Nuclear Instruments and Methods最新文献

A second injector has been installed in front of the established one to be used mainly for heavy ion beams. The high resolution 90° analyzing magnet (M/ΔM = 100) is mounted on a rotary mount to allow for the simultaneous installation of different types of ion sources. Better ion optics of the new injector together with terminal cryopumping lead to improved transmission through the accelerator system.

Operating experience and some of the modifications introduced during the last two years are reported. During the past year the terminal voltage obtained in test runs, the voltage used during experiments and the operating efficiency of the accelerator have improved considerably. The spectrum of ions available in routine operations has been extended to include ¹⁴C, ³⁰Si, ³⁶S, ⁴⁸Ca and ⁶⁰Ni beams.

The effects of a strong earthquake on the Bucharest FN tandem are described. A brief analysis of seismic phenomena in connection with a tandem is made. The configuration of the rebuilt accelerator system and the performances of the tandem after the rebuilding are given.

The present status of the tandem project at the Laboratorio Nazionale del Sud (LNS) is described.

A 20 MV tandem accelerator laboratory is currently under construction in Argentina. The facility is planned to be completed by the end of 1982.

A new tandem accelerator laboratory is under construction at the Institute of Atomic Energy in Peking. This institute was built in 1958 and equipped with a reactor, cyclotron, electrostatic accelerator and some other facilities to meet the increasing interest in nuclear study and its application in China. The project of this tandem laboratory was approved in 1978. A 13 MV tandem accelerator will be provided by the High Voltage Engineering Corporation of Burlington, Massachusetts, USA, and a Q3D magnetic spectrometer by AB Scanditronix, Sweden. Some auxiliary systems, experimental equipment and the tank of the tandem are being designed and manufactured in China.

A report is given on the high voltage tests of the Daresbury 30 MV tandem and on the information gained on the control system and the SF₆ gas plant.

The project consists essentially in replacing the standard 72 in. tube sections by new 88 in. tube sections taking advantage both of the protrusion of the electrostatic field towards the dead sections and of the room left there. A first new 88 in. tube section has been tested separately up to 4.6 MV and in normal MP running conditions for three months. After some difficulties with broken tube glasses, the tests of the total upgraded machine are planned for May and June 1980.

The Argonne FN tandem accelerator and standard components of its experimental heavy-ion research facility have been used as a highly-sensitive mass spectrometer to detect several long-lived radioisotopes and measure their concentrations by counting accelerated ions. Background beams from isobaric nuclei have been eliminated by combining the dispersion from the energy loss in a uniform Al foil stack with the momentum resolution of an Enge split-pole magnetic spectrograph. Radioisotope concentrations in the following ranges have been measured: ¹⁴C/¹²C = 10⁻¹² to 10⁻¹³, ²⁶Al/²⁷Al = 10⁻¹⁰ to 10⁻¹², ³²Si/Si = 10⁻⁸ to 10⁻¹⁴, ³⁶Cl/Cl = 10⁻¹⁰ to 10⁻¹¹. Particular emphasis was placed on exploring to what extent the technique of identifying and counting individual ions in an accelerator beam can be conveniently used to determine nuclear quantities of interest when the measurement involves very low radioisotope concentrations. We are able to demonstrate the usefulness of this method by measuring the ²⁶Mg(p, n)²⁶ Al(7.2 × 10⁵ yr) cross section at proton energies in the astrophysically interesting range just above threshold, and by accurately determining the previously poorly known half-life of ³²Si.