FEL R&D

Zhirong Huang

May4, 2011

Pre-SPC Meeting for Accelerator R&D

H.-D. Nuhn,H. Winnick

Ligh

t Sou

rces

at ~

1 Å

LCLS

LCLS-II

1010

storage rings

FWHM X-Ray Pulse Duration (ps)

Pea

k B

right

ness

(pho

tons

/s/m

m2 /m

rad2 /0

.1%

-BW

)

Why FEL R&D?• Seeded FELs with Full Coherence are the next Frontier

– Narrower bandwidth, stable pulse form– FEL efficiency is greatly enhanced with a tapered undulator

• Smaller emittance, higher peak current– Advanced cathodes and guns– Bunch compression, mitigation of collective effects– Emittance exchange/conditioning

• Ultrafast techniques and instrumentations to fully utilize XFELs

• Average brightness enhancement• Special source and polarization are highly designable

FEL R&DPage 3

FEL R&DPage 4

National and International context• LCLS is the first and only hard x-ray FEL.

• LCLS-II will be built in the next six years.

• Next Generation Light Source (LBL) closes in on CD-0, needs extensive R&D on seeding etc.

• Many XFEL projects on the international stage: SPring8 (Japan), FERMI (Italy), PSI (Switzerland), FLASH and FLASH-II (Germany), European XFEL, Pohang (Korea), Shanghai (China)…

FEL R&DPage 5

Charge from Norbert and Jo

• Identify and prioritize the experiments that should be executed at the LCLS, and if required at other SLAC accelerator test facilities.

• Involve the FEL community in the design, preparation, execution, exploitation and potentially even the funding of these experiments.

• Develop an integrated program that has near-term, mid-term and long-term goals and that spans the breadth of accelerator and x-ray based science and technology from basic physics to FEL science and into ultra short beam diagnostics.

To Jerry Hastings, Zhirong Huang (Jan. 21, 2011)

Overall program

FEL R&DPage 6

Two equally important categories

• A class of experiments necessary to improve LCLS operation as well as those that will be instrumental in deciding what the detailed configuration of LCLS II

• A class of experiments that would benefit not only SLAC but the larger FEL community.

Parameter Now Future

Photon energy, keV Up to 10 Up to 100Pulse repetition rate, Hz ≤ 120 102-106

Pulse duration, fs ~2-300 <1-1000

Coherence, transverse diffraction limited

diffraction limited

Coherence, longitudinal not transform limited

transform limited

Coherent photons/pulse 2x1012-3x1013 109-1014

Peak brightness, ph/s mm2 mrad2

0.1% bandwidth 1033 1030-1034

Average Brightness, ph/s mm2

mrad2 0.1% bandwidth 4x1022 1018-1027

Polarization linearvariable, linear

to circular

X-ray FEL Parameters – Now and Future(C. Pellegrini et al., summary of FEL workshops.)

red: parameter space to be developed

SLAC wants to be a big part of this future!

FEL R&D planning process• Standing meeting to discuss FEL R&D plans.• Identify projects, lead physicists and engineers.• A concurrent task force led by Bob Hettel looks into test

facilities for many R&D areas. • Seek a variety of funding streams: AIP, MIE, BES, HEP

• R&D planning is ongoing, new ideas and projects will be addressed as they arise.

• Look for collaborations (national and international) and suggestions

FEL R&DPage 8

FEL R&D Program with essential components for LCLS II, NGLS and other FELs

2011-12 2015-162013-14 2017-18 2019-20

LCLS-II injector LCLS-II completion

HXRSS

Injector studies(LCLS-II injector)

ITF (Sector 0-9) to enable advanced beam generation, manipulation, compression and seeding at high energy

Temporal diagnostics & timing

Attosecond x-ray generation

FEL Seedingschemes

Beam brightness & manipulation

Technologydevelopment

Ultrafast techniques

ECHO-7+

SXRSS demo

Laser & phase error control

THz & Polarization

THz generation

Polarization ctrl.

