CESR as a Vehicle for ILC Damping Rings R&D Mark Palmer Cornell Laboratory for Accelerator-Based Sciences and Education

International Linear Collider Overview Outline International Linear Collider Overview Preparing for the Engineering Design Report (EDR) ILC R&D at Cornell CesrTA Proposal ILC Damping Rings Overview Damping Rings R&D Using CESR Concept and Goals Ring Modifications Parameters and Experimental Reach Collaborators Damping Rings Projects Schedule Synergies with Other Parts of the CLASSE Program Acknowledgments and Conclusion April 22, 2019 CesrTA Seminar

The ILC Basic Numbers Machine Configuration 500 GeV – upgradeable to 1 TeV 14 kHz Collision Rate Luminosity: 2x1034 cm-2s-1 31 km end-to-end length 31.5 MV/m SRF cavities 16K Cavities 2K Cryostats Machine Configuration Helical Undulator polarized e+ source Two 6.7 km damping rings in central complex RTML running length of linac 11.2 km Main Linac Single Beam Delivery System 2 Detectors in Push-Pull Configuration April 22, 2019 CesrTA Seminar

ICFA Release of Reference Design Report (RDR) ILC Program ICFA Release of Reference Design Report (RDR) Release Date: February 8, 2007 Draft available at: http://www.linearcollider.org Press Release: http://www.interactions.org/cms/?pid=1024912 RDR Cost Estimate (accelerator complex): $1.8bn site costs (eg, tunneling) $4.9bn technology and component costs 13K person-years of effort (personnel costs not in above numbers) Start of the Engineering Design Phase Engineering Design Report (EDR) in early 2010 Complete critical R&D (eg, SRF cavity gradient yield for ML, electron cloud and fast kicker technology for DR) Basic engineering design April 22, 2019 CesrTA Seminar

ILC R&D at Cornell R&D Efforts Also management contributions Helical Undulator Polarized Positron Source Ring-to-Main Linac Low Emittance Transport (RTML and Main Linac) Damping Rings SRF Detector (TPC) Also management contributions April 22, 2019 CesrTA Seminar

ILC Damping Rings R&D Overview Simulation Electron Cloud and Ion Effects Technical Systems (wigglers, kickers, instrumentation…) CesrTA Development BCD and RDR Support J. Alexander, M. Billing, G. Codner, J. Crittenden, G. Dugan, M. Ehrlichman, D. Hartill, R. Helms, R. Holtzapple, J. Kern, Y. Li, R. Meller, M. Palmer, D. Rice, D. Rubin, D. Sagan, L. Schachter, J. Shanks, E. Tanke, M. Tigner, J. Urban (note: 5 students) J. Urban April 22, 2019 CesrTA Seminar

International Linear Collider Overview Outline International Linear Collider Overview Preparing for the Engineering Design Report (EDR) ILC R&D at Cornell CesrTA Proposal ILC Damping Rings Overview Damping Rings R&D Using CESR Concept and Goals Ring Modifications Parameters and Experimental Reach Collaborators Damping Rings Projects Schedule Synergies with Other Parts of the CLASSE Program Acknowledgments and Conclusion April 22, 2019 CesrTA Seminar

The ILC Damping Rings Beam energy 5 GeV Circumference 6695 m RF frequency 650 MHz Harmonic number 14516 Injected (normalised) positron emittance 0.01 m Extracted (normalised) emittance 8 μm × 20 nm Extracted energy spread <0.15% Average current 400 mA Maximum particles per bunch 2×1010 Bunch length (rms) 6 mm 9mm Minimum bunch separation 3.08 ns OCS v6 TME Lattice 2 pm-rad geometric emittance 250 km main linac bunch train is “folded” into the DRs Circled items play a key role in our local R&D plans… April 22, 2019 CesrTA Seminar

RDR Version of ILC DR Layout e- ring circulates in opposite direction in same central tunnel April 22, 2019 CesrTA Seminar

