x-band test accelerator & new initiatives

X-band Test Accelerator & New Initiatives

Cecile Limborg, Chris Adolphsen, Tor RaubenheimerMarch 11, 2013

GARD Review @ SLAC

X-Band Test Accelerator (XTA)

Generation of high brightness beams is a key accelerator technology

Goals for the XTA:• High brightness injector (beams accelerated to 100 MeV)

- Study an approach to very high brightness beams• Compact X-band linac

- Study operational issues (timing, alignment, …)• Use facility to support new initiatives

Construct XTA leveraging existing infrastructure• Installed in NLCTA enclosure, uses control room and rf sources• Based on LCLS design; uses LCLS high-level controls & applications

Based on 20 years of X-band rf development22013 General Accelerator R&D Review

NLCTA Facility

50 meter shielded enclosure containing NLCTA and XTA.

Facility has 4 X-band rf sources, 1 S-band rf gun, 1 X-band rf gun, 3 laser systems and supports a variety of acceleration and beam physics R&D activities

2013 General Accelerator R&D Review 3~50 meters

X-band Test AcceleratorCompact (~6 meters) Injector Beamline

42013 General Accelerator R&D Review

High Brightness Electron SourcesState-of-the-art

Groups around the world are pushing on e- source brightness• Peak and average brightness• Focus on peak brightness largely driven by next generation radiation

sources: SwissFEL, PALFEL, MARIE, MEGA-ray, …Two separate issues: transverse and longitudinal phase space

• LCLS S-band gun pushes both

• Cathodes will likelyyield further improvements but gun is still limitation

Recently, strong focus on lower charge bunches Q << 1 nC• Naturally matched to higher frequency rf guns

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From Aug, 2008ICFA BD Newsletter


High Brightness Electron GunsWhat are the next Steps?

LCLS S-band rf injector performs extremely well

How to improve peak brightness?• Many incremental improvements (better field comp, load lock, …)• No concrete ideas for factor of 2 much less a factor of 10

What about different approaches?• DC photo-injector (reduced space charge and emittance from gun)• Low rf frequency gun (reduced field tolerances and peak current)• High gradient rf gun (reduced space charge and bunch length)

X-band rf gun offers factor of ~8 improvement in brightness (in simulation) but will be challenging to implement

• Broad synergies with other programs across SLAC


RF Gun Emittance and Brightness ScalingBenefits of shorter Wavelength

Simple scalings of emittance and brightness suggest: B ~ 1/l2 and ge ~ l whereQ ~ l and sz ~ l

Many applicationsare optimizing towardlower charge beams

• LCLS was designed for 1 nC and typically operates at 150 pC

• Natural for highrf frequency gun

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From J. Rosenzweig modified by Feng Zhou for LCLS

Emittance vs. Charge


Mark-1 X-band RF GunJoint SLAC-LLNL Collaboration

First X-band gun design was built and tested at SLAC in mid-2000’s

Mark-1 incorporateslessons from LCLS

• Racetrack coupler; increased modeseparation; elliptical iris shape


RF Gun Simulation StudiesX-band gun 8x higher Brightness

ASTRA simulations results (after multi-parameter optimization)

High ERF,cathode to beat surface self-field

and reach smaller rlaser and thus smaller e┴

High dEz / dt for short bunches

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X-Band Test Acc. (Simulations) LCLS (Simulations and measurements)

Q [pC] ex,95% [mm-mrad]

sl [mm] Bpeak=Q/sl/e2/1e3

ex,95% [mm-mrad]

sl [mm] Bpeak=Q/sl/e2/1e3

250 0.25 0.228 17.5250 0.28 0.184 17.3 0.40 0.620 2.5220 0.075 0.109 32.6 0.15 0.220 4.0410 0.076 0.055 31.510 0.118 0.042 17.11 0.016 0.080 48.81 0.036 0.025 30.9

cathodeRF

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EQrlaser

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Cecile Limborg

XTA Beamline Diagnostics

The XTA was built with extensive diagnostics similar to LCLS• Beam will be accelerated to over 70 MeV to reduce space charge• Includes 3 YAG and 3 OTR screens, large angle spectrometer,

transverse deflecting cavity, rf BPMs to align structureGoal is to fully characterize the brightness of the X-band injector

2013 General Accelerator R&D Review 10

Gun200 MV/m YAG/

FC

T105~100 MV/m

TD11 (TCAV)3MV

OTR YAG/OTR

YAG/OTRFC

FC

4 Quadrupoleswith BPMs

8 MeV 70 ~ 100 MeV

SpectrometerSolenoid Cavity BPMs

Cecile Limborg

XTA HardwareProject started in 2011

Starting with Mark-0rf gun and old T105accelerator structure

• Mark-1 is fabricated• New T105 is almost

ready

Linac

YAG, Laser Injection chamber

View from dumpMark-1 rf gun

TCAV

112013 General Accelerator R&D Review Cecile Limborg

XTA Commissioning ResultsAs of end of February, 2013

XTA routinely operated with charges up to 30-40 pCEnergy at ~8 MeV from gun and ~70 MeV out of linac Transverse deflector installed and commissionedBunch lengths measured to be 250 fs rms for ~20pC, in agreement with simulationsTuning to small emittances is sensitive to strong jitter and low OTR light level

