the infrared fel user facility at jefferson lab · .triggers, video monitoring and recording....

mds[c:My Documents]User Facility 21 August 2001Operated by the Southeastern Universities Research Association for the U.S. Department Of Energy

Thomas Jefferson National Accelerator Facility

Michelle Shinn

talk given by Gwyn Williams

Work supported by U.S. Dept. of Energy under contract DE-AC05-84-ER40150, the Office of Naval Research, the Commonwealth of Virginia, and the Laser Processing Consortium

The Infrared FEL User Facility at Jefferson Lab



OUTLINE

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JLAB ACCELERATOR SITE



THE JEFFERSON LAB FEL FACILITY



FEATURES OF THE IR DEMO FEL IR Demo FEL Characteristics. Superconducting RF, energy-recovering linac. Reliable operation, ~ 80% availability.. high average power ~2 kW in fundamental range (2–8.0 µm). initial operation in 3 spectral regions: 3, 5, & 6 µm. extension to 1.0 µm with 3rd harmonic operation. 340 W demonstrated in October 2000. extensions through the UV with nonlinear conversion crystals. DC photocathode gun enables unique pulse flexibility. sub-ps micropulse at high (18.7, 37.4, 75 MHz) repetition rate. Macropulses as short as 0.8 µs, or as long as seconds. PRF from 0.5 - 60 Hz, locked to AC, or 20 kHz, externally

triggered. Macropulses have low amplitude jitter (< 5% p-p)



IR DEMO LAYOUT



FEL FACILITY UPSTAIRS LAYOUT



FEATURES OF THE FACILITY

. six large, flexible user labs located above FEL (600 m2) containing:. Utilities e.g., compressed air, dry N2, low cond. water, chilled water, vacuum pump (or process gas) exhausts.. 100 Mbps Ethernet, patch panel to Control Room, beam & line-synched triggers, video monitoring and recording.. Continuous monitoring of laser performance - results available in graphical or numerical format.. Analytical tools (e.g., FTIR, SEM, optical microscopy) available on-site or in the adjacent Applied Research Center.



IR DEMO PERFORMANCESpecification Achieved

. Average Power 600–1000 W 2100 W

. Wavelength range 6.5–3 µm 6.5-2.9 µm

. Micropulse energy ~25 µJ 23 µJ

. Pulse length ~2 ps FWHM nominal 0.5-1.7 ps

. PRF 37.425, 18.7 MHz 74.85, 37.425, 18.7 MHz

. Bandwidth ~ 0.2–0.5% 0.2-3.3%

. Timing jitter < 0.2 ps not yet measured

. Amplitude jitter < 20% p-p <10% p-p

. Wavelength jitter 0.02% RMS not yet measured

. Polarization linear, > 100:1 >6000:1

. Transverse mode quality < 2x diffraction limit <2x

. Beam diameter at lab 2 - 4 cm 1.5-3.5 cm



JLab FEL User Facility Developments

. Program Advisory Committee established

• Guidelines for User Proposals are on the web http://www.jlab.org/exp_prog/PACpage/fel_prop_submit.html

. 18 Proposals received and reviewed

• FEL User Training is now taken care of in the user office• http://www.jlab.org/exp_prog/experiments/fel_get_started.html

. Productive FEL user runs. Over 1400 hours delivered in 5 months of user time since Oct. 1999

. First user publications, 2 PRL’s with 2 more PRL’spending

. FEL Upgrades (10kW IR/1kW UV) are proceeding well



JLAB FEL BASIC SCIENCE ACTIVITIES (1999 - 2001)Research topics Participants

. chemical dynamics of highly vibrationally Princeton, UVa

excited molecules

. photophysics at semiconductor interfaces Vanderbilt, OSU, NCSU

. multicolor ultrafast AMO physics CWM, UVa, ODU, UDel

. pulsed laser deposition CWM, JLab, NRL, ODU

. laser-assisted chemical vapor deposition NSU, FSU

. metal amorphization, nitriding U. Göttingen, UMass, SUNY

. rapid thermal processes in polymer surfaces CWM ,UVa, DuPont

. kinetics of carbon nanotube production CWM, Penn State, DuPont

. Terahertz generation RPI, Kansai ARC (Japan),

JLAB, BNL, LBNL

. Thomson-scattered X-ray generation JLab, U. of Georgia



JLAB FEL APPLIED RESEARCHACTIVITIES (1999-2001)

