1. Damping Ring Summary S. Guiducci, M. Palmer, M. Pivi, J. Urakawa
ILC10, Beijing
30 March 2010
Global Design Effort

2. DR Session Talks

3. Report only on Highlights
DR Session Talks
All the talks on INDICO
Report only on Highlights

4. DR Lattices 6.4 km DCO4 3.2 km DSB3 LNF 3.2 km DMC1 72° FODO
All racetrack, same straight section layout
6.4 km well assessed
3.2 km optimization in progress
IHEP
Cockroft Institute

5. 15E/W Comparison – e+ Un-normalized Normalized According to Simulation
1x20 e+, 5.3GeV, 14ns, drift
Central collectors (4-6) only
Note: Al signal is divided by 4
15W location (amorphous C) sees about 2.4× the photon flux of the 15E (TiN) location
At high bunch charges, normalization to photon flux insufficient a normalize based on a simulation of the ratio of fluxes
TiN and a-C are comparable, both much better than Al
Note: Both chambers show a similar dP/dI which is worse than our Al chambers
Un-normalized
Normalized According to Simulation
Normalized to photon flux
March 28, 2010
March 28, 2010
ILC2010, Beijing
ILC2010, Beijing 5

6. Conclusion The CESR reconfiguration for CesrTA is complete
Low emittance damping ring layout
4 dedicated experimental regions for EC studies with significant flexibility for collaborator-driven tests
Instrumentation and vacuum diagnostics installed (refinements ongoing)
Recent results include:
Machine correction to ey ~ 31pm (within factor of ~1.5 of target)
EC mitigation comparisons
First single-pass bunch-by-bunch beam size measurements to characterize emittance diluting effects
Extensive progress on EC simulations
~70 machine development days scheduled in 2010 – May, July, September and December experimental periods. Will focus on:
Fully exploiting our new ring instrumentation
LET effort to reach a target emittance of ey≤ 20pm
Completion of our targeted EC mitigation studies
Detailed characterization of instabilities and sources of emittance dilution in the ultra low emittance regime (EC-induced incoherent emittance growth, IBS studies)
Application of our results to the damping rings design effort
March 28, 2010
March 28, 2010
ILC2010, Beijing
ILC2010, Beijing 6 6

7. Output Waveform: No Post-pulse
Opening Switch Program
Functionally similar to DSRD systems marketed by FID GmbH
“Open source” design
2-ns prototype demonstrated (FY08)
Developing 4-ns modulator for ATF2
5 ns
Active clamping to eliminate post-pulse
SLAC DR Kicker Modulator Update for ILC2010
Page 7
C. Burkhart, A. Krasnykh, & T. Tang

8. Multi-bunch beam extraction by the Fast kicker
Kick angle was stable as 4x10-4 < ILC requirement.
Further improvements of the HV pulser should be done for multi-bunch extraction.
in DR:
3 Trains,
9(max 10) bunches/train with 5.6 nsec spacing
Extracted:
27(max 30) bunches with 308 ns spacing
bunch-by-bunch profile follows that in the DR.
bunches were extracted from the last bunch to the first bunch.
11/14/2018 8

9. Y. Suetsugu

10. @ SuperKEKB

11. IHEP ILC Activities J. Gao Content ILC and CLIC Beam Dynamics
ILC Damping Ring Design
ATF2 Optics optimization and experiment
IHEP Innovation Program Project for 1.3GHz SCRF
IHEP Contribution to XFEL “cold mass”: PXFEL1
IHEP contributes to CLIC rf Components
th LC Accelerator School in Beijing
Summary
IHEP ILC Activities
J. Gao
ATF2 Q-poles
9-cell LG LL SC Cavity
Coupler

12. LER10 “Low Emittance Rings Workshop” Summary
Have Our Hopes Been Met?
LER10 “Low Emittance Rings Workshop” Summary
Bringing together experts…
70 registered participants representing a cross section of all the major groups working on low emittance rings
Profiting from experience…
56 presentations highlighting critical design issues for low emittance electron and positron rings
An impressive range of observations from light sources, B factories and test facilities presented
Clear areas of mutual interest identified
Many design issues highlighted
There appear to be many synergies between plans being developed for future light source development and the plans for low emittance high energy physics rings
All leading to…
a range of animated discussions
exploration of possibilities for collaboration
Y. Papaphilippou
January 15, 2010
January 15, 2010
LER CERN
LER CERN 12

