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2003

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Monte Carlo Simulations Of Low-Energy Cosmogenic Neutron Fluxes Near The Bottom Of Cliff Faces, J. A. Dunne, D. Elmore Jan 2003

Monte Carlo Simulations Of Low-Energy Cosmogenic Neutron Fluxes Near The Bottom Of Cliff Faces, J. A. Dunne, D. Elmore

Department of Physics and Astronomy Faculty Publications

Cosmogenic radionuclide analysis for determining exposure ages and erosion rates is becoming more extensively utilized. Due to the complexity of the neutron absorption production avenue, the interpretation of Cl-36 data is a complex problem, particularly for non-trivial landform geometries. This work provides a numerical, Monte Carlo simulation analysis of variations in in situ cosmogenic Cl-36 production rate near the bottom of vertical cliffs. It is found that in comparison with production at height (more than a thermal neutron mean free path length in air) the production rate in the cliff face increases with decreasing height, but within a thermal neutron …

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Seismic Focusing By A Single Planar Fracture, A. Oliger, D. D. Nolte, L. J. Pyrak-Nolte Jan 2003

Seismic Focusing By A Single Planar Fracture, A. Oliger, D. D. Nolte, L. J. Pyrak-Nolte

Department of Physics and Astronomy Faculty Publications

[1] A single plane fracture with an axially symmetric stress distribution behaves as a seismic lens that focuses seismic energy to a beam "waist'' at a focal plane. Both phase and amplitude effects on a seismic wave propagating across the fracture contribute to the lensing behavior. Radial gradients in the fracture specific stiffness cause wave refraction through a radially varying group time delay, while the fracture transmission amplitude approximates a Fresnel zone plate. This work demonstrates that a two-dimensional planar fracture, contrasted with three-dimensional geologic structures such as basins and domes, can focus seismic waves. Focusing of seismic waves by …

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Control Of Cl-36 Production In Carbonaceous Shales By Phosphate Minerals, G. Chmiel, S. J. Fritz, D. Elmore Jan 2003

Control Of Cl-36 Production In Carbonaceous Shales By Phosphate Minerals, G. Chmiel, S. J. Fritz, D. Elmore

Department of Physics and Astronomy Faculty Publications

When using Cl-36 to date very old groundwater in regional aquifer systems, knowledge of the subsurface Cl-36 input into the aquifer system is essential. Although Cl-36 can be produced through nuclear reactions in the subsurface, in many situations, the input of Cl-36 into sedimentary aquifer systems by this avenue of production can be neglected. This is a valid assumption when investigating long-flowpath groundwater systems composed of sandstones, limestones, and shales of typical composition. These rock types are not sufficiently enriched in radioactive elements to produce significant Cl-36 in the deep subsurface. Carbonaceous shales, on the other hand, can concentrate the …

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Accelerator Mass Spectrometry In Geologic Research, P. Muzikar, D. Elmore, D. E. Granger Jan 2003

Accelerator Mass Spectrometry In Geologic Research, P. Muzikar, D. Elmore, D. E. Granger

Department of Physics and Astronomy Faculty Publications

The ability of accelerator mass spectrometry (AMS) to measure very small concentrations of the nuclides Be-10, C-14, Al-26, Cl-36, and I-129 has led to many innovative applications in geologic research. To take advantage of this opportunity in the geosciences, it is important to understand how AMS works, how these nuclides are produced, and how they can be applied to geologic problems. We first discuss the basics of AMS, explaining what gives the method its ability to count small numbers of these nuclides. We review how these nuclides are produced and transported in the atmosphere, hydrosphere, and lithosphere. We then explain …

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Detection Of Tev Gamma Rays From The Bl Lacertae Object 1es 1959+650 With The Whipple 10 Meter Telescope, J. Holder, I. H. Bond, P. J. Boyle, S. M. Bradbury, J. H. Buckley, D. A. Carter-Lewis, W. Cui, C. Dowdall, C. Duke, I. D. Perez, A. Falcone, D. J. Fegan, S. J. Fegan, J. P. Finley, L. Fortson, J. A. Gaidos, K. Gibbs, S. Gammell, J. Hall, T. A. Hall, A. M. Hillas, D. Horan, M. Jordan, M. Kertzman, D. Kieda, J. Kildea, J. Knapp, K. Kosack, H. Krawczynski, F. Krennrich, S. Lebohec, E. T. Linton, J. Lloyd-Evans, P. Moriarty, D. Muller, T. N. Nagai, R. Ong, M. Page, R. Pallassini, D. Petry, B. Power-Mooney, J. Quinn, P. Rebillot, P. T. Reynolds, H. J. Rose, M. Schroedter, G. H. Sembroski, S. P. Swordy, V. V. Vassiliev, S. P. Wakely, G. Walker, T. C. Weekes Jan 2003

