摘要:

Ray Herb’s career in the development of electrostatic accelerators spans 65 years. He began in 1933 by pressurizing a Van de Graaff generator, for the first time. Over the next six years, the group at the University of Wisconsin, under his direction, developed the fundamentals of equipotential rings, potential grading, corona triode control, and other basic mechanisms for the practical use of electrostatic accelerators while making fundamental contributions to experimental nuclear physics. This group held the world’s record in sustaining potential difference of 4.5 MV. During World War II, he worked on radar at the Radiation Laboratory. After the war, Herb resumed his career with further fundamental contributions including metal/ceramic bonding, ultrahigh vacuum pumping, negative ion source development and metal charge carriers. The company, National Electrostatics, under his direction manufactured the accelerator which still holds the world’s record for the highest sustained potential difference of32±1.5&hthinsp;MV.Throughout his career he led teams which made the electrostatic accelerator a valuable tool for applications in a wide variety of scientific fields, well beyond nuclear physics. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58961

出版商:AIP    

年代:1999

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.58971

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Prof. Ray Herb pioneered the concept and design of the tandem Pelletron accelerator in the late sixties at NEC. The 15UD Pelletron at Nuclear Science Centre (NSC), upgraded for 16MV operation using compressed geometry accelerating tubes is the last such large Pelletron. It has unique features like offset and matching quadrupoles after the stripper for charge state selection inside the high voltage terminal and consequently the option of further stripping the ion species of the selected charge states at high energy dead section, and elaborate pulsing system in the pre-acceleration region consisting of a beam chopper, a travelling wave deflector, a light ion buncher (1–80 amu) and a heavy ion buncher (>80 amu). NSC was established as a heavy ion accelerator based inter university centre in 1985. It became operational in July 1991 to cater to the research requirements of a large user community which at present includes about fifty universities, twenty-eight colleges and a dozen other academic institutes and research laboratories. The number of users in Materials and allied sciences is about 500. Various important modifications have been made to improve the performance of the accelerator in the last seven years. These include replacement of the corona voltage grading system by a resistor based one, a pick-up loop to monitor charging system performance, conversion from basic double unit structure to singlet, installation of a spiral cavity based phase detector system with post-accelerator stripper after the analyzing magnet, and a high efficiency multi harmonic buncher. Installation of a turbo pump based stripper gas recirculation system in the terminal is also planned. A brief description of utilization of the machine will be given. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58972

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The history of electrostatic accelerators has been punctuated by a series of projects in which innovative designs have failed to meet the expectations of their designers. From the early, air-insulated Van de Graaffs at Round Hill to certain of the large pressurized heavy ion accelerators of the 1970s and 1980s, increases in size or changes in design and materials have not always led to the maximum voltages expected or extrapolated. Since these failures have continued beyond childhood into a mature technology, it is reasonable to assume that the causes of voltage limitation are varied and complex. They have remained poorly understood for a number of reasons: resources for an extended program of research into breakdown and failure of electrostatic generators have always been meager, especially for large machines devoted to nuclear research; the inaccessibility of pressurized generators makes instrumentation difficult and testing slow; the calculation of transient and dynamic effects is laborious and the results difficult to verify; voltage test experiments on operating accelerators are inhibited by the significant risk of damage due to energy release on breakdown: and the total voltages (though not the local fields) achieved in many electrostatic accelerators exceed those produced in any other man-made environment. In this review, the behavior of several generators of different designs is examined in order to assess the importance of the various design features and operating conditions that control the maximum voltage achievable in a working machine. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58966

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

TRIUMF and Northrop Grumman have developed a new system for the detection of concealed explosives and drugs. This Contraband Detection System (CDS) is based on the resonant absorption by14Nof gammas produced using13C(p,&ggr;)14N.The chosen reaction uses protons at 1.75 MeV and the gammas have an energy of 9.17 MeV. By measuring both the resonant and the non-resonant absorption using detectors with good spatial resolution, and applying standard tomographic techniques, we are able to produce 3D images of both the nitrogen partial density and the total density. The images together may be utilized with considerable confidence to determine if small amounts of nitrogen based explosives, heroin or cocaine are present in the interrogated containers. Practical Gamma Resonant Absorption (GRA) scanning requires an intense source of protons. However this proton source must also be very stable, have low energy spread, and have good spatial definition. These demands suggested a tandem as the accelerator of choice. We have therefore constructed a 2 MeVH−tandem optimized for high current (10 mA) operation, while minimizing the overall size of the accelerator. This has required several special innovations which will be presented in the paper. We will also present initial commissioning results. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58973

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Modern electron cyclotron resonance ion source (ECRIS)s are able to produce intense beams of highly charge positive ions, of which charge states are higher than those obtained from electron stripping at the high voltage terminal of tandem accelerators. It is possible to increase beam intensity, beam energy and beam species by utilizing an ECRIS in a tandem accelerator. A small permanent magnet ECRIS has been installed in the high voltage terminal of the vertical and folded type 20UR Pelletron tandem accelerator at Japan Atomic Energy Research Institute at Tokai. Acceleration tests have been successfully carried out with beams ofH+,N2+,O3+,5+,Ar6+,8+,9+and132Xe12+,13+ions. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58974

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The Chalk River Laboratories of Atomic Energy of Canada Ltd. was a major centre for Accelerator based physics for the last fifty years. As early as 1946, nuclear structure studies were started on Cockroft-Walton accelerators. A series of accelerators followed, including the world’s first Tandem, and the MP Tandem, Superconducting Cyclotron (TASCC) facility that was opened in 1986. The nuclear physics program was shut down in 1996. This paper will describe some of the highlights of the accelerators and the research of the laboratory. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58975

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

A summary of the ten years’ operation of the HI-13 tandem accelerator at CIAE is presented. The particular emphasis is put on the improvements on the laddertron and high voltage divider resistor system. Some statistics on the machine operation and maintenance are also given. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58976

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The Munich MP tandem accelerator is in operation since 1970. Now it is equipped with a NEC Pelletron charging system and HVEC stainless steel tubes. The negative ion injector and the high energy extension with the analyzing system were completely reconstructed. Also the instrumentation was improved continuously. The tandem is used in an increasing degree not only for nuclear and atomic physics, but also for biological and material science work. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58969

出版商:AIP    

年代:1999

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.58977

出版商:AIP    

年代:1999

数据来源: AIP