SLAC ARD Test Facilities

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SLAC ARD Test Facilities

Tor Raubenheimer

December 8
th
, 2010



SLAC SPC May 2010 Meeting

Page
2


SLAC Accelerator Research


SLAC is largely focused on accelerator
-
based research


SLAC accelerator research is key to the future of the laboratory



Accelerator R&D focused on advancing operating facilities
and the next generation of HEP and BES accelerators



World
-
class research programs in Accelerator Science


High gradient acceleration
: microwave structures, direct laser
acceleration, plasma wakefield acceleration


High brightness sources
: Beam physics and computing


Technology programs to translate research into operations


Laboratory has unique facilities


Experimental facilities for accelerator R&D


Technical support and fabrication capabilities to implement results


Existing Experimental Test at SLAC

Accelerator Research requires R&D facilities



Development has a long timeline



Important to have facilities with different energy scales



Even small facilities are expensive to operate and maintain



University participants require more of a user facility paradigm



Model for facility support is changing but support is critical for future R&D

Work supported by the U.S. DOE under Contract no. DE
-
AC02
-
76SF00515

July 8, 2008

ASTA Test Facility

From Two 50 MW Klystrons

Variable Delay line
length through variable
mode converter

Gate Valves

Two experimental stations inside the
enclosure, one with compressed pulse
and the other without the benefit of
the pulse compressor.

SLAC
Accelerator
Research

Stanford

University

Scientists,

Technical Staff &

Accelerator Hardware
Fabrication

ESB and NLCTA Test Facility

50 MeV capability

RF component testing

Future photocathode R&D

Rapid modifications possible

400 MeV capability with L
-
band (10 MW), S
-
band (30 MW),

and
X
-
band (500 MW) RF sources

RF structure and low
e

gun testing

Low energy beam experiments


Direct Laser Acceleration

E
-
163, Echo
-
7,
e
-
exchange, micro
-
bunching, CSR,

THz, RF Undulator …

Infrastructure for RF system development and laser
-
electron
interaction experiments

FACET
Test Facility

20
GeV

capability

Ultra high density beams

Verification of novel approaches

Unique facilities only possible because of SLAC
linac

FACET
Experimental
Region

L
C
L
S
-
II

I
n
j
e
c
t
o
r

End Station Test Beam

LCLS
Expansion

Po
ssi
ble

LC
LS
-
III

Inj
ect
or

FACET Operation 2012


2017

National &
International
Collaborations

Existing ARD Experimental Program

RF
Linac

and
Technology
Development

High Gradient
Acceleration
experimental research

High brightness beams
and FEL

experimental research

Beam Physics,
Accelerator Design,

HP Computing and

Technical
Infrastructure

FACET, NLCTA, ASTA

FACET, NLCTA, LCLS

NLCTA, ASTA

Note: ESTB not included

as this is largely for HEP

detector R&D although it

will likely receive accelerator

diagnostic proposals as well

Introduction


Source brightness has been increasing 1000x every decade


Future challenges to understand dynamics and time evolution


Requires improved coherence and energy bandwidth


Short pulses and high brightness electron sources


Seeding of soft and hard x
-
ray FELs


Multiple pulses with timing control for pump probe


Meeting these challenges will require advances in both
fundamental accelerator concepts as well as directed
development of accelerator science and technology


Program will need a combination of quasi
-
parasitic use of
operating facilities and a diverse set of dedicated test beds


Role of Accelerator Physics R&D

Page
5


ARD Strategic Goals for Advancing XFELs


Five strategic efforts aimed at XFEL objective

1.
Strong beam and FEL theory effort

2.
Develop new high brightness injectors


LCLS
-
II and upgrades

3.
Development of novel beam handling and seeding techniques

4.
High resolution diagnostics, timing and synchronization techniques

5.
Development of high gradient and high rep rate FEL drivers


Focus on concepts unique to SLAC


high peak brightness



Challenge


This is research, not development or demonstration


Need correctly sized facilities to explore concepts quickly followed by
demonstrations performed at larger scale


SLAC SPC May 2010 Meeting

Page
6


High Brightness Photo
-
Injector


LCLS photo
-
injector performing better than specified:


Opens opportunity for re
-
optimizing FEL complexes


LCLS
-
II


But, factor of ~2x poorer performance than simulations and next
steps for significant improvement are not clear





Path towards a higher brightness injector:

1.
Improve cathode thermal
emittance



cathodes and laser

2.
Reduce space
-
charge and gun aberrations


electron guns

3.
Manipulate beam to optimally use brightness


beam dynamics


SLAC SPC May 2010 Meeting

Page
7


Cathodes and Lasers


Very hot topic with programs around the world


Most groups are focused on high average brightness


High QE to ease laser requirements for high average current


SLAC should focus on high peak brightness, ideally, with multi
-
bunch trains but low still average current


A number of new ideas for better
photocathodes


Coatings, diamond amplifiers, transparent cathodes, …


Study QE and thermal
emittance

performance


Also need to explore operational limitations


Cathode lifetime, damage limits and cleaning procedures


Some of studies can be done in test chambers and some must be
done in operating
rf

guns

Cathode Test Facility


Have dc cathode test chambers to study QE



Build a facility with high rep rate laser to study thermal
emittance
, lifetime and in situ cleaning


Want rapid turn
-
around for R&D studies but include options for
accelerated lifetime testing and gun qualification


Separate thermal
emittance

performance from other issues


Always want higher energy but not clear it is necessary



Possible to utilize ASTA facility to establish CTF capability


S
-
band and X
-
band
rf

power is available


Shielding for 50
MeV

beams but space is limited


start with gun


<2M$ capital cost for lasers, PPS, test stand & controls upgrades


Operation costs ~500k/year (inc. operators, techs & consumables)


ASTA & CTF


Three goals for CTF:



Cathode research



Operational techniques



Rf

gun qualification


Open path to future

collaborations

Electron Guns


LCLS
rf

gun performs extremely well



How to improve?