Detection Of Tev Gamma Rays From The Bl Lacertae Object 1es 1959+650 With The Whipple 10 Meter Telescope, J. Holder, I. H. Bond, P. J. Boyle, S. M. Bradbury, J. H. Buckley, D. A. Carter-Lewis, W. Cui, C. Dowdall, C. Duke, I. D. Perez, A. Falcone, D. J. Fegan, S. J. Fegan, J. P. Finley, L. Fortson, J. A. Gaidos, K. Gibbs, S. Gammell, J. Hall, T. A. Hall, A. M. Hillas, D. Horan, M. Jordan, M. Kertzman, D. Kieda, J. Kildea, J. Knapp, K. Kosack, H. Krawczynski, F. Krennrich, S. Lebohec, E. T. Linton, J. Lloyd-Evans, P. Moriarty, D. Muller, T. N. Nagai, R. Ong, M. Page, R. Pallassini, D. Petry, B. Power-Mooney, J. Quinn, P. Rebillot, P. T. Reynolds, H. J. Rose, M. Schroedter, G. H. Sembroski, S. P. Swordy, V. V. Vassiliev, S. P. Wakely, G. Walker, T. C. Weekes

Department of Physics and Astronomy Faculty Publications

We present the first strong detection of very high energy gamma-rays from the close (z=0.048) X-ray-selected BL Lacertae object 1ES 1959+650. Observations were made with the Whipple 10 m telescope on Mount Hopkins, Arizona, using the atmospheric Cerenkov imaging technique. The flux between 2002 May and July was highly variable, with a mean of 0.64+/-0.03 times the steady flux from the Crab Nebula and reaching a maximum of 5 crab, with variability on timescales as short as 7 hr.

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Accelerator-Mass-Spectrometry: Where Are We Now And Where Will We Be In 10 Years?, M. W. Caffee Jan 2003

Accelerator-Mass-Spectrometry: Where Are We Now And Where Will We Be In 10 Years?, M. W. Caffee

Department of Physics and Astronomy Faculty Publications

No abstract provided.

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Toward Coherent Neutrino Detection Using Low-Background Micropattern Gas Detectors, P. S. Barbeau, J. I. Collar, J. Miyamoto, I. Shipsey Jan 2003

Toward Coherent Neutrino Detection Using Low-Background Micropattern Gas Detectors, P. S. Barbeau, J. I. Collar, J. Miyamoto, I. Shipsey

Department of Physics and Astronomy Faculty Publications

The detection of low energy neutrinos (< few tens of MeV) via coherent nuclear scattering remains a holy grail of sorts in neutrino physics. This uncontroversial mode of interaction is expected to profit from a sizeable increase in cross section proportional to neutron number squared in the target nucleus, an advantageous feature in view of the small probability of interaction via all other channels in this energy region. A coherent neutrino detector would open the door to many new applications, ranging from the study of fundamental neutrino properties to true "neutrino technology." Unfortunately, present-day radiation detectors of sufficiently large mass (>1 kg) are not sensitive to sub keV nuclear recoils like those expected from this channel. The advent of micropattern gas detectors (MPGDs), new technologies originally intended for use in high energy physics, may soon put an end to this impasse. We present first tests of MPGDs fabricated with radioclean materials and discuss the approach to assessing their sensitivity to these faint signals. Applications are reviewed, in particular their use as a safeguard against illegitimate operation of nuclear reactors. A first industrial mass production of gas electron multipliers (GEMs) is succinctly described.

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Bone Resorption In Postmenopausal Women Using Ca-41 Technology., J. M. K. Cheong, G. S. Jackson, B. R. Martin, D. Elmore, J. R. Nolan, M. Peacock, G. P. Mccabe, C. M. Weaver Jan 2003

Bone Resorption In Postmenopausal Women Using Ca-41 Technology., J. M. K. Cheong, G. S. Jackson, B. R. Martin, D. Elmore, J. R. Nolan, M. Peacock, G. P. Mccabe, C. M. Weaver

Department of Physics and Astronomy Faculty Publications

No abstract provided.

