thomas jefferson national accelerator facility

Thomas Jefferson National Accelerator Facility

J. Michael KlopfJefferson Lab - Free Electron Laser Division

Outline of the proposed JLAMP VUV/soft X-ray FEL

and the challenges for the photon beamlines and optics

Workshop on Future Light SourcesSLAC National Accelerator Laboratory

March 1-5, 2010


Outline• Layout and parameters of the existing IR and UV FEL at JLab• Proposed machine design and parameters for the JLAMP

VUV/soft X-ray FEL• Requirements on the photon beamlines and optics for the users

and for FEL R&D• Challenges for the optical beamline design

• damage threshold due to extremely high peak and average brightness

• trade-offs between the pulsewidth and bandwidth of the photon pulses

• need for and requirements on the monochromator systems• separation and delay control for coaxial high energy and low

energy photon sources (e.g. pump-probe experiments)• Preliminary conceptual beamline design• Questions and comments


Jefferson Lab

Jefferson LabNewport News, VA


Existing Jefferson Lab FEL and THz Source

DC Gun

SRF L

inac

Dump

Bunchi

ng Chic

aneIR W

iggler

UV Transp

ort Lin

e

UV FEL IR FEL

THz(CSR)

• 150 MeV, 135 pC, 75 MHz ERL driving IR or UV FEL oscillator• IR: 950 nm – 7 mm• UV: 4 eV (fundamental) 12 eV (3rd harmonic)

• high power THz (CSR) collected from final bunching chicane dipole

• primarily an ONRdevelopment project

• limited user ops• very high average power

• 14 kW IR FEL• 100 W (40 W lab) THz

• ultrashort pulses(100 fs FWHM)


Proposed JLAMP VUV/soft X-ray FEL

• Planned design to Operates from 7 eV table-top laser energy to 500 eV with harmonics

• 3 to 6 orders greater average brightness than FLASH• Scientific case focused on DOE-BES Grand Challenges from

world-class committee• materials science• ARPES (angle resolved photoelectron spectroscopy)• AMO (Atomic, Molecular, Optical Science)• imaging

• Secondary goals address BES R&D priorities (injector, srf, collective effects, seed lasers) for next generation hard X-ray photon facility

• < $100M and fast schedule since it builds on existing FEL infrastructure


JLAMP in the Light Source Landscape

JLAMP delivers important parameter space un-addressed in hard X-ray proposals, with chemical selectivity to measure atomic structure at the nano-scale, measurement of dynamics on the femto to attosecond timescale of electron motion, and imaging

JLAMPLCLS

JLAMPharmonics

JLAMPUltimate LS

JLAMPharmonics

FLASH

FLASH

LCLS


Proposed JLAMP Upgrade Concept

Upgrade three cryomodules to new C100 design with>100 MeV/module

Add two recirculations up in energy and two down in energy recovery

Maintain IR/UV FEL capabilities


Proposed JLAMP Upgrade Concept

• 600 MeV, 2 pass acceleration• 200 pC, 1 mm mrad injector• Up to 4.68 MHz CW repetition rate• Recirculation and energy recovery• 10 nm fundamental output, 10 nm/N harmonic• 50 fs-1000 fs near transform-limited pulses

• Baseline: seeded amplifier operation using HHG• HGHG amplifier + oscillator capability• THz Wiggler for synchronized pump/probe

Items in blue are estimates not from official project sources

Wavelength (nm)

Photon Energy (keV)

Pulse duration (FWHM) (fs)

FEL beamline repetition rate (Hz)

Peak Brightness

Average Brightness (CW)

Average Brightness (bunch trains)

Photons per pulse coherent

Bandwidth

NGLS 1–10 1.2–0.12 0.3–500 105 + 1030–1032 1019–1025 109–1013 10-2–10-6

LCLS 0.15 8.2 80 120 2x1033 2x1022 1024 2x1012 2x10-3

1.5 0.82 240 120 3x1031 8x1020 5x1022 2x1013 4x10-3

JLAMP 10 -1 00 0.1 – 0.01 50-100 4.7x106 1030–1032 1023–1026 1023–1026 6x1012 10-3–10-4

FLASH 6.8 0.18 10–50 5 1029–1030 1016–1017 3x1019 2x1012 10-2

47 0.026 10–50 5 1029–1030 1016–1017 3x1019 2x1012 10-2

XFEL

0.1–6.3 12.4–0.2 100 10 1031–1033 1020–1021 1023–10251012–1014 ~10-3

SPring8 XFEL

0.1 12.4 50 60 1033 1011 ~10-3

FERMI @elettra 3–10 0.41–0.12 ~40 50 1032 1020

1011–1012 ~10-4

NLS

1.24–2.5 1–0.5 20 1000 1032 1021 1011–1012 ~10-4

SwissFEL

0.1–7 12–0.17 0.6–28 100 1031–1033 1020–1021 1011–1013 10-3–10-4


Technical Specs for JLAMP and other Light Sources

Items in italics are measured on operational facilities


Competing Light Source Requirements

• Some users want ultrashort pulses (time resolved)• Some users want minimum bandwidth (spectroscopy)• Some experiments require high repetition rate (pump-probe,

spectroscopy)• Some experiments require low repetition rate or single-shot

(extreme conditions, phase changes, microscopy, holography)• Some users want what they cannot have (DE Dt < ħ/2)• Also want to test scalability/feasibility for multipass ERL driven

