Wayne A. McMullin

A high quality permanent-magnet wiggler for the Rocketdyne/Stanford infrared free electron laser

Abstract A high quality, variable gap, variable taper, permanent-magnet wiggler has been built for infrared free electron laser (FEL) experiments to be performed at the Stanford Photon Research Laboratory. The design and characterization procedure used to assemble the wiggler is discussed. A simulated annealing code was used to minimize field errors arising from variations in the individual magnets. The computed electron trajectories associated with the measured magnetic fields are presented for a range of different operating points of the wiggler. These plots indicate a very high quality field over a large range of different wiggler operating regimes. Resultant trajectory wander over the 2 m long wiggler for a 40 MeV electron at a wiggler gap corresponding to 3.3 kG was calculated to be less than 25 μm. The ability to control trajectory wander and optical phase slip using the simulated annealing code suggests future extensions to extremely long wigglers.

First operation of the Rocketdyne/Stanford free electron laser

Abstract A near infrared free electron laser (FEL) has been built and installed by Rocketdyne in the Stanford Photon Research Laboratory. The Rocketdyne/Stanford FEL utilizes a very high quality, 2 m long, permanent magnet planar wiggler whose gap may be continuously tuned, and magnetic field axially tapered by varying the gap at one end relative to the other. The laser is operated with an e-beam supplied by the Stanford Mark-III accelerator. A stable resonator with a broadband, dielectric coated element permits transmissive outcoupling over the 2.7–3.7 μm wavelength range. Results from initial operation of this laser are presented.

Initial results of operating the rocketdyne undulator in a tapered configuration

Abstract The near-infrared Rocketdyne/Stanford free electron laser (FEL) uses a very-high-quality precision undulator whose field strength and field taper are adjustable. The Rocketdyne undulator has been operated in both an amplifier configuration, as in the master-oscillator power amplifier (MOPA) experiments, and an oscillator configuration, as in the photocathode and tapered-undulator experiments. The tapered-undulator experiment was performed at the Stanford Photon Research Laboratory (SPRL) using an electron beam supplied by the Mark III rf-linac. During the experiment we observed sustained oscillations as the undulator magnetic-field taper was continuously tuned from 0% to 10%. We observed ∼1.2% extraction efficiency for a magnetic-field taper of 9.6%. During the same experiment we observed sustained oscillations as the undulator gap was continuously varied over 120 mil. Details of the experiment are presented.

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.

Initial results from the free-electron-laser master oscillator/power amplifier experiment

Abstract We describe the first master oscillator/power amplifier experiment in which both the master oscillator and power amplifier are free-electron-laser devices driven by time-sharing an electron beam from a single radiofrequency linear accelerator. The optimized, small-signal gain spectrum realized in the untapered power amplifier is presented. Up to 60% gain was observed at 3 μ with an estimated peak current of 35 A. Additional Q -switched experiments are also discussed.

Design and characterization of a high quality, variable taper samarium cobalt undulator

Abstract A very high quality, planar undulator with continuously variable gap and magnetic field taper has been designed and built for near-infrared free-electron laser experiments. The design, assembly and results of the first application of a simulated annealing technique for electron trajectory optimization of this all samarium cobalt undulator are described.