Showing papers on "Linear particle accelerator published in 1979"

Variable energy standing wave linear accelerator structure

Abstract: Variable energy selection is accomplished in a side cavity coupled standing wave linear accelerator by shifting the phase of the field in a selected side coupling cavity by π radians where such side coupling cavity is disposed intermediate groups of accelerating cavities. For an average acceleration energy of E 1 (MeV) per interaction cavity, and a total number of N interaction cavities, the total energy gain is E 1 (N-2N 1 ) where N 1 is the number of interaction cavities traversed beyond the incidence of the phase shift. The phase shift is most simply accomplished by changing the selected side cavity configuration mechanically in repeatable manner so that its resonant excitation is switched from TM 010 mode to either TM 011 or TEM modes. Thus, the total energy gain can be varied without changing the RF input power. In addition, the beam energy spread is unaffected.

Linear induction accelerators made from pulse-line cavities with external pulse injection.

Abstract: Two types of linear induction accelerator have been reported previously. In one, unidirectional voltage pulses are generated outside the accelerator and injected into the accelerator cavity modules, which contain ferromagnetic material to reduce energy losses in the form of currents induced, in parallel with the beam, in the cavity structure. In the other type, the accelerator cavity modules are themselves pulse‐forming lines with energy storage and switches; parallel current losses are made zero by the use of circuits that generate bidirectional acceleration waveforms with a zero voltage‐time integral. In a third type of design described here, the cavities are externally driven, and 100% efficient coupling of energy to the beam is obtained by designing the external pulse generators to produce bidirectional voltage waveforms with zero voltage‐time integral. A design for such a pulse generator is described that is itself one hundred percent efficient and which is well suited to existing pulse power techniq...

Photon contamination in 8-20-MeV electron beams from a linear accelerator.

Abstract: The amount of x-ray contamination near the surface of a phantom irradiated with electron beams was measured directly. Measurements were done to ascertain if photon contamination in the beam contributes a higher dose to the more superficial layers of an irradiated medium than indicated by conventional methods. A 1.4-kG magnetic field was used to deflect the electron beams generated by a Philips SL/75-20 linear accelerator. The electron energies studied were 8, 10, 12, 14, 17, and 20 Mev. After sweeping the electron beam, a significant amount of photon contamination was measured in all cases. The characteristic qualities of the photon contamination were measured directly in a water tank. They were found to agree with those of bremsstrahlung spectra generated in a thin target with a virtual source at the location of the scattering foil.

Proceedings of the 1979 linear accelerator conference

Abstract: s of individual items from the conference were prepared separately for the data base. (GHT)

Induction Linear Accelerators and Their Applications

Abstract: A growing number of applications of particle accelerators require combinations of beam current, beam energy, and beam quality which are not readily achieved with conventional types of particle accelerators. Induction linear accelerators promise to fill some of these needs. A general description is presented of linear induction accelerator principles, various types of linear induction accelerators and their status, and possible future developments.

Space-charge limits for linear accelerators

Abstract: Equations are developed which determine the space-charge limits for a generalized linear accelerator. A single parameter k, the ratio of space charge to restoring forces, is the only unknown parameter. Experience and computer simulations indicate that k approx. = 0.5.

Stability of Intense Transported Beams

Abstract: At the previous National Accelerator Conference, the transport of intense ion beams, with particular reference to Heavy Ion Fusion, was analyzed by finding matched solutions of the coupled envelope equations. l) This work established relations between lattice structure, beam dimensions and space-charge tune depression as a function of intensity. In this paper we report on an investigation of the stability of the K-V distribution in transport by a periodic quadrupole system, a generalization of Gluckstern's analysis for a continuous solenoid 2) The results are presented and compared with simulation computations for a particular case; the results provide a prediction of maximum transportable current without degradation of emittance due to instability.

Design/Cost Study of an Induction Linac for Heavy Ions for Pellet-Fusion

Abstract: The physics of the pellet implosion sets stringent conditions on the accelerator driver. The beam energy should be > 1 MJ, the beam power > 100 TW (implying a pulse length approx. = 10 ns), and the specific energy deposition in the pellet > 20 MJ/g. Thus, considerable current amplification is required, e.g. from some 10 amps at the source to perhaps 10 kiloamps at the pellet. Most of this amplification can be accomplished continuously along the accelerator and the remainder achieved at the end by bunching in the final transport lines to the target chamber. A conceptual schematic of an Induction Linac Fusion Driver is shown, which includes an injector, an accelerator-buncher, and a final transport system. Here only the accelerator portion of the driver is discussed.

