摘要:

The proposals and experience in production and transportation of ion beams with high brightness are discussed. The attention is concentrated on the seldom‐discussed distinctive features of high brightness beam formation in noiseless regimes of negative ion source operation. Beam quality enhancement up to level j/T=1 A/cm2eV is possible by optimization of negative ion generation, extraction, and transportation in surface plasma sources with cesium catalysis. A strong drop in brightness of a highly expanded beam, caused by fluctuating fields (the overheating through overcooling) has been observed. The magnification of the electric field fluctuations by the collapsed concentration of oscillating secondary particles is discussed. The influence of feedback by secondary particles in the excitation of large beam instabilities and fluctuating microstructure of a noiseless negative ion beam is discussed.

ISSN:0094-243X    

DOI:10.1063/1.44787

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We fabricate a new small hollow−cathode Penning SPS with a multiaperture extraction for the anode N1 production study. It was found, that the anode surface conversion of superthermal and fast hydrogen atoms into H−ions is effectively realized in the Penning SPS in the case of an increased, cesiated anode surface. (AIP)

ISSN:0094-243X    

DOI:10.1063/1.44788

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The small‐angle source (SAS), 4X source, and 8X source are Penning surface‐plasma sources (SPS) that produce high‐current, high‐brightness H−ion beams for accelerator applications. It is desirable to achieve high duty‐factor (df) operation, ultimately dc, with a Penning SPS. Two developments may make this goal possible. First, the H−beam‐emission scaling from the SAS (the 1X device) to the 4X source, and from the 4X source to the 8X source, is more favorable than the scaling laws predict. Second, fringe‐field separation of the e−and H−beams may make it possible to handle the power of the coextracted e−beam, especially since a collar arrangement reduces the e−loading. We compare our measured results with the predictions of the Penning SPS scaling laws. Particular attention is paid to the H−current and temperature scaling as well as the power efficiency.

ISSN:0094-243X    

DOI:10.1063/1.44790

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Using the 4X source performance and the Penning SPS scaling laws, we predicted the performance of the 8X source. A pulsed 8X source was then built and tested. After verifying the pulsed 8X source operation, especially the H−beam current, emittance, and power efficiency, we designed and built the CW 8X source. We plan to operate the source arc at dc power levels up to 30 kW. This will be accomplished by actively cooling the electrode surfaces with pressurized, hot water. The CW 8X source is presently undergoing shake‐down tests on a test stand at Los Alamos. Evaluation of the high‐current, hydrogen‐cesium dc arc will begin when these tests are completed.

ISSN:0094-243X    

DOI:10.1063/1.44791

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We are developing a surface‐conversion source, using a 10 cm diameter solid barium converter, to produce D−ion beams suitable for acceleration by the ESQ accelerator. The ion temperature was found to be ≊3% of the converter bias potential. The efficiency of converting D+to D−is as high as 4.8% but only 25% of the D−ions survived to leave the source without being stripped by the plasma or the gas molecules. Some early results from the RF discharges are promising because of their higher power efficiency and gas efficiency.

ISSN:0094-243X    

DOI:10.1063/1.44792

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

For realization of the long and stable operating conditions some changes were done in the H−ion source with cesium hollow cathode. The results of testing such a source and the obtained characteristics are given in the paper.

ISSN:0094-243X    

DOI:10.1063/1.44793

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Recent results of R&D on high current negative ion source at JAERI are ion beam production, the R&D work has been progressed toward longer pulse beam production and the beam optics. A long pulse operation for 24 hours was demonstrated stably with a small cesiated volume source. It was confirmed that the heat load in the source is a modest level allowable for the long pulse operation. The cesium effect lasted for 24 hours, once the cesium was seeded before operation. In beam optics study, we have produced a beam with very small divergent angle of 1.5 mrad. To take this advantage for a design of compact neutral beam system, beamlet focusing technique by aperture displacement was applied in the H−beam extractor.

ISSN:0094-243X    

DOI:10.1063/1.44794

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Cesium effects have been investigated in a semi‐cylindrical negative ion source whose inner dimensions are 34 cm in diameter and 129 cm in length. D−and H−ion beams were extracted and accelerated by a multiaperture extraction system, which has 240 holes of 11.3 mm in diameter within an area of 6 cm×120 cm. The cesium effects, i.e., enhancement of the negative ion current and reduction of the optimum pressure and electron current, have been observed both in deuterium and in hydrogen operations. The enhancement factor of the D−ion beam current by cesium was higher than that of the H−ion beam current. Though the D−current had a strong tendency of saturation with arc discharge power in pure volume operation, the D−ion beam current was increased linearly with arc discharge power in cesium seeded operation. The ration of the D−ion beam current to the H−ion beam current was 0.8 in cesium seeded operation while the ratio in pure volume operation was 0.5. The D−ion beams more than 2.2 A with an average current density of about 10 mA/cm2was obtained at an energy of 100 keV for 5 sec at the beam targets which were located at 4 m and 6.4 m from the source.

ISSN:0094-243X    

DOI:10.1063/1.44795

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The 1/3‐scaled H−ion source for NBI‐system of Large Helical Device has been developed. By seeding cesium vapor into the multicusp plasma source, the H−ion current is enhanced 3 times larger than that in pure hydrogen operation. The reduction of electron current and operating gas pressure is also observed. Total H−ion current of 8.5 A has been obtained from 800 extraction holes of 9 mm in diameter arranging in a large area of 25×50 cm2. The ratio of electron to H−ion current can be reduced to 2 by using the EggBox Cell placed on the plasma grid. From 36 extraction holes, the H−ion current of 1.24 A has been obtained with the extraction voltage of 8.5 kV, which corresponds to the current density of 54 mA/cm2. The H−ion current density increases as an extraction voltage and an input arc power increase.

ISSN:0094-243X    

DOI:10.1063/1.44796

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A review is given of progress in ion source performance at the cw test stand. Data is presented both for pure and cesiated source performance. For uncesiated operation we show how the performance depends on cathode area by changing both filament number and diameter. We have proved that this is due to the collection of ions from the plasma by the cathode structure. Through the use of cesium in the ion source the H−and D−current is enhanced by about a factor of two. An accelerator perveance limit was identified which prevented all the current available from the source being transported, but this was overcome by a new accelerator design allowing very high currents, 86 mA of H−and 37.3 mA of D−, to be extracted from a 16 mm diameter aperture.

ISSN:0094-243X    

DOI:10.1063/1.44797

出版商:AIP    

年代:1992

数据来源: AIP