Beam Energy Requirements Research Articles

Design of a cw, low-energy, high-power superconducting linac for environmental applications

The treatment of flue gases from power plants and municipal or industrial wastewater using electron beam irradiation technology has been successfully demonstrated in small-scale pilot plants. The beam energy requirement is rather modest, on the order of a few MeV, however the adoption of the technology at an industrial scale requires the availability of high beam power, of the order of 1 MW, in a cost effective way. In this article we present the design of a compact superconducting accelerator capable of delivering a cw electron beam with a current of 1 A and an energy of 1 MeV. The main components are an rf-gridded thermionic gun and a conduction cooled beta= 0.5 elliptical Nb3Sn cavity with dual coaxial power couplers. An engineering and cost analysis shows that the proposed design would result in a processing cost competitive with alternative treatment methods.

Effects of beam temperature and plasma frequency on the radiation growth rate of a FEL with a laser wiggler

AbstractA linearly polarized laser pulse has been employed as a wiggler in a free-electron laser (FEL) in the presence of a plasma background for generating short wavelength radiation down to the extreme ultraviolet ray and X-ray spectral regions. Introducing plasma background in the FEL interaction region would lessen the beam energy requirement and also enhance both the beam current and the electron-bunching process. This configuration affords the possibility of scaling the device to more compact FELs and would have a higher tunability by changing the plasma density and the temperature of the electron beam. Electron trajectories have been analyzed using single-particle dynamics. The effect of plasma density on electron orbits has been investigated. A polynomial dispersion relation considering longitudinal thermal motion has been derived, by employing perturbation analysis. Numerical studies indicate that by increasing plasma density, the growth rate for groups I and II decreases, while the growth rate for group III increases. In addition, the effect of beam temperature and cyclotron frequency on the growth rate has been discussed. It has been found that by increasing the thermal velocity of the electron beam, the growth rate for groups I and III trivially decreases, while it increases for group II orbits. Besides, an increase in cyclotron frequency cause growth enhancement for group I orbits, while it present a growth decrement for group II and III orbits.

Free-electron laser with a plasma wave wiggler propagating through a magnetized plasma channel

A plasma eigenmode has been employed as a wiggler in a magnetized plasma channel for the generation of laser radiation in a free-electron laser. The short wavelength of the plasma wave allows a higher radiation frequency to be obtained than from conventional wiggler free-electron lasers. The plasma can significantly slow down the radiation mode, thereby relaxing the beam energy requirement considerably. In addition, it allows a beam current in excess of the vacuum current limit via charge neutralization. This configuration has a higher tunability by controlling the plasma density in addition to the γ-tunability of the standard FEL. The laser gain has been calculated and numerical computations of the electron trajectories and gain are presented. Four groups (I–IV) of electron orbits have been found. It has been shown that by increasing the cyclotron frequency, the gain for orbits of group I and group III increases, while a decrease in gain has been obtained for orbits of group II and group IV. Similarly, the effect of plasma density on gain has been exhibited. The results indicate that with increasing plasma density, the orbits of all groups shift to higher cyclotron frequencies. The effects of beam self-fields on gain have also been demonstrated. It has been found that in the presence of beam self-fields the sensitivity of the gain increases substantially in the vicinity of gyroresonance. Here, the gain enhancement and reduction are due to the paramagnetic and diamagnetic effects of the self-magnetic field, respectively.

SU-E-T-438: Optimal Proton Beam Energy to Treat Adult CNS, Adult Head and Neck, and Pediatric Cancers.

Proton therapy machines with lower beam energy requirements are expected to be easier and more cost-efficient to design, construct, and operate, particularly when using novel proton acceleration technology (e.g., dielectric wall). We determine, for adult central nervous system (CNS) and head and neck (HN) and pediatric cases, the optimal proton beam energies that can lead to clinically acceptable plan quality. Proton treatment plans for various adult CNS and HN and pediatric cases, previously treated at our institution using helical tomotherapy, were generated using a commercial planning system (XiO, v. 4.62, Elekta) with a passively-scattered proton beam model. Proton beam orientations were chosen such that the distance from the skin to the distal target edge was minimal; however, beams could not pass through areas with significant surface irregularity (e.g. ear), nor through OARs with strict dose limitations (e.g. lens). For a given beam direction, the planning system would calculate an optimum range and modulation to cover a given target volume. Beam weights were adjusted so that 95% of the target volume received the prescribed dose. All plans were limited to two proton beams. An optimal proton energy exists for each case studied. Among all cases, target dose conformity (the ratio of target volume to volume encompassed by theprescribed dose) ranged from 0.74 to 0.94, and target dose uniformity (the ratio of the D5 and D95 doses) ranged from 1.01 to 1.04, with the optimal proton energies. Among the CNS and HN cases and for most pediatric cases, the maximum proton energy required was 133 MeV. For a pediatric abdomen case, 159 MeV protons were required. For protontreatment of most adult CNS and HN and pediatric cases, the optimal energies that are capable of generating good quality plans are only as high as 130 MeV.

