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

2. Cathode System in SRF Project
Preparation chamber
Transport chamber
Cathode cooling system

3. 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
CARE Meeting 2005

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

5. 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

6. 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)

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

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

9. First test in new chamber
No.
Sub.
Thick. Te
Thick. Cs
Cs/Te
PIXE
RBS # Cu
10 nm
20 nm
0.55
0.44 #
68 nm \
1.9 # Si
70 nm
1.6 #
46 nm
0.8

10. Our homepage

11. 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

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

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

14. 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)

15. 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…)

16. Thank you!