Showing papers on "Linear particle accelerator published in 1981"
TL;DR: In this paper, a gallium arsenide photocathode is illuminated by the optical beam from a frequency doubled, actively mode-locked and Q-switched Nd:YAG laser.
Abstract: For the generation of intense single and multiple bunches of electrons (>8 nc per bunch) for accelerator studies at SLAC, a high peak current photoemission electron gun has been developed. A gallium arsenide photocathode is illuminated by the optical beam from a frequency doubled, actively mode-locked and Q-switched Nd:YAG laser. The mode-locked optical pulses are of variable, sub-nanosecond width and occur with a spacing of 8.4 nsec, synchronized with the 2856 MHz accelerator rf. The gun is designed to be space charge limited at 15 A and 200 kV, although emission of 60 A was obtained with a 57 kV test structure, corresponding to a current density of 180 A/cm2. With the proper choice of laser wavelength, the electron beam may be 40% longitudinally polarized.
52 citations
TL;DR: The design of a dedicated intra-operative facility, using a high energy linear accelerator, is presented with respect to shielding requirements for the machine and the room and to improved beam design by increasing the incident electron dose rate and by improving the depth dose at each energy.
Abstract: In the early part of 1978, a pilot program of intra-operative radiotherapy was initiated at the Massachusetts General Hospital (MGH), using beams of high energy electrons. A technique has been employed to irradiate the tumor bearing area using a sterilized acrylic resin cone that slides into a metal holder attached to the head of the accelerator. The acrylic resin cone is inserted into the patient directly over the tumor; the patient couch is adjusted until the cone is correctly aligned inside the holder. The dosimetry for this procedure has been investigated as a function of the primary collimator setting of the linear accelerator. A fixed setting was chosen as a compromise between increased bremsstrahlung, low effective electron dose rate observed with narrower settings, and more rounded beam profiles together with somewhat poorer depth dose characteristics found with larger settings. Field shaping and blocking of critical organs was achieved using sterile lead sheets that are cut to the appropriate size. Consideration has been given to improved beam design by increasing the incident electron dose rate and by improving the depth dose at each energy. The design of a dedicated intra-operative facility, using a high energy linear accelerator, is presented with respect to shielding requirements for the machine and the room.
49 citations
TL;DR: The 18 MV photon beam characteristics of a Therac 20 Medical Linear Accelerator manufactured by Atomic Energy of Canada Ltd, are presented and the effect of field size and depth on the penumbra is described.
Abstract: The 18 MV photon beam characteristics of a Therac 20 Medical Linear Accelerator manufactured by Atomic Energy of Canada Ltd, are presented. Tissue phantom ratios (TPR's) and percent depth dose data are given; for a 10 x 10 cm field, the percent depth dose at a depth of 10 cm is 78.5 (SSD 100 cm). The relative dose factors (RDF'S) are given and are analyzed to elucidate the relative contributions from phantom scatter, collimator scatter, and backscatter from the top of the collimators into the monitor chambers. The effect of field size and depth on the penumbra is described. Crossplots of the beam at a depth of 5 cm indicate that the flattening filter could be improved; there are hot spots of 108% near the corners of 40 x 40 fields.
42 citations
TL;DR: A radiofrequency quadrupole (RFQ) focused proton linac has been developed and successfully tested at the Los Alamos Scientific Laboratory (LASL) for the purpose of evaluating its performance and applicability as a low-beta accelerator as discussed by the authors.
Abstract: A radio-frequency quadrupole (RFQ) focused proton linac has been developed and successfully tested at the Los Alamos Scientific Laboratory (LASL) for the purpose of evaluating its performance and applicability as a low-beta accelerator. The geometry of the structure was designed to accept a 100-keV beam, focus, bunch, and accelerate it to 640 keV in 1.1 m with a high-capture efficiency and minimum emittance growth. The accelerator test facility includes an injector, low-energy transport section for transverse matching, and a high-energy transport section for analysis of the beam properties. The accelerator cavity is exited through a manifold powered by a 425-MHz klystron. Diagnostic instrumentation was prepared to facilitate operation of the accelerator and to analyze its performance. Measurements of the beam properties are presented and compared with the expected properties resulting from numerical calculations of the beam dynamics.
