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Relative Cross Sections for Photo Fission and Photo Neutron Emission

Description: Abstract: The yields of U²³⁷ and a fission product were measured as a function of maximum betatron energy, The ratio of the number of fissions divided by the number of U²³⁷ atoms increases with increasing maximum betatron energy. This is consistent with the picture that the higher-energy gammas leave the U²³⁷ atoms with enough excitation energy (above photofission and photoneutron thresholds) to also decay by fission or neutron emission. This secondary process increases the number of fissions and decreases the U²³⁷ yield, this increasing the above ratio.
Date: May 20, 1952
Creator: Duffield, Robert B. & Huizenga, John R.
Partner: UNT Libraries Government Documents Department

Polarization of Bremsstrahlung

Description: Abstract: Numerical information necessary to an experimental study of the polarization of bremsstrahlung is presented. One may conclude that it is possible to produce significantly polarized γ-ray beams with existing electron accelerators. These beams will provide a new tool for the study of photonuclear reactions over a wide range of energy.
Date: September 3, 1954
Creator: Karplus, Robert & Reifman, Alfred
Partner: UNT Libraries Government Documents Department

Adaptation of a cubic smoothing spline algortihm for multi-channel data stitching at the National Ignition Facility

Description: Some diagnostics at the National Ignition Facility (NIF), including the Gamma Reaction History (GRH) diagnostic, require multiple channels of data to achieve the required dynamic range. These channels need to be stitched together into a single time series, and they may have non-uniform and redundant time samples. We chose to apply the popular cubic smoothing spline technique to our stitching problem because we needed a general non-parametric method. We adapted one of the algorithms in the literature, by Hutchinson and deHoog, to our needs. The modified algorithm and the resulting code perform a cubic smoothing spline fit to multiple data channels with redundant time samples and missing data points. The data channels can have different, time-varying, zero-mean white noise characteristics. The method we employ automatically determines an optimal smoothing level by minimizing the Generalized Cross Validation (GCV) score. In order to automatically validate the smoothing level selection, the Weighted Sum-Squared Residual (WSSR) and zero-mean tests are performed on the residuals. Further, confidence intervals, both analytical and Monte Carlo, are also calculated. In this paper, we describe the derivation of our cubic smoothing spline algorithm. We outline the algorithm and test it with simulated and experimental data.
Date: December 28, 2010
Creator: Brown, C; Adcock, A; Azevedo, S; Liebman, J & Bond, E
Partner: UNT Libraries Government Documents Department

Photon interaction data for ENDF/B-VI

Description: The ENDF/B-VI photon interaction library includes data for the elements hydrogen (Z=1) through fermium (Z=100) over the energy range 10 eV to 100 MeV. This library contains data to meet the needs of traditional photon transport methods. However, this library also contains data that can be used to perform much more detailed transport calculations. This paper describes the contents of this library and how it can be used for both traditional and more detailed transport calculations.
Date: February 1, 1994
Creator: Cullen, D. E. & Perkins, S. T.
Partner: UNT Libraries Government Documents Department

Polarization observables in pion photoproduction on light nuclei

Description: Single polarization observables {Sigma}, P, and T are investigated for the nucleon (p, n) and the trinucleon ({sup 3}He, {sup 3}H). The threshold E{sub 0+} and the resonance M{sub 1+} and E{sub 1+} multipoles are particularly studied. For the reaction {sup 3}He({gamma}, {pi}{sup +}){sup 3}H a recently developed nonlocal coupled-channel approach is presented that employs three-body Faddeev amplitudes and incorporates two-step processes such as {sup 3}He({gamma}, {pi}{sup o}){sup 3}He({pi}{sup o}, {pi}{sup +}){sup 3}H. Enhancement effects of the contributions from small components of the {sup 3}He wave function as well as from the {Delta} resonance E2 transition to the polarization observables have been found.
Date: July 1, 1994
Creator: Tiator, L.; Kamalov, S. S. & Bennhold, C.
Partner: UNT Libraries Government Documents Department

