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Indirectly heated cathodes and duoplasmatron type electron feeds for positive ion sources

Description: Development of indirectly heated cathodes and duoplasmatron type electron feed assemblies is being pursued for use on positive ion sources of neutral beam systems. The cathodes utilize La/sub 2/O/sub 3/ doped molybdenum emission surfaces which supply ionizing electrons for a large rectangular (28 cm. x 60 cm.) magnetic multi-cusp confinement chamber. Single and double electron feed assemblies with different electrode geometries were tested at discharge currents of greater than or equal to 1000 A and pulse lengths of approx. 35 sec. Details of construction and performance results such as plasma uniformity are discussed.
Date: October 19, 1981
Creator: Schechter, D.E. & Tsai, C.C.
Partner: UNT Libraries Government Documents Department

Performance of a modified DuoPIGatron ion source for PLT neutral beam injectors

Description: The performance of a modified duoPIGatron ion source for PLT neutral beam injectors is described. The 22-cm source has been operated to deliver beams of 70 A, up to 45 keV, and 0.5 sec. Following a brief review of source operation, the dominant reactions leading to an enhanced atomic ion fraction in the source plasma are emphasized. In addition to the high atomic ion species yield (about 85%), other important characteristics of the source such as high arc efficiency (about 1.1 A ion beam current per kW of arc power), long filament lifetime, high reliability, and scalability are also described.
Date: September 1, 1978
Creator: Tsai, C.C.; Stirling, W.L. & Haselton, H.H.
Partner: UNT Libraries Government Documents Department

15 cm duoPIGatron ion source

Description: The 10-cm (grid diameter) duoPIGatron ion source produces pulsed hydrogen ion beams of 10 to 15 A beam current in the 20- to 40-keV energy range for a duration of a few tenths of a second. To fulfill the requirements of the next generation of high-power neutral beam injectors for heating plasmas in CTR devices, this source has been enlarged to a version 15-cm in grid diameter. In addition, by utilizing a magnetic multipole line cusp field confinement method, the plasma created is characterized over the 15 cm grid diameter by a noise level within +- 10 percent and spatial density variations within +- 15 percent at a density on the order of 10/sup 12/ cm/sup -3/. This larger source has operated reliably and produced a beam current exceeding 30 A of hydrogen at 27 keV. Initial operation of a 20-cm version of this source employing line cusp confinement has produced an extraction current of 60 A at 33 keV.
Date: October 1, 1976
Creator: Stirling, W. L.; Tsai, C. C. & Ryan, P. M.
Partner: UNT Libraries Government Documents Department

Plasma studies on a duoPIGatron ion source

Description: In an effort to develop a plasma source capable of producing a dense, quiescent, uniform plasma for extracting tens of amperes of hydrogen ions, experimental and theoretical studies on a duoPIGatron ion source have been pursued. A study of plasma generation in the duoPIGatron was begun and a discharge model was subsequently developed to explain observed source behavior. The discharge model is based on two plasmas, a cathode plasma and a PIG plasma separated by a double layer of ions and electrons, and is similar to the existing model for a duoplasmatron. This discharge model is reviewed and the importance of the double layer on plasma generation in the duoPIGatron is discussed. Source electrode modifications suggested by the model resulted in a low noise level of about +- 5% and a low-density nonuniformity of about +- 10% over a 10-cm diameter at a high hydrogen plasma density of roughly 2 x 10/sup 12/ cm/sup -3/.
Date: January 1, 1977
Creator: Tsai, C. C.; Ryan, P. M. & Stirling, W. L.
Partner: UNT Libraries Government Documents Department

Hollow cathode for positive ion sources

Description: Development to incorporate hollow cathodes into high power ion sources for neutral beam injection systems is being pursued. Hollow tube LaB/sub 6/-type cathodes, similar to a UCLA design, have been constructed and tested in several ORNL ion source configurations. Results of testing include arc discharge parameters of >1000 and 500 amps for 0.5 and 10 second pulse lengths, respectively. Details of cathode construction and additional performance results are discussed.
Date: January 1, 1979
Creator: Schechter, D.E.; Kim, J. & Tsai, C.C.
Partner: UNT Libraries Government Documents Department

