Some Considerations on CLIC Integrated Tests D. Schulte, A. Grudiev, E. Jensen, A. Latina, Y. Papaphilippou, Ph. Lebrun, H. Schmickler, S. Stapnes, I. Syratchev, R. Tomas, W. Wuensch D. Schulte CLIC Layout Drive Beam Generation Complex Main Beam Generation Complex D. Schulte Future of Luminosity Studies Moving from There is a solution to This is the most cost effective solution with reasonable risk We need to define margins more precisely, which has a strong cost impact compare different implementations of components for risk make sure that all operational constraints are respected Make sure that we did not forget something This requires more precise quantitative predictions, more detailed modelling, understanding of operational constraints More experimental verification of predictions An experimental programme is essential for this stage On the component and imperfections model level Integrated beam tests address the operational issues They confirm that we did not miss some important effect Are an essential and time consuming step to turn a theoretical solution into something practical D. Schulte D. Schulte Damping ring design is consistent with target performance Light sources have comparable performances Many design issues lattice design dynamic aperture tolerances intra-beam scattering space charge wigglers RF system vacuum electron cloud kickers Damping Ring Consideration Should verify emittances with more similar beam conditions But not all parameters are similar Damping Ring Experiments Currently addressed at existing rings Small zero current emittance Has been shown in vertical plane, reasonably close in horizontal Collective effects Intra-beam scattering Experiment at SLS, but difficult to separate from other collective effects Electron cloud Small secondary emission yield seems universally required and achievable (1.3) But small photo-emission yield is not obvious (0.001 e/) Wigglers Test planned at ANKA Extraction kickers Tests planned in ALBA and maybe ATF RF system Tests to be determined Tests at/improvements of existing rings should be increased D. Schulte Beam Delivery System Consideration D. Schulte6 Main design issues chromaticity non-linear effects synchrotron radiation tuning stability Probability to achieve more than L/L 0 [%] Need to verify the beam performance in real system ATF2 is a good model But design is complex Convergence of tuning is slow in simulations O(10 4 ) iterations Very sensitive to dynamic effects Requires very advanced instrumentation and component design Design is OK (based on Pantaleos scheme) Imperfection mitigation comes close to target (L 110% L 0, probability 90%) Simulated full tuning performance Goal BDS Experiments Current programme is focused on ATF2 Past experiment at FFTB Tuning of ATF2 is big step toward tuning of CLIC BDS Many instruments and components are being developed for ATF2 Ground motion experiment is foreseen Compare ground motion sensors and beam measurements Compromised by low repetition rate and different ground motion spectrum Main issues The availability of ATF2/ATF3 And a potential change of our system design May obtain O(40nm) beamsize (O(25nm) with upgrade), CLIC has 2.3nm at 500GeV and 1nm at 3TeV No active stabilisation against ground motion in ATF2; but this is mandatory for CLIC, so we would like to test it Would like better test facility D. Schulte D. Schulte8 Main Linac Considerations Main design issues Wakefields BPM alignment wake monitors structure tilt BPM resolution quadrupole roll quadrupole stability vacuum Emittiance growth at 500GeV after DFS Design is OK Imperfection mitigation achieves target DFS has not been tested many effects were discovered during the studies, so maybe we miss one emittances are unprecedented in linacs (10nm vs. >1m) Main Linac Exeriments Two beam test stand in CTF3 A single structure but gives important information Three modules are in preparation for beam tests Will allow to test modules better But need to define additional tests, e.g. BPM accuracy, wakemonitor accuracy, Currently have experiment at FACET Others can be envisaged But far from our target emittance and hardware configuration Will have about 100m of linac at CLIC0 But will only come at the end of CLIC0 Need something else 4 th generation light sources (e.g. Swiss FEL) Something purpose built D. Schulte Experiment Considerations Would like to test a significant length of main linac Would like 108 modules i.e. 108 quadrupoles, ~11 betatron wavelengths, ~220m 3 DFS correction bins i.e. long enough for ballistic alignment tests Some distance for wakefield bump Expect O(11%/6%) of full CLIC wakefield emittance growth (at 500GeV/3TeV) Small emittance beam for steering tests Maybe can live with somewhat less Would like an integrated test of low emittance generation and preservation System chain is important, e.g. use bunch compressor for main linac alignment, main linac RF jitter is important for BDS, D. Schulte Ultimate CLIC Test Facility Drive Beam Generation Complex Main Beam Generation Complex D. Schulte Dream Test Facility Scheme Low emittance ring, e.g. CLIC damping ring, 3 rd generation light source, damping ring test facility Main linac with bunch compressor Powered with drive beam or X-band klystrons BDS test facility Injector Example options: SPS as damping ring (combined with CLIC0?), FACET with improved damping ring? ATF, PEP-II, ESRF, SLS, SPRING-8, Note: FFTB has been similar But with y = O(1m) Reached y =70nm (design 50nm) D. Schulte Required Linac Beam Parameters O(10nm) vertical emittance to test preservation Would need um cavity scatter -> 0.14nm 14um BPM scatter -> 14nm D. Schulte Example Test Linac Parameters (cont.) Beam parameters at entrance depend on ring Could use another structure and adjust beam parameters Could reduce cost by Compromise on length Use of other structures, with smaller power needs Use of unpowered structures Synergy with a user facility The linac can be the heart of an FEL D. Schulte User Facility Operation Bypassing the damping ring or with dedicated injector, one can use the linac as an FEL Maybe some benefit in using ring and linac together as light source or for other experiments, e.g. ATF3 programme Can we think of more? The ring can still be used almost independently, e.g. as a light source D. Schulte Example: ESRF ParameterValueComment Energy6 GeVSomewhat high, maybe can operate at lower energy