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Considerations involved in the design of negative-ion-based neutral beam systems

Description: We consider the requirements and constraints for negative-ion-based neutral beam injection systems, and show how these are reflected in design considerations. We will attempt to develop a set of guidelines for users and developers to use to see how well (in a qualitative sense, at least) a particular neutral beam system fits a particular proposed need.
Date: November 1, 1983
Creator: Cooper, W.S.
Partner: UNT Libraries Government Documents Department

Summary of the status of negative-ion-based neutral beams

Description: Negative-ion-based neutral beam systems can perform multiple functions for fusion reactors, such as heating, current drive in tokamak reactors, and establishing and maintaining potential barriers in tandem mirror reactors. Practical systems operating continuously at the 200 keV, 1 MW level can be built using present-day technology. Ion sources have been demonstrated that produce D/sup -/ beams with <5% electron content, and that operate at linear current densities that are within a factor of 2 of what conservatively designed accelerator/transport structures can handle. Concepts are in hand for transporting the negative ion beam through a neutron maze before neutralization, thus permitting a radiation-hardened beamline. With an advanced laser photoneutralizer, overall system power efficiencies of 70% should be possible. A national program is being planned to achieve the goal of application of 475 keV systems on a mirror ETR in 1994.
Date: January 1, 1983
Creator: Cooper, W.S.
Partner: UNT Libraries Government Documents Department

Two-dimensional linacs

Description: We describe several schemes for rf acceleration of ribbon beams. (Although the ribbon edges of course, need to be focussed, these configurations are essentially 2-D.) They allow simpler modeling than quadrupole systems and, if operable, provide good matching to certain types of ion sources and beam neutralizers. We discuss four possible configurations, in chronological order of conception: (1) an rf linac with dc transverse field focussing; (2) a similar linac, also with many pairs of electrodes, but using rf focussing; (3) an RFQ-like configuration with continuous electrodes, in which energy changes slowly along the beam axis; and (4) a similar system in which the beam energy oscillates along the axis. We discuss some of the advantages and disadvantages of these systems, and analyze the last case in some detail. 8 refs., 1 fig.
Date: May 1, 1985
Creator: Cooper, W.S. & Anderson, O.A.
Partner: UNT Libraries Government Documents Department

National negative-ion-based neutral-beam development plan

Description: The plan covers facilities required, program milestones, and decision points. It includes identification of applications, experiments, theoretical research areas, development of specific technologies and reactor development and demonstration facilities required to bring about the successful application of negative-ion-based neutral beams. Particular emphasis is placed on those activities leading to use on existing plasma confinement experiments or their upgrades.
Date: August 1, 1983
Creator: Cooper, W.S. & Pyle, R.V. (eds.)
Partner: UNT Libraries Government Documents Department

A neutral-beam diagnostic for fast confined alpha particles in a burning plasma: Application on CIT (Compact Ignition Tokamak)

Description: Diagnostic methods for fast confined alpha particles are essential for a burning-plasma experiment. We review one- and two-electron-capture methods using energetic neutral beams, and provide quantitative estimates of signal level for a two-electron-capture method applicable to CIT. The best probe is a ground-state helium-atom beam because of its relatively good penetration into a CIT plasma and the large cross section for two-electron capture; it can be produced in useful quantities from HeH/sup +/. We calculate a signal level of the order of 10/sup 7/ counts/s for 100 mA of accelerated HeH/sup +/, which is sufficient to allow time-resolved measurements of the alpha-particle velocity distribution. Limited position information could be obtained for appropriate access port geometry. This diagnostic is feasible, and we recommend further research and development leading to implementation on CIT. 39 refs., 16 figs., 5 tabs.
Date: October 1, 1987
Creator: Schlachter, A.S.; Stearns, J.W. & Cooper, W.S.
Partner: UNT Libraries Government Documents Department


Description: The U.S. magnetic fusion energy program has developed a single design long pulse neutral beam source for TFTR, MFTF-B, and DIII-D. The arc is a very compact axial magnetic line cusp. The accelerator is an actively cooled tetrode with water cooled grid tubes of shaped molybdenum forming 'slot' beamlets. DIII-D and MFTF-B configurations have an 80 kV accelerator gap, with 12 x 48 cm aperture, and a 10 meter 'module' focus. TFTR modules are unfocused, with a 120 kV gap and 12 x 43 cm mask. The first CLPS was tested in the TFTR configuration, at 120 kV, 2 seconds. Optimum current was 73 Amperes, or 1.76 ppervs (deuterium), with 80% - 85% atomic fraction. Optimum divergence of ions plus neutrals was 0.4' parallel to the slots, and 0.7' perpendicular to the slots ( l / e half angle). The combination of an axial cusp magnetic bucket and slot accelerator apertures gives the CLPS about twice the beam power per unit cross section of other long pulse sources, plus lower divergence in the direction parallel to the slots.
Date: December 1, 1987
Creator: Vella, M. C.; Cooper, W. S. & Pincosy, P. A.
Partner: UNT Libraries Government Documents Department

