Showing papers on "Linear particle accelerator published in 1995"

The Stanford linear accelerator polarized electron source

Abstract: The Stanford 3-km linear accelerator at SLAC has operated exclusively since early 1992 using a polarized electron beam for its high-energy physics programs. The polarized electron source now consists of a diode-type gun with a strained-lattice GaAs photocathode DC biased at high voltage and excited with circularly polarized photons generated by a pulsed, Ti:sapphire laser system. The electron polarization at the source is > 80%. To date the source has met all the beam requirements of the SLC and fixed target programs with < 5% downtime.

The LCLS: A fourth generation light source using the SLAC linac

Abstract: Recent technological developments make it possible to consider use of the Stanford linear accelerator to drive a linac coherent light source (LCLS)—a laser operating at hard x‐ray wavelengths. In the LCLS, stimulated emission of radiation would be achieved in a single pass of a high‐energy, extremely bright electron beam through an undulator, without the optical cavity resonator normally used in storage ring‐based free‐electron lasers. The x‐ray laser beam would be nearly diffraction limited with very high transverse coherence, and would exhibit unprecedented peak intensity and peak brightness, and sub‐picosecond pulse length. Such an x‐ray source offers unique capabilities for a large number of scientific applications.

X‐ray source and the output factor

Abstract: When the collimator setting of a linear accelerator is made sufficiently small, the output factor in air, R, is greatly reduced because the collimators obstruct the periphery of the x‐ray source. This has been utilized to examine the size of the source by varying the width y of a narrow field and determining how R(y) varies. The source diameters in the two principal directions were clearly influenced by the design of the accelerators. The x‐ray sources of two accelerators with bending magnets were found to be noncircular while that of a linear accelerator without a magnet showed circular symmetry. The position of the source relative to the axis of collimator rotation was determined by measuringR for offset narrow fields. For one of the accelerators, the source was initially moving and off the central axis by about 2 mm for the first five monitor units. The results correlated well with sharpness in portal–film images. The technique can serve to evaluate the major source characteristics in acceptance testing and quality control.

Linear accelerator for radiation chemistry research at Notre Dame

Abstract: An 8 MeV, S-band linear accelerator has been delivered to Notre Dame by Titan Beta Corporation. This accelerator utilizes a variety of techniques to provide uniform dose repeatability, very low dark current, and high beam current over a range of pulse widths from 2 ns to 1.5 s. This paper describes the design and results of tests.

Cluster-surface interaction at high kinetic energy. I. Electron emission

Abstract: The electron emission resulting from a collision of accelerated clusters and a solid surface was measured. The charged, mass selected clusters were accelerated to high velocities (3–100 km/s) in a linear accelerator. The quantum yield for electron emission as well as their kinetic energy distribution were measured. These measurements allow an estimate of kinetic to internal energy conversion.

Superconducting cyclotron and target for use in the production of heavy isotopes

Abstract: A superconducting cyclotron (1) has four superconducting magnetic coils (2, 3, 4, 5) surrounding a chamber (10). Within the chamber upper and lower sets of soft iron pole pieces (11, 12) are positioned to provide an accelerating particle beam space (13) therebetween. The pole pieces (11, 12) interact with the magnetic field generated by the superconducting coils (2, 3, 4, 5). Cavity resonators (14, 15, 16, 17) are also located within the chamber (10) to generate an RF oscillating voltage across the beam space (13). A linear accelerator (30) is provided axially aligned with the magnetic field of the superconducting magnetic coils to pre-accelarate the ionised particles before the ionised particles are injected into the beam space (13). In this way much higher beam currents may be obtained. A target which may be used to produce heavy isotopes utilising the higher beam currents generated by the cyclotron relies substantially upon radiative cooling during isotope production.