High Current Linear Ion Accelerators Utilizing Electron Neutralization

Abstract: The transport and post-acceleration of multikiloampere ion beams is being studied at Sandia Laboratories for application to inertial fusion. A number of projects have been carried out over the past year, including theoretical investigation of non-linear beam transport, rapid space charge neutralization of ion beams by electrons emitted from boundaries, and longitudinal instabilities of pulseline driven linear accelerators. In the experimental part of the program, injectors have been developed which can deliver 10 kA of protons and 2 kA of carbon ions (at 100-200 keV) for microsecond pulse durations. These beams have been post-accelerated in a magnetically insulated acceleration gap. By suitably shaping the electrostatic gap boundaries, focusing of the beams has been demonstrated.

The First Year of Operation at the Heidelberg Heavy-Ion Postaccelerator

Abstract: The 3MV stage of the Heidelberg Heavy Ion Postaccelerator being the first one to use the independent phasing concept of short linear accelerator cavities in a booster application behind an MP-Tandem accelerator, went into operation in December 1977 and is in the state of full user-availability since May of 1978. The machine uses spiral resonators at room temperature. Ten such resonators with design velocity s0 = 0.10 at 108.48 MHz are operated either in CW at 20 kW or in pulsed mode (df = 0.25) at 80 kW. Due to the flexibility of the independent phasing of the 10 resonators presently in operation, acceleration voltages as high as 3.3 MV (CW) could be demonstrated for ions between 12C and 58Ni. 5.5 MV have been achieved in pulsed operation. An energy resolution of ?E/E2 4 . 10-4 allowing rebunched pulse widths of ?tFWHM < 70 ps could be measured, showing the tandem like beam quality. The machine is exclusively computer controlled, prerequisite for the operation of the many parameters of a tandem-postaccelerator-combination. The overall availability of the postaccelerator together with the MP Tandem was above 80% of the scheduled user beam time. The operation of the 3 MV stage will be interrupted for a 4 months' shutdown late 1979 to allow for the extension of the machine to its full 10 MV (CW) acceleration voltage by the addition of 20 more spiral resonators.

Construction of a Cerenkov light source.

Abstract: A radiationsource has been developed and implemented from Cerenkov emission that is intended to provide an intense continuum from the infrared to 600 A. Parasitic use of the primary electron beam at the Stanford Linear Accelerator Center (SLAC) together with a novel optical geometry for light collection can give a focused and tunable ultraviolet beam with 104 kW/m2⋅sr brightness, 10−2spectral purity, and with the pulsed, 5 ps time structure of the SLAC electron beam. Measurements of emission characteristics in the visible part of the spectrum correlate closely with the predicted performance.

A Proposed RF System for the Fusion Materials Irradiation Test Facility

Abstract: Preliminary rf system design for the accelerator portion of the Fusion Materials Irradiation Test (FMIT) Facility is in progress. The 35-MeV, 100-mA, cw deuteron beam will require 6.3 MW rf power at 80 MHz. Initial testing indicates the EIMAC 8973 tetrode is the most suitable final amplifier tube for each of a series of 15 amplifier chains operating at 0.5-MW output. To satisfy the beam dynamics requirements for particle acceleration and to minimize beam spill, each amplifier output must be controlled to ±1° in phase and the field amplitude in the tanks must be held within a 1% tolerance. These tolerances put stringent demands on the rf phase and amplitude control system.

Properties of a linac-storage ring stretcher system

Abstract: Some of the design characteristics and costs of a matched system comprising a pulsed linac and a storage ring to be used as a beam stretcher are discussed. The goal is to obtain a 2 GeV, 0.1 mA quasi-continuous stream of electrons. Within this goal, some optimization criteria will be examined and some technological difficulties will be indicated.

Progress Report on Testing of a 100-kV 125-mA Deuteron Injector

Abstract: The Linear Accelerator to be used for the Fusion Materials Irradiation Test Facility (FMIT) will require an injection energy of 100 keV at a dc current level of 125 mA. Studies are being made on a pre-prototype version of this injector, including performance tests of both a single aperture reflexarc ion source and a cusp-field source. A single stage, high-gradient extraction system is used prior to mass analysis in a 90° bending magnet. A two-stage beam steering device to measure beam emittance under full beam power has been designed and constructed. To avoid production of neutrons, all prototype tests are run with H2+ ions rather than D+ ions.