Characteristics and potential applications of an ORNL microwave ECR multicusp plasma ion source

Description: A new microwave electron cyclotron resonance (ECR) multicusp plasma ion source that has two ECR plasma production regions and uses multicusp plasma confinement has been developed at Oak Ridge National Laboratory. This source has been operated to produce uniform and dense plasma over large areas of 300 to 400 cm{sup 2} and could be scaled up to produce uniform plasma over 700 cm{sup 2} or larger. The plasma source has been operated with continuous argon gas feed and pulsed microwave power. The working gases used were argon, helium, hydrogen, and oxygen. The discharge initiation phenomena and plasma properties have been investigated and studied as functions of the discharge parameters. The discharge characteristics and a hypothetical discharge mechanism for this plasma source are described and discussed. Potential applications, including plasma and ion-beam sources for manufacturing advanced microelectronics, for space electric propulsion, and for fusion research, are discussed. 10 refs., 10 figs.
Date: January 1, 1990
Creator: Tsai, C.C.
Partner: UNT Libraries Government Documents Department

Potential applications of a new microwave ECR (electron cyclotron resonance) multicusp plasma ion source

Description: A new microwave electron cyclotron resonance (ECR) multicusp plasma ion source using two ECR plasma production regions and multicusp plasma confinement has been developed at Oak Ridge National Laboratory. This source has been operated to produce uniform and dense plasmas over large areas of 300 to 400 cm{sup 2}. The plasma source has been operated with continuous argon gas feed and pulsed microwave power. The discharge initiation phenomena and plasma properties have been investigated and studied as functions of discharge parameters. Together with the discharge characteristics observed, a hypothetical discharge mechanism for this plasma source is reported and discussed. Potential applications, including plasma and ion-beam processing for manufacturing advanced microelectronics and for space electric propulsion, are discussed. 7 refs., 6 figs.
Date: January 1, 1990
Creator: Tsai, C.C.
Partner: UNT Libraries Government Documents Department

Direct cryosorption pumping of an energetic hydrogen ion beam

Description: Cryosorption pumps (CSP) are a prime candidate for the pumping of helium and deuterium-tritium (D-T) in tokamak divertor systems and may also see service in neutral beam injectors. However, the ability of a CSP to take high energy ions escaping from a plasma or neutral beam has not previously been demonstrated. In this study we arranged a 10-cm ion source of the type used in the Oak Ridge Tokamak (ORMAK) to inject a beam of ions directly into the inlet of a CSP. The pump contained two chevron baffles at 100K and 15K as well as a 15K cryosorption surface covered with a type 5A molecular sieve. The cryosurfaces were cooled by a closed-cycle helium refrigerator. For hydrogen ion pulses up to 11.5-keV energy and 1.3-A current, the pressure maintained during the pulse was only a few percent higher than that maintained with an equal flow of cold neutral gas. Pulse lengths of 100-300 ms were used. Calorimetric measurements showed that 40-60% of the I-V power was incident on the pump inlet. Cool-down and regeneration behavior of the pump will also be discussed.
Date: January 1, 1979
Creator: Schwenterly, S.W.; Ryan, P.M. & Tsai, C.C.
Partner: UNT Libraries Government Documents Department

Development of a long-pulse (30-s), high-energy (120-keV) ion source for neutral-beam applications