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 beam loading)


High gradient
rf

gun (reduced space charge and bunch length)



X
-
band
rf

gun offers factor of 4~5 improvement in
simulation but will be challenging to implement


Synergies and collaboration with other programs


Rf

Gun Development


X
-
band
rf

gun has potential to enable compact
linacs


Compact single
-
frequency
linac

compared with lower
rf

frequency


Higher brightness with ~ 3x higher peak currents and smaller

e



Collaboration with LLNL and UCLA on X
-
band gun technology


Construct
rf

gun test stands in NLCTA and Cathode Test
Area in ASTA

Rf

gun detail

Rf

gun test beam line

Beam Manipulation and Seeding


Want to manipulate the beam to optimally use the
brightness,
ie

bunch compression,
emittance

exchange, etc


Study effects deleterious during bunch compression: CSR,
microbunching
, …


Verify
emittance

exchange techniques and beam transformations


Experiments on NLCTA
linac
:


Echo
-
7 completion and Narrow
-
band THz generation


COTR and micro
-
bunching studies


CSR catch
-
up / shielding measurements


Emittance

exchange studies


Rf

and short
-
period
undulator

demonstrations


Upgrade Echo
-
7 proposal 1.8M/yr


BD proposal 3.5M/yr


120 MeV linac with variety of L
-
band, S
-
band and X
-
band
rf

power sources, 3 laser systems and flexible beam line


Direct laser acceleration


Echo
-
7 seeding experiment


Microwave
rf

gun and structure testing


Shared between HEP and BES programs

End Station B Facility for Accelerator R&D

Class 10,000 Clean room

20 feet

Chicane
-
1

Echo
-
7 Beam line

Evolve NLCTA into ‘Injector

Test Facility’ on ~ 2016
timescale


LCLS
-
III

Flexible UV and IR laser

SLAC SPC May 2010 Meeting

Page
14


NLCTA Limitations


Would like
GeV
-
scale beam energy and space for radiator


Present NLCTA
linac

energy is 120
MeV



Installed
rf

makes allows increasing energy to ~300
MeV


Shielding enclosure is only 50m in length


Need to rebuild
linac

or extend shielding to add radiators and
downstream diagnostics


Power and water exist to support additional
rf

power


Largely based on 1
st

generation X
-
band
rf

technology


Expensive to convert everything to S
-
band if that is desired



Planned Upgrades


Improved diagnostics


Installing two X
-
band TCAVs for longitudinal phase space
diagnostics, energy spread control and
emittance

exchange studies


Installing new spectrometer with 4x better resolution


New
rf

gun and capture section


Existing UCLA/SLAC/BNL S
-
band gun


old X
-
band structures

1.
Either install X
-
band
rf

gun and improved capture structures

2.
Or improve S
-
band gun and add S
-
band capture structure


Studies at NLCTA to understand present limitations


Modify 1
st

chicane (Chicane
-
1)


Present system very flexible but difficult to operate


Exploring options for replacement or improvement

SLAC SPC May 2010 Meeting

Page
17


High Brightness Injector Program

Three Parallel Experimental Efforts


Page
17


Cathode Test Facility

ASTA Facility

Photocathode R&D aimed at

understanding LCLS lifetime

and damage issues

Test rf gun modifications before

installation in LCLS
-
I or II

Longer term R&D aimed

at high brightness cathodes

with lower thermal
e


(coatings, smoothness,

new materials)

LCLS
-
II Injector

Incremental upgrade of

LCLS
-
I with opportunity

for R&D during

commissioning


Injector R&D Program

NLCTA Facility

Simulation and experimental

program aimed at significant

improvement in brightness

1)
Design studies on
rf

gun design, CSR micro
-

bunching and cathodes

2)
Rf

gun development and

testing at NLCTA in
2012

3)
NLCTA R&D on injector

beam
physics

Construction in
~2014

and commissioning

in
~2015 to study injector

physics before LCLS
-
II

operation

Combined HB program

requires ~3M/yr

new funding

Timing and Synchronization


fs

scale science requires equally stable
fs

scale accelerator
phasing and timing information over km scale



improved stability and resolution beyond existing state of the art


Beam and radiation properties dependent on timing/synch stability



Research fundamental technical options


Integrated systems combine RF, optical synchronization with
dynamic timing signals, integral diagnostics


Multi
-
drop distribution to 1000s of elements


Build on encoding techniques used in GPS and DSL (adaptive
symbol coding, orthogonal spread spectrum codes)



Proposed joint LBL
-
SLAC program (Fox/Byrd)


~500k/yr
to develop options and technology


More Aggressive Approaches

(in parallel or replacement)


Want multiple facilities for different program scales


CTF/ASTA at few
MeV


Injector system at 100~200
MeV


Beam dynamics studies at few hundred
MeV


Dedicated seeding studies at
Gev
-
scale


Studies at LCLS with high quality high energy beams


Build S
-
band injector for
rf

gun and injector BD studies


Essentially the same as LCLS (LCLS
-
II) injector


Build S
-
band injector in Sector
-
0 to allow
GeV
-
scale studies


Need to understand limitations of merging beams and existing
systems and how to operate FACET.


Build high rep rate X
-
band
linac

for
GeV
-
class studies


Either expand NLCTA or install in new location (ESA ?)