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This paper discusses the tolerances imposed on certain imperfections in the TRIUMF magnetic field by the resonances νx = 1/1, 2/2, 3/2 and 6/4, νz = 1/2 and νx − νz = 1, and by the height of the equilibrium orbit. A method of calculating harmonic coil settings to centre a beam of wide phase width is described.

In this paper the results of numerical investigation of transverse motion influence on time duration of the ion bunch in the isochronous cyclotron are reported. The requirements to the control degree of transverse motion parameters at beam extraction from the isochronous radius and from the region with dropping magnetic field are formulated. The ion entry into the additional bunching dee operating at the highest harmonic compared with the accelerating voltage of the main dee has been investigated. In conclusion the results of numerical modelling of the beam acceleration in the ring isochronous cyclotron with double‐acceleration system at the beam extraction from radial stability boundary are given.

In the basic tokamak experiment, the copper shell is a highly‐satisfactory feedback control device. For certain extensions of the tokamak operation — for example, to compression heating — it is, however, convenient to remove the copper shell. External feedback control of the equilibrium position is then a natural substitute. A more complex problem is the feedback stabilization of MHD modes. The interchange instabilities, against which linear magnetic feedback is ineffective, are fortunately stabilized by the minimum‐average‐B property of the toroidal tokamak. Feedback stabilization of a type of thermal instability that results in major‐radius shifts is the principal topic of this paper.

This paper describes the 80 MeV (protons) cyclotron built for the University of Louvain. The machine features variable energy and can also accelerate deuterons, 3He and alpha particles. Design and construction were completed within 40 months and first operational results are reported.

Particle accelerators have been used for some time in materials science to study the effects of irradiation damage and to implant impurity atoms to well defined concentrations. In the past the majority of this work has been of a fairly fundamental nature but recently important technological problems in connection with fast reactor development, have been highlighted. This paper will review the use of cyclotrons to study a variety of materials problems and in particular the Harwell Variable Energy Cyclotron to study the phenomenon of void formation in irradiated materials. It will illustrate how simulation experiments can help to provide an understanding of an important technological problem and furthermore provide data which can be used together with that from fast neutron irradiation to select the most suitable materials for the design of fast reactors.

According to the increasing demands for magnetic tape printing especially for video tape, the magnetic tape duplication using a contact process is one of the most attractive solutions. There are two major methods, i. e. anhysteretic transfer and thermal transfer. The coercivity of the master tape should be 2.5 times higher than the slave by computer simulation for anhysteretic transfer, but is not important for thermal transfer. The highest coercivity of the slave tape will be decided by the master tape which, in turn, is limited by the recording head saturation for anhysteretic transfer, however, the thermal characteristics of coercivity and magnetic induction under Tc are more dominant for thermal transfer. The tape surface roughness as well as the coercivity is very important for short wavelength printing. In this paper, the properties of the master and slave tapes for anhysteretic and thermal transfer are discussed with theoretical and experimental results.

This paper discusses the system developed to control the 2 MW 23 MHz RF system at TRIUMF. Included are means of pulsing through the multipactoring region; RF accelerating voltage amplitude and phase control; provision of self‐excited and driven modes of operation; fine tuning of the resonators; phase and amplitude control of third harmonic voltage for flat‐topping of the RF waveform. Results obtained with a prototype control system on the central region cyclotron are included.

This paper discusses the rationale of fast neutron therapy and presents some early results obtained at the Medical Research Council's Cyclotron Unit at Hammersmith Hospital, London. The importance of the oxygen enhancement ratio for fast neutrons is considered, together with the significance of the small proportion of anoxic cells present in most tumours. The significant features of the preliminary results obtained in patients with malignant disease are presented and the characteristics of fast neutron beams for radiotherapy are discussed.

After 20 years of operation as a conventional synchrocyclotron producing 0.4 ?A time average internal beam current of protons (increased to 1.6 ?A in 1967) of ~ 385 MeV, we stopped operation in September 1970 for the major modification for which we have been planning since 1965. The major study program and the conversion project are supported by a $ 3.9 M grant from the NSF. The conversion retains the basic cyclotron magnet (2000 tons of Fe and ~ 300 tons of Cu coils), but adds a 10-in. thick Fe band around the outside magnet perimeter to lower the return path reluctance. A new larger vacuum chamber is used, with auxilliary excitation coils. Pole iron within 30 in. of the median plane is replaced by a new configuration which includes N=3 symmetry sector iron with a small median plane gap. = 18 kG near the center and 20 kG near 80 in. radius. Strong azimuthal magnetic field flutter begins at < 2 in. radius to give strong focusing ?z, and ?r?1. We expect to obtain ~ 550 MeV proton energy, with high extraction efficiency for a 10 to 40 ?A time average external beam (~ 50% duty factor), when operation starts later this year. Additional details are given in companion papers in these Proceedings. The system will still be a synchrocyclotron and will have a 300 Hz FM repetition rate, with a new RF system, etc.