Present and Future Program for Accelerator Research at SLAC

Present and Future Program for Accelerator Research at SLAC

Tor Raubenheimer

SLAC DOE HEP Review

July 7 – 9, 2008

July 8, 2008 SLAC Annual Program Review Page 2

ARD Mission

* Develop accelerator science and technology that will enable new accelerators in photon science and high energy physics as well as other fields of science, medicine and industry with R&D aimed at near-term, mid-term, and long-term development– Requires broad spectrum of R&D activities focused on different

timescales and ranging from theory aimed at fundamental questions to experiments directed towards immediate or near-term applications

– Need to determine the balance between long-term, mid-term, and near-term R&D

* Where applicable, support a national and international user program in accelerator R&D


ARD Departments & Functions

* LHC R&D– Contribute to the LHC

operation and upgrades

* Linear Collider R&D– Develop linear collider designs

and technology for NC and SC options

* Advanced Microwave Tech.– Develop advanced rf structures

and sources

* Advanced Accelerator R&D– Research options for ultra-high

gradient acceleration using technologies such as lasers and plasmas

* Accelerator Beam Physics– Supports operating

accelerators and R&D groups with optics designs and understanding of collective effects

* Accelerator Computation– Develop computational

solutions for accelerator design and operation using massively parallel computing

* Test Facilities– Operate and support test

facilities including NLC Test Accelerator, ESB, ESA, ATF & ATF2, and FACET R&D


Overview of Financial Data – FY2008

FY 2008 FTE by Job CategoryARD Division

Permanent PhD, 34.36

Temporary PhD, 8.03

Graduate Students, 5.47

Engineer / Computing

Professional, 55.53

Other, 2.78Administrative / Technician,

7.15

Total FTE: 113.3

FY 2008 Total K$ by ProgramARD Division

Accel Sci, 7,507

Accelerator Development,

9,582

ILC R&D, 5,997

LARP Design Studies, 1,363

Acc Ops NLCTA, 726

PEPII Acc R&D, 1,614

Allocation of PPA DPS, 2,121

Total K$ of ARD: 26,790

* SLAC ARD program was badly hit by December Omnibus bill 21 PPA positions cut


Overview of Financial Data 2007-2010

FY 2007-2010 Total K$ By Cost TypeARD Division

0

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35,000

FY07 FY08 FY09 FY10

(

K$

)

Labor M&S Allocation of PPA DPS

FY 2007-2010 Total K$ By ProgramARD Division

0

5,000

10,000

15,000

20,000

25,000

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35,000

FY07 FY08 FY09 FY10

(

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LARP NLCTA PEPII R&DAccel Sci Accel Development ILC R&DAllocation of PPA DPS


Linear Collider R&D

* P5 noted that a future lepton collider will be a necessary complement to the LHC– A linear collider can provide this capability

* SLAC has been developing LC concepts for 30 years* Many options for the next-generation collider with different

levels of risk and different costs– ILC: lowest risk but high cost– X-band klystron: medium risk but significant cost savings– X-band Two-beam: higher risk but probably greater savings– Plasma wakefield or laser acceleration: much higher risk but

potential for much lower costs

* Strong R&D programs on these different options– Need to understand systems issues and cost scales to direct R&D


A Roadmap for Multi-TeV Lepton Colliders

500 GeV LC

Neutrino source

Neutrino ring

Muon collider(few TeV)

350 GeV LC

Multi-TeV LC

2010 2020 2040 20502030Timescale (personal guess)

Plasma Acc

Superconducting RF

Normal conducting - Two-Beam-based

Normal conducting – Klystron-based

Multi-TeV LC

4th GenerationSR Sources

5th Generation SR Sources?

The LC roadmap illustrates options and connections between them. Selecting a path requires additional information suchas LHC results and technology status


Conventional rf Linear Collider R&D

* Strong leadership in ILC GDE– Working on 1.3 GHz RF power sources, beam delivery

system, electron source, and systems integration– Efforts have broad applicability – not just ILC

* Want to re-invigorate X-band (11~12 GHz) R&D – Provides more conservative solution to normal conducting LC– Excellent High Gradient effort but need power source studies

* Collaboration with CERN and KEK on CLIC– Accelerator structure development and testing

• CLIC structures based on SLAC/KEK work at 11 GHz

– Future collaborations on beam delivery, e+/e- sources, and collective effects (impedance, electron cloud, ion instabilities)

– Building 12 GHz klystrons for CERN testing program


High Gradient R&D

* Long history of X-band rf development– Achieved >400 MW 11.GHz rf power in 400 ns pulses

• Modulators, klystrons, and rf pulse compression

– 1000 hours operation of ~5m X-band structures at 65 MV/m– Strong collaboration with CERN and KEK