• Laser noise reduced from 350-500 fs rms down to 70 fs rms• Contribution modulator HVPS measured ~175ppm rms (ie dF~ 0.6 deg rms,

dV/V ~3e-4); Contribution from LLRF still under investigation• OTR replaced by combined dual YAG/OTR

Low charge studies• QE relatively low; increased by lengthening laser pulse• Plans to measure thermal emittance and maybe laser cleaning

122013 General Accelerator R&D Review Cecile Limborg

Future XTA Commissioning TimelineComplete commissioning in FY2013

Goal: demonstrate injector performance by end of 2013Continue with Mark-0 rf gun through August, 2013

• Measure cathode properties: QE and thermal emittance; try laser cleaning

• Work on improving jitter sources: LLRF and modulators• Optimize slice emittance and bunch length

Install Mark-1 rf gun and new T105 in August down• Measure cathode properties: QE and thermal emittance• Optimize slice emittance and bunch length

Program is interlaced with other NLCTA efforts• Operate a shift per day roughly 50% of time


New Initiatives with X-band RF GunInverse Compton Source and Ultra-fast Electron Diffraction

The high brightness source will enable many future programs• Improved beams for E-163 or Echo-75 at the NLCTA or LCLS or FACET• MEGA-ray experiments at LLNL (or SLAC)• An Inverse Compton Source at XTA• An Ultra-fast Electron Diffraction source at XTA

Ultra-fast Electron Diffraction• Large dEz / dt in gun will allow large velocity compression of bunch

• X-Band technology (gun + compressor) promises - 1pC, few fs rms- 8pC, 20 fs rms

• 2-3 orders of magnitude better than present technology

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with divergence < 0.5 mrad REGAE @ DESY

Siwick @ McGill


Why Inverse Compton Scattering (ICS)?Narrow bandwidth and high spectral brilliance

Narrow spectral bandwidth key to improving S/N15

Bremstrahlung Channeling Compton Undulator

Eg ~ 0 – Eb Eg ~ 100g3/2 Eg ~ 4g2 Eg ~ 2x10-4g2

100% BW 10% BW 1~0.1% BW 0.1% BW

High flux Moderate flux Low flux Moderate flux


Inverse Compton Source Characteristics Two features of ICS source make it very powerful

» Easy variation of photon energy (pulse-by-pulse, if desired)» Scan resonances, contrast enhahncement, etc.

» Narrow bandwidth with highly correlated Eg and q» Core spectral width is ~0.1% improved S/N and reduced dose

Wide set of possible applications ranging from medical (oncology & imaging), industrial (spectroscopy & imaging), science and security


Inverse Compton Scattering Sources Two primary approaches to beam generation:

» Ring-based with high rep rate but larger emittance » Linac-based with brighter beams

• SCRF linac has benefits of both» Very different technical challenges

Brightness of source depends onelectron source brightness

For high energy g’s a linac is likely to provide a compactcost-effective path

Many applications are dose limitedand don’t require huge fluxes

ThomX ICS design

MIT ICS design


Some Existing or Planned ICS Facilities

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Facility Type X-ray E(keV)

Rep. Rate(Hz)

Bunches/pulse

Source size†(mm rms)

Spectral flux (approx.)(ph/s/% BW)

PLEIADES (LLNL) Linac 10-100 10 1 10 108 10% BW

AIST LCS (Japan) Linac 10-40 10 1-100 40 107-109 4-10% BW

LUCX (Quantum Beam) SC linac ~5-50 12.5 Hz 100

(future 8x103) 8 ??

*NERL (UTNL, Tokyo) Linac 10-80 10 104 75 x 60 109-2x1010 few % BW

*MIT SC linac 3-30 108 1 2.4 1014 25% BW(>1015 future ERL, FEL?)

*MXI Systems (Tennessee) Linac 8-100 10 1 1010 10% BW

*PLASMONX (SPARC, Italy) Linac 20-380 10 1 5-10 109 ~10% BW

(future FEL?)

Lyncean Tech(California) ring 7-35 65 x 106 1 30-50 109 3-4% BW

(future 5 x 1011) *NESTOR (Kharkov IPT) ring ~6-900 20-700 x 106 1 35 ??