Commissioning and performance of the HIMAC medical accelerator

Abstract: Heavy ions show the excellent dose concentration especially at a position located deep in a human body. This character of heavy ions are well suited for the medical treatment of the cancer. A heavy ion synchrotron complex, HIMAC, has been constructed at NIRS for this purpose. The HIMAC accelerator consists of an injector linac, a couple of synchrotron rings, long and complicated beam transport lines, three treatment rooms and four experimental rooms. The maximum energy of the synchrotron is determined so that the residual range of silicon ions exceeds 30 cm in water. The clinical trials of the cancer treatment started on June 21 using a 290 MeV/u carbon beam, and 21 patients were treated by the end of February 1995.

Design considerations on a proton superconducting linac

Abstract: The authors analyze the longitudinal motion of a single proton in a superconducting linear accelerator. They derive the linearized equations of motion, and develop a matrix formalism to represent the progress of motion. The goal is to provide a tool which can be easily included in a computer code for the design of superconducting proton linacs. In particular they determine the stability conditions, and the amount of motion mismatch resulting from the presence of drift insertions, and from the rate of acceleration. Space-charge effects have not been included in the analysis. They complement the analysis with considerations of the rf and cryogenic power requirements, of the pulsed mode of operation, and of the beam transverse confinement. They conclude with an example of a Spallation Neutron Source.

Superconducting cyclotron for use in the production of heavy isotopes

Abstract: A superconducting cyclotron is provided that includes a superconducting magnet. This superconducting magnet is arranged to provide a magnetic field that extends axially through a chamber which includes a radially extending beam space. There is further an interaction within the chamber between the axially extending magnetic field and RF energy that energizes particles that are circulating within the beam space. There is further a linear accelerator that is aligned with and exposed to the axially extending magnetic field of the superconducting cyclotron. The output of this linear accelerator communicates with an input to the beam space so that the particles for acceleration within the beam space are pre-accelerated by the linear accelerator.

A 3-stage cyclotron complex for driving the Energy Amplifier

Abstract: The goal of this accelerator complex is to provide a 10 MW proton beam for driving the Energy Amplifier recently proposed by C. Rubbia. It is lower (by one order of magnitude) than the requirements of most of the accelerator-driven projects based on c-w linacs. Therefore, the requirements for the Energy Amplifier open an alternative solution based on ring cyclotrons producing a continuous beam. Thus taking into account the present development of high-intensity cyclotrons, a three-stage cyclotron accelerator is a possible solution. It comprises of: (1) the injector(s) which should be able to deliver a 10 mA beam in a given phase width-a solution based on two 5mA compact isochronous cyclotrons working in parallel is proposed; (2) the intermediate stage which is a four-separated-sector cyclotron accelerating the injected beam up to 120 MeV; and (3) the final booster which has ten separated sectors and six cavities raising the kinetic energy up to about 1000 MeV.

Interactions between neighboring beams in a heavy ion fusion reactor chamber

Abstract: Multiple beams in a heavy ion fusion reactor chamber can increase the beam spot size at the target. Each beam experiences the field from nearby beams and this field varies along the bunch length. These field variations cause different parts of the beam to be focused at different locations and results in a larger spot size at the target. Calculations show that this is not a large effect for a beam generated by an induction linear accelerator in which the current is nearly constant over much of the pulse. These calculations show 90%–99% of the charge reaches the target for a radiation converter radius that is 10%–20% larger than the beam radius.