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Robust Steady-State Filtering For Systems With Deterministic And Stochastic Uncertainties, F. Wang, V. Balakrishnan Jan 2003

Robust Steady-State Filtering For Systems With Deterministic And Stochastic Uncertainties, F. Wang, V. Balakrishnan

Department of Physics and Astronomy Faculty Publications

For uncertain systems containing both deterministic and stochastic uncertainties, we consider two problems of optimal filtering. The first is the design of a linear time-invariant filter that minimizes an upper bound on the mean energy gain between the noise affecting the system and the estimation error. The second is the design of a linear time-invariiint filter that minimizes an up per bound on the asymptotic mean square estimation error when the plant is driven by a white noise. We present filtering algorithms that solve each of these problems, with the filter parameters determined via convex optimization based on linear matrix …

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Comparison Of Various Buffer Schemes To Grow Gan On Large-Area Si(111) Substrates Using Metal-Organic Chemical-Vapor Deposition, R. Venugopal, J. Wan, M. Melloch, G. Kim, G. Zhank, S. Tsoi, A. Ramdas Jan 2003

Comparison Of Various Buffer Schemes To Grow Gan On Large-Area Si(111) Substrates Using Metal-Organic Chemical-Vapor Deposition, R. Venugopal, J. Wan, M. Melloch, G. Kim, G. Zhank, S. Tsoi, A. Ramdas

Department of Physics and Astronomy Faculty Publications

A comparison of gallium-nitride (GaN) films grown on large-area Si(111) using a single aluminum-nitride (AlN) buffer, an AlN/graded-AlxGa1-xN buffer, and the introduction of additional low-temperature (LT)-grown AlN interlayers is reported. A graded-AlGaN buffer followed by additional LT-AlN interlayers is shown to completely eliminate cracking in nitride films of thickness >2 mum and also reduce the threading-dislocation density significantly. A partial compensation of GaN-tensile strain by the compressive-lattice strain induced by the AlGaN and AlN layers is responsible for this effect. The surface roughness is increased by the introduction of the LT-AlN buffers.

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Nuclear Resonance Vibrational Spectroscopy (Nrvs): An Exciting New Technique For The Study Of Iron Porphyrinates And Heme Proteins., W. R. Scheidt, G. R. A. Wyllie, M. K. Ellison, J. T. Sage, B. K. Rai, S. M. Durbin, W. Sturhahn, E. E. Alp Jan 2003

Nuclear Resonance Vibrational Spectroscopy (Nrvs): An Exciting New Technique For The Study Of Iron Porphyrinates And Heme Proteins., W. R. Scheidt, G. R. A. Wyllie, M. K. Ellison, J. T. Sage, B. K. Rai, S. M. Durbin, W. Sturhahn, E. E. Alp

Department of Physics and Astronomy Faculty Publications

No abstract provided.

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A Dual Description Of Decoherence In De Sitter Space, S. Khlebnikov Jan 2003

A Dual Description Of Decoherence In De Sitter Space, S. Khlebnikov

Department of Physics and Astronomy Faculty Publications

Decoherence associated with super-Hubble modes in de Sitter space may have a dual description, in which it is attributed to interaction of sub-Hubble modes with an "environment" residing just inside the observer's horizon. We present a version of such description, together with some consistency checks, which it is shown to pass.

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Reversibly Altering Electronic Conduction Through A Single Molecule By A Chemical Binding Event, B. S. T. Kasibhatla, A. P. Labonte, F. Zahid, R. G. Reifenberger, S. Datta, C. P. Kubiak Jan 2003

Reversibly Altering Electronic Conduction Through A Single Molecule By A Chemical Binding Event, B. S. T. Kasibhatla, A. P. Labonte, F. Zahid, R. G. Reifenberger, S. Datta, C. P. Kubiak

Department of Physics and Astronomy Faculty Publications

This letter presents experimental evidence that the electrical conductance of a single molecule can be altered by a chemical binding event. Self-assembled monolayers of electron donor tetramethyl xylyl dithiol (TMXYL) have been synthesized and chemically switched to a conducting state by reaction with an electron acceptor tetracyanoethylene (TCNE). Low bias conductance measurements obtained by scanning tunneling spectroscopy under ultrahigh vacuum conditions show a change from insulating to ohmic behavior as a result of the electron donor/acceptor interaction.

