Surface Plasma Source Research Articles

H− source and low energy transport for an RFQ preinjector

A radio-frequency quadrupole (RFQ) accelerator has replaced a 750-keV Cockcroft-Walton as the H− preinjector for the Brookhaven alternating gradient synchrotron. A magnetron surface-plasma source with a circular aperture is used to produce 65–100 mA of H− at 35 keV with a discharge current of less than 20 A. The symmetry of the beam is maintained in the 2-m transport to the RFQ via the use of magnetic solenoids for focusing. Currents up to 60 mA have been obtained out of the RFQ. A traveling-wave electrostatic chopper in the 35-keV transport line leads to a distortion of the emittance due to space-charge effects.

Studies of surface-plasma negative ion sources at Novosibirsk

STUDIES OF SURFACE-PLASMA NEGATIVE ION SOURCES AT NOVOSIBIRSK Yu. I. Belchenko, G. E. Derevyankin, G. I. Dimov, and V. G. Dudnikov UDC 621.385(088.8) The recharging method is often used to control particle flows in accelerator technology and magnetic controlled thermonuclear synthesis systems. This method permits use of a change in particle charge state to control motion in electric and magnetic fields, change the magnitude and direction of particle acceleration, "switch on" and "switch off" the action of macroscopic fields, affect particle distribution in phase space, etc. G. I. Budker produced a significant contribution to the development of the recharging method for control of accelerated particle flows. He prosposed the use of dissociation of rapid molecular ions upon collisions with residual gas and plasma to fill magnetic hot plasma traps in his first study of mirror traps in 1954. At his initiative the Nuclear Physics Institute of the Siberian Branch, Academy of Sciences of the USSR developed a recharging method for proton injection into cyclical accelerators and accumulators [i, 2], together with physical bases for producing intense atomic beams of high energy hydrogen isotopes for injec- tion into thermonuclear traps [3-6]. A convenient method for producing high energy hydrogen particles is stripping of accelerated negative hydrogen ions which easily lose their "excess" electron in collisions on the recharging target and have a high (0.6-0.9) coefficient of conversion into atoms over a wide range of particle energies. Studies of H- ion sources at the Nuclear Physics Institute of the Siberian Branch, Aca- demy of Sciences of the USSR were begun in connection with development of the recharging method for proton injection into accelerators. For this purpose plasma sources were developed at the Institute (Elers type sources) with pulsed current up to 8 mA, together with recharg- ing sources first at a current of 15 mA, later up to I00 mA. However the characteristics of these sources did not permit complete realization of the advantages of recharging injection so that the latter were not widely used in accelerators. The situation with respect to production of negative ion beams improved radically after observation and experimental study of a new surface-plasma mechanism for negative ion forma- tion in gas discharges [3]. Using this mechanism a number of surface-plasma H- ion sources were developed for accelerators. Moreover, the surface-plasma method proved so effective that it could be used for development of high power negative ion sources for controlled thermo- nuclear synthesis. Major contributions to development of surface-plasma sources were also made by labora- tories in the USA (Brookhaven, Berkeley, Los Alamos, Oak Ridge, Fermi Lab), a number of laboratories in the Soviet Union, Europe, and Japan. These results are reflected in the proceedings of the International Symposium on Production and Neutralization of Negative Ions [7-9], accelerator conferences, and many other publications. In the present study we will briefly consider the results obtained at the Nuclear Physics Institute of the Siberian Branch~ Academy of Sciences of the USSR. Some achievements of these studies were considered in [4, 5, i0, ii], which offer citations of the original literature involved. Studies of the Physical Basis of the Surface-Plasma Method for Producing Negative Ion Beams. The first major results which served as a base for development of the surface-plasma method for generating negative ion beams and surface-plasma sources were obtained at the Institute in 1970. At that time note was made of the possibility in principle of forming H- ions due to secondary emission of negative ions upon bombardment by ions of surfaces with a reduced work function. Experiments performed revealed that upon bombardment of metal Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 106-115, July-August, 1987. Original article submitted December 26, 1986. 568 0021-8944/87/2804-0568512.50 9 1988 Plenum Publishing Corporation

On geometric focusing of hydrogen negative ions in the surface-plasma sources

Analyse detaillee du rendement de la focalisation geometrique dans les sources plasma-surface

Negative ion surface-plasma source development for fusion in Novosibirsk

This paper is a review of research effected on negative ion plasma-surface sources in the Institute of Nuclear Physics in Novosibirsk. It contains the description of the performances of the planatron, a source which produced in 1972 in pure hydrogen a density of H- ion current of 0.75 A/cm2. The results of recent studies of this source, in the 1987 version, designated as semi-planatron, are also presented. The experiments effected by adding cesium to the hydrogen discharge lead to a theoretical model of the surface-plasma sources with low work function cathode. The optimization of the negative ion production led to the increase of the beam intensity to 11 A.

H- production in pure hydrogen discharges of surface-plasma sources

H- production in pure hydrogen discharges of surface-plasma sources

Continuous operated H−-surface plasma ion source

A H−-surface plasma source with a cesiated converter electrode has been operated continuously. Out of a single extraction aperture of a diameter of 13 mm, a H− current of 50 mA has been extracted with reasonable beam properties. The current was limited by the extraction voltage of 30 kV. The dependence of the generated H− current on different parameters has been examined. In addition, the profile and the emittance of the extracted ion beam has been measured. At optimum conditions, the beam divergence was found to be ±22 mrad. The normalized rms emittance was measured to be 0.4×10−6 π mrad. The emittance of the beam is mainly determined by the geometrical arrangement of the converter electrode with respect to the extraction aperture.

