摘要:

A toroidal electrostatic analyzer of a design suitable for space plasma instrumentation has been constructed and tested. Experimental results are compared with second‐order ion optical theory and are in good agreement. Verifying the ion optics of the toroid was simplified by use of a position‐sensing microchannel‐plate detector mounted on a positioning system with three translational degrees of freedom located at the toroid exit. The toroidal analyzer described here is the first optical element in a fully toroidal mass spectrograph intended for analysis of kilovolt magnetospheric plasmas.

ISSN:0034-6748    

DOI:10.1063/1.1139260

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Torsatron and stellarator plasma confinement devices rely on magnetic surface mapping to determine the critical vacuum magnetic field structure. A recently developed method employing an emissive filament offers some advantages over the traditional technique of mapping with a directed electron beam. On the Auburn torsatron a comparative study between the emissive filament and directed electron beam techniques has been conducted. The parameters varied in the comparative study are filament geometry, emission current, bias voltage, background gas pressure, and magnetic field strength. This comparative study indicates that the emissive filament technique is reliable over a broad and easily accessible range of parameters. We have also measured the spatial distribution of electrons on a given magnetic surface. As an application of the emissive filament technique, the optimization of the magnetic surfaces on the Auburn torsatron is shown.

ISSN:0034-6748    

DOI:10.1063/1.1139261

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The operation of a Proca and Green type 30° parallel plate electrostatic energy analyzer is modeled in a new manner that permits high‐resolution heavy ion beam probe measurements of fluctuating plasma potential. Systematic calibration procedures permit detection of potential changes smaller than 0.01% of the probing beam energy at frequencies up to a megahertz. Most recent applications of beam probes have made use of this new capability.

ISSN:0034-6748    

DOI:10.1063/1.1139262

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

This paper describes the design, construction, and performance of a single‐stage microchannel‐plate image intensifier used as a photon counting detector over the wavelength range from 1150 to ∼2000 A˚. The intensifer incorporates three high strip current (∼300 &mgr;A) microchannel plates, constructed with 12‐&mgr;‐diam channels and 15‐&mgr; center–center spacing, in a ‘‘Z’’ configuration. The use of high strip current MCPs requires gating the power supply to protect the plates from thermal runaway of the strip current. The output pulses are proximity focused onto a P‐46 phosphor screen, which is fiber‐optically coupled to a linear, self‐scanning photodiode array. Maximum frame rates for the photodiode array are ∼ 125 000 frames/s, with maximum count rates of ∼25 000 photoevents/s. The detector was placed at the focal plane of a 1‐m focal length Ebert–Fastie spectrometer and the performance characteristics of the spectrometer‐detector system were evaluated using a hollow cathode Pt lamp. The linewidths measured during this evaluation demonstrate that the spatial resolution of the detector is better than 50 &mgr;. The spectrometer‐detector system was then used to determine ion temperatures from Doppler broadened impurity lines emitted from plasmas of the Alcator C tokamak. This detector demonstrated more than an order of magnitude increase in sensitivity compared to a photon‐counting photomultiplier tube with a vibrating mirror previously used for these measurements with the same spectrometer. This permitted a determination of the central ion temperature of the Alcator C tokamak using the ‘‘forbidden’’ line of Fexiiat 1354.1 A˚ which was not detected with the previous system.

ISSN:0034-6748    

DOI:10.1063/1.1139263

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A hydrogen beam probing system developed for the REPUTE‐1 reversed field pinch device is described. With this system, the plasma ion line density, the central ion temperature, and the magnetic field profile can be measured. Before being applied to the REPUTE‐1 device, the probing system was tested on the TORIUT‐5 tokamak and TORIUT‐6 ultralow‐q (ULQ) devices. The experimental results show the availability of the system. The measured line density agrees well with that measured by the microwave interferometry. The measurable density ranges from 1019m−3to 3×1020m−3. A new method of magnetic field measurement which is effective and important for RFP plasmas is proposed. The resolution and the accuracy of this measurement have been confirmed by experiments on the TORIUT‐5 device. Experimental results agree well with computation.

ISSN:0034-6748    

DOI:10.1063/1.1139264

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A simple fiber extruder has been developed to produce small diameter filaments of frozen deuterium. The extruder is based on a commercially available liquid‐helium‐cooled cryostat, and only the actual deuterium extruder mechanism must be fabricated. The extruder features interchangeable nozzles and fibers ranging in diameter from 40 to 300 &mgr; have been made. All fibers are over 10 cm in length and their physical dimensions remain unchanged for at least 4 min. The neutral gas density outside the fiber is on the order of 1013and drops off with the inverse of the radius. These fibers are used to provide the plasma for the NRL densez‐pinch experiment whose objective is to study the fusion application of small, dense plasmas.

ISSN:0034-6748    

DOI:10.1063/1.1139265

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The use of an ordinary mode reflectometer has already proved to be a good means for determining the density profile of a plasma, but the fact that this mode reflects where its frequency equals the local plasma frequency restricts its use to the region of the density gradient. The extraordinary mode reflectometry investigated here permits the observation of the scrape‐off layer as well as the near‐axis region and in certain conditions also the high magnetic field side of the density profile. It is also shown that this mode requires a range of frequency sweep for measuring a given density profile smaller than the ordinary mode. On the Petula‐B tokamak, the density profile has been measured in 200 &mgr;s, its evolution when applying the lower hybrid current drive could be also followed. Since the measurement is particularly sensitive near the reflection point of the wave, it could be used to determine precisely the position of magnetic islands and the fluctuation amplitudes. In addition, the access and place occupied in the vacuum chamber being very small, this diagnostic should be compatible with reactor conditions.

ISSN:0034-6748    

DOI:10.1063/1.1139266

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A cold atomic hydrogen beam source has been built and tested at BNL. The flow channel of the source, consisting of a discharge tube, a constricting nozzle, a thermal transition section, and an accommodator, was designed to operate in the laminar flow range. A novel feature of this source is a 0.3‐mm gap between the transition Teflon tube which guides the flow and an accommodator which cools the flowing gas; across this gap the wall temperature may step from 100 K in the Teflon to 3 K in the accommodator. A record pulsed H° beam flux of 9.4×1018H° sr−1 s−1was obtained at an accommodator temperature of 5.8 K. The gas dynamic analysis of the system is in excellent agreement with the experimental results.

ISSN:0034-6748    

DOI:10.1063/1.1139267

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We have constructed a 1.20‐T pole tip field quadrupole magnet which is used to separate electrically neutral metal clusters by their spin magnetic moment. The device is magnetically energized with rare‐earth samarium cobalt magnets. The use of this material allows for both the low cost and the small size of the device.

ISSN:0034-6748    

DOI:10.1063/1.1139268

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

An electro‐optic modulator using LiTaO3is described which yields 34% of the carrier intensity in each of the first‐order sidebands with rf phase modulation frequenciesfm∼1.0 GHz and ≲1.0 W input power. The modulator makes use of a lumped resonator withQ∼200 to obtain efficient production of the sidebands. It is shown that the device can be scaled for operation at ∼2 GHz. Applications of this modulator include optical pumping of the lighter alkali atoms,FMsideband spectroscopy, and laser phase/frequency stabilization using rf modulation techniques.

ISSN:0034-6748    

DOI:10.1063/1.1139269

出版商:AIP    

年代:1987

数据来源: AIP