Topic Participants

polymer surface modification DuPont, UVa, Northrop Grumman. amorphization, texturing

metal processing AK Steel, Dominion Resources, CWM, Northrop Grumman, U. Mass, ODU, JLab. amorphous metals. texturing. cutting/welding. PLD

microfabrication Aerospace, Northrop Grumman. non thermal processing. ceramics/glasses



JLAB FEL AND ACCELERATOR PHYSICS (1999 - 2001)Research topics Participants

. Beam breakup studies Merminga, et al.

. FEL laser parameter characterization Shinn, et al.

. Tapered lasing Benson

. HOM measurements Merminga, et al.

. FEL-RF interaction Merminga et al.

. Harmonic lasing Benson et al.

. Harmonic generation Shinn et al

. Difference-orbit sudies Douglas

. FEL Mirror Distortion Benson et al.

. FEL Mirror Losses Shinn et al.



HIGHLIGHTS OF RECENT RESEARCH

. Dynamics of H in Si - Lupke, next talk

. Dynamics in proteins - Austin et al.

. Ablation rates in metals

. Pulsed Laser Deposition (PLD)

. THz radiation generation

. Nonlinear harmonic generation



Protein Dynamics with FEL sources

Austin et al.Princeton U.

Dynamics of myoglobinFelix FEL replicatedat J-Lab.



Nanotubes at the JLab FEL

Penn StateCollege of William and MaryNASA LaRC



WHY DETERMINE ABLATION RATES?

. Knowledge of the average ablation rate benefits several materials processing applications:. Drilling and cutting rates in metals. Pulsed laser deposition (PLD) target removal rates

. Measurements using the FEL help answer questions about materials processing with high PRF lasers:. In what PRF range does a pulsed laser behave as a CW laser?. At our PRFs, does the FEL have the materials processing advantages (clean

cuts, with minimal collateral damage) possessed by other ultrafast lasers?



ABLATION - THE ps ADVANTAGE

. P.S. Banks, et al. SPIE 4065 pp147-160 (2000) 2J/picosecond pulse



DRILLING COMPARISON

0.001

0.01

0.1

1

10

100

Dri

lling

Tim

e (s

)

0.1 1 10 100 Pulsewidth (ps)

JLab data(PRF=37.4 MHz)

LLNL Data(PRF=1 kHz)

0.75 mm stainless steel



. Measured ablation rates in stainless steel as a function of thickness

. At high intensities, i.e., 1012 W/cm2*, sample absorption bands are unimportant

. Looked for indications of plume-FEL interactions

. Lack of a constant ablation rate for different thickness material, along

with the hole quality, indicative these interactions are occurring.

. Still, drilling rates are 104 higher than demonstrated by other ultrafast lasers.

. Approach rates obtained using cw lasers.

. Further studies in the works include:

. Create flat top irradiation profile

. Studies of hole quality and ablation rate as a function of macropulse length

are progressing.

*peak/pulse

ABLATION SUMMARY



PULSED LASER DEPOSITION

. Creates thin films that are otherwise difficult to make by traditional techniques.. Not used commercially because of process problems.. Droplets of target material (macroparticles) also deposit on substrate,

ruining it.

. Lasers with high PRFs, but low energy/pulse may surmount the particulate problem.

A. V. Rode, B. Luther-Davies, and E. G. Gamaly, J. Appl. Phys. 85 pp 4222-4230 (1999).



PLD OF NIOBIUM

. 235 W @ 18.71 MHz PRF for ~ 120 sec., focused to 60 micron diameter spot. Target rotated in high vacuum. Film was ~ 100 nm thick and had a very low particulate density (< 1 cm-2). Growth rate was ~ 1 nm/sec

Plasma during irradiation Resulting film on glass substrate

Photo by Amy Wilkerson, ARC



PLD SUMMARY

. Initial results are very encouraging, with deposition rates in the range 1-10 nm/sec (10 - 100 times higher than typically measured using excimer lasers).. Very low particulate formation.

