Showing papers on "Linear particle accelerator published in 1975"

Photoproduction of the psi Particles

Abstract: The s and t dependence of incoherent psi (3100) photoproduction from deuterium has been measured at the Stanford Linear Accelerator Center. psi (3700) photoproduction and psi (3100) photoproduction from hydrogen have also been measured.

Synchrotron radiation as a new tool within photon‐beam technology

Abstract: Synchrotron radiation is now playing an increasingly important role in recent developments of new light sources. Synchrotron light emitted from a relativistic electron beam has a radiation pattern which makes it a unique source. The advantages with this type of radiation can be summarized as (a) continuous spectrum extending from the ir to the x‐ray region, (b) strongly polarized, (c) highly collimated, (d) pulsed structure allowing time‐resolution spectroscopy, and (e) high intensity making feasible the use of monochromators with narrow band pass. The Stanford Synchrotron Radiation Project has been in operation since May 1974 as a U.S. National Facility for uv and x‐ray research in many disciplines using the radiation from the storage ring SPEAR at the Stanford Linear Accelerator Center. The radiation spectrum is characterized by the critical energy which varies as E3 (E=electron‐beam energy) and is 11 keV for E=4 GeV. Useful flux is available out for approximately five times the critical energy. Five mo...

Standing-wave linear accelerator

Abstract: A standing-wave linear charged particle accelerator is disclosed which comprises a plurality of interlaced substructures, with each substructure having a plurality of accelerating cavities disposed along the particle beam path and having side cavities disposed away from the beam path for electromagnetically coupling the accelerating cavities. A standing radio-frequency electromagnetic wave is supported in each substructure, with the wave in each substructure being phase with respect to the wave in every other substructure so that the particle beam will experience a maximum energy gain throughout its path through the accelerator. This interlaced substructure configuration minimizes the transit time of the particles across the gap of each accelerating cavity and makes it possible to operate the accelerator without radio-frequency breakdown at a power level that provides a substantially higher average value of the accelerating electric field along the beam path than has heretofore been obtainable.

Double pass linear accelerator operating in a standing wave mode

Abstract: A double pass linear accelerator which is used in a radiation therapy unit to provide electron radiation or photon bremsstrahlung radiation when combined with an appropriate target. The accelerator operates in a standing wave mode and includes an accelerating section, a charged particle source and injection section, a microwave source operating in the S band and adapted to excite the accelerating section and a reflector system which is mounted at one end of the accelerating section to reflect a particle beam which has been accelerated due to one pass, back into the accelerating section such that it may be further accelerated. The distance between the reflector is made adjustable to provide for output particle energy variation.

Code of practice for x-ray therapy linear accelerators

Abstract: Details are presented on the tests that should be performed during the installation of a megavoltage linear accelerator. Also discussed are the dosimetry studies that should be done as part of the operation of the machine. Information in specific radiation monitoring equipment is provided. (AIP)

Design Considerations for the ORNL 25 MV Tandem Accelerator

Abstract: Construction of a 25 MV tandem electrostatic accelerator is now planned as part of a new heavy-ion facility at the Oak Ridge National Laboratory. The design of this accelerator incorporates several unusual features. The most important of these are a folded design, in which the low-energy and high-energy acceleration tubes are contained within a single column structure, and a digital control system. Motivations for these design features are discussed in conjunction with a brief description of the accelerator.

X-RAY DEPTH DOSES FROM LINEAR ACCELERATORS IN THE ENERGY RANGE FROM 10 TO 32 MeV

Abstract: The depth dose characteristics of the x-ray beam from a linear accelerator have been studied in the electron energy range from 10 to 32 MeV for various target and flattening filter combinations. At all energies the most penetrating x-ray beam is obtained with a low atomic number flattening filter. At energies below 15 MeV a high atomic number target should be used, while at energies above 15 MeV a low atomic number target should be employed to get the best depth dose distribution. The optimum target thickness is approximately equal to the mean range of electrons in the target material. The study of some physical parameters such as depth dose, average dose, and integral dose, suggests that the optimum energy for linear accelerators used in the x-ray mode is about 25 MeV.

Surface Dose from Megavoltage Therapy Machines

Abstract: To determine the cause of increased skin reactions near the edges of the field the authors measured doses at and near the surface of the skin with an extrapolation chamber for the gamma-ray beam of an AECL Eldorado 8 60Co irradiator and the x-ray beams of a Varian Clinac 4 linear accelerator, a Varian Clinac 6 linear accelerator, and an ARCO Mevatron 8 linear accelerator. Buildup curves were measured on each machine to locate the depth of the maximum dose (Dmax). The surface dose of the central axis was measured as a function of field size. Off-axis surface doses were measured on the Clinac 4 linear accelerator and on the Eldorado 8 60Co therapy unit. No measurable increase in surface dose was found leading the authors to believe that the observed skin reaction in the axilla for the Clinac 4 linear accelerator is due to a combination of increased dose at Dmax from the anterior mantle field and an increase in exit dose from the posterior mantle field when compared to similar treatments for 60Co.