RDB S3 Very High Priorities Lattice design for baseline positron ring Lattice design for baseline electron ring Demonstrate < 2 pm vertical emittance Characterize single bunch impedance-driven instabilities Characterize electron cloud build-up Develop electron cloud suppression techniques Develop modelling tools for electron cloud instabilities Determine electron cloud instability thresholds Characterize ion effects Specify techniques for suppressing ion effects Develop a fast high-power pulser April 22, 2019 CesrTA Seminar

Moving to a Single Positron DR M. Pivi ILCDR06 No additional suppression techniques assumed in dipoles and wigglers! Cloud density near (r=1mm) beam (m-3) before bunch passage, values are taken at a cloud equilibrium density. Solenoids decrease the cloud density in DRIFT regions, where they are only effective. Compare options LowQ and LowQ+train gaps. All cases wiggler aperture 46mm. April 22, 2019 CesrTA Seminar

Suppressing Electron Cloud in Wigglers Submitted to PRSTAB Design & test of impedance is under the way, test in PEPII Dipole & CESR Wiggler Strip-line type Wire type Suetsugu’s talk Calculation of the impedance ( Cho, Lanfa) Wire type L. Wang ILCDR06 Strip-line type April 22, 2019 CesrTA Seminar

ILCDR R&D Issues and CesrTA Some High and Very High Priority R&D Items that Can Be Addressed at CesrTA… Electron Cloud Growth in quadrupoles, dipoles, and wigglers Suppression in quadrupoles, dipoles, and wigglers Instability thresholds and emittance growth in the positron damping ring This issue has become more significant due to the decision to employ a single positron damping ring Ion Effects Instability thresholds and emittance growth in the electron damping ring Ultra-low Emittance Operation Alignment and Survey Beam-based Alignment Optics Correction Measurement and Tuning Fast (single bunch) high voltage kickers for injection/extraction >100 kV-m of stripline kick required <6 ns wide pulse into a 0.3 m long stripline so as not to perturb neighboring bunches in the damping ring Development of 650 MHz SRF System April 22, 2019 CesrTA Seminar

Reconfigure CESR as a damping ring test facility CesrTA Concept Reconfigure CESR as a damping ring test facility Move wigglers to zero dispersion regions for low emittance operation Open up space for insertion devices and instrumentation Provide an R&D program that is complementary to work going on elsewhere (eg, KEK-ATF) Provide a vehicle for: R&D needed for EDR decisions (EDR R&D completion by end of 2009 is ILC target) Operating and tuning experience with ultra-low emittance beams DR technical systems development Provide significant amounts of dedicated running time for damping ring experiments April 22, 2019 CesrTA Seminar

CesrTA Operating Model Experimental Model Collaboration among international researchers (similar to HEP collaborations) Cornell provides machine infrastructure and support Cornell provides operations staff Scheduling Model Provide multiple dedicated experimental periods each year Provide sufficient scheduled down time to flexibly upgrade machine and install experimental apparatus Alternate running periods with CHESS April 22, 2019 CesrTA Seminar

CesrTA Ring Modifications Place all wigglers in zero dispersion regions Wigglers in L1 and L5 straights can remain in place Emittance scaling for wiggler dominated ring: Vacuum system modifications Electron cloud and ion diagnostics Synchrotron x-ray dump for high energy operation of part of the wiggler complement Remove 4 of 6 electrostatic separators Upgrade instrumentation and diagnostics for planned experiments Feedback system modifications for 4 ns bunch spacing April 22, 2019 CesrTA Seminar

CESR Modifications Move 6 wigglers from the CESR arcs to the South IR (zero dispersion region around CLEO) NOTE: this is a recent change in plans Instrumentation and feedback upgrades April 22, 2019 CesrTA Seminar

The South IR South IR Modifications: Remove CLEO drift chambers Instrumented vacuum chambers for local electron cloud diagnostics Eventual test location for prototype ILC damping wiggler and vacuum chambers April 22, 2019 CesrTA Seminar

