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Beam energy absolute measurement using K-edge absorption spectrometers

Description: A method is presented of absolute energy measurement with an accuracy of {triangle}{Epsilon} {approximately} 10{sup {minus}4}{Epsilon}{sub o} by direct measurement of the bend angle in a high-precision magnetic dipole using two opposite-direction short (about 2 mm long) high-field-intensity magnets ({bar {Beta}} {sub dipole} {much_lt} {Beta}{sub short mag}) installed at each end and two K-edge absorption spectrometers. Using these spectrometers and the hard x-ray synchrotron radiation created by the short magnets, a bend angle of 4.5 arc deg for the CEBAF energy bandwidth can be measured with an accuracy of a few units of 10{sup {minus}6} rad, and the main sources of systematic errors are the absolute measurement of the field integral and the determination of the centroid of the synchrotron beam at a wavelength equal to the K-edge absorption of the chosen substance.
Date: May 1, 1994
Creator: Karabekov, I.P. & Neil, G.
Partner: UNT Libraries Government Documents Department

Amplitude and phase beam characterization using a two-dimensional wavefront sensor

Description: We have developed a two-dimensional Shack-Hartman wavefront sensor that uses binary optic lenslet arrays to directly measure the wavefront slope (phase gradient) and amplitude of the laser beam. This sensor uses an array of lenslets that dissects the beam into a number of samples. The focal spot location of each of these lenslets (measured by a CCD camera) is related to the incoming wavefront slope over the lenslet. By integrating these measurements over the laser aperture, the wavefront or phase distribution can be determined. Since the power focused by each lenslet is also easily determined, this allows a complete measurement of the intensity and phase distribution of the laser beam. Furthermore, all the information is obtained in a single measurement. Knowing the complete scalar field of the beam allows the detailed prediction of the actual beam`s characteristics along its propagation path. In particular, the space- beamwidth product M{sup 2}, can be obtained in a single measurement. The intensity and phase information can be used in concert with information about other elements in the optical train to predict the beam size, shape, phase and other characteristics anywhere in the optical train. We present preliminary measurements of an Ar{sup +} laser beam and associated M{sup 2} calculations.
Date: September 1996
Creator: Neal, D. R.; Alford, W. J.; Gruetzner, J. K. & Warren, M. E.
Partner: UNT Libraries Government Documents Department

Developments on the Toroid Ion Trap Analyzer

Description: Investigations into several areas of research have been undertaken to address the performance limitations of the toroid analyzer. The Simion 3D6 (2) ion optics simulation program was used to determine whether the potential well minimum of the toroid trapping field is in the physical center of the trap electrode structure. The results (Figures 1) indicate that the minimum of the potential well is shifted towards the inner ring electrode by an amount approximately equal to 10% of the r0 dimension. A simulation of the standard 3D ion trap under similar conditions was performed as a control. In this case, the ions settle to the minimum of the potential well at a point that is coincident with the physical center (both radial and axial) of the trapping electrodes. It is proposed that by using simulation programs, a set of new analyzer electrodes can be fashioned that will correct for the non- linear fields introduced by curving the substantially quadrupolar field about the toroid axis in order to provide a trapping field similar to the 3D ion trap cross- section. A new toroid electrode geometry has been devised to allow the use of channel- tron style detectors in place of the more expensive multichannel plate detector. Two different versions have been designed and constructed - one using the current ion trap cross- section (Figure 2) and another using the linear quedrupole cross- section design first reported by Bier and Syka (3).
Date: June 13, 1999
Creator: Lammert, S.A.; Thompson, C.V. & Wise, M.B.
Partner: UNT Libraries Government Documents Department

Laser-heterodyne interferometry with streak camera detection

Description: The spatial interference pattern between a cw laser local oscillator and a pulsed laser (40 to 80 ns pulsewidth) is recorded by an electronic streak camera. Analysis yields time dependent wavefront and frequency chirp characteristics of single laser pulses. 2 refs., 3 figs.
Date: January 1, 1988
Creator: Feldman, M.; Salmon, J.T. & Mockler, D.
Partner: UNT Libraries Government Documents Department

