clic and other options for multi-tev lepton physics

CLIC and Other Optionsfor Multi-TeV Lepton PhysicsTor RaubenheimerAccelerator Research Division Head, SLAC

P5 MeetingFermilabFebruary 1st, 2008

February 1st, 2008 Page * Tor Raubenheimer

IntroductionOutlineCLIC concept (X-band Two-Beam Accelerator)Technology statusOutstanding issuesLC roadmap and other optionsAssumptionsBelieve that the motivation for TeV-scale LC remains the same but timescale is slower, motivating a broad look at LC technologyCaveatsEvaluation of outstanding issues for CLIC design is my opinionSuggestions for other options is also my opinionThese views are not endorsed by SLAC, the GDE, or I (and SLAC) are committed to developing the ILC as the near-term solution for a 500 GeV LC


What is CLIC?CLIC = Compact LInear ColliderDeveloped by CERN originally as a 30 GHz and 150 MV/m that is based on a two-beam accelerator conceptTwo-beam concept is an efficient way to transform rf frequency from long-pulse low-frequency short-pulse high-frequency and thereby drive high gradientsConcept is elegant but still waiting for demonstrations and detailed costs illustrating the benefits Developed parameters from 500 GeV 3TeVRecently changed parameters to 12 GHz and 100 MV/m to reduce cost and better utilize GLC/NLC R&DDevelopment program to demonstrate ~100 MV/m by 2010CTF3 test facility should demonstrate TBA concept on a similar timescale


Two-Beam Accelerator Concept(from R. Corsini; 2006 parameters)


CLIC RF Module ~ 2 metersMain Beam ~1 ADrive Beam 100 AAccelerating structure, +100 MV/m, 64 MW, 229 mm Power Extraction Structures:-6.5 MV/m, 136 MW, 210 mmrf distribution


CLIC Schematic (2007 Parameters for 3 TeV)Injector systems similar to other LC conceptsDrive beam complex efficiently generates high power beamMain linacs have deccelerator struct-ures adjacent to accelerator structures in single tunnel all LLRF and complicated electronics are elsewhereSimilar number of klystrons as 500 GeV ILC


CLIC Linear Collider Parameters


Possible CLIC Siting OptionIP under CERN Prevessin sitePhase 1: 1 TEV extension 19.5 kmPhase 2: 3 TeV extension 48.5 kmDetectors and Interaction PointCERN sitePrevessin


Proposed Timescale(from JPD presentation to CERN SPC)


Cost for TBA versus Conventional LCMajor study needed as part of CLIC CDR but characteristics can be understood. The TBA has a large central infrastructure that generates drive beam Cost per GeV of TBA is likely cheaper than that of a conventional klystron-based linear colliderInitial cost of the TBA is higher than that of a klystron-based collider

Location of cross-over and slopes is unknown for present technologiesFrom 1998 comparison of 1996 NLC versus X-band TBA costs by G. LoewCms GeV

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GLC/NLC >50 MV/m OperationUnloaded Gradient (MV/m)Breakdown Rate at 60 Hz (#/hr)with 400 ns PulsesNLC/GLC Rate LimitEight Structure Average Single Structures Breakdown performance continued to improve with time BDR ~ exp(- t / 400 hrs) over the 2000 hrs operation


100 MV/m Structure testing at NLCTA(Structures from GLC/NLC program in early 2000s)Run slotted, a/l = 0.18, 75 cm NLC structure (H75vg4S18) with 150 ns pulses - at 102 MV/m, breakdown rate = 6 10-6Run early NLC, non-slotted, 53 cm, smaller aperture (a/l = 0.13) structure (T53vg3MC) at short pulses unloaded gradient at a 10-6 breakdown rate with 100 ns pulses is 105 MV/m and more recently it achieved similar gradient with 200ns ramped pulse.Building CERN-designed structures for future tests at SLAC and KEK


Single Cell Accelerator Structure Testing(Understand Fundamental Breakdown Limits) Goals Study rf breakdown in practical accelerating structures: dependence on circuit parameters, materials, cell shapes and surface processing techniquesDifficultiesFull scale structures are complex and expensiveSolutionSingle cell Traveling wave (TW) and single cell standing wave (SW) structures with properties close to that of full scale structures This program, now, has a strong participation from both KEK and CERN.Time of flat pulse after filling timeVariety of Single Cell Accelerator Structures Manufactured at KEKSW accelerator structure test with a/l~0.21. In this type of structures loaded and unloaded gradients are the same


CTF3 CLIC Test FacilityLarge-scale LC test facility to demonstrate TBA conceptDLCLEX 2007-2009building in 2006/720042005Thermionic gunCRTL2 2007-200830 GHz production(PETS line)and test standPhoto injector / lasertests from 2008LinacBeam up to here2007Major milestones in 2007:Combiner Ring (CR) installedCLEX building finished, equipment installation started150 MeV 30 A - 140 ns


