thomas jefferson national accelerator facility
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Thomas Jefferson National Accelerator Facility. Outline of the proposed JLAMP VUV/soft X-ray FEL and the challenges for the photon beamlines and optics. J. Michael Klopf Jefferson Lab - Free Electron Laser Division. Workshop on Future Light Sources SLAC National Accelerator Laboratory - PowerPoint PPT PresentationTRANSCRIPT
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
Thomas Jefferson National Accelerator Facility
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
Thomas Jefferson National Accelerator Facility
Jefferson Lab
Jefferson LabNewport News, VA
Thomas Jefferson National Accelerator Facility
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)
Thomas Jefferson National Accelerator Facility
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
Thomas Jefferson National Accelerator Facility
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
Thomas Jefferson National Accelerator Facility
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
Thomas Jefferson National Accelerator Facility
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
Thomas Jefferson National Accelerator Facility
Technical Specs for JLAMP and other Light Sources
Items in italics are measured on operational facilities
Thomas Jefferson National Accelerator Facility
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
Thomas Jefferson National Accelerator Facility
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)
Thomas Jefferson National Accelerator Facility
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)
Thomas Jefferson National Accelerator Facility
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
Thomas Jefferson National Accelerator Facility
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
Thomas Jefferson National Accelerator Facility
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??? *
Thomas Jefferson National Accelerator Facility
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)
Thomas Jefferson National Accelerator Facility
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
Thomas Jefferson National Accelerator Facility
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
Thomas Jefferson National Accelerator Facility
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???
Thomas Jefferson National Accelerator Facility
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???
Thomas Jefferson National Accelerator Facility
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