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Advanced neutral-beam technology

Description: Extensive development will be required to achieve the 50- to 75-MW, 175- to 200-keV, 5- to 10-sec pulses of deuterium atoms envisioned for ETF and INTOR. Multi-megawatt injector systems are large (and expansive); they consist of large vacuum tanks with many square meters of cryogenic pumping panels, beam dumps capable of dissipating several megawatts of un-neutralized beam, bending magnets, electrical power systems capable of fast turnoff with low (capacity) stored energy, and, of course, the injector modules (ion sources and accelerators). The technology requirements associated with these components are described.
Date: September 1, 1980
Creator: Berkner, K.H.
Partner: UNT Libraries Government Documents Department

1-2 GeV synchrotron radiation facility at Lawrence Berkeley Laboratory

Description: The Advanced Light Source (ALS), a dedicated synchrotron radiation facility optimized to generate soft x-ray and vacuum ultraviole (XUV) light using magnetic insertion devices, was proposed by the Lawrence Berkeley Laboratory in 1982. It consists of a 1.3-GeV injection system, an electron storage ring optimized at 1.3 GeV (with the capability of 1.9-GeV operation), and a number of photon beamlines emanating from twelve 6-meter-long straight sections, as shown in Fig. 1. In addition, 24 bending-magnet ports will be avialable for development. The ALS was conceived as a research tool whose range and power would stimulate fundamentally new research in fields from biology to materials science (1-4). The conceptual design and associated cost estimate for the ALS have been completed and reviewed by the US Department of Energy (DOE), but preliminary design activities have not yet begun. The focus in this paper is on the history of the ALS as an example of how a technical construction project was conceived, designed, proposed, and validated within the framwork of a national laboratory funded largely by the DOE.
Date: October 1, 1985
Creator: Berkner, K.H.
Partner: UNT Libraries Government Documents Department

Sputtering-erosion estimates for NBETF beam dumps

Description: To stop multi-second high-energy hydrogen or deuterium beams in neutral injection systems, thin-skin actively cooled dumps made of Cu, Mo, or W are contemplated. For the Neutral Beam Engineering Test Facility (NBETF), the design goal for the life of the beam dumps is 25,000 thirty-second pulses, with a fluence of 10/sup 23/ deuterons/cm/sup 2/. From a review of the literature on sputtering and blistering, we estimate that an erosion allowance of 0.13 cm for Cu, 0.02 cm for Mo, and 0.004 cm for W has to be incorporated in the beam-dump design.
Date: October 1, 1981
Creator: Wekhof, A. & Berkner, K.H.
Partner: UNT Libraries Government Documents Department

Beam-induced pressure variations in a TFTR neutral-beam injector

Description: In neutral-beam injection systems either all or part of the gas flow into the neutralizer comes from the plasma source. When the beam is switched on, ions from the plasma source, which used to contribute to the gas flow, are converted to an energetic beam and are pumped away: hence reducing the gas input to the neutralizer. The large volume of the neutralizer and its high conductance damp out rapid changes; for example, when the gas to the source is first turned on, there is a 230 msec exponential rise time associated with pressure in the neutralizer. The neutralizer in turn acts as a source of gas to the first chamber and the first chamber to the second and so on. Beam dumps become additional sources of gas in the second chamber and target tank as gas molecules are collisionally desorbed from the surface of the dump. A simple analytical model (the equivalent of an electrical RC circuit) of the volumes and conductances of the system has been used to describe the pressure variations. The use of time dependent sources terms in the model gives an estimate of the desorption rate from the dumps and its time variation during a beam pulse.
Date: October 1, 1981
Creator: Willis, J.E. & Berkner, K.H.
Partner: UNT Libraries Government Documents Department

Neutral beam injector research and development work in the USA

Description: This brief review covers the US neutral-beam-injector research and development work carried out at DOE Laboratories: The Brookhaven National Laboratory (BNL), The Lawrence Berkeley and Livermore Laboratories (LBL/LLL), and The Oak Ridge National Laboratory (ORNL).
Date: January 1, 1978
Creator: Pyle, R.V.; Baker, W.R. & Berkner, K.H.
Partner: UNT Libraries Government Documents Department

Collision of fast highly charged ions in gas targets: ionization, recoil-ion production, and charge transfer

Description: Electron-capture, ionization, and recoil-ion-production cross sections are measured and calculated for fast highly charged projectiles in hydrogen and rare-gas targets. Recoil-ion-production cross sections are found to be large; the low energy and high charge states of the recoil ions make them useful for subsequent collision studies.
Date: July 1, 1982
Creator: Schalchter, A.S.; Berkner, K.H. & Beyer, H.F.
Partner: UNT Libraries Government Documents Department

Neutral-beam design options. [Design and cost optimization]