34 citations
TL;DR: In this article, the beam dynamics and current limits in a linear accelerator are determined largely by the periodicity and phase-space acceptance of the external focusing system and the particle oscillation frequencies (or phase shifts per focusing period), both without the space-charge forces and with the space charge forces of the particle bunch.
Abstract: In recent years considerable interest has developed in the use of linear accelerators for various high‐current applications (radiation testing facilities, neutron spallation sources, heavy‐ion fusion, etc.). The beam dynamics and current limits in a linear accelerator are determined largely by the periodicity and phase‐space acceptance of the external focusing system and the particle oscillation frequencies (or phase shifts per focusing period), both without the space‐charge forces and with the space‐charge forces of the particle bunch. General formulas for the transverse and longitudinal current limits in terms of these fundamental quantities are derived. The relationships with the actual accelerator and particle beam parameters are examined for strong (quadrupole) and weak focusing field configurations. As a practical illustration, the results are applied to a drift‐tube linac with quadrupole focusing in the transverse direction and rf phase focusing in the longitudinal direction.
31 citations
TL;DR: Buildup and surface-dose measurements were taken for the 6 MV photon beam from a Therac 6 linear accelerator with and without a lucite blocking tray in place and the results were found to be consistent with similar measurements taken with a variable volume extrapolation chamber.
Abstract: Buildup and surface-dose measurements were taken for the 6 MV photon beam from a Therac 6 linear accelerator manufactured by Atomic Energy of Canada Limited (AECL) with and without a lucite blocking tray in place. Further measurements were made with a copper filter designed to reduce secondary electrons emitted by photon interactions with the Lucite tray. The results are discussed in relation to skin-sparing for radiation therapy patients. The measurements were made with a fixed volume PTW parallel-plate ionization chamber and corrected to zero-chamber volume. The results were found to be consistent with similar measurements taken with a variable volume extrapolation chamber.
25 citations
TL;DR: The radio-frequency quadrupole (RFQ) linear accelerator as mentioned in this paper was developed at Los Alamos, USA to accelerate high-current dc beams with only small beam loss and low radial emittance growth.
Abstract: In many Laboratories, great emphasis now is placed on the development of linear accelerators with very large ion currents. To achieve this goal, a primary concern must be the low-velocity part of the accelerator, where the current limit is determined and where most of the emittance growth occurs. The use of magnetic focusing, the conflicting requirements in the choice of linac frequency, and the limitations of high-voltage dc injectors, have tended to produce lowvelocity designs that limit overall performance. The radio-frequency quadrupole (RFQ) linear accelerator, invented in the Soviet Union and developed at Los Alamos, offers an attractive solution to many of these low-velocity problems. In the RFQ, the use of RF electric fields for radial focusing, combined with special programming of the bunching, allows high-current dc beams to be captured and accelerated with only small beam loss and low radial emittance growth. Advantages of the RFQ linac include a low injection energy (20-50 keV for protons) and a final energy high enough so the beam can be further accelerated with high efficiency in a Wideroe or Alvarez linac. These properties have been confirmed at Los Alamos in a highly successful experimental test performed during the past year. The success of this test and the advances in RFQ design procedures have led to the adoption of this linac for a wide range of applications. The beam-dynamics parameters of three RFQ systems are described.
23 citations
TL;DR: In this paper, a high-current injector was designed to yield the 7.5 × 1010e-per S-band bunching required for the proposed linear collider.
Abstract: A new, high-current injector has been designed to yield the 7.5 × 1010e- per S-band bunch necessary for the proposed linear collider. The injector consists of two prebunchers at the 16th subharmonic, a 0.75 c traveling wave buncher, and a three-meter velocity of light traveling wave structure. The e- beam is confined by a solonoidal magnetic field in the buncher and capture regions. A computer simulation similar to that used by Mavrogenes et al., has been used to calculate the bunching. The calculation indicates it is possible to achieve ~l × 1011e- in 16° of S-band from a 15 amp gun pulse of 1.5 nsec duration.
17 citations
TL;DR: In this paper, the transverse emittance properties of a high-current linear accelerator were measured by using TV cameras sensitive to the visible radiation emitted following beam interactions with residual gas, which was used to measure emittances for the Fusion Materials Irradiation Test (FMIT).