13. Profiting from Experience – an example:
Have Our Hopes Been Met?
Profiting from Experience – an example:
Major concern for damping ring teams has been the attainability of the targeted ultra low emittance parameters
Following table has been shown twice already…
Model emittance
Measured emittance
-beating (rms)
Coupling*
(y/ x)
Vertical emittance
ALS
6.7 nm
0.5 %
0.1%
4-7 pm
APS
2.5 nm
1 %
0.8%
20 pm
ASP
10 nm
0.01%
1-2 pm
CLS
18 nm
17-19 nm
4.2%
0.2%
36 pm
Diamond
2.74 nm nm
0.4 %
0.08%
2.2 pm
ESRF
4 nm 1%
0.25%
10 pm
SLS
5.6 nm
5.4-7 nm
4.5% H; 1.3% V
0.05%
2.8 pm
SOLEIL
3.73 nm nm
0.3 %
4 pm
SPEAR3
9.8 nm
< 1%
5 pm
SPring8
3.4 nm nm
1.9% H; 1.5% V
6.4 pm
January 15, 2010
January 15, 2010
LER CERN
LER CERN 13

14. Profiting from Experience – an example:
Have Our Hopes Been Met?
Profiting from Experience – an example:
Major concern for damping ring teams has been the attainability of the targeted ultra low emittance parameters
Following table has been shown twice already…
Vertical emittance in the range required for the ILC Damping Rings has been demonstrated
Demonstrated emittances are also very similar to the values proposed for the Super B factories
Values are rapidly approaching the CLIC damping ring regime!
Plans for future light sources are in even closer proximity to the damping ring parameters
a Greatly improves our confidence in the proposed designs!
Model emittance
Measured emittance
-beating (rms)
Coupling*
(y/ x)
Vertical emittance
ALS
6.7 nm
0.5 %
0.1%
4-7 pm
APS
2.5 nm
1 %
0.8%
20 pm
ASP
10 nm
0.01%
1-2 pm
CLS
18 nm
17-19 nm
4.2%
0.2%
36 pm
Diamond
2.74 nm nm
0.4 %
0.08%
2.2 pm
ESRF
4 nm 1%
0.25%
10 pm
SLS
5.6 nm
5.4-7 nm
4.5% H; 1.3% V
0.05%
2.8 pm
SOLEIL
3.73 nm nm
0.3 %
4 pm
SPEAR3
9.8 nm
< 1%
5 pm
SPring8
3.4 nm nm
1.9% H; 1.5% V
6.4 pm
January 15, 2010
January 15, 2010
LER CERN
LER CERN 14

15. Compare thresholds for 6 km and 3km DR
ECLOUD WG
SEY 1.4
SEY 1.2
antechamber
antechamber
Simulation Campaign 2010: compiled data of build-up simulations compared with the simulated beam instability thresholds. Overall ring average cloud densities are shown for the 6 km and 3 km rings. The surface Secondary Electron Yield (SEY) determines the cloud build-up and density level.
LCWS10
M. Pivi 15

16. Base for Recommendation and Risk Assessment
With respect to the RDR baseline, the EC risk level for adopting a reduced 3km Damping Ring while maintaining the same bunch spacing is: Low.
The acceptable surface Secondary Electron Yield (SEY) may strongly depend on issues not yet thoroughly investigated such as beam jitter and slow incoherent emittance growth. Refined estimations of the photoelectron production rate by simulations will better define the maximum acceptable SEY.
Reducing the positron ring circumference to 3-km eliminates the back up option of 12 ns bunch spacing (safer e- cloud regime) and may reduce the luminosity margins.
In the event that effective EC mitigations cannot be devised for a 3km damping ring, an option of last resort would be to add a second positron damping ring.
March 29, 2010
ILC Beijing 16 16

17. High Repetition Rate Option
A 10Hz repetition rate has been proposed to increase low energy luminosity
This appears to be a reasonable option for the 3.2km configuration
8 damping times needed to reduce vertical emittance
5 Hz  x = 26 ms
10 Hz  x = 13 ms
Increase wiggler field
Reduce wiggler period
Double the number of RF cavities