Instrumentation for Ultra-Low Emittance Measurement Typical Beam Sizes Vertical: sy~10-12 mm Horizontal: sx ~ 80 mm (at a zero dispersion point) Have considered laserwire and X-ray profile monitors Fast X-ray imaging system (Alexander) Core diagnostic for CesrTA – high resolution and bunch-by-bunch capability Plan for integrating systems into CHESS lines First pinhole camera tests were successful! (see next slide) Laserwire CESR-c fast luminosity monitor offers window suitable for laserwire use Detector potentially could be used for fast segmented readout of Compton photon distribution April 22, 2019 CesrTA Seminar

GaAs Detector for X-ray Imaging First bunch-by-bunch beam size data in CHESS conditions a Significant CHESS support Signal (ADC Counts) = 142 +/- 7 mm Different symbols represent different bunches Pinhole camera setup at B1 hutch Fast enough for single bunch resolution Position (mm) NEW: GaAs arrays from Hamamatsu 1x512 linear array 25 mm pitch 1st sample has recently arrived April 22, 2019 CesrTA Seminar

CesrTA Beamsize Monitor Concept Simple optics High transmission 2 keV operation (works for both 2 GeV and 5 GeV) Hundreds (2 GeV) to thousands (5 GeV) of photons per bunch passage Explore other detector possibilities (eg, InSb arrays) Collaboration with CHESS colleagues for optics and device development as well as integration with existing Xray lines p q 25um Be detector zone plate Multilayer W/C mirrors; April 22, 2019 CesrTA Seminar

CESR Modifications Summary How extensive are the modifications? Significant changes to the South IR (however, certainly no more difficult than a detector and IR magnet upgrade) Conversion is relatively modest Core ring modifications will take place in a single down period Mid-2008 <3 months duration Carry out key preparation work between now and April 2008 April 22, 2019 CesrTA Seminar

Experimental Reach Baseline Lattice Parameter Value E 2.0 GeV Nwiggler 12 Bmax 2.1 T ex 2.25 nm Qx 14.59 Qy 9.63 Qz 0.075 sE/E 8.6 x 10-4 tx,y 47 ms sz (with VRF=8.5MV) 9 mm ac 6.4 x 10-3 tTouschek(Nb=2x1010) >10 minutes April 22, 2019 CesrTA Seminar

Tune scans used to identify suitable working points Qx~14.59 Qy~9.63 April 22, 2019 CesrTA Seminar

Zero current ex (nm-rad) Alternate Optics Have explored a range of optics for machine transition and physics studies Layout Energy (GeV) Bpeak (T) No. Wigglers Zero current ex (nm-rad) CesrTA 2.0 2.1 12 1.8 CESR-c 6 6.5 1.9 2.5 3.2 1.5 1.4 1.3 5.0 26 April 22, 2019 CesrTA Seminar

Lattice Evaluation Dynamic aperture 1 damping time Injected beam fully coupled ex = 1 mm ey = 500 nm Alignment sensitivity and low emittance correction algorithms Simulations based on achieving nominal CESR alignment resolutions Misalignment Nominal Value Quadrupole, Bend and Wiggler Offsets 150 mm Sextupole Offsets 300 mm Quadrupole, Bend, Wiggler and Sextupole Rotations 100 mrad April 22, 2019 CesrTA Seminar

Vertical Emittance Sensitivities (Selected Examples) April 22, 2019 CesrTA Seminar

Low Emittance Operations Have evaluated our ability to correct for ring errors with the above lattice Goal: ey~5-10 pm at zero current Simulation results indicate that we can reasonably expect to meet our targets Nominal Values Correction Type Average Value 95% Limit Orbit Only 10.2 pm 21.4 pm Orbit+Dispersion 3.9 pm 8.2 pm April 22, 2019 CesrTA Seminar