Description: Multimegawatt neutral beams of hydrogen or deuterium atoms are needed for fusion machine applications such as MFTB-B, TFTR-U, DIII-U, and FED (INTOR or ETR). For these applications, a duoPIGatron ion source is being developed to produce high-brightness deuterium beams at a beam energy of approx. 120 keV for pulse lengths up to 30 s. A long-pulse plasma generator with active water cooling has been operated at an arc level of 1200 A with 30-s pulse durations. The plasma density and uniformity are sufficient for supplying a 60-A beam of hydrogen ions to a 13- by 43-cm accelerator. A 10- by 25-cm tetrode accelerator has been operated to form 120-keV hydrogen ion beams. Using the two-dimensional (2-D) ion extraction code developed at Oak Ridge National Laboratory (ORNL), a 13- by 43-cm tetrode accelerator has been designed and is being fabricated. The aperture shapes of accelerator grids are optimized for 120-keV beam energy.
Date: January 1, 1983
Creator: Tsai, C.C.; Barber, G.C. & Blue, C.W.
Partner: UNT Libraries Government Documents Department

Methods for independent plasma production and beam injection for H/sup +/. -->. H/sup -/ surface conversion

Description: Based on the Oak Ridge National Laboratory (ORNL) source development program, ways to create a uniform and dense plasma are briefly reviewed. The positive ions so created will be accelerated towards a surface convertor for producing negative ions. The convertor will be used for reducing the electrons in the extraction region. The significant results and features of this study are presented.
Date: January 1, 1977
Creator: Tsai, C C; Stirling, W L & Davis, R C
Partner: UNT Libraries Government Documents Department

Energetic neutral beam cleaning. Final CRADA report for CRADA number Y-1296-0427

Description: The purpose of this project is to evaluate the feasibility of cleaning silicon wafers with an energetic (1 to 100 eV) neutral particle beam and to develop a viable neutral beam source. A microwave plasma source on an existing test stand was modified to produce a 2-cm diameter neutral beam for cleaning the wafers. Significant results regarding neutral beam wafer cleaning are reported.
Date: December 31, 1996
Creator: Schechter, D.E.; Tsai, C.C. & Boitnott, C.
Partner: UNT Libraries Government Documents Department

RELAP5/MOD2 overview and developmental assessment results from TMI-1 plant transient analysis

Description: RELAP5/MOD2 is a new version of the RELAP5 thermal-hydraulic computer code containing improved modeling features that provide a generic capability for pressurized water reactor transient simulation. Objective of this paper is to provide code users with an overview of the code and to report developmental assessment results obtained from a Three Mile Island Unit One plant transient analysis. The assessment shows that the injection of highly subcooled water into a high-pressure primary coolant system does not cause unphysical results or pose a problem for RELAP5/MOD2.
Date: January 1, 1984
Creator: Lin, J.C.; Tsai, C.C.; Ransom, V.H. & Johnsen, G.W.
Partner: UNT Libraries Government Documents Department

Material and electromagnetic properties of Faraday shields for ion cyclotron heating antennas

Description: The Faraday shields for ion cyclotron antennas must transmit magnetic waves and adsorb little rf power. To investigate these properties, we have constructed 27 Faraday shields in many configurations, including chevrons, tubes, straps, concentric rings, various layered shields, conventionally leafed straps, and replicas of the Faraday shields for ASDEX, the Joint European Torus (JET), TEXTOR, and Alcator-C. We have measured the magnetic flux and observed loading at various operating resistances by using dielectric sheets or magnetic-coupled loads. Each Faraday shield effects a net change in the characteristic inductance of the antenna, resulting in a reduction of wave coupling. However, the load experienced by the antenna is not always reduced because the Faraday shield itself acts as a load. We differentiate between these effects experimentally. The net result of the study is that the Faraday shields now in use cost up to a factor of 50% of coupling. This, of course, reduces the power handling capability by 50% as well. However, configurations exist that are easily cooled and result in a reduction of less than 5% in loading.
Date: January 1, 1985
Creator: Hoffman, D.J.; Becraft, W.R.; Baity, F.W.; Caughman, J.B.O. & Tsai, C.C.
Partner: UNT Libraries Government Documents Department

Determination of species yield of ion sources used for intense neutral-beam injection