Description: The designs and costs of magnetic-confinement experimental devices and reactors can be affected strongly by the choice of parameters for the neutral-beam injection system. To provide the designer with information with which to estimate the physical and cost consequences of variations in energy, neutralizer thickness, ion-species mixtures, etc., we are carrying out parametric studies of the neutralization efficiency. Some of the results are reported here. The data base is too small and uncertain to permit calculations which would optimize all aspects of designs at this time.
Date: April 1, 1976
Creator: Stearns, J. W.; Berkner, K. H. & Pyle, R. V.
Partner: UNT Libraries Government Documents Department

STATUS OF THE LBL/LLL DEVELOPMENT PROGRAM

Description: The status and near-term goals of the LBL/LLL neutral-beam-development program are described. The emphasis in this paper is on the technology of systems based on the acceleration and neutralization of positive ions; this approach will be used in the near term, probably through 1985 at least. For more efficient injection, part of our plan is to develop a negative-ion approach suitable for 200- to 400-kV injectors on confinement experiments in the 1985-90 period. However, the negative-ion based program is still very much in the research phase, and it is difficult to project how it will phase into fusion reactor fueling experiments.
Date: November 1, 1977
Creator: Berkner, K.H.; Berkner, K.H.; Ehlers, K.W.; Pyle, R.V. & Hooper Jr., E.B.
Partner: UNT Libraries Government Documents Department

Effect of capacitive stored energy on neutral-beam-accelerator performance

Description: The results of tests to determine the effects of capacitive stored energy (1/2 CV/sup 2/) on the performance of neutral-beam injectors are reported. Typical fault-current waveforms and methods to limit fault current are presented. Tests indicate that deterioration of performance is not only a function of peak stored energy but is also dependent on peak current and the characteristics of the breakdown.
Date: September 1, 1982
Creator: Owren, H.M.; Baker, W.R.; Berkner, K.H.; Hopkins, D.B. & Massoletti, D.J.
Partner: UNT Libraries Government Documents Department

Plasma neutralizers for H/sup -/ or D/sup -/ beams

Description: Plasma neutralizers can produce higher conversion efficiencies than are obtainable with gas neutralizers for the production of high-energy neutral beams from negative hydrogen ions. Little attention has been paid to experimental neutralizer studies because of the more critical problems connected with the development of negative-ion sources. With the prospect of accelerating ampere dc beams from extrapolatable ion sources some time next year, we are re-examining plasma neutralizers. Some basic considerations, two introductory experiments, and a next-step experiment are described.
Date: October 1, 1980
Creator: Berkner, K.H.; Pyle, R.V.; Savas, S.E. & Stalder, K.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

Design and fabrication of a large rectangular magnetic cusp plasma source for high intensity neutral beam injectors

Description: The design and fabrication techniques for a large, rectangular magnetic bucket plasma source are described. This source is compatible with the accelerator structures for the TFTR and DIII neutral-beam systems.
Date: November 1, 1979
Creator: Biagi, L.A.; Berkner, K.H.; Ehlers, K.W.; Paterson, J.A. & Porter, J.R.
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

Neutron production by neutral beam sources

Description: Neutron yields, from interactions of multiampere 40- to 120-keV deuterium beams with deuterium atoms implanted in copper targets, have been measured in order to provide input data for shielding of neutral-deuterium beam facilities for magnetic fusion experiments.
Date: November 1, 1979
Creator: Berkner, K.H.; Massoletti, D.J.; McCaslin, J.B.; Pyle, R.V. & Ruby, L.
Partner: UNT Libraries Government Documents Department

Negative-hydrogen-ion production by backscattering from alkali-metal targets

Description: Measurements have been made of the total backscattered D/sup -/ and H/sup -/ yields from Cs, Rb, K, Na and Li surfaces bombarded with D/sub 2//sup +/, D/sub 3//sup +/, H/sub 2//sup +/ and H/sub 3//sup +/ in the energy range 0.15 to 4 keV/nucleus. All measurements were made at a background pressure less than 10/sup -9/ Torr and the alkali-metal surfaces were evaporated onto a substrate in situ to minimize contamination of surfaces. For each target, the D/sup -/ and H/sup -/ yields exhibited maxima (as high as 8% per incident deuteron or proton for Cs); the maxima occurred at incident energies between 300 and 1000 eV/nucleus and always occurred at a lower incident energy for H than for D for a given target. Both the H/sup -/ and D/sup -/ yields decreased, at any measured energy, in going from Cs to Li in the order given above. Measurements of the H/sup -/ yield were also made for H/sub 3//sup +/ bombarding a W substrate, as a function of the work function of the target, as Li was deposited on the W. The work function of the target showed a minimum as the Li coverage was increased and the H/sup -/ yield showed a corresponding maximum which was almost two orders of magnitude higher than the H/sup -/ yield for a thick Li target.
Date: November 1, 1979
Creator: Schneider, P.J.; Berkner, K.H.; Graham, W.G.; Pyle, R.V. & Stearns, J.W.
Partner: UNT Libraries Government Documents Department

