Development of a quasi-monoenergetic neutron field using the 7Li(p,n)7Be reaction in the energy range from 250 to 390 MeV at RCNP

A quasi-monoenergetic neutron field using the (7)Li(p,n)(7)Be reaction has been developed at the ring cyclotron facility at the Research Center for Nuclear Physics (RCNP), Osaka University. Neutrons were generated from a 10-mm-thick Li target injected by 250, 350 and 392 MeV protons and neutrons produced at 0 degrees were extracted into the time-of-flight (TOF) room of 100-m length through the concrete collimator of 10 x 12 cm aperture and 150 cm thickness. The neutron energy spectra were measured by a 12.7-cm diam x 12.7-cm long NE213 organic liquid scintillator using the TOF method. The peak neutron fluence was 1.94 x 10(10), 1.07 x 10(10) and 1.50 x 10(10) n sr(-1) per muC of 250, 350 and 392 MeV protons, respectively. The neutron spectra generated from various thick (stopping length) targets of carbon, aluminium, iron and lead, bombarded by 250 and 350 MeV protons, were also measured with the TOF method. Although these measurements were performed to obtain thick target neutron yields, they are also used as a continuous energy neutron field. These neutron fields are very useful for characterising neutron detectors, measuring neutron cross sections, testing irradiation effects for various materials and performing neutron shielding experiments.     

Development of a fast neutron radiography converter using wavelength-shifting fibers

A fluorescent converter for fast neutron radiography (FNR) comprising a scintillator and hydrogen-rich resin has been developed and applied to electronic imaging. The rate of the reaction between fast neutrons and the converter is increased by thickening the converter, but its opaqueness attenuates emitted light photons before they reach its surface. To improve the luminosity of a fluorescent converter for FNR, a novel type of converter was designed in which wavelength-shifting fibers were adopted to transport radiated light to the observation end face. The performance of the converter was compared with that of a polypropylene-based fluorescent converter in an experiment conducted at the fast-neutron-source reactor YAYOI in the University of Tokyo.     

Characterisation of kilo electron volt neutron fluence standard with the 45Sc(p,n)45Ti reaction at NMIJ

We are developing a national standard of a monoenergetic kilo electron volt neutron field with the (45)Sc(p,n)(45)Ti resonance reaction. A wide resonance yields 27.4 keV neutrons at 0 degrees with respect to the proton beam. The proton energy was precisely determined in the measurement of the relative neutron yield as a function of the proton energy from the threshold energy to 2.942 MeV. Absolute measurement of the monoenergetic neutron fluence was performed using a (3)He proportional counter. Relative measurement was also carried out using a Bonner sphere calibrated at our 144 keV standard neutron field. Calibration factors were obtained between the count of a neutron monitor and the neutron fluence. A silicon-surface barrier detector with a (6)LiF foil converter was also being developed for the neutron fluence measurement. Successful results were obtained in the tests in the 144 keV standard neutron field.     

Construction of monoenergetic neutron calibration fields using 45Sc(p, n)45Ti reaction at JAEA

The 8 and 27 keV monoenergetic neutron calibration fields have been developed by using (45)Sc(p, n)(45)Ti reaction. Protons from a 4-MV Pelletron accelerator are used to bombard a thin scandium target evaporated onto a platinum disc. The proton energies are finely adjusted to the resonance to generate the 8 and 27 keV neutrons by applying a high voltage to the target assemblies. The neutron energies were measured using the time-of-flight method with a lithium glass scintillation detector. The neutron fluences at a calibration point located at 50 cm from the target were evaluated using Bonner spheres. A long counter was placed at 2.2 m from the target and at 60 degrees to the direction of the proton beam in order to monitor the fluence at the calibration point. Fluence and dose equivalent rates at the calibration point are sufficient to calibrate many types of the neutron survey metres.     