IBS Evaluation (2 GeV Baseline Lattice) Transverse emittance growth for different contributions of coupling and dispersion to the vertical emittance Baseline lattice Compare different corrected optics assumptions 9 mm bunch length Energy flexibility of CESR and g-4 IBS dependence offers a flexible way to study, control and understand IBS contributions to emittance relative to other physics under consideration April 22, 2019 CesrTA Seminar

CesrTA Research Directions Core Efforts Electron Cloud Growth Studies – particularly in the CESR-c wigglers Bunch trains similar to those in the ILC DR Vacuum chambers with mitigation techniques and diagnostics Ultra low Emittance Operation Alignment and Survey Beam-based Alignment Optics Correction Measurement and Tuning Beam Dynamics Studies Detailed inter-species comparisons (use to distinguish electron cloud, ion and wake field effects) Characterize emittance growth in ultra-low emittance beams (electron cloud, ion effects, IBS, …) Test and Demonstrate Key Damping Ring Technologies Wiggler vacuum chambers, optimized wigglers, diagnostics, … April 22, 2019 CesrTA Seminar

Proposal Collaborators Institution Topic M. Pivi and L. Wang SLAC Electron cloud studies, wiggler chambers for electron cloud suppression Y. Cai and PEP-II Beam Physics Group Machine correction and ultra-low emittance tuning A. Reichold and D. Urner Oxford Alignment and survey requirements and upgrades S. Marks and R. Schlueter and M. Zisman LBNL Wiggler chambers for electron cloud suppression C. Celata, M. Furman and M. Venturini Simulation of electron cloud in wigglers A. Molvik LLNL Electron cloud measurements J. Byrd, S. de Santis, M. Venturini, and M. Zisman Wiggler and electron cloud and FII studies K. Harkay ANL J. Flannagan, K. Ohmi, N. Ohuchi, K. Shibata, Y. Suetsugu, and M. Tobiyama KEK Electron cloud measurements and simulation P. Spentzouris, J. Amundsen and L. Michelotti FNAL Beam dynamics simulations and measurements A. Wolski Cockcroft Inst. R. Holtzapple Alfred Univ. Instrumentation and beam measurements J. Urakawa R&D program coordination L. Schächter Technion-Haifa Electron cloud measurements and analysis Letters of intent from ~30 collaborators for direct work on CesrTA April 22, 2019 CesrTA Seminar

CESR-c Wiggler Modifications Initial vacuum tests in CesrTA Remove Cu beam-pipe Replace with beam-pipe having ECE suppression and diagnostics hardware CU/SLAC/LBNL Collaboration Prototype Optimized ILC Wiggler and Vacuum Chamber Cornell/LBNL Collaboration April 22, 2019 CesrTA Seminar

Wiggler Design Basic Requirements Large Aperture Physical Acceptance for injected e+ beam Improved thresholds for collective effects Electron cloud Resistive wall coupled bunch instability Dynamic Aperture Field quality Wiggler nonlinearities Have carried out a series of physics studies with an eye towards the engineering develop an optimized wiggler design which we hope will lead to an ILC prototype Dynamic aperture studies using OCS2 April 22, 2019 CesrTA Seminar

Superferric ILC-Optimized CESR-c Wiggler Optimized Wiggler Superferric ILC-Optimized CESR-c Wiggler 12 poles (vs 14) Period = 32 cm (vs 40) Length = 1.68 m (vs 2.5) By,peak = 1.95 T (vs 1.67) Gap = 86 mm (vs 76) Width = 238 mm I = 141 A tdamp = 26.4 ms ex,rad = 0.56 nm·rad sd = 0.13 % Misses nominal target (25 ms) April 22, 2019 CesrTA Seminar

Engineering Issues Cryogenics Modifications Shorter Unit Indirect cooling for cold mass Switch to cold He gas for cooling thermal shields 42% of manpower for inner cryostat and stack assembly a significant cost reduction expected Shorter Unit Simplified and more robust yoke assembly Significant cost reduction 14 % fewer poles 30% reduction in length Larger aperture Relaxed constraints on warm vacuum chamber interface with cryostat Estimated cost savings relative to RDR value: ~25% Wiggler Information: https://wiki.lepp.cornell.edu/ilc/bin/view/Public/CesrTA/WigglerInfo April 22, 2019 CesrTA Seminar

