The production of negative polarized heavy ions and their acceleration by tandem accelerators is reviewed. Particular emphasis is given to the polarized lithium and sodium beams at the Heidelberg EN tandem. The problem of depolarization of an incompletely-stripped beam is discussed using experimental results on the beam as an example. The advantages involved in using tandems with high terminal voltages for the acceleration of polarized ion beams heavier than lithium is stressed.
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 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.
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.
The present status of the tandem project at the Laboratorio Nazionale del Sud (LNS) is described.
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 improvements are described resulting from the addition of an 8 MV tandem as a second injector for the VICKSI accelerator combination. For ion beams with masses A < 30 the limitation for high energy beams will be given by the magnetic field of the cyclotron, e.g. 32 MeV/A. The alternate use of the two electrostatic injectors will increase the available beam time. The variety of ions for acceleration with VICKSI will be enlarged considerably by use of sputter sources.
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.
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