Abstract: The transverse emittance properties of a high-current linear accelerator may be measured by using TV cameras sensitive to the visible radiation emitted following beam interactions with residual gas. This paper describes the TV system being used to measure emittances for the Fusion Materials Irradiation Test (FMIT) project.
16 citations
Patent•
29 May 1981TL;DR: In this article, a system for achromatically deflecting a beam of charged particles without producing net divergence of the beam comprises three successive magnetic deflection means (A, B, C) which deflect the beam alternately in opposite directions.
Abstract: A system for achromatically deflecting a beam of charged particles without producing net divergence of the beam comprises three successive magnetic deflection means (A, B, C) which deflect the beam alternately in opposite directions. the first (A) and second (B) by angles of less than 50° and the third (C) by an angle of at least 90°; particles with different respective energies are transversely spaced as they enter the third deflection means (C), but emerge completely superimposed in both position and direction, and may be brought to a focus (F) in each of two mutually perpendicular planes a short distance thereafter. Such a system may be particularly compact, especially in the direction in which the beam leaves the system. and is suitable for deflecting a beam of electrons from a linear accelerator (5,6,7) so as to produce a vertical beam of electrons (or with an X-ray target, of X-rays) which can be rotated about a horizontal patient for radiation therapy.
16 citations
TL;DR: The radio-frequency quadrupole (RFQ) as mentioned in this paper is a new linear accelerator concept in which rf electric fields are used to focus, bunch, and accelerate the beam, and it can capture a high-current dc ion beam from a lowvoltage source and accelerate it to an energy of 1 MeV/nucleon within a distance of a few meters.
Abstract: The radio-frequency quadrupole (RFQ) is a new linear accelerator concept in which rf electric fields are used to focus, bunch, and accelerate the beam. Because the RFQ can provide strong focusing at low velocities, it can capture a high-current dc ion beam from a low-voltage source and accelerate it to an energy of 1 MeV/nucleon within a distance of a few meters. A recent experimental test at the Los Alamos Scientific Laboratory (LASL) has confirmed the expected performance of this structure and has stimulated interest in a wide variety of applications. We review the general properties of the RFQ, and present examples of applications of this new accelerator.
CERN1
TL;DR: The Program Lines Sequencer (PLS) as discussed by the authors sends to the equipment concerned (before every machine cycle) a serial message, describing the user and the characteristics of the beam, created by an on-line computer using previously-entered information through a series of application programs and external conditions coming from the process or the users.
Abstract: The CERN PS complex (comprising the 50 MeV Linac, the 800 MeV Booster, the 28 GeV PS and the 3.5 GeV/c Antiproton Accumulator) must deliver beams of various characteristics (e.g. energy, intensity, emittances, ejection mode) to several users, with a repetition time as low as 0.65 s. The SPS accelerator, ISR and LEAR storage rings and the 25 GeV physics experiments receive beams in a repetitive sequence, called a supercycle. The coordination is achieved by the Program Lines Sequencer (PLS) which sends to the equipment concerned (before every machine cycle) a serial message, describing the user and the characteristics of the beam. This message is created by an on-line computer using (i) previously-entered information through a series of application programs and (ii) external conditions coming from the process or the users: these signals in turn can modify the information (i) accordingly.
TL;DR: In this paper, a computer code was developed to reconstruct the 4D transverse phase-space distribution of an accelerator beam from a set of linear profiles measured at different angles at three or more stations along the beam line.
Abstract: A computer code has been developed to reconstruct the 4-D transverse phase-space distribution of an accelerator beam from a set of linear profiles measured at different angles at three or more stations along the beam line. The code was applied to wirescan data obtained on the low-intensity H- beam of the LAMPF accelerator. A 4-D reconstruction was obtained from 10 wire-scan profiles; 2-D projections of the reconstruction agree fairly well with slit-and-collector measurements of the horizontal and vertical emittance distributions.
TL;DR: In this article, the following possibilities are discussed: inverse free electron laser (wiggler accelerator), inverse Cerenkov effect, plasma accelerator; dielectric tube; and grating linac.
