high rep rate guns: fzd superconducting rf … of radiation physics jochen teichert...
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Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBE
J. Teichert, A. Arnold, H. Büttig, D. Janssen, M. Justus, U. Lehnert, P. Michel,K. Moeller, P. Murcek, Ch. Schneider, R. Schurig, G. Staats, F. Staufenbiel,
H. Tietze, R. Xiang, P. Kneisel, B. v. d. Horst, A. Matheisen, J. StephanT. Kamps, J. Rudolph, M. Schenk, G. Klemz, I. Will, V. Volkov
High Rep Rate Guns:FZD Superconducting RF Photogun
FLS 2010 Workshop, SLAC, March, 1-5, 2010
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBEINTRODUCTION – HISTORY OF SRF GUN R&D
68 7
1 2 3 4
5
1988-91 proposal & first experimentA. Michalke, PhD Thesis, WUB-DIS 92-5Univ. Wuppertal, 1992
2002 first beam from a SCRF gun @ FZDD. Janssen et al., NIM-A, Vol. 507(2003)314
since 2004: Development of the 3½-Cell SRF Photoinjector for ELBE A. Arnold et al., NIM-A, Vol. 577(2006)440
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBECOMMISSIONING – FIRST COOL-DOWN
0 50 100 150 200 250 3001,2980G
1,2985G
1,2990G
1,2995G
1,3000G
1,3005G
frequ
ency
[Hz]
temperature [K]
∆f=2.02MHz
first cool-down 1 – 2 August 2007
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBECOMMISSIONING - FIRST ELECTRON BEAM
Cu cathode
RF: Eacc = 5 MV/mf = 1300. 38327 MHz, 150 Hz bandwidthPdiss = 6 W
Laser: 263 nm, 100 kHz reprate0.4 W power (4 µJ)
Cathode: Cu, Q.E. ≈ 10-6
Electron beam: 2.0 MV energy 50 nA average current,0.5 pC bunch charge
first beam of the 3½ cell SRF gun on November 12th, 2007
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBEINTRODUCTION
ELBE Superconducting RF Photoinjector• New Injector for the ELBE SC Linac• Test Bench for SRF Gun R&D
Mode ELBE High Charge
final electron energy ≤ 9.5 MeV
RF frequency 1.3 GHz
operation mode CW
bunch charge 77 pC 1 nC
repetition rate 13 MHz 500 kHz
laser pulse (FWHM) 4 ps 15 ps
transverse rms emittance 1 mm mrad 2.5 mm
mrad
average current 1 mA 0.5 mA
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBE
Design for the SRF-Gun @ ELBE• CW + high rep rate - 500 kHz, 13 MHz and higher• medium average current 1 – 2 mA (< 10 mA)• high energy (stand alone) - 3½ cells• low - high bunch charge 80pC – 1 nC• low transverse emittance 1 – 3 mm mrad• normal-conducting, lqN2-cooled, exchangeable,
semi-conductor photo cathode• highly compatible with ELBE cryomodule(1.3 GHz cavity, 10 kW coupler, He & N2 support, etc.)
Application @ ELBE• high peak-current operation for FELs with (13 MHz, 80 pC)• high current (1 mA) @ low rep rate (<1 MHz) -> high charge
pulsed secondary particle beams: neutrons, positronswith ToF measurements
• low emittance @ medium charge (100 pC) for short pulsesTHz-radiationx-rays by inverse Compton backscattering
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBE
LASER
NC Cs2Tephoto cathode
heliumport
SC Nb3½ -cell cavity
e-
MAIN COMPONENTS
Liquid HeVessel
cathode cooling (77 K)& support system
photo cathodealignmentcavity
tuners
rf powercoupler
SRF Gun Cryomodule
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBE
parameter present cavity new “high gradient cavity”measured ´08 ELBE high charge ELBE high charge
final electron energy 2.1 MeV 3 MeV ≤9.5 MeV
peak field 13.5 MV/m 18 MV/m 50 MV/m
laser rep. rate 1 – 125 kHz 13 MHz 2 – 250 kHz 13 MHz ≤500 kHz
laser pulse length (FWHM)
15 ps 4 ps 15 ps 4 ps 15 ps
laser spot size 2.7 mm 5.2 mm 5.2 mm 2 mm 5 mm
bunch charge ≤ 200 pC 77 pC 400 pC 77 pC 1 nC
max. aver. Current 1 µA 1 mA 100 µA 1 mA 0.5 mA
peak current 13 A 20 A 26 A 20 A 67 A
transverse. norm. emittance (rms)
3 1 mm mrad@ 80 pC
2 mm mrad 7.5 mm mrad 1 mm mrad 2.5 mm mrad
SRF Gun Parameter
MEASUREMENT & OPERATION PARAMETERS
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBE
0.0 10.0M 20.0M 30.0M 40.0M 50.0M
1E9
1E10
Q 0
Epeak in V/m
V-Test 1 V-Test 2 V-Test 3 V-Test 4all 4 tests limited by field emission
achieved peak axis fields of all 4 vertical test benches Tests in thevertical cryostat(1.8 K) at DESYin 2007
3½ CELL CAVITY
HPR cleaning very difficult, surface damagedafter 4 vertical test at DESY improvement not expected
cavity used as it was, assembly continued
Treatment and test of the cavity
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBE
Helium consumption measurement
3½ CELL CAVITY
Cavity performance in the gun
2.7peak
acc
EE
=
• maximum achievable field only 1/3 of the designed value of Epeak=50 MV/m,• measured Q0 is 10 times lower than in all vertical tests,• gradient is limited by field emission• no Q degradation found since the 1st measurement in 2007,• Improvement by (9th test) high power processing (HPP) results 3 MeV operation• After warming-up or cathode exchange the HPP must be repeated
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBE3½ CELL CAVITY
Energy and energy spread @ 5 pC (w/o space charge)
