SRF Gun at ELBE Work package 10, Task 7 Jochen Teichert Forschungszentrum Dresden-Rossendorf (FZD) Dresden, Germany EuCARD/SRF Kick-off meeting at DESY, Hamburg, March 24, 2009

7.1 HZB, FZD HZB T. Kamps 7.2 FZD R. Xiang 7.3 FZD, HZB J. Teichert Task - SRF gun @ ELBE 1. Subtasks and Collaboration Partners Leading lab: Forschungszentrum Dresden-Rossendorf (FZD); J. Teichert (j.teichert@fzd.de) Collaborating lab: Helmholz Zentrum Berlin (BESSY); Thorsten Kamps (kamps@bessy.de) Subtask Title collaborators responsible contact person 7.1 slice emittance, installation +measurement HZB, FZD HZB T. Kamps 7.2 preparation + application of GaAs photo cathodes FZD R. Xiang 7.3 evaluation of critical issues of SRF guns FZD, HZB J. Teichert

ELBE layout SRF Gun thermionic DC Gun Task SRF gun @ ELBE - SRF gun status laser ELBE layout thermionic DC Gun SRF Gun 3

SRF Gun operation in 2008 Task SRF gun @ ELBE - SRF gun status gradient Eacc = 5 MV/m, Ee = 2 MeV next run in 2009: Higher gradient 6.5 MV/m Gun operation with Ee = 3 MeV Optimized laser spot size (2.7 mm -> 5.2 mm) Transverse Emittance – Solenoid scan screen DV02 (YAG) 1.9 m from gun exit, 2.7 m from cathode -175°, σx = 300 µm -150°, σx = 330 µm -130°, σx = 610 µm -115°, σx = 760 µm -95°, -65°, σx = 430 µm +3°, σx = 1650 µm laser phase scan

Results of slice measurements Task SRF gun @ ELBE - Subtask 7.1 Slice emittance measurement using a correlated energy spread by ELBE modules beamline to ELBE spectrometer magnet status installation funding Beamline to ELBE design ready 10/2009 FZD lab budget Spectrometer magnet ordered 7/2009 Installation spectrometer dipole Milestone 9/2010 Spectrometer diagnostic 3/2010 HZB / EuCard Results of slice measurements Deliverable 3/2011

alternative for the ILC electron source Subtask 7.2 – GaAs photo cathodes Motivation: high-brightness & high-average-current gun for polarized electrons alternative for the ILC electron source A SRF gun may provide the vacuum required for GaAs photo cathodes by the cryopumping of the cavity. In the RF field the ion backbombardment is reduced compared to exisiting DC guns. A similar experiment will be carried out at BNL Courtesy A. Burrill

Existing equipment for Cs2Te photo cathodes Subtask 7.2 – GaAs photo cathodes Existing equipment for Cs2Te photo cathodes Take a cathode from the carrier Transfersystem at gun while backing Cathode moved with transfer stem Transfersystem in cathode preparation lab

work aim finished vacuum < 10 -9 mbar particlefree Subtask 7.2 – GaAs photo cathodes vacuum < 10 -9 mbar particlefree work aim finished improvement of transfer systems NEG pump, backing p<10-10 mbar 4/2009 Cathode preparation C2Te cathodes with high QE until 9/2009 Modification of preparation system GaAs substrate, etc. 3/2010 Prep. system for GaAs finished Milestone GaAs photo cathodes produced 3/2011 Results of GaAs PC in SRF gun Deliverable 12/2011

perhaps > 2 mA in macropulse mode (dump current limit) Subtask 7.3 – Critical issues of SRF guns High-average current operation SRF guns up to 1 mA in CW operation, perhaps > 2 mA in macropulse mode (dump current limit) cavity performance HOM production and damping photo cathode behavior and life time RF problems, input coupler etc. Photo cathode studies in SRF guns QE and thermal emittance life time, dark current alternative photo cathodes, metallic, CsKNb? Study of emittance compensation methods RF focusing (backdrawn & shaped cathode) External Solenoid RF issues connected to the TE mode no milestones and deliverables

FZD PM 2009 2010 2011 2012 Subtask 7.2 FZD EC Costs and EU support Task 7.3 – SRF Gun @ ELBE Costs and EU support lab total EC funding FZD 281050 € 76 000 € HZB (BESSY) 16 pm 10 pm FZD HZB Additional Personnel FZD PM 2009 2010 2011 2012 Subtask 7.2 FZD EC

Task - SRF gun @ ELBE Deliverables: 10.7.1 Results of slice measurements Report M24 10.7.2 Results for GaAs photo cathodes Report M33 Milestones: 10.7.1 Preparation system for GaAs finished O M12 10.7.1 Installation spectrometer dipole O M18 10.7.3 GaAs photo cathodes produced D 24