*ThomX (France) ring 50-90 21 x 106 1 40-70 1013 25% BW


Scientific Opportunities with ICSExamples of Applications

Developing a compact source with modest flux at high photon energy will complement DOE SR light sources

• It would provide a relatively compact (room sized) system at a moderate cost but with high performance needed for research


http://www.emsl.pnnl.gov/root/publications/docs/compact_xray.pdf

Anne Sakdinawat, Yijin Liu, Mike Toney

Impact (Beyond Office of Science)Example: Understanding lifecycle of rare earth elements

New Critical Materials Hub recently created at DOE EERE

• “… challenges in critical materials, including mineral processing, manufacture, substitution, efficient use, and end-of-life recycling; …”

Rare earth K-shell binding energies range from 4 to 65 keV• A moderate energy ICS would penetrate typical core samples

An ICS-based microscopy system could be instrumental as an experimental tool in the analysis of the morphology and composition of rare earth materials throughout their life cycle. 2013 General Accelerator R&D Review

20Anne Sakdinawat, Yijin Liu, Mike Toney

Impact (Beyond Office of Science)Example: Understanding Carbon Sequestration and Storage

Goal: understand the flow and storage of hydrocarbons• Determine generative potential

and pay type (i.e., gas vs. oil) to catalog the organic resources

This type of investigation needs to be carried out at different length scales (resolution from ~mm to micron-level to 30 nanometers)

Desired features of the source: 1. High beam energy (for penetrating large specimens)2. Brightness (for desired resolution)3. Energy tunability (in order to retrieve elemental distribution)2013 General Accelerator R&D Review

21Anne Sakdinawat, Yijin Liu, Mike Toney

Impact (Beyond Office of Science)Example: Microbeam Radiation Therapy (MRT)

Goal: Radiosurgery with reduced impact to surrounding tissue• Microbeam Radiation Therapy (MRT)

has been studied at BNL and ESRF:Dilmanian, et al., Natl Acad Sci 2006 Jun 20;103(25):9709-14; Serduc, et al., PLoS One. 2010 Feb 3;5(2): e9028.

• “Growing experimental evidence is showing remarkable tolerance of brain and spinal cord to irradiation with microbeam arrays delivering doses up to 400 Gy with a beam width up to 0.7 mm” (Neurol Res. 2011 Oct;33(8):825-31)

• Rat studies performed with 100 ~ 350 keV photons; need ~MeV x-rays for people.

• ICS would be a possible, compact source

2013 General Accelerator R&D Review22

Serduc, et al., PLoS One. 2010 Feb 3;5(2): e9028

http://www.ncbi.nlm.nih.gov/pubmed?term=Dilmanian%20FA%5BAuthor%5D&cauthor=true&cauthor_uid=16760251

http://www.ncbi.nlm.nih.gov/pubmed/16760251



http://www.ncbi.nlm.nih.gov/pubmed?term=Serduc%20R%5BAuthor%5D&cauthor=true&cauthor_uid=20140254






http://www.ncbi.nlm.nih.gov/pubmed?term=Serduc%20R%5BAuthor%5D&cauthor=true&cauthor_uid=20140254




Inverse Compton Experiment at X-band (ICE-X)

Goal: high brightness gamma beam for precision experiments• Optimizing the system with photon science/medical school experts

Flux of >107 g/s of 0.1 ~ 2 MeV photons with B >109 (g/s/mm2/mrad2/0.1%)• Narrow bandwidth achieved with high brightness beam and long-pulse

laser interaction reasonable beam and laser parameters- Commercially available 10 Hz, 3J, 3ns, YAG pump laser with 30 um laser waist

(I0 ~ 1x1014 W/cm2)

- 5 cm e- beta, 250 pC, ge < 0.4 mm-mrad• Stable beam and laser simpler operating conditions

Upgrades to increase flux & brightness by >1000• Upgrade laser to 120 Hz• Operate with multibunch train (30 bunches / rf pulse)


Inverse Compton Experiment at X-band (ICE-X)Build on the XTA

Build on the X-band Test Area (100 MeV X-band photo-injector)• Build experimental hutch and borrow interaction laser• Lengthen accelerator to generate 235 MeV e- 2 MeV g’s

Support for hutch and experiments from external programs• Start with staged approach to illustrate feasibility

NLCTADumpEcho-75 beamline

XTA/ICS beamline

NLCTA Enclosure

Experimental hutch(upgrade for Echo beamline as well)


Staged Construction of ICE-XICE-Lite (FY2014 – FY2015)

Start from 100 MeV XTA configuration• Complete XTA injector demonstration – October, 2013• Borrow YAG pump laser system (3J, 3ns, 10 Hz at 1 um)• Add IR and laser to generate g’s – March, 2014• Start construction of g-hutch – July, 2014• Operate ICS at 50 to 200 keV – Sept, 2014• Upgrade with multibunch and laser rep. rate for 1000x flux

and brightness – FY2015

Upgrade linac to 235 MeV ICE-X• Install old T105 and two additional T55 structures• Double klystrons in Station 2


SummaryQuality and impact of research over the last four years:

• Working on new e- source with order-of-magnitude improvement in brightness• XTA has gone from concept to beamline in <2 years and commissioning has begun

Expected deliverables over the next 5-10 years:• Demonstration of a new high brightness electron source

- Key accelerator technology

• Utilization of electron source to demonstrate an optimized high energy, high brightness ICS- Broad potential impact in medicine, industry, security as well as science

Benefits of additional investments:• Need 1.5 M$/yr in FY14 and FY15 to complete modification to ICS

Impacts of reduced investment:• Loss of opportunity to demonstrate HEP contribution to accelerator technology

Why at SLAC?• Unique environment with required accelerator, laser and photon science expertise


x-band test accelerator & new initiatives

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