Induction Linac Research Articles

Achromatic beam combiner and bend system for ILSE

The lattice configuration of the beam combiner and bend system of the proposed induction linac system experiment (ILSE) is described. These subsystems

Induction linac drivers: prospects for the future

This review is intended to place in perspective our current view of the parameter ranges for induction linac drivers that lead to attractive scenarios

Theoretical and experimental investigations of a neutralized ion induction linac for inertial confinement fusion

Studies of an induction linac for space-charge-neutralized beams, comprising an injector and two induction stages with magnetoinsulating cusps in the a

A review of free-electron lasers

Free-electron laser (FEL) theory and experiments are reviewed. The physical mechanism responsible for the generation of coherent radiation in the FEL is described and the fundamental role of the ponderomotive wave in bunching and trapping the beam is emphasized. The relationship of the FEL interaction to the beam–plasma interaction is pointed out. Various FEL operating regimes are discussed. These include the high-gain Compton and Raman regimes, both with and without an axial guiding magnetic field. The linear and nonlinear regimes are examined in detail, with particular emphasis on techniques for achieving efficiency enhancement. The quality of the electron beam used to drive FEL’s is a critical factor in determining their gain and efficiency. The subject of electron beam quality, for different accelerators, is discussed. Key proof-of-principle experiments for FELs in an axial guiding magnetic field, as well as those driven by induction linacs, rf linacs, electrostatic accelerators, and storage rings, are reviewed. Finally, the requirements on wigglers and resonators are discussed.

Experiment and theory on CO2 laser powered wiggler and induction linac FEL

As an electromagnetic wiggler experiment, CO2 laser light (100 J/100 ns) is injected into a high current electron beam (1 kA, 0.5 MeV). Scattered visible light (λ = 8000-5000 Å) is observed. From the spontaneous emission power the gain for the CO2 laser powered FEL is estimated.The induction linac for the FEL which is developed at our institute and the FEL driven by the induction linac are also reported.

Guided radiation beams in free electron lasers

In a free electron laser (FEL), the radiation field, wiggler field and electron beam resonantly couple and modify the refractive index in the vicinity of the electron beam, such that the radiation beam will tend to focus upon the electron beam. From the radiation envelope equation derived from the source dependent expansion (SDE) method of solving the 3-D wave equation in FELs, conditions and parameters necessary to achieve guided radiation beams (constant radius) in the Compton exponential gain regime are obtained for FELs driven by either induction linacs or rf linacs with various transverse profiles of the electron beam. From the efficiency of the guided radiation beam, the trapping potential of the ponderomotive potential prior to saturation and the required beam quality of the electron beam can be obtained. The wiggler field could be tapered to further increase the operating efficiency. The possibility of bending or steering radiation beams in FELs is discussed and a condition necessary for radiation guiding along a curved electron beam orbit is obtained.

The Livermore Free-Electron Laser Program Magnet Test Laboratory

Test Laboratory supports the ongoing development of the Induction Linac Free-Electron Laser and uses magnetic-field measurement systems that are useful in the testing of long-period magnetic structures, electron-beam transport magnets, and spectrometer magnets. The major systems are described which include two three-axis Hall probe-and-search coil transports with computer-controlled data acquisition; an automated-search coil system used to detect very small inaccuracies in wiggler fields; a nuclear-magnetic-resonance (NMR)-based Hall probe-calibration facility; and a high-current DC ion source using heavy ions of variable momentum to model the transport of high-energy electrons. A high-precision electron-beam-position monitor, under development for use within long wigglers, that has a positional resolution of less than 100 mu m is discussed briefly.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Development of the strong electromagnet wiggler

A description is given of the design approach used for a permanent magnet-assisted electromagnet under development as part of the Induction Linac Free-Electron-Laser program. A single-period schematic of the wiggler is described. This device is an iron-core, DC electromagnet in which poles of identical magnetic scalar potential are attached to large iron plates. These scalar potential busses are bridged by iron plates around which the large primary coils are wound. Smaller trim coils that provide the magnetic-field taper are placed at the base of the poles. Permanent-magnet material, magnetized in a direction opposite to that of the field created by coils, is placed between the poles. The magnetic scalar potential of the poles can be elevated to the desired point while delaying the onset of magnetic saturation in the iron. Data are presented from a seven-period prototype wiggler that has been designed, fabricated and tested. >

