摘要:

Flow cytometry instrumentation developed from early efforts to count cells and particles in liquid suspension as they passed through a sensing device. Since the mid‐1960’s sophisticated instruments have been designed for analyzing cells based on various cytological, biochemical, and functional properties. These instruments have revolutionized automated cell analysis methods in that measurements are made at high speed, multiparameter data is correlated on each cell, statistical precision is high, and cells are separated in high purity from heterogeneous mixtures for identification and functional analysis. Advanced instruments capable of measuring cell volume, surface area, multicolor fluorescence, fluorescence polarization, light scatter within various angular regions, and axial light loss (extinction) at different wavelengths are being used in biomedical research for analyzing and sorting normal and abnormal cell populations. This article reviews the development of flow cytometers, the conceptual basis of flow measurements, and discusses some of the numerous applications of the technology in biology and medicine.

ISSN:0034-6748    

DOI:10.1063/1.1137948

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

This paper describes a new diagnostic technique to decode information contained in the spectral and spatial distribution of photons emitted by fast neutral beam particles and provide an estimate of the 2‐D beam density distribution function in a cross‐sectional slice. By scanning Doppler‐shiftedH&agr;radiation from the fast beam particles at a number of peripheral locations around the beam axis, tomographic reconstructions of the beam distribution with spatial resolution &Dgr;x&bartil;2 cm and time resolution &Dgr;t&bartil;10 ms can be made. Using a maximum entropy reconstruction algorithm (making no symmetry assumptions), experimental reconstructions are presented of the 2‐D profile of the beam generated by the prototype JET source for each of the Doppler‐shifted line radiation components. Applications of this image processing technique in other areas of high‐temperature plasma diagnostic development are discussed briefly.

ISSN:0034-6748    

DOI:10.1063/1.1137949

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A potassium‐seeded wall‐stabilized arc source has been developed to provide a stable well‐characterized plasma in which to measure the Stark broadening parameters of potassium excited‐state transitions. Low‐pressure (20‐Torr argon) operation of the arc source reduces the argon collisional broadening contribution to the Stark‐broadened line shapes, while a heated channel wall minimizes radial cataphoresis in the mixed‐gas plasma. The arc source is designed for end‐on observation and is compatible with far‐infrared laser interferometry which is used to determine the effective plasma path length and on‐axis electron density over the current operating range of 5–35 A.

ISSN:0034-6748    

DOI:10.1063/1.1137950

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

We have precisely measured stress distributions in the quartz tubes of high‐energy linear flash lamps, and determined the correlations between the measured stress and flash lamp explosion. Premature lamp explosion can be ascribed to the initial tensile stress at the outer surface of the tube, whereas normal lamp explosion can be ascribed to the accumulated tensile stress at the inner surface. The upper limits of the stresses in these two cases are given so that they can be used to prevent the lamp explosions by removing marginal tubes from use before explosion.

ISSN:0034-6748    

DOI:10.1063/1.1137951

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

In continuous operation a positive hydrogen ion beam up to 240 mA has been extracted at 50 kV out of a single aperture, corresponding to a perveance of 2.1×10−8A/V3/2. The effective mass of the extracted ion beam was measured to be about 1.8 amu. The current density distribution of the extracted ion beam was measured with a small calorimetric probe. It was found that the beam distribution strongly depends on the matching between the plasma current density and the extraction voltage. At overmatched conditions the ion beam may even become hollow. The distribution of the extracted ion beam depends on the pressure along the beam path. At pressures above 3×10−4Torr H2, the distribution was observed to be Gaussian. At a pressure 2×10−5Torr H2, the intensity in the wings of the beam is relatively high with respect to the intensity in the beam center. The beam divergence decreases with the square root of the extraction voltage. The space‐charge potential of the neutralized beam is estimated to be about 5.6 V at 2×10−5Torr decreasing to 1.6 V at 10−3Torr independent of the beam energy.

ISSN:0034-6748    

DOI:10.1063/1.1137952

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Three independent techniques are used to measure the mean ion energy in an intense ion beam accelerated with a standard pinch‐reflex diode. The experimental accelerating voltage agrees with a numerical simulation. The resulting deuteron energy is consistent with the activation results of a BN target and with the hydrodynamic motion of subrange and overrange aluminum foils bombarded by the beam. The accelerating voltage is also used to compare the experimental and computed neutron yields when the beam strikes a CD2target. The total ion current measured with an electrical diagnostic is five to ten times greater than the corresponding deuteron component. This is significantly greater than values reported previously.

ISSN:0034-6748    

DOI:10.1063/1.1137953

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

An apparatus capable of producing current or voltage controlled positive and negative ion beams in 1‐atm oxidizing and nonoxidizing ambients between 25° and 950 °C is presented. The apparatus utilizes a point‐to‐plane corona discharge in the gas phase. Room‐temperature experiments revealed that the small differences in ion beam shape between the two polarities is primarily due to the difference in applied voltage required to produce the same current for the two polarities. Due to increased ion mobility and decreased threshold voltage at higher temperatures, a slight broadening of the ion beam current‐density profiles for both positive and negative ions is predicted.

ISSN:0034-6748    

DOI:10.1063/1.1137954

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

We describe a laser wavelentgh calibration system based on a grating spectroscope used with the method of overlapping orders. Illuminated by a neon spectral lamp it gives about 1500 reference lines. A small mirror, put on the grating axis, is lightened by a He–Ne laser and gives an angular measurement which helps in the identification of the lines. Calibration of the laser wavelength is obtained by linear interpolation between two neighboring reference lines.

ISSN:0034-6748    

DOI:10.1063/1.1137955

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Extensive experimental work has revealed that multielement electrodes are required to provide uniform current distribution in cw coaxial laser discharge configurations. Cylindrical pin electrodes have demonstrated good plasma uniformity, but are vulnerable to damage by high plasma temperatures. This paper describes the design and electrical charcteristics of a new hollow button cathode, which combines excellent discharge performance with greatly improved cooling features.

ISSN:0034-6748    

DOI:10.1063/1.1137945

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A laser current regulator with an operating range of 10 to 50 mA and overall voltages ranging from 2 to 15 kV is described. The current regulation is better than 0.1% for frequencies from dc to 10 kHz. The regulator is designed for operation with a double discharge laser tube in which the two halves of the discharge share a common cathode and one of the anodes is held at ground potential for reasons of operator safety.

ISSN:0034-6748    

DOI:10.1063/1.1137946

出版商:AIP    

年代:1984

数据来源: AIP