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High-Speed Wide-Field Coherence-Gated Imaging Via Photorefractive Holography With Photorefractive Multiple Quantum Well Devices, C. Dunsby, D. Mayorga-Cruz, I. Munro, Y. Gu, P. M. W. French, D. D. Nolte, M. R. Melloch Jan 2003

High-Speed Wide-Field Coherence-Gated Imaging Via Photorefractive Holography With Photorefractive Multiple Quantum Well Devices, C. Dunsby, D. Mayorga-Cruz, I. Munro, Y. Gu, P. M. W. French, D. D. Nolte, M. R. Melloch

Department of Physics and Astronomy Faculty Publications

The parallel pixel acquisition inherent in wide-field coherence-gated imaging techniques offers the possibility of high-frame-rate imaging and volumetric imaging, including through scattering media. We discuss photorefractive holography using sensitive, dynamic photorefractive multiple quantum well (PRQW) films as a promising approach and, after reviewing the factors that determine the sensitivity of this technique, we demonstrate that high-frame-rate wide-field coherence gated imaging is possible at 830 frames per second with PRQW devices using a non-intensified camera to record the diffracted signal.

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Determination Of The Complete Set Of Iron Normal Modes In The Heme Model Compound Fe-Iii(Oep)C1 From Nuclear Resonance Vibrational Spectroscopic Data, T. E. Budarz, E. W. Prohofsky, S. M. Durbin, T. Sjodin, J. T. Sage, W. Sturhahn, E. E. Alp Jan 2003

Determination Of The Complete Set Of Iron Normal Modes In The Heme Model Compound Fe-Iii(Oep)C1 From Nuclear Resonance Vibrational Spectroscopic Data, T. E. Budarz, E. W. Prohofsky, S. M. Durbin, T. Sjodin, J. T. Sage, W. Sturhahn, E. E. Alp

Department of Physics and Astronomy Faculty Publications

The vibrational spectrum of Fe-57 in chloro iron octaethylporphyrin, Fe(OEP)Cl, has been calculated by normal-mode analysis refined to absorption data from nuclear resonance vibrational spectroscopy. This technique directly measures the amplitudes and frequencies for all modes that have significant iron participation, providing rigorous constraints to the best-fit values for the force constants. The calculated normal modes reveal the importance of Fe displacements perpendicular to the heme plane for both the lowest frequency modes and the ligand modes. The actual normal modes of Fe(OEP)Cl are not well described by single modes of the core porphyrin; instead they are hybrids of multiple …

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Lorentz Transformation And Vector Field Flows, S. H. Chiu, T. K. Kuo Jan 2003

Lorentz Transformation And Vector Field Flows, S. H. Chiu, T. K. Kuo

Department of Physics and Astronomy Faculty Publications

The parameter changes resulting from a combination of Lorentz transformations are shown to form vector field flows. The exact, finite Thomas rotation angle is determined and interpreted intuitively. Using phase portraits, the parameters evolution can be clearly visualized. In addition to identifying the fixed points, we obtain an analytic invariant which correlates the evolution of parameters.

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Measurements Of Absorption Coefficient And Refractive Index Changes Without The Kramers-Kronig Relation In Photorefractive Quantum Wells Of Gaas, R. Ramos-Garcia, R. Chiu-Zarate, D. Nolte, M. R. Melloch Jan 2003

Measurements Of Absorption Coefficient And Refractive Index Changes Without The Kramers-Kronig Relation In Photorefractive Quantum Wells Of Gaas, R. Ramos-Garcia, R. Chiu-Zarate, D. Nolte, M. R. Melloch

Department of Physics and Astronomy Faculty Publications

We measure the absorption coefficient and refractive index changes produced in photorefractive quantum wells of GaAs by using a high-sensitivity periodically phase-modulated two-wave mixing technique. The technique allows us to measure both the amplitude and phase of the refractive and absorption index changes simultaneously. Thus, there is no necessity to use the Kramers-Kronig relation when either the absorption or refractive index is known. We also measure the response time of the grating 2 formation in the frequency domain, yielding similar to15 mus at I-0 = 11 mW cm(-2), which shows that quantum wells of GaAs are one of the fastest …

