High Duty Factor Research Articles

A standing-wave structure for a synchrotron ring injector

A stand-alone linear accelerator is the simplest injector for a synchrotron ring. It is the appropriate choice for the injection of high current at high duty factors. This paper examines design parameters of a single-structure standing-wave linac, made from on-axis coupled cavities, operated in stored-energy mode, as a simple high-current, high-duty-factor, synchrotron ring injector.

Induction-linac based free electron laser amplifier for fusion applications

We describe an induction-linac based free electron laser amplifier design for producing multi-megawatt levels of microwave power for electron cyclotron resonance heating of tokamak fusion devices such as the Compact Ignition Tokamak or the International Thermonuclear Experimental Reactor. The wiggler design strategy incorporates a tapering algorithm suitable for FEL systems with moderate space charge effects and minimizes spontaneous noise growth at frequencies below the fundamental, while enhancing the growth of the signal at the fundamental. In addition, engineering design considerations of the waveguide wall loading and electron beam fill factor in the waveguide set limits on the waveguide dimensions, the wiggler magnet gap spacing, the wiggler period, and the minimum magnetic field strength in the tapered region of the wiggler. This FEL is designed to produce an average power of about 10 MW at frequencies in the range from 280 to 560 GHz. The achievement of this average power at a reasonable cost requires a high duty factor, which affects some component design. In addition, the desire to obtain a high extraction efficiency pushes the beam energy up and requires magnetic field strengths in the wiggler that are near or possibly larger than the Halbach limit. We used a methodology for our system study that had been developed earlier. We considered several FEL configurations and selected one that minimized total cost. We determined that increasing the beam energy requires that the wiggler use vanadium-permendur as the pole material. We discuss the basic design of the selected configuration and give the expected performance.

電子ビーム加工の研究 アルミナグリーンシートの穴あけ特性

This paper deals with the electron beam drilling of alumina green sheet. The following results were obtained through some experiments by multi-pulse drilling under various duty factors and a thermal calculation. (1) The number of beam pulse does not affect the diameter and taper of drilled hole. Furthermore, hole taper is kept constant for various value of workpiece thickness when drilling are performed in same conditions. (2) Hole diameter and taper increase dramatically at high duty factor even though drilling conditions are kept constant. (3) Material removal in the drilling of green sheet is taken place through scattering of surrounding material by explosive vaporization of organic binding material in the green sheet. (4) The increase in hole diameter and taper is due to the focal movement taken place through the space charge neutralization by positive ions generated by the ionization of vaporized gas.

Aqueous Solutions of Organic Compounds as Dielectrics for EDM Sinking

Use of aqueous solutions of organic compounds as a medium for EDM sinking almost completely excludes any fire hazard, permitting safe operation of plant in the second and third shifts. Although addition of organic compounds often considerably increases the attainable removal rate as compared to that for pure deionized water, the removal rate at low concentrations remains significantly less than that possible with hydrocarbons. This drawback must be seen in relation to the advantage that relative wear at high discharge currents is practically halved. Additionally, surface roughness is lower when water dielectrics are used, although the corrosive effect of aqueous working media must be taken into account when processing steels. In the present study, the best results were obtained with a highly concentrated aqueous glycerine solution. Working media containing glycerine are at an advantage as compared to hydrocarbon dielectrics when working with long pulse durations and high pulse duty factors and discharge currents, i.e. in the roughing range with high open-circuit voltages and a positively polarised tool electrode. A change to graphite electrodes permitted a further significant improvement in working results. The glycerine dielectric proved superior to the hydrocarbon medium for roughing at optimised parameters in the parameter range under investigation.

The 150-MeV photon tagging system at Sendai

A description is given of the 32-channel photon tagging system recently constructed at the Laboratory of Nuclear Science. Tohoku University. Some results of photonuclear experiments performed using this system in conjunction with the high duty factor electron beam from the pulsed beam stretcher are presented.

Methods in Relativistic Nuclear Physics

M Danos, V Gillet and M Cauvin 1984 Amsterdam: North-Holland x + 302 pp price Dfl200 ISBN 0 444 86317 6 For many topics in traditional nuclear physics a nonrelativistic treatment is adequate. However, this is not the case when discussing meson exchange current effects, high momentum components of nuclear wavefunctions revealed by the illumination provided by the new generation of high duty factor electron accelerators or relativistic heavy-ion collisions.

Coincidence techniques for high energy electron induced multiparticle breakup experiments

A new generation of electron accelerators is coming on-line with high duty factors, high currents, and energies in the range of a few hundred MeV to several GeV. One of the major motivations for these accelerators has been the desire to perform coincidence experiments in electron-induced nuclear breakup reactions. Some recent experiments are reviewed, and the planning of new experiments, including out-of-plane detection, is examined.

