摘要:

Magnet design codes, plasma dispersion solvers, and particle‐in‐cell (PIC) simulation codes have been used to arrive at the first step in the design of an advanced ion source based on electron cyclotron resonance (ECR) technology. The advanced concept design uses a minimum‐Bmagnetic mirror geometry which consists of a multicusp magnetic field to assist in confining the plasma radially, a flat central field for tuning to the ECR resonant condition, and specially tailored mirror fields in the end zones to confine the plasma in the axial direction. The magnetic field is designed to achieve an axially symmetric plasma ‘‘volume’’ with constant mod‐B, which extends over the length of the central field region. This design, which strongly contrasts with ‘‘surface’’ ECR zones characteristic of conventional ECR ion sources, results in dramatic increases in the absorption of rf power, thereby increasing the electron temperature and ‘‘hot’’ electron population within the ionization volume of the source. The creation of a volume rather than a surface ECR zone is, therefore, commensurate with the generation of higher beam intensities, higher charge states, and a higher degree of ionization. A summary of the results of these studies is presented in this report.

ISSN:0034-6748    

DOI:10.1063/1.1144954

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The 1903 Trouton–Noble (TN) experiment, which sought a torque on a charged capacitor, is often regarded as the electrostatic equivalent of the Michelson–Morley experiment, inasmuch as it was supposed to have detected ether drift, and it yielded a null result. The present experiment was designed to be the electrostatic equivalent of the Michelson–Gale experiment, which was performed to detect the rotational velocity of the earth and which yielded a nonnull result. The present experiment is 105times as sensitive as the original TN experiment, but yields a null result nonetheless. Although the TN experiment is often regarded as crucial, a footnote in the original paper reveals the conjectural nature of the theory.

ISSN:0034-6748    

DOI:10.1063/1.1144955

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A technique of initiation of a self‐sustained electrical discharge for pumping excimer lasers, based on the use of a stabilizing predischarge with an electron densityNe∼1012–1013cm−3, has been developed. It has been demonstrated that such an auxiliary discharge is stable for random disturbances of the plasma parameters. An efficient, stable, and highly homogeneous pumping discharge of duration up to 800 ns with an aperture of 6×12 cm2and current density of ∼300 A/cm2has been realized in Ne(He,Ar)/Xe(Kr)/HCl mixtures. The proposed technique can be used in developing wide‐aperture excimer lasers and shows promise for creating high‐repetition‐rate systems of kilowatt average power.

ISSN:0034-6748    

DOI:10.1063/1.1145236

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The use of a spherical mirror Fabry–Perot cavity as a mirror of variable reflectivity for near monochromatic light is demonstrated herein. The results of an experimental test of two control systems for the variable mirror are presented. It is shown that the reflectivity of our mirror can be controllably varied over a wide range. This technique has application in laser interferometric gravitational‐wave detection.

ISSN:0034-6748    

DOI:10.1063/1.1144903

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Some problems of temperature stabilization of light‐emitting diode (LED) radiation have been discussed in the paper. Temperature–electrical characteristics of LED have been discussed and a way has been suggested to use them for the improvement of techniques for the temperature stabilization of their radiation power. There exists a possibility of developing one common monolithic LED‐compensation system, and at the same time, a thermally compensated electroluminescence diode. The compensation system presented in the paper, in which an LED is a source of radiation and a temperature sensor, is not complicated and is practical in measurements where thermal conditions undergo fast changes. The presented system for the thermal stabilization can be adapted for impulse work, which allows for a considerable increase of LED radiation power. It has been proved in the paper that LED is an original source of radiation which can be applied to a construction of photometers of different kinds, working in real field conditions.