Radiation beam scanner

Abstract: A radiation beam scanner system employs a peak detection methodology to measure the intensity and distribution of radiation produced by a medical linear accelerator. The scanner system combines the capability to perform scanning measurements with the capability to perform high accuracy calibrations of the linear accelerator. The system employs two ion chamber detectors, signal and reference, with the signal detector positioned within a tank of water (phantom tank). As the water is irradiated by the linear accelerator, the signal detector is continuously moved within the water by means of electrical stepper motors as the reference detector remains stationary at some point within the radiation beam. The reference detector output is compared to a predetermined threshold and, when the threshold is reached, a peak detector circuit monitors the signal detector output for a radiation pulse peak. Accelerator anomalies are eliminated by calculating a ratio of the signal detector output to the reference detector output. Each ratio is time tagged and correlated to signal detector position information, thereby providing a map of the distribution and intensity of the radiation within the water. The resultant data is evaluated by a qualified medical physicist to ascertain the accelerator's suitability for use in dosimetry. In one embodiment, the pulse frequency of the accelerator is determined and the rate of signal detector movement (scan rate) is set as a function of the pulse frequency of the accelerator. The system includes a unique, integrating, auto-zeroing, calibration electrometer that can be employed to calibrate the accelerometer.

An investigation into the comparison between different dosimetric methods of measuring profiles and depth doses for dynamic wedges on a Varian 600C linear accelerator.

Abstract: Three dosimetric methods for commissioning the dynamic wedges on a Varian 600C linear accelerator operating at 4.7 MV were compared. The techniques involved the use of ionization chambers, X-ray verification film and solid state detectors. Ionization chambers gave the most accurate results, as expected, but data acquisition was very time consuming. Film dosimetry was found to have good spatial resolution for beam profiles, but problems were encountered with the acquisition of depth doses. Solid state detectors generally showed reasonable agreement with the ionization chambers.

The SLAC high-density gaseous polarized 3He target☆

Abstract: A large-scale high-pressure gaseous 3 He polarized target has been developed for use with a high-intensity polarized electron beam at the Stanford Linear Accelerator Center. This target was used successfully in an experiment to study the spin structure of the neutron. The target provided an areal density of about 7 × 10 21 nuclei/cm 2 and operated at 3 He polarizations between about 30% and 40% for the six-week duration of the experiment.

Progress toward a prototype recirculating induction accelerator for heavy-ion fusion

Abstract: The US Inertial Fusion Energy (IFE) Program is developing induction accelerator technology toward the goal of electric power production using heavy-ion beam-driven inertial fusion (HIF) The recirculating induction accelerator promises driver cost reduction by repeatedly passing the beam through the same set of accelerating and focusing elements We present plans for and progress toward a small (45-m diameter) prototype recirculator, which will accelerate K/sup +/ ions through 15 laps, from 80 to 320 keV and from 2 to 8 mA Beam confinement is effected via permanent-magnet quadrupoles; bending is via electric dipoles Scaling laws, and extensive particle and fluid simulations of the space-charge dominated beam behavior, have been used to arrive at the design An injector and matching section are operational Initial experiments are investigating intense-beam transport in a linear magnetic channel; near-term plans include studies of transport around a bend Later experiments will study insertion/extraction and acceleration with centroid control

Vibration studies of the Stanford Linear Accelerator

Abstract: Vibration measurements of the linear accelerator structures in the SLC linac show a 1 micron RMS vertical motion. This motion reduces to 0.2 micron RMS motion when the cooling water to the accelerator structures is turned off. The quadrupoles have 250 nanometer RMS vertical motion with the accelerator structure cooling water on and 60 nanometer motion with it off. These results together with measurements of the correlations as a function of frequency between the motions of various components are presented.

Single-bunch and multibunch electron beam generation for FEL experiments with the 38 MeV L-band linear accelerator at ISIR

Abstract: The generation of multibunch electron beams used for FEL oscillation experiments with the 38 MeV L-band linear accelerator at The Institute of Scientific and Industrial Research has been studied. Originally, the components of the accelerator system have been optimized for generating a high-brightness single-bunch beam. The operational conditions of the system have been investigated for a multibunch beam. A multibunch beam with a macropulse length of 4 μs has been accelerated at energies of 17 to 19 MeV. The latter part of the pulsed beam with a length of 1.8 μs has an energy spread of 1.8%. The charge per bunch is 2 nC. The beam of this part has been successfully used for oscillation experiments at a wavelength of 32 to 40 μm.