EC in Wiggler Vacuum Chamber The multipacting strips of electron cloud in the wigglers is more close to the beam L. Wang, ILCDR06 Wiggler Dipole, B=0.194T April 22, 2019 CesrTA Seminar

Wiggler Trajectory Note that CESR beam trajectory significant relative to stripe spacing at 2GeV Diagnostics Ideally should be capable of roughly millimeter transverse resolution Longitudinal segmentation to cleanly sample stripe 4mm April 22, 2019 CesrTA Seminar

Diagnostic Wiggler Chamber Concept Integral RFA Expect to make several variants to explore Electrodes Grooves Coatings Modify existing extrusions Clearing Electrode Clearing Electrode 1.5mm slot spacing RFA sections 31mmx38mm sampling central fields of wiggler April 22, 2019 CesrTA Seminar

Survey and Alignment Rapid Tunnel Reference Surveyor (RTRS) Concept Proposal submitted for ILC DR alignment and survey studies using CesrTA wall markers internal FSI SM beam external FSI Tunnel Wall Reichold D. Urner LiCAS technology for automated stake-out process Reconstructed tunnel shapes (relative co-ordinates) collider component April 22, 2019 CesrTA Seminar

Electron Cloud (and Ion) Studies Electron Cloud and Ion Studies Underway Utilize multi-bunch turn-by-turn instrumentation Beam profile monitors Beam position monitor Collaborator Participation Sept. 2006: M. Pivi Jan. 2007: K. Harkay (ANL), J. Flanagan (KEKB), A. Molvik (LLNL) April 22, 2019 CesrTA Seminar

e+ Beam Size vs Bunch Current 2 GeV vertical bunch-by-bunch beam size for 1x45 pattern, positrons April 22, 2019 CesrTA Seminar

Theory and measurement of instability onset Qualitative comparison: if the transverse eigen-frequency of the electron cloud becomes comparable with the corresponding betatron frequency (xc), then the transverse motion becomes unstable. Need to take into account the horizontal motion as well. 0.35 mA See ILCDR06 Talk by L. Schachter – https://wiki.lepp.cornell.edu/ilc/pub/Public/DampingRings/CornellWorkshopTalks/Schachter.Wake-Field_in_eCloud.ppt April 22, 2019 CesrTA Seminar

Witness Bunch Studies – e+ Vertical Tune Shift Initial train of 10 bunches a generate EC Measure tune shift and beamsize for witness bunches at various spacings Positron Beam, 0.75 mA/bunch, 14 ns spacing, 1.9 GeV Operation Error bars represent scatter observed during a sequence of measurements 1 kHz a Dn=0.0026 re ~ 1.5 x 1011 m-3 Ohmi, etal, APAC01, p.445 Preliminary Results April 22, 2019 CesrTA Seminar

Witness Bunch Studies – e- Vertical Tune Shift Same setup as for positrons Negative vertical tune shift and long decay consistent with EC Electron Beam, 0.75 mA/bunch, 14 ns spacing, 1.9 GeV Operation Negative vertical tune shift along train a consistent with EC Magnitude of shift along train is ~1/4th of shift for positron beam NOTE: Shift continues to grow for 1st 4 witness bunches! Preliminary Results April 22, 2019 CesrTA Seminar

Witness Bunch Studies – Comparison of e-/e+ Tunes Magnitude of tune shift for electron beam is ~1/4th of shift observed for positron beam April 22, 2019 CesrTA Seminar

Fast Ion Instability? Qh Qv 0.5 kHz full scale - 45 bunch train - Electrons - 14ns spacing - 1.2e10/bunch Qh 0.6 kHz full scale Instability? Linear theory predicts 100 turn growth rate for 45th bunch Vertical beam size Qv 0.5 kHz full scale Measurements underway to characterize mode spectra April 22, 2019 CesrTA Seminar