Double Pass Linear Accelerator - Reflexotron

Abstract: Measurements of energy spectra and percentage beam transmissions are given for an S-band linear accelerator through which the electron beam passes twice, in opposite directions. Results are presented for two magnet reflecting systems which have energy acceptance windows, ?E/E, of 2% and 16% where E is the output beam energy after the first pass through the accelerator. For a first pass beam energy of 8 MeV the second pass energy could be varied from 3 MeV to 16 MeV by changing the separation between the accelerator and the magnet system. The corresponding full-width half-maximum energy spreads were 1.6 MeV and 0.7 MeV respectively. The system transmission was 35% first pass (unbunched injected beam) and ~ 100% second pass.

Experimental Investigation of Linear-Beam Collective Ion Acceleration in Vacuum

Abstract: Preliminary experimental results of collective ion acceleration using a linear beam from the University of Maryland Electron Ring Accelerator injector are presented. Neutron yield of 109 neutrons/pulse from Cu(p, n) Zn reactions are observed. From the Q value of the reaction, the energy of the proton must be above 4 MeV. The number of protons per pulse is estimated to exceed 1013.

Ultra-Short Pulies of Heavy Ions

Abstract: The bunching requirements for a heavy-ion tandemlinac accelerator are defined and a bunching system to satisfy these requirenents is outlined. This discussion introduces an experimrent on the bunching of 45 MeV 16O ions by means of a ?/2 superconducting-helix resonator. The measured ion-bunch width is 64 psec, a value daminated by the resolution width of the ion detector. By correcting for the detector-resolution width one infers that the ion bunch itself is <40 psec wide.

Linear particle accelerator using magnetic mirrors

Abstract: A particle accelerator for obtaining high energy particle beams, comprises an accelerating structure SA, one mirror or two mirrors constituted with magnetic achromatic and stigmatic deviators and a source K of particles located at the entry of the accelerating structure SA and having an annular shape allowing the accelerated particles having passed twice through the accelerating structure SA to cross the source K, the axis of the source K being coincidental with the axis of the accelerating stucture SA. Magnetic fields are determined in such a manner that the mirrors totally reflect the particles having a predetermined energy level and totally transmit the particles having an energy level higher than this predetermined energy level.

A 200-MHz Debuncher for the Fermilab Injector

Abstract: Although the momentum spread of the beam as it leaves the linac is comfortably within the design specifications, space charge effects in the 200-MeV transport line and in the booster increase the momentum spread of the debunched beam.112,314 The phase space density of the beam is further decreased during capture in the booster because the magnetic field is changing during capture and because the capture process is not completely adiabatic. 5,6

A Wide Dynamic Range 10 MeV High Current Electron Linear Accelerator

Abstract: The salient features of a new high power linear accelerator system are described. This machine combines a 300 kV dc accelerator, constructed for operation with pulsed currents in excess of 2A, with a single section 10 MeV accelerator waveguide so that given levels of high peak current may be maintained over a wide range of beam energies. (Previous technology required RF phase and/or power adjustment to a second accelerator section.) The accelerator waveguide incorporates a suppressed phase oscillation buncher designed so that a loss of terminal electric field strength, caused by a large reduction of input RF power to reduce beam energy, may be accurately compensated by an increase in potential of the dc accelerator, thus maintaining the capture efficiency of the waveguide. Reduction of space charge forces due to HV injection, and avoidance of dual section operation, prove to be major operational advantages. The 20 MW RF transmitter and the overall beam centerline are described; and operating performance and equipment photographs are presented.

Accessory beam flattening filter for the varian clinac-4 linear accelerator.

Abstract: An accessory beam flattening filter (brass disk with critical angles) attaches to the shadow tray of the Clinac-4 linear accelerator, intercepts the x-ray beam, and eliminates higher dose areas at the edges of large fields near the skin surface. This improves the x-ray beam dose distribution within the patient and results in a reduction of dose to normal tissues near the surface.

Tests on the initial section of an accelerator with quadrupole HF focusing

Abstract: The focusing, acceleration, and bunching are described for the beam injection section of a linear ion accelerator. This initial section is a double H cavity with accelerating electrodes and resonant chambers made of steel coated with copper. Under normal operation, the focusing channel carries the entire beam current from the 100-keV ion gun (up to 400 mA). (PMA)

Depth absorbed dose distributions for electrons

Abstract: It is pointed out that comparisons made by Brahme et al. (see ibid., vol.20, p.39, 1975) were made with the microtron in an operating condition different from that of the MEL SL75 linear accelerator. In order to obtain results that can be more readily compared, measurements have been made on a SL75 linear accelerator using a 0.1 mm3 active volume solid state detector in a water phantom with a thin entrance window.