Use of Mini-Mag Orion and superconducting coils for near-term interstellar transportation

Interstellar transportation to nearby star systems over periods shorter than the human lifetime requires speeds in the range of 0.1–0.15 c and relatively high accelerations. These speeds are not attainable using rockets, even with advanced fusion engines because at these velocities, the energy density of the spacecraft approaches the energy density of the fuel. Anti-matter engines are theoretically possible but current physical limitations would have to be suspended to get the mass densities required. Interstellar ramjets have not proven practicable, so this leaves beamed momentum propulsion or a continuously fueled Mag-Orion system as the remaining candidates. However, deceleration is also a major issue, but part of the Mini-Mag Orion approach assists in solving this problem. This paper reviews the state of the art from a Phases I and II SBIT between Sandia National Laboratories and Andrews Space, applying our results to near-term interstellar travel. A 1000 T crewed spacecraft and propulsion system dry mass at .1 c contains ∼ 9 × 10 21 J . The author has generated technology requirements elsewhere for use of fission power reactors and conventional Brayton cycle machinery to propel a spacecraft using electric propulsion. Here we replace the electric power conversion, radiators, power generators and electric thrusters with a Mini-Mag Orion fission–fusion hybrid. Only a small fraction of fission fuel is actually carried with the spacecraft, the remainder of the propellant (macro-particles of fissionable material with a D-T core) is beamed to the spacecraft, and the total beam energy requirement for an interstellar probe mission is roughly 10 20 J , which would require the complete fissioning of 1000 ton of Uranium assuming 35% power plant efficiency. This is roughly equivalent to a recurring cost per flight of 3.0 billion dollars in reactor grade enriched uranium using today's prices. Therefore, interstellar flight is an expensive proposition, but not unaffordable, if the nonrecurring costs of building the power plant can be minimized.

Interstellar propulsion opportunities using near-term technologies

Interstellar transportation over periods shorter than the human lifetime requires speeds in the range of 0.2–0.3 c. These speeds are not attainable using rockets, even with advanced fusion engines. Anti-matter engines are theoretically possible but current physical limitations would have to be suspended to get the mass densities required. Interstellar ramjets have not proven practicable, so this leaves beamed momentum propulsion as the remaining candidate. This paper reviews the state of beamed-momentum in-space propulsion and presents a point design system suitable for human exploration of nearby stars using today's physics and resources known to exist in the solar system. The total beam energy requirement for an interstellar probe mission is roughly 10 20 J , which would require the complete fissioning of one thousand tons of uranium assuming 35 percent power plant efficiency. This is roughly equivalent to a recurring cost per flight of 3.0 billion dollars in reactor grade enriched uranium using today's prices. Therefore, interstellar flight is an expensive proposition, but not unaffordable, if the nonrecurring costs of building the power plant can be minimized.

Cost considerations for interstellar missions

This paper examines the technical and economic feasibility of interstellar exploration. Three candidate interstellar propulsion systems are evaluated with respect to technical viability and compared on an estimated cost basis. Two of the systems, the laser-propelled lightsail (LPL) and the particle-beam propelled magsail (PBPM), appear to be technically feasible and capable supporting one-way probes to nearby star systems within the lifetime of the principal investigators, if enough energy is available. The third propulsion system, the antimatter rocket, requires additional proof of concept demonstrations before its feasibility can be evaluated. Computer simulations of the acceleration and deceleration interactions of LPL and PBPM were completed and spacecraft configurations optimized for minimum energy usage are noted. The optimum LPL transfers about ten percent of the laser beam energy into kinetic energy of the spacecraft while the optimum PBPM transfers about thirty percent. Since particle beam generators are roughly twice as energy efficient as large lasers, the PBPM propulsion system requires roughly one-sixth the busbar electrical energy a LPL system would require to launch an identical payload. The total beam energy requirement for an interstellar probe mission is roughly 10 20 joules, which would require the complete fissioning of one thousand tons of Uranium assuming thirty-five percent powerplant efficiency. This is roughly equivalent to a recurring cost per flight of 3.0 Billion dollars in reactor grade enriched uranium using today's prices. Therefore, interstellar flight is an expensive proposition, but not unaffordable, if the nonrecurring costs of building the powerplant can be minimized.

