A Plasma Wakefield Accelerator-Based Linear Collider Vision for Plasma Wakefield R&D at FACET and Beyond e-e+Colliding Plasma Wakes Simulation, F. Tsung Beyond 10 GeV: Results, Plans and Critical Issues T. Katsouleas University of Southern California Doe FACET Review February 19, 2008 Outline • • • • • Brief History and Context Introduction to plasma wakefield accelerators Path to a high energy collider Critical issues, milestones and timeframe What can and cannot be addressed with FACET Plasma Accelerators -- Brief History • • • • • • • 1979 Tajima & Dawson Paper 1983 Tigner Panel rec’d investment in adv. acc. 1985 Malibu, GV/m unloaded beat wave fields, world-wide effort begins 1989 1st e- at UCLA 1994 ‘Jet age’ begins (100 MeV in laser-driven gas jet at RAL) 2004 ‘Dawn of Compact Accelerators’ (monoenergetic beams at LBL, LOA, RAL) 2007 Energy Doubling at SLAC ILC Current Energy Frontier E164X/E-167 LBL RAL LBL Osaka UCLA ANL Research program has put Beam Physics at the Forefront of Science Acceleration, Radiation Sources, Refraction, Medical Applications Charge Context Ι mechanism to elevate some new acceleration technologies to the next level of demonstrated performance.Σ #3. Evaluate the effectiveness of the anticipated ASF R&D program to confront the critical technical issues for very compact, multi-TeV plasma accelerators. 1. 2. Evaluate the effectivenes s of the anticipated ASF R&D progr am to conf ront the criti cal techni cal is sue s for very comp act, multi- TeV plasma accelerators. #4. Advise the HEP program on the anticipated scientific Advise the HEP program on the anticipated scientifi c im pact of FACET, whether impact of isFACET, theofimpact commensurate the impact comm ensurawhether te wit h the scale resourcesis required for cons truction 1.with Evaluate the effectivenes s of the anticipated ASF R&D progr am to conf the and the operation; theof un iquenes s of the facilit y; and the exist ence of simil ar ront scale resources required for construction and criti cales techni cal isre.sue s for very comp act, multi- TeV plasma accelerators. capabiliti els ewhe operation; the uniqueness of the facility; and the existence Advise the HEP capabilities program on the anticipated scientifi c im pact of FACET, whether the of similar elsewhere. im pact is comme nsu rate with the scale of resources requir ed for construction and operation; the uniquene ss of t he facilit y; and the existenc e of simil ar capabiliti es els ewhe re. Particle Accelerators Requirements for High Energy Physics • High Energy • High Luminosity (event rate) • • High Beam Quality • • • L=fN2/4psxsy Energy spread dg/g ~ .1 - 10% Low emittance: en ~ gsyqy << 1 mm-mrad Low Cost (one-tenth of $10B/TeV) • • Gradients > 100 MeV/m Efficiency > few % Simple Wave Amplitude Estimate E Vph=c 1-D plasma density wave E ~ ik p E 4 pen1 k p p Vph p c n1 ~ n o eE ~ 4 pen oe 2c p mc p or eE ~ no 10GeV m 16 3 10 cm Gauss’ Law Linear Plasma Wakefield Theory (t2 2p ) n1 n 2p b no no Large wake for a laser amplitude a beam density nb~ no For sz of order cpp-1 ~ 30m (1017/no)1/2 and spot size s=c/p ~ 15m (1017/no)1/2 : Q/ sz = 1nCoul/30m (I~10 kA) Requirements on I, t, s, g require a FACET-class facility Ultra-high gradient regime and long propagation issues not possible to access with a 50 MeV beam facility Nonlinear Wakefield Accelerators (Blowout Regime) Rosenzweig et al. 1990 -- -- -- ----- ---------++- ++ ++ ++ ---++-- -+-+------++ ++ ++ ++ ++ --+-+- +--+----+-+- ++ + +--+ ++ + ++ + +++ ++++ -+++-+------++- ++++ ++++ ++++ ++ ++--++--++++ ++++ ++++ ++ ---- ------- --- -- -- - - - -- -- - ---- -- - - - - -- --Ez • Plasma ion channel exerts restoring force => space charge oscillations •Linear focusing force on beams (F/r=2pne2/m) •Synchrotron radiation •Scattering Limits to Energy Gain E- •Beam propagation • Head erosion (L=ps2/e) • Hosing load driver E+ • Transformer Ratio: R g load g driver E L E E L E PIC Simulations of beam loading Blowout