The Humidity Calibration Facility of the National Metrology Institute of South Africa (NMISA)

The NMISA Humidity Laboratory maintains the South African national measurement standards for humidity and provides traceability for commercial calibration laboratories. The laboratory performs both relative humidity and dew-point calibrations. The laboratory has been accredited since January 2004 for both parameters by the South African National Accreditation System (SANAS). Industries such as the pharmaceutical industry, power stations, and the food industry make use of the calibration services provided by the laboratory. The facilities and the measurement capabilities of the laboratory are presented in this paper. Two calibration methods are used for the calibration of relative humidity measuring instruments (RH meters). Depending on the type of instrument, they are calibrated against aqueous salt solutions or by comparison with reference RH meters. Measurements are performed over the humidity range 5–95 %rh (Best Measurement Capabilities: 0.4–1.4 %rh). Two chilled-mirror hygrometers are used as reference standards for dew-point calibrations over the range from −75°Cfp to +17°Cdp (Best Measurement Capabilities: 1.5°Cdp to 0.4°Cdp). The laboratory has participated in two international interlaboratory comparisons, one for each accredited parameter. The NMISA Humidity Laboratory is working to reduce its calibration uncertainties for relative humidity instruments: since first accredited in 2004, the best measurement capabilities have been improved from 2.1 %rh to 0.4 %rh for some humidity ranges.     

Investigation of the neutron energy distribution of the IRSN 241Am-Be(alpha,n) source

The neutron energy distribution of the IRSN standard (241)Am-Be(alpha,n) source was measured using a proton recoil liquid scintillator, BC501A, >1.65 MeV. The experimental data were compared with the ISO recommended neutron energy distribution for an Am-Be source and some significant discrepancies were observed. Monte Carlo simulations were then performed to investigate on the neutron source term in order to consider the different parameters between the IRSN Am-Be source and the one used to establish the neutron emission spectrum recommended by the ISO standard. The variation of the parameters of the source did not explain the remaining discrepancies. A good agreement with the experimental results was observed when the theoretical neutron energy distribution from Geiger and Van der Zwan was introduced in the study as new source term. These investigations showed that the ISO recommended Am-Be distribution might not be well suited to represent the neutron energy distribution of all Am-Be sources, and that the manufacturing of the sources might play a major role in the neutron fluence energy distribution.     

PINO—a tool for simulating neutron spectra resulting from the Li(p,n) reaction

The ⁷Li(p,n) reaction in combination with a 3.7 MV Van de Graaff accelerator was routinely used at FZK to perform activation as well as time-of-flight measurements with neutrons in the keV-region. Planned new setups with much higher proton currents like SARAF and FRANZ and the availability of liquid-lithium target technology will trigger a renaissance of this method. A detailed understanding of the neutron spectrum is not only important during the planning phase of an experiment, but also for the analysis of activation experiments. Therefore, the Monte-Carlo based program PINO (Protons In Neutrons Out) was developed, which allows the simulation of neutron spectra considering the geometry of the setup and the proton-energy distribution.     

NIM与CIAE"60 Co-γ射线空气中照射量率的比较测量"

本文介绍2001年3月27日至3月30日中国计量科学研究院(简称NIM)与中国原子能研究院(简称CIAE)分别利用标称体积为30cm3的石墨空腔电离室在中国计量科学研究院的60Co-γ射线辐射场进行60Co-γ射线空气中照射量率的绝对测量,其结果在0.4%以内吻合.NIM对CIAE的电离室的校准因子Nx值与日本国家标准电子技术综合实验室(简称ETL)的校准因子在0.41%吻合.     

Evaluation of large deuterated scintillators for fast neutron detection (E=0.5-20 MeV) using the D(d,n)He, C(d,n) and Al(d,n) reactions

The response of large deuterated liquid scintillators (up to 10 cm diameter by 15 cm) to neutrons 0.5-20 MeV has been studied using the 2.5 MeV neutron generator at the University of Michigan, and the d(d,n), ¹³C(d,n), ²⁷Al(d,n) and other reactions at the University of Notre Dame FN tandem accelerator. The latter utilize 9 and 16 MeV deuteron beams including a pulsed beam, which permitted time-of-flight measurements. Combining pulse-shape discrimination and time-of-flight allows gating on specific neutron energy groups to determine the detector response to specific neutron energies. This will permit accurate simulation of the detector response functions for applications of these detectors in nuclear research and homeland security applications.     

