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

published or submitted for publicationis peer reviewedOpe

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

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

A Color-Magnitude Diagram for a Globular Cluster In the Giant Elliptical Galaxy NGC 5128

The Hubble Space Telescope has been used to obtain WFPC2 (V,I) photometry for a large sample of stars in the outer halo of the giant elliptical NGC 5128 (d = 4 Mpc). The globular cluster N5128-C44, at the center of the Planetary Camera field, is well enough resolved to permit the construction of a color-magnitude diagram (CMD) for it which covers the brightest two magnitudes of the giant branch. The CMD is consistent with that of a normal old, moderately low-metallicity ([Fe/H] = -1.30 globular cluster, distinctly more metal-poor than most of the field halo stars at the same projected location (which average [Fe/H] ~ -0.5). This is the most distant globular cluster in which direct color-magnitude photometry has been achieved to date, and the first one belonging to a giant E galaxy.Comment: 12 pages, LaTeX, including 5 postscript figures; submitted to Astronomical Journa

Results of aircraft open-loop tests of an experimental magnetic leader cable system for guidance during roll-out and turnoff

An experimental magnetic leader cable (MLC) system designed to measure aircraft lateral displacement from centerline and heading relative to centerline during rollout, turnoff, and taxi was tested at NASA's Wallops Flight Facility using NASA's Transport System Research Vehicle (TSRV), a modified B-737. The MLC system consisted of ground equipment that produced a magnetic field about a wire along runway centerline and airborne equipment that detected the strength and direction of this field and computed displacement and heading. Results of these tests indicate that estimates of aircraft displacement from centerline produced by the magnetic leader cable system using either of the two algorithms appear to be adequate for use by an automatic control system during rollout, turnoff, and taxi. Estimates of heading, however, are not sufficiently accurate for use, probably because of distortion of the magnetic field by the metal aircraft

Wave spectra of a shoaling wave field: A comparison of experimental and simulated results

Wave profile measurements made from an aircraft crossing the North Carolina continental shelf after passage of Tropical Storm Amy in 1975 are used to compute a series of wave energy spectra for comparison with simulated spectra. Results indicate that the observed wave field experiences refraction and shoaling effects causing statistically significant changes in the spectral density levels. A modeling technique is used to simulate the spectral density levels. Total energy levels of the simulated spectra are within 20 percent of those of the observed wave field. The results represent a successful attempt to theoretically simulate, at oceanic scales, the decay of a wave field which contains significant wave energies from deepwater through shoaling conditions

Minimal-resource computer program for automatic generation of ocean wave ray or crest diagrams in shoaling waters

A computer program for studying linear ocean wave refraction is described. The program features random-access modular bathymetry data storage. Three bottom topography approximation techniques are available in the program which provide varying degrees of bathymetry data smoothing. Refraction diagrams are generated automatically and can be displayed graphically in three forms: Ray patterns with specified uniform deepwater ray density, ray patterns with controlled nearshore ray density, or crest patterns constructed by using a cubic polynomial to approximate crest segments between adjacent rays

SAGE III aerosol extinction validation in the Arctic winter: comparisons with SAGE II and POAM III

The use of SAGE III multiwavelength aerosol extinction coefficient measurements to infer PSC type is contingent on the robustness of both the extinction magnitude and its spectral variation. Past validation with SAGE II and other similar measurements has shown that the SAGE III extinction coefficient measurements are reliable though the comparisons have been greatly weighted toward measurements made at mid-latitudes. Some aerosol comparisons made in the Arctic winter as a part of SOLVE II suggested that SAGE III values, particularly at longer wavelengths, are too small with the implication that both the magnitude and the wavelength dependence are not reliable. Comparisons with POAM III have also suggested a similar discrepancy. Herein, we use SAGE II data as a common standard for comparison of SAGE III and POAM III measurements in the Arctic winters of 2002/2003 through 2004/2005. During the winter, SAGE II measurements are made infrequently at the same latitudes as these instruments. We have mitigated this problem through the use of potential vorticity as a spatial coordinate and thus greatly increased of the number of coincident events. We find that SAGE II and III extinction coefficient measurements show a high degree of compatibility at both 1020 nm and 450 nm except a 10–20% bias at both wavelengths. In addition, the 452 to 1020 nm extinction ratio shows a consistent bias of ~30% throughout the lower stratosphere. We also find that SAGE II and POAM III are on average consistent though the comparisons show a much higher variability and larger bias than SAGE II/III comparisons. In addition, we find that SAGE II and POAM III data sets are not well correlated at and below 18 km. Overall, we find both the extinction values and the spectral dependence from SAGE III are robust and we find no evidence of a significant defect within the Arctic vortex