regime Beam load flattens wake, reduces energy spread Ez Unloaded wake Loaded wake •Nload~30% Nmax •1% energy spread U C L A Emittance Preservation • Emittance en = phase space area: px s x Plasma focusing causes beam to rotate in phase space 1/4 betatron period (tails from nonlinear Fp ) Several betatron periods (effective area increased) • Matching: Plasma focusing (~2pnoe2s) = Thermal pressure (grad p~e2/s3) s en 2 2 c g p • No spot size oscillations (phase space rotations) • No emittance growth Fp Fth Positron Acceleration -- two possibilities blowout or suck-in wakes e+ ee+ load • Non-uniform focusing force (r,z) • Smaller accelerating force • Much smaller acceptance phase for acceleration and focusing Ref. S. Lee et al., Phys. Rev. E (2000); M. Zhou, PhD Thesis (2008) Accelerator Comparison •On ultra-fast timescales, relativistic plasmas can be robust, stable and disposable accelerating structures •No aperture, BBU TESLA structure l ~ 30cm Plasma l ~ 100mm 2a Path to a TeV Collider from present state-of-the-art* • Starting point: 42 --> 85 GeV in 1m – Few % of particles • Beam load – 25-50 GeV in ~ 1m – 2nd bunch with 33% of particles – Small energy spread • Replicate for positrons • Marry to high efficiency driver • Stage 20 times * I. Blumenfeld et al., Nature 445, 741 (2007) CLIC-like PWFA LC Schematic ~120 MW AC power per side 12 usec trains of e- bunches accelerated to ~25 GeV Bunch population ~3 x 1010, 2 nsec spacing 100 trains / second Drive Beam Accelerator ~2 km ~60 MW drive beam power per side ~20 MW main beam power per side PWFA Cells: DR 25 GeV in ~ 1 m, 20 per side Beam Delivery System, ~100 m spacing IR, and Main Beam Extraction / Dump Main Beam e- Source: ~ 4 km 500 nsec trains of e- bunches Bunch population ~1 x spacing 100 trains / second 1010, 2 nsec 1TeV CM DR Main Beam e+ Source: 500 nsec trains of e- bunches Bunch population ~1 x 1010, 2 nsec spacin 100 trains / second Drive Beam Source • DC or RF gun mini-train 20 mini-train 1 • Train format: • With 3 x 1010 /bunch @ 100Hz: • ~2.3 mA average current, ~2 A beam current, similar to beam successfully accelerated in CTF3 500ns: 250bunches 2ns spacing 100ns kicker gap 12ms train •Compress bunches to ~30 m RMS length • SPPS achieved much smaller RMS lengths • Accelerate to 25 GeV • Fully-loaded NC RF structures, similar to CLIC / CTF 3 • Inject into “Drive Beam Superhighway” with pulsed extraction for each PWFA cell • Both e+ and e- main beams use e- drive beam See slide notes for additional background Drive Beam Superhighway • Based on CLIC drive beam scheme – Drive beam propagates opposite direction wrt main beam – Drive mini-train spacing = 2 * PWFA cell spacing i.e, ~600 nsec Drive Beam Distribution • Format options – Mini-trains < 600 nsec • NC RF for drive beam • Duty cycle very low – Individual bunches > 12 μsec • SC RF for drive beam • Duty cycle ~100 % Main Beam Source and Plasma Sections • Electron side: •DC gun + DR •Compress to 10m (achieved in SPPS) •20, +25GeV plasma sections, each 1E17 density, <1.2 meters long • Gaussian beams assumed -shaped beam profiles => larger transformer ratio, higher efficiency • Final main beam energy spread <5% • Positron side: • conventional target + DR • Positron acceleration in electron beam driven wakes (regular plasma or hollow channel) • Will have tighter tolerances than electron side Matching / Combining / Separating Main and Drive Beams • • • Must preserve bunch lengths Preserve emittance of main beam ~100 μm spacing of main and drive bunches – Time too short for a kicker – need magnetostatic combiner / separator – Need main – drive bunch timing at μm level • Different challenges at different energies – High main beam energy: emittance growth from SR – Low main beam energy: separation tricky because of ~equal beam energies • Need ~100 m between PWFA cells “First attempt” optics of 500 GeV / beam separator. First bend and first quad separate drive and main beam in x (they have different