Multi bunches, detectors, short-period undulators, high-rep. rate

CTF/GTF(Cathode,

Gun)

X-ray Beamline R&D

LCLS R&D Projects

FEL R&DPage 10

LCLS undulator

HXRSS(hard x-ray self seeding)

XTCAV(X-band trans. cavity)

SXRPC(Soft x-ray polarization control)

THXPP(THz/x-ray pump/probe)

XRSSS(X-ray single-shot spectrometer)

EXRLT(experimental x-ray to laser timing)

MBXRP(Multi-bunch x-ray production)

XRDBL(X-ray R&D Beamline)

Self-seeding of 1-mm e- pulse at 1.5 Å yields 10-4 BW with 20-pC mode. Undulator taper provides 30brightness & 25 GW.P. Emma (SLAC), A. Zholents (ANL)

FEL spectrum after the diamond crystal

Geloni, Kocharyan, Saldin (DESY)

Hard X-ray Self-Seeding (HXRSS)

1 GW ~25 GW

3.2 m

wall side

Schedule and costs

Concept and Design 4 monthsConstruction and Installation 5 monthsCommissioning 6 shifts (8 hrs/shift)** plus 2 weeks pre-beam checkout

Stages of Project Development:

Cost Estimate 0.94 M$Add 30% Contingency 1.22 M$

Project Costs:Est. Commissioning Date Dec. 2011

FEL R&DPage 12

FEL ON FEL OFF

13

time

e-

sz

2×1 m

bd bs

D 90°

V(t)RF

‘streak’ Dipole

X-band TCAV

ener

gyDy

High resolution, ~ few fs; Applicable in all FEL wavelength; Beam profiles, single shot; No interruption with operation; Both e-beam and x-ray profiles.

e-beam x-ray

X-band Transverse Cavity (XTCAV)

Y. Ding

X-band rf freq = 11.4 GHz

)( 0

,

0 sE

V x

xNrf

b

resolution

fs-resolution electron and x-ray temporal diagnostics

Provide missing LCLS capability for tuning SASE process

Measure pulse length similar to soft X-ray statistical method

Serve as prototype for LCLS-II XTOD spectrometer

Provide diagnostic for hard X-ray self-seeding

Hard X-Ray Single-Shot Spectrometer (HRSSS)

FEL R&DPage 14

M. Yabashi, J. Hastings et. al. PRL 97, 084802 (2006)

Glassy-carbon

1/DT

1/tc

SASEspectral spikes

(Optional)Designed operating range4 -13 keV

10 keV

Si <555>Y. Feng

Exp. X-ray to Laser Timing (EXRLT)

Spectrometer

Ti:Sapph laser

SiN

wavelength

stacked spectra

Measure x-ray to laser timing to <10fs (rms)● Hard x-rays: RF cavity timing

● Soft x-rays: chirped continuum technique

● Chirped continuum uses x-rays to induce a change in refractive index

R. Coffee

Soft x-rays

Two bunches to serve SXR/HXR in LCLS-2

Two bunches for THz/X-ray

Multiple bunches (separated by ~10s ns) to increase hit rate on samples

Multi-Bunch X-Ray Production (MBXRP)

8.4 ns

FEL

Higher hit rate of virus in jet

1mm

/10n

s

Sample source

2-Bunch lasingdemonstrated

F.-J. Decker

Develop electron and photon multi-bunch diagnostics for reliable operation

FEL R&DPage 16

Soft X-ray Polarization Control (SXRPC)

linearvertical 500 eV …

500 eV– …

2. Circular Polarizer (Fundamental)

Phase Shifter

linear horizontal circular

Lowest Cost;Reduced degree of polarizationDegree of polarization fluctuates

1. Crossed Polarizer (Fundamental) – Fast Switching

High degree of polarization;High intensity; Degree of polarization stable

– Slow Switching

Afterburner

linear horizontal

Existing LCLS undulator Afterburner

Exiting LCLS undulator

Adding APPLE undulators to LCLS for polarization control

• Polarization Control Photon Range: 500 eV – 2000 eV• Additional tapered undulator for HXRSS• APPLE gap changes to Second Harmonic Afterburner