Deuteron photodisintegration: Data and plans

Description: We review existing data for the exclusive reaction {gamma}d {yields} pn at photon energies above {approx} 1 GeV. We compare these data to various models, most notably those which rely on fundamental quark and gluon degrees of freedom. We include a discussion of future plans for related measurements.
Date: September 1, 1993
Creator: Napolitano, J.; Anthony, P. & Arnold, R.
Partner: UNT Libraries Government Documents Department

Photodisintegration of the deuteron at high energy

Description: Measurements of the angular distribution for the {gamma}d{yields}+pn reaction were performed at SLAC for photon energies between 0.7 and 1.8 GeV (experiment NE8) and between 1.6 and 4.4. GeV (experiment NE17). The final results for experiment NE8 will be presented, but only preliminary results for NE17 will be discussed. The data at {theta}{sub cm} = 90{degrees} appear to follow the constituent counting rules. The angular distribution at high photon energies exhibit large values of the cross section at forward angles. There is evidence that the cross section may also be large at backward angles and high energies.
Date: August 1, 1992
Creator: Holt, R. J.
Partner: UNT Libraries Government Documents Department

Deuteron photo-disintegration at large energies

Description: Current proposals at CEBAF include the measurement of cross sections and polarization observables of exclusive photo-reactions such as deuteron photo-disintegration and pion photo-production from nucleons. At issue is the applicability of traditional meson-exchange models versus quark models of these reactions at photon energies of several GeV. Beam energies above 4 GeV at CEBAF could make possible the measurement of these reactions over a kinematic range sufficiently broad to distinguish between the models. Estimates of counting rates for a Hall-C experiment to measure the {gamma}d {yields} pn cross section are presented.
Date: August 1, 1994
Creator: Potterveld, D. H.
Partner: UNT Libraries Government Documents Department

Sum rule measurements of the spin-dependent compton amplitude (nucleon spin structure at Q{sup 2} = 0)

Description: Energy weighted integrals of the difference in helicity-dependent photo-production cross sections ({sigma}{sub {1/2}} - {sigma}{sub 3/2}) provide information on the nucleon`s Spin-dependent Polarizability ({gamma}), and on the spin-dependent part of the asymptotic forward Compton amplitude through the Drell-Hearn-Gerasimov (DHG) sum rule. (The latter forms the Q{sup 2}=0 limit of recent spin-asymmetry experiments in deep-inelastic lepton-scattering.) There are no direct measurements of {sigma}{sub {1/2}} or {sigma}{sub 3/2}, for either the proton or the neutron. Estimates from current {pi}-photo-production multipole analyses, particularly for the proton-neutron difference, are in good agreement with relativistic-l-loop Chiral calculations ({chi}PT) for {gamma} but predict large deviations from the DHG sum rule. Either (a) both the 2-loop corrections to the Spin-Polarizability are large and the existing multipoles are wrong, or (b) modifications to the Drell-Hearn-Gerasimov sum rule are required to fully describe the isospin structure of the nucleon. The helicity-dependent photo-reaction amplitudes, for both the proton and the neutron, will be measured at LEGS from pion-threshold to 470 MeV. In these double-polarization experiments, circularly polarized photons from LEGS will be used with SPHICE, a new frozen-spin target consisting of {rvec H} {center_dot} {rvec D} in the solid phase. Reaction channels will be identified in SASY, a large detector array covering about 80% of 4{pi}. A high degree of symmetry in both target and detector will be used to minimize systematic uncertainties.
Date: December 31, 1995
Creator: Babusci, D.; Giordano, G.; Baghaei, H.; Cichocki, A.; Blecher, M.; Breuer, M. et al.
Partner: UNT Libraries Government Documents Department

Investigations of the dynamics and electromagnetic interactions of few-body systems. Progress report, June 30, 1994--September 30, 1995

Description: This progress report summarizes the work of The George Washington University (GW) nuclear theory group during the period 1 July 1994 - 30 September 1995 under DOE Grant No. DE-FG02-95-ER40907 mainly dealing with photonuclear reactions and few-body problems of nuclei. This report contains: papers published or in press, submitted for publication, and in preparation; invited talks at conferences and meetings; invited talks at universities and laboratories; contributed papers or abstracts at conferences; visitors to the group; and research progress by topic.
Date: October 1, 1995
Creator: Lehman, D.R.
Partner: UNT Libraries Government Documents Department

