peak power, GW 3-51-3
Photon pulse length, fs 22Repetition rate, kHz 1
Beam energy 750 MeV
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XUV-FEL injector
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
Beam parameters at the entrance of main linac
Bunch charge, nC 1.0Bunch repetition rate, kHz 1.0Beam energy, MeV 210Normalised emittance, π·mm·mrad <2Uncorrelated energy spread, % <0.05RMS bunch length (σ ), ps ~2
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Normal conductive 1.5-cell RF photocathode gun
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
0
400
800
1200
1600
2000
2400
0 0.2 0.4 0.6 0.8 1
Longitudinal position, m.
Ma
gn
eti
c f
ield
, a
.u.
-60.0
-40.0
-20.0
0.0
20.0
40.0
60.0
Ele
ctr
ic f
ield
, a
.u.
Focusing magnetic field
Accelerating electric field
Distribution of accelerating RF and focusing magnetic field in the gun
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ASTRA simulation of the RF gun
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
0 0.5 1 1.5 2 2.5 330
1
2
3
4
5
Horizontal position, m
RM
S t
rans
vers
e be
am s
ize,
mm
Simulation parameters
Laser spot diameter, mm 4Spatial laser spot distribution UniformTemporal laser pulse shape Flat-topLaser pulse length, ps 20Rise time, ps 2Initial rms beam energy spread, V 0.4Maximum RF accelerating field, MV/m 40
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ASTRA simulation of the XUV-FEL injector
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
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ASTRA simulation of the XUV-FEL injector
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
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Laser for the XUV-FEL injector
[%]][
1241
eQnm
nCqJE
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
Required energy of laser pulse is given by:
For an CsTe2 photocathode Qe=1% at =262 nm :
Wavelength, nm 262Repetition rate, kHz 1.0Pulse shape Flat topMaximum rise time, ps 2Pulse length, ps 10Laser pulse energy, µJ 1
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VUV-FEL branch of 4GLS
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
Photon energy range, eV 3-10Peak power, MW 350Photon pulse length, fs 64Repetition rate, MHz n*4.33
Beam energy 550 MeV
Maximum photon energy, eV 80Average flux, 1/s/0.1% bp 1.0*1015
Repetition rate, GHz 1.3
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VUV-FEL injector
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
Beam parameters at the entrance of main linac
Bunch charge, pC 77Bunch repetition rate, GHz 1.3Operation mode CWBeam energy, MeV 10Normalised beam emittance, π·mm·mrad < 2Uncorrelated energy spread, % < 0.1Bunch length, ps 5
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High voltage DC photocathode gun
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
Parameter of the photocathode gun
Gun voltage, kV 500Average beam current, mA 100Bunch repetition rate, GHz 1.3RMS laser pulse length, ps 20Laser pulse shape GaussianEstimated operational lifetime, hours 27Estimated rms transverse emittance, π·mm·mrad 2.8Estimated rms bunch Length, ps 30
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Photocathode preparation set-up
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
Required photocathodes:
•NEA III/V semiconductor•Transmission mode•High quantum efficiency•Fast response•High emission current density
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Photoemission from “thick” NEA photocathodes
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
Photoemission from “thick” NEA photocathodes illuminated by
green light
by the courtesy of A.S. Terekhov
Energy distribution of electrons emitted from bulk GaAs photocathodes according to
measurements made at Max Planck Institut für Kernphysik (MPI-K), Heidelberg, Germany.
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Photoemission from “thin” NEA photocathodes
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
100 nm
1000 nm
2.3 ps
30 ps
Data from Mainz: experiment, diffusion model
if d≤L - thermalization length “hot” photo-electrons increase transverse energy spread
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Beam dynamics in the VUV-FEL injector
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
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Laser for VUV-FEL injector
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
For GaAs photocathodes <850 nm, for =520 nm
Wavelength, nm 520Repetition rate, GHz 1.3RMS pulse with, ps 10Average laser power for Qe=10%, W 2.3Average laser power for Qe=1%, W 23Average laser power for Qe=1%,=0.7, W 33Timing jitter, fs 100
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Time structure of the beam in the main linac
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
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4GLS laser system
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
by the courtesy of G. Hirst
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IR-FEL branch of 4GLS
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
Wavelength, m 2.5-2520-200
Repetition rate, MHz 13Peak power, MW 3-20Photon pulse length, ps 0.8-2.4Switch yard frequency, Hz 100
Beam energy 25-60 MeV
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IR-FEL injector
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
Bunch charge, pC 200Bunch repetition rate, MHz 13Peak current, A 8 to 80Energy, MeV 25 to 60Normalised emittance, π·mm·mrad < 10RMS energy spread, % < 0.1RMS bunch length, ps 1 - 10
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Thermionic emitter
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
-2
-1
0
1
2
0 0.5 1 1.5 2
RF phase, p .
Gri
d v
olt
age,
a.u
.
Grid modulated 6 mm LaB6 emitter Formation of the grid voltage
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ASTRA simulation of a 400 kV thermionic gun
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
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Beam in the transverse and longitudinal phase spaces
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
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Status and perspectives
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
XUV-FEL injector R&DVUV-FEL injector
•Photocathode gun Drawing room•Preparation facility Drawing room•Photocathodes R&D•Laser system R&D•High voltage power supply R&D•Test beam line ERLP test beam line
IR-FEL injector R&D
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Conclusion
B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007
Injection system of 4GLS requires state of the art and beyond electron sources, laser and synchronisation devicesThough 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 cavityHigh repetition rate low jitter laser system
Injector for VUV-FEL requires additional research in the direction ofPhotocathode developmentPhotocathode preparation and manipulation techniqueVery high voltage photocathode gun designHigh frequency high power laser system
IR-FEL injector may be build on the bases of well known grid modulated thermionic gun