The PEP Injection System

Abstract: A system to transport 10-to-15-GeV electron and positron beams from the Stanford Linear Accelerator and to inject them into the PEP storage ring under a wide variety of lattice configurations has been designed. Optically, the transport line consists of three 360° phase-shift sections of FODO lattice, with bending magnets interspersed in such a way as to provide achromaticity, convenience in energy and emittance definition, and independent tuning of the various optical parameters for matching into the ring. The last 360° of phase shift has 88 milliradians of bend in a vertical plane and deposits the beam at the injection septum via a Lambertson magnet. Injection is accomplished by launching the beam with several centimeters of radial betatron amplitude in a fast bump provided by a triad of pulsed kicker magnets. Radiation damping reduces the collective amplitude quickly enough to allow injection at a high repetition rate.

Single Bunch Beam Loading Experiments on the SLAC Two-Mile Accelerator

Abstract: In September 1971, the authors presented a paper on “Single Bunch Radiation Loss Studies at SLAC. ” I Aside from its academic interest, the main motivation behind this work was its relevance to the design of electron ring accelerators (ERA). Indeed, at that time a number of laboratories throughout the world were hoping to build these new types of machines but the theories of how much energy the ring would radiate to its accelerating structure were not on firm ground and had not been tested. The SLAC two-mile accelerator seemed to be one of the few vehicles where the dependence of single bunch radiation loss as a function of energy could be measured.

Measurements of selected psi (3684) branching ratios from a study of secondary lepton pairs

Abstract: The measurements considered were made at the electron-positron storage ring at the Stanford Linear Accelerator Center. The apparatus used consists of two identical spectrometers mounted in a collinear configuration about the beam-interaction region. The energies of secondary electrons or positrons are measured with good resolution in large NaI(Tl) total-absorption detectors. Data accumulated without gamma-ray converters were examined for electron-positron pairs. The data taken with gamma-ray converters in place and at center-of-mass energies within 1 MeV of the resonance energy were scanned for evidence of either charged particles or converted gamma rays accompanying the detected muon pairs.

Light Ion Linacs for Medical Applications

Abstract: Recent advances in linear accelerator technology point to the feasibility of designing and developing practical medical linacs for producing protons, neutrons, or pi mesons for the radiation therapy of cancer. Additional uses of such linacs could include radioisotope production and charged particle radiography. For widespread utilization medical linacs must exhibit reasonable cost, compactness, reliability, and simplicity of operation. Possible extensions of current accelerator technology which might provide these characteristics are discussed in connection with linac design, fabrication techniques, materials, power sources, injectors, and particle collection and delivery systems. Parameters for a medical proton linac for producing pions are listed.

Implications of High Beam Currents for Accelerator and Component Design

Abstract: Introduction The need for higher currents has been a primary force in design and innovation since the invention of accelerators, and a substantial amount of attention continues to be directed toward this end. In this paper, some aspects of the influence this effort has had upon the design of accelerators and storage rings are reviewed. In order to permit proper coverage and to achieve clarity, it has been necessary to limit the choice of topics for discussion and therefore to omit some of the many schemes used to achieve the present degree of success. These topics have been arbitrarily selected from the following categories: transverse interaction of a beam with its surroundings, longitudinal interaction of a beam with its surroundings, influence of vacuum on high beam currents and colliding beam-beam interactions. In the preceding paper presented at this Conference,' the limitation of beam performance by these phenomena has been reviewed and the reader is referred to this paper for more complete references to the original literature. Transverse Interaction of a Beam with Its Environment It was first observed by Kerst that the self fields of a high-current beam would reduce the transverse fo-cusina of the beam and result in a shift of the betatron osciljation frequent y, Av, which is proportional to the number of particles. The beam will become unstable if the betatron frequency is shifted onto a strong resonance , an effect which has certainly influenced the design of proton synchrotrons and their injectors, especially strong focusing machines. Because the maximum number of particles as limited by this tune shift increases with energy, one solution has been to increase the output energy of the injector, For example, in the Brookhaven conversion project, the linac energy output was increased to 200 MeV. At CERN, the P.S. Booster Group takes a different approach. They retain the 50 MeV linac but feed four rings, each with the sufficient number of particles to be at the Av limit, and accelerate the four beams up to 800 MeV, an energy at which they are below the Av limit when the beams are combined in the CERN proton synchrotron. At the Princeton-Penn accelerator and the Fermilab Booster, still another approach was used: to increase the pulse rate to achieve the total number of particles per second desired within the Av limit for the number of oarticles that could be contained in the synchrotron.' Laslett …