Richard A. Hartley

Design and operation of the Compact Infrared Free-Electron Laser (CIRFEL)

The Compact Infrared Free Electron Laser (CIRFEL) was built as part of a joint collaboration between Northrop Grumman and Princeton University to develop FELs for use by researchers in the materials, medical and physical sciences. The CIRFEL was designed to laser in the Mid-IR and Far-IR regimes with picosecond pulses, megawatt level peak powers and an average power of a few watts. The CIRFEL utilizes an RF photocathode gun to produce high-brightness time synchronized electron bunches. The micropulse separation is 7 nsec which allows a number of relaxation phenomena to be observed. In addition, the photocathode illumination laser can be used in combination with the FEL IR light for pump- probe experiments. The CIRFEL is presently being commissioned and working towards lasing. The present status of the machine is presented.

FIRST LASING OF THE COMPACT INFRARED FREE-ELECTRON LASER

Abstract On 15 May 1996, lasing was achieved at the Compact Infrared Free-Electron Laser (CIRFEL) at 14 μm. The electron beam energy was 11.2 MeV and the micropulse charge was 1 nC. The width of the detuning curve was approximately 50 μm. Since achieving this milestone, we have lased repeatedly from 12.5 to 20 μm with between 0.25 and 1.5 nC of charge. Saturation is typically reached in less than 1.5 μs. The measured FEL spectrum is Gaussian in shape with a line width of 56 nm at 13 μm. Assuming a transform limited pulse, this corresponds to an FEL light pulse of 4.4 ps. The CIRFEL is a photocathode based free-electron laser with a micropulse width of 4–10 ps and a micropulse separation of 7 ns. The macropulse length is between 4 and 6 μs and the repetition rate is between 1 and 5 Hz. We present details of the CIRFEL machine as well as experimental measurements of the FEL radiation.

Beam diagnostics and modeling in CIRFEL

Abstract In this paper results of phase stability measurements of the photocathode drive laser at different points in the drive laser system, as well as the electron current micro-pulse phase stability measurements results are reported. Summary results of CIRFEL bend modeling and emittance measurements are also described. Result of a 5th order perturbation model for wiggler focusing is also reported.

The Northrop Grumman Compact Infrared FEL (CIRFEL)

As part of Northrop Grummans ongoing research in particle accelerators, we have designed and are commissioning a Compact Infrared Free-Electron Laser (CIRFEL) for the study of high-brightness electron beams and free-electron lasers. Besides serving as a tool for FEL development, the CIRFEL laboratory, located at Princeton University, will be used in experiments ranging from basic FEL physics and biophysics to chemistry, materials science and medicine. The CIRFEL is to lase initially in the 10 - 20 /spl mu/m range. The pulse format of this FEL is a train of micropulses, 5 - 10 psec is duration, at a repetition rate of 142.8 MHz. The micropulse energy is in excess of 100 /spl mu/J. The micropulses comprise a macropulse lasting approximately 10 /spl mu/sec. The macropulse repetition rate is 10 Hz, thus the average power of the FEL is on the order of 1.5 W.

Electron transport and emittance diagnostics in CIRFEL

Electron pulses for the Northrop Grumman Compact Free Electron Laser CIRFEL are produced at a repetition rate of up to 10 Hz by the illumination of a Mg photocathode with a photon injector 261 nm seed laser system mode locked to the 20th sub-harmonic of 2.856 GHz. Presently the system is being operated in the 10 to 12 MeV energy range and spontaneous radiation has been observed. We present some preliminary results on electron beam characterization including its energy spread, energy stability, and spontaneous radiation observations.

Design and construction of a Compact Infrared Free Electron Laser CIRFEL

The 5-15 micron Grumman Compact Infra Red Free Electron Laser CIRFEL which will produce extremely short pulses of tunable radiation under construction is described. Electron pulses are produced at a repetition rate of up to 10 Hz by the illumination of a single crystal <001> LaB/sub 6/ photocathode with a photon injector, a 6-10 psec, 349 nm (frequency tripled Nd-YLF) laser mode locked to the 20th subharmonic of 2856 MHz. Photoelectrons are further accelerated and guided to the superconducting microwiggler by a robust beam transport system through an achromatic bend. The /spl sim/10 MeV electrons interact with the optical radiation inside a near symmetric laser cavity. The FEL output will be coupled out through a hole in one of the cavity mirrors. The CIRFEL system is expected to be delivered in 1994.<<ETX>>