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBE
09:36 10:48 12:00 13:12 14:24 15:36
30,6
30,9
31,2
31,5
pres
sure
[mBa
r]
time [hh:mm]
SRF Gun: ~ 230 Hz / 1mbarELBE Linac: ~ 35Hz / 1mbar
1,30038102G
1,30038108G
1,30038114G
1,30038120G
1,30038126G
1,30038132G
f 0 [H
z]
RF MEASUREMENTS
He pressure effect on cavity frequency
30,6 30,7 30,8 30,9 31,0 31,1 31,2 31,31300381000
1300381020
1300381040
1300381060
1300381080
1300381100
1300381120
1300381140
1300381160
1300381180
1300381200
∆=232,61337 Hz/mBar
f0 [Hz]
P [mBar]
Messwerte f0 vs. P lineare Regression
Lorentz force detuning
SRF-gun ~230 Hz/mbar ELBE module ~35 Hz/mbar
3½ CELL CAVITY
SRF-gun K= 0.69 Hz/(MV/m)²ELBE module K = 0.25 Hz/(MV/m)²(with respect to peak fields)
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBE3½ CELL CAVITY
New “High Gradient” Cavity
old design new design
Improvements• higher stiffness of the half-cell back wall
microphonics, Lorentz force detuning• larger opening in choke and partly in half-cell
better HPR cleaning• new pick-up antenna design, etc.
simpler clean-room assembly
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBE
New “High Gradient” Cavity
3½ CELL CAVITY
Fabricated in collaborationwith JLab, thanks to P. Kneisel
standardRRR 300Nb cavity
Large grainNb cavity
now: warm tuning @ JLabnext: warm rf measurements @ FZD
cleaning & test @ JLab
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBE
Photo cathode preparation equipment at FZD
Ø10 mm Cs2Tecone forpositioning &thermal contact
pressure springbayonet fixing
Photo Cathode Transfer System
Cs2Te PHOTO CATHODES
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBE
Transferchamber
Transportchamber
Lock
Cathode transfer rodlinear & rotation
Places for6 cathodes
Use of semiconductor photo cathodes likeCs2Te requires a UHV exchange systemwith <109 mbar
• Cool PC exchange works • Change of PC needs ~30 min• Docking of transport chamberneeds 1 maintenance shift+ 1 week backing (duringELBE operation)
Photo Cathode Transfer System
Cs2Te PHOTO CATHODES
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBEUV LASER SYSTEM
UV CW Laser system delivered by MBILaser upgrade 2010
(0.5 W @ 262 nm)
Two oscillators13 MHz:
Nd:glass oscillator (26 mHz)3 ps FWHM Gaussian
500, 250, 125 kHz:Nd:YLF oscillator (26 mHz)
14 ps FWHM Gaussian
one amplifierNd:YLF multipass amplifier
10-20 W
two UV converterstwo-stage frequency
converters (LBO, BBO)existing ≤250 kHz laserwith Nd:YLF regenerativeamplifier
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBEUV LASER SYSTEM
Upgrade of the laser beam line & virtual cathode
remote-controlled laser spot size setting(telescope & aperture)
Measurement of laser profile, position, andpower on the virtual cathode screen
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBE
diagnostics beamline designed and built by HZB (BESSY) Berlin
- Laser input port, Solenoid- Current & Charge (Faraday-cup & ICTs) - Transverse Emittance (slit mask, solenoid scan)- Energy and ∆E (C-bent)- Bunch length (Cherenkov radiator with optical
beamline and streak camera,electro-optical sampling
BEAM PARAMETER MEASUREMENT - DIAGNOSTICS BEAMLINE
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBEELBE INJECTION
Installation of electron beamline to ELBE was finished in winter shutdown 2009/10
First accelerated SRF gun beam at ELBE on Febr. 5, 2010
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBEELBE INJECTION
5 MeV energy increaseCompared to thermionicinjector3 MeV from SRF gun,2 MeV from on-crestinjection
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBESUMMARY
In 2009• Upgrade of the cathode transfer system: sufficient vacuum, backing duringELBE operation
• Installation of the beam line to ELBE• Commissioning of the Cherenkov station for bunch length measurements• Spectrometer for slice emittance measurements delivered• Design upgrade and fabrication of two new “high gradient” cavities
Outstanding and planned for 2010• Demonstration of ELBE injection• Preparation and Test of the new cavities at JLab• Demonstration of high-current operation with 13 MHz laser & PC >1% QE• Systematic experimental studies of HOM excitation in the gun• Measurements & Optimization to find the bunch charge limit at 3 MeV• First ELBE user beam with SRF gun
Institute of Radiation Physics Jochen Teichert www.fzd.de Forschungszentrum Dresden-Rossendorf
Radiation Source ELBE
AcknowledgementWe acknowledge the support of the European Community-Research Infrastructure Activity
under the FP6 programme 2004-08 (CARE, contract number RII3-CT-2003-506395) and the FP7 programme since 2009 (EuCARD, contract number 227579) as well as the support of the
German Federal Ministry of Education and Research grant 05 ES4BR1/8.
THANK YOU FOR YOUR ATTENTION
Thanks to the ELBE crew, the technical staff of BESSY, DESY and MBI,
to RI, JLab, and all the others supported and encouraged this project