The 10-pm Los Alamos free-electron laser (FEL) facility is being upgraded. The conventional electron gun and bunchers have been replaced with a much more compact 6-MeV photoinjector accelerator. By adding existing parts from previous experiments, the primary beam energy will be doubled to 40 MeV. With the existing 1-mS wiggler (Xv, 2.7 cm) and resonator, the facility can produce photons with wavelengths from 3 to 10 im when lasing on the fundamental mode and produce photons in the visible spectrum with short period wigglers or harmonic operation. After installation of a 150° bend, a second wiggler will be added as an amplifier. The installation of laser transport tubes between the accelerator vault and an upstairs laboratory will provide experimenters with a radiation free environment for experiments. At the time of writing (Jan. 1990), the injector plus one additional tank has been installed and tested with beam to an energy of 17 MeV.
A free-electron laser facility (FEL) is being constructed at the National
Institute of Standards and Technology (NIST) in collaboration with the Naval
Research Laboratory (NRL) . The FEL will be driven by the electron beam from the
NIST racetrack microtron (RTM). The anticipated performance of the FEL is: (1)
wavelength variability from 200 run to 10 tim; (2) continuous train of 3-ps pulses at
66 MHz; and (3) average power of 10 W to 200 W. This excellent performance will be
achieved primarily because of the unique characteristics of the RTM. This
accelerator will provide a continuously pulsed electron beam with high brightness
and low energy spread at energies from 17 MeV to 185 MeV. For FEL operation high
peak current is required and a new injector for this purpose has been designed. The
undulator for the project is 3.64-m long with 130 periods and a peak field of 0.54
T. The construction of the undulator is nearly complete and delivery is expected
shortly. The 9-m optical cavity has been designed and is under construction. An
experimental area is being prepared for FEL users which will have up to six
stations. Initial operation of the FEL is scheduled for 1991. The NIST-NRL FEL
will provide a powerful, tunable light source for research in biomedicine, materials
science , physics , and chemistry.
The paper concentrates on possible applications of plasmas to FELs and closely related radiation sources. The possibility of using intense longitudinal plasma oscillations as wigglers for FELs is assessed, and three methods of generating intense plasma waves are presented: one utilizes two intense laser beams of different frequencies, the other employs shining a laser on a plasma with a resonance layer, and the third uses the wake fields of charged bunches from a linear accelerator. It is also demonstrated that by using plasma beat-wave or plasma wake-field accelerators, bunches as short as a few microns can be produced. The possibility of matching the group velocity of the EM wave to the electron velocity is considered, and cyclotron autoresonance masers and ion-channel lasers are covered.
The feasibility of using relativistically moving plasma waves as short wavelength undulators for possible free-electron laser (FEL) and Compton scattering applications is considered. Focus is placed on the spontaneous emission emitted by a single electron bunch as it traverses a plasma wave wiggler. The basic characteristics of the radiation from such a wiggler are discussed, and attention is given to the wave-particle interaction physics. The electron trajectories in the plasma wave wiggler are simulated using a three-dimensional model which includes emittance effects, and the resulting radiation pattern produced by the electrons is calculated. The scattered-electron energies and spatial distributions are analyzed.
We are developing computer codes for the numerical simulations of relativistic klystrons and relativistic klystron
"afterburners". The purpose of this note is to discuss the main features of our numerical model.
The quantum-kinetic equation for free-electron lasing in a longitudinal electric wiggler is expressed by two methods: a method expanding the momentum distribution function up to the second order and the transition probability up to the next order in h/2pi in the Taylor series forms and a method utilizing only the first-order derivative of the momentum distribution function and the lowest order in 'h' of the transition probability by means of the corresponding principle, the momentum and energy-conservation laws, and the time-reversal invariance of the transition probability. The gain of a free-electron laser using a longitudinal electric wiggler is determined, and emphasis is placed on the single-pass gain with consideration of the increase in the momentum spread.
A set of self-consistently nonlinear and coupled equations in three dimensions, describing the evolutions of both radiation field and electrons is obtained. In the model utilized in the analysis, a relativistic electron beam with an arbitrary radial profile is injected into the interactional region of an amplifier. Focus is placed on the effects of the wiggler field amplitude and a dc magnetic-field amplitude, electron beam, and input-signal power. Experimental results show increases in efficiency up to 9 percent, and it is noted that higher efficiency rates are possible.
