Doe FACET Review February 19, 2008 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
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Doe FACET Review February 19, 2008 A Plasma Wakefield Accelerator-Based Linear Collider Vision for Plasma Wakefield R&D at FACET and Beyond e-e+Colliding.
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Doe FACET Review February 19, 2008
A Plasma Wakefield Accelerator-Based Linear Collider
Vision for Plasma Wakefield R&D at FACET and Beyond
e-e+Colliding Plasma WakesSimulation, F. Tsung
Beyond 10 GeV: Results, Plans and Critical IssuesT. Katsouleas
University of Southern California
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
in laser-driven gas jet at RAL)• 2004 ‘Dawn of Compact
Accelerators’ (monoenergetic beams at LBL, LOA, RAL)
• 2007 Energy Doubling at SLAC
RAL
LBL Osaka
UCLA
E164X/E-167
ILC
Current Energy Frontier
ANL
LBL
Research program has put Beam Physics at the Forefront of Science
Acceleration, Radiation Sources, Refraction, Medical Applications
Charge
Context “…mechanism to elevate some new accelerationtechnologies to the next level of demonstratedperformance.”
1. Evaluate the effectiveness of the anticipated ASF R&D program to confront thecriti cal technical issues for very compact, multi-TeV plasma accelerators.
Advise the HEP program on the anticipated scientifi c impact of FACET, whether theimpact is commensurate with the scale of resources required for construction andoperation; the uniqueness of the facilit y; and the existence of similar capabiliti eselsewhere.
1. Evaluate the effectiveness of the anticipated ASF R&D program to confront thecriti cal technical issues for very compact, multi-TeV plasma accelerators.
2. Advise the HEP program on the anticipated scientifi c impact of FACET, whetherthe impact is commensurate with the scale of resources required for constructionand operation; the uniqueness of the facilit y; and the existence of similarcapabiliti es elsewhere.
#4. Advise the HEP program on the anticipated scientificimpact of FACET, whether the impact is commensuratewith the scale of resources required for construction andoperation; the uniqueness of the facility; and the existenceof similar capabilities elsewhere.
Particle Accelerators Requirements for High Energy Physics
• High Energy
• High Luminosity (event rate)• L=fN2/4xy
• High Beam Quality• Energy spread ~ .1 - 10%
• Low emittance: nyy << 1 mm-mrad
• Low Cost (one-tenth of $10B/TeV)• Gradients > 100 MeV/m• Efficiency > few %
Simple Wave Amplitude Estimate
€
∇• E ~ ikp E = −4πen1
kp = ωp Vph ≈ ωp c
n1 ~ no
⇒ eE ~ 4πenoe2c ωp = mcωp
or eE ~no
1016cm−310GeV m
Gauss’ Law
E
1-D plasma density waveVph=c
Linear Plasma Wakefield Theory
€
(∂t2 + ωp
2 )n1
no
= −ωp2 nb
no
Large wake for a laser amplitude a beam density nb~ no
Requirements on I, require a FACET-class facilityUltra-high gradient regime and long propagation issues not
possible to access with a 50 MeV beam facility
Q/ z = 1nCoul/30 (I~10 kA)
For z of order cp-1 ~ 30 (1017/no)1/2 and spot size =c/p ~ 15 (1017/no)1/2 :
• Electron side:•DC gun + DR•Compress to 10 (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
IP Parameters* e+ e-
h.e. bunch gamepsX [m] 2.0E-06
h.e. bunch gamepsY [m] 5.0E-08
beta-x [m] 5.0E-02
beta-y [m] 2.0E-04
sigx [m] 3.2E-07
sigy [m] 3.2E-09
sigz [m] 1.0E-05
Dy 5.6E-01
Uave 2.81
delta_B 0.14
P_Beamstrahlung [W] 2.9E+06
ngamma 0.79
Hd 1.2
Lum. [cm-2 s-1] 2.4E+34
Int. Lum. [fb-1 per 2E7s] 474
Coherent pairs/bc 2.2E+07
E CM at IP [GeV] 1000
N, drive bunch 2.9E+10
N, high energy bunch 1.0E+10
n h.e. bunch/sec [Hz] 25000
Main beam train length [nsec] 500
Main beam bunch spacing [nsec] 2
Main beam bunches / train 250
Repetition rate, Hz 100
PWFA voltage per cell [GV] 25
PWFA Efficiency [%] 35
# of PWFA cells 20
n drive bunch/sec [Hz] 500000
Drive bunch energy [GeV] 25
Power in h.e. beam [W] 2.0E+07
Power in drive beam [W] 5.7E+07
Avg current in h.e. beam [uA] 40.05
Avg current in drive beam [mA] 2.29
Modulator-Drive Beam Efficiency [%] 54
Site power overhead [MW] 71
Total site power [MW] 283
Wall Plug Efficiency 14%
*If DR emittance is preserved
Other Paths to a Plasma-based Collider
• Hi R options --> 100 GeV to TeV c.m. in single stage – Ramped drive bunches or bunch trains – Plasma question: hose stability– RF Driver questions: pulse shaping techniques, drive charge is 5x larger
• SRF Driven Stages– 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
• 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/) needs to increase by 102-104
Critical Issues
System Req. Issue Tech Drivers
N Load 2nd bunch Chicane+chirp
photocathode
Load 2nd bunch Bunch shape
Phase control
nMatching
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
Red=FACET onlyBlue=FACETGreen=Facet partial
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 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 FFL* =2my*=0.1mm
1 TeV Plasma Wakefield Accelerator
5, 100 GeV drive pulses, SC linac
Trailing Beam
~10 µs+
Trailing Beam
Ref.: V. Yakimenko and R. Ischebeck, AIP conference proceedings 877, p. 158 (2006).