Developments for a New Spectral Irradiance Scale at the National Institute of Standards and Technology

Recent developments for a new spectral irradiance scale realization at the National Institute of Standards and Technology have been targeted to reduce the present relative expanded uncertainties of 0.67 % to 4.34 % (coverage factor of k = 2 and thus a 2 standard deviation estimate) in the spectral irradiance scale to 0.17 % for the range from 350 nm to 1100 nm. To accomplish this goal, a suite of filter radiometers calibrated using NIST’s high accuracy cryogenic radiometer have been used to measure the temperature of a high-temperature black-body. A comparison of the filter radiometer calibrations with the spectral irradiance scale along with an evaluation of the black-body calibration technique have been performed. With the aid of a monochromator, the calibrated filter radiometers will then be utilized to calibrate primary and secondary spectral irradiance standard lamps at NIST.     

Characterisation of a neutron beam available at the RPI using a set of Bonner spheres

The use of Bonner spheres to characterise radiation fields is abundantly documented in the literature. This study, carried out using the state-of-the-art Monte Carlo code MCNPX and the deconvolution program MAXED, aims to characterise the RPI epithermal neutron beam using of a set of Bonner spheres of different radii surrounding a 3He detector. The energy range of interest in this study covers from thermal to 10 MeV. This purely computational study aims to assess the feasibility of using the method previously mentioned to improve the knowledge of the energy and intensity characteristics of the epithermal beam.     

Development of a three-stage, light-gas gun at the University of Dayton Research Institute

An elusive goal of the hypervelocity impact community has been the evaluation of the ballistic response of space hardware to impact velocities ranging from 8 to 11 km/s using projectiles with known properties. The design, development, and use, during the 1960s, of a three-stage, light-gas gun at McGill University is reviewed. The developers of this gun claim that they were able to launch cylindrical, 12.7-mm-diameter Lexan disks with masses of 1.5 and 1.1 g to velocities of 9.6 and 10.5 km/s, respectively. This paper presents the results of an internally funded program at the University of Dayton Research Institute (UDRI) to duplicate the published performance of the McGill University launcher. A support structure and various components of a third stage which used an 8.1-mm-diameter launch tube were added to the UDRI 75/30-mm, two-stage, light-gas gun, making the arrangement of the components similar to the one used by McGill University. Work on the development of the UDRI three-stage, light-gas gun is a continuing effort, with the goal of successfully launching small diameter (3 mm or less) aluminum spheres to velocities in excess of 9 km/s. To date, the highest projectile velocity achieved with the UDRI three-stage, light-gas gun has been 8.65 km/s.     

Realization of a scale of absolute spectral response using the National Institute of Standards and Technology high-accuracy cryogenic radiometer

Using the National Institute of Standards and Technology high-accuracy cryogenic radiometer (HACR), we have realized a scale of absolute spectral response between 406 and 920 nm. The HACR, an electrical-substitution radiometer operating at cryogenic temperatures, achieves a combined relative standard uncertainty of 0.021%. Silicon photodiode light-trapping detectors were calibrated against the HACR with a typical relative standard uncertainty of 0.03% at nine laser wavelengths between 406 and 920 nm. Modeling of the quantum efficiency of these detectors yields their responsivity throughout this range with comparable accuracy.     

Techniques for vector analyzing power measurements of the H( , np)n breakup reaction at low energies

Experimental methods to measure the vector analyzing powers over a broad range of kinematic configurations in the n-d breakup reaction have been developed at TUNL. These techniques employ the polarized beam facilities at TUNL and use the ²H( , )³He reaction as a source of low-energy polarized neutrons. Our methods permit measurements to a high statistical accuracy over a large fraction of three-nucleon phase space. The techniques are described and experimental spectra along with kinematic calculations are presented.