Author: Walfried MichaelisPublisher:
ISBN:
Category :
Languages : en
Pages : 8
Book Description
A High-resolution Ge(Li) Anti-Compton Spectrometer for Radiative Neutron Capture Spectroscopy
Author: Walfried MichaelisHigh Resolution Flat Crystal Spectrometer For Neutron Capture Gamma-Ray Studies
Author: Atomic Energy of Canada LimitedPublisher:
ISBN:
Category :
Languages : en
Pages : 35
Book Description
Cryogenic Neutron Spectrometer Development
Author: A. BurgerPublisher:
ISBN:
Category :
Languages : en
Pages : 4
Book Description
Cryogenic microcalorimeter detectors operating at temperatures around {approx}0.1 K have been developed for the last two decades, driven mostly by the need for ultra-high energy resolution (0.1%) in X-ray astrophysics and dark matter searches [1]. The Advanced Detector Group at Lawrence Livermore National Laboratory has developed different cryogenic detector technologies for applications ranging from X-ray astrophysics to nuclear science and non-proliferation. In particular, we have adapted cryogenic detector technologies for ultra-high energy resolution gamma-spectroscopy [2] and, more recently, fast-neutron spectroscopy [3]. Microcalorimeters are essentially ultra-sensitive thermometers that measure the energy of the radiation from the increase in temperature upon absorption. They consist of a sensitive superconducting thermometer operated at the transition between its superconducting and its normal state, where its resistance changes very rapidly with temperature such that even the minute energies deposited by single radiation quanta are sufficient to be detectable with high precision. The energy resolution of microcalorimeters is fundamentally limited by thermal fluctuations to {Delta}E{sub FWHM} {approx} 2.355 (k{sub B}T{sup 2}C{sub abs}){sup 1/2}, and thus allows an energy below 1 keV for neutron spectrometers for an operating temperature of T {approx} 0.1 K . The {Delta}E{sub FWHM} does not depend on the energy of the incident photon or particle. This expression is equivalent to the familiar (F{var_epsilon}E{sub {gamma}}){sup 1/2} considering that an absorber at temperature T contains a total energy C{sub abs}T, and the associated fluctuation are due to variations in uncorrelated (F=1) phonons ({var_epsilon} = k{sub B}T) dominated by the background energy C{sub abs}T” E{gamma}. The rationale behind developing a cryogenic neutron spectrometer is the very high energy resolution combined with the high efficiency. Additionally, the response function is simple and the instrument is transportable. We are currently developing a fast neutron spectrometer with 0.1% energy resolution at 1 MeV neutron energy with an efficiency of 1%. Our fast-neutron spectrometers use boron-based and {sup 6}LiF absorber crystals with Mo/Cu thermistors readout. They have achieved an energy resolution of 5.5 keV FWHM for 2.79 MeV deposited in {sup 10}B by thermal neutron capture (fig. 1), and 46 keV FWHM for fast (MeV) neutrons absorbed in {sup 6}LiF (fig. 2). Since the energy resolution does not depend on the neutron energy, we expect a similar energy resolution for MeV neutron energies. The response function is given simply by the cross section of the capture reaction, offset from zero by the Q-value of the capture reaction. This allows straightforward discrimination against gamma-events, most of which deposit less that Q{sub 6Li} = 4.79 MeV in the {sup 6}LiF absorber, and easy deconvolution of the neutron spectrum, since there is only a single capture reaction in {sup 6}Li and the spectrum is not affected by edge effects or geometric broadening. The current challenge for microcalorimeters is their necessarily small effective pixel area, {approx}1cm{sup 3} for neutron spectrometer pixels, and their slow decay time, {approx}10ms for neutron spectrometers. The pixel size is limited by the requirement for low Cabs for high energy resolution; the decay time is set by the intrinsically weak thermal coupling between materials at low temperatures. Both issues can be addressed by fabricating large detector arrays. This will enable high-precision neutron spectrometry with high statistics, such as simulated for Pu analysis in fig 3.