An improved time-of-flight ion charge state diagnostic

Description: A time-of-flight diagnostic for analysis of relatively low energy ion beams is described. The system incorporates several novel features which improve its performance in a number of ways. The technique is simple and can provide an alternative to magnetic analysis of ion beams for the determination of ion charge state and beam composition.
Date: March 1, 1987
Creator: Brown, I.G.; Galvin, J.E.; MacGill, R.A. & Wright, R.T.
Partner: UNT Libraries Government Documents Department

Gaussian optics calculations of the parameters of a magnetic sector energy analyzer

Description: The design of a magnetic deflection system for use as an electron energy loss spectrometer can be a complex process if one takes the most general approach. However, for application to materials research the design process can be reduced to three basic steps. First, the qualitative features of the overall system are defined--i.e., incident electron energy, required resolution, type of magnet, the desired focal properties, etc. Secondly, the design parameters necessary to meet these requirements are calculated using the appropriate equations. Finally, once the magnetic field has been specified, ray-tracing techniques can be employed to verify the system response to the conditions defined in the first two steps. The calculation of the parameters of a uniform field magnetic sector analyzer capable of energy resolutions of 20 ppM or better are considered. Higher resolution is attainable; however, for most materials work, more important considerations are the attainment of double focusing to improve S/N, the minimization of aberrations and the achievement of a flat image plane to facilitate parallel data recording.
Date: January 1, 1978
Creator: Zaluzec, N.J.
Partner: UNT Libraries Government Documents Department

E/parallels/B end-loss-ion analyzer for TMX-U

Description: We are constructing and testing a diagnostic intrument to investigate, in detail, ions emanating along magnetic-field lines from the plasma region of the TMX-U tandem-mirror experiment. This analyzer (of TFTR design) contains parallel electric and magnetic fields, which yield ion mass and energy spatial separation, respectively. A two-dimensional array of 128 copper collector plates detects the particles. The entering ion flux is first well collimated and then focused onto the detector plane during the 180/sup 0/ bending in the magnetic field. This instrument is designed to measure higher particle energies than the present gridded end-loss analyzers as well as determine the energy spectra more accurately. Tandem-mirror plasma parameters to be investigated with this analyzer include end-plug potential, average central-cell-ion energy, and plasma potential in the thermal-barrier and nearby regions. We plan a time resolution of up to 2 kHz for each detector.
Date: September 14, 1984
Creator: Foote, J.H.; Coutts, G.W.; Pedrotti, L.R.; Schlander, L. & Wood, B.E.
Partner: UNT Libraries Government Documents Department

Large-acceptance-angle gridded analyzers in an axial magnetic field

Description: Electrostatic retarding-potential gridded analyzers have been used to measure the current and the axial energy distributions of ions escaping along magnetic field lines in the 2XIIB magnetic mirror fusion experiment at Lawerence Livermore National Laboratory (LLNL). Three analyzers are discussed: a large scanning analyzer with a movable entrance aperture that can measure ion or electron losses from a different segment of the plasma diameter on each shot, a smaller analyzer that mounts in 5-cm-diam ports, and a multicollector analyzer that can continuously measure losses from the entire plasma diameter.
Date: June 1, 1981
Creator: Molvik, A.W.
Partner: UNT Libraries Government Documents Department

Optical diagnostics in the advanced test accelerator (ATA) environment

Description: The ATA is a 50-MeV, 10-kA, 70-ns pulsed electron beam accelerator that generates an extremely harsh environment for diagnostic measurements. Diagnostic targets placed in the beamline are subject to damage, frequently being destroyed by a single pulse. High radiation (x-ray, gamma, and neutron) and electromagnetic interference levels preclude placing components near the beamline that are susceptible to radiation damage. Examples of such components are integrated circuit elements, hydrocarbons such as Teflon insulation, and optical components that darken, resulting in transmission loss. Optical diagnostics play an important part in measuring experimental parameters such as the beam current density profile. A large number of optical lines of sight (LOS) are routinely deployed along the experimental beamlines that use the ATA beam. Gated TV cameras are located outside the accelerator tunnel, because the tunnel is inaccessible during operations. We will describe and discuss the difficulties, problems, and solutions encountered in making optical measurements in the ATA environment.
Date: May 1, 1987
Creator: Chong, Y.P.; Cornish, J.P. & Donnelly, D.
Partner: UNT Libraries Government Documents Department

