Maximum Beam Power Research Articles

Neutronic and thermo-mechanic calculations for the design of the TRADE spallation target

The spallation target of the TRADE Project—at present in stand-by waiting for further decisions on budget availability—is based on the concept of a solid target cooled by forced convection. The solid target approach presents a maximum power density limitation due to the high thermal stresses which are generated by the huge differential temperatures in the material. These at their turn stem from the proton energy loss in the volume of the target material and the water cooling on the external surface. The maximum operating beam power and the proton beam profile were imposed by experimental and geometrical considerations; the peak power density of the target material (Tantalum) turned out to be about 8E09 W/m 3. The power generation of the reference configuration of the spallation target was accurately calculated by the code MCNPX, which allows to simulate individual particle tracks in 3-D geometry, starting from the accelerated 140 MeV protons down to all the relevant secondary particles. The temperature distribution and the stress and strain maps were calculated by the thermo-mechanical ANSYS code. The main calculation results are reported. The elastic-plastic analysis of the target material is performed in terms of maximum allowable deformation, fatigue and progressive plastic deformation.

Prescriptions for optimizing intensities of short-lived RIBs at ISOL based research facilities

In order to generate useful intensities of short-lived radioactive species at Isotope Separator On-Line (ISOL) based research facilities, species of interest must be diffused from the interior of the production target-material, effusively transported to an ion source, ionized, extracted, mass-analyzed, and accelerated to research energies in times commensurate with their lifetimes. The intensities at such facilities are principally limited by decay losses associated with times required for diffusion-release from target materials and transport from the target to the ion source and by the maximum permissible primary beam power depositional density that can be tolerated without deleteriously affecting target integrity or ion source efficiency. Consequently, it is imperative to minimize delay times associated with the independent diffusion and effusive-flow processes by choosing small dimensioned (short-diffusion length) highly refractory target materials and formatting them in highly permeable mechanically and thermally robust structures that can withstand high-power beam irradiation for extended periods of time. This article provides basic information on methods, procedures and principles for selecting target materials; for designing fast diffusion-release targets; for designing fast effusive-flow vapor transport systems; and introduces methods for controlling target temperatures as required for optimizing intensities of short-lived radioactive ion beams at ISOL based research facilities.

Design, performance and construction of a 2 MW ion beam test facility for plasma facing components

A new facility for the testing of plasma facing components (PFC) under high heat fluxes is presently under construction at IPP Garching. The aim of this facility is to provide thermal testing capabilities for high heat loaded divertor components which have both active water cooling and large outer dimensions. The water-cooled test chamber is equipped with two ion sources for positive ion beam production. Initially, only one of the two individually controlled RF ion sources with 1.1 MW maximum beam power will be used for heat loading tests within an operating regime from 5 to 65 MW/m 2 at the target position. This paper presents the details of the technical characteristics and the systems for vacuum generation, cooling, power supply, control, target diagnostics and data acquisition.

Signal Parameter Estimation for Sparse Arrays

For arrays with a small number of elements, such as those deployed in infrasound detection, the theoretical pattern of beam power associated with the incidence of a plane wave shows a broad main beam with strong side lobes. A novel approach to the estimation of the parameters of the incoming wave field is proposed based on the exploitation of the full beam pattern for the array. The pattern of beam power over a limited mask of beam points in slowness space is compared with the theoretical predictions over a set of narrow frequency bands and the set of signal parameters that give the best fit determined by an inversion using a Neighbourhood Algorithm (NA). The angle of incidence and azimuth provide a convenient parameter set since they can be used to include corrections for elevation differences between the sensors in the process of beamforming. Because the theoretical beam pattern depends only on the array geometry and frequency band, it can be computed on a dense grid and interpolation carried out to provide the beam power across the beam mask for a specified set of angular parameters. The NA inversion with an L 1.3 measure of misfit in beam power is able to achieve good definition of the minimum misfit with only 120 trials, and the level of fit itself provides a good measure of the validity of the model of a single dominant plane wave. The NA approach is supplemented by a contracting grid method using a set of self-similar grid masks that can rapidly locate the position of maximum beam power. The two methods provide a valuable tool for real-time analysis, with both independent estimates of the angular parameters and a measure of the quality of the results. Manuscript received 5 November 2002.

