Status of Cathode System in FZR Photocathode preparation and test of the cathode cooling system Rong Xiang FZ Rossendorf, Dresden

Cathode System in SRF Project Preparation chamber Transport chamber Cathode cooling system 18.01.2019

What we need ? Micro- Pulse Cath Gun Laser necessary project Q.E. 1/18/2019 What we need ? Micro- Pulse Cath Gun Laser necessary project Q.E. Qbunch Imean Pmean Epulse ELBE normal 13 MHz 1% 77pC 1mA  0.47 W 36 nJ 0.8 W 60 nJ high charge 1 MHz 1 nC 1mA 470 nJ 1.0 W 1 µJ future goal 1 kHz 2% 2.5 nC 2.5 µA 0.24 W 590 nJ 18.01.2019 CARE Meeting 2005

Preparation Chamber Design Manufacture First test, optimize Clean room building Clean Assemble Experiment Production (July 2006) 18.01.2019

Preparation System Ultra high vacuum (10-11 ~ 10-9 mbar ) evaporators laser light ports shutter rate monitors cathode Ultra high vacuum (10-11 ~ 10-9 mbar ) Cathode holding Halogen-light heating Ion-beam cleaning Co-evaporation of Te and Cs Measurment of quantum efficiency QE during deposition Life time Distribution scan 18.01.2019

Cathode plug Cathode plugs are made of Cu or Mo Ø10 mm Cs2Te cone for positioning & thermal contact pressure spring bayonet fixing Cathode plugs are made of Cu or Mo Manual Polishing result: average roughness: 17.2 nm (analyzed by Dektak8 profiler) 18.01.2019

Control system Control program “SRFgun” Quartz thickness monitor STM-1 18.01.2019

Co-evaporation Stoichiometric Calibration Preparation NCs R= NTe = 2 1 Te, Cs separate Preparation 18.01.2019

First test in new chamber No. Sub. Thick. Te Thick. Cs Cs/Te PIXE RBS #05-05-31 Cu 10 nm 20 nm 0.55 0.44 #05-06-16 68 nm \ 1.9 #05-06-22 Si 70 nm 1.6 #05-06-23 46 nm 0.8 18.01.2019

Our homepage http://www.fz-rossendorf.de/projects/CARE/ 18.01.2019

2. Transport Chamber Design Manufacture First test, optimize Clean cathode transfer root linear & rotation exchange chamber places for 6 cathodes transportation Design Manufacture First test, optimize Clean Assemble 18.01.2019

Minimum particle generation during exchange Six cathodes can be stored and transferred Accurate adjustment 18.01.2019

3. Cathode cooling system cathode cooler LN2 reservoir Design Manufacture First test, optimize Final assemble 18.01.2019

Test of the cathode cooling system Measured temperatures via power input 30 W power input to the photo cathode burdens the cavity with only 31 mW. (F. Staufenbiel, et al., SRF2005) 18.01.2019

Next work Finish construction of preparation chamber (clean, assemble, vacuum…) Solidify preparation technology (control, measure, calibrate…) Finish the test of transport chamber (optimize, clean, vacuum, portable…) 18.01.2019

Thank you! 18.01.2019