Latency differences and effects of selective attention to gratings in the central and right visual fields: II

Description: The goals were to examine the temporal sequence in which visual information (such as visual field, spatial frequency) are processed and to determine whether different neural sources are activated when such features are attended versus not attended. These issues are basic to current models of visual selective attention. 10 refs., 4 figs.
Date: January 1, 1987
Creator: Aine, C.J.; George, J.S. & Flynn, E.R.
Partner: UNT Libraries Government Documents Department

Bragg reflection transmission filters for variable resolution monochromators

Description: There are various methods for improving the angular and spectral resolution of monochromator and analyzer systems. The novel system described here, though limited to higher x-ray energies (>20keV), is based on a dynamical effect occurring on the transmitted beam with a thin perfect crystal plate set in the Bragg reflection case. In the case of Bragg reflection from a perfect crystal, the incident beam is rapidly attenuated as it penetrates the crystal in the range of reflection. This extinction length is of the order of microns. The attenuation length, which determines the amount of normal transmission through the plate is generally much longer. Thus, in the range of the Bragg reflection the attenuation of the transmitted beam can change by several orders of magnitude with a small change in energy or angle. This thin crystal plate cuts a notch in the transmitted beam with a width equal to its Darwin width, thus acting as a transmission filter. When used in a non-dispersive mode with other monochromator crystals, the filter when set at the Bragg angle will reflect the entire Darwin width of the incident beam and transmit the wings of the incident beam distribution. When the element is offset in angle by some fraction of the Darwin width, the filter becomes useful in adjusting the angular width of the transmitted beam and removing a wing. Used in pairs with a symmetric offset, the filters can be used to continuously adjust the intrinsic angular divergence of the beam with good wing reduction. Instances where such filters may be useful are in improving the angular resolution of a small angle scattering camera. These filters may be added to a Bonse-Hart camera with one pair on the incident beam to reduce the intrinsic beam divergence and a second pair on the analyzer arm ...
Date: January 1, 1989
Creator: Chapman, D. (Brookhaven National Lab., Upton, NY (USA))
Partner: UNT Libraries Government Documents Department

Microchannel plate based detector for a heavy ion beam spectrometer

Description: The design parameters and operating characteristics of the detector used in the Brutus and Fannie heavy ion beam spectrometers at the SuperHILAC facility are described. The detector utilizes a 25 mm diameter microchannel plate array to obtain gains of 10/sup 2/ to 10/sup 8/ with a linear dynamic range of 10/sup 3/. It has had over three years of almost maintenance-free service, detecting ion beams from carbon to xenon with energies between 1.2 and 8.5 MeV per nucleon.
Date: October 1, 1979
Creator: Green, M.I.
Partner: UNT Libraries Government Documents Department

High resolving power spectrometer for beam analysis

Description: We describe a system designed to analyze the high energy, closely spaced bunches from individual RF pulses. Neither a large solid angle nor momentum range is required so this allows characteristics that appear useful for other applications such as ion beam lithography. The spectrometer is a compact, double-focusing QBQ design whose symmetry allows the Quads to range between F or D with a correspondingly large range of magnifications, dispersion and resolving power. This flexibility insures the possibility of spatially separating all of the bunches along the focal plane with minimal transverse kicks and bending angle for differing input conditions. The symmetry of the system allows a simple geometric interpretationof the resolving power in terms of thin lenses and ray optics. We discuss the optics and the hardware that is proposed to measure emittance, energy, energy spread and bunch length for each bunch in an RF pulse train for small bunch separations. We also discuss how to use such measurements for feedback and feedforward control of these bunch characteristics as well as maintain their stability. 2 refs.
Date: March 1, 1992
Creator: Moshammer, H.W. & Spencer, J.E.
Partner: UNT Libraries Government Documents Department