Los Alamos high‐power proton linac designs

Abstract: Proton accelerators for driving transmutation applications have beam power requirements in the range 40 MW to 400 MW, which corresponds to energy and current performance requirements in the range 800 MeV to 1600 MeV, and 50 mA to 250 mA. Linear accelerator designs aimed at providing these performance levels have been studied at Los Alamos for the past few years. Appropiate accelerator architectures have been developed, using the existing technology base for water‐cooled‐copper linacs, and key technical issues have been identified and addressed.

A versatile, high-power proton linac for accelerator driven transmutation technologies

Abstract: We are applying the new coupled-cavity drift-tube linac (CCDTL) to a conceptual design of a high-current, CW accelerator for transmutation applications. A 350-MHz RFQ followed by 700-MHz structures accelerates a 100-mA proton beam to 1 GeV. Several advantages stem from four key features: (1) a uniform focusing lattice from the start of the CCDTL at about 7 MeV to the end of the linac, (2) external location and separate mechanical support of the electromagnetic quadrupole magnets, (3) very flexible modular physics design and mechanical implementation, and (4) compact, high-frequency structures. These features help to reduce beam loss and, hence, also reduce potential radioactivation of the structure. They result in easy alignment, fast serviceability, and high beam availability. Beam funneling, if necessary, is possible at any energy after the RFQ.

Free-electron laser oscillation with a multibunch electron beam of the 38 MeV L-band linear accelerator at ISIR

Abstract: Free-electron laser oscillation has been achieved with a multibunch electron beam generated with the 38 MeV L-band linear accelerator at The Institute of Scientific and Industrial Research in Osaka University. The wavelengths of the observed FEL are 32 to 40 μm for energies of the electron beams of 17 to 19 MeV. The macropulse length of the beam is 1.8 μs. The net FEL gain measured at a wavelength of 40 μm is 25%. The tuning range of the length of the optical cavity and the FEL spectra have also been measured. The total output FEL energy of 12 mJ has been obtained in the recent experiments at a wavelength of 40μm. The intracavity peak power of the FEL is estimated to be about 150 MW.

Beam dynamics issues in an extended relativistic klystron

Abstract: Preliminary studies of beam dynamics in a relativistic klystron were done to support a design study for a 1 TeV relativistic klystron two-beam accelerator (RK-TBA), 11.424 GHz microwave power source. This paper updates those studies. An induction accelerator beam is modulated, accelerated to 10 MeV, and injected into the RK with a RF current of about 1.2 kA. The main portion of the RK is the 300-m long extraction section comprised of 150 traveling wave output structures and 900 induction accelerator cells. A periodic system of permanent quadrupole magnets is used for focusing. One and two dimensional numerical studies of beam modulation, injection into the main RK, transport and longitudinal equilibrium are presented. Transverse beam instability studies including Landau damping and the "Betatron Node Scheme" are presented.

On the use of CsK2Sb photocathodes in RF linacs

Abstract: The use of CsK 2 Sb photocathodes in an RF linear accelerator is investigated. Several fabrication techniques for this type of cathodes are reviewed. Measurements are performed on the drop in quantum efficiency due to the use of the cathode in the linac at several wavelengths in the visible. A better lifetime has been found for shorter wavelengths. Finally, the effect of high energy laser pulses on the quantum efficiency in the green is demonstrated.

The S-band Linear Collider Test Facility

Abstract: The S-Band Linear Collider Test Facility under construction at DESY will serve as a unique test bed for the necessary technical developments of a large scale 2/spl times/250 GeV e/sup +/e/sup -/ linear accelerator. The test facility consists of two modular units similar to those to be installed in a Linear Collider tunnel. The questions of Higher Order Mode excitation, measurement, damping and feedback on the accelerating cavity and the quadrupole position are especially important and have to be addressed in order to understand the most crucial aspect of a 15 km linear accelerator namely the beam stability. Simultaneously the performance of the newly developed rf-systems is investigated. The status of this set-up is presented.