CEBAF — a high energy, high duty factor electron accelerator for nuclear physics

The Nuclear Science Advisory Committee has recommended the construction of the Continuous Electron Beam Accelerator Facility (CEBAF) as proposed by the Southeastern Universities Research Association (SURA), a consortium of more than thirty institutions in the southeastern United States. The accelerator will be capable of delivering intense ( I ave > 100 μA), quasi-continuous (duty Factor > 90%) beams of electrons with energies up to 4.8 GeV. Short (1.2 μs), intense ( I pk = 200 mA) pulses of electrons will be accelerated by passing twice through a conventional pulsed linac. The pulses then will be injected into and stored in a pulse stretcher ring, the circumference of which is close to the length of the electron pulse. During the period between pulses (1ms) the stored electrons will be extracted to yield a high duty factor beam. Delivery of arbitrarily polarized beams will be possible. Experimental facilities will include three end stations. Two will be used for experiments utilizing the primary electron beam; the third will serve as a tagged photon facility.

Thermomechanical evaluation of poloidal divertor plates for a long-pulse experiment

The Tokamak de Varennes experiment comprises a double-null poloidal divertor and intends studying in a high duty factor sequence, discharges for times of up to 30 s, each discharge lasting between 100 ms and 1 s, with a 15 min interval between sequences. A total energy of up to 6 MJ has to be absorbed by the divertor plates resulting from a constant loading by an exponential power distribution on either side of the separatrix (260 W/cm 2 peak power with 2 cm width outside the separatrix and 0.2 cm inside). Energy removed from plasma is in present experiments stored in divertor plates and removed from these between successive discharges. Active cooling of plates is required for high heat-flux density and also for long pulse discharges. This paper examines various materials for inertial cooling. Two designs based on active cooling are also presented. It is found that inertial cooling is insufficient, active cooling of the plates during and in-between sequences being necessary.

Overview of CW Electron Accelerator Proposals

Electron beams in the MeV to GeV energy range have been used for nuclear studies for the last thirty years. The precision of measurements made using electrons is sufficiently high that they are also now used as starting points for the analysis of data obtained using strongly interacting probes such as pions and protons. Virtually all measurements made to data have been of the inclusive variety. Enhancing the precision of such measurements, through such means as more accurate particle differentiation and improved time resolution, has meant making the duty factor of the beam as high as possible. The global interest in high duty factor electron accelerators has consequently risen. This paper groups both existing and proposed high duty factor accelerators into three categories. The first group covers those involving a pulsed accelerator and a pulse stretcher ring. The second category consists of machines based on the microtron concept. The third group includes the recirculated linac. The current proposals for high duty factor accelerators are divided into two groups: those involving the upgrade of an existing pulsed accelerator and those involving the construction of a new accelerator. The proposals for new accelerators are further categorized into those based on linac pulsemore » stretcher combinations and those based on microtrons. This paper assesses the existing and proposed activities of these facilities as they currently stand at laboratories around the world.« less

Multi-GeV Electron Linac-Pulse Stretcher Design Options

The Linac-Pulse Stretcher Ring system is evaluated as a design for a high duty factor (> 90%), intense (240 ?A), electron accelerator for operation in the 0.5 to multi-GeV (> 4 GeV) region. Options within this system are discussed in light of their predicted initial and operational cost, flexibility, and reliability. The ramifications of the choice of a particular cavity type, accelerating gradient, repetition rate, beam pulse length, and number of beam recirculations for the linac design are discussed both with respect to the linac itself and to the Pulse Stretcher Ring. The Pulse Stretcher Ring concept is analysed in terms of injection schemes (single or multi-turn), extraction methods (half or third integer, chromatic or achromatic), and operation parameters (machine tune and chromaticity).

A Proposal for a High Current, High Duty Factor Electron Accelerator

A linac-Pulse-Stretcher-Ring has been proposed for the generation of high duty factor, high current electron beams in a nominal energy range of 0.5 to 2.0 GeV. A low duty factor linac beam is injected into a storage ring from which it is slowly extracted to yield a high duty factor. The linac beam is composed of 1.2 ?s current pulses containing 240 nC/pulse with a repetition rate of 1 kHz. Each pulse is injected vertically during a single turn into the pulse stretcher ring, a 377.89 m oval with a magnetic radius of 29 m. Excitation of an n/3 betatron resonance in the horizontal plane is used in conjunction with electric and magnetic septa for extraction. Typical extracted beam parameters are: horizontal emittance ?0.37? mm-mrad, vertical emittance ?0.l? mm-mrad, and an energy spread ?0.1%. The extracted beam has a maximum average current of 240 ?A, a duty factor >90%, and may be polarized. Beam characteristics, design parameters, and facility layout are discussed.