Electron-beam radiolysis of gaseous propane in the presence of water under circulation conditions

The paper describes the data obtained from the study of electron-beam radiolysis of gaseous propane in the presence of water under circulation conditions on pilot-scale facility with electron accelerator UEVK “Avrora-9B” (energy 0.5 MeV, maximum beam power 40 kW). It was obtained that irradiation leads to the formation of condensable alkanes and oxygen-containing organic compounds (predominantly alcohols and ethers). The dependencies of their content in the formed mixture on cooling conditions, dose, and gas flow rate were measured. The mechanism of the formation of the mentioned compounds was discussed.

Commissioning of the new GSI high current linac and HIF related RF linac aspects

The new 1.4 MeV/u front end of the Unilac accelerates ions with A/ q ratios up to 65 and with beam intensities in mA up to 0.25 A/ q. The maximum beam power is 1300 kW, the normalized 90% emittance areas are around 0.55 π mm mrad. The layout of the 91 MV linac as well as the results from Ar 1+ beam measurements along the whole system are quite important for the design of a HIF-relevant RF driver linac. A concept for a 250 mA, Bi 1+ test injector with four beamlets is developed at present, which could serve as a HIF driver front end element.

Combined electron-beam and coagulation purification of molasses distillery slops. Features of the method, technical and economic evaluation of large-scale facility

The paper summarizes the results obtained from the study on combined electron-beam and coagulation method for purification of molasses distillery slops from distillery produced ethyl alcohol by fermentation of grain, potato, beet and some other plant materials. The method consists in preliminary mixing of industrial wastewater with municipal wastewater, electron-beam treatment of the mixture and subsequent coagulation. Technical and economic evaluation of large-scale facility (output of 7000 m 3 day −1) with two powerful cascade electron accelerators (total maximum beam power of 400 kW) for treatment of the wastewater by the above method was carried out. It was calculated that the cost of purification of the wastes is equal to 0.25 US$ m −3 that is noticeably less than in the case of the existing method.

10MeV 25KW industrial electron LINAC

A 10MeV 25KW plus class electron LINAC was developed for sterilisation of medical devices. The LINAC composed of a standing wave type single cavity prebuncher and a 2m electro-plated travelling wave guide uses a 5MW 2856MHz pulse klystron as an RF source and provides 25KW beam power at the Ti alloy beam window stably after the energy analysing magnet with 10MeV plus-minus 1 MeV energy slit. The practical maximum beam power reached 29 KW and this demonstrated the LINAC as one of the most powerful S-band electron LINACs in the world. The control of the LINAC is fully automated and the “One-Button Operation” is realised, which is valuable for easy operation as a plant system. 2 systems have been delivered and are being operated stably.

New electron beam facility for irradiated plasma facing materials testing in hot cell

Since plasma facing components such as the first wall and the divertor for the next step fusion reactors are exposed to high heat loads and high energy neutron flux generated by the plasma, it is urgent to develop plasma facing components which can resist these. We have established electron beam heat facility (‘OHBIS’, Oarai hot-cell electron beam irradiating system) at a hot cell in JMTR (Japan materials testing reactor) hot laboratory in order to estimate thermal shock resistivity of plasma facing materials and heat removal capabilities of divertor elements under steady state heating. In this facility, irradiated plasma facing materials (beryllium, carbon based materials and so on) and divertor elements can be treated. This facility consists of an electron beam unit with the maximum beam power of 50 kW and the vacuum vessel. The acceleration voltage and the maximum beam current are 30 kV (constant) and 1.7 A, respectively. The loading time of the electron beam is more than 0.1 ms. The shape of vacuum vessel is cylindrical, and the main dimensions are 500 mm in inside diameter, 1000 mm in height. The ultimate vacuum of this vessel is 1 × 10 −4 Pa. At present, the facility for the thermal shock test has been established in a hot cell. The performance of the electron beam is being evaluated at this time. In the future, the equipment for conducting static heat loadings will be incorporated into the facility.

