Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct First Photocathodes from DESY Sven Lederer PITZ-Collaboration meeting 27 th -28 th of Oct 2011

Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct Preparation system Set-up for QE-measurements and -maps port for transport box/ load-lock port for future SAFEM preparation chamber

Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct >First three real cathodes produced >#22.6 >Plug produced at LASA >Plug polished at LASA >Photo-emissive film deposited at DESY >#613.1 >Plug produced at DESY >Plug polished at DESY (estimated roughness factor 2 higher than #22.6) >Photo-emissive film at DESY >#625.1 >Plug produced at DESY >Plug polished at DESY (estimated roughness factor 2 higher than #22.6) >Photo-emissive film at DESY >In addition new carrier design from LASA: worked really nice! First cathodes

Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct Spectral response > W: work function of material, for Cs 2 Te sum of energy band gap E G and electron affinity E A, > parameter m gives information on emission process cathodeE g +E a mQE (262 nm) # eV % # eV % # %

Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct #625.1 #22.6#613.1

Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct S. Lederer, Beschleunigerbetriebsseminar, Grömitz Cathode operation – #22.6 >Start-up operation with 150  s RF-pulse length and extremely slow ramp-up but continued with 150  s >Full RF-power (6.2 MW) reached >Only two directional coupler vacuum interlocks >Mainly PM interlocks during ramp up of RF-power, but they are not necessarily caused by the cathode No information on signal behaviour and height because of pulse transformers (still)! Without them one could learn much more! Start-up to 3.8 MW 3.8 MW 6.2 MW operation and pulse length increase

Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct S. Lederer, Beschleunigerbetriebsseminar, Grömitz Cathode operation – #613.1 >Full RF-power reached >A few directional coupler vacuum interlocks >Mainly PM interlocks and majority of them only during changes of RF-power, but they are not necessarily caused by the cathode No information on signal behaviour and height because of pulse transformers (still)! Without them one could learn much more!

Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct Cathode operation – #625.1 No information on signal behaviour and height because of pulse transformers (still)! Without them one could learn much more! >Full RF-power (6.2 MW) at 650  s reached >A few coupler vacuum interlocks >Mainly PM interlocks, during the initial ramp up, but they are not necessarily caused by the cathode

Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct CathodeQE (45 MV/m)QE (60 MV/m) # %11.4 % # %12.2 % # %13.7 % QE measurements – pulsed mode 3.8 MW (FLASH) 6.2 MW (XFEL) Launch phase ~ 38 deg w.r.t. zero crossing (adjusted by hand)

Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct #625.1 Pulsed QE maps at P = 3.8 MW. >Homogeneity especially at edges should be improved! >Trial of a bit higher distance cathode surface – mask (currently 200  m, may be 300  m for next ones >During first real maintenance mask to be investigated #613.1 QE-maps – pulsed mode #22.6

Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct >Dark current level acceptable but still to be improved >dc most probably driven by particles Dark current

Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct >Dark current images at 3.8 MW RF-power >Comparable shapes >One additional emitter visible for cathode #613.1 >Most probable the reason for the increased dc Dark current #22.6 #613.1

Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct >Special tool box for FLASH: >Cs 2 Te photocathode >Mo plug >BGO-scintillator >45 deg mirror Next box to be produced

Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct >Quite successful test of the cathodes >Continued studies necessary – esp. at PITZ >Long term stability >Routinely QE measurements and QE-maps under defined conditions >Full potential of interlock sensors to be used >Thanks for making the tests possible even if it was during the start of the shut-down >Thanks esp. to the guys supporting me during the shifts Closing