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Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct. 2011 First Photocathodes from DESY Sven Lederer PITZ-Collaboration meeting 27 th -28 th of Oct 2011
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Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct. 2011 Preparation system Set-up for QE-measurements and -maps port for transport box/ load-lock port for future SAFEM preparation chamber
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Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct. 2011 >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
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Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct. 2011 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) #22.63.54 eV1.877.89 % #613.13.66 eV1.210.23 % #625.13.611.311.12 %
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Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct. 2011 #625.1 #22.6#613.1
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Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct. 2011 S. Lederer, Beschleunigerbetriebsseminar, Grömitz 26.-29.09.2011 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 operation @ 3.8 MW 6.2 MW operation and pulse length increase
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Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct. 2011 S. Lederer, Beschleunigerbetriebsseminar, Grömitz 26.-29.09.2011 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!
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Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct. 2011 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
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Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct. 2011 CathodeQE (45 MV/m)QE (60 MV/m) #22.611.0 %11.4 % #613.19.6 %12.2 % #625.113.5 %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)
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Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct. 2011 #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
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Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct. 2011 >Dark current level acceptable but still to be improved >dc most probably driven by particles Dark current
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Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct. 2011 >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
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Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct. 2011 >Special tool box for FLASH: >Cs 2 Te photocathode >Mo plug >BGO-scintillator >45 deg mirror Next box to be produced
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Sven LedererPITZ-Collaboration meeitng 27 th -28 th of Oct. 2011 >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
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