L. Grodzins

Scanning Proton-Induced X-ray Microspectrometry in an Atmospheric Environment

Collimated million-electron-volt proton beams, brought out into air, can be used as a scanning microprobe to examine specimens with a spatial resolution of the order of 1 micrometer. Trace elements at concentrations as low as 1 part per million can be detected. Some preliminary results based on the use of this simple method are presented.

Nuclear techniques for finding chemical explosives in airport luggage

Abstract Chemical explosives are composed of concentrated densities of nitrogen and oxygen. High values of the nitrogen alert the presence of a bomb; high values of both nitrogen and oxygen densities certify the bombs presence uniquely. More than a dozen nuclear-based techniques have been proposed for rapidly scanning airport luggage to find hidden explosives by measuring these elemental distributions. In almost every scheme, the technological challenge is the accelerator, which must be small, well-shielded, cost-effective, and be operable in busy airports by nominally-trained personnel, with minimum unscheduled downtime for repairs or service. This paper will summarize, within the limits imposed by security, four of the imaging schemes.

Gamma-Ray Measurements of a Soviet Cruise-Missile Warhead

A portable germanium detector was used to detect gamma-ray emissions from a nuclear warhead aboard the Soviet cruiser Slava. Measurements taken on the missile launch tube indicated the presence of uranium-235 and plutonium-239—the essential ingredients of nuclear weapons. With the use of this equipment, these isotopes probably could have been identified at a distance of 4 meters from the warhead. Such inspections do not reveal detailed information about the design of the warhead.

Computer calculations of solenoidal focussing of MeV proton beams to one micrometer diameter

Abstract A superconducting solenoid lens for focussing proton beams up to 5 MeV to the order of one micron is installed on a scanning proton microprobe facility. The expected performance of the lens including the effects of the spherical, chromatic and mechanical aberrations, on the resolution and throughput, studied by ray trace computer calculations is described.

PROPOSED RECOIL MASS SPECTROGRAPH FOR DETECTING SUPERHEAVY NUCLEI.

Abstract A new type of mass spectrograph is being proposed for separating and identifying nuclei recoiling from a thin target bombarded with heavy ions. The scheme is aimed principally at superheavy nuclei produced in fusion reactions, e.g., 62154Sm + 52130Te, but it can also be used for lighter elements, e.g., for detecting proton-rich nuclei, such as products of the reaction 2040Ca + 2040Ca. The apparatus planned consists of a crossed-field velocity selector, deflecting horizontally, followed by a broad-range magnetic spectrograph deflecting vertically. The combination produces two-dimensional focusing and velocity focusing so that particles with constant M/q fall on sharp slanted lines on the detector with a relatively good mass resolution, independent of target thickness and beam homogeneity. The advantage of this scheme over a conventional Nier-type mass spectrograph for this purpose is that it can handle a large range of charge states of the recoiling nuclei. Preliminary plans for also determining Z of the recoiling nuclei include stopping-power or range measurements and detection of chatacteristic X-rays emitted either in the stopping process or following decay.

Hyperfine interactions on 237Np and 239Np implanted into copper and nickel

Abstract Alpha-gamma perturbed angular correlations after recoil implantation have been used to study the hyperfine interactions acting on neptunium isotopes in metals. The interaction in coper is shown to be nonstatic and is probably of quadrupole character. The effective magnetic hyperfine field on 239 Np in nickel has been determined to be −0.170 ± 0.040 MOe.

Measurements of equilibrium charge states of Br, I, Ta and U up to about 200 MeV☆

Abstract The charge distribution of Br, I, Ta and U ions passing through carbon foils and certain gases has been determined. The most probable charge versus projectile energy is presented for E proj up to ∼ MeV. The data can be used directly to predict the energy spectrum versus terminal potential for an electro-static accelerator.

Antiproton production in 14.6 AGeVc Si+A collisions

Abstract Antiproton production cross sections have been measured for minimum bias and central Si+Al and Si+Au collisions at 14.6 A GeV c . The data presented cover the range of transverse momentum from 0.3 to 1.2 GeV c and lab rapidities from 1.1 to 1.7 units. The relative p π − and p K − yields are found to be the smallest for the heaviest system measured, central Si+Au collisions. For these collisions, the p π − ratio, determined from integrated yields for 1.1⩽y⩽1.7, is (0.84±0.07)×10−3. In the same rapidity interval, the average antiproton inverse m⊥ slope is 141±14 MeV for central Si+Al and central Si+Au collisions.

Measurement of the quadrupole moments of the first 2+ states of 130Ba and 134Ba

Abstract The quadrupole moments of the first 2 + states of 130,134 Ba were measured using the reorientation precession technique. Prolate deformations were determined for both nuclei. The quadrupole moments found were Q = −0.33 ± 0.24 b and −0.31 ± 0.24 b for 130 Ba and 134 Ba, respectively.

HYPERFINE MAGNETIC FIELDS AT THORIUM AND URANIUM NUCLEI IN IRON METAL.

Abstract The perturbation of the α-γ angular correlation after recoil implantation has been measured for the 2 + states of 228 Th and 234 U implanted into copper and iron metals. Substantial precessions and attenuations are observed in time-integral measurements. Assuming theoretical g -factors and the applicability of the Abragam-Pound theory for combined interactions, the hyperfine magnetic fields in iron are H Th (Fe) = − 0.31 ± 0.06 MOe and H U (Fe) = −0.56 ± 0.16 MOe.