SRF Photoelectron Source Development for BERLinPro TTC-meeting Februar 28 March 3 2011 Milano, Italy O. Kugeler (based on talk given by A. Neumann) O. Kugeler TTC Meeting February 28 March 3 2011 Milano, Italy Path towards a Photoinjector for BERLinPro ERL: Combine high beam quality of linac with high average current of storage rings Booster Main linac Merger Beam dump Undulator Gun Return arcs RF Photoinjector ERL challenges: - Optics design max. beam energy 100 MeV - HOM excitation, beam break up max. current 100 mA - Bunch length manipulation nominal bunch charge 77 pC - Beam loss max. rep. rate
1.3 GHz - Timing jitter normalized emittance < 1mm mrad - Field control cryo load @ 1.8K 240 W But: The beam quality is determined by the source No source has ever reached these parameters Workshop at HZB with leading experts in 2009: Decision for SC RF Photoinjector Goals for ERL demonstrator O. Kugeler TTC Meeting February 28 March 3 2011 Milano, Italy 2 SC RF photoinjector principle Pick-up probe Excited -TM010 mode Pb-Cathode TTF-III Input coupler Frequency -mode 1300 MHz Epeak/Eacc 1.86 Hpeak/Eacc
4.4 mT/(MV/m) Geometric factor 212.2 R/Q (linac, =1) 189.9 Qext 10 -10 7 - 1.6 cell TESLA structure with backplane at the equator; EM design by Jacek Sekutovicz: Highest fields at Cathode region Reaching ERL parameters is a complex task and challenge 8 O. Kugeler TTC Meeting February 28 March 3 2011 Milano, Italy follow a three stage approach 3 The three stage approach HoBiCaT Stage A Beam
Demonstrator Parameter Goal Electron energy RF frequency Design peak field Operation launch field Bunch charge Repetition rate Cathode material Laser wavelength Laser pulse energy Laser pulse shape Laser pulse length Average current 30 kHz Pb 258 nm 0.15 J Gaussian 2.5 ps FWHM 0.5 A Gun lab Stage B Brightness R&D gun 1.5 MeV 1.3 GHz 50 MV/m 10 MV/m 77 pC 54 MHz
Cu, CsK2Sb 355, 526 nm 1 J Gaussian, Flat-top 15 ps 10 mA BERLinPro Stage C Current Production gun 1.3 GHz CsK2Sb 526 nm 4 nJ Flat-top 15 ps 100 mA Stage A (Beam dynamics): Stage B (Peak Brightness): Stage C (High avg. Current): Study beam dynamics of SC RF photoinjector: - Emittance - Field levels - Stability Starting point for SC design and operation of SRF gun no tuner. Sync with feeback loop on laser rep-rate
Study + develop cathode insert into SC injector (choke filter): Lifetime + quantum efficiency of cathode materials Reliable cathode replacement scheme SC design for ERL design current High power operation HOM damping Cathode lifetime Started here O. Kugeler TTC Meeting February 28 March 3 2011 Milano, Italy 4 Stage A Gun with Diagnostic beamline at HZB Stripline BPM, ICT SC Solenoid (Niowave) THz diagnostics SQ Faraday Cups SC Cavity
HoBiCaT cryostat Dipole magnet Mass Spectrometer Viewscreens First time operated fully SC photoinjector ensemble (SC Cathode, Cavity & Solenoid) O. Kugeler TTC Meeting February 28 March 3 2011 Milano, Italy 5 Extension of the HoBiCaT Cavity Test Facility Laser hut Laser beamline HoBiCaT cryostat Diagnostic e- beamline C o n t r o l ro o m
IOT (CPI, cw, 17kW) O. Kugeler TTC Meeting February 28 March 3 2011 Milano, Italy 6 The Collaboration for the Stage A injector Cathode Laser cleaning QE measurements Cavity fabrication, treatment and testing Cavity electro-magnetic design Project planning Cavity mechanical design, Setup of test facility, Beam physics program O. Kugeler TTC Meeting February 28 March 3 2011 Milano, Italy Pb Cathode deposition Laser design and fabrication 7 Mechanical design: Countermeasures to increase field stability Beam quality dominated by field stability Field stability in SC cavity: Avoid detuning (deformation) of the cavity
Combined FEM mechanical and Electro-magnetic field simulations low deformation (detuning) design ANSYS simulation Backwall stiffening Detuning in Hz/mbar F Type Without Short bar Long bar Spider O. Kugeler TTC Meeting February 28 March 3 2011 Milano, Italy SuperFish 527 200 130 - CST MWS 615 - Measured 474 146 8 Cavity fabrication at Thomas Jefferson Lab Fundamental power coupler port
Stiffening ring STATUS ANFANG DES JAHRES: Cavity backwall for cathode Cavity halfcells Passive stiffening System: Spider Pick-up Port Helium vessel endplate All pictures courtesy of Peter Kneisel Cavity in helium vessel Cavity tuning setup at JLab O. Kugeler TTC Meeting February 28 March 3 2011 Milano, Italy 9 Cathode deposition at IPJ Andre Soltan Swierk Plasma arc depositon setup in 30 configuration 16 x 5min depositions result in a few hundred nm thick Pb cathode film Cavity with helium vessel
Pb cathode film Mask to protect cavity O. Kugeler TTC Meeting February 28 March 3 2011 Milano, Italy 10 Cavity vertical tests at Jlab: Current status ERL operation Acceptance tests for SC cavity: Rsurf or Q0 as function of peak field Test after fabrication, tuning and several treatments: Peak fields > 40 MV/m, light field emission at highest fields Cathode deposition First cathode was lost Second cathode depositon Final vertical test with cathode: Fields above ERL operating range Surface resistance below cryogenics limits Cavity ready for beam production! O. Kugeler TTC Meeting February 28 March 3 2011 Milano, Italy 11 Outlook: Near future onebeamline in HoBiCaT d Installation of cavity, solenoid
and t s o alm Cold test of solenoid Installation and commissioning t doneof laser s o m l a First horizontal RF tests: - Q0(Eacc), cryogenic tests - LLRF field control: Field stability - Test with laser and RF, synchronization First beam on viewscreen by spring 2011 Start design of Stage B in collaboration with FZD (HZDR), DESY and TU Dortmund People involved: W. Anders, M. Dirsat, A. Frahm, A. Jankowiak, T. Kamps, J. Knobloch, O. Kugeler, A. Neumann, T. Quast, J. Rudolph, M. Schenk, M. Schuster, Helmholtz-Zentrum Berlin fr Materialien und Energie GmbH, Berlin, Germany T. Rao, J. Smedley, BNL, Upton, Long Island, New York, USA J. Sekutowicz, DESY, Hamburg, Germany P. Kneisel, JLAB, Newport News, Virginia, USA R. Nietubyc ,The Andrzej Soltan Institute for Nuclear Studies, Swierk/Otwock, Poland I. Will, MBI, Berlin, Germany + the support of many more. O. Kugeler TTC Meeting February 28 March 3 2011 Milano, Italy 12