RF Unit Demonstrations(What is necessary before construction?)The RF Unit is the acceleration element that is replicated through the main linacsUsually thought of as the minimal element that needs demonstration before construction -- CLIC is different

In GLC/NLC: two 75-MW klystrons, SLED-II rf pulse compression system and 4.8 meters of accelerator structure operating at 50 MV/m loaded ~250 MeV per rf unitPieces demonstrated in 2004; System demo canceledIn ILC: a modulator and klystron, an rf distribution system, and 3 cryomodules with 26 1-meter rf cavities operating at 31.5 MV/m ~1 GeV per rf unitPieces to be demonstrated in 2010; System demo in ~2012In CLIC: a 2.5 GeV 100 Amp drive beam is fed into ~600 meters of decellerator structures that accelerate the primary by ~60 GeVPieces demonstrated in ~2012 in CTF3 but no RF Unit demo


Outstanding Issues for CLICProgram to develop high-gradient accelerator structures by 2010May not achieve 100 MV/m at desired breakdown rate but, given present results, will probably be closeSystematic cost estimate needed Working with GDE to develop costs using same methodology as applied to ILC aiming for 2010-timescaleTighter alignment and jitter tolerancesAiming to demonstrate stabilization techniques by 2010Program to demonstrated TBA-concept in CTF3 by 2012 and accelerate beams to ~1 GeVConcept demonstrated but drive beam parameters quite different from CLIC and will not demonstrate an RF UnitNot clear what is necessary to launch construction and the collaboration is discussing options


Understanding the Gradient ChoiceCost optimum is a balance between costs proportional to length, i.e. tunnel & structures and costs proportional to the rf power sources G = A sqrt(P * Rs) P = rf power / meter Rs = shunt imp. / m

Have to reduce rf power cost per MW by 2x or double shunt imped. to increase G by 40%

Unloaded Gradient (MV/m)Relative TPCAt low gradient, cost increases due to larger length costsAt high gradient, cost increases due to higher rf power costsGLC/NLC X-band


CLIC Gradient OptimizationCERN developed a detailed cost estimate using the TESLA estimate and the US Technical Options Study (2003) costingNot entirely clear what is included and what drives the frequency scaling but the basic form makes senseBelieve that there is an assumption that above 10 GHz, the gradient is independent of frequencyMain point: very high gradients dont make cost sense

PreviousNewOptimumCost


Approaches to a Linear Collider(Four Options)Superconducting rf (1.3 GHz)Strong international support through ILC collaborationGradients of 30 MV/m in cavities yielding 20 MV/m averageTechnology well advanced (1 GeV test facilities under construction at Fermilab and KEK 2011 or 2012)Can be stretched to ~1 TeV energy Normal conducting rf (11 ~ 12 GHz)Strong international support through CLIC collaborationCLIC recently adopted 12 GHz down from 30 GHzGradients of 100 MV/m yielding 80 MV/m averageTechnology fairly well advanced (test facility at SLAC demonstrated 300 MeV at 50 MV/m in 2004 and CTF3 at CERN aiming for 1 GeV at 100 MV/m in 2012 - 2014)Certainly reach 1 TeV and maybe multi-TeV energies


Approaches to a Linear Collider (2)(Four Options)Normal Conducting rf (cont.)Two NC rf source concepts have been considered:Klystron-based linacs with klystrons along accelerator Two-Beam accelerator with drive beam powering linacPossible to consider a staged implementation using first klystron-based and then TBA-based rf power to reduce riskAdvanced concepts (laser and plasma)Small lab and university-based collaborationsGradients of many GeV per meter have been demonstratedTechnology has many challenges working to develop roadmap illustrating development of acceleration concept and beam quality conceptsSome concepts (PWFA) use conventional rf linacs as drivers or injectors


A Roadmap for Multi-TeV Lepton Colliders500 GeV LCNeutrino sourceNeutrino ringMuon collider (few TeV)350 GeV LCMulti-TeV LC20102020204020502030Timescale (personal guess)Plasma AccSuperconducting RFNormal conducting - Two-Beam-basedNormal conducting Klystron-basedMulti-TeV LC4th GenerationSR Sources5th Generation SR Sources?The LC roadmap illustrates options and connections between them. Selecting a path requires additional information such as LHC results and technology status


One Possible Path to Multi-TeV Lepton Physics500 GeV LCNeutrino sourceNeutrino ringMuon collider (few TeV)350 GeV LCMulti-TeV LC20102020204020502030Timescale (personal guess)Plasma AccSuperconducting RFNormal conducting - Two-Beam-basedNormal conducting Klystron-basedMulti-TeV LC4th GenerationSR Sources5th Generation SR Sources?