A program in medium energy nuclear physics. Progress report, January 1, 1992--March 31, 1995

Description: This progress report and continuation proposal summarizes our achievements for the period from July 1, 1994 to September 30, 1995 and requests continued funding for our program in experimental medium-energy nuclear physics. The focus of our program remains the understanding of the short-range part of the strong interaction in the nuclear medium. In the past year we have focused our attention ever more sharply on experiments with real tagged photons, and we have successfully defended two new experimental proposals: Photofission of Actinide and Preactinide Nuclei at SAL and Photoproduction of the {rho} Meson from the Proton with Linearly Polarized Photons at CEBAF. (We are co-spokespersons on two previously approved Hall-B experiments at CEBAF, Photoreactions on {sup 3}He and Photoabsorption and Photofission of Nuclei.) As part of the team that is instrumenting the Photon Tagger for Hall B; we report excellent progress on the focal-plane detector array that is being built at our Nuclear Detector Laboratory, as well as progress on our plans for instrumentation of a tagged polarized-photon beam using coherent bremsstrahlung. Also, we shall soon receive a large computer system (from the SSC) which will form the basis for our new Data Analysis Center, which, like the Nuclear Detector Laboratory, will be operated under the auspices of The George Washington University Center for Nuclear Studies. Finally, during the past year we have published six more papers on the results of our measurements of pion scattering at LAMPF and of electron scattering at NIKHEF and Bates, and we can report that nearly all of the remaining papers documenting this long series of measurements are in the pipeline.
Date: October 1, 1995
Creator: Berman, B.L. & Dhuga, K.S.
Partner: UNT Libraries Government Documents Department

Reaction theories for N* excitations in {pi}N and {gamma}N reactions

Description: The importance of developing reaction theories for investigating N* physics is illustrated in an analysis of pion photoproduction on the nucleon. It is shown that the {gamma}N {leftrightarrow} {Delta} transition amplitudes predicted by the constituent quark model are in agreement with the values extracted from the {gamma}N {r_arrow} {pi}N data only when the contributions from the reaction mechanisms calculated using a dynamical approach are taken into account in the analysis.
Date: December 31, 1996
Creator: Lee, T. S. H.
Partner: UNT Libraries Government Documents Department

The deuteron: a mini-review

Description: We review some recent results for elastic electron deuteron scattering (deuteron form factors) and photodisintegration of the deuteron, with emphasis on the recent high energy data from Jefferson Laboratory (JLab).
Date: July 1, 2001
Creator: Gross, Franz & Gilman, R.
Partner: UNT Libraries Government Documents Department

Hypernuclear physics at TJNAF

Description: The strangeness electroproduction experiments, just starting to take data at TJNAF, are very promising for giving very useful information to understand the nuclear and nucleonic structure and reaction mechanism. The experimental program on hypernuclei already approved concerns few body, light nuclei and heavy nuclei. It will be possible to investigate these hypernuclear systems for the first time by photo- and electro-induced reactions, allowing to obtain very useful information such as {Lambda}-N interaction and weak interaction in the nuclear medium in a complementary way with respect to what can be done with hadron probes.
Date: November 1, 1999
Creator: Cisbani, E.; Frullani, S.; Garibaldi, F.; Iodice, M.; Urciuoli, G.M.; Leo, R. De et al.
Partner: UNT Libraries Government Documents Department

