High-energy Neutron Measurements Research Articles

A new Bonner-sphere set for high energy neutron measurements: Monte Carlo simulation

The usual Bonner sphere set consists of six to eight high density polyethylene spheres with diameters varying from 3 to 12 inches. Either a BF/sub 3/ counter, LiI scintillator, or /sup 3/He detector is located at the center of each sphere to detect the moderated neutrons. The responses of these spheres for high energy neutrons are very low even for the largest 12 inch sphere. To increase the response for high energy neutrons, high Z material such as Pb, W, TI, or Au can be added to the sphere to utilize the (n,xn) reaction of these materials. Monte Carlo simulations for the Pb-added case with a /sup 3/He detector as an example will be presented. The response at high energy for this case is enhanced by a factor of 5 to 8 depending upon the sphere diameter. >

High-energy neutron spectrometry with CR-39 SSNTDs

Spectrometric measurements of high-energy neutrons have been made, employing CR-39 plastic track detector. Triple-α tracks, produced by the reaction 12C(n,n′)3α have been used to measure the energy and angular distributions of the three α-prongs. Applying the energy and momentum conservation rules, the energy spectra of neutrons have been obtained.

High-energy neutron spectrometry with plastic SSNTDs

Spectrometric measurements of high-energy neutrons have been made, employing a cellulose nitrate (CA80-15) plastic track- detector. High-energy neutrons produce, amongst other things, “triple tracks” in the plastic detector by means of the reaction 12C(n, n′) 3α. By measuring the energy and angular distributions of the three α-prongs, and applying considerations of conservation of energy and momentum, the energy spectra of neutrons have been obtained.

An experiment to detect energetic neutrons and gamma rays from the sun

A payload for the detection and measurement of high energy neutrons and gamma rays from the sun was flown onboard the first Indian satelliteAryabhata. The payload system for this neutron-gamma experiment was designed for detecting energetic neutrons in the energy range 10–500 MeV and gamma rays in the energy range 0.2–20 MeV. The details of the design of the payload, various tests carried out on it as well as the preliminary in-orbit performance are presented.

Support for Crand Theory from measurements of Earth albedo neutrons between 70 and 250 MeV

The results of high energy neutron measurements during two balloon flights on May 1 and 25, 1971, from Palestine, Texas, are reported. At atmospheric depths of 8.6 and 4.7 g cm−2 we obtained the energy and angular distribution of atmospheric neutrons between 70 and 250 MeV. The upward moving part, in terms of the albedo neutron leakage current, can be described by J2π=2.53 · E−1.89 neutron/cm² s MeV in this energy range. The angular distribution of the neutron flux shows a pronounced peak in the horizontal direction (zenith angle, 90°) with a full width at half maximum of about 30°. The measured energy spectrum is in good agreement with results of recent Monte-Carlo calculations on atmospheric neutrons. Together with the angular distribution it also confirms theoretical estimates of the albedo neutron source strength required in a Crand (cosmic ray albedo neutron decay) theory where the high-energy protons in the earth's inner radiation belt are injected by decaying neutrons. The instrument used employs a double scattering technique and has been calibrated at the synchrocyclotron of the Atomic Energy Research Establishment, Harwell, England.