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Patterned Protein Microarrays For Bacterial Detection, S. W. Howell, H. D. Inerowicz, F. E. Regnier, R. Reifenberger Jan 2003

Patterned Protein Microarrays For Bacterial Detection, S. W. Howell, H. D. Inerowicz, F. E. Regnier, R. Reifenberger

Department of Physics and Astronomy Faculty Publications

Patterned microarrays of antibodies were fabricated and tested for their ability to bind targeted bacteria. These arrays were used in a series of bacterial immunoassays to detect E. coli O157:147 and Renibacterium salmoninarum (RS). Microarrays were fabricated using microcontact printing (muCP) and characterized using scanning probe microscopy (SPM). The high-resolution SPM imaging showed that targeted bacteria had a higher binding selectivity to complementary antibody patterns than to unfunctionalized regions of the substrate. Additional studies indicated a significant reduction in binding of bacteria when the microarrays were exposed to nonspecific bacteria. These studies demonstrate how protein microarrays could be developed into …

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Direct Determination Of The Complete Set Of Iron Normal Modes In A Porphyrin-Imidazole Model For Carbonmonoxy-Heme Proteins: [Fe(Tpp)(Co)(1-Melm)], B. K. Rai, S. M. Durbin, E. W. Prohofsky, J. T. Sage, M. K. Ellison, A. Roth, W. R. Scheidt, W. Sturhahn, E. E. Alp Jan 2003

Direct Determination Of The Complete Set Of Iron Normal Modes In A Porphyrin-Imidazole Model For Carbonmonoxy-Heme Proteins: [Fe(Tpp)(Co)(1-Melm)], B. K. Rai, S. M. Durbin, E. W. Prohofsky, J. T. Sage, M. K. Ellison, A. Roth, W. R. Scheidt, W. Sturhahn, E. E. Alp

Department of Physics and Astronomy Faculty Publications

Detailed Fe vibrational spectra have been obtained for the heme model complex [Fe(TPP)(CO)-(1-Melm)] using a new, highly selective and quantitative technique, Nuclear Resonance Vibrational Spectroscopy (NRVS). This spectroscopy measures the complete vibrational density of states for iron atoms, from which normal modes can be calculated via refinement of the force constants. These data and mode assignments can reveal previously undetected vibrations and are useful for validating predictions based on optical spectroscopies and density functional theory, for example. Vibrational modes of the iron porphyrin-imidazole compound [Fe(TPP)(CO)(1-Melm)] have been determined by refining normal mode calculations to NRVS data obtained at an X-ray …

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Gauging Internal Fermionic Symmetries And Spin-3/2 Fields, S. T. Love Jan 2003

Gauging Internal Fermionic Symmetries And Spin-3/2 Fields, S. T. Love

Department of Physics and Astronomy Faculty Publications

Field theoretic models possessing a global internal fermionic shift symmetry are considered. When such a symmetry is realized locally, spin-3/2 fields appear naturally as gauge fields. Implementation of the gauging procedure requires not only the usual replacement of ordinary derivatives by covariant derivatives containing the spin-3/2 fields, but also the inclusion of additional monomials. The Higgs mechanism and the high energy Nambu-Goldstone fermion equivalence theorem axe explicitly demonstrated.

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Multiwavelength Observations Revealing The Evolution Of The Outburst Of The Black Hole Xte J1118+480, S. Chaty, C. A. Haswell, J. Malzac, R. I. Hynes, C. R. Shrader, W. Cui Jan 2003

Multiwavelength Observations Revealing The Evolution Of The Outburst Of The Black Hole Xte J1118+480, S. Chaty, C. A. Haswell, J. Malzac, R. I. Hynes, C. R. Shrader, W. Cui

Department of Physics and Astronomy Faculty Publications

We report multiwavelength observations of the soft X-ray transient XTE J1118 + 480, which we observed with UKIRT, Hubble Space Telescope (HST), RXTE, Extreme Ultraviolet Explorer (EUVE) and many other instruments and facilities. Adding radio (Ryle Telescope, VLA), submillimetre (JCMT) and X-ray (Chandra and SAX) data from the literature, we assembled the most complete spectral energy distribution (SED) of this source yet published. We followed the evolution of this source for 1 yr, including six observations performed during the outburst, and one observation at the end of the outburst. Because of the unusually high galactic latitude of XTE J1118 + …