An Induction Linac Driven Heavy-Ion Fusion Systems Model

A computerized systems model of a heavy-ion fusion (HIF) reactor power plant is presented. The model can be used to analyze the behavior and projected costs of a commercial power plant using an induction linear accelerator (Linac) as a driver. Each major component of the model (targets, reactor cavity, Linac, beam transport, power flow, balance of plant, and costing) is discussed. Various target, reactor cavity, Linac, and beam transport schemes are examined and compared. The preferred operating regime for such a power plant is also examined. The results show that HIF power plants can compete with other advanced energy concepts at the 1000-MW(electric) power level (cost of electricity (COE) --50 mill/kW . h) provided that the cost savings predicted for Linacs using higher charge-state ions (+3) can be realized. The induction Linac driver is still a major component of the total capital cost (43%), but it no longer appears that large 4000-MW(electric), $5 billion (1984) power plants will be required to make the economics of HIF look favorable. More importantly, the results also indicate that there are several different combinations of target and reactor cavity options that lead to COEs within 10% of the overall minimum. The induction Linac's highermore » efficiency (>20%) is able to compensate for changes in target concept (gain) and cavity type with minimal change in COE. The potential cost reductions and apparent flexibility identified by this study together with the established performance data base from present-day accelerators are leading to renewed interest in induction Linacs for near-term target development applications.« less

Authors

Authors

U.S. Heavy-Ion Fusion Systems Assessment Project Overview

A multi-institutional study was conducted to evaluate the potential of heavy-ion induction Linacs as inertial confinement fusion (ICF) drivers. This Heavy-Ion Fusion Systems Assessment (HIFSA) study was a U.S. effort to evaluate a wide range of possible system configurations for electric power plants driven by induction Linacs, as opposed to the radio-frequency accelerators used in previous heavy-ion fusion (HIF) power plant conceptual designs. In contrast to these earlier studies, the HIFSA project specifically avoided concentrating on a point design. Rather, cost/performance models of the major systems in an HIF power plant were devised by the institutions with expertise in the applicable technologies (e.g., Lawrence Berkeley Laboratory for induction accelerators and beam transport/focus; McDonnell Douglas Astronautics Company for cost scaling and systems modeling/intergration). (Detailed descriptions of these systems and associated integration/trade-off studies appear in other papers in this special issue.) Some of the key results of the HIFSA study are summarized and their significance assessed. The cardinal conclusions of the study are twofold: (a) Conceptual HIF power plants have estimated cost-of-electricity (COE) values that, at 1 GW (electric), are roughly comparable to those from other ICF and magnetic fusion system studies; and (b) HIF technology is robust in that there existsmore » a large parameter space region in which the COE is close to the minimum; i.e., the minima in COE are broad.« less

Heavy-Ion Linear Induction Accelerators as Drivers for Inertial Fusion Power Plants

A linear induction accelerator that produces a beam of energetic heavy ions (T -- 10 GeV, A -- 200 amu) is a prime candidate as a driver for an inertial fusion power plant. Some early perceptions were that heavy-ion drive fusion would not be cost-competitive with other power sources because of the high cost of the accelerators. However, improved understanding of the physics of heavy-ion transport and acceleration (supported by experimental results), combined with advances in accelerator technology, have resulted in accelerator design costs -- 50% of previous estimates. As a result, heavy-ion drive fusion power plants are now projected to be cost-competitive with other conceptual fusion power plants. A brief formulation of transport and acceleration physics is presented here, along with a description of the induction Linac cost optimization code LIACEP. Cost trends are presented and discussed, along with specific cost estimates for several accelerator designs matched to specific inertial fusion target yields. Finally, a cost-effective strategy using heavy-ion induction Linacs in a development scenario for inertial fusion is presented.

Heavy-Ion Fusion Systems Assessment Implications for Reactors

The requirements, desirable characteristics, trade-offs, and design constraints are discussed for commercial heavy-ion fusion (HIF) reactor plants with induction linear accelerator (Linac) drivers. The trade-offs and the design constraints when the reactor plant requirements and desirable characteristics conflict with those for other HIF power plant systems are described. The reactor plant concepts included in the Heavy-Ion Fusion Systems Assessment (HIFSA) are discussed in relation to these requirements, characteristics, trade-offs, and constraints. Four reactor plant concepts were included in the HIFSA studies to provide large ranges of reactor repetition rate and target yield accommodation (1 to 20 Hz and 150 to 3000 MJ). This permitted thorough exploration of the impact on HIF cost of electricity (COE) of the high repetition rate and efficiency advantages of induction Linacs. Contrary to pre-HIFSA expectations, large plants with large driver repetition rates and multiple reactors are not required for attractive COE: Repetition rates <10 Hz in 1000-MW(electric) one-reactor plants are competitive. More than one HIF reactor plant concept shows promise: The minimum COE estimates for the four concepts in 1000-MW(electric) plants range from 55 to 75 mill/kW-h. Cost and/or technological problems in one part of reactor operating parameter space need not be fatal for HIF: The estimated COE is within 5% of the minimum over wide ranges of the repetition rate and the target yield for a fixed plant size and reactor concept.