Experimental Investigation of Heating Phenomena in Linac Mechanical Interfaces from RF Field Penetration

In a high duty-factor, high-current, drift-tube linear accelerator, a critical interface exists between the drift-tube stem and the tank wall. This interface must provide vacuum integrity and RF continuity, while simultaneously allowing alignment flexibility. Because of past difficulties with RF heating of vacuum bellows and RF joints encountered by others, a paucity of available information, and the high reliability requirement for the Fusion Materials Irradiation Test (FMIT) accelerator, a program was initiated to study the problem. Because RF heating is the common failure mode, an attempt was made to find a correlation between the drift-tubestem/linac-tank interface geometry and RF field penetration from the tank into the interface region. Experiments were performed at 80 MHz on an RF structure designed to simulate the conditions to which a drift-tube stem and vacuum bellows are exposed in a drift-tube linac. Additional testing was performed on a 367-MHz model of the FMIT prototype drift-tube linac. Experimental results, and a method to predict excessive RF heating, is presented. An experimentally tested solution to the problem is discussed.

Performance of the MEA Solid-State High Duty Factor Modulator

The MEA 500 MeV electron linac is powered by 12 solid-state 10% duty factor line type modulators. Repetition rates up to 2000 Hz, pulse widths of 50 microsec. and RF peak power up to 4 M.W. at 2856 MHz have been obtained. Some of the modulators have been used for several thousands of hours, performance will be presented. Special attention will be given to the freon cooling system.

The LBL Wideroe-Based Heavy Ion Injector Project

The LBL Wideroe-based high-intensity heavy-ion injector for the SuperHILAC will be operational by April 1981. It will provide several emA of low charge state ions up through uranium at high duty factor to the SuperHILAC. Several of the subsystems have already operated to specification and will be described.

A Conceptual Design of a Linac-Stretcher Ring to Obtain a 2-GeV Continuous Electron Beam

In order to obtain a high duty factor, > 100 μA 2-GeV electron beam, we have designed a linac-stretcher ring system. The system is an attractive option because it draws heavily on the existing accelerator technology. The linac-stretcher ring consists of a 2-GeV SLAC-type pulsed linac which injects into a storage ring. In between linac pulses, the stored electron beam is to extract resonantly. This design differs from those discussed recently in several important respects. The storage ring includes an RF system whose purpose is to control the beam orbit and rate of extraction from the ring. With an RF system in the ring, the injection scheme consists of a few turns of synchronous transfers of beam between the linac and storage ring.

A Novel Power Supply for High Duty Factor Kicker Magnets

A Novel Power Supply for High Duty Factor Kicker Magnets

Polarization transfer in elastic electron scattering from nucleons and deuterons

We present a description, including relevant formulas and numerical estimates, of a set of polarization transfer experiments which appear to offer a feasible way to separate the deuteron charge and quadrupole form factors and measure the neutron and proton electric form factors. The experiments require a 2 to 4 GeV high-intensity, high-duty factor, longitudinally polarized electron beam and require that the polarization of the recoiling hadron be measured in a second, analyzing, scattering. The relevant asymmetries are fairly large, and our calculations show that they are sensitive to different models obtained from existing data. Attention is called to the fact that the proposed deuteron measurements will require new 10% measurements of vector and tensor analyzing powers of deuterons with kinetic energy from 150 to 450 MeV.

A Fast Beam Protection System

The MEA 500 MeV high duty factor electron linac has been designed to accelerate electrons eventually on a pulse-to-pulse base. Each beam pulse may have a different current and/or energy and may serve one or several experimental beam lines. The usual beam protection sprstems impose limitations on this multiuser scheme. Due to good emittance of the electron beam, a very fine beam spot may be focussed accidentally on an unwanted place, causing damage within 50 microsec. Therefore a system has been developped which provides reliable beam shut-off within less than 10 microsec. Copper protection collimators positioned at crucial places will intercept a faulty beam. The gamma rays produced will then induce current in a special downstream compton battery, which is part of the emergency injector stop-line. More than 50 units have been installed to protect beam lines, vacuum valves, beam monitors, etc.

Multitarget interleaved tracking for phased-array radar

Use of multiple active devices in phased-array radars to generate r.f. power is becoming more interesting, owing to the technical advantages of solid-state components. Because the solid-state components have peak-power limitations instead of the mean-power limitations of traditional components, it is more cost effective to transmit signals with a high duty factor. Furthermore, one of the most important features of phased-array radars is the capability of performing simultaneous tracking on several targets. A method of interleaving pulse sequences for the multitarget tracking function, thus using a high duty factor, is reported. In particular, a technique of selecting the pulse repetition frequency (p.r.f.) and the transmission frequency is described, depending on the estimated radial velocity of each target, its accuracy, clutter spectral characteristics, and the interleaving algorithm efficiency. A simulation has been performed to evaluate the packing efficiency as a function of the pulse length, the duty factor of the transmitter, the number of targets and their range distribution. Consequently, a typical partitioning of the radar frame time among the different functions (tracking, search, confirmation etc.) has been determined for fixed and rotating phased-array antennas. Finally, an evaluation of computer loading to implement multitarget tracking is given.