[en] This document describes the National Bureau of Standards (NBS) calibration service 44090C (formerly 8.1R) which operates in the following way: (i) dosimetry sensors (metal foils, nuclear track detectors, wires, crystals, etc., supplied by the customer or by NBS) are irradiated to a measured neutron fluence in a fission-spectrum neutron field (for short lived reaction products, the samples are irradiated to near saturation and the fluence rate specified); and (ii) the irradiated dosimetry sensors are shipped to the customer, followed by a test report stating the fluences or fluence rates and associated uncertainties. The scope and philosophy of the service, the neutron-field characteristics, irradiation procedures, and the uncertainties in the reported neutron fluences or fluence rates are discussed. Typical maximum fluences are of the order of 3 x 10¹⁵ neutrons/sq cm, with combined (1 omega) uncertainties of + or - 2 %

[en] This document describes the NBS calibration service 44080C (formerly 8.10), which operates in the following way: (i) dosimetry sensors (metal foils, nuclear track detectors, wires, crystals, etc., supplied by the customer or by NBS) are irradiated to a certified neutron fluence in a ²⁵²Cf spontaneous fission neutron field (for short lived reaction products, the samples are irradiated to near saturation and the fluence rate specified), and (ii) the irradiated dosimetry sensors are shipped to the customer, followed by a test report stating the fluences or fluence rates and associated uncertainties. The scope and philosophy of the service, the neutron-field characteristics, irradiation procedures, and the uncertainties in the reported neutron fluences or fluence rates are discussed. Typical maximum fluences are of the order of 1 x 10¹³ neutrons/sq cm and maximum fluence rates of 10 million neutrons/cm₂ sec, with combined (1 sigma) uncertainties of + or - 1.2%

[en] Neutron depth profiling (NDP) has been employed to examine manufacturing processes and starting materials for several high-technology applications. NDP combines nuclear and atomic physics processes to determine the concentration profile of several light elements in the near surface region (∼1-8 μm) of smooth surfaces. The method is both quantitative and non-destructive. Analyses are performed at the Center for Neutron Research at NIST on samples prepared at Corning Incorporated. Two types of samples have been analyzed: (1) Boron profiles are measured in glasses to determine B loss due to its volatilization during manufacturing. Surface depletion of B is a key characteristic of borosilicate materials for both chemical vapor deposition and conventional melting processes. (2) For lithium niobate, a quantitative measure of Li concentration can differentiate congruent and stoichiometric compositions and any surface depletion in commercial wafers

[en] Properties of Ce-activated, Li-loaded glass scintillators ae discussed as well as their applications as neutron detectors. Three special problems that may arise in their use for neutron detection are nonuniformity of the ⁶Li content, multiple scattering, and afterpulsing of the photomultiplier. These problems and their consequences are discussed as well as some possible solutions

[en] The common features used in the measurement ⁶Li(n,α), ¹⁰B(n,αγ), and ²³⁵U(n,f) cross sections presented in three subsequent papers are described. The experiments were performed on the 200-m flight path of the National Bureau of Standards Linac and cover the neutron energy region from 5 to 800 keV. The neutron flux monitor was a hydrogen-filled gas proportional counter located at the end of the flight path, while the primary detectors specific to each of the three cross section measurements were placed 70 m along the flight path. The properties of the neutron source, the detailed operation of the flux monitor, the data acquisition system, and the data analysis procedure are described. The systematic errors in the neutron flux measurement are given. 6 references

[en] A detector has been designed for the detection of sub-Becquerel amounts of the radioactive xenon isotopes ^131mXe and ¹³³Xe. High efficiency has been obtained by the condensation of the sample directly onto the surfaces of two closely spaced silicon surface-barrier detectors. The measurement of the ^131mXe is based on the detection of the conversion electrons. The ¹³³Xe measurement is obtained by detection of the 81 keV photon in a NaI detector that nearly surrounds the silicon detectors. The minimum detectable activity for ¹³³Xe is 0.015 Bq. For a ^131mXe sample with no ¹³³Xe present, the minimum detectable activity is about 0.003 Bq. (orig.)

[en] This paper describes the measurement of the total neutron cross sections of carbon, ₆Li and ₇Li from 3 to 40 MeV, using the pulsed beam of the national Bureau of Standards electron linear accelerator as a source of neutrons. The measured pulse width was approximately 5 ns FWHM and the neutron flight path was approx. 150 keV at the higher energies

[en] Three different methods of flux monitoring are presented: (1) the activation foil method, (2) the fission chamber method, and (3) two techniques involving ¹⁰B. For each method, experimental problems and expected accuracies are discussed. An intercomparison of the techniques is proposed as well as comparisons with other methods. 11 refs., 1 tab

[en] An associated particle apparatus employing the T(p,n)³He reaction is now in routine use at the NBS. The apparatus consists of two target chambers with ports at 10⁰ and 25⁰ which give a useful neutron energy range of 100 keV to 1 MeV for protons from the 3 MV Van de Graaff. Electrostatic deflection, fast energy discrimination and pulsed beam time of flight techniques are used to reduce background in the neutron-associated ³He⁺⁺ pulse height spectrum to less than 1 percent. Neutron fluxes in the associated cone range between 30 and 100 n/sec at the lowest and highest bombarding energies. The spatial profile of the neutron cone is bombarded by coulomb scattering of the ³He⁺⁺ in the tritiated titanium target and has a width less than 12⁰ (full width at one-tenth maximum) for neutron energies above 300 keV. The apparatus has been used to calibrate a ''black'' detector described by Lamaze. The results of this calibration will be compared to a Monte Carlo calculation of the efficiency

[en] The shape of the ⁶Li(n,α)T cross-section curve was measured from 3- to 800-keV neutron energy. The neutrons were produced by the National Bureau of Standards 140-MeV Linac, and the measurements were made along the 200-m above-ground drift tube. The neutron flux was monitored by a 61-cm-long hydrogen gas proportional counter giving a direct ratio of the ⁶Li(n,α) cross section to the H(n,p) cross section. The ⁶Li(n,α) events were detected in a 0.5-mm-thick piece of ⁶Li glass (NE-912). The results were normalized to ENDF/B-V in the region from 10 to 400 keV. Overall uncertainties in the measurement are approx. 2% in the range from 10 to 400 keV. Error analysis and comparisons with previous measurements are given. 9 references