Showing papers on "Linear particle accelerator published in 1978"

High‐current‐pulsed linear ion accelerators

Abstract: Possible methods are described for constructing ion linear accelerators in the 100‐MeV range which have pulsed current outputs 105 times higher than currently available. A drift‐tube design with insulating magnetic fields between the tubes is presented. The fields not only prevent electron flow, but also are essential for beam neutralization by low‐energy electrons and transverse beam focusing. Preliminary discussions are given on accelerator design and construction, transverse focusing and beam neutralization, and control of the beam in longitudinal phase space.

Alternating phase focused linacs

Abstract: A heavy particle linear accelerator employing rf fields for transverse andongitudinal focusing as well as acceleration. Drift tube length and gap positions in a standing wave drift tube loaded structure are arranged so that particles are subject to acceleration and succession of focusing and defocusing forces which contain the beam without additional magnetic or electric focusing fields.

Wall-scattering effects in electron beam collimation.

Abstract: This report describes now a set of applicators, convering fields with dimensions of 4 to 20 cm, for the 6 to 20 MeV electron beams of a MEL SL75-20 linear accelerator was developed. The electron scatter contribution of the applicator walls to the treatment field was investigated, varying the applicator entrance opening and the scattering foil, with the aim of optimizing the resulting field flatness, with a minimum loss of depth dose. Experiments with field defining end frames and additional perspex scatterers for large field sizes are also reported.

Combination free electron and gaseous laser

Abstract: A multiple laser having one or more gaseous laser stages and one or more free electron stages. Each of the free electron laser stages is sequentially pumped by a microwave linear accelerator. Subsequently, the electron beam is directed through a gaseous laser, in the preferred embodiment, and in an alternative embodiment, through a microwave accelerator to lower the energy level of the electron beam to pump one or more gaseous lasers. The combination laser provides high pulse repetition frequencies, on the order of 1 kHz or greater, high power capability, high efficiency, and tunability in the synchronous production of multiple beams of coherent optical radiation.

Compact irradiation apparatus using a linear charged- particle accelerator

Abstract: An irradiation apparatus comprising a fluid-tight enclosure in which are located a linear electron accelerator, a magnetron supplying a high frequency signal, means for injecting this high frequency signal into the accelerating structure, means for supplying voltage to the magnetron and the accelerator. A magnetic deflecting system can be associated with the linear accelerator for deflecting the accelerated electrons towards a target emitting X-rays. Cooling systems are provided inside the enclosure 1, in particular for cooling the magnetron.

Neutrontherapy apparatus using a linear accelerator of electrons

Abstract: Neutron-based radiotherapy apparatus comprising a linear charged-particle accelerator which delivers a beam of accelerated electrons, a target intended to be bombarded by the beam of accelerated electrons for emitting neutrons under the impact of that beam, means for cooling the target, means for eliminating parasitic radiations, and a collimation system for the useful beam of neutrons. The electron accelerator may be arranged either on the inside or on the outside of the rotating arm of the neutron-radiotherapy apparatus.

Pulsed ferrite core tests for 50-ns linear induction accelerator

Abstract: The Lawrence Livermore Laboratory undertook an investigation of the properties of ferrite materials to be used in a 5-MeV, 50-ns linear induction accelerator. The investigation, on a part-time basis, lasted about one year and had the cooperation and helpful suggestions of several manufacturers: TDK of Japan, Phillips of Holland, and Stackpole of the U.S.A. Ferrites have been widely used as tuning cavities for proton synchrotron accelerators at radio frequencies. In such an application, the μQf factor is used in describing the figure of merit for ferrites where a high duty factor requires low loss ferrites. In our linear induction accelerator with an average rep-rate of 5-Hz, the ferrite losses are negligible and the concept of complex permeability in describing the losses will not be introduced, but a large signal ΔB/ΔlH will be used to describe their properties. The properties of interest in designing the accelerating cavity were: a) flux swing ΔB = B r + B m > .5T b) a residual flux density B_{r} \geq .15T with a reset no greater than 2 Oer. c) a relatively high incremental μ > 400 to keep the excitation current small in relation to the load current, d) a high resistivity for the 250-kV voltage hold-off.