Applications of induction linacs to free-electron lasers and particle beams

Applications of induction linacs to free-electron lasers and particle beams

Recent results from the naval research laboratory experimental FEL program

The Naval Research Laboratory has been very active in the development of high-power, millimeter-centimeter wavelength FELs. These devices have been operated as amplifiers, superradiant amplifiers, and as an oscillator. The amplifier experiments demonstrated power gains of 50 dB with > 3% efficiency (with no enhancement), and superradiant experiments produced 75 MW pulses at λ = 4 mm with 6% efficiency. These experiments were performed using a 1 2 MeV pulse line accelerator having a 50 ns pulse duration. Most recently, an induction linac having a 2 μs pulse duration has been employed for oscillator experiments. This work has demonstrated steady-state operation for 1 μs at power levels up to 10 MW. The initial power gain per pass is as large as 10 4, so that turn-on occurs rapidly. This device has operated with various mirror configurations, including a Bragg resonator. The experimental results agree well with recent theoretical work, which predicts efficiencies > 20% in a tapered wiggler oscillator. These results are also directly applicable to the operation of a two-stage FEL experiment.

Pulsed ion sources for accelerator inertial fusion

Experimental results are reported on an extractor for pulsed, high-intensity beams of intermediate mass ions. Aluminum and indium plasmas were generated using a metal vapor vacuum arc. A method for electrostatic separation of ions from electrons at the anode was utilized to generate constant current beams, insensitive to plasma flux variations.A maximum extraction voltage of 30 kV was applied across a 1·6 cm gap. Voltage pulse length ranged from 10 to 50μsec. Peak current densities of 15 mA/cm2 and normalized emittance of εn&lt;3χ10-7; π-m-rad were achieved for Al+ and In+ from a 20-cm2 anode. Ions were predominantly in the +1 ionization state with no observable species contamination. The technology may have application to the induction linac approach to Accelerator Inertial Fusion.

Accelerator research for heavy ion inertial fusion

It is now one decade since serious consideration was first given to the use of heavy ion accelerators for inertial confinement fusion. After an initial period of wide-ranging studies, the US program settled on an induction linac method proposed by Lawrence Berkeley Laboratory (LBL). The ion kinetic energy is modest (30–100 MeV/amu, 5–10 GeV total) but intense beam currents of order 1 kA per beam in 10–30 beams are required on target in a short pulse of order 10–20 ns. In this review the conceptual designs are described, together with recent theory and experiments on high-current beam transport and use of multiple beams. Parallel efforts in West Germany, Japan and the Soviet Union are mentioned, and a two-year US study of heavy ion fusion electric power plants is summarized.

Pulsed Power Opening Switch Research at the University of New Mexico

Opening switch research at the University of New Mexico (UNM) is directed toward moderate-current (~10 kA) devices with potential applications to high-power charged particle accelerators. Two devices with the capacity for controlling gigawatt high-voltage circuits, the grid-controlled plasma flow switch and the scanned-beam switch, are under investigation. Both switches are conceptually simple; they involve little collective physics and are within the capabilities of current technology. In the plasma flow switch, the flux of electrons into a high-voltage power gap is controlled by a low-voltage control grid. Plasma generation is external to, and independent of, the power circuit. In the closed phase, plasma fills the gap so that the switch has a low on-state impedance. Pulse repetition rates in the megahertz range should be feasible. In single-shot proof-of-principle experiments, a small area switch modulated a 3-MW circuit; a 20-ns opening time was observed. The scanned-beam switch will utilize electric field deflection to direct the power of a sheet electron beam. The beam is to be alternately scanned to two inverse diodes connected to output transmission lines. The switch is expected to generate continuous-wave pulse trains for applications such as high-frequency induction linacs. Theoretical studies indicate that 10-GW devices in the 100-MHz range with 70-percent efficiency should be technologically feasible.

A Comparison of the Design and Costs of Induction Linac Drivers for Inertial Fusion Using Ions of Mass 133 and 200

Optimized cost estimates for induction linac accelerators using mass 133 ions at a charge state of +2 producing inertial fusion target yields of 300, 600, and 1200 MJ are presented. The ions are injected into the accelerator at 3 MV, and accelerated to the required voltage appropriate to the desired target yield. A cost comparison of these drivers is made with drivers using mass 200, charge state +3 ions for several target yields and a fusion power of 3000 MW.

Heavy-Ion Fusion: Future Promise and Future Directions

The previous papers in this heavy-ion fusion special session have described work performed as part of the Heavy-Ion Fusion Systems Assessment (HIFSA) Project. Key technical issues in the design and costing of targets, induction linacs, beam transport, reactor, balance of plant, and systems integration have been identified and described. The HIFSA systems model was used to measure the relative value of improvements in physics understanding and technology developments in many different areas. Within the limits of our 1986 knowledge and imagination, this study defines the most attractive heavy-ion fusion (HIF) power plant concepts. The project has deliberately avoided narrowing the focus to a point facility design; thus, the generic systems modeling capability developed in the process allows for relative comparisons among design options. We will describe what are thought to be achievable breakthroughs and what the relative significance of the breakthroughs will be, although the specific mechanism for achieving some breakthroughs may not be clear at this point. This degree of optimism concerning such breakthroughs is probably at least as conservative as that used in other fusion assessments.