Description: For efficient plasma heating, ion sources of neutral-beam injectors should be capable of producing ion beams with an atomic fraction of 90% or higher. Diagnostic techniques for quantitatively determining source species yield have been developed and evaluated. These include magnetic momentum analysis of the unneutralized ions passing through the neutralizer, energy analysis of the neutral beam by electrostatic separation of ions emanating from a stripping cell, and quantity vs implantation-depth analysis of hydrogen implanted into a crystal by SIMS technique. The operational features and advantages and disadvantages of each technique will be discussed. If the effects of beamlet optics, energy straggling in the accelerator, and neutralizer gas scattering are taken into account, the results of the measurements using the three techniques are shown to be mutually consistent within experimental error.
Date: January 1, 1982
Creator: Tsai, C.C.; Barnett, C.F.; Haselton, H.H.; Langley, R.A. & Stirling, W.L.
Partner: UNT Libraries Government Documents Department

Potential applications of fusion neutral beam facilities for advanced material processing

Description: Surface processing techniques involving high energy ion implantation have achieved commercial success for semiconductors and biomaterials. However, wider use has been limited in good part by economic factors, some of which are related to the line-of-sight nature of the beam implantation process. Plasma source ion implantation is intended to remove some of the limitations imposed by directionality of beam systems and also to help provide economies of scale. The present paper will outline relevant technologies and areas of expertise that exist at Oak Ridge National Laboratory in relation to possible future needs in materials processing. Experience in generation of plasmas, control of ionization states, pulsed extraction, and sheath physics exists. Contributions to future technology can be made either for the immersion mode or for the extracted beam mode. Existing facilities include the High Power Test Facility, which could conservatively operate at 1 A of continuous current at 100 kV delivered to areas of about 1 m{sup 2}. Higher instantaneous voltages and currents are available with a reduced duty cycle. Another facility, the High Heat Flux Facility can supply a maximum of 60 kV and currents of up to 60 A for 2 s on a 10% duty cycle. Plasmas may be generated by use of microwaves, radio-frequency induction or other methods and plasma properties may be tailored to suit specific needs. In addition to ion implantation of large steel components, foreseeable applications include ion implantation of polymers, ion implantation of Ti alloys, Al alloys, or other reactive surfaces.
Date: January 1, 1994
Creator: Williams, J. M.; Tsai, C. C.; Stirling, W. L. & Whealton, J. H.
Partner: UNT Libraries Government Documents Department

Characteristics of an electron-beam rocket pellet accelerator

Description: An electron-beam rocket pellet accelerator has been designed, built, assembled, and tested as a proof-of-principle (POP) apparatus. The main goal of accelerators based on this concept is to use intense electron-beam heating and ablation of a hydrogen propellant stick to accelerate deuterium and/or tritium pellets to ultrahigh speeds (10 to 20 km/s) for plasma fueling of next-generation fusion devices such as the International Thermonuclear Engineering Reactor (ITER). The POP apparatus is described and initial results of pellet acceleration experiments are presented. Conceptual ultrahigh-speed pellet accelerators are discussed. 14 refs., 8 figs.
Date: January 1, 1989
Creator: Tsai, C.C.; Foster, C.A. & Schechter, D.E.
Partner: UNT Libraries Government Documents Department

Characteristics of an electron-beam rocket pellet accelerator

Description: A proof-of-principle (POP) electron-beam pellet accelerator has been developed and used for accelerating hydrogen and deuterium pellets. An intact hydrogen pellet was accelerated to a speed of 460 m/s by an electron beam of 13.5 keV. 0.3 A, and 2 ms. The maximum speed is limited by the acceleration path length (0.4 m) and pellet integrity. Experimental data have been collected for several hundred hydrogen pellets, which were accelerated by electron beams with parameters of voltage up to 16 kV, current up to 0.4 A, and pulse length up to 10 ms. Preliminary results reveal that the measured burn velocity increases roughly with the square of the beam voltage, as the theoretical model predicts. The final pellet velocity is proportional to the exhaust velocity, which increases with the beam power. To reach the high exhaust velocity needed for accelerating pellets to >1000 m/s, a new electron gun, with its cathode indirectly heated by a graphite heater and an electron beam, is being developed to increase beam current and power. A rocket casing or shell around the pellet has been designed and developed to increase pellet strength and improve the electron-rocket coupling efficiency. We present the characteristics of this pellet accelerator, including new improvements. 13 refs., 6 figs.
Date: January 1, 1991
Creator: Tsai, C.C.; Foster, C.A.; Milora, S.L. & Schechter, D.E.
Partner: UNT Libraries Government Documents Department

