COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC
description
Transcript of COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC
![Page 1: COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC](https://reader035.fdocuments.net/reader035/viewer/2022081512/5681624c550346895dd2949a/html5/thumbnails/1.jpg)
COPPER PHOTOCATHODESDEVELOPMENTS AT ASTEC
R. ValizadehAccelerator Science and Technology
Centre Science & Technology Facility Council, UK
![Page 2: COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC](https://reader035.fdocuments.net/reader035/viewer/2022081512/5681624c550346895dd2949a/html5/thumbnails/2.jpg)
• Overview of work done at other accelerator centres
• Photocathode preparation program at Daresbury Lab
Outline
2
![Page 3: COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC](https://reader035.fdocuments.net/reader035/viewer/2022081512/5681624c550346895dd2949a/html5/thumbnails/3.jpg)
Important Properties of Photocathodes• High Quantum efficiency • Fast response time• Uniform emission• Low as possible emittance (atomically flat)
• Have reasonably high operating life time
at vacuum level 10-9 to 10-10 Torr range.• Easy to fabricate, reliable, reproducible QE
and emittance after cathode cleaning and re-activation.
![Page 4: COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC](https://reader035.fdocuments.net/reader035/viewer/2022081512/5681624c550346895dd2949a/html5/thumbnails/4.jpg)
Why Metal Photocathodes• Metal cathodes have fast response time
10-15 to 10-14 seconds.• They are robust and can survive years at
high cathode fields to produce high brightness beam
• However due to the high work function UV photons are needed for reasonable QE.
![Page 5: COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC](https://reader035.fdocuments.net/reader035/viewer/2022081512/5681624c550346895dd2949a/html5/thumbnails/5.jpg)
Metal Photocathodes
![Page 6: COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC](https://reader035.fdocuments.net/reader035/viewer/2022081512/5681624c550346895dd2949a/html5/thumbnails/6.jpg)
QE and thermal emittance
![Page 7: COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC](https://reader035.fdocuments.net/reader035/viewer/2022081512/5681624c550346895dd2949a/html5/thumbnails/7.jpg)
Variation of Emittance and QE with laser wavelength and spot size
![Page 8: COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC](https://reader035.fdocuments.net/reader035/viewer/2022081512/5681624c550346895dd2949a/html5/thumbnails/8.jpg)
Effect of surface roughness on Emittance.
![Page 9: COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC](https://reader035.fdocuments.net/reader035/viewer/2022081512/5681624c550346895dd2949a/html5/thumbnails/9.jpg)
Survivability and lifetime
![Page 10: COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC](https://reader035.fdocuments.net/reader035/viewer/2022081512/5681624c550346895dd2949a/html5/thumbnails/10.jpg)
Dependence of lifetime on residual operating gas species
![Page 11: COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC](https://reader035.fdocuments.net/reader035/viewer/2022081512/5681624c550346895dd2949a/html5/thumbnails/11.jpg)
Effect of laser surface cleaning for restoring QE
![Page 12: COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC](https://reader035.fdocuments.net/reader035/viewer/2022081512/5681624c550346895dd2949a/html5/thumbnails/12.jpg)
H-ion bombardment and Ozone
![Page 13: COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC](https://reader035.fdocuments.net/reader035/viewer/2022081512/5681624c550346895dd2949a/html5/thumbnails/13.jpg)
Annealing and Ar plasma Cleaning
13
![Page 14: COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC](https://reader035.fdocuments.net/reader035/viewer/2022081512/5681624c550346895dd2949a/html5/thumbnails/14.jpg)
Photocathode preparation and diagnostic system
![Page 15: COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC](https://reader035.fdocuments.net/reader035/viewer/2022081512/5681624c550346895dd2949a/html5/thumbnails/15.jpg)
QE Measurment setup
![Page 16: COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC](https://reader035.fdocuments.net/reader035/viewer/2022081512/5681624c550346895dd2949a/html5/thumbnails/16.jpg)
Vacuum suitcase for transportation of prepared photocathode to RF Gun.
![Page 17: COPPER PHOTOCATHODES DEVELOPMENTS AT ASTEC](https://reader035.fdocuments.net/reader035/viewer/2022081512/5681624c550346895dd2949a/html5/thumbnails/17.jpg)
Initial Programme• Establish reliable and reproducible sample preparation
procedure to minimise the final surface carbon contamination. (done at SLAC)
• Prepare atomic flat surfaces for single crystal and poly-crystalline copper.
• Produce engineered rough surface.• Determine QE for different method of surface regeneration
(Ar, H and Ozone cleaning)• Determination of surface roughness after each procedure.• Identify the effect each individual residual gas species(H2,
CO, CO2, H2O and CH3) on QE degradation.• Optimization of wide band gap coating (CsBr) on copper.• Study the effectiveness of the Vacuum suitcase.