JLab FEL User Meeting and

Laser Processing Consortium Workshop

January 17-18, 2002

Jefferson Lab

The first phase of the Jefferson Lab FEL program, the IR Demo, is now complete, having delivered a total of 2600 hours of user beamtime in the course of 8 months of running that began in October 1999. The IR Demo initiated a new generation of FEL’s, incorporating for the first time critical fundamental advances: superconducting RF accelerator technology and same-cell energy recovery from the spent electron beam, enabling average output power to exceed the previous FEL record by a factor of more than 100. Further, the IR Demo lased at harmonics of the main frequency with record-setting power and delivered tens of watts in the terahertz range, the latter roughly 4 orders of magnitude more than its predecessors. All performance specifications were met or exceeded. A more solid basis for the development of future FEL’s can hardly be imagined. The user procedures functioned successfully beamtime assignment, safety in experimentation, and operations. They will continue to be refined.

The IR ugrade phase now under construction will deliver more than: 10 kW average power, 100 mJ/pulse, 1.5 to 15 mm wavelength, 0.2 – 2 ps pulse length, and 4.68 MHz to 74.85 MHz repetition rate. A further power upgrade based on cryogenically-cooled cavity mirrors is funded and a proposal for increasing power to beyond 100 kW is in preparation. UV light from a separate, dedicated wiggler is expected about a year after the IR upgrade starts up. The major output characteristics will be: 0.25 – 1 mm wavelength, more than 25 mJ/pulse and more than 1 kW average output power. The desire of users for shorter wavelengths and more power has been clearly communicated; the chief issue is absorption by the optical cavity mirrors. Plans also include a beamline for THz radiation, a beamline for Compton femtosecond x-rays and operation of the Helios compact synchrotron.

Results from using the FEL for basic research this year include:

The applied science program strives to translate science into technology, and technology into applications that are ultimately deployed into manufacturing. One family of promising candidates is based on ablation – micromachining (drilling), specialized coatings, and production of single-walled carbon nanotubes. A second is based on rapid thermal processing – metal surface glazing, polymer surface amorphization. Earlier, we determined that the native FEL beam, even after the upgrade, does not offer the best parameter range for ablation studies. We therefore sought funding to achieve it by downstream beam conditioning equipment and (since the January meeting) we are successful.

Highlights of applied research results include:

As always, continuing progress depends on a continuing flow of funds into the program. The FEL leadership team is hard at work. Progress also depends on users obtaining and communicating important results. A vigorous user effort during the shutdown to prepare new experiments is critical. Users are urged most strongly to exert themselves accordingly.