Alpha particle diagnostic beam line system to generate an intense Li/sup 0/ beam with an ORNL SITEX source

Description: The Oak Ridge National Laboratory (ORNL) SITEX (Surface Ionization with Transverse Extraction) negative ion source utilizes a 100-V/20-A reflex arc discharge in a 1300-gauss magnetic field to generate Cs+ ions and H+ or D+ ions, depending on the beam required. A shaped molybdenum plate is placed directly behind the arc column. Cesium coverage on this plate is used to minimize the surface work function, which requires two-thirds of a monolayer coverage. Cesium coverage ia adjusted both by cesium flow control into the arc discharge chamber and by temperature control of the converter using gaseous-helium cooling channels in the converter plate. Normal converter operational temperatures are 300/sup 0/ to 500/sup 0/C H/sup -//D/sup -/ beams are generated at the biased converter surface (-150 V with respect to the anode) by Cs/sup +/ sputtering of absorbed hydrogen or deuterium and by the reflection-conversion mechanism of H/sup +//D/sup +/ ions which strike the converter surface at 150 eV. The negative ions are accelerated through the 150-V plasma sheath at the converter surface and are focused by the converter geometry and magnetic field so as to pass through the exit aperture with minimum angular divergence. The ion optics of the SITEX accelerator has been calculated using the ORNL 3-D optics code and results in a divergence perpendicular to the slot of theta/sub perpendicular rms/ = 0.35/sup 0/ and parallel to the slot of theta/sub parallel rms/ = 0.18/sup 0/. This beam divergence should be adequate for injection into a radio frequency quadrupole (RFQ) for further acceleration.
Date: January 1, 1985
Creator: Dagenhart, W.K.; Stirling, W.L.; Tsai, C.C. & Whealton, J.H.
Partner: UNT Libraries Government Documents Department

Production of low energy positive ions suitable for double electron capture systems

Description: Single aperture beam extraction studies have been made of a new technique to produce low divergence beams of about 0.4/sup 0/ HWHM at about 15 keV to 40 keV. Computer calculations show that this technique of coating the plasma side of the plasma grid with about 0.01'' of Al/sub 2/O/sub 3/ can also be extended to the 0.5 keV to 5 keV range with beam optics less than 1/sup 0/. Source performance including results from multiaperture source operation will be discussed.
Date: January 1, 1977
Creator: Whealton, J H; Tsai, C C; Grisham, L R & Stirling, W L
Partner: UNT Libraries Government Documents Department

New ORNL neutral beam transport system

Description: The Princeton Large Torus (PLT) neutral beam injection systems have proven themselves to be a solid foundation on which next generation systems can be based. There are two areas in the new systems receiving particular emphasis: (a) increased power per beam line and (b) higher beam transmission efficiency. Two different methods are being investigated to improve the transmission efficiency. First the drift tube region, the region of the beam line between the vacuum chamber housing the ion source and the torus, is being enlarged. In this manner a second, large cryopump will be installed in the drift tube to lower the pressure to approx.10/sup -5/ torr. Thus, neutral beam reionization on the background gas will be significantly reduced from the measured losses at a few 10/sup -4/ torr of the PLT system. Second, the beam divergence will be reduced by application of one or more of three known techniques developed on a single aperture source in the laboratory. Each of these methods has shown a reduction in single beamlet divergence from theta/sub HWHM/ approx. 1/sup 0/ to approx.0.5/sup 0/. The low beamlet divergence coupled with a differentially pumped drift tube will effectively accommodate the larger ion sources under development. All future beam line systems will benefit either directly or indirectly from the experience gained operating and upgrading the PLT beam line concept.
Date: January 1, 1977
Creator: Stirling, W.L.; Davis, R.C.; Haselton, H.H.; Schnechter, D.E. & Tsai, C.C.
Partner: UNT Libraries Government Documents Department