Accelerating structure for a linear charged particle accelerator

Abstract: OF THE DISCLOSURE : An accelerating structure for a linear particle accelerator operating in the travelling wave mode or in the standing wave mode comprises at least one accelerating section and a complementary bunching or pre-accelerating section formed by a resonant cavity of the reentrant type magnetically coupled with the first cavity of the accelerating section by means of a coupling iris, the reentrant cavity having a length L = (2m + 1) .lambda.o/4 and the distance D separating the interaction spaces of the first cavity of the complementary section and the first cavity of the accelerating section being equal to D = (2k + ? +.alpha.) .pi..beta..lambda.o , with O?.alpha. ?, n and k being integers, .beta. being the reduced velocity v/c of the particles and .lambda.o being the operating wave length of the accelerator.

Integrator for use in bombardment experiments.

Abstract: A convenient integrator was developed for use in bombardment experiments with a charged particle accelerator such as a linac. In this device an irradiation dose is digitally displayed in the number of electrons per cm2. Furthermore, a linac is controlled to deliver a preset dose by this integrator.

Conceptual design of a heavy ion fusion energy center

Abstract: A Heavy Ion Accelerator system is described which is based upon existing technology, and which is capable of producing 150 MW of average beam power in 10 MJ, 200 TW bursts, 15 times per second It consists of an rf linac which accelerates doubly ionized uranium ions to an energy of 20 GeV Then by utilizing the well known procedure of multiturn injection, a 66 ms long burst of linac current is stored in 8 separate ''accumulator'' rings At the conclusion of the filling process, a pulsed rf system bunches the beam in each of the 8 rings simultaneously As the bunches decrease in length, they are then extracted from the rings and transported for about 1 km to one of 5 ''boilers'', in which the thermonuclear pellet has been placed The 8 beams (2 opposing clusters of 4 beams each) are then focused simultaneously onto the pellet, resulting in a release of thermonuclear energy about 80 times larger than the input beam energy

Evaluation of the Therac 6 linear accelerator for radiation therapy.

Abstract: The Therac 6 is new generation of low-energy linear accelerator. It incorporates a PDP-11/05 computer for beam control, treatment-factor input, and beam shutdown in the event of failure of the system. The performance of the unit has not been hindered by computer or software malfunction, and the computer has provided an excellent means for preventive maintenance and repair. Dosimetry parameters are similar to other 6 MV x-ray beams, and comparison to 60Co therapy beams shows that this unit may be more like 60Co units in penumbra and absence of off-axis peaking than other low-energy accelerators.

Some new accelerating structures for high current intensity accelerators

Abstract: The space charge effect inside the beam of charged particles causes serious problems in high-intensity linear particle accelerators At the present time there is only the Alvarez-Blewett accelerating structure which uses continuous strong focusing to keep the beam confined to the axis The most serious problem is at the injection end of the accelerator where the particle velocities are low and the drift tube structure has decreased efficiency It is suggested that some new or less well known accelerating structures using rf quadrupole focusing and H-type mode resonators may solve this problem The disk-and-washer structure with very high coupling coefficient can be used successfully for the high-energy part of the accelerator A newly developed coaxial coupler solves the problem of the intertank rf coupling

A Pulsed System for Obtaining Microdosimetric Data with High Intensity Beams

Abstract: The use of heavy particle accelerators for radiation therapy requires high intensity beams in order to produce useful dose rates. The 800-MeV proton beam at LAMPF passes through different production targets to generate secondary pion beams. Conventional microdosimetric techniques are not applicable under these conditions because exceedingly high count rates result in detector damage, gas breakdown, and saturation effects in the electronics. We describe a new microdosimetric system developed at the Pion Biomedical Channel of LAMPF. The accelerator provides a variable low intensity pulse once every ten high intensity macropulses. The voltage on the detector is pulsed in coincidence with the low intensity pulse so that we were able to operate the detector under optimum data-taking conditions. A low noise two-stage preamplifier was built in connection with the pulsed mode operation. A comparison is made between data obtained in pulsed (high intensity beam) and unpulsed (low intensity beam) modes. The spectra obtained by the two methods agree within the experimental uncertainties.