Calorimetric and optical beam diagnostics on the LBL 120-keV neutral beam test facility

Description: The 120-keV Neutral Beam Test Facility at LBL is fitted with several types of instrumentation to determine the properties of the 10- to 15-A hydrogen and deuterium beams produced in this facility. These include a neutral particle dump for measuring the temperature profile generated by the beam, and a fixed and a moveable ion dump to measure the temperature profiles generated by the various ion components after they have been swept out of the neutral beam by a bending magnet. These several dumps provide enough information to determine the power density profiles and divergences of the neutral beam and the various ion beams for comparison with theoretical calculations, the beam composition, and the neutralization efficiency. The optical beam diagnostic consists of a high-resolution spectrometer coupled with a commercial optical multichannel analyzer. These instruments analyze Doppler-shifted optical radiation from the moving neutral atoms in the beam. Analysis of data so obtained provides the aiming directions and divergences of the various energy components in the neutral beam, as well as the beam composition.
Date: October 1, 1977
Creator: Burrell, C.F.; Cooper, W.S.; Steele, W.F. & Smith, R.R.
Partner: UNT Libraries Government Documents Department

Performance of a developmental 120-keV, 10-A deuterium (14-A hydrogen) neutral beam system

Description: We have recently operated the LBL 120-keV neutral beam test facility on deuterium. This facility consists of a large (170,000 l) vacuum system, a plasma source, a multiple-aperture electrostatic accelerator structure, an ion sweep magnet, ion and neutral beam dumps, and a computer diagnostic and control system. The total length of the beamline is about 8.5m. Operation of this test facility on deuterium has produced beams with an energy of 120 keV, a total (ion plus neutral) beam current of 10 A, and a pulse length of 0.5 sec. The beam profile at the location of the dump is bi-gaussian, with 1/e halfwidths of about 1.28 and 0.42 degrees. Deuterium operation has been very limited because of the high neutron production rate (about 10/sup 11/ sec/sup -1/ when the beam is on) and the lack of radiation shielding around the facility.
Date: October 1, 1977
Creator: Berkner, K.H.; Cooper, W.S.; Ehlers, K.W. & Pyle, R.V.
Partner: UNT Libraries Government Documents Department

Neutron production in a high-intensity deuterium neutral beam facility

Description: Measurement of d-d neutron yields incidentally produced in multi-megawatt neutral deuterium beam injectors used in magnetic fusion experiments is discussed. Unavoidable neutron production in the neutralizer, ion-beam dump, neutral beam calorimeter and beam collimator sections of an injector is measured to provide data for the design of radiation shielding and beam diagnostic experiments. At 120 kV, 10A, 0.5s pulsed injector operation, neutron yields plateau at an instantaneous yield from the calorimeter of 10/sup 11/ n/s. Beam diagnostic applications of neutron measurements are adjustment of beam source conditions to maximize the full-energy fraction of the neutral beam on target, and measurement of density in the neutralizer. (RME)
Date: June 1, 1977
Creator: Berkner, K.H.; Cooper, W.S.; McCaslin, J.B. & Pyle, R.V.
Partner: UNT Libraries Government Documents Department

Negative ion beam acceleration and transport experiments

Description: The design of a negative ion beam transport system is discussed. The ion source and accelerator have produced a 1-A, 8 keV beam of H ions with a pulse length of 30 seconds. The beam was additionally characterized as to electron content, uniformity along the slot, emittance perpendicular to the slot, and the beam divergence. 8 refs., 5 figs. (WRF)
Date: November 1, 1985
Creator: Cooper, W.S.; Anderson, O.A.; Kwan, J. & Steele, W.F.
Partner: UNT Libraries Government Documents Department