ISSN:0034-6748    

DOI:10.1063/1.1144904

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A high‐sensitivity, laser‐excited, confocal‐fluorescence scanner has been developed for the detection of fluorescently labeled nucleic acids separated on slab gels. The gel is placed on a motor‐driven, two‐dimensional scan stage and raster scanned past the optical detection system. The 488‐nm argon ion laser beam is introduced into the confocal optical system at a long‐pass dichroic beam splitter and focused within the gel to an ∼2 &mgr;m diameter spot by a high‐numerical aperture microscope objective. The resulting fluorescence is gathered by the objective, passed back through the first long‐pass beam splitter, and relayed to a second dichroic beam splitter that separates the red and green emissions. The fluorescence is then focused on confocal spatial filters to reduce stray and scattered light, passed through spectral filters, and detected with photomultipliers. The resulting signals are amplified, filtered, and digitized for display on a computer. This system can detect as little as 5×10−12M fluorescein, the resolution as operated is 160 &mgr;m, and it can scan a 6 cm×6 cm gel using a scan rate of 4 cm/s in 12 min. The detection of DNA on slab gels, two‐color DNA fragment sizing, and microtiter plate scanning are presented to illustrate some of the possible applications of this apparatus.  

ISSN:0034-6748    

DOI:10.1063/1.1144905

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A two‐dimensional, ultraviolet photon‐counting detector suitable for spaceflight use, consisting of a microchannel plate intensifier coupled to a Reticon photodiode array, has been constructed and tested. The design is an extension of the one‐dimensional detector flown on theHopkinsUltravioletTelescope. Extensive laboratory measurements have determined the operating characteristics of the detector and shown that it can successfully centroid with subdiode resolution. It was flown as part of an ultraviolet spectrometer on two sounding rockets, and successfully obtained long slit spectra of Comet Austin (1990 V) and the Io plasma torus surrounding Jupiter in the wavelength range of 1150–1850 A˚. Details of the design, construction, testing, and flight performance of the detector are presented.

ISSN:0034-6748    

DOI:10.1063/1.1144906

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

We describe here the details of the concept, the construction, and the performance of an accurate and inexpensive sidereal tracking drive unit (SDU) for the 1‐m or larger class of astronomical telescopes. The SDU is tunable and has a very highly stable and undistorted sinusoidal wave shape. The SDU consists mainly of a variable drift‐free drive rate generator and a distortion‐free, low‐cost power amplifier. Tracking accuracies of less than a couple of arcseconds in sky are achieved in 60 min of observation time. The unit can also be used in negative feed back mode to correct any errors in the tracking system. The accuracies in frequency stability obtainable with the SDU and the feasibility of operation in negative feedback mode for correcting tracking errors are not possible in the commercially available battery back‐up uninterrupted power supply (UPS) units. The total cost of the SDU currently works out to be approximately $200 (US) and requires about one man‐month for building and testing.

ISSN:0034-6748    

DOI:10.1063/1.1144907

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A soft x‐ray beamline designed principally for gas phase measurements has been constructed and tested at the 550‐MeV MAX I electron storage ring in Lund, Sweden. The beamline uses synchrotron radiation from a short 35‐period undulator with a magnetic period of 24 mm. The photon energy range of the undulator is about 60–600 eV covering, e.g., the important C, N and O 1sionization regions. The beamline is based on a modified SX‐700 plane grating monochromator with a plane elliptical focusing mirror. The beamline has been tested by measuring total ion and electron yield spectra from the rare gases Kr and Ar in the resonance excitation regions just below the KrM4,5and ArL2,3ionization thresholds. These results show that the monochromator has very high resolution,E/&Dgr;E≊4800 at 244 eV and ≊7600 at 91 eV, comparable with the best spherical and plane grating monochromators. The beamline is equipped with an effective differential pumping system for the gas phase experiments combined with a refocusing mirror in order to provide a small spot size (&fgr;<1 mm) at the sample region.

ISSN:0034-6748    

DOI:10.1063/1.1145234

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A new surface characterization technique with a lateral spatial resolution has been developed for nondestructive surface analysis using a synchrotron x‐ray microbeam. The grazing‐exit condition for fluorescent x‐ray detection is utilized to attain the surface sensitivity. A focused x‐ray microbeam of high photon flux has realized a lateral spatial resolution of a few &mgr;m. A layered thin‐film electrode is analyzed in both the scanning and point modes. In the point mode, the analyzing position is fixed while the exit angle is changed. The characterization of thin films over a small region is made. In the scanning mode, the exit angle is fixed while the sample is being scanned. The two‐dimensional intensity distribution reflects depth information in addition to the lateral elemental distribution. The intensity modulation near to the surface step of the pattern edge is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1144908

出版商:AIP    

年代:1994

数据来源: AIP