Proposal for Installation of an Anticompton-spectrometer for Neutron Capture Gamma-ray Spectroscopy
Author: Walfried MichaelisConstruction and Calibration of an Anti-compton Spectrometer
Author: Joseph A. MuscariPublisher:
ISBN:
Category :
Languages : en
Pages : 55
Book Description
By suppressing the Compton response the anti-Compton spectrometer emphasizes the photopeak without sacrificing resolution. The detector's response matrix is experimentally determined with five monoenergetic gamma ray sources. By interpolating between these known energies and extrapolating from these measured shapes the response to gamma rays within the range 230 Kev to 1460 Kev is found. Applying the inverse response matrix to several line spectra unfolds the pulse height spectra.
ACTI - An MCNP Data Library for Prompt Gamma-Ray Spectroscopy
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 21
Book Description
Prompt gamma-ray spectroscopy is used in a wide variety of applications for determining material compositions. High-quality photon-production data from thermal-neutron capture reactions are essential for these applications. Radiation transport codes, such as MCNP{trademark}, are often used to design detector systems, determine minimum detection thresholds, etc. These transport codes rely on evaluated nuclear databases such as ENDF (Evaluated Nuclear Data File) to provide the fundamental data used in the transport calculations. Often the photon-production data from incident neutron reactions in the evaluations are of relatively poor quality. We have compiled the best experimental data for thermal-neutron capture for the naturally occurring isotopes for elements from H through Zn as well as for {sup 70,72,73,74,76}Ge, 149Sm, {sup 155,157}Gd, 181Ta and {sup 182,183,184,186}W. This compilation has been used to update the ENDF evaluations for 1H, 4He, 9Be, 14N, 16O, 19F, Na, Mg, 27Al, 32S, S, {sup 35,37}Cl, K, Ca, 45Sc, Ti, 51V, {sup 50,52,53,54}Cr, 55Mn, {sup 54,56,57,58}Fe, {sup 58,60,61,62,64}Ni, {sup 63,65}Cu and {sup 182,183,184,186}W. In addition, the inelastic cross sections and corresponding secondary-photon distributions were updated for 16O. Complete new evaluations were submitted to ENDF for {sup 35,37}Cl. This paper will discuss the evaluation effort and the production of the MCNP data library, ACTI, based on the new evaluations. Data from the ENDF evaluations for 28−3°Si were also included in the ACTI library for completeness. The silicon evaluations were updated in 1997 and include the latest experimental data for radiative capture.
Detection System for High-resolution Gamma Radiation Spectroscopy with Neutron Time-of-flight Filtering
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
A .gamma.-radiation detection system that includes at least one semiconductor detector such as HPGe-Detector, a position-sensitive .alpha.-Detector, a TOF Controller, and a Digitizer/Integrator. The Digitizer/Integrator starts to process the energy signals of a .gamma.-radiation sent from the HPGe-Detector instantly when the HPGe-Detector detects the .gamma.-radiation. Subsequently, it is determined whether a coincidence exists between the .alpha.-particles and .gamma.-radiation signal, based on a determination of the time-of-flight of neutrons obtained from the .alpha.-Detector and the HPGe-Detector. If it is determined that the time-of-flight falls within a predetermined coincidence window, the Digitizer/Integrator is allowed to continue and complete the energy signal processing. If, however, there is no coincidence, the Digitizer/Integrator is instructed to be clear and reset its operation instantly.
Neutron Generators for Analytical Purposes
Author: International Atomic Energy AgencyPublisher: IAEA Radiation Technology Repo
ISBN: 9789201251107
Category : Science
Languages : en
Pages : 145
Book Description
This publication addresses recent developments in neutron generator (NG) technology. It presents information on compact instruments with high neutron yield to be used for neutron activation analysis (NAA) and prompt gamma neutron activation analysis in combination with high count rate spectrometers. Traditional NGs have been shown to be effective for applications including borehole logging, homeland security, nuclear medicine and the on-line analysis of aluminium, coal and cement. Pulsed fast thermal neutron analysis, as well as tagged and timed neutron analysis, are additional techniques which can be applied using NG. Furthermore, NG can effectively be used for elemental analysis and is also effective for analysis of hidden materials by neutron radiography. Useful guidelines for developing NG based research laboratories are also provided in this publication.
A High Resolution Neutron Spectrometer Using Mica Analyzers and Pulsed Cold Source
Author: Kazuhiko InoueHigh Resolution Neutron Spectroscopy in the Kilovolt Region ...
Author: Paul Frothingham NicholsPublisher:
ISBN:
Category : Bismuth
Languages : en
Pages :
Book Description