DuoPIGatron ion sources for PLT injectors

Description: Plasma heating requirements for the Princeton Large Torus (PLT) are set at about 1 MJ total beam energy for 3 MW beam power of energetic hydrogen (or deuterium) neutrals at 40 keV. To fulfill this design goal from four neutral beam injectors, the duoPlGatron ion source originally developed at ORNL has been modified, developed, and scaled-up to versions with 20-cm and/or 22-cm grid diameters. Utilizing the multipole line cusp magnetic field confinement for the ionizing electrons and created Philips Ionization Gauge (PIG) plasma, these sources generate a uniform (+-5 percent density variation over 23-cm diam) and dense plasma (about 2 x 10/sup 12/ cm/sup 3/ at the extraction surface). Such sources have been operated reliably to deliver a beam current exceeding 70 A of hydrogen ions at 40 keV. For such a beam condition the source is capable of running with an arc pulse of 0.5 sec. Moreover, the corresponding arc efficiency is very high, below 1.0 KW arc power per ampere of ion beam current. In this paper we describe the plasma generation, source characteristics and arc efficiency as functions of magnetic fields, gas pressure, and arc power (including the arc voltage and current). The other exciting feature, high proton yield (exceeding 80 percent), will be discussed.
Date: January 1, 1977
Creator: Tsai, C. C.; Stirling, W. L.; Haselton, H. H.; Davis, R. C. & Schechter, D. E.
Partner: UNT Libraries Government Documents Department

Erosion tests of materials by energetic particle beams

Description: The internal components of magnetic fusion devices must withstand erosion from and high heat flux of energetic plasma particles. The selection of materials for the construction of these components is important to minimize contamination of the plasma. In order to study various materials' comparative resistance to erosion by energetic particles and their ability to withstand high heat flux, water-cooled copper swirl tubes coated or armored with various materials were subjected to bombardment by hydrogen and helium particle beams. Materials tested were graphite, titanium carbide (TiC), chromium, nickel, copper, silver, gold, and aluminum. Details of the experimental arrangement and methods of application or attachment of the materials to the copper swirl tubes are presented. Results including survivability and mass losses are discussed.
Date: January 1, 1985
Creator: Schechter, D.E.; Tsai, C.C.; Sluss, F.; Becraft, W.R. & Hoffman, D.J.
Partner: UNT Libraries Government Documents Department

Technology of ICH systems for advanced fusion experiments

Description: Work has been done at ORNL to improve existing ICRH technology for machines such as the Tore Supra. Improvements have been made in three components of the ICRH system: the antenna, Faraday shield, and rf vacuum feedthrough. Improvements in power handling capabilities and/or efficiency of a factor of 2-4 have been observed. The resulting overall improvement for the system is then 4-16. (WRF)
Date: January 1, 1985
Creator: Swain, D.W.; Baity, F.W.; Hoffman, D.J.; Owens, T.L. & Tsai, C.C.
Partner: UNT Libraries Government Documents Department

Characteristics of the ORNL ECR multipole plasma source

Description: There are many similarities between the characteristics of the plasma sources needed for semi-conductor processing and those needed for fusion neutral beams. Both need useful plasma areas up to 20-30 cm in diameter and uniform plasma densities (<10% variation for fusion with a factor of about three better needed for semiconductor processing). The evolution of fusion ion sources suggested a development strategy for improved semiconductor processing sources. The first step in this path has now been carried out at ORNL and has produced encouraging results. This progress suggests that this line of development has a good chance of meeting semiconductor processing needs. 2 refs., 5 figs.
Date: January 1, 1989
Creator: Berry, L.A.; Gorbatkin, S.M.; Roberto, J.B.; Tsai, C.C.; Holber, W. & Yeh, J.
Partner: UNT Libraries Government Documents Department