H.-D. Nuhn

(Advanced Planar Polarized Light Emitted)

THz/X-ray Pump Probe (THXXP)• Laser-based THz sources are insufficient for pump-probe• LCLS can create a quasi-unipolar pulse with >1 GV/m and

>100 µJ that is synchronized with x-rays

A. Fisher

FEL R&DPage 18

X-ray R&D Beamline (XRDBL)

Pulse stealing at 1 Hz (out of 120 Hz), available in parallel with normal LCLS operation

Provide a development and test area for hard x-ray methods and instrumentation (for example: detectors)

FEL R&DPage 19

Near Experimental HallAMO SXR XPP

Pulse pick-uplocation

S. Moeller

FEL R&DPage 20

LCLS R&D Summary• Hard X-ray Self-Seeding: seeded FEL at hard x-ray regime

• Single-shot diagnostics: temporal (X-band TCAV), spectral (hard x-ray spectrometer), timing (exp. x-ray laser timing)

• Multi-bunch X-ray Production to increase rate, brightness

• Synchronized pump/probe sources (THz/X-rays)

• Control of radiation properties (polarization control)

• X-ray beamline R&D

Program Execution Plan• LCLS R&D projects will be managed uniformly• Each project has lead physicist(s), engineer(s)• Project scope, schedule, cost must be clearly defined• For example

Other R&D areas

• Echo-7• ITF for laser seeding at high energy• Laser• Detector • …

FEL R&DPage 22

ECHO-7 at NLCTA

ECHO is a novel harmonic generation technique from laser-beam interaction (seeding options for NGLS and LCLS-II SXR)

5th harmonic generated with ECHO technique

The facility is under upgrade for benchmark of ECHO theory at higher harmonic number (>=7)

350 400 450 500 550Radiation wavelength (nm)

ECHO

1590 nm laser on

795 nm laser on

Both lasers on

600

First ECHO signal

FEL R&DPage 23

D. Xiang

FEL R&DPage 24

ITF for high-energy seeding/compression

Collaborating with LBNL to develop a high-energy test facility (S0 ITF) to

perform critical R&D (Echo-100, HHG seeding) for NGLS and other FELs

Based on the first 1 km of the SLAC linac, use an LCLS-like injector

Serve as a testbed for advanced beam generation, compression

J. Frisch

Seeding laser system Transform

Limited Pulse

“Chirped”Pulse

Oscillator

Amplifier

Harmonics

• Laser phase error is amplified by harmonic number N in harmonic generation FELs

• Need to measure and control laser spectral phase to better than ~1/N ~ 10 mrad (for N ~ 100)

A. Fry

Seed Laser Phase Error Control

Seeded spectra

FEL R&DPage 25

SAC Meeting April 18-19, 2011

Charge: Evaluate the presented LCLS R&D projects:

1. Are the proposed R&D projects important from a science/LCLS user point of view?

2. Which do you consider the most important ?

3. Should other R&D projects be added at this time ?

FEL R&D program presented to LCLS SAC

FEL R&DPage 26

SAC defined categories

• Must do (self-seeding, single-shot diagnostics, Detector)

• General Benefit (multi-bunch, X-ray beamline)

• Smaller subset of users (THz, polarization)

• LCLS-II and wider community (Echo-7+, laser phase error)

• SAC comments that ‘real time’ data analysis/on-line data reduction are crucial for the users

FEL R&DPage 27

FEL R&DPage 28

Conclusions• LCLS, LCLS-II create excitement in FEL and x-ray sciences.

• A vibrant FEL R&D program is an essential element of the SLAC future.

• R&D projects are being pursued not only for LCLS, but also for the larger FEL community.

• The program benefits from strong national and international collaborations.