RF Power Source R&DDeveloping rf power sources for ILC:Marx solid state modulator broad applicability of technologySheet beam klystron broad applicability of SBK conceptDeveloped rf power source for GLC/NLC:SLED-II system delivered >500 MWTwo-Pac modulator fabricated but never tested halted in 2004X-band klystrons operated at 75 MW and 1.5 us but limited by breakdowns Consider new output structures or reduced power levels using knowledge from high gradient studiesFuture program to complete X-band rf source programCould provide a more conservative option to CLIC designPower sources for compact radiation sources and other compact installations


GLC/NLC RF Power SourcesGood success with modulator, pulse compression and rf distribution development. Klystrons achieved peak power and pulse length specs but BDR was too highCombined Klystron PowerOutput Power(Gain = 3.1, Goal = 3.25)


Staged Approach to TBAShould re-optimize the NC rf source but as a start:Use the (nearly developed) GLC/NLC power source to power the CLIC accelerator structures at a loaded gradient of ~60 MV/mNeed to solve klystron BDR problem but assuming successIncrease gradient by ~20% for same cost per meterEasy to perform systems demonstration of an rf unitSimple improvements in pulse compression could increase power per meter 10% cost reductionBuild lowest reasonable energy LC with klystronsCommission X-band main linac, BDS, sources and detectorsUse infrastructure to start testing TBA drive beam dynamics while operating klystron-based collider and then move to TBA.


Another Possible Path to Multi-TeV Lepton Physics500 GeV LCNeutrino sourceNeutrino ringMuon collider (few TeV)350 GeV LCMulti-TeV LC20102020204020502030Timescale (personal guess)Plasma AccSuperconducting RFNormal conducting - Two-Beam-basedNormal conducting Klystron-basedMulti-TeV LC4th GenerationSR Sources5th Generation SR Sources?


Comment on Spin-off ApplicationsCompact high gain FELsStorage ring injectorsMedical linacsIndustrial radiation sourcesHigh gain FELsRecirculating linacs and CW applicationsIndustrial accelerators (no present applications)Both NC and SC rf technology have many additional applicationsNormal conducting RFSuperconducting RF To date, NC technology has been simpler and cheaper to implement (at least for small-scale applications) SC technology is better suited for CW applications and NC is better suited to short high-current beam pulses Both technologies can have comparable efficiencies and deliver comparable beam power


Applications Example: High Gain FELsRoughly equal number of normal conducting and superconductingbased FEL sources

Many FELs use higher harmonics for bunch compressions; SLAC was asked to build 12 GHz klystrons for Trieste, Frascati and PSI


Yet Another Possible Path to Multi-TeV Lepton Physics500 GeV LCNeutrino sourceNeutrino ringMuon collider (few TeV)350 GeV LCMulti-TeV LC20102020204020502030Timescale (personal guess)Plasma AccSuperconducting RFNormal conducting - Two-Beam-basedNormal conducting Klystron-basedMulti-TeV LC4th GenerationSR Sources5th Generation SR Sources?PWFA accelerator could likely work with either SC or NC driver linacs SC option illustrated here.


Example: Plasma Wakefield Acceleration (PWFA)Acceleration gradients of ~50 GV/m (3000 x SLAC)Doubled energy of 45 GeV beam in 1 meter plasmaMajor questions remainBeam accelerationEmittance preservationNew facilities being developed


Future PWFA OpportunitiesA TeV Plasma Wakefield Accelerator based Linear Collider or optimized design using low energy bunch train to accelerate single high energy bunchSingle stage afterburnerOther applications:Apply MT/m focusing gradients in plasma ion column to radiation production (Ion Channel Laser)New phenomena (trapped electrons) may offer high brightness sources


X-band R&D Funding RequirementsX-band R&D was cut from ~20M$ / year to ~3M$ per year after 2004 ITRP decision3M$ / year funds US High Gradient Collaboration pursuing fundamental R&D on structure gradient limitationsUS and KEK are working with CERN testing high-gradient structure prototypes. Need additional funds to support this.Also urge funding for X-band power source R&D in USComplete GLC/NLC rf power source development to facilitate a staged approach to CLIC while pursuing fundamental R&D on alternate rf power sourcesInfrastructure is already in place relatively inexpensive to use; however it will be difficult to maintain capability without a programComplete R&D program would ramp to ~10 M$ / yearRoughly 20% of projected FY10 US SCRF and ILC programs


SummaryCritical time for linear collider R&D programScience case for a TeV-scale collider remains strongNeed to consider what we as a community need to do to maintain options for energy frontier lepton probesOptions exist with different reaches, timescales, risks and costsILC is the most developed but X-band options also existDont really know the costs and risks of the different pathsShould have much more information in 2010 ~ 2012

Develop multiple linear collider technologies: need R&D on SC, NC and advanced acceleration concepts Great potential & many applications of the technology across scienceStrong collaborations with ILC GDE as well as CERN and KEKExtensive infrastructure exists to support X-band and plasma R&D

clic and other options for multi-tev lepton physics

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