摘要:

If the major axes of the helical and vertical field coils of a torsatron plasma confinement device are not aligned to within ∼1% of their major radii, the resulting error field can break up closed magnetic flux surfaces and reduce the effective plasma confinement volume. A novel technique for accurately locating the magnetic symmetry axes of torsatron helical and vertical coil sets to within ∼1 mm using magnetic field measurements near the device major axis (i.e., away from the confinement volume) is described and applied to the URAGAN‐3 torsatron. The axis of the vertical field coil set was found to be shifted by ∼1 cm relative to the axis of the helical coil set; this shift could account for the reduced confinement volume observed in previous experiments. The magnetic measurements were repeated after coil repositioning to verify correct alignment.

ISSN:0034-6748    

DOI:10.1063/1.1138634

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Compact, vacuum‐compatible submillimeter viewing dumps, whose design parameters were based on the results of simple ray calculations, have been fabricated from Pyrex, Macor, and alumina. The measured performance of the dumps agrees qualitatively with calculated results. The absorption is somewhat lower than expected, but still acceptable (≥99% absorption for Pyrex and Macor). In an electron cyclotron plasma emission experiment on Alcator C tokamak, comparison of the emission spectra with and without the dump shows that the dump in this configuration is effective in suppressing the unwanted radiation by approximately 90%. The additional reflection is believed to be due to a portion of the antenna pattern missing the dump.

ISSN:0034-6748    

DOI:10.1063/1.1138635

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We have developed a simulated load technique for estimating power dissipation and effective impedance of the discharge which is useful over a wide range of driver frequencies. This is used to calculate the power delivered to the plasma and plasma current for frequencies from 0.12 to 13.56 MHz. This technique allows an efficiency calibration curve to be made for a given match circuit which can be quickly applied to any new discharge condition to give match efficiency.

ISSN:0034-6748    

DOI:10.1063/1.1138636

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A novel type of ion spectrometer for laser‐produced plasma diagnostics is described. The Thomson parabola configuration is used to separate the expanding plasma ions according to their different charge‐to‐mass ratios. One particular ion species is subsequently collected by a parabola‐shaped charge collector. In this way ion velocity distributions of a single charge‐to‐mass ratio are obtained through simple time‐of‐flight analysis. Measured ion energies can be as low as 1 keV per nucleon.

ISSN:0034-6748    

DOI:10.1063/1.1138637

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The techniques, operational aspects, and experimental results of a radio frequency induction plasma generator, with an internal rf power coupler, intended for intense neutral beam applications are described. One of the development sources suitable for 10×10‐cm2extraction optics was operated to a deuterium ion current density of 250 mA/cm2, uniform to 5%, over a circular extraction area 15 cm in diameter with a coupled rf power of 20 kW. Temporal fluctuation levels in the extracted ion current were measured to be typically 1% of the dc level. A second developmental source suitable for 10×40‐cm2grid sets was operated to 200 mA/cm2, uniform to ±8% over a 10×40 cm2area, with 40‐kW coupled rf power.

ISSN:0034-6748    

DOI:10.1063/1.1138638

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Beam extraction tests at energies up to 80 kV were performed using a radio frequency induction (RFI) plasma generator hydrogen ion source. A 7×10‐cm2, long pulse accelerator was operated with a 10×10‐cm2axial magnetic cusp bucket and a magnetic‐filter bucket. Atomic fractions (up to 85% H+), plasma production efficiencies (≊0.6 A of beam per kW rf power), and beam divergence were at least as good as with arc plasmas in similar chambers. Potential advantages of the RFI plasma sources for large‐scale applications are ease of operation, reliability, and extended service life.

ISSN:0034-6748    

DOI:10.1063/1.1138639

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A 160‐keV neutral deuterium beam injector has been developed for plasma heating in JET (Joint European Torus) fusion experiment. This injector has been reliably operated at 5.9‐MW extracted deuterium ion beam power (37‐A, 160‐keV ion beam) and 5‐s pulse duration. The neutral beam power was 1.75 MW corresponding to an overall neutral injector power efficiency of 30%. The beam divergence was 0.6°. The ion beam was accelerated with a three‐grid multiaperture system (aperture diameter &fgr;=11 mm). The accelerating gap length was 24 mm. The extracted deuterium ion current density amounted to 150 mA/cm2. Grid and source body power loadings were acceptable for quasi‐steady‐state operation.

ISSN:0034-6748    

DOI:10.1063/1.1138640

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A directly heated, cylindrical LaB6cathode has been tested in a multicusp plasma generator. Magnetic fields generated by the heater and the discharge current are minimized by the special coaxial construction, thus enabling electron emission at very low discharge voltages. At higher discharge voltage, a discharge current greater than 100 A has been obtained from a single cathode unit in a steady‐state plasma source operation. When the discharge current exceeds 25 A, the cathode can be operated without any heater current. The emission temperature is maintained just by ion bombardment from the discharge plasma.

ISSN:0034-6748    

DOI:10.1063/1.1138641

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We describe a dc volume H−source, employing multicusp plasma confinement, which has been constructed for use with the TRIUMF cyclotron. An extracted H−current density of 12 mA/cm2has been obtained. Beam emittance and brightness have been measured as a function of current density and beam fraction. Beam brightness values for normalized beam emittances of the order of 0.2 &pgr;mm mrad at 81% beam fraction are typically 10 mA/(mm mrad)2[equivalent rmsB=223 mA/(mm mrad)2].

ISSN:0034-6748    

DOI:10.1063/1.1138642

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A liquid metal ion source of Al with a boride reservoir was developed. In this reservoir a shorter boride emitter was designed to overcome the brittleness of boride materials and some problems in supplying the Al material. This source makes possible a long continuous operation time and enhanced reliability. The fundamental performance characteristics did not change after 250 h of operation. A stable Al ion beam emission was obtained for more than 500 h and its current fluctuation was less than ±1%/3 h for a 20–30‐&mgr;A source ion current. The energy spread was less than 9 eV (FWHM) for a 30‐&mgr;A/sr angular current intensity.

ISSN:0034-6748    

DOI:10.1063/1.1138643

出版商:AIP    

年代:1986

数据来源: AIP