Beam Driven Plasma-Wakefield Linear Collider: PWFA-LC J.P Delahaye / SLAC On behalf of J.P. E. Adli, S.J. Gessner, M.J. Hogan, T.O. Raubenheimer (SLAC), P.Muggli (MPI), C.Lindstrom (Oslo University), A. Seryi (Adams Inst.) W. An, C. Joshi, W. Mori (UCLA) Co authors of: SLAC Pub (2009) Snowmass 2013 (arXiv: )arXiv: IPAC13 (MOPWO011) IPAC14 (THPRI013)

2 Drive beam generation & distribution derived from CLIC (CTF3 validation) Pulsed main beam: 125b * 4ns * 100Hz Effective accelerating gradient dominated by inter-plasma cell (100m) 25 GeV/100m = 250 MeV/m Cost and power consumption dominated by turn arounds (40 at 1TeV) Every plasma cell (25 GeV acceleration) Short interval (4ns) between bunches in plasma Plasma relaxation? Original concept of a beam driven PWFA-LC Counter-propagating drive beam (a la CLIC) SLAC Pub & (2009) J.P.Delahaye Beam driven FACET-II Science Workshop (Oct 14, 2015)

3 Plasma cell (as optimized by E.Adli: arXiv: )arXiv: J.P.Delahaye Beam driven FACET-II Science Workshop (Oct 14, 2015)  drive to plasma ~ 76%,  plasma to main ~ 66%  drive to main > 50% Single bunch process Main bunch: 1E10 charges (1.6 nC), 20  m bunch length Drive bunch: 2E10 charges (3.2 nC), 25 GeV Plasma cell: Plasma cell 3.3 m long with 2x10 16 /cm 3 density Transformer ratio: 1, 7.6 GV/m accelerating field 25 GeV acceleration gain per plasma cell.

Co-linear beam driven PWFA Linear Collider : Single bunch: continuous operation, high repetition (10 kHz) SLAC-PUB (arXiv: ) IPAC13 & IPAC14arXiv: J.P.Delahaye 4 Beam driven FACET-II Science Workshop (Oct 14, 2015) Long interval between pulses in plasma (100  s) Effective feedback at IP by high repetition rate Large geometric acceleration: 25GeV/30m=833MeV/m Efficient drive beam acceleration by SCRF recirculating linac (continuous operation) No turn around Drive & main bunches synchronisation by magnetic chicane (2ns=60cm) at each plasma cell

5 Major beam parameters covering a wide energy range J.P.Delahaye Beam driven FACET-II Science Workshop (Oct 14, 2015)

6 PWFA extending high energy frontier with potential of considerable cost & power savings J.P.Delahaye Beam driven FACET-II Science Workshop (Oct 14, 2015) PWFA

Pulsed mode bunch train collisions (a la ILC) J.P.Delahaye to 600 mA pulsed drive linac feasibility? (NC fully loaded or SC RF low frequency) Similar bunch structure and beam parameters as the ILC Beam driven FACET-II Science Workshop (Oct 14, 2015)

An alternative ILC upgrade by PWFA from 250GeV to 1 TeV and beyond? J.P.Delahaye 8 ILC TeV upgrade One possible scenario could be: 1) Build & operate the ILC as presently proposed up to 250 GeV (125 GeV/beam): total extension 21km 2)Develop the PFWA technology in the meantime (up to 2025?) 3)When ILC upgrade requested by Physics (say up to 1 TeV), decide for ILC or PWFA technology: 4) Do not extend the ILC tunnel but remove latest 500m of ILC linac (beam energy reduced by 12.5 GeV) 5) Install a bunch length compressor and 16 plasma cells in latest part of each linac in the same tunnel for a GeV PWFA beam acceleration (465m) 6) Reuse the return loop of the ILC main beam as return loop of the PWFA drive beam 500 m Beam driven FACET-II Science Workshop (Oct 14, 2015)

ILC afterburner from 500 GeV to 1 TeV by PWFA An efficient TeV-LC without drive beam generation J.P.Delahaye 9 Beam driven FACET-II Science Workshop (Oct 14, 2015) ILC acceleration till 500 GeV Each 250 GeV ILC bunch split: - one drive bunch(2/3 charge) - one main bunch(1/3 charge) PWFA till 1 TeV: Drive bunch provides 50% energy to main bunch thus doubles main beam energy No drive beam generation and distribution No extra power and length Low luminosity per bunch due to low charge but compensated by stronger horizontal focusing and higher repetition frequency 18 TeV 1 TeV 500 GeV 320 m 11 km