Efficient, radiation-hardened, 800-keV neutral beam injection system

Description: Recent advances and new concepts in negative ion generation, transport, acceleration, and neutrailzation make it appear likely that an efficient, radiation-hardened neutral beam injection system could be developed in time for the proposed FED-A tokamak. These new developments include the operation of steady-state H/sup -/ ion sources at over 5 A per meter of source length, the concept of using strong-focussing electrostatic structures for low-gradient dc acceleration of high-current sheet beams of negative ions and the transport of these beams around corners, and the development of powerful oxygen-iodine chemical lasers which will make possible the efficient conversion of the negative ions to neutrals using a photodetachment scheme in which the ion beam passes through the laser cavity.
Date: October 1, 1982
Creator: Anderson, O.A.; Cooper, W.S.; Goldberg, D.A.; Ruby, L.; Soroka, L. & Fink, J.H.
Partner: UNT Libraries Government Documents Department

Conceptual design of a neutral-beam injection system for the TFTR

Description: The neutral-beam injection requirements for heating and fueling the next generation of fusion reactor experiments far exceed those of present devices; the neutral-beam systems needed to meet these requirements will be large and complex. A conceptual design of a TFTR tokamak injection system to produce 120 keV deuterium-ion beams with a total power of about 80 MW is given. (auth)
Date: November 1, 1975
Creator: Ehlers, K.W.; Berkner, K.H.; Cooper, W.S.; Hooper, E.B.; Pyle, R.V. & Stearns, J.W.
Partner: UNT Libraries Government Documents Department

Efficient, radiation-hardened, 400- and 800-keV neutral-beam injection systems

Description: We present designs for two negative-ion based neutral beam lines with reactor-level power output. Both beam lines make use of such technologically advanced features as high-current-density surface-conversion ion sources, transverse-field-focussing (TFF) acceleration and transport, and laser photodetachment. For the second of these designs, we also presented detailed beam and vacuum calculations, as well as a brief description of a proof-of-principle test system currently under development.
Date: April 1, 1983
Creator: Anderson, O.A.; Cooper, W.S.; Fink, J.A.; Goldberg, D.A.; Ruby, L.; Soroka, L. et al.
Partner: UNT Libraries Government Documents Department

Mechanical design and construction of a 200 mA, 100 keV, dc, negative ion accelerator

Description: A volume production source and a 100 keV, dc, accelerator together with an additional, modular, 100 keV, electro static focused accelerator provide a starting point for a high energy H/sup -//D/sup -/ beam-line (200 keV to 800 keV), intended for fusion energy applications. The 100 keV accelerator tests started in June 1987. The mechanical design and construction of the accelerator is described. 3 refs., 8 figs.
Date: October 1, 1987
Creator: Purgalis, P.; Anderson, O.A.; Cooper, W.S.; Cummings, C.; Koehler, G.W.; Matuk, C.A. et al.
Partner: UNT Libraries Government Documents Department

Tranverse-field focussing beam transport experiment

Description: The Transverse-Field Focussing (TFF) beam transport and accelerator system developed at LBL is useful for negative-ion -based neutral beam injection due to its unique differential pumping and neutron shielding properties. We have tested the first module of our TFF system transporting H/sup -/ beams up to 80 keV beam energy. The testing addressed the most crucial physics and engineering issues involved in the principles of a TFF system including beam compression and differential gas pumping. At optimum perveance, the present design will transport 4 A/m of H/sup -/ beam at 80 keV beam energy.
Date: October 1, 1986
Creator: Kwan, J.W.; Ackerman, G.D.; Anderson, O.A.; Chan, C.F.; Cooper, W.S.; Soroka, L. et al.
Partner: UNT Libraries Government Documents Department

Neutral-beam research and development at LBL, Berkeley

Description: The neutral-beam research and development effort at LLL has been concerned mainly with design, construction, and testing of ion sources needed in present and planned experiments, chiefly at LLL. Development of techniques for producing reactor-type neutral beam systems with higher voltage, current, and duty cycle proceeds as resources permit. An important part of this program is the attempt to increase the physics understanding and technology needed for the design of beams with precisely controlled trajectories, e.g., converging beams. (auth)
Date: November 1, 1973
Creator: Baker, W.R.; Berkner, K.H.; Cooper, W.S.; Ehlers, K.W.; Kunkel, W.B.; Pyle, R.V. et al.
Partner: UNT Libraries Government Documents Department