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The Remarkable Rapid X-Ray, Ultraviolet, Optical And Infrared Variability In The Black Hole Xte J1118+480, R. I. Hynes, C. A. Haswell, W. Cui, C. R. Shrader, K. O'Brien, S. Chaty, D. R. Skillman, J. Patterson, K. Horne Jan 2003

The Remarkable Rapid X-Ray, Ultraviolet, Optical And Infrared Variability In The Black Hole Xte J1118+480, R. I. Hynes, C. A. Haswell, W. Cui, C. R. Shrader, K. O'Brien, S. Chaty, D. R. Skillman, J. Patterson, K. Horne

Department of Physics and Astronomy Faculty Publications

The transient black-hole binary XTE J1118 + 480 exhibited dramatic rapid variability at all wavelengths which were suitably observed during its 2000 April-July outburst. We examine time-resolved X-ray, ultraviolet, optical and infrared data spanning the plateau phase of the outburst. We find that both X-ray and infrared bands show large amplitude variability. The ultraviolet and optical variability is more subdued, but clearly correlated with that seen in the X-rays. The ultraviolet, at least, appears to be dominated by the continuum, although the lines are also variable. Using the X-ray variations as a reference point, we find that the ultraviolet (UV) …

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Silicon Sensors Development For The Cms Pixel System, K. Arndt, G. Bolla, D. Bortoletto, K. Giolo, R. Horisberger, A. Roy, T. Rohe, S. Son Jan 2003

Silicon Sensors Development For The Cms Pixel System, K. Arndt, G. Bolla, D. Bortoletto, K. Giolo, R. Horisberger, A. Roy, T. Rohe, S. Son

Department of Physics and Astronomy Faculty Publications

The CMS experiment will operate at the Large Hadron Collider (LHC). A hybrid pixel detector located close to the interaction region of the colliding beams will provide high resolution tracking and vertex identification which will be crucial for b quark identification. Because of the radiation environment of the LHC, the performance of the sensors must be carefully evaluated up to a fluence of 6 x 10(14) n(eq) cm(-2). We expect that the sensors will be operated partially depleted during their operation at the LHC and we have implemented an n(+) on n sensor design. We have irradiated prototype,sensors to a …

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Humidity-Dependent Open-Circuit Photovoltage From A Bacteriorhodopsin/Indium Tin Oxide Bioelectronic Heterostructure, S. Crittenden, S. Howell, R. Reifenberger, J. Hillebrecht, R. R. Birge Jan 2003

Humidity-Dependent Open-Circuit Photovoltage From A Bacteriorhodopsin/Indium Tin Oxide Bioelectronic Heterostructure, S. Crittenden, S. Howell, R. Reifenberger, J. Hillebrecht, R. R. Birge

Department of Physics and Astronomy Faculty Publications

Non-contact electrostatic force microscopy techniques were used to study the open-circuit photovoltage of purple membrane multilayers electrodeposited on indium tin oxide. A humidity-dependent photovoltage response under illumination by a 635 nm photodiode was observed. Peak photovoltages in excess of 2 V at similar to36 W m(-2) were obtained for similar to15% relative humidity.

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Irradiation Studies Of Silicon Pixel Detectors For Cms, G. Bolla, D. Bortoletto, K. Giolo, R. Horisberger, T. Rohe, C. Rott, A. Roy Jan 2003

Irradiation Studies Of Silicon Pixel Detectors For Cms, G. Bolla, D. Bortoletto, K. Giolo, R. Horisberger, T. Rohe, C. Rott, A. Roy

Department of Physics and Astronomy Faculty Publications

Prototype n(+) on n sensors with different guard rings and p-stop isolation designs were developed for the CMS Forward Pixel System. The prototype sensors were irradiated to a fluence equivalent to that expected after 6 years of operation at the LHC. I-V characteristics of these sensors after irradiation were measured. (C) 2002 Elsevier Science B.V. All rights reserved.