The Sharp Lepton Quandary: Reasonable cautions

Description: Surprisingly, the new APEX experiment designed to measure a definitive invariant mass distribution of the sharp pairs previously reported in similar heavy ion studies reports null results. Although it asserts no direct conflict with any data reported by EPOS/I, the APEX report nevertheless seems to have encouraged the view that the earlier (EPOS/I) observations were erroneous, and by extrapolation, that the whole (e{sup +}e{sup {minus}}) Puzzle data set can be dismissed as an unfortunate set of physically meaningless statistical fluctuations. We wish here to argue that such sweeping judgments should be postponed, on the grounds that (1) the published APEX analysis of their data is self-inconsistent, and can therefore sustain no valid inference about the EPOS/I data; (2) the data which supports the occurrence of sharp (e{sup +}e{sup {minus}}) pairs is much more extensive than the EPOS/I data, so that the APEX surprise must be considered as one episode in a much longer struggle finally to settle the question of whether these weak signals are significant or not; (3) a qualitative phenomenology exists which can organize the whole range of data of the Sharp Lepton Problem, and which suggests that (4) certain low energy (and low cost) experiments ought to be explored for their creation of sharp pairs; as follows: the study of pairs emitted following scattering of few MeV electron and positron beams from neutral U and Th atoms, and the study of pairs emitted following the resonant absorption of photons of 1.5 to 2.0 MeV on U and Th atoms. We first present a brief data-oriented history of the Sharp Lepton Problem, to show that no single unexpected null result can provide an adequate basis for rejecting the great range and quantity of data which evidences the occurrence of sharp pairs. We then consider the Quadronium Composite Particle ...
Date: February 1, 1996
Creator: Griffin, J.J.
Partner: UNT Libraries Government Documents Department

Electromagnetic Structure of the Deuteron

Description: Recent high energy measurements of elastic ed scattering support the use of a relativistic theory based on an accurate description of the NN channel, but theory needed for an understanding of the high energy deuteron photodisintegration cross sections and polarized observables is not yet mature.
Date: June 1, 2002
Creator: Gross, Franz
Partner: UNT Libraries Government Documents Department

Photoneutron cross sections for D$sub 2$O and beryllium

Description: The photodissociation cross section by $sup 24$Na gamma rays was measured for deuterium in order to resolve a discrepancy between earlier measurements (1.43 to 1.59 millibarns) and a more recently reported one (1.34 mb). The measurement of the beryllium ($gamma$,n) cross section for $sup 24$Na gamma rays was also included as a check. Results for deuterium (1.54 mb) are in agreement with the earlier values. (SDF)
Date: January 1, 1975
Creator: Bowsher, H. F.; Woods, F. J. & Baumann, N. P.
Partner: UNT Libraries Government Documents Department

Photonuclear Benchmarks with a Comparison of COG and MCNPX Results

Description: The Nuclear Data Section of the International Atomic Energy Agency (IAEA) has distributed an evaluated photonuclear data library in standard ENDF-6 format that is intended for use in transport codes. This ''IAEA Photonuclear Data Library'' consists of a number of individual ASCII text files for various elements that have been recently processed into the single binary (COG data library) file ''COGPNUC'' with corresponding changes to the COG code for use in transport calculations involving photonuclear reactions.
Date: October 20, 2003
Creator: Heinrichs, D P & Lent, E M
Partner: UNT Libraries Government Documents Department

Electromagnetic interactions with nucleons and nuclei. Progress report, November 1990--October 1991

Description: Our primary research effort continues to be at the LEGS project at Brookhaven National Laboratory. The LEGS facility has made a transition in the last year from a combination of experiment and facility construction to full time experimental work. The first experiment, photodisintegration of the deuteron with polarized {gamma} rays, is completed and partially published. A second experiment, {sup 3}He({gamma},NN), has also been completed and analysis has begun. We except to begin two more experiments in the next year. Other research efforts are primarily related to CEBAF and this work is growing, since major CEBAF experimental equipment is now being constructed. We are heavily involved in the CLAS collaboration in Hall B which will build the CEBAF Large Acceptance Spectrometer. Our contributions to the CEBAF experimental program and equipment construction are described. The {sup 3}He({gamma}, NN) experiment at LEGS was the second use, in a new format, of the University of Virginia Nucleon Detector System. It is now a fully developed system. We also describe a new area of instrument development, applications of waveshifting optical fibers to novel position sensitive detectors for neutral particles.
Date: October 30, 1991
Creator: Thornton, S. T. & Sealock, R. M.
Partner: UNT Libraries Government Documents Department