* Improved understanding of gradient limitations– Theoretical and experimental studies– Studying rf power flow, arc formation, pulsed heating , …

* Significant improvements in X-band structure capability– >100 MV/m (unloaded) in traveling wave structures

• Collaborating with CERN to develop structures for 120MV/m

– ~150 MV/m in single cell standing wave structures• Potential for very high gradient normal conducting linacs


Understanding the Gradient Choice

* Cost 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 powercost per MW by 2x or double Rs to increase G by 40%

Unloaded Gradient (MV/m)

Rel

ativ

e T

PC

At low gradient, cost increases due to larger length costs

At high gradient, cost increases due to higherrf power costs

GLC/NLC X-band

GLC/NLC RF Power Sources (2004)

* Good success with modulator, pulse compression and rf distribution development. Klystrons achieved peak power and pulse length specs but breakdown rate was too high

Combined Klystron Power

Output Power

(Gain = 3.1, Goal = 3.25)


X-band RF Power Source R&D

* Developing novel rf power sources:– Marx solid state modulator – broad applicability of technology– Sheet beam klystron – broad applicability of SBK concept

* Developed rf power source for GLC/NLC:– SLED-II system delivered >500 MW– Two-Pac modulator fabricated but not fully tested – halted in 2004– X-band klystrons worked at 75 MW / 1.5 us but many breakdowns

→Consider new output structures or reduced power levels using knowledge from high gradient studies

* Future program to complete X-band rf source development– Could provide a more conservative option to X-band design– Broad applicability: power sources for compact radiation sources

and other compact linacs (complements High Gradient Program)


Linear Collider Cost Studies

* Linac cost studies are needed to set X-band gradient and optimize between Two-Beam and Klystron options

* Working with GDE on ILC design and costing– Tried to engage GDE in CLIC/X-band effort and costing as well

* Detailed X-band costs will be needed to optimize between X-band and other technical options– Use the GDE costing methodology – common basis– Performing cost studies in collaboration with CERN– May consider a broader X-band collaboration for these efforts

* High-level costing is needed to help direct R&D efforts– Options for X-band, plasma or laser acceleration


Future X-band Test Facilities (>2012)

* After initial R&D, need a new test facility if either X-band klystron-based or TBA-based collider are to be pursued

* 3 GeV X-band Test Facility– 10 rf units with 100 MV/m X-band linac– Demonstrate emittance preservation, rf stability, and reliability– Completed facility could deliver beams for AARD or BES programs

* Two-Beam Demonstration (STF4 ??)– Next step beyond CTF3 at CERN– Use ~150 SLAC linac klystrons to generate 10 Amp 1 GeV few us

drive beam (share rf with FACET and LCLS-II)– 8x combiner using SLC damping ring complex 80 Amps– Drive beam would power 40 GeV of TBA linac


Advanced Accelerator R&D

* Program to find cost-effective solution to accelerate e-– Need to generate multi-MW beams with low emittance

* Plasma-Wakefield Acceleration (PWFA)– Use drive beam to excite plasma wave and accelerate a trailing

beam no material breakdown limits• Excellent power transfer efficiency >30% in simulation• Possible to generate drive beam with high efficiency like CLIC• Emittance preservation possible in simulation

– Needs experimental demonstration new FACET facility

* Direct Laser Acceleration– Use high electric fields of laser beam to directly accelerate e-

• Does NOT require esoteric PetaWatt lasers • Capitalize on B$ laser industry pushing cost, efficiency and size

– R&D program is making great progress


PWFA-Linear Collider Concept

* Developed a concept for a 1 TeV plasma wakefield-based linear collider– Use conventional Linear Collider concepts for main beam and

drive beam generation and focusing and PWFA for acceleration• Makes best use of PWFA R&D and 30 years of conventional rf R&D

– Concept illustrates focus of PWFA R&D program

• High efficiency

• Emittance pres.

• Positrons

– Allows study of cost-scalesfor furtheroptimization


FACET PWFA Experimental Facility* Progress on PWFA requires new facility to demonstrate single-stage e- acceleration and understand e+ acceleration

– New FACET facility will provide high quality e+ & e- beams forstudies of drive-witness studies of e-/e-, e+/e+ & e-/e+ acceleration

– Developed an R&D program at FACET to determine all parameters of a PWFA-LC from 2010 2016

– Followed by pre-construction multi-stage PWFA demonstration: FACET-II (~100M$ scale similar to current rf LC test facilities)


Laser Acceleration R&D

* High gradient (~GV/m) and high efficiency are possible* Capitalize on large diode-pumped solid state laser

industry and on semiconductor fabrication technology* Structures for High-Gradient Laser Accelerators

