Neutron Yield from (3-He,xn) Reactions on Thick Copper Targets

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

Calculations and measurements of the energy-dependent response of a shielded gamma-ray detector

Instruments designed to record high-intensity gamma-ray flashes must have fast time response, wide dynamic range, and good rejection of photon backgrounds at lower energies. In principle, plastic scintillators can easily provide the necessary time response and dynamic range; like other photon detectors, however, they must be carefully shielded to reduce their low-energy sensitivity. This shielding is often complicated by the need to use different optical sensors to cover the full dynamic range, which each sensor requiring a separate opening through the shielding. In this detector, a high-sensitivity photomultiplier tube handles low-intensity signals, and a silicon photodiode covers high intensities. These electronic components, particularly the diode, may also respond directly to incident radiation, so localized shielding must be provided. To reduce the detector`s total mass, the scintillator and photodiode are enclosed in a relatively thick, tight-fitting inner shield, which is surrounded by a thin outer shield to reduce the leakage through any gaps. Although efficient, this arrangement demands careful design and testing. This report describes such an analysis, which uses Monte Carlo simulations to develop a comprehensive model of the detector at photon energies from threshold to above 10 MeV. Included are discussions of the fundamental responses of the unshielded silicon diode and plastic scintillator, explanations of the effectiveness of different shielding materials, studies of calibration sources, and comparisons with laboratory tests

Atmospheric transport of neutrons and gamma rays from near-horizon nuclear detonations

This report continues a study of the transport of neutrons and rays from nuclear detonations at high altitudes to a set of detectors, with an emphasis on the limiting case of sources even beyond the horizon. To improve the calculational efficiency, the standard arrangement of a single source with multiple detectors is transformed to an equivalent one with a single detector and sources at multiple locations. Particular attention is paid to the critical problem of transport at near-horizon angles in an atmosphere whose density decreases exponentially with altitude. As a check, calculations for this region are made using both analytical and Monte Carlo approaches. For sources approaching the horizon, the fluence of gamma rays and neutrons reaching the detector drops gradually as the increasing column density attenuates the direct, unscattered fluence. Near the grazing angle, the direct fluence plummets, but the scattered component continues to decrease slowly and remains observable. Over this range, the timedependent flux of direct-plus-scattered gamma rays changes dramatically in both shape and magnitude, but it probably remains distinct from typical natural backgrounds. The neutron time-of-flight spectrum is dominated by scattering and reflects only the most important aspects of the original source spectrum; its most obvious features are a prominent low-energy tail and the resonance structure produced by nuclear interactions in the atmosphere. In some cases, the fluence of secondary gamma rays produced by these interactions may be larger than that from the source itself

Calibration of the Neutron Detection Efficiency of the COMPTEL NE213 Detector

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

Measurements of the (n,p) Reaction at IUCF

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

Status of the Search for Charge Symmetry Breaking in n-p Scattering

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

Preequilibrium Neutron Emission in (p, xn) Reactions with 80-160 MeV Projectiles

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

Study of (n,p) Reactions Between 100 and 200 MeV

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

Progress on the Charge-Symmetry-Breaking Experiment

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

A Measurement of C_NN in n-p Scattering at 188 MeV

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440