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Time-Sensitive Search For Chemical Agents In Gamma-Ray Spectra, J. C. Cooper, Y. E. Kim, D. S. Koltick, R. D. Koltick, B. Liu Jan 2003

Time-Sensitive Search For Chemical Agents In Gamma-Ray Spectra, J. C. Cooper, Y. E. Kim, D. S. Koltick, R. D. Koltick, B. Liu

Department of Physics and Astronomy Faculty Publications

We have performed a search for Sarin, a chemical warfare agent, in luggage-sized sealed containers in order to illustrate how effectively and quickly a search could be conducted in a fixed installation at airports, embassies, government buildings, military installations, and other public areas. A portable neutron generator and a Californium source were used, generating up to 10(8) neutrons per second, that penetrate into a container and are capable of exciting a sample in a period of approximately 10 s, to produce enough gamma radiation that target elements within the sample can be identified. In the vast majority of cases, there …

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Signal Searching In Return Spectra And Decision Making Using Minimal Integration Time, D. S. Koltick Jan 2003

Signal Searching In Return Spectra And Decision Making Using Minimal Integration Time, D. S. Koltick

Department of Physics and Astronomy Faculty Publications

Neutron scanning techniques are becoming important tools in the search for chemical agents, explosives, drugs, nuclear material and other hazardous materials in government buildings, airports, military installations or public areas. Each nucleus when excited emits quanta of gamma radiation at characteristic energies. The element can be physically located and identified by these energy lines. It is important to identify these lines in a minimal amount of time in order to increase the number of items that are searched and to allow fast flow of people and their possessions into and through facilities. This paper develops a mathematical model of the …

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A First Mass Production Of Gas Electron Multipliers, P. S. Barbeau, J. I. Collar, J. D. Geissinger, J. Miyamoto, I. Shipsey, R. Yang Jan 2003

A First Mass Production Of Gas Electron Multipliers, P. S. Barbeau, J. I. Collar, J. D. Geissinger, J. Miyamoto, I. Shipsey, R. Yang

Department of Physics and Astronomy Faculty Publications

We report on the manufacture of a first batch of approximately 2000 Gas Electron Multipliers (GEMs) using 3M's fully automated roll-to-roll flexible circuit production line. This process allows low-cost, reproducible fabrication of a high volume of GEMs of dimensions up to 30 x 30 cm(2). First tests indicate that the resulting GEMs have optimal properties as radiation detectors. Production techniques and preliminary measurements of GEM performance are described. This now demonstrated industrial capability should help further establish the prominence of micropattern gas detectors in accelerator-based and non-accelerator particle physics, imaging and photodetection. (C) 2003 Elsevier B.V. All rights reserved.

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An Aging Study Of A Micromegas With Gem Preamplification, S. Kane, J. May, J. Miyamoto, I. Shipsey Jan 2003

An Aging Study Of A Micromegas With Gem Preamplification, S. Kane, J. May, J. Miyamoto, I. Shipsey

Department of Physics and Astronomy Faculty Publications

We have conducted the first study of the aging behavior of a MICROMEGAS detector with gas electron multiplier (GEM) preamplification. Because a MICROMEGAS is constructed with minimal insulation and because the electric field is parallel to the amplification gap, superior radiation hardness was previously reported in an Ar-Isobutane gas mixture in a stand-alone device. The MICROMEGAS is expected to tolerate an even larger accumulated charge in a cleaner gas mixture, such as Ar-CO2. However, using a MICROMEGAS as a stand-alone device in this mixture could increase discharge probability and lead to faster degradation in detector performance. We show that this …

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Evaluation Of Zno(Ga) Coatings As Alpha Particle Transducers Within A Neutron Generator, J. C. Cooper, D. S. Koltick, J. T. Mihalczo, J. S. Neal Jan 2003

Evaluation Of Zno(Ga) Coatings As Alpha Particle Transducers Within A Neutron Generator, J. C. Cooper, D. S. Koltick, J. T. Mihalczo, J. S. Neal

Department of Physics and Astronomy Faculty Publications

Neutrons generated by the deuterium-tritium reaction (D-2 + T-3 --> n + alpha) are correlated to the alpha particle by energy and momentum conservation to lie along trajectories 180degrees with respect to one another. An associated particle neutron generator uses this spatial correlation to infer the neutron trajectory by detecting the alpha particle. This technique can be used to suppress backgrounds and in building three-dimensional images using the return excitation gamma-ray energy due to the neutron interactions. The critical-performance component of the system is the alpha detection element, which is embedded within the neutron generator accelerator head. This element must …

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