– Photonic Crystal Fiber (Silica)– Photonic Crystal Woodpile (Silicon)– Transmission Grating (Silica)

* Possible to generate a reasonable set of parameters for a TeV-scale linear collider

ECM = 500 GeV Laser JLC/NLC N 5106 9.5109 fc 50MHz 11.4kHz Pb (MW) 10 4.5

x/y (nm) 0.5/0.5 330/5 N 0.22 1.1

z (m) 120 300

z/c (psec) 0.4 1 0.045 0.11 L 11034 5.11033

xy

z

laserbeam

cylindrical lensvacuum

channel

electron beam

cylindrical lens

top view

/2

xy

z

laserbeam

cylindrical lensvacuum

channel

electron beam

cylindrical lens

top view

/2

top view

/2

Luminosity from a laser-driven linear collider must come from high bunch

repetition rate and smaller spot sizes, which naturally follow

from the small emittances required


Laser Acceleration — Bunch Train Attosecond Bunch Train Generation

First- and Second-Harmonic COTR Output as a function of Energy Modulation Depth (“bunching voltage”)

Left: First- and Second-Harmonic COTR output as a

function of temporal dispersion (R56)

Inferred Electron Pulse Train Structure

Bunching parameters: b1=0.52, b2=0.39

C. M. Sears, et al, “Production and Characterization of Attosecond Electron Bunch Trains“, Phys. Rev. ST-AB, 11, 061301, (2008).

800 nm 400 nm

400 nm 800 nm

=800 nm


LHC / LARP Activities

* Participate in the LHC accelerator physics program:– Contributing in areas where SLAC has expertise & experience– Enhance SLAC’s areas of core excellence:

• collective effects, RF cavity design, collimation systems,…

– Educate SLAC staff on HEP’s only energy frontier machine

* Collimation– Rotatable Collimator and crystal collimation

* Instrumentation and LLRF diagnostics– Long-term visitor to work on instrumentation projects

* Accelerator Physics– Ecloud; Beam-Beam Studies; Crab Cavity; PS2 Studies

* Management– LARP Level-2 Accelerator Systems leader

LHC Phase II Collimators

SLAC Design

CERN Carbon-Jaw Collimator

SLAC Prototype Jaw

Stable

Unstable

• Errant LHC beams will destroy most materials except Carbon• Carbon has a large resistance and impacts the beam


Super B-Factory R&D

* SLAC could collaborate with Frascati on Super-B design– Possible to consider L ~ 1036 using results from PEP-II with some

improvements: crab waist scheme, improved beam control (very small emittances), e-cloud control, powerful feedback

– Beam control concepts from SRS and LC damping rings– Crab waist tested at DAFNE– Frascati ring would reuse much PEP-II hardware allowing an

inexpensive path for a strong US contribution

* Also possible to collaborate with KEK on KEKB upgrade– Design path with very high currents seems more challenging but

KEK team has demonstrated capability– US role less evident: SLAC could contribute vacuum system,

feedback systems, …


Accelerator Physics

* Strong Accelerator Physics group– Optics design

• ILC Beam Delivery, Bunch Compressor, Damping Rings, e+/e- Sources

• Design of PEP-II and upgrade options

• FACET facility

– Collective effects• Conventional impedance issues

• Electron cloud and beam ion instabilities

– Feedback and LLRF system design• Pioneered bunch-by-bunch feedbacks and diagnostics

– Colliding beam accelerator design• Strong experience with e+/e- IR and systems design

– Massively parallel computation• Leader of EM accelerator computation

Beam Physics and Computing

A Trapped Mode in ILC Cryomodule - Electric fields calculated by Omega3P

• TM-like mode localized in beampipe between 2 ILC TDR cavities

• Damping required to avoid deleterious effects on beam dynamics and excessive heat loads

TM mode

Similar techniques were applied to study the beam breakup problem in the cryomodule of the JLab 12 GeV upgrade

L-Band Sheet Beam Klystron

LBSK DC gun –• Simulated using Gun3P, a parallel, 3D,

high order finite-element electron trajectory code

• Benchmarked against Michelle

• Parallel computation speeds up runtime by an order of magnitude

Input: 115 kVOutput: 129 A

144K tets4.5M DOF’s

Beam profile at cathode

Gun3P

Michelle


Microwave Fabrication

* High precision machining, brazing and cleaning of rf components is a core capability at SLAC– Supports SLAC efforts in rf development as well as world-wide

HEP community• SLAC asked to build 12 GHz klystrons for European labs

• SLAC / KEK / CERN collaboration built best high gradient structures

• SLAC PEP-II klystrons needed to replace industry-built devices

• SLAC regularly consulted on structure fabrication and supports external user base

