Robert J. Burke

First demonstration of a free-electron laser driven by electrons from a laser-irradiated photocathode

We report the results from the first operation of a free electron laser (FEL) driven by an electron beam from a laser-irradiated photocathode. The Rocketdyne/Stanford FEL achieved sustained oscillations, lasting in excess of three hours, driven by photoelectrons accelerated by the Stanford Mark III radiofrequency linac. A LaB6 cathode, irradiated by a tripled Nd: Yag mode-locked drive laser was the source of photoelectrons. The drive laser, operating at 95.2 MHz, was phase-locked to the 30th subharmonic of the S-band linac. Peak currents in excess of 125 A were observed and delivered to the Rocketdyne 2 m undulator which was operated as a stand-alone oscillator. Sustainable small-signal gain of 100% per pass was observed over a 2 h time period with periodic observation of small-signal gain as high as 150% per pass. Preliminary estimates of the electron-beam brightness deliverable to the undulator range from 3.5 × 1011 to 5.0 × 1011 A/(rad m)2.

High-performance pure permanent-magnet undulators

Abstract Pure permanent-magnet (PM) undulator designs that can match or exceed the on-axis field of PM hybrids are presented. Linearity and superposition of fields allows us to construct undulators with optimized performance for both FEL and synchrotron-radiation applications. Examples and performance data are given.

Simulations of the Rocketdyne free-electron laser with a 4 m wiggler

Abstract Rocketdyne is assembling a high-brightness 78 MeV FEL. After full development the laser will be capable of an average output of greater than 1 kW. Performance calculations using the Rocketdyne FELOPT code are presented for a 1.06 μm system.

Rocketdyne FEL for power beaming using a regenerative amplifier

The Rocketdyne free-electron laser (FEL) being presently developed for operation in the visible to one-micron regime is described, with particular attention given to some of the principal optics and atmospheric propagation issues. The paper describes the system assembly and discusses the performance requirements for power beaming, the resonator design, and the basic ideas and calculations involved in the beam propagating through the atmosphere and tilt corrections. This FEL will be capable of an average output of greater than 1 kW in the near infrared. The laser system has an ability of scaling to power levels required for beaming power to space platforms.

An accelerator based steady state neutron source

Abstract Using high current, cw linear accelerator technology, a spallation neutron source can achieve much higher average intensities than existing or proposed pulsed spallation sources. With about 100 mA of 300 MeV protons or deuterons, the accelerator based neutron research facility (ABNR) would initially achieve the 10 16 n/cm 2 s thermal flux goal of the advanced steady state neutron source, and upgrading could provide higher steady state fluxes. The relatively low ion energy compared to other spallation sources has an important impact on R&D requirements as well as capital cost, for which a range of

Power beaming with FEL lasers

300–450M is estimated by comparison to other accelerator-based neutron source facilities. The source is similar to a reactor source in most respects. It has some higher energy neutrons but fewer gamma rays, and the moderator region is free of many of the design constraints of a reactor, which helps to implement sources for various neutron energy spectra, many beam tubes, etc. With the development of a multibeam concept and the basis for currents greater than 100 mA that is assumed in the R&D plan, the ABNR would serve many additional uses, such as fusion materials development, production of proton-rich isotopes, and other energy and defense program needs.

Regenerative ultraviolet driven photocathode

FEL power beaming has broad application to space operations. The Rocketdyne Division of Rockwell International Corporation has examined the commercial applications of beamed power from Earth to space using the Radio Frequency LINAC Free Electron Laser (RF FEL) and has determined that there is a substantial addressable market. Rocketdynes experience in developing and demonstrating FEL technologies, optics and atmospheric compensation and advanced power and power distribution systems ideally positions the Division to conduct the initial demonstration to prove the feasibility of using a FEL to beam power to space platforms.