Preliminary research concerning the use of electron accelerators to improve the conservability and to extend the shelf-life of fruits and vegetables

The potential of ionizing radiation treatment for food preservation, shelf-life extension, control of microbial load and reduction of pathogenic microorganism was demonstrated. The irradiations were performed under normal conditions on the Institute of Physics and Technology for Radiation Device's linear electron accelerator, which has the following parameters: 5 μA mean beam current, 6 MeV electron mean energy, pulse period 3.5 μs and dose rates between 100–1500 Gy/min. This research project was aimed at assuring the consumer's acceptance for radiation-treated food and to obtain a significant reduction of food losses. We also propose a promising solution for the radiation processing of some bulk food products at the place of storage, consisting of a mobile electron accelerator. The main characteristics of the mobile electron accelerator are: electron energy 3 to 5 MeV, maximum beam power 5 kW, vertical electron beam; irradiation is possible both with electron beams and with bremsstrahlung. The results of our preliminary research lead to the conclusion that electron-beam irradiation and the use of electron accelerators is a promising solution for food preservation and food safety. Interesting future applications are outlined.

Performance of jaeri electron beam irradiation stand

Abstract The electron beam facility was constructed to test and develop plasma facing components. Maximum beam power reaches 400 kW. The facility has a plasma electron gun which is the largest one in the world. The power supply of the facility utilizes high-frequency invertors as a beam switching system. The plasma electron gun and power supply system were developed on the basis of neutral beam injectors for JT-60. Heating time ranges from 1 ms to continuous operation. Maximum head flux is over 2000 MW/m2, and heating area is up to 1800 cm2. The heating area can be changed by a number of grid apertures. The facility can produce intense heat loads at off-normal events such as disruption, and steady-state heat loads on the divertor and the first wali at normal operations.

Two-dimensional focusing of self-magnetically insulated “Plasma Focus Diode”

A new and simple type of self-magnetically insulated, vacuum ion diode named “Plasma Focus Diode” has been successfully developed with a large solid angle of irradiation and low divergence angle. The diode has a pair of coaxial cylindrical electrodes similar to a Mather-type plasma focus device. Ion-current density of 1·9 kA/cm2 has been obtained on the anode surface under the experimental conditions of diode voltage ∼1·4 MV, diode current ∼180 kA, and pulse width ∼75 ns. The generated ion beam has been two-dimensionally focused (line focusing) with a focusing radius of ∼0·18 mm, giving a maximum ion current density and beam power density at the axis of ∼0·14 MA/cm2 and ∼0·18 TW/cm2, respectively. The motion of electrons in the gap has been numerically simulated by use of a newly developed particle-in-cell computer simulation code, and good agreement has been obtained between the simulation and the experiment.

Longitudinal and Transverse Space Charge Limitations on Transport of Maximum Power Beams

The maximum transportable beam power is a critical issue in selecting the most favorable approach to generating ignition pulses for inertial fusion with high energy accelerators. Maschke and Courant1 have put forward expressions for the limits on transport power for quadrupole and solenoidal channels. We have included in a more general way the self consistent effect of space charge defocusing on the power limit. The results show that no limits on transmitted power exist in principal. In general, quadrupole transport magnets appear superior to solenoids except for transport of very low energy and highly charged particles. Longitudinal space charge effects are very significant for transport of intense beams.

