Gary L. Jensen

A neutron coincidence spectrometer

Abstract We have developed a spectrometer for MeV neutrons that relies upon total energy absorption to measure neutron energy. A coincidence signal is required from the capture of thermalized neutrons in Li-6 glass scintillators incorporated in the detector body. This dual signal from a single neutron provides a powerful means of discrimination against background events arising either from gamma rays or from ambient, low-energy neutrons. The spectrometer is particularly useful in situations in which the neutron source intensity is very low.

A compact neutron coincidence spectrometer, its measured response functions and potential applications

Abstract A one-liter “coincidence spectrometer” utilizing plastic scintillator and three 6 Li-glass plates has been calibrated at five neutron energies between 1.2 and 14.1 MeV, and the response functions are given. The features of this spectrometer, including the ability to operate with essentially no cross talk between multiple detectors, suggest several important potential applications, such as the neutron detector in π-d capture experiments to measure the nn scattering length, as well as other experiments involving multiple-neutron sources, spontaneous-fission detection, and dosimetry. The spectrometer is also compared with other current neutron spectrometer systems.

Gamma-ray sensitivity of 6Li-glass scintillators

Abstract The gamma-ray response of thin NE 905 6Li-glass scintillators is studied as a function of gamma-ray energy, scintillator thickness, and detector resolution. The probability for a gamma ray to simulate a neutron event is measured at three gamma-ray energies for three scintillator thicknesses. The feasibility of using coincidence information from electrons that diffuse out of the glass to reduce gamma-ray caused background is also studied.

Anomalous nuclear reactions in condensed matter: Recent results and open questions

We have observed clear signatures for neutron emission during deuteron infusion into metals, implying the occurrence of nuclear fusion in condensed matter near room temperature. The low-level nuclear phenomenon has been demonstrated in collaborative experiments at Brigham Young University, at the Gran Sasso laboratory in Italy, and at the Los Alamos National Laboratory. We have shown that neutron emission can be induced in metals using both electrochemical and variational temperature/pressure means to generate non-equilibrium conditions. Observed average neutron emission rates are approximately 0.04–0.4 no/s. Current efforts focus on trying to understand and control the phenomenon. In particular, we wish to understand the correlation of neutron yields with parameters such as hydrogen/metal ion ratio, pressure (induced, for example, by electrical field or gas pressure or mechanical pressure), temperature variation, hydride phase changes, and surface conditions, e.g., a palladium coating on titanium. We want to know if fusion arises due to the close proximity of the deuterons in the lattice (piezonuclear fusion), or possibly from “microscopic hot fusion”, accompanying strong electric fields at propagating cracks in the hydride. The latter interpretation would imply neutron emission in bursts. Our experiments show clear evidence for emission of ∼102 neutrons in bursts lasting <128 μs, although random neutron-singles emissions were also observed. Experiments now underway to compare thed−d, andp−d, andd−t reaction rates will be important to a consistent description of the new phenomenon. Careful scrutiny of this effect could increase our understanding of heat, helium-3, and tritium production in the earth, other planets, and even the stars.

High-efficiency fast-neutron detectors

Abstract Two high-efficiency detectors for fast neutrons are described. The first detects bursts of neutrons as well as single neutrons. The second is a neutron spectrometer with burst-mode capabilities. Both instruments require a signal from neutron energy loss in a moderating scintillator followed by a signal from neutron capture in 6Li. All potentially interesting events are recorded by a waveform digitizer for detailed analysis and background subtraction. Time dispersion of the capture signals makes possible an estimate of the number of incident neutrons in the burst. The spectrometer has been calibrated at four neutron energies from 1.2 to 14.1 MeV.

In quest of a trigger mechanism for neutron emissions from deuterium/solid systems

The triggering of neutron emission in electrolysis experiments has not been achieved. (AIP)

First experimental results at the gran sasso laboratory on cold nuclear fusion in titanium electrodes

We present here the first results obtained at the Gran Sasso Laboratory on the neutron emission following the electrolytic infusion of deuterons into titanium electrodes. The measurements were carried out under a 4000-m water equivalent rock thickness, i.e., in an extremely reduced cosmic-radiation background. The neutrons were detected by proton-recoil liquid scintillation detectors, allowing a huge reduction of the local gamma-ray background. The results obtained provide a neutron emission rate comparable in size to the one recently reported by Joneset al. in an electrolysis experiment performed with a different apparatus in ordinary laboratory conditions. They provide more evidence in favor of low-level cold nuclear fusions in metals.

A moderating 6Li-glass neutron detector

Abstract A neutron detector with good detection efficiency in the neutron-energy range up to 1 MeV has been built using 2 mm thick 6 Li-glass plates immersed in a moderating liquid. The detector is compact, reasonably insensitive to gamma rays, and relatively fast.

Multiple scattering of protons and deuterons by thick foils

Abstract Protons and deuterns from the Triangle Universities Nuclear Laboratory (TUNL) tandem Van de Graaff of energies 3.0, 4.0, and 5.0 MeV were scattered from foils of Al, Ni, Mo, and Ta having thicknesses from 6.14 to 47.2 mg/cm 2 . Multiple-scattering angular distributions were measured using a position-sensitive detector to collect data at nine different angles simultaneously. Modified Gaussian curves were fitted to the points of the distributions, and the angles where the distribution falls to 1 e , 1 10 , and 1 100 of its central value are presented. The 1 e data points are compared with calculations using a traditional method of determining multiple-scattering angular distributions. An empirical correction for extending the traditional method into the low-energy and thick-foil region considered here is suggested.

Multiple Scattering of Protons and Deuterons by Thick Foils

Protons and deuterons from the Triangle Universities Nuclear Laboratory (TUNL) tandem Van de Graaff of energies 3.0, 4.0, and 5.0 MeV were scattered from foils of Al, Ni, Mo2, and Ta having thicknesses of 6.14 to 47 mg/cm2. Multiple scattering angular distributions were measured using a position-sensitive detector to collect data at nine different angles simultaneously. Gaussian curves were fitted to the central points of the distributions and the ¿1/e angles thus derived are presented graphically. The data points are compared with calculations using a common method of determining multiple scattering angles. An empirical correction for extending this method into the low energy and thick foil region considered here is suggested.