Visual evoked responses to sinusoidal gratings presented in central and right visual fields: I

Description: The present study applies neuromagnetic measurement techniques to probe the neurophysiological processing of spatial frequency (SF) by normal human observers. By exploiting the temporal and spatial resolution of neuromagnetic measurements, we hope to discriminate and characterize underlying neural functions and explore their correlation with perceptual or behavioral performance measures. Spatial frequency analysis has proven a useful paradigm for the study of visual perception and has been applied in psychophysical studies as well as invasive anatomical and physiological studies of experimental animals. These approaches have produced evidence of specialized neural activity and network structure for the analysis of spatial frequency information. Because the encoding of spatial frequency is a function of neuronal receptive-field size and since receptive-field size varies as a function of retinal location, we have also examined effects of visual field on responses to stimuli of defined spatial frequency content. 10 refs., 3 figs.
Date: January 1, 1987
Creator: George, J.S.; Aine, C.J. & Flynn, E.R.
Partner: UNT Libraries Government Documents Department

Analyzing gigahertz bunch length instabilities with a digital signal processor

Description: A bunch length instability, nicknamed the sawtooth'', because of its transient behavior, has been observed at high current running in the Stanford Linear Collider (SLC) electron damping ring. The incompatibility of this instability with successful SLC naming prompted its study using a high bandwidth real-time spectrum analyzer, the Tektronix 3052 digital signal processor (DSP) system. This device has been used to study energy ramping in storage rings but this is the first time it has been used to study transient instability phenomena. It is a particularly valuable tool for use in understanding non-linear, multiple frequency phenomena. The frequency range of this device has been extended through the use of radio frequency (RF) down converters. This paper describes the measurement setup and presents some of the results.
Date: November 1, 1992
Creator: Stege, R.E. Jr.; Krejcik, P. & Minty, M.G.
Partner: UNT Libraries Government Documents Department

An interference wiggler for precise diagnostics of electron beam energy

Description: Relativistic electrons passing through two identical magnetic sections generate synchrotron radiation whose spectrum is strongly modulated as the photon energy varies. The modulation is caused by the interference of radiation from each section, and has been observed in the spectrum of spontaneous radiation from transverse optical klystron which utilizes two undulators. In this paper, another device based on two simple wigglers is analyzed. The device, which will be called the interference wiggler, can be used for precise diagnostics of electron beam energy; by analyzing the modulated spectrum with a monochromator, the electron energy can be determined up to an accuracy of 10/sup -3/ or 10/sup -4/. General design criteria for interference wigglers are developed. Several example designs are given for measurement of the electron energy for the planned electron beam facility at CEBAF for the 1 to 2 GeV Light Source at Berkeley.
Date: March 1, 1987
Creator: Kim, Kwang-Je
Partner: UNT Libraries Government Documents Department

A novel method for measuring beam energies by time-of-flight

Description: A novel time-of-flight (TOF) technique is reported for the measurement of ion beam energies. This technique was used, along with a more conventional nuclear reaction technique, to measure the calibration function of the Holifield Heavy Ion Research Facility tandem accelerator energy-analyzing magnet. The technique to be described is based on the use of a variable frequency buncher and two identical capacitive pickup units (CPU) to measure the velocity of ions selected by the energy-analyzing magnet. The CPUs were separated by a distance of 6166.2 +- 0.4 mm and were connected by equal length cables to wide band HP-8447F preamplifiers which in turn were connected to a dual trace oscilloscope. The beam was bunched using the first harmonic element of the double-drift bunching system which is located in the tandem accelerator injection line.
Date: January 1, 1986
Creator: Olsen, D.K.; Erb, K.A.; Jones, C.M.; Milner, W.T. & Ziegler, N.F.
Partner: UNT Libraries Government Documents Department

