Groundwater Resources in the Saline Valley Conservancy District, Saline and Gallatin Counties, Illinois

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Low energy operation of the DIAMOND light source

Abstract Within the last decade storage ring free-electron lasers (SRFELs) have reached UV output wavelengths and beyond: several facilities have achieved down to 250nm and quite recently below 200nm. The design of DIAMOND, the third-generation replacement for the existing SRS light source at Daresbury Laboratory, has been optimised at 3 GeV to provide high quality output for the scientific community, mainly from a range of insertion devices. In this paper we propose an additional DIAMOND regime at 1-1.5 GeV in an attempt also to include an SRFEL which would be of major benefit to users needing high quality, high brightness UV/VUV radiation. Such variable ring operating energy will have significant implications, not least in achieving acceptable beam lifetimes. In addition, enhanced beam coherent instabilities (notably microwave) at low energy will affect the single bunch length (peak current) and energy spread which will in turn limit the achievable FEL gain. All these factors will have to be assessed in the detailed design stages of DIAMOND. DIAMOND LIGHT SOURCE The recent successful demonstration of an SRFEL on the ELETTRA light source [1], together with earlier experience at LURE (Super-ACO) and elsewhere, has encouraged interest in the incorporation of such advanced facilities in all leading light sources. The normal operating mode of DIAMOND at 3GeV is described in detail elsewhere FEL OPERATING MODE When operating in optimised FEL mode, the storage ring will be populated with bunches spaced apart in time by twice the round trip time in the FEL cavity, ensuring energy transfer occurs as frequently as possible; the cavity length is always chosen to be a sub-harmonic of the storage ring circumference, whilst satisfying other, practical constraints. The final circumference of the DIAMOND storage ring has not yet been fixed but may be finalised at 528 m (an increase on the present 489 m layout [2] to budget for additional elements), giving a harmonic number of 880 at 500 MHz RF frequency. With 8 equally spaced bunches this leads to a required cavity length of 33 m, which is reasonable (cf. the ELETTRA device which has a cavity length of 32.4 m [1]). Since a very small vertical emittance is not necessary for FEL operation, a conservative coupling value of 3% has been assumed for these calculations, which should both be readily achievable and provide a satisfactory Touschek lifetime; both greater coupling and larger emittance could be selected if necessary. The momentum acceptance will be the primary limit on the beam lifetime at low energies, via Touschek scattering and quantum lifetime; the 4% dynamic and physical acceptance limit specified for 3 GeV operation BUNCH MODELLING To provide peak currents of tens of Amperes, as will be needed for useful FEL gains, bunch currents of several milliamperes are required. At these currents the effects of bunch lengthening from potential well distortion (PWD) and from the microwave instability (MI) are large, but are beneficial in that they provide low enough number densities within the bunches to give an acceptable Touschek lifetime; however the issue is whether sufficient peak current can then be maintained, together with acceptable energy spread. The ZAP code [3] was used to predict the effect on bunch parameters of PWD and MI (details are given in [4]); however, the implementation of Brück's approximatio

Advances in induction-heated plasma torch technology

Continuing research has resulted in significant advances in induction-heated plasma torch technology which extend and enhance its potential for broad range of uses in chemical processing, materials development and testing, and development of large illumination sources. Summaries of these advances are briefly described

Seeded gas thrusters and related system components

A program involved with the construction and test of a number of laser heated thrusters is described. These thrusters, with a cavity approximately 23 cm long and 3.5 cm in i.d., are to be tested by NASA at a later date with a laser beam focused through the throat to heat hydrogen propellant containing an opacifier. The heated propellant exhausts through a supersonic nozzle with a 0.6 cm throat at 3000 C. Thrust stands and control systems were furnished with the thrusters. The report describes radio frequency plasma heated hot and cold flow simulation tests by the contractor

Induction plasma nozzle tests

Simulation of nozzle environment in gas core nuclear rocket with induction coupled arc plasma syste

Inducing strong density modulation with small energy dispersion in particle beams and the harmonic amplifier free electron laser

We present a possible method of inducing a periodic density modulation in a particle beam with little increase in the energy dispersion of the particles. The flow of particles in phase space does not obey Liouville's Theorem. The method relies upon the Kuramoto-like model of collective synchronism found in free electron generators of radiation, such as Cyclotron Resonance Masers and the Free Electron Laser. For the case of an FEL interaction, electrons initially begin to bunch and emit radiation energy with a correlated energy dispersion which is periodic with the FEL ponderomotive potential. The relative phase between potential and particles is then changed by approximately 180 degrees. The particles continue to bunch, however, there is now a correlated re-absorption of energy from the field. We show that, by repeating this relative phase change many times, a significant density modulation of the particles may be achieved with only relatively small energy dispersion. A similar method of repeated relative electron/radiation phase changes is used to demonstrate supression of the fundamental growth in a high gain FEL so that the FEL lases at the harmonic only

An interactive graphics package for the automatic node renumbering of finite element matrices

An interactive graphics software package which allows users to display the non-zero structure of large sparse symmetric materials was described and methods used to implement it as a portable FORTRAN callable subroutine were summarized. In particular, the system permits the display of the resulting matrix after reordering the rows and columns, with the reordering scheme either defined by the user or automatically generated by the program with the aim of reducing matrix bandwidth and profile. Although the primary application of the package has been to the finite element analysis of structures, it is equally well suited to the many other areas of engineering and science which use sparse matrices