energies); combiner is same idea in reverse. This optics needs some tuning and ~2 sextupoles. System is isochronous to the level of ~1 μm R56. Assuming that another ~50 m needed for combiner, each PWFA cell needs ~100 m of optics around it. TeV Beam Parameter Summary E CM at IP [GeV] N, drive bunch N, high energy bunch n h.e. bunch/sec [Hz] Main beam train length [nsec] Main beam bunch spacing [nsec] Main beam bunches / train Repetition rate, Hz PWFA voltage per cell [GV] PWFA Efficiency [%] # of PWFA cells n drive bunch/sec [Hz] Drive bunch energy [GeV] Power in h.e. beam [W] Power in drive beam [W] Avg current in h.e. beam [uA] Avg current in drive beam [mA] Modulator-Drive Beam Efficiency [%] Site power overhead [MW] Total site power [MW] Wall Plug Efficiency 1000 2.9E+10 1.0E+10 25000 500 2 250 100 25 35 20 500000 25 2.0E+07 5.7E+07 40.05 2.29 54 71 283 14% IP Parameters* h.e. bunch gamepsX [m] h.e. bunch gamepsY [m] beta-x [m] beta-y [m] sigx [m] sigy [m] sigz [m] Dy Uave delta_B P_Beamstrahlung [W] ngamma Hd Lum. [cm-2 s-1] Int. Lum. [fb-1 per 2E7s] Coherent pairs/bc e+ e2.0E-06 5.0E-08 5.0E-02 2.0E-04 3.2E-07 3.2E-09 1.0E-05 5.6E-01 2.81 0.14 2.9E+06 0.79 1.2 2.4E+34 474 2.2E+07 *If DR emittance is preserved Other Paths to a Plasma-based Collider • Hi R options --> 100 GeV to TeV c.m. in single stage – – – • SRF Driven Stages – – – • Ramped drive bunches or bunch trains Plasma question: hose stability RF Driver questions: pulse shaping techniques, drive charge is 5x larger 5 stage example of Yakimenko and Ischebeck Plasma question: extrapolate to 2m long 100 GeV SRF questions: 3x5 +1 times the power/m and loading of ILC, wakes and BBU Laser drivers – – – Extrapolate 1 GeV experiments to 25 GeV • Scale up laser power x25, pulse length x5, density x0.04, plasma length x125 • 20 Stages Plasma questions: channel guiding over 1m; injected e-; e+ behind bubble Laser questions: Avg. laser power (20MW/h) needs to increase by 102-104 Critical Issues System Req. N Red=FACET only Blue=FACET Green=Facet partial Issue Tech Drivers Load 2nd bunch Chicane+chirp photocathode g/g Load 2nd bunch Bunch shape Phase control en Matching hosing Scattering Ion motion Plasma sources Plasma channels plasma matching sections Combiner/separators e+ Gradients Nonlinear focusing Accel on e- wake Plasma channels e+ sources phase control E Beam propagation Synchrotron losses Staging or shaping Simulation modeling to guide designs Laser jitter stabilization f Power coupling RF stability w/ hi load, short bunch (CSR) Gas removal & replenish Klystron power CLIC DoD Gas laser program L Final Focus-Plasma lens’ Pointing stability Plasma sources Ultra-fast feedback R&D Roadmap for a Plasma-based Collider Summary • Recent success is very promising • No known show stoppers to extending plasma accelerators to the energy frontier • Many questions remain to be addressed for realizing a collider • FACET-class facility is needed to address them – Lower energy beam facilities cannot access critical issues in the regime of interest – FACET can address most issues of one stage of a 5-20 stage e-e+ TeV collider Backup and Extra Future upgrade or alternative paths • PWFA can be an upgrade path of e-e- or gg options • The following flow corresponds to the afterburner path Beam delivery • NLC style FF with local chromatic correction can be a starting point • ~TeV CM required just ~300m • Energy acceptance (full) was about 2% – within a factor of two from what is needed for PWFA-LC (further tweaking, L* optimization, etc) • Beam delivery length likely be dominated by collimation system (could be +1.0-1.5km/side) – methods like crystal collimation and nonlinear collimations to be looked at again An early (2000) design of NLC FF L* =2m by*=0.1mm 1 TeV Plasma Wakefield Accelerator PWFA Modules P ~10 µs+ Trailing Beam ~1 ns Trailing Beam 5, 100 GeV drive pulses, SC linac Ref.: V. Yakimenko and R. Ischebeck, AIP conference proceedings 877, p. 158 (2006).