Exotic sources of X-rays for iodine K-edge angiography

Digital subtractive angiography has been performed to image human coronary arteries using wiggler radiation from electron storage rings. The significant medical promise of this procedure motivates the development of smaller and less costly X-ray sources. Several exotic sources are candidates for consideration, using effects such as Cherenkov, channeling, coherent bremsstrahlung, laser backscattering, microundulator, parametric, Smith-Purcell, and transition radiation. In this work we present an analysis of these effects as possible sources of intense X-rays at the iodine K-edge (33.169 keV). The criteria we use are energy, efficiency, flux, optical properties, and technical realizability. For each of the techniques, we find that they suffer either from low flux, a low energy cutoff, target materials heating, too high electron beam energy requirement, optical mismatch to angiography, or a combination of these. We conclude that the foreseeable state-of-the-art favors a compact storage ring design (H. Wiedemann et al., these Proceedings (8th Nat. Conf. on Synchrotron Radiation Instrumentation, Gaithersburg, MD, USA, 1993) Nucl. Instr. and Meth. A. [1]).

Commercial Production of Radioisotopes for Nuclear Medicine, 1970-1980

The first small cyclotrons were installed for commercial production of radioisotopes at New England Nuclear Corporation, Billerica, Massachusetts, and at Medi-Physics, Emeryville, California. Both machines were Cyclotron Corporation Cs-22 multiple particle, fixed energy cyclotrons. In the ten years that followed, the total number of commercial radioisotope producing small accelerators has grown to ten, with four more projected for 1981. The beam energy requirement for the first accelerators was modest; 22 MeV protons, 12 MeV deuterons, 24 MeV He-4, and 31 MeV He-3; and commercial radioisotope production for nuclear medicine utilized all four particles. The first product available from cyclotron production was fluorine-18 from the 16O(3He, p)18F reaction. Injected intravenously as no-carrier-added Na18F, the radionuclide quickly concentrated in bone, providing the nuclear medicine physician with diagnostic information on skeletal abnormalities including metastatic bone disease. Following in quick succession were 67Ga from 68Zn(p, 2n)67Ga, 111In from 112Cd(p, 2n)111In, 43K from 40Ar(α, p)43K, 123I from 122Te(d, n)123I, and 81Rb from 82Kr(p, 2n)81Rb. The next few years saw one radionuclide, 43K, disappear from the marketplace, and two others, 18F and 81Rb, disappear, and then reappear, although not for the purposes originally intended. More recently, the widespread demand for 201Tl for imaging myocardial perfusion has led to increased requirements for beam energies higher than those from the original small cyclotrons.

Neutral-beam requirements for compression-boosted ignited tokamak plasmas

Neutral-beam energies of 200 to 500-keV D0 may be required to ensure adequate penetration into the centre of ignition-sized tokamak plasmas. However, the beam energy requirement can be reduced by using a start-up scenario in which the final plasma is formed by major-radius compression of a beam-heated plasma whose density-radius product, na, is determined by satisfactory neutral-beam penetration. “Compression boosting” is attractive only for plasmas in which nτE increases with na, because a major-radius compression C increases na by C3/2. This paper analyses the dependence on C of beam energy and beam power for plasmas which obey “empirical scaling laws” of the type nτE∝(na)2. The dependences on C of stored magnetic energy and TF-coil power dissipation are also determined. It is found that a compression ratio of 1.5 to attain the ignited plasma permits adequate penetration by ·150-keV D0 beams.

Heating of a large CTR-tokamak by neutral-beam injection

The start-up of a large CTR tokamak plasma at low density using energetic neutral beams is studied. Questions of beam-energy deposition profiles, beam-energy requirements for penetration, and beam-power requirements to achieve ignition or prescribed plasma heat-up rates are examined. A detailed analysis for a particular CTR-system design, using a two-fluid, space-time numerical model to simulate plasma behaviour, is reported. The numerical model includes neoclassical ion conduction, pseudoclassical electron conduction, radiation losses, Ohmic heating, thermonuclear alphaparticle heating, and injection heating. It is found that even when the power density deposition profile for beam heating is peaked on the axis, the plasma temperature profiles can have local maxima and thus be inverted in the outer plasma regions. This is caused by the decreased density in these zones. For a specific large system studied in detail (aspect ratio 2.6, plasma radius 500 cm, initial peak density 3 × l013/cm3), beam energies of 100 keV, 350 keV, and 500 keV are considered. Only the 500-keV beam case yields non-inverted temperature profiles during heating. In all cases, moderate power levels are required to ignite low-density plasmas in times of the order of seconds. In addition, the injection time required to establish a prescribed plasma heat-up rate is examined in detail. In some cases, for a given amount of injected energy, the heat-up rate resulting from low-energy beams is greater than that due to higher-energy beams. Beam-energy and -power requirements for smaller systems are also given.