. Plume generation is so strong that the input viewport is coated and causes problems.. Work on target/sample geometry proceeding.



JLAB FEL HARMONIC GENERATION

Wavelength Conversion CW Powerefficiency (Watts average)

Fundamental 1.6% 1700*3.165 µm (ebeam:light)

Lasing 3rd Harmonic 0.7% 350*1.055 µm (ebeam:light)

2x 40% 56*528 nm

3x 9% 12*352 nm

4x 8% 17 (pulsed)264 nm

*World record for picosecond laser



THE ACCELERATOR IS A SOURCE OF THz RADIATION

. The short bunchlength and high current in the FEL permit high average power generation of THz radiation.. A collaborative research effort between Jlab, BNL, and LBNL has been characterizing the THz output.. Spectrum peaked near 1THz (300

µm) with 2W average power

• THz radiation can be used for imaging in dielectric media• Called T-rays

• Advantages include:• Photons are nonionizing• Picosecond pulses permit time (or depth) resolving

• Current technology makes diagnostic imaging a challenge, due to low laser powers an PRFs



UPGRADE PLANNING. Plan developed for upgrading the IR Demo FEL

• Links stakeholder interests:

DOE: basic and applied research with extended spectral range

IR User Facility (1–60 µm)

UV Demo upgrade (0.2–1 µm)

Industry: upgrade path for kW Demo in UV

higher power (> 10 kW) in IR/UV

Navy: upgrade path for higher power (> 20 kW) in IR

Air Force: High average power, ultrafast source of UV for micromachining. takes advantage of the Jefferson Lab/Nuclear Physics Energy Upgrade goal to design/build higher gradient cryomodules. a three cryomodule device can attain > 160 MV, sufficient for

- 1 kW UV (~ 300 nm)

- 10-20 kW IR (~ 1 µm)



IR DEMO UPGRADE FEL LAYOUT

. Accelerator has a 10 mA injector and 3 cryomodules.. Optical cavity is a near-concentric resonator design. Currently plan to run at powers above 10kW in the mid-IR. Electromagnetic wiggler makes wavelength tuning easier.. Installation scheduled to begin in Spring 2002.



OTHER ADDITIONS TO THE USER FACILITY

. Helios - a 750 MeV compact, superconducting synchrotron donated to FEL User Facility by IBM. Moved to JLab in Nov. 2000. Commonwealth of Virginia is being asked to fund relocation, building addition, and recommissioning costs.



CONCLUSIONS

. We have an active research program at the FEL User Facility:. Applied research involves ~ 11 organizations and 15 people. Basic research involves 20 organizations and ~ 70 people. We operate ~ 1 month/quarter and deliver over 1000 hrs/yr

. We continue to enhance our capabilities.. Harmonic generation in the UV & Vis. > 50W @ 525 nm. > 10 W @ 350 nm (262.5 nm values should be similar). Production of ultrafast THz and X-ray radiation. Synchronized to the IR FEL. Acquisition of Helios synchrotron. Upgrades to the accelerator and optics to produce 10 kW IR and 1 kW UV



ACKNOWLEDGEMENTSSteve Benson Wael IbrahimGeorge Biallas Dave Kashy*Courtlandt Bohn* Geoffrey KrafftJim Boyce Bob Legg*David Douglas Rui LiFred Dylla Frank Manley*David Engwall* Lia MermingaRichard Evans George NeilJock Fugitt* Dick Oepts* Donna Gilchrist Philippe Piot* Al Grippo Joe PrebleJoe Gubeli Tim SigginsKim Haddock* Jinhu Song*Alicia Hofler Trey Thurman*Curt Hovater Richard Walker Richard Hill* Mark WisemanKevin Jordan Dawn Venhaus*

* Alumni Byung YunnMany others from JLab also contributed greatly to the project.