L.M. Young

Results of the Los Alamos free-electron laser experiment

A free-electron laser (FEL) amplifier experiment to test the performance of a tapered wiggler at high optical power has been successfully completed. A well-separated two-component electron energy distribution has been obtained that is characteristic of a tapered wiggler. Energy distribution spectra and extraction efficiencies have been measured as a function of initial electron energy, energy spread, emittance, optical power, and spatial and temporal misalignments of the laser and electron beams. A maximum efficiency of ∼ 4 percent was measured, and good agreement of efficiency with a one-dimensional theory was obtained.

POISSON/SUPERFISH on PC compatibles

We have adapted the POISSON/SUPERFISH codes to run on 486 or 386 PCs. The PC version includes features not found in the standard version, including programs for automatically tuning RFQ, DTL, and CCL cavities; a complex version of the RF field solver; memory allocation for temporary data; many line regions for dividing the mesh into fine or coarse sections; full support for multiple-cell DTL cavities; plotting of resonance-search and transit-time data; and on-line documentation. We modified AUTOMESH to generate self-consistent logical and physical coordinates. This new, more robust code greatly reduces the number of crashes in LATTICE caused by ill-formed mesh triangles along boundaries. The codes solve arbitrarily large problems. Each program allows free-format entry of CON array elements, and provides error checking of user entries. Standard release 4 now uses our root finder and convergence criteria.<<ETX>>

Experimental results from the Los Alamos FEL photoinjector

The authors report some initial measurements of electron beam properties from the new photoinjector installed as the front end on the Los Alamos free-electron laser (FEL). The FEL is being rebuilt with the photoinjector, added acceleration to 40 MeV, new diagnostics, and a beam line designed to minimize emittance growth. The authors measured the spatial and temporal properties of the beam at energies of about 15 MeV as a function of several parameters and the results have been compared to simulations. The operational characteristics of the important elements of the system and the theoretical comparisons are described. >

Recent results from the Los Alamos free-electron laser

In this paper, we review the most recent experimental results of the Los Alamos free-electron laser program. Three major efforts will be described: lasing at improved efficiency over that previously attained, electron beam improvement, and energy recovery. An extraction efficiency of 2 percent was achieved with a wiggler having a 12 percent wavelength taper. The beam has been improved so that limits to its quality are now caused, not by injector performance, but by wake fields related to the high peak currents achieved. Limits to optical power are set by mirror damage. Experiments are described that demonstrate the successful operation of an energy-recovery system.

The accelerator for the Los Alamos free-electron laser - IV

The design parameters and performance of the accelerator used with the Los Alamos free-electron laser are described. Special emphasis is placed on those features of the accelerator that affect emittance, energy spread, and micropulse temporal shape.

Progress Report on the NBS/LOS Alamos RTM

The NBS-Los Alamos 200 MeV Racetrack Microtron (RTM) is being built under a program aimed at developing the technology needed for high-current intermediateenergy CW electron accelerators. In this report we give an overview of the present status of the project. Recent progress includes: (1) completion of testing of the 100 keV chopper-buncher system demonstrating a normalized emittance well under the design goal of 2.6 ¿ mm mrad at currents exceeding the design goal of 600 ¿A; (2) operation of the rf structures comprising the 5 MeV injector linac at power levels up to 50 kW/m, resulting in an accelerating gradient at ß=1 of 2 MV/m (compared to a design goal of 1.5 MV/m). The measured shunt impedance is 82.5 Mn/m; (3) construction and installation of the 30 ton end magnets of the RTM. Field mapping of one magnet has been completed and its uniformity exceeds the design goal of ±2 parts in 104; (4) performance tests (with beam) of prototype rf beam monitors which measure current, relative phase, and beam position in both transverse planes. (5) Installation and initial operation of the primary control system.

Design and analysis of experimental performance of the Los Alamos HIBAF facility accelerator using the INEX computer model

The authors review the accelerator design of the high brightness accelerator free electron laser (FEL) (HIBAF) at Los Alamos National laboratory and analyze its performance. HIBAF is the first high-brightness high-current (several hundred amperes) accelerator build using a photoelectric injector. The authors discuss the design philosophy and the integrated numerical experiment (INEX) design tool, and describe the accelerator components. Currently, the machine has only been operated at intermediate energies near 15 MeV. The INEX computer code package is used to examine the accelerator performance by comparing the measurements with simulations at that energy. The accelerator should be able to reach the design goal of 300 A current with the normalized 90% transverse emittance of less than 50 pi mm mrad for a 5-nC bunch after reaching the final energy of 40 MeV. >

Physics design of the high brightness linac for the advanced free-electron laser initiative at Los Alamos

This paper describes the design of an accelerator that can produce beams of greater than 1 {times} 10{sup 13} A/m{sup 2} (brightness = 2*I/{var epsilon}{sup 2}, where {var epsilon} is the rms emittance). The beam emittance growth in the accelerator is minimized by: producing a short-electron bunch in a high-gradient rf cavity, using a focusing solenoid to correct the emittance growth caused by space charge, and designing the coupling slots between accelerator cavities to minimize quadrupole effects. The results from simulations are, at 2.3 nC, a peak current of 180 A and an emittance of 1.6 {pi} mm-mrad, and, at 4.6 nC a peak current of 300 A and an emittance of 2.4 {pi} mm-mrad. The exit energy from the linac is 20 MeV for both cases.

Simulations of the LEDA RFQ 6.7-MeV accelerator

The codes PARMTEQM and RFQTRAK simulate the beam transport through the radio-frequency-quadrupole (RFQ) accelerator for the low-energy-demonstration accelerator (LEDA). They predict 95% transmission for a matched 110-mA proton beam with a normalized-RMS emittance of 0.02 mm mrad. RFQTRAK simulates the effects of arbitrary vane-tip misalignments. This RFQ includes some new features in its design. It consists of four resonantly coupled 2-m-long segments that make up its 8-m length. It has higher vane-gap voltages at the high-energy end than the low-energy end. The entrance end of the RFQ has lower transverse focusing strength to facilitate beam matching. The exit of the RFQ has a transition cell and a radial-matching section. The exit radial-matching section matches the beam into the following accelerator.

Los Alamos advanced free-electron laser

Abstract Los Alamos researchers are building a free-electron laser (FEL) for industrial, medical, and research applications. This FEL, which will incorporate many of the new technologies developed over the last decade, will be compact, robust, and user-friendly. Electrons produced by a photocathode will be accelerated to 20 MeV by a high-brightness accelerator and transported by permanent-magnet quadrupoles and dipoles. The resulting electron beam will have an excellent instantaneous beam quality of 10πmm mrad in transverse emittance and 0.3% in energy spread at a peak current up to 300 A. Including operation at higher harmonics, the laser wavelength extends from 3.7 μm to 0.4 μm.