Ne0.8-14nCVery good zz 6mmA bit long, hard to compress at 6GeV xx 50mSomewhat high, but still fits in aperture, plans to reduce it? yy 40nmA bit high, limited by instrumentation? GHz/f b Does not quite match Space avail.?To be discussed Need to explore potential improvements of parameters Operation at lower energy? Lattice improvements? Shorter bunches D. Schulte Required Photon Energies Seem to profit from below 1 a only for very short pulses Typically 8keV (0.15nm) are needed for atoms TESLA design report states 100keV as interesting for material science, but SUR is used profit from high energy and current Do we miss something interesting? NLS report D. Schulte Required Beam Energy Coherent wavelength is given by Typical best values are (e.g. Swiss FEL) Consequently for =0.1nm => Gradient for CLIC test facility is about 40MV/m for 150m active length D. Schulte Feasibility Proposal of Ch. Adolphsen et al. shows concept for X-band Swiss FEL: E=5.8GeV Q=200pC z =7m 200nm-500nm Main parameters: E=6GeV Q=250pC z =8m 400nm-500nm D. Schulte High Frequency Advantages For the same structure design and gradient one can reduce total peak klystron power with sqrt(1/f) and average power with 1/f 2 Potentially some cost saving Or one can increase gradient with sqrt(f) for the same total peak klystron power and reduced average power (scales as 1/f 3/2 ) Can decrease cost More compact design But space savings only important at high energies Can we improve the structure design? To give us more advantage than above scaling Should make a clear case for high frequency Provided we can Not focused on our specific design D. Schulte High Frequency Issues Component practicality This is what we want to address, common for light source and CLIC (not fully for klystrons) Higher wakefields Transverse effects grow with f 4 This forces to use tighter focusing Which requires better alignment And maybe stabilisation for test facility E.g. simply scaled Swiss FEL linac 2 cannot work for us Need further increased focusing Increased apertures Shorter bunches D. Schulte Structure Choice 1>>A= Stability requires Linac 2 of SLAC proposal is most difficult Calculate required a, using CLIC lattice D. Schulte SLAC Structure Parameters Optimum cost at 70MV/m and 55MV/m Would profit from our focusing lattice but shorter than what we want 82m instead of 150m D. Schulte Power System 1 SLAC proposal would need klystrons D. Schulte Power System 2 Igors proposal uses 5.5MW klystrons Can run at 1kHz How profitable is this? D. Schulte Bunch Compressor and BDS Bunch compressor conceptual design is on the way (A. Latina) Almost factor 30 reached in ILC (6mm->220m) But system is 300m long (at 5GeV) BDS can achieve y 10m (R. Tomas) Corresponds to y 3nm Estimated BDS and diagnostics line length is 130m 130m BDS Plus 100m for diagnostics Total close to Swiss FEL photon and experimental line length D. Schulte Things to Test Accelerating structure performance Single bunch wakefields, breakdowns, conditioning, operation, fabrication, dark current, environment for instrumentation, vacuum?, low-level control, Beam dynamics and operation Operation constraints, dispersion free steering, integrated studies, instrumentation performance, overlooked effects, benchmarking, Functioning of instrumentation Alignment, wake monitors, BPMs, tiny beam sizes Have to check the need of stabilisation Multi-bunch stability will be difficult to test Not required for FEL Or maybe there is a case? Can we use the FEL injector or the damping ring? Frequency matching (e.g. ESRF 350MHz) D. Schulte Conclusion An integrated test facility could strongly improve understanding emittance preservation Excellent test facility for main linac The combination of ring, bunch compressor, linac and BDS is very valuable E.g. allows very small beam sizes We can profit from very strong synergy with user facilities X-band seems a very good technology for FEL Could we make an even better case? We would foster wide use of X-band technology D. Schulte Reserve D. Schulte What do we learn about rf from the facility 1? Scientific and technical results Statistical and long-term behaviour of X-band accelerating structures. What is the performance variation among structures? Do the structures continue to improve in breakdown rate? Opportunity to compare various conditioning strategies. We generate lots of opinions, here there will be enough structures to actually test some of them in a statistically meaningful way. The statistics need to be shared with arguments which follow! Opportunity to compare fabrication technologies - various surface preparation techniques for example. We can predict the effect for the highest gradients even if we are not running at them through BDR slopes. Excellent test of the simulations we have done. For example are our do real and simulated structure wakefields match? Are we accounting for multi-polar components in the fundamental correctly? What is the operational environment for other beam systems such as instrumentation? Measure dark current and radiation backgrounds. New opportunity to measure dynamic vacuum? D. Schulte What do we learn about rf from the facility 2? Scientific and technical results (cont.) Refined design of rf components for cost performance and lifetime Refine operational strategies. What are the statistics of breakdown and how do we recover from them? Develop low-level rf systems breakdown detection, wakefield monitor and phase control electronics. Commercial and cost We will have create suppliers for X-band hardware of all types. Will be needed them later on. Create integrate suppliers capable of delivering to high-power rf specifications rather than just mechanical ones. Improve knowledge of cost. Knock-on effect Successful operation of the linac will make the X-band and high-gradient much more attractive and defendable for other projects. Increases community for high-gradient and high-frequency technology. D. Schulte Beam Dynamics Single bunch beam stability with jitter BPM alignment and one-to-one steering Dispersion free steering Need to artificially make BPM alignment worse Functioning of instrumentation Alignment, wake monitors, BPMs, tiny beam sizes Have to check the need of stabilisation Multi-bunch stability will be difficult to test Not required for FEL Or maybe there is a case? Can we use the FEL injector or the damping ring? D. Schulte Basic Parameters D. Schulte