* Capability is at risk in transition from HEP to BES funding– BES demands and vision for rf development are narrower– Need to work with HEP and BES to develop plan to keep this

core capability

Electron cloud effect – R&D at SLAC

* Intense R&D by many groups– Complicated problem

* Our strategy: eliminate low energy electrons no cloud– Focused on measuring and understanding SEY in acc. environment– TiN-coated aluminum chamber demonstrated consistently low SEY– Other options add further improvement but may not be necessary

* Key collaborations and experiments at other labs:– KEK: grooved chamber and clearing electrodes– CESR-TA: grooved chamber in dipole magnet and simulations– FNAL: effect of SEY in Project-X proton ring– SPS/LHC: grooved chamber in dipoles, simulations and

measurements

* Continue to investigate remaining issues with TiN (long term durability, SEY in magnetic regions, etc.)


PEP-II Low Energy Ring LER1ST INSTALLATION: in situ SEY measurements 2nd INSTALLATION: groove chambers

3nd INSTALLATION: chicane magnetic field tests

PEP-II chambers dedicated to electron-cloud research

1.5% of the ring

2 4 6 8 10 120

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

n

E-c

urr

ent

PEP-II E-cloud Results

Before installation in beam line

After beam conditioning

SEY #1SEY #2

SEY #3SEY #3

Uncoated Al

TiN coated Al1000xsmallerscale


Test Facilities for ARD

* Accelerator Research has four main test facilities:– NLC Test Accelerator and End Station B

• E-163, X-band & L-band rf development

– End Station A• Future test beam and beam physics program

– FACET• PWFA experimental program; user program

– Klystron Test Lab• X-band and L-band rf development; rf gun development

– Also ATF/ATF2 at KEK in which we have a large role

* Test facilities are critical for ongoing advancement of accelerator science and technology– Need to provide support in era when HEP facilities are closing


Future plans for ARD Test Facilities

* FACET:– >20 GeV; 2x1010 e+ or e-; >20kA; <10 um spot sizes– Planned to be dedicated 75% to the directed PWFA-LC program and

25% for a user program– External advisory committee to recommend experiments

* End Station A– ~10 GeV; ~1x1010 e- or few 107 hadron beams– Proposal for test beam facility for detector and IR instrumentation

development; requires new PPS system and BES agreement

* NLC Test Accelerator– <350 MeV; ~1x1010 e-; z < 1 mm (100 um); < 5 mm-mrad

– Laser acceleration; L-band and X-band rf development– Soliciting proposals for new experiments but not to support as a user

facility


Contributions to Project-X

* SLAC has been collaborating with Fermilab on the L-band rf system – essential for ILC and Project-X– Planning to deliver rf distribution systems; fundamental mode

couplers; 10 MW klystron– Would play a large role in the rf system design and construction

* Planning to work on electron-cloud issues for Project-X– Simulation and modeling studies– Electron cloud experimental apparatus for use in Main Injector

* Could take additional roles:– Beam optics and nonlinear dynamics– Detailed impedance model and instability calculations– Complete model for beam losses and collimation including

nonlinear optics, space charge, and collimators


Summary

* Excellent accelerator research program– World-class beam theory and computation group and world-

class rf design, fabrication, and testing facilities – Host to US High Gradient collaboration and forming a PWFA-LC

collaboration

* Options to collaborate on Super B-factory– Leverage US investment in PEP-II and SLAC expertise

* Broad program to advance energy frontier– Superconducting LC, X-band LC, PWFA and laser acceleration

• Different timescales, risks and costs

• Want to increase efforts on alternates to ILC to provide options

– Linear collider Roadmap – document available in September


ARD Talks Agenda

Plenary8:00 Present and future program for accelerator research Raubenheimer 35+58:40 ILC and SiD programs Phinney 25+59:10 High gradient program Tantawi 25+5 9:40 Plasma acceleration research and FACET Hogan 25+5

Breakout11:00 E163 and laser acceleration E.Colby 25+511:30 Electron Cloud R&D J. Ng 25+512:00 Lunch 4512:45 ATF/ATF2 experiment and BDS program A. Seryi 25+513:15 L-band and X-band rf sources C.Adolphsen 30+1013:55 NLCTA and ESA programs C. Hast 20+514:20 LHC Accelerator Research T. Markiewicz 20+514:45 Super B studies U. Weinands 20+515:10 Beam Physics Y.Cai 20+515:35 Advanced Computation studies C.Ng 20+516:00 Break 30

Documents

Present and Future Program for Accelerator Research at SLAC