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 13766 (2009)

Snowmass 2013 (arXiv:1308.1145)

IPAC13 (MOPWO011)

IPAC14 (THPRI013)

2Beam driven PWFA @ FACET-II Science Workshop (Oct 14, 2015)

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-LCCounter-propagating drive beam (a la CLIC)

SLAC Pub 13723 & 13766 (2009)

J.P.Delahaye

3Beam driven PWFA @ FACET-II Science Workshop (Oct 14, 2015)

Plasma cell(as optimized by E.Adli: arXiv:1308.1145)

J.P.Delahaye

hdrive to plasma ~ 76%, hplasma to main ~ 66%hdrive to main > 50%

Single bunch process

Main bunch:1E10 charges (1.6 nC), 20 mm bunch length

Drive bunch:2E10 charges (3.2 nC), 25 GeV

Plasma cell:Plasma cell 3.3 m long with 2x1016/cm3 density Transformer ratio: 1, 7.6 GV/m accelerating field 25 GeV acceleration gain per plasma cell.

4Beam driven PWFA @ FACET-II Science Workshop (Oct 14, 2015)

Co-linear beam driven PWFA Linear Collider : Single bunch: continuous operation, high repetition (10 kHz)

SLAC-PUB-15426 (arXiv:1308.1145) IPAC13 & IPAC14

J.P.Delahaye

Long interval between pulses in plasma (100 ms)

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

5Beam driven PWFA @ FACET-II Science Workshop (Oct 14, 2015)

Major beam parameters covering a wide energy range

J.P.Delahaye

6Beam driven PWFA @ FACET-II Science Workshop (Oct 14, 2015)

PWFA extending high energy frontierwith potential of considerable cost & power savings

J.P.Delahaye

PWFA

PWFA

7Beam driven PWFA @ FACET-II Science Workshop (Oct 14, 2015)

Pulsed mode bunch train collisions (a la ILC)

J.P.Delahaye

230 to 600 mApulsed drive linac

feasibility?(NC fully loaded orSC RF low frequency)

Similar bunch structure and beam parameters as the ILC

8Beam driven PWFA @ FACET-II Science Workshop (Oct 14, 2015)

An alternative ILC upgrade by PWFAfrom 250GeV to 1 TeV and beyond?

J.P.Delahaye

ILC TeVupgrade

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 375+12.5 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

9Beam driven PWFA @ 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

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 distributionNo extra power and length

Low luminosity per bunchdue to low charge butcompensated by stronger horizontal focusing and higher repetition frequency

18 TeV

1 TeV

500 GeV

320 m

11 km

10PWFA-LC, Sept 23, 2014

“Artistic” view of the inter-plasma cell layout

J.P.Delahaye

Realistic design of main beam inter-cell

by C.Lindstrom (next)

Drive beam line

Main beam line

PWFA-LC, Jan 20, 2015

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

Pi/2 phase advance

1

RF deflector

RF deflector

Septum3 2 1

1

2

3Pi/2 phase advance

24 4 34

12Beam driven PWFA @ FACET-II Science Workshop (Oct 14, 2015)

Combination of RF transverse deflectors at various frequencies for increasing the number of drive bunches

J.P.Delahaye

13PWFA-LC, March 10, 2015J.P.Delahaye

Alternative multilines drive beam distribution(Carl Lindstrom)

14PWFA-LC, March 10, 2015J.P.Delahaye

Alternative multilines drive beam distribution(Carl Lindstrom)

PWFA-LC, Jan 20, 2015

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

30MV with TCAV(1m) @12GHz

(MV)

PWFA-LC, Jan 20, 2015

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 schemeCo & Counter-propagating drive beam

J.P.Delahaye

17PWFA-LC, March 10, 2015

Rough cost estimation of various options of drive beam distribution of a 3 TeV collider

J.P.Delahaye

Common assumption: drive beam made of bunches with 5cm interval

18PWFA-LC, March 10, 2015

Drive beam generation and distributionSingle-bunch main beam no accumulation with compression(Hybrid 3 TeV LC made of 500 GeV sectors powered by 20 bunches each)

J.P.Delahaye

667ps = 20cm

5 bunches, 4.85A

3.33ns = 1m

0 to 0.5 TeV 0.5 to 1.0 TeV 1.0 to 1.5 TeV

1.5GHz Drive Linac

953m 1649m 2128m

10 kHz kicker

Main beam10kHz 100ms =30km 100ms =30km

Drive beam 1.26 MHz 24% duty factor

SC option compatible with drive beam pulsed operation?

1906m = 6.35ms 3298m = 11.0ms

167ps = 5cm

20 bunches, 19.4A

3.33ns = 1m X4 multiplication

1906/4=476.5mcircumference

238m = 793ns 2*4*3 =24 trains of 5 bunches, 7110m = 23.70ms

100ms =30km

19Beam driven PWFA @ FACET-II Science Workshop (Oct 14, 2015)

ConclusionsPWFA 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