Experiment to measure the electron neutrino mass using a frozen tritium source

Description: We are performing an experiment to determine the electron neutrino mass with the precision of a few eV by measuring the tritium beta decay energy distribution near the endpoint. Key features of the experiment are a 2 eV resolution electrostatic spectrometer and a high-activity frozen tritium source. It is important that the source have electronic wavefunctions which can be accurately calculated. These calculations can be precisely made for tritium and the HeT/sup +/ daughter ion and allow determination of branching fractions to 0.1% and energy of the excited states to 0.1 eV. We discuss the excited final molecular state calculations and describe the experimental apparatus. 2 references, 6 figures.
Date: March 1, 1985
Creator: Fackler, O.; Mugge, M.; Sticker, H.; White, R.M. & Woerner, R.
Partner: UNT Libraries Government Documents Department

Monochromator harmonic content measurements and calculations at energies above 20 keV

Description: Measurements of the harmonic content from single and double crystal silicon monochromators have been made in the 20 to 100 keV at the X17 Superconducting Wiggler Beamline at the NSLS. These measurements are compared with calculations which estimate the monochromatic beam harmonic content and the detection system efficiency with good agreement. At high photon energies ( > 20keV), the scattering of x-rays from an amorphous scatterer is dominated by the inelastic Compton process. At large scattering angles this will completely overwhelm the more forward directed elastic scattering. The Compton x-ray energy shift is large enough to make the distinction between elastic and Compton scattering unambiguous when a spectrum is acquired with a solid state detector. This shift, which is energy dependent, allows the measurement of the relative harmonic intensity in a way that is not affected by pulse pileup in the detector and electronics. The present measurements were done to assess the level of harmonic contamination from two monochromator systems both used on the X17 beamline: the single crystal type monochromator for the Digital Subtraction Coronary Angiography project; and the double crystal monochromator being developed for the Multiple Energy Computed Tomography (MECT) project and the Materials Science program. 5 refs.
Date: January 1, 1991
Creator: Chapman, D.; Moulin, H. & Garrett, R.F.
Partner: UNT Libraries Government Documents Department

A high repetition rate beam profile monitor

Description: A high repetition rate beam profile monitor is needed to measure the momentum distribution of each bunch in a 200 bunch train at the Brookhaven Accelerator Test Facility. We have designed a monitor using secondary emission from a microstrip delay line. The delay line converts position information into discrete time delays synchronous with the sampling rate of a fast transient digitizer. We present the results of initial electrical testing here.
Date: January 1, 1991
Creator: Rogers, J.T.; Warren, J.B. (Brookhaven National Lab., Upton, NY (United States)) & Gray, A. (State Univ. of New York, Stony Brook, NY (United States). Dept. of Physics)
Partner: UNT Libraries Government Documents Department

Microstructure and magnetic properties of spinodal Fe--Cr--Co alloys

Description: The relationship between the microstructure and magnetic properties of spinodally decomposed Fe--Cr--Co ductile permanent magnet alloys was investigated using transmission electron microscopy, electron diffraction, Lorentz microscopy, and magnetic analysis. Isothermal aging of three alloys (Fe-16 wt percent Cr-28 wt percent Co, Fe-31 wt percent Cr-23 wt percent Co, Cr-26 wt percent Fe-13 wt percent Co) resulted in decomposition into two phases, an Fe--Co rich phase (..cap alpha../sub 1/) and a Cr-rich phase (..cap alpha../sub 2/). The microstructural features of the decomposed products were consistent with those expected and agree with the asymmetry in shape of the reported miscibility gap in the Fe--Cr--Co system. An Fe-31 wt percent Cr-23 wt percent Co alloy was found to be best among the three alloys as a permanent magnet because of its combination of good ductility and good magnetic properties.
Date: May 1, 1978
Creator: Okada, M.
Partner: UNT Libraries Government Documents Department