As the FEL program enters its tenth year, lean resources still limit the pace. Nonetheless, all the original goals are being achieved and more. Since the last consortium meeting in June 1999:

• The FEL exceeded 170% of its design power and delivered more than 200 hours of 3 - 6 micron beam to the user labs in the sum of two month-long running periods. New capabilities beyond the original version emerged: useful power at wavelengths much shorter than the primary output via harmonic lasing and picosecond pulsed x-rays by scattering the electron beam off the laser output.

• The start-up and commissioning are encountering surprisingly few problems considering the novelty of the undertaking, surely a tribute to those responsible for the FEL's design, construction and operation. No issues have emerged that limit attainment of any of the original goals.

• The program and technology path is in place for a ten-fold power upgrade with wavelength expansion from the present 3 - 6 micron range to 2 - 20 microns. A follow-on will add 1 kW of UV down to 250 nm.

• Key experiments demonstrated the FEL's capability to do scientifically important and technologically useful work.

• Clear procedures are now in place for seeking FEL beamtime, arranging for use of facilities, getting required safety training for personnel and safety approval for experiments. They will be put on the JLab website. Improvements in clarity and user-friendliness will be in place before the summer running period. Efficiently, fairly and safely serving our growing community depends on all of us faithfully following the procedures.

Main characteristics of the present FEL operation are:

• High average power (100's of watts) is available from 3 - 6 mm, with individual micropulse energy up to 15 mJ. Highest pulse energy increases the spectral width of pulses to 2.5%, from 0.4% at 3.1 mm, which may be significant for some experiments. Minimum micropulse length (FWHM) is about 0.7 ps, with a maximum separation of 55 ns. In addition to the primary wavelength, harmonic lasing can deliver watts at 1 micron, though stability issues require resolution before that light can be usefully exploited. Straightforward improvements to the optical cavity and transport system could raise the harmonic power several-fold. Available pulse formats range from CW to macropulses as short as 10 ms at any reasonable macropulse repetition rate. The beam is highly polarized (6000:1). Since laser operation may not be drift-free on the time scale of hours with presently installed equipment. Experimenters need to identify and monitor critical parameters, e.g., wavelength, micropulse energy, beam pointing.

• Most operating regimes do not permit users to be in the lab while beam is being delivered. However, they may be present during "alignment mode" conditions: 18.75 MHz, 250 ms (or less) macropulse length, 2 Hz or less macropulse repetition rate. Many users chose alignment mode for either set-up or experiments. Burst mode delivers macropulse having a chosen length, repetition rate and total number.

• Generally-available facilities in the user labs remain spartan. Since most experimenters are already working with lasers, they are able to bring what they need. Researchers doing so need to be aware that they need safety approval for the equipment and the experiments before operations can begin.

• FEL users need to take care of several procedural matters before their work can begin. Required safety training is available through the JLab User Liaison Office and includes: general safety, radiation safety, laser safety and oxygen deficiency hazards. The experiments to be carried out at the FEL also require both safety approval and instructions to the FEL operator as to what beam is to be provided. The Experimental Safety Approval and Laser Test Plan forms are available in MS Word from George Neil (neil@jlab.org) and will be on the JLab website.

• Existing IR Demo: Envisioned performance improvements include: beam-shaping optics to give other than Gaussian profiles, e.g., top-hat for micromachining; a pulse-picker to deliver micropulses individually or at a chosen rate; a pulse-stacker to combine and deliver the energy from a train of FEL micropulses as much larger micropulses at a correspondingly reduced repetition rate; a stretcher/compressor combined with chirping the FEL to extend the pulse length range to about 0.1 - 10 ps; an optical cavity to accumulate the energy of successive pulses for in-cavity experiments that need high peak power but consume little net energy.

• IR Upgrade (3 cryomodules): wavelength range becomes to 2 - 20 mm, micropulse energy increases 10 X over IR demo and average power exceeds 10 kW. If a wiggler like the OK-4 can be used, the, wavelength can be extended below 1 mm.