Steady state gas efficiency of ion sources for neutral beams

Description: Gas present in the acceleration grids of a neutral beam line is one cause of divergent beam power. A measure of this problem is the gas efficiency (nuclear) of the ion source, epsilon/sub g/ = I/sub b//I/sub g/, where I/sub b/ denotes the extracted current of beam nuclei, and I/sub g/ the total current of nuclei to the source as gas. For a short pulse beam, less than or equal to 0.1 sec, gas transients make epsilon/sub g/ difficult to observe. Using the fraction size Berkeley LPA (nominally 120 keV, 10A), the gas efficiency of a positive ion, hydrogen neutral beam has been studied with pulses from 0.5 to 28 sec at 80 keV, 5.7 A, and 0.5 sec at 120 keV, 10A. The observed gas efficiency, 20% to 40%, is shown to agree with a simple steady state model. The model indicates that gas efficiency is determined by the degree of arc ionization.
Date: September 1, 1981
Creator: Vella, M.C.; Berkner, K.H.; Massoletti, D.J.; Owren, H.M. & Willis, J.E.
Partner: UNT Libraries Government Documents Department

Photoelectric work function measurement of a cesiated metal surface and its correlation with the surface-produced H/sup -/ ion flux

Description: For application in plasma heating, fueling, and current drive of magnetic fusion devices, high current negative deuterium ion sources for intense neutral beam injectors are being developed using efficient production of negative hydrogen isotope ions on low work function metal surfaces imbedded in hydrogen plasmas. In order to investigate the correlation between work function and negative hydrogen ion production, photoelectron emission from a cesiated metal surface, which is immersed in a hydrogen plasma with an electron density less than 5 x 10/sup 10//cc, was measured in the photon energy range of 1.3 to 4.1 eV. The work function determination was based on Fowler's analysis, and at the optimum coverage a work function of less than 1.5 eV was observed for a Cs-Cu surface. Measured values of work functions for different Cs coverages were compared to the negative hydrogen currents produced at the metal surface in the discharge; the surface production of negative hydrogen ion current is monotonically increasing with decreasing work function.
Date: September 1, 1982
Creator: Wada, M.; Berkner, K.H.; Pyle, R.V. & Stearns, J.W.
Partner: UNT Libraries Government Documents Department

D- production by backscattering from clean alkali-metal surfaces

Description: Measurements have been made of the total back-scattered D/sup -/ yields from Cs, Rb, K, Na and Li surfaces bombarded with D/sub 2//sup +/ and D/sub 3//sup +/ in the energy range 0.05 to 3.5 keV/nucleon. All measurements were made at a background pressure less than 10/sup -9/ Torr and the alkali-metal surfaces were evaporated onto a substrate in situ to assure uncontaminated surfaces. For each target, the D/sup -/ yield is at a maximum (as high as 12% per incident deuteron for Cs) between 150 and 300 eV/nucleon, and at any measured energy, the D/sup -/ yield decreases from Cs to Li in the order given above.
Date: September 1, 1977
Creator: Schneider, P. J.; Berkner, K. H.; Graham, W. G.; Pyle, K. V. & Stearns, J. W.
Partner: UNT Libraries Government Documents Department

Cryopump, neutral-beam compatibility test

Description: The design and performance testing plan for a cryopump to be used on the TFTR neutral beams injectors are briefly discussed. The cryopump consists of an outer envelope at liquid nitrogen temperature, and an inner envelope at liquid helium temperature. In the cryopanel-chevron structure to be tested, a deuterium condensation rate of 2.5 x 10/sup 4/ liters/s is predicted. A three phase test plan for performance testing at both LBL and LLL is delineated. (RME)
Date: January 1, 1977
Creator: Berkner, K.H.; Law, P.K.; Pyle, R.V.; Ruby, L.; Pittenger, L.C. & Valby, L.E.
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

Design data for calculating neutral beam penetration into Z/sub eff/ > 1 plasmas

Description: Impurities such as C, N, O, Fe, and Mo in a confined plasma reduce the penetration of the energetic neutral deuterium or hydrogen beam injected for heating or fueling the plasma, thus affecting the energy- and fuel-deposition profiles. New calculations, confirmed by recent experimental results, show that previous estimates of the reduction of neutral beam penetration due to impurities in the plasma were overly pessimistic. Until recently, the cross sections used to calculate beam attenuation had been assumed to be q/sup 2/times the cross section for H/sup +/ + H obtained from the Born approximation, where q is the charge state of the ion. This led to very large cross sections for large values of q, and thus to very stringent requirements on the acceptable level of impurity ions in the plasma.
Date: January 1, 1978
Creator: Olson, R.E.; Berkner, K.H.; Graham, W.G.; Pyle, R.V.; Schlachter, A.S. & Stearns, J.W.
Partner: UNT Libraries Government Documents Department