slide1
Download
Skip this Video
Download Presentation
WSHQE Oct. 5, 2006 Klaus Floettmann

Loading in 2 Seconds...

play fullscreen
1 / 13

K. Floettmann - PowerPoint PPT Presentation


  • 206 Views
  • Uploaded on

Photo cathode requirements for the European XFEL. WSHQE Oct. 5, 2006 Klaus Floettmann. A lifetime of some month with a QE > 0.5% is required. This is achieved with Cs 2 Te Cathodes e.g. at Flash. Can we go home now? . QE and Lifetime requirements.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'K. Floettmann' - sheng


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

Photo cathode requirements for the European XFEL

WSHQE

Oct. 5, 2006

Klaus Floettmann

WSHQE, OCT. 5, 2006

qe and lifetime requirements
A lifetime of some month with a

QE > 0.5% is required.

This is achieved with Cs2Te Cathodes e.g. at Flash.

Can we go home now?

QE and Lifetime requirements

WSHQE, OCT. 5, 2006

problem i
roughly half of the predicted emittance of the XFEL injector is due to the thermal emittance of the cathodeProblem I:

WSHQE, OCT. 5, 2006

development of the transverse emittance
Development of the transverse Emittance
  • 1nC charge
  • uniform transverse distribution
  • longitudinal flat-top with 2 ps rise time
  • incl. thermal emittance

WSHQE, OCT. 5, 2006

slice emittance at the injector exit
Slice Emittance at the Injector exit

emittance in longitudinal slices of the bunch

WSHQE, OCT. 5, 2006

slice emittance at the injector exit6
Slice Emittance at the Injector exit

w.o. thermal emittance

WSHQE, OCT. 5, 2006

slide7
The measured thermal emittance is even higher than expected from simple theoretical predictions (Schottky effect, cathode roughness)

How can we reduce the thermal emittance?

reduce cathode roughness

control the work function

…?

WSHQE, OCT. 5, 2006

dark current extrapolation to 60 mv m
Dark Current extrapolation to 60 MV/m

no conditioning effect taken into account

WSHQE, OCT. 5, 2006

slide10
A large fraction of the dark current is generated at or near the cathode. Collimation at low energies is very difficult because the dark current has similar properties as the beam

How can we reduce the dark current generation

reduce cathode roughness

reduce number of emitters by better cleaning techniques

…?

WSHQE, OCT. 5, 2006

dry ice cleaning principle
Dry Ice Cleaning Principle

cold Nitrogen

CO2

WSHQE, OCT. 5, 2006

co2 nozzle
CO2 Nozzle

WSHQE, OCT. 5, 2006

slide13
No field emission was observed up to 90 MV/m on dry ice cleaned Cu samples in field emission scans.

Dry ice cleaning of the gun cavity is in preparation.

Dry Ice Cleaning of the cathode plugs should be tested next.

To monitor the deposition of field emitters during the cathode preparation process a field emission scanning apparatus for the cathodes will be designed and build in collaboration with the University of Wuppertal.

WSHQE, OCT. 5, 2006

ad