Phase-space constraints on some heavy-ion inertial-fusion igniters and example designs of 1 MJ rf linac systems

Abstract: The design of a high-energy heavy-ion accelerator system for the ignition of inertial-fusion pellet targets starts with the need to satisfy the six-dimensional phase space volume requirement at the target, taking into account dilutions of ion phase space density arising from imperfect beam manipulations throughout the system. Although this need is well known, the phase space condition does not appear to have been widely used as a systematic design guide. Such an approach is presented for systems employing an rf linac either as the main accelerator or as a synchrotron injector; some general properties of final focusing lens systems are included in the analysis. The method is illustrated in some detail, and example designs are developed, for one-megajoule linac-accumulator ring systems.

Establishment of a beam line at the Fermi National Accelerator Laboratory for proton radiography

Abstract: A proton beam is extracted from the 200-MeV linear accelerator at the Fermi National Accelerator Laboratory to investigate the efficacy of proton radiography in medical diagnosis. Fluence rates from 2 x 10/sup 3/ to 2 x 10/sup 5/ protons/cm/sup 2/ s over a 28-cm diameter field are obtained with a full width at half-maximum beam-energy spread of less than 3.61 MeV. The system is designed to radiograph most parts of the human body, including the head, with high-speed screen-film as the imaging medium. Beam extraction and test results along with the medical implications of the beam quality are reported.

25 MV X-ray beam characteristics from a 35 MeV linear accelerator.

Abstract: This manuscript presents characteristic dosimetry measurements for the 25 MV X-ray beam from the Varian Associates Clinac ® 35 linear accelerator. The quality of the beam is expressed by its attenuation as a narrow beam in lead. Percentage depth dose tables are given as a function of field size for square fields. Tissue-phantom ratios are tabulated for square field sizes. A study of the variation of the dose in the buildup region demonstrates that surface dose and the depth of maximum dose is a strong function of the field size. Other beam parameters measured and discussed include field flatness and symmetry, penumbra, and applicability of inverse square law.

Absorbed dose distributions for X-ray beams and beams of electrons from the Therac 20 Saturne linear accelerator.

Abstract: After a brief description of the Therac 20 Saturne linear accelerator a complete set of absorbed-dose distribution values is given. These values define the depths on the axis as a function of the depth dose and define the penumbra (as characterized by the positions of the intersections of the isodose curves with planes parallel to the phantom surface) for beams of X-rays and for beams of electrons. Tissue-maximum ratios are given for beams of X-rays. Analytical values for the electron depth dose curve are compared with the values obtained on the Sagittaire linear accelerator.

Developments in the Physics of High Current Linear Ion Accelerators

Abstract: Linear ion accelerators have been proposed for both high peak and high average current applications.1 The design of high-intensity linacs is strongly influenced by the requirement of providing sufficient focusing (confinement) for the beam to balance the effects of the space-charge (self-field) forces, which become important for high beam current. Longitudinal focusing is obtained by operation on the rising rf electric field, where both acceleration and phase stability are obtained. Strong transverse focusing results from electric or magnetic quadrupole lenses arranged in a quasiperiodic structure; in the drift-tube linac (DTL), these individual quadrupole elements are installed within the drift tubes. In a smooth approximation, the quadrupole lenses produce an equivalent linear continuous focusing force upon which is superimposed the local forces of individual lenses that create a flutter in the beam envelope.

Velocity of the propagation of the ionized front of the plasma cluster in the linear rail type accelerator

Abstract: Two microwave apparatus for the measurement of the plasma cluster velocity are described in this paper. The obtained results show that the position of the maximum velocity is shifting in dependence on the capacitor battery voltage. Further on the dependencevmax=k.U02 was found experimentally.