FEL

Need to provide large range of achievable FEL parameters


Challenges for Photon Beamlines and Optics

• Damage threshold• average power (thermal management)• peak power (ablation)

• Focusing optics must accommodate variable source point (variable curvature)

• Control and delivery of required time-bandwidth product (DE Dt) to the user endstation

• Monochromator• must operate over very wide spectral band• must be characterized for all polarizations• double-mono necessary for low photon energy

• Must preserve coherence of pulses to endstation• Separation of VUV/X-ray and FIR beams (FLASH design)


Damage Threshold for Beamline Optics

Numbers to Watch†

300 eV 900 eVenergy/pulse: 60 mJ 42 mJs’: 7.9 mrad 3.5 mradarea: 0.98 mm2 0.2 mm2

fluence: 0.06 mJ/mm2 0.2 mJ/mm2

power density: 61 W/mm2 210 W/mm2

* LN2 cooling may be needed *

We have experience with cryo-cooled mirrors whichenabled the 14 kW operation of the JLab IR FEL

†numbers from WIFEL proposalcourtesy of Ruben Reininger (BNL)


Damage Threshold for Beamline Optics

Ablation: fluence/pulse

damage to Au film from a single pulse of the FLASH FEL

(l = 98 nm, 40 fs)Peak power density ~ 100 TW/cm2

Material Threshold Fluence

Carbon: 0.6 mJ/mm2

Silicon: 0.3 mJ/mm2

Gold: 0.4 mJ/mm2

*sample threshold also critical*

courtesy of Ruben Reininger (BNL) and FLASH


Focusing Optics

• The source point moves along the length of the wiggler as a function of e- beam energy and the g wavelength• variable curvature – variable focal length• KB mirror pair – simple, control curvature in each plane

separately

• Is the wavefront preserved?• critical for minimum pulsewidth• could be important in extreme pressure experiments

• Other mirror designs (Pros/Cons)• Toroidal• Ellipsoidal


Control of Bandwidth/Pulsewidth

• Need to have control of the bandwidth delivered to endstation (monochromator)

• Reducing bandwidth increases pulsewidth (transform limit)• Users need to understand bandwidth pulsewidth constraints• Need to have photon diagnostics to characterize bandwidth and

pulsewidth parameters

* Will photon diagnostics be supported??? *


Monochromators for FELs• FEL bandwidth will often be

greater than the experimental requirements

• Monochromators are the primary means for controlling bandwidth

• For high g energy: s’ and l are small small k short pulse

• For low g energy:• photon beam needs to be

“cleaned” of spontaneous and background emission

• double mono can clean beam and preserve pulsewidth

a

s

s’r

k = l/mm

RMS sourcelimited resolution:

al

sll

asl

sin

sin

2ch

krEE

kr

DD

D

RMS illuminated lines:a

ssin

' krN

Each line delays l/c:

htEckrN

ct

lss

la

sl

'sin

'

DD

D

Diffraction limit:24

' DD tElss

courtesy of Ruben Reininger (BNL)


Double Monochromator Design

G : grating M : mirror

• Double mono functions like a prism pair in a mode-locked ultrashort pulse laser

• Bandwidth controlled by slit width


JLAMP Conceptual Beamline Design

collimator

VLSGM

diffractiongratings

narrow spectrum beam

source point

endstation

mirror

variableslit focusing

mirror

K-B mirror pair

full spectrum beam

samplefocus

25 m


Other Beamline Challenges

• Will full coherence be preserved to the sample through all of the beamline optics?

• JLAMP to also include FIR undulator downstream of VUV/soft X ray wiggler (pump-probe studies)• coaxial beams to be separated using a mirror with a hole to

pass low divergence high energy beam and reflect low energy FIR beam (FLASH)

• FIR and X-ray pulse delay scheme at JLAMP to utilize e- bunch “pairs” (FIR pulses lead X-ray pulses) and FIR delay line (unlike FLASH)

WHAT HAVE I MISSED???


Conclusions

• FELs can enable time-resolved measurements on a femtosecond or better time scale combined with X-ray measurement techniques

• The laws of Physics still hold: DE Dt < ħ/2• Monochromators will need to operate over a very wide spectral

range, and must provide a range of spectral bandwidth• Double monochromator is likely necessary for low g energy to

“clean” the beam and preserve the pulsewidth• Average and peak power density must be kept well below damage

threshold for beamline optics…and sample!!! (gas attenuator)• Will photon diagnostics be supported???

WHAT HAVE I MISSED???


Acknowledgements

Ruben Reininger (BNL)Peter Johnson (BNL)Hongbo Yang (BNL)

Jonathan Rameau (BNL)

Michael Gensch (FLASH/DESY)

Kevin Morris (CAMD)

FEL Team (JLab)

This work supported by the Office of Naval Research, the Joint Technology Office, the Commonwealth of Virginia, the Air Force Research Laboratory, The US Army Night Vision Lab, and by DOE under contract DE-AC05-060R23177.

The Jefferson Lab FEL Team

This work supported by the Office of Naval Research, the Joint Technology Office, the Commonwealth of Virginia, the DOE Air Force Research

Laboratory, The US Army Night Vision Lab, and by DOE under contract DE-AC05-060R23177.

April 24, 2009

thomas jefferson national accelerator facility

Documents

jlamp upgrade concept

light source landscape

laser energy

low repetition rate

iruv fel capabilities

light sourcesitems

existing fel infrastructure

hard xray proposals