Abstract: The following possibilities are discussed: inverse free electron laser (wiggler accelerator); inverse Cerenkov effect; plasma accelerator; dielectric tube; and grating linac. Of these, the grating acceleraton is considered the most attractive alternative. (GHT)
01 Dec 1981
TL;DR: This publication provides an overview of the components of the linear accelerator and how they function and interrelate.
Abstract: This primer is part of an educational package that also includes a series of three videotapes entitled 'Theory and Operation of Linear Accelerators in Radiation Therapy, Parts I, II, and III' This publication provides an overview of the components of the linear accelerator and how they function and interrelate The auxiliary systems necessary to maintain the operation of the linear accelerator are also described
TL;DR: In this article, a linear induction accelerator with beam transport using electron neutralization of ion space charge is described. But it is based on linear induction technology coupled with new methods of beam transport, and the resulting accelerators are modular and relatively compact.
Abstract: Accelerator systems capable of driving inertial fusion targets are described. They are based on linear induction accelerator technology coupled with new methods of beam transport using electron neutralization of ion space charge. The resulting accelerators are modular and relatively compact. Typical unbunched output parameters of a beamline are 37 kA of Ne+ at 150 MeV in a 60 ns pulse.
TL;DR: In this paper, the authors analyze several important beam stability topics, including radial oscillations induced by an accelerating gap, the diocotron, resistive wall, and cyclotron maser instabilities, and the transverse beam breakup and image displacement instabilities.
Abstract: Stable beam transport may be the limiting factor in the development of a new generation of high current linear induction accelerators. In this paper we analyze several important beam stability topics, including radial oscillations induced by an accelerating gap, the diocotron, resistive wall, and cyclotron maser instabilities, and the transverse beam breakup and image displacement instabilities. At present image displacement appears to represent the most serious limitation to high current beam transport in linear accelerator structures.
TL;DR: The Heidelberg Heavy Ion Postaccelerator as discussed by the authors, a linear accelerator booster for the upgraded MP-Tandem, has been operational in its extended version since end of 1979, yielding 9.7 MV in CW and 18.5 MV in pulsed mode (duty factor 0.25).
Abstract: The Heidelberg Heavy Ion Postaccelerator, a linear accelerator booster for the upgraded MP-Tandem is operational in its extended version since end of 1979. Yielding 9.7 MV in CW and 18.5 MV in pulsed mode (duty factor 0.25) it has considerably increased the mass and energy range of heavy ions for Nuclear Physics experiments at Heidelberg. The high flexibility of the booster is guaranteed by using 32 independently phased spiral resonators allowing operation of the machine in the mass range of A=10 to A=100 with almost constant accelerating voltage; although even ions as heavy as 197Au have been successfully postaccelerated. Typical examples of postaccele-rated beams are: 164 MeV 12C, 332 MeV 32S, 476 MeV 79Br, 511 MeV 127J and 640 MeV 197Au. Longitudinal and transversal beam quality are tandem like with ?r < 2? mm mrad and ?l < 3.2? MeV .deg., the debunched energy resolution being well below 10-3. The overall availability of the postaccelerator together with the MP-Tandem was 83% of the scheduled user beam time in 1980.
TL;DR: The Advanced Test Accelerator (ATA) as discussed by the authors is a pulsed linear induction accelerator with the following design parameters: 50 MeV, 10 kA, 70 ns, and 1 kHz in a ten-pulse burst.
Abstract: The Advanced Test Accelerator (ATA) is a pulsed linear induction accelerator with the following design parameters: 50 MeV, 10 kA, 70 ns, and 1 kHz in a ten-pulse burst. Acceleration is accomplished by means of 190 ferrite-loaded cells, each capable of maintaining a 250 kV voltage pulse for 70 ns across a 1-inch gap. The unique characteristic of this machine is its 1 kHz burst mode capability at very high currents. This paper describes the pulse power development program which used the Experimental Test Accelerator (ETA) technology as a starting base. Considerable changes have been made both electrically and mechanically in the pulse power components with special consideration being given to the design to achieve higher reliability. A prototype module which incorporates all the pulse power components has been built and tested for millions of shots. Prototype components and test results are described.
TL;DR: In this article, single S-band bunches of 109 electrons have been used to study the characteristics of the SLAC linac in anticipation of its operation as a linear collider.