• UV Follow-On: maximum pulse spacing increases to 440 ns; add UV down to below 250 nm (possible emittance limit); peak micropulse energy of 25 mJ at 350 nm. Improvements to the mirror coatings and the accelerator performance could bring the lower wavelength limit below 190 nm.

FEL users are already doing important experiments:

• Spectroscopy of H in Si (Luepke) - despite its importance and ubiquity, the behavior of H in Si has not been adequately characterized because suitable spectroscopic tools have been lacking, a situation the JLab FEL high average power uniquely overcomes. This fall's experiments yielded the first measurement of vibrational lifetime of isolated H in crystalline Si, and contributed to the understanding of annealing by showing strong coupling between H-associated modes and optical-mode lattice phonons.

• Pulsed Laser Deposition of Metals (Reilly) - the combination of high peak power, picosecond pulse length and high average power make the FEL an attractive tool for PLD, ultimately as a way to go beyond the limits of the existing excimer laser based technology. Though the present 55 ns maximum pulse to pulse spacing prevents fully accessing what the FEL can do, it was possible to make metal films with particulate counts apparently lower than excimer laser technology despite the latter's long development effort.

• Micromachining of Polyimde (Kelley) - precisely drilled polyimide films are widely used as printed wiring board dielectrics, ink jet printer heads and potentially as space sails. The FEL offers a unique opportunity to tune to strong absorbances and to use pulse lengths (10 ms) near the thermal diffusion transition. Percussion drilling experiments near to (5.85 mm) and away from (3.12 mm) the strongest absorption resonance attained partial or full penetration in a single macropulse, yielding a diameter less than about 30 mm at the smallest.

While these and other efforts are expected to continue, further exciting opportunities are now opening:

• Energy Flow in Proteins (Austin) - the exact position of the amide absorption and out-flow of vibrational excitation energy deposited into it, both depend on the detailed local structure of the protein. The protein's biological function depends on related energy flows. Based on previous experiments at FELIX, the JLab FEL's high-average power and excellent stability will combine to offer the signal-to-noise performance needed for high sensitivity at the needed wavelengths near 6 mm.

• "Spintronics" (Tolk et al.) - a novel semiconductor electronics based on spin rather than charge appears possible and capable of important advances, e.g., sharply increased memory density at reduced power input. The FEL's high average power and tunability enable the first round of experiments: band offset measurement at semiconductor interfaces, lifetime measurement of photo-induced, spin-polarized carriers, and (more broadly) study of electron-hole dynamics.

• UV Photobiology (Sutherland) - assessing the nature and extent of the human health risk arising from increased UV light reaching the earth requires uniform exposure of a statistically significant number of target organisms (e.g., animals) at levels relevant to chronic human exposures in the critical 290 nm - 400 nm wavelength range. There is simply no source in prospect other than the JLab UV FEL.

• Laser/Materials Interaction Fundamentals (Pate) - combining FEL and table-top laser based experiments gives a way to study events at a molecular level. The theme is to selectively deposit energy in a chose bond and then follow its fate with a probe laser or sequential multiphoton excitation. The most immediate practical benefit will be to indicate the range of opportunity to use multiphoton high peak power IR to achieve photochemistry requiring, e.g., UV if driven by single photons.

• Pulsed IR/X-RayExperiments (Boyce/Happek) - The IR beam can act as a pump to induce structural transformations in materials (e.g., amorphization, melting) that can be characterized after a controlled brief time interval by a x-ray pulse. Accordingly, the time course of rapid thermal processing in the picosecond regime can be studied directly. Initial hardware construction and demonstration experiments are planned.

• Laser Processing Applications for Automotive Fuel Components (Hamann) - Increasingly stringent automotive emission requirements drive fuel injector technology toward smaller, more precise orifices than can be made by established punching, EDM or drilling technology. Desirable next-generation orifices would be 50 - 200 mm diameter in 75 - 350 mm thick stainless steel, have straight walls with zero taper, and sharp entry/exit edges. To displace other laser technology, the FEL will need to deliver high power at 1 mm or preferably shorter, with a micropulse rate between 10 and 100 kHz.