Nuclear Instruments and Methods最新文献

Carbon stripper foils produced by cracking hydrocarbon gases are known to have a much longer lifetime during heavy ion bombardment than foils made by the evaporation of carbon. The lifetime of cracked foils installed in the terminal of the Heidelberg MP-tandem was improved by up to a factor of 30. Crystallographic structure from electron diffraction, hydrogen content, electrical conductivity and the density have been determined to reveal characteristic differences between cracked and evaporated foils.

The São Paulo Pelletron was the first Pelletron constructed by the NEC and also the first to become operational at the end of 1971. Although the Herb Pelletron design was demonstrated from the beginning to be very good (later this was proven by the successful operation of several larger Pelletrons) our machine did suffer from defects in engineering which limited its performance and its application as a reliable tool for research in nuclear physics. This paper describes some of the improvements which we have introduced to increase the reliability of our Pelletron as a research tool in the University.

A superconducting linear accelerator booster is to be added to the existing super FN tandem Van de Graaff accelerator installation at Florida State University to achieve an effective 12 MV additional acceleration voltage. A description of this booster, the tandem modifications to accommodate it and the present status of this project are presented.

The Argonne tandem uses pelletron chains, NEC accelerator tubes, and a dual closed-corona system. Its main function is to be an injector for a superconducting linear accelerator. As long as the transverse and longitudinal emittances are within the acceptance of the linac, the output beam quality of the tandem-linac system is essentially determined by the tandem. The sensitivity of the linac to the longitudinal emittance ΔEΔt of the incident beam makes the output beam quality dependent on the negative-ion velocity distribution in the source, transit-time effects in the tandem, molecular-beam dissociation, and stripper-foil uniformity. In this paper we discuss these beam-degrading effects.

Several improvements that have been implemented in the Pelletron system are described. The main components are protective automatically closing valves at each end of the accelerator tank, pick-up wheels and corona point supports of a new design, and valves in the stripper housing. These modifications result in improved operation reliability and a minimum of service interruptions.

A description of the VICKSI computer-control system is given. It uses CAMAC modules as unique interface between accelerator devices and the computer. Through a high degree of standardisation only seven different types of CAMAC modules are needed to control the accelerator facility. The idea of having one module control one accelerator device minimizes the cabling and also the software requirements. The operation of the control system has proved to be very reliable causing less than 2% down time of the facility.

A status report of the 30 MV tandem installed at the Daresbury Nuclear Structure Facility is given. The technical aspects of the various installations are presented in detail.

A status report of the home-built 3.5 MV tandem accelerator of CISE is presented. Among the improvements, particular care has been given to the computer control of the tandem which is especially useful for the applied research which is now under way.

Since the 4th Tandem Conference in 1978 we have spent considerable effort on the reconstruction of the vacuum system of the tandem EGP-10-1 and on the construction of a Middleton type sputter source. Operational results and preliminary test results concerning the sputter source are presented.