Abstract: Single S-band bunches of ~ 109 electrons have been used to study the characteristics of the SLAC linac in anticipation of its operation as a linear collider Emittance measurements have been made, the longitudinal charge distribution within single bunches has been determined and transverse emittance growth has been produced by deliberately missteering the beam New equipment is being installed and checked out, and the sensitivity of new traveling-wave beam position monitors has been measured
TL;DR: A superconducting linear accelerator booster is to be added to the existing super FN tandem Van de Graaff accelerator installation at Florida State University to achieve an effective 12 MV additional acceleration voltage as mentioned in this paper.
TL;DR: In this article, the trade-off between optimized shunt impedance and maximum accelerating gradient in structure design is examined and relative advantages of side-coupled and interlaced structures are delineated in the light of much higher permissible internal electric fields.
Abstract: Requirements for straight- and bent-beam medical accelerator configurations are compared. Technical progress of straight-beam accelerators over the past 12 years is reviewed and the trade-off between optimized shunt impedance and maximum accelerating gradient in structure design is examined. Relative advantages of side-coupled and interlaced structures are delineated in the light of much higher permissible internal electric fields, recently demonstrated. A novel concept for a single-section standing-wave structure with multiple photon mode capability is presented.
TL;DR: In this article, the beam energy capability of an electron linear accelerator can be extended by using a magnetic transport system to return the beam after passing once through the accelerator, to the injector end and then "recirculating" the beam through the accelerating structure several times.
Abstract: The beam energy capability of an electron linear accelerator can be extended by using a magnetic transport system to return the beam after passing once through the accelerator, to the injector end and then "recirculating" the beam through the accelerating structure several times. The most important property of the transport system is that it be a good achromat, since operability requirements and beam loading transients usually require at least a few percent energy bandwidth over which the beam will successfully traverse the accelerator during recirculation. The system must also be nearly isochronous, with linear phase-energy correlation corresponding to not more than a fraction of an RF wavelength over a few percent bandwidth and with a small second-order phase-energy correlation coefficient. Such a system to be described in this paper has been designed and is currently under construction for the purpose of recirculating the beam of the 400 MeV Bates Linear Electron Accelerator.
TL;DR: In this paper, a new concept for the linear acceleration of high brightness particle beams, and a description of one working model, is presented, which involves the simultaneous acceleration of a large number of low current beamlets in individual, small bore, electrostatic quadrupole focussing channels.
Abstract: A new concept for the linear acceleration of high brightness particle beams, and a description of one working model, are presented. The idea involves the simultaneous acceleration of a large number of low current beamlets in individual, small bore, electrostatic quadrupole focussing channels. Large total current can be reached.
TL;DR: In this article, a radio frequency quadrupole (RFQ) accelerator at 13.5 MHz for the acceleration of U++ ions from 2.4 to 100 keV/amu has been designed.
Abstract: The radio frequency quadrupole (RFQ) structure has been accepted to be very well suited for the acceleration of light ions at high currents in the low energy range. In case of very heavy ions with low charge the structure is characterized by low r.f. frequencies in the 10 MHz range, and is therefore technically different. An RFQ accelerator at 13.5 MHz for the acceleration of U++ ions from 2.4 to 100 keV/amu has been designed. Problems like current transport capability, emittance growth, validity of calculations are presently studied using a 1:4 proton model.
TL;DR: The Pulselac C accelerator as mentioned in this paper was constructed to study the properties of spacecharge-neutralized ion beams and to demonstrate the feasibility of controlling high ion fluxes, which can supply over 50 A/cm2 of N+ or other intermediate mass ions.
Abstract: The Pulselac C accelerator is being constructed to study the properties of spacecharge-neutralized ion beams and to demonstrate the feasibility of controlling high ion fluxes. A gas-injection plasma gun has been developed which can supply over 50 A/cm2 of N+ or other intermediate mass ions. This source supplies ion flux for the magnetically insulated extraction gap. The source and extractor produce a 100 kV, 5 kA annular ion beam which propagates into a diagnostic region. Diagnostics, including a Thompson parabola mass spectrometer, a magnetic spectrometer, magnetically insulated detectors, and biased charge collectors, have proven the purity and uniformity of the beam and have given preliminary information on its propagation characteristics. Further experiments on the injector will include focusing using a toroidal lens and studies of beam aiming from the extractor gap. Two inductive post-acceleration stages, presently under construction, will increase the beam energy by 500 keV.