The Argonne Wakefield Accelerator high current photocathode gun and drive linac

Abstract: The Argonne Wakefield Accelerator (AWA) is a new facility for advanced accelerator research. A major component of the AWA is its drive linac, consisting of a unique high current short pulse L-band photocathode based gun and special standing wave preaccelerator designed to produce 100 nC, 30 ps electron bunches at 20 MeV. Commissioning on the drive linac is now underway. We report on our initial operating experience with this novel machine, including bunch length and emittance measurements.

Method and apparatus for controlling the acceleration energy of a radio-frequency multipole linear accelerator

Abstract: A method for controlling a particle acceleration energy in a radio-frequency quadrupole accelerator, the method being particularly adapted for ion implantation in the process of manufacturing semiconductor devices, wherein the particle acceleration energy is varied without the necessity of changing the resonant frequency of the RFQ accelerator so that the final energy of the particles has a plurality of distinct energy having a lower value than the designed voltage.

Accelerator archeology-the resurrection of the Stanford Mark III electron linac at Duke

Abstract: In the early 1960s, the Mark III accelerator at the Stanford High Energy Physics Laboratory was used as the prototype test-bed for the SLAC two-mile accelerator. In the mid 1980s, the accelerator was dismantled and a large part of it was transported to the Duke University Free-Electron Laser Laboratory to form the basis of the injector for the 1-GeV Duke Storage Ring. The plan was to use the original accelerator sections and some RF equipment with new magnetic optics, vacuum system, gun and a modern control system. The first 295-MeV portion of the linac is now operational at Duke. The linac currently consists of eleven sections from the old linac with a single-cell RF gun. Our guiding principal has been one of economy and simplicity. We have not attempted to restore the accelerator to its original form, but have added modem components where necessary. We discuss some of the more interesting features of the linac, and how we have given new life to this venerable machine here at Duke.

Halos of intense proton beams

Abstract: Beam halo is an important issue for accelerator driven transmutation technologies and other applications of CW proton accelerators. These projects include, for example, the accelerator transmutation of waste, accelerator-based conversion of plutonium, accelerator production of tritium, and the development of a next-generation spallation neutron source. To keep radioactivation within acceptable limits these accelerators must operate with a very low beam loss (less than a nanoampere per meter). Beam loss is associated with the presence of a low density halo far from the beam core. Understanding the physics of halo production and determining methods to control beam halo are important to these projects. In recent years significant advances have been made, both analytically and computationally. In the following we describe recent developments in beam halo theory and simulation, including results from multi-million particle simulations.

Parametric study of an X-ray FEL

Abstract: An FEL utilizing a high energy, high current and low emittance beam to produce radiation shorter than 2Ais investigated in this paper. This device is an extension of the previously proposed 40ALinac Coherent Light Source based on the Stanford linear accelerator. Here we investigate the performance characteristics and parameter sensitivities of this single pass, high gain FEL amplifier operating by self-amplified spontaneous emission (SASE). We begin by comparing various approaches to this short wavelength source and justify our choice of a helical undulator operating on the fundamental frequency. Numerical simulations as well as extensions of previous studies are used to show performance as a function of undulator parameters, startup noise, emittance, focusing, current and energy spread. Further studies and parameter modifications are proposed where needed.

The Pohang light source

Abstract: A 2 GeV synchrotron light source project is in progress in Pohang, Korea. The light source is designed to provide high brightness radiation with continuous wavelengths down to 1 A (10-8 em) with its peak at 4·43 A(Le. 2·8 keY). The project, consisting of a full energy injector linear accelerator and a 2 GeV storage ring, was launched in 1988 and is scheduled to be completed by the end of 1994. In this article, we introduce the main features and status of the storage ring components and the installation procedure. Radiation characteristics and beamline status are also described.