1. SRF Gun at ELBE Work package 10, Task 7 Jochen Teichert
Forschungszentrum Dresden-Rossendorf (FZD)
Dresden, Germany
EuCARD/SRF Kick-off meeting at DESY, Hamburg, March 24, 2009

2. 7.1 HZB, FZD HZB T. Kamps 7.2 FZD R. Xiang 7.3 FZD, HZB J. Teichert
Task - SRF ELBE
1. Subtasks and Collaboration Partners
Leading lab: Forschungszentrum Dresden-Rossendorf (FZD); J. Teichert
Collaborating lab: Helmholz Zentrum Berlin (BESSY); Thorsten Kamps
Subtask
Title
collaborators
responsible
contact
person
7.1
slice emittance,
installation +measurement
HZB, FZD
HZB
T. Kamps
7.2
preparation + application
of GaAs photo cathodes
FZD
R. Xiang
7.3
evaluation of critical issues of SRF guns
FZD, HZB
J. Teichert

3. ELBE layout SRF Gun thermionic DC Gun
Task SRF ELBE - SRF gun status
laser
ELBE layout
thermionic DC
Gun
SRF Gun 3

4. SRF Gun operation in 2008 Task SRF gun @ ELBE - SRF gun status
gradient Eacc = 5 MV/m, Ee = 2 MeV
next run in 2009:
Higher gradient 6.5 MV/m
Gun operation with Ee = 3 MeV
Optimized laser spot size (2.7 mm -> 5.2 mm)
Transverse Emittance – Solenoid scan
screen DV02 (YAG)
1.9 m from gun exit,
2.7 m from cathode
-175°,
σx = 300 µm
-150°,
σx = 330 µm
-130°,
σx = 610 µm
-115°,
σx = 760 µm
-95°,
-65°,
σx = 430 µm
+3°,
σx = 1650 µm
laser phase scan

5. Results of slice measurements
Task SRF ELBE - Subtask 7.1
Slice emittance measurement using a correlated energy spread by ELBE modules
beamline to ELBE
spectrometer magnet
status
installation
funding
Beamline to ELBE
design ready
10/2009
FZD lab budget
Spectrometer magnet
ordered
7/2009
Installation spectrometer dipole
Milestone
9/2010
Spectrometer diagnostic
3/2010
HZB / EuCard
Results of slice measurements
Deliverable
3/2011

6. alternative for the ILC electron source
Subtask 7.2 – GaAs photo cathodes
Motivation: high-brightness & high-average-current gun for polarized electrons
alternative for the ILC electron source
A SRF gun may provide the vacuum
required for GaAs photo cathodes by the
cryopumping of the cavity.
In the RF field the ion backbombardment
is reduced compared to exisiting DC guns.
A similar experiment will be
carried out at BNL
Courtesy A. Burrill

7. Existing equipment for Cs2Te photo cathodes
Subtask 7.2 – GaAs photo cathodes
Existing equipment for Cs2Te photo cathodes
Take a cathode from the carrier
Transfersystem at gun while backing
Cathode moved with transfer stem
Transfersystem in cathode preparation lab

8. work aim finished vacuum < 10 -9 mbar particlefree
Subtask 7.2 – GaAs photo cathodes
vacuum < mbar
particlefree
work
aim
finished
improvement of transfer systems
NEG pump, backing
p<10-10 mbar
4/2009
Cathode preparation
C2Te cathodes
with high QE
until 9/2009
Modification of preparation system
GaAs substrate, etc.
3/2010
Prep. system for GaAs finished
Milestone
GaAs photo cathodes produced
3/2011
Results of GaAs PC in SRF gun
Deliverable
12/2011

9. perhaps > 2 mA in macropulse mode (dump current limit)
Subtask 7.3 – Critical issues of SRF guns
High-average current operation SRF guns
up to 1 mA in CW operation,
perhaps > 2 mA in macropulse mode (dump current limit)
cavity performance
HOM production and damping
photo cathode behavior and life time
RF problems, input coupler etc.
Photo cathode studies in SRF guns
QE and thermal emittance
life time, dark current
alternative photo cathodes, metallic, CsKNb?
Study of emittance compensation methods
RF focusing (backdrawn & shaped cathode)
External Solenoid
RF issues connected to the TE mode
no milestones and deliverables

10. FZD PM 2009 2010 2011 2012 Subtask 7.2 FZD EC Costs and EU support
Task 7.3 – SRF ELBE
Costs and EU support
lab
total
EC funding
FZD € €
HZB (BESSY)
16 pm
10 pm
FZD
HZB
Additional Personnel
FZD PM
2009
2010
2011
2012
Subtask 7.2
FZD EC

11. Task - SRF ELBE
Deliverables: Results of slice measurements Report M24
Results for GaAs photo cathodes Report M33
Milestones: Preparation system for GaAs finished O M12
Installation spectrometer dipole O M18
GaAs photo cathodes produced D 24