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

DR Session Talks

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

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

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

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

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

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

Y. Suetsugu

@ SuperKEKB

IHEP ILC Activities J. Gao Content ILC and CLIC Beam Dynamics ILC Damping Ring Design 3. ATF2 Optics optimization and experiment 4. IHEP Innovation Program Project for 1.3GHz SCRF 5. IHEP Contribution to XFEL “cold mass”: PXFEL1 6. IHEP contributes to CLIC rf Components 7. 4th LC Accelerator School in Beijing 8. Summary IHEP ILC Activities J. Gao ATF2 Q-poles 9-cell LG LL SC Cavity Coupler

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 2010 - CERN LER 2010 - CERN 12

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 2.7-2.8 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 3.70-3.75 nm 0.3 % 4 pm SPEAR3 9.8 nm < 1% 5 pm SPring8 3.4 nm 3.2-3.6 nm 1.9% H; 1.5% V 6.4 pm January 15, 2010 January 15, 2010 LER 2010 - CERN LER 2010 - CERN 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… 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 2.7-2.8 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 3.70-3.75 nm 0.3 % 4 pm SPEAR3 9.8 nm < 1% 5 pm SPring8 3.4 nm 3.2-3.6 nm 1.9% H; 1.5% V 6.4 pm January 15, 2010 January 15, 2010 LER 2010 - CERN LER 2010 - CERN 14

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

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 ILC2010 - Beijing 16 16

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