Spectroscopic Measurements on an H- Ion Source Discharge

Spectral emission lines from an H- Penning surface-plasma source (SPS), the 4X source, are examined in the visible and near ultraviolet. Electron distribution temperatures are deduced from integral line-strength measurements. These temperatures are surprisingly low, about 0.5 eV. Electron density values of about 1.5 × 1014 cm-3 and H-atom energies between 2 and 2.6 eV are determined from the measured Balmer-line profiles. Assuming the H- energy is identical to the H-atom energy, an emittance limit of 0.006π·cm·mrad is deduced for this source with a 5.4-mm aperture.

The 4X Source

Our Penning surface-plasma source (SPS) discharge chamber was enlarged 4X in two dimensions. To date, three pulsed discharge modes have been studied: two with noisy arc (#x02273;20% H- current fluctuations) and one with quiescent arc (≲1% H- current fluctuations). Lower arc magnetic field and higher H2 gas flow allow switching from the noisy to the quiescent mode. The noisy modes yield up to 120 mA of 29-keV H- beam; for 110 mA at 29 keV, the two-dimensional normalized rms emittance is 0.017 x 0.018 π·cm·mrad. The quiescent mode yields 75 mA of 29-keV H- beam; for 67 mA at 24 keV, the emittance is 0.011 x 0.012 π·cm·mrad.

An Efficient Ionizer for Polarized H- Formation

An ionizer is under development for a polarized H-source based on the resonant charge exchange reaction HH#x02192°+D- H#x02192-+D°. The H#x02192° beam passes through the center of a magnetron surface-plasma source having an annular geometry, where it crosses a high current (~0.5 A), 200 eV D-beam. Calculations predict an H°H#x02192- ionization efficiency of ~ 7%, 1 more than an order of magnitude higher than that obtained on present ground state atomic beam sources. In initial experiments using an unpolarized H° beam, H- currents in excess of 100 µA have been measured. While the ionization efficiency is now only about the same as other methods (Cs beam, for example), the results are encouraging since it appears that by injecting positive ions to improve the space-charge neutralization, and by improving the extraction optics, considerable gains in intensity will be made. We will then use this ionizer with a polarized H' beam, and measure the polarization of the resulting H-beam. If no depolarization is observed this ionizer will be combined with an atomic beam, cooled to 5-6 K, 2 to give a polarized H- beam expected to be in the milliampere range for use in the AGS.

A model for the dependence of H - ion production on the converter potential in a surface plasma source

An elementary model for the production of negative hydrogen ions on a W(110) converter surface in a hydrogen plasma is presented. The calculated equilibrium cesium coverage is far from optimum in a high density plasma. The optimum converter potential for H - ion production is ∼ -200 V with respect to the plasma.

H− beam emittance measurements for the Penning and the asymmetric, grooved magnetron surface-plasma sources

H− beam emittance measurements for the Penning and the asymmetric, grooved magnetron surface-plasma sources

H− beam emittance measurements for the Penning and the asymmetric, grooved magnetron surface-plasma sources

Beam intensity and emittance measurements show that the H− beam from our Penning surface-plasma source (SPS) has twice the intensity and ten times the brightness of the H− beam from an asymmetric, grooved magnetron SPS. H− ion temperatures of 5 eV for the Penning SPS and 22 eV for the asymmetric, grooved magnetron are deduced by using a simple emittance theory and the present emittance measurements.

Measurements of the Cesium Flow from a Surface-Plasma H- Ion Source

We have constructed a surface ionization gauge (SIG) and have used it to measure the Cs0 flow rate through the emission slit of a surface-plasma source (SPS) of H- ions with Penning geometry. The equivalent cesium density in the SPS discharge is deduced from these flow measurements. For dc operation the optimum H- current occurs at an equivalent cesium density of ~7 × 1012 cm-3 (corresponding to an average cesium consumption rate of 0.5 mg/h). For pulsed operation the optimum H- current occurs at an equivalent cesium density of ~2 × 1013 cm-3 (1-mg/h average cesium consumption rate). We observe cesium trapping by the SPS discharge for both dc and pulsed operation. A cesium energy of ~0.1 eV is deduced from the observed time of flight to the SIG. In addition to providing information on the physics of the source, the SIG is a useful diagnostic tool for source startup and operation.

A 100-mA Negative Hydrogen-Ion Source for Accelerators

A surface-plasma source of H/sup -/ ions was developed and designed for powerful linear accelerators (meson factories) and also for circular accelerators with charge-exchange injection of protons, especially for boosters of the proton synchrotrons. Parameters of the source (nominal values are given in parentheses) are: repetition rate of up to 100 (100) Hz, current pulse duration of 100 to 300 (200) msec, output current of the H/sup -/ ion beam of up to 150 (100) mA, ion energy of 10 to 30 (20) keV.

Addendum: Theses and Dissertations Accepted by Graduate Library Schools: 1972 through December 1973

Previous articleNext article No AccessAddendum: Theses and Dissertations Accepted by Graduate Library Schools: 1972 through December 1973PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Library Quarterly Volume 45, Number 1Jan., 1975Proceedings of the Thirty-Seventh Annual Conference of the Graduate Library School, August 5-6, 1974. Differentiating the Media: A Focus on Library Selection and Use of Communication Content Article DOIhttps://doi.org/10.1086/620364 Citations: 2Citations are reported from Crossref Copyright 1975 The University of ChicagoPDF download Crossref reports the following articles citing this article:Vadim Dudnikov General Remarks on Surface Plasma Sources, (Oct 2019): 309–318.https://doi.org/10.1007/978-3-030-28437-4_7Vadim Dudnikov Surface Plasma Production of Negative Ions, (Oct 2019): 73–153.https://doi.org/10.1007/978-3-030-28437-4_4Related articlesTheses and Dissertations Accepted by Graduate Library Schools: 1972 through December 197329 Sep 2015The Library Quarterly