Compact 80-keV neutral-beam module

Description: A compact and maintainable source of 80-keV neutral beams that focus to a high power density is required for the Mirror Fusion Test Facility (MFTF). In the new source being designed and built to meet these requirements, the cross-sectional area is reduced in two ways: by immersing the source in a vacuum where high voltage can be held over smaller distances and by redesigning grid supporting structures. Reliability is increased by reducing the electric fields everywhere else below those present between grids and by design innovations. The latter include techniques to reduce stray magnetic field and disperse gas uniformly, all metal-ceramic construction, and a 60-kV shield enclosing all 80-kV electrodes. Wherever possible, we have attempted to simplify the construction. We expect to solve problems that arise during testing either with add-on fixes or with the techniques already tested successfully on the Lawrence Berkeley Laboratory (LBL) 120-keV source. Easy maintenance is obtained by a compact isolation valve and by modular construction. Curving both the grid wires and their holders provides focusing in two planes.
Date: September 29, 1977
Creator: Molvik, A.W.; Baird, E.D.; Berkner, K.H.; Cooper, W.S.; Duffy, T.J.; Ehlers, K.W. et al.
Partner: UNT Libraries Government Documents Department

Long-pulse neutral injector development at the Lawrence Berkeley Laboratory

Description: The program elements for the development of long-pulse deuterium accelerators for neutral-beam injection into fusion plasmas are described. Operational characteristics of a 4-grid, 80-kV, 40-A accelerator, designed for 30-sec operation but limited to 800 msec operation by the test facility, are presented. These pulses are long enough to establish thermal equilibrium of the accelerator grids. Beam divergences of 1.0/sup 0/ x 0.4/sup 0/ have been achieved at 80 kV, 36 A for deuterium; 0.44/sup 0/ x 1.0/sup 0/ at 80 kV, 47 A for hydrogen. Measured heat loads on each grid are of the order of 0.5% of the beam power.
Date: January 1, 1982
Creator: Berkner, K.H.; Cooper, W.S.; Ehlers, K.W.; Jacobson, V.L.; Owren, H.M.; Paterson, J.A. et al.
Partner: UNT Libraries Government Documents Department

Design and fabrication of a surface conversion negative ion source and an 80 keV pre-accelerator

Description: The design and fabrication of a surface conversion negative ion source and an 80 keV pre-accelerator intended for use as a proof-of-principle demonstration leading to a radiation-hardened 400 keV TFF based beamline for the next generation mirror or tokamak reactor will be described in this paper. Experience gained in a previous source and accelerator module was utilized to redefine the overall design and construction for this second generation CW device. The source will provide 1 to 2 amps of H/sup -/ for acceleration by a 3 electrode 80 keV preaccelerator. Particular attention was placed on the mounting of the source to the primary high-voltage insulator, the insulator itself, magnet installation, converter shape and construction, cesium injector and exit aperture design, and accelerator construction, with an overall emphasis on serviceability.
Date: December 1, 1983
Creator: Matuk, C.A.; Anderson, O.A.; Biagi, L.A.; Berkner, K.H.; Cooper, W.S.; Ehlers, K.W. et al.
Partner: UNT Libraries Government Documents Department

Negative-ion-based neutral beams for fusion

Description: To maximize the usefulness of an engineering test reactor (e.g., ITER, TIBER), it is highly desirable that it operate under steady-state conditions. The most attractive option for maintaining the circulating current needed in the center of the plasma is the injection of powerful beams of neutral deuterium atoms. The beam simultaneously heats the plasma. At the energies required, in excess of 500 keV, such beams can be made by accelerating D/sup -/ ions and then removing the electron. Sources are being developed that generate the D/sup -/ ions in the volume of a specially constructed plasma discharge, without the addition of cesium. These sources must operate with minimum gas flow, to avoid stripping the D/sup -/ beam, and with minimum electron output. We are designing at LBL highly efficient electrostatic accelerators that combine electric strong-focusing with dc acceleration and offer the possibility of varying the beam energy at constant current while minimizing breakdown. Some form of rf acceleration may also be required. To minimize irradiation of the ion sources and accelerators, the D/sup -/ beam can be transported through a maze in the neutron shielding. The D/sup -/ ions can be converted to neutrals in a gas or plasma target, but advances in laser and mirror technology may make possible very efficient photodetachment systems by the time an ETR becomes operational. 9 refs., 4 figs.
Date: October 1, 1987
Creator: Cooper, W.S.; Anderson, O.A.; Chan, C.F.; Jackson, L.T.; Kunkel, W.B.; Kwan, J.W. et al.
Partner: UNT Libraries Government Documents Department