ILC EDR needs drive research program until early 2010 CesrTA Schedule Initial Focus Electron cloud growth and suppression in wigglers Improvements for low emittance operations through 2009 ILC EDR needs drive research program until early 2010 Expect re-evaluation of program at that point Potential for prototype testing after the EDR period At NSF request, we have resubmitted (3 weeks ago) the CesrTA proposal jointly to DOE and NSF April 22, 2019 CesrTA Seminar

Now Until April 1, 2008 RFA Assembly Implement 4ns transverse feedback (transverse now operating) R. Meller, M. Billing, G. Codner, J. Sikora Install North IR Retarding Field Analyzers (RFA) for electron cloud measurements during May down Preparatory machine studies program Continue electron cloud and ion studies Start exploration of low emittance operations CESR-c (existing machine layout) optics have been designed: ex ~ 6.5 nm Early work on beam-based alignment Prepare for wiggler vacuum chamber studies Collaboration: SLAC, LBNL Design and construction of new vacuum chambers is a critical path item Segmented RFA for high field operation General infrastructure preparation Feedback Cryogenics Vacuum Other… RFA Assembly April 22, 2019 CesrTA Seminar

International Linear Collider Overview Preparing for the Engineering Design Report (EDR) ILC R&D at Cornell ILC Damping Rings R&D in Detail CesrTA Proposal Overall Scope Damping Rings R&D Using CESR Concept and Goals Ring Modifications Parameters and Experimental Reach Schedule Collaborators and Projects Synergies with Other Parts of the CLASSE Program Conclusion and Acknowledgments April 22, 2019 CesrTA Seminar

Modifications that will benefit ERL@CESR Synergies Modifications that will benefit ERL@CESR BPM system upgrade provides electronics that will be reused for the ERL Improvements in low emittance diagnostics Improvements in survey and alignment capabilities Development of machine correction methods at ultra low emittance Potential new regimes for CHESS operations 5 GeV low emittance lattice 6 wiggler operation with ex ~ 26 nm Requires a ~100kW x-ray dump Goal is 100 mA single beam operations April 22, 2019 CesrTA Seminar

Unique Features of R&D at CESR CESR offers: The only operating wiggler-dominated storage ring in the world The CESR-c damping wigglers Technology choice for the ILC DR baseline design Physical aperture: Acceptance for the injected positron beam Field quality: Critical for providing sufficient dynamic aperture in the damping rings Flexible operation with positrons and electrons Flexible bunch spacings suitable for damping ring tests Presently operate with 14 ns spacing Can operate down to 4ns (or 2ns) spacings with suitable feedback system upgrades Flexible energy range from 1.5 to 5.5 GeV CESR-c wigglers and vacuum chamber specified for 1.5-2.5 GeV operation An ILC DR prototype wiggler and vacuum chamber could be run at 5 GeV Dedicated focus on damping ring R&D for significant running periods after the end of CLEO-c data-taking A useful set of damping ring research opportunities… The ability to operate with positrons and with the CESR-c damping wigglers offers a unique experimental reach April 22, 2019 CesrTA Seminar

CesrTA conceptual design work is ongoing Conclusion CesrTA conceptual design work is ongoing Program offers unique features for critical ILC damping ring R&D Simulations indicate that the emittance reach is suitable for a range of damping ring beam dynamics studies The experimental schedule will allow timely results for ILC damping ring R&D! April 22, 2019 CesrTA Seminar

CesrTA Studies and CESR Machine Studies Acknowledgments CesrTA Studies and CESR Machine Studies J. Alexander M. Billing G. Codner J. Crittenden M. Ehrlichman (Minn) M. Forster D. Hartill R. Helms D. Rice D. Rubin D. Sagan L. Schachter J. Shanks (REU) E. Tanke M. Tigner J. Urban April 22, 2019 CesrTA Seminar