摘要:

A grazing incidence one‐dimensional focusing collector for use in the extreme ultraviolet is described. The collector has a field of view of 1×50°, a focal length of 3015 cm, and a total unobstructed area of 224 cm2. The instrument employs an interchangeable detector package of either channel‐electron multipliers or proportional counters which yield a limiting sensitivity of 1.0 photons/cm2sec A˚ at 170 A˚ and 0.05 photons/cm2sec A˚ at 90 A˚, respectively, for one second integrations. The design and calibration of the instrument are described in detail. Data obtained by this instrument during recent rocket flights are presented.

ISSN:0034-6748    

DOI:10.1063/1.1134223

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Modifications to our previously described detector of magnetic monopoles resulting in substantial improvements in performance have been made. The sensitivity has been increased a factor of 35 by using a sensitive magnetometer (SQUID) to measure changes in current. The modifications, new measurement techniques, and implications for past and future experiments are described.

ISSN:0034-6748    

DOI:10.1063/1.1134224

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A new merged‐beam apparatus is described, which permits the measurement of the energy dependence of the absolute cross sections for ion–neutral and neutral–neutral reactions yielding ionic products over the energy range <0.010 to ∼10 eV. The apparatus has a somewhat different geometry than that of any previous merged‐beam instrument and incorporates several innovations which facilitate the rapid measurement of relative cross sections, the accurate determination of the beam overlap integral, and the high‐resolution measurement of the product energy distribution. The performance of the instrument is illustrated with data on the reaction H+2+ H2→ H+3+ H.

ISSN:0034-6748    

DOI:10.1063/1.1134225

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

An optically thin actinometer is described which measures the rate of photolysis of NO2in air. Operating details of the device are reported together with a test in downtown Detroit. The result was that the instrument was more accurate than some of the other test parameters in the range 0–0.5 min−1. Applications to photochemical smog and stratospheric pollution problems are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1134226

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A description is given of an electromechanical scanning Fabry–Perot interferometer, designed primarily for rapid and precise wavelength comparisons and spectral line profile studies under vacuum conditions. It has a continuously variable path difference range of up to 1 m. Wavelengths may be compared with the present primary krypton‐86 standard to the uncertainty of this standard (± 4 parts in 109). Provision is also made for automatic control of plate parallelism and plate separation.

ISSN:0034-6748    

DOI:10.1063/1.1134227

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A single stage magnetically focused image converter, having a nickel mesh at its first accelerating electrode, was constructed. An S‐11 post‐oxidized photocathode was processed in this image tube. The imaging properties of this type of image converter have been studied under static and pulsed conditions. The output image resolution was studied as a function of the pulse duration or the switching on time. The effect of the application of a pulse to the photocathode or the control grid on the output image resolution is also mentioned. The ’S’ distortion and pincushion distortion under pulsed conditions is also briefly described. Applications of this image converter in spark gap photography, plasma diagnostics, and beam cross‐section photography of the 1.3 GeV synchrotron at Frascati are briefly mentioned.

ISSN:0034-6748    

DOI:10.1063/1.1134219

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A method for reducing the unwanted effect of dust in fluid samples used in light scattering experiments is described. An on‐line minicomputer is employed to reject data accumulated during the presence of dust particles in the light beam, using a digital autocorrelator and a homodyne or heterodyne detection setup. The effectivity of the method is demonstrated by comparing

ISSN:0034-6748    

DOI:10.1063/1.1134220

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A stopped‐flow apparatus is described for the measurement of millidegree changes in optical rotation and absorbance changes at wavelengths between 230 and 800 nm. The design utilizes Faraday modulation at 2.5 kHz and signal processing by selective filtering and phase sensitive detection. Observed rms noise levels are reported for the wavelength range 230–450 nm: representative values for nonabsorbing solutions are 0.2 mdeg at 450 nm (15 nm bandpass, 9 msec time constant) and 3 mdeg at 260 nm (8 nm bandpass, 9 msec time constant). It is shown that these figures correspond to the theoretical shot‐noise limited performance of the instrument. The use of the apparatus is exemplified by studies of the hydroxide ion‐catalyzed mutarotation of glucose, and the displacement of NADH by NAD+from the NADH‐liver alcohol dehydrogenase complex.

ISSN:0034-6748    

DOI:10.1063/1.1134221

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

When a conducting specimen is placed inside a coil, the coil impedance changes. For simple coil and specimen geometries, the impedance change can be related to the electrical resistivity of the specimen. This paper describes a variety of methods for the accurate determination of the resistivity of a cylindrical specimen from the measured change in mutual inductance of a cylindrically symmetric coil assembly. The useful range of resistivity extends from about 3n&OHgr;⋅cm to above 100 &mgr;&OHgr;⋅cm. Using the calibration methods that are described, 1% absolute accuracy is not difficult to obtain even when using a coil system only five coil diameters in length. When compared with calculations for the corresponding infinite specimen and coil problem, the measurements are in disagreement by much more than 1%. Approximate calculations and numerical estimates show that axial field gradients are responsible for these differences when the specimen is more than about twice as long as the coils, and that end effects in the specimen are responsible for the differences when the specimen is short compared to the coil length. The effect of losses other than those in the specimen being studied has also been investigated extensively. We find that in many important experimental circumstances, the conventional procedure of subtracting coil system losses with the specimen absent from those with specimen present can be seriously in error. For instance , if the tail of a metal Dewar, a vacuum can, or the pole faces of an electromagnet are placed so that they intercept some of the return flux of the primary coil, the system losses may not be additive. This occurs because the magnitude of the return flux depends upon the screening currents in the specimen (and hence on the presence or absence of the specimen). This problem is discussed from both an analytical and experimental point of view. An experimental system having very small background losses is described and numerous results on specimens of different lengths and diameters are presented. It can be shown that a radial conductivity variation of about 50% or more can be determined by making measurements at a few frequencies, but that the results are not very sensitive to the functional form of the conductivity variation.

ISSN:0034-6748    

DOI:10.1063/1.1134222

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

An inexpensive method to stabilize the frequency of a CO2laser is described. The method is completely electronic and utilizes variations in the impedance of the laser plasma tube to produce a frequency correction.

ISSN:0034-6748    

DOI:10.1063/1.1134228

出版商:AIP    

年代:1975

数据来源: AIP