Operational Experience with Coupled-Cavity Structures in a High Duty Factor Accelerator

Abstract: The Chalk River Electron Test Accelerator is a facility to study beam behaviour in a multi-tank accelerator and to develop control systems for high power operation. Two standing-wave structures have been operated at energy gradients of 0.75 MeV/m and their accelerating fields held constant under 50% beam loading. During start-up, the control systems must accommodate resonant frequency shifts exceeding ten bandwidths in both of the dissimilar structures and their resonant frequencies must differ by less than a tenth of a bandwidth before locking to the accelerator frequency. The central mini-computer controls the run-up and among other things controls the structure temperature.

Desicn and status of an experimental superconducting linear accelerator for electrons

Abstract: We report on the design and status of a small superconducting linear accelerator for electrons in the 3 MeV range. It is operated at 8 GHz. Primary goals are: a high energy gradient by choosing a high frequency, a working temperature of 4.2 K by using Nb3Sn, and to gain information about the performance of multicell structures at 8 GHz. At present the 80 keV electron gun, the vacuum beam line, and the cryostat are set up. A three cell Nb3Sn covered cavity was used for the first experiment with the accelerator and a beam of 1 μA was accelerated to 160 keV. The performance of four 30-cell Nb-accelerating structures operated in the π/2-mode and the observed field limitations around 2 MV/m are analysed. Higher field values (up to 8.8 MV/m) were achieved in structures of a smaller number of cells.

A Proposed Multi-Purpose Separated-Sector Cyclotron at IPCR

Abstract: A new research facility including an accelerator complex to provide all heavy ions up to uranium has been proposed at the Institute of Physical and Chemical Research. A separated-sector cyclotron (SSC) with K=620 MeV is being designed as a booster accelerator for a variable-frequency heavy-ion linac now under construction. For the injection of relatively light ions up to neon into the above SSC, the existing ordinary cyclotron will be converted into an AVF machine with K=90 MeV to be used as another preaccelerator. The maximum beam energy provided by this accelerator system will range from 120 MeV/u for fully stripped ions to 15 MeV/u for very heavy ions such as uranium. Acceleration of light particles like deuterons and ? particles is also possible. The basic design and some model studies of the proposed machine are described.

Linac Particle Tracing Simulations

Abstract: A particle tracing code was developed to study space-charge effects in proton or heavy-ion linear accelerators. The purpose is to study space-charge phenomena as directly as possible without the complications of many accelerator details. Thus, the accelerator is represented simply by harmonic oscillator or impulse restoring forces. Variable parameters as well as mismatched phase-space distributions were studied. This study represents the initial search for those features of the accelerator or of the phase-space distribution that lead to emittance growth.

Initial Operation of the Fermilab Antiproton Cooling Ring

Abstract: The "cooling" of protons by electrons has been studied by the accelerator group at the Institute of Nuclear Physics at Novosibirsk, U.S.S.R.l. They have achieved damping of proton-betatron oscillations by Coulomb interactions with "cold" electrons as described by simple theory. They also observe fast damping when the longitudinal velocities of all the protons and electrons are very nearly the same and the electrons are trapped in a longitudinal magnetic field. This effect results from the extended interaction between the same electrons and protons.

RF power manifold for the radio frequency quadrupole linear accelerator

Abstract: The properties of rf power manifolds for use in a radio frequency quadrupole accelerator are discussed in the context of a coupled-circuit model. (GHT)

Parametrisation of linear accelerator electron beam for computerised dosimetry calculations.

Abstract: The authors have adapted the age-diffusion model proposed by Kawachi (ibid., vol.20, p.571 (1975)) and later modified by Steben, Ayyangar and Suntharalingam (1977) to parametrise the Brown Boveri Asklepitron 45 electron beams, to obtain the parameters for the Sagittaire linear accelerator electron beams introducing the necessary modifications in the dose equation. The dose equation used by Steben et al. is given.

Experimental test accelerator (ETA)

Abstract: The Lawrence Livermore Laboratory is constructing an induction linac with the following parameters 10kA, 50ns FWHM pulse width, 5MeV, and 5PPS. This paper describes the design features of the 2.5 MeV injector and it's associated pulsed power system.