Millimeter wave power may be the ideal source of heat for a plasma, but
advances in technology are needed to meet requirements of next generation
fusion devices. Free electron lasers (FEL) are one candidate for such sources,
and this paper reviews the progress, issues of physics and technology, and
potential benefits for fusion from these devices.
We review the technical advantages offered by x-ray holographic microscopy for imaging
the structure of living biological specimens. We discuss the wavelength, coherence, energy,
and pulse-length requirements and conclude that these could be met by free-electron laser
architectures of the near future. We also show that Fourier-transform holography using a
reference scattering sphere is the best optical configuration for a practical instrument.
Future ti-linac-driven FELs, operating in the range from 4 nm to 100 nm, could be excellent exposure
tools for extending the resolution limit of projection optical lithography to □O.1 m and with adequate total
depth of focus (1 to 2 Rm). When operated at a moderate duty rate of □1%, XUV EELs should be able to
supply sufficient average power to support high-volume chip production. Recent developments of the
electron beam, magnetic undulator, and resonator mirrors are described which raise our expectation that FEL
operation below 1 00 nm is almost ready for demonstration. Included as a supplement is a review of initial
design studies of the reflecting XUV projection optics, fabrication of reflection masks, characterization of
photoresists, and the first experimental demonstrations of the capability of projection lithography with 14-nm
radiation to produce lines and spaces as small as 0.05 m.
Within the last several years a number of meetings and conferences have addressed the
unique scientific opportunities which would result from the development of an RF-linac FEL user
facilty accessing the XUV and mid-JR spectral regions. The capabilities of a number of linear
and nonlinear spectroscopies would be enhanced by one or more features of the FEL output, e.g.,
its free tunability in these regions, transform-limited linewidth, high peak power and brightness,
time structure, and the possibility of multi-color pump-probe experiments utilizing the coordinated
output from more than one FEL oscillator. These advances would in turn benefit a variety
of scientific areas. In the realm of basic science, experiments or measurements which either require
an FEL or where increased sensitivity would be advantangeous can be found in quantum,
atomic, cluster, molecular, and condensed matter physics, magnetic materials, surface science and
catalysis, non-linear spectroscopy, and biophysics and -chemistry. Potential technological applications
at such a facility include analytical chemistry and physics, advanced fabrication processes,
medical applications, and others. These applications form the basis for the specifications of the
FEL and for the design of the laboratories for the proposed FEL user facility at Los Alamos.
The IRFEL is a useful infrared light source that can be
employed as a probe of vibrational dynamics on surfaces. This
paper will discuss the application of the IRFEL to desorb
adsorbates from surfaces by resonantly exciting their vibrational
modes. This application is illustrated by recent investigations
of the resonant desorption of butane from Al2O(1120) using the
Mark III IRFEL. These resonant desorption studies revealed a
greater desorption yield for the asymmetric C-H stretches in
comparison with the symmetric C-H stretches. This greeter
desorption efficiency for the asymmetric C-H stretches was
attributed to the orientation of the butane molecules in an
ordered adlayer on A1203 (1120).
The interest in Free electron Laser is due to: its large wavelength range,
which at present extends from about one centimeter to 0.24 micrometer; its tunability;
its high peak power"2 This point is illustrated in Fig. 1, which cornpares
the FELs and other radiation sources: microwaves tubes, lasers, undulators
in high brightness synchrotron radiation storage rings, plasma based X-ray lasers
at Livermore and Princeton. The FEL performance level is partly based on experirnental
data, and partly extrapolated from our present knowledge of the physics
and technology of this system. This second case applies in particular to the far
TJv and soft X-ray region. One can see that there are two main regions of interest
for FELs applications, where they can be superior to other sources: one in the IR
and millimeter to centimeter region; the second in the short wavelength region,
below 0.1 micrometer. In this paper we will discuss the present status of the
research to produce a FEL in the short wavelength region, and the characteristics
and performance of such a system.
The physical mechanisms that contribute to harmonic radiation in free-electron laser systems are examined.
Mathematical models for the spontaneous and coherent-spontaneous emission in plane-polarized
wigglers are given. How these models are used to perform numerical simulations is discussed. Modifications
of the models to incorporate non-ideal free-electron laser effects are reviewed.