TL;DR: In this paper, the authors used the single charge exchange cross section from thin and narrow foils (intercepting 1-3% of the beam) as a line source for measuring the divergence and momentum spectra for operating H- accelerator beams.
Abstract: A novel technique is presented for measuring the six-dimensional beam emittance for high-energy H- accelerators in real time. This techniuqe uses the single charge exchange cross section from thin and narrow foils (intercepting 1-3% of the beam) as a line source for measuring the divergence and momentum spectra for operating H- accelerator beams. By scanning the foil across the beam, X, ?, and p beam density spectra and emittance can be determined. The introduction of a second foil provides the Y-? emittance. Operational experience of this low cost emittance measuring device has been obtained from the 50-MeV H- linear accelerator at Argonne National Laboratory, simultaneously with its use as an injector into the Rapid Cycling Synchrotron (RCS).
TL;DR: The first flash x-ray machine (FXR) at LLNL is scheduled for completion in late 1981 as mentioned in this paper, which is a 54 module linear induction accelerator, designed to deliver 500 Roentgen at 1 m as bremsstrahlung from a 20 MeV, 4 kA, 60 ns pulsed electron beam.
Abstract: The new flash x-ray machine (FXR) at LLNL is scheduled for completion in late 1981. This is a 54 module, linear induction accelerator, designed to deliver 500 Roentgen at 1 m as bremsstrahlung from a 20 MeV, 4 kA, 60 ns pulsed electron beam. The 1.5 MV, cold cathode injector makes use of six accelerator modules as voltage sources. High voltage testing of the accelerator modules and their associated pulse forming lines and Marx banks has been completed, and beam tests of the complete injector assembly are in progress. Design information and preliminary test results are presented.
TL;DR: The Pion Generator for Medical Irradiations (PIGMI) as mentioned in this paper is a compact linear proton accelerator design, optimized for pion production and cancer treatment use in a hospital environment.
Abstract: PIGMI (Pion Generator for Medical Irradiations) is a compact linear proton accelerator design, optimized for pion production and cancer treatment use in a hospital environment. Technology developed during a four-year PIGMI Prototype experimental program allows the design of smaller, less expensive, and more reliable proton linacs. A new type of low-energy accelerating structure, the radio-frequency quadrupole (RFQ) has been tested; it produces an exceptionally good-quality beam and allows the use of a simple 30-kV injector. Average axial electric-field gradients of over 9 MV/m have been demonstrated in a drift-tube linac (DTL) structure. Experimental work is underway to test the disk-and-washer (DAW) structure, another new type of accelerating structure for use in the high-energy coupled-cavity linac (CCL). Sufficient experimental and developmental progress has been made to closely define an actual PIGMI. It will consist of a 30-kV injector, an RFQ linac to a proton energy of 2.5 MeV, a DTL linac to 125 MeV, and a CCL linac to the final energy of 650 MeV. The total length of the accelerator is 133 meters. The RFQ and DTL will be driven by a single 440-MHz klystron; the CCL will be driven by six 1320-MHz klystrons. The peak beam current is 28 mA. The beam pulse length is 60 ps ?s at a 60-Hz repetition rate, resulting in a 100-?A average beam current. The total cost of the accelerator is estimated to be ~$10 million.
TL;DR: In this article, the beam was stacked in the transverse phase space using a horizontal multiturn injection system and the injected ions were then stacked into longitudinal phase space by an RF field.
Abstract: TARN is an accumulation ring of heavy ion beam from the Sector Focusing Cyclotron. In order to obtain a high-intensity stacked beam, both of multiturn injection and RF stacking methods were applied to the TARN. In this injection scheme, about 20 turns of the beam was stacked in the transverse phase space using a horizontal multiturn injection system. The injected beam emittance was about 100 Trmm.mrad. The injected ions were then stacked into longitudinal phase space by an RF field. Since the period for the stacking procedure is limited by the frequency of phase oscillation and the condition of adiabaticity, the repetition rate of RF stacking was 50 %' 100 Hz. The total gain of beam intensity is estimated at about one thousand.