Design Equations for Dynamitron Type Power Supplies in the Megavolt Range

The power supply which is used as the accelerating potential for megavolt Dynamitron accelerators is a parallel-fed, series-cascaded rectifier system. Low frequency RF voltage is capacitively coupled into the cascaded rectifier system by means of an SF-6 gas insulated electrode configuration. Maximum voltage attained with this configuration has been 5.7 MV. Maximum current attained has been 20 mA. Maximum beam power attained has been 40 kW. This paper covers the development of equations which express the operational input parameters such as, oscillator plate voltage, current, and power in terms of the required output high voltage and load current, and the internal circuit parameters such as, tank capacitance, tank inductance resistance, number of rectifier stages, and oscillating frequency. Calculated data from these equations agree closely with experimental data. This analysis allows the optimization of a power supply design in terms of critical parameters for a given maximum output voltage and load current.

An Experimental Investigation of a High‐Voltage Electron‐Bombardment Ion Thruster

The performance of a mercury electron‐bombardment thruster at large values of net accelerating potential is described. A 20‐cm diameter thruster was tested at values of ion beam current and net accelerating potential up to 0.165 amp and 70 kv, respectively. A maximum beam power of about 10 kw was obtained. The maximum supportable electric field strength between accelerator grids was approximately constant at for spacings between 0.5 and 3.0 cm. The ion chamber performance was qualitatively similar to that at low accelerating voltage. The energy dissipated per beam ion in the ion‐chamber discharge was related to the percentage of Child's law ion current extracted over a wide range of accelerator spacings and potentials. The maximum percentages of Child's law current transmitted were about 60 and 80% for thrusters with 20 and 7.5‐cm diameter accelerator grids, respectively, and were essentially independent of grid spacing and thickness. Ion focusing characteristics, at ion beam current densities of about 10 amp/m2, indicated that the ratio of center‐to‐center grid spacing to grid thickness should be between about 2.5 and 4 to avoid direct ion impingement.The power efficiency was measured and found to be consistent with data taken with low voltage thrusters operated at similar conditions. A power efficiency of 0.8 was obtained at a net accelerating potential of 18 kv and rose to 0.88 at a net accelerating potential of 36 kv. Over‐all thruster efficiencies of about 0.80 and 0.82 were obtained at net accelerating potentials of 28 and 36 kv, respectively.

Water Cooled Targets for Intense Ion Beams

Target backings cooled by water in linear flow have proven capable of dissipating heat loads from 2 kW ion beams focused to about 20 mm2 for extended periods without structural failure. In addition to the more obvious modes of failure by plastic deformation and melting, metallographic studies of damaged targets have revealed deep void penetrations along grain boundaries. The targetry limitations imposed on maximum usable beam power by heat transfer from the backing to the cooling fluid have been investigated. Neutron producing lifetimes of LiF targets have been compared for different proton beam and coolant flow conditions.

ジルコニウムおよびジルカロイ-2合金の電子ビーム溶接に関する研究

A high-voltage electrcn-beam welding machine with a maximum beam power of 1.5 kw (50 kV, 30 mA) has been operated in the Japan National Research Institute for Metals since July 1960. With this equipment, the characteristics of bead penetration and welded joints of Zirconium and Zircaloy-2, namely, microstructure, hardness, tensile and bending properties and corrosion resistance against high temperature, high pressure water studied as compared with the case of TIG welding, and the following conclusions were obtained :(1) It is possible to make a butt-joint weld at a high welding speed such as 40 to 100cm/min up to about 2.0 mm thickness of sheet.(2) Relationship between specific weld heat input and ratio of bead penetration-to-width is given by following equation. w/p X 100=76 log H-45(3) About three times the specific weld heat input of electron beam welding is necessary for TIG welding to give the same bead penetration.(4) To make a smooth and not-burn - through welding bead, it may be supposed that a low voltage type power source should be preferred type, especially, for a thin sheet.(5) No evidence has been found to substantiate the occurrence of a change in oxygen and nitrogen composition due to this welding process.(6) Metallography, hardness, mechanical-property evaluations and corrosion tests have revealed satisfactory properties in Zirconium and Zircaloy-2 wleded joints by this welding process.