10 “Artistic” view of the inter-plasma cell layout J.P.Delahaye PWFA-LC, Sept 23, 2014 Realistic design of main beam inter-cell by C.Lindstrom (next) Drive beam line Main beam line

Extraction of last drive beam bunch from the drive beam pulse by state of the art Kickers (developed for ILC Damping Ring) with a rise time of 2ns Minimum interval between bunches of 2ns at 25 GeV Drive bunches synchronisation by magnetic chicane with 60cm delay 4 SC bending magnets 7.5 T, 2m long (280mrad) for each plasma cell Shorter rise time with RF transverse deflectors Bunch interval a fraction of wavelength (ex with 4 bunches) Works only for a limited number of bunches 4 bunches powering 4 plasma cells Corresponding to a collider of 200 GeV c.m. Bunch interval = RF deflector period/4 Interval between drive bunches and magnetic chicane? J.P.Delahaye PWFA-LC, Jan 20, 2015 Pi/2 phase advance 1 RF deflector Septum Pi/2 phase advance

12 Combination of RF transverse deflectors at various frequencies for increasing the number of drive bunches J.P.Delahaye Beam driven FACET-II Science Workshop (Oct 14, 2015)

13 J.P.Delahaye PWFA-LC, March 10, 2015 Alternative multilines drive beam distribution (Carl Lindstrom)

14 J.P.Delahaye PWFA-LC, March 10, 2015 Alternative multilines drive beam distribution (Carl Lindstrom)

Drive bunch interval of (1.5E9*4 )-1 = 0.167ns or 5cm Compatible with efficient drive beam generation by SC recirculating linac equipped with 1.5 GHz SC RF cavities and multiplication frequency by a factor 4 (a la CLIC) Reasonable drive beam intensity of 19.4 Amp during pulse Reasonable magnetic chicane with for each cell: 4 magnets 2.4m long and 2 T with 50 mrad deflection Transverse deflectors (2 of each kind for each cell) Tentative sketch Drive beam and chicanes J.P.Delahaye PWFA-LC, Jan 20, MV with (MV)

1.2 TeV acceleration based on co-propagating drive beam scheme with magnetic chicanes: One beam turn-around for every additional 1.2 TeV c.m. Number of turn-arounds reduced by a factor 48 in respect with counter-propagating drive beam scheme A hybrid scheme Co & Counter-propagating drive beam J.P.Delahaye PWFA-LC, Jan 20, 2015

17 Rough cost estimation of various options of drive beam distribution of a 3 TeV collider J.P.Delahaye PWFA-LC, March 10, 2015 Common assumption: drive beam made of bunches with 5cm interval

18 Drive beam generation and distribution Single-bunch main beam no accumulation with compression (Hybrid 3 TeV LC made of 500 GeV sectors powered by 20 bunches each) J.P.Delahaye PWFA-LC, March 10, ps = 20cm 5 bunches, 4.85A 3.33ns = 1m 0 to 0.5 TeV 0.5 to 1.0 TeV1.0 to 1.5 TeV 1.5GHz Drive Linac 953m1649m2128m 10 kHz kicker Main beam 10kHz 100  s =30km Drive beam 1.26 MHz 24% duty factor SC option compatible with drive beam pulsed operation? 1906m = 6.35  s 3298m = 11.0  s 167ps = 5cm 20 bunches, 19.4A 3.33ns = 1m X4 multiplication 1906/4=476.5m circumference 238m = 793ns 2*4*3 =24 trains of 5 bunches, 7110m =  s 100  s =30km

Conclusions PWFA a very promising technology: Attractive schemes possibly extending LC reach in multi-TeV range Potential of considerable savings (Cost & Power): High accelerating fields: effective 833 MeV/m (10*CLIC) Excellent power efficiency (Wall-plug to beam ~ 20% = 2*CLIC) Great flexibility of time interval Continuous or pulsed mode of operation An alternative for ILC energy upgrade? Many challenges still to be addressed Adaptation to e+ acceleration (tentatively assumed similar to e-) ! Beam quality preservation, efficiency, etc… High energy applications heavily rely on multi-stages Inter-space plasma cell design critical (main & drive beam lines) Short(er) matching section from plasma to plasma (larger effective gradient) Magnetic chicanes detailed design including CSR (short bunches) Most appropriate drive beam generation & distribution? Major issues should be addressed in FACET-II Two stages system test in FACET-II (phase 4)? Optics corrections, tolerances, etc…. J.P.Delahaye 19 Beam driven FACET-II Science Workshop (Oct 14, 2015)