摘要:

The parameters governing the time response of an RCA 1P28 photomultiplier are investigated, and special circuitry for optimum time response is described. Photomultiplier performance is extensively evaluated with respect to application in flash photolysis and pulse radiolysis. The output signal rise time achieved is 360 psec for a light impulse and 540 psec for a step function over a linear range extending to an anode current of 8 mA.

ISSN:0034-6748    

DOI:10.1063/1.1134685

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A new technique to obtain reflection high energy electron diffraction (RHEED) double patterns has been developed. This technique has allowed us to obtain simultaneously the RHEED patterns of a thin film and of the single crystal substrate on which the same thin film has been grown. It is possible to have an identification and a relative calibration, on the same exposure, of the crystalline parameters of the film under observation utilizing the simultaneous diffraction pattern of the substrate.

ISSN:0034-6748    

DOI:10.1063/1.1134686

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A crystal monochromator with a logarithmic‐spiral curvature has been designed as part of a low‐angle x‐ray diffraction camera that uses synchrotron radiation emanating from the storage ring SPEAR at Stanford Linear Accelerator Center. The logarithmic‐spiral curvature allows a greater demagnification of the source than is permitted by a cylindrical geometry. Independent bending couples are applied at both ends of a rectangular crystal plate via pairs of parallel rods which rotate under a linear push from differential micrometer screws. Stepping motors control the bending mechanism, theta motion, guard slits, and camera alignment. A tenfold demagnification of the source is readily obtained. Focusing is rapid and easy. The crystal monochromator is combined with a focusing mirror in order to eliminate harmonics and produce a point focus (Webb, Samson, Stroud, Gamble, and Baldeschwieler, 1975).

ISSN:0034-6748    

DOI:10.1063/1.1134687

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The theory and operation of a time‐of‐flight mass spectrometer employing a multichannel electrostatic analyzer are discussed with emphasis placed on laser‐produced plasma studies. It is shown that the finite length of the analyzer leads to enhanced mass resolution. A method ofinsitucalibration of the analyzer channels is described, and measurements of the resolution and beam divergence are presented. Use of the mass spectrometer to calibrate ion‐collecting probes for mass and kinetic energy measurements is also considered.

ISSN:0034-6748    

DOI:10.1063/1.1134688

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A double‐prism variable‐beam attenuator for 10.6 &mgr;m, which is based on frustrated total internal reflection, has been built. The attenuation can be varied between 2 dB and more than 105 dB, and the transmitted power is independent of the beam polarization. For high attenuations, the phase behavior is that of a quarter‐wave plate. With the aid of a visible laser beam, the prism gap can be monitored interferometrically.

ISSN:0034-6748    

DOI:10.1063/1.1134689

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A ’’ruggedized’’ microwave hygrometer which requires no moving parts in the basic measurement method is described. It is designed to measure atmospheric humidity over the vapor pressure range 3–7400 pascals (Pa) (0.03–74 millibar).

ISSN:0034-6748    

DOI:10.1063/1.1134690

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The present paper describes the system configuration of a computerized Auger electron spectrometer, which incorporates various schemes of complicated process control as well as automatic data acquisition, reduction, and retrieval. Central to the system is a sensor‐based computer which controls the spectrometer and interfaces with a host computer where large‐scale computations can be performed. With a graphic terminal as its operator’s station, the system can operate in either automatic or interactive modes. Examples of the process control implemented for the system are given, accompanied by the circuit adaptations necessary for hardware interfacing. Spectral data obtained by the system indicate that the rate of data acquisition has increased by two orders of magnitude with a signal reproducibility of better than 0.5%. Experiments with controlled surface contamination suggest that the spectrometer sensitivity can be doubled by time averaging a number of spectra measured under identical conditions.

ISSN:0034-6748    

DOI:10.1063/1.1134691

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A commercially available CaMoO4tunable acousto‐optic filter has been evaluated for use as a monochromator and modulator for incorporation into a rapid scanning spectrophotometer for the wavelength range 450–750 nm. The construction of a suitable rf driver is described. The bandwidth of light transmitted by the filter was found to be between 2 and 6 A˚, permitting excellent spectral resolution. The contrast ratio was greater than 1400 over the major portion of the tuning range, and the skirt rejection was 35–40 dB for 1‐nm‐wide bands 10–100 nm distant from the center wavelength. The transmission of the filter can be switched in 20 &mgr;sec, and modulation frequencies up to 25 kHz are attainable without appreciable loss of transmission. With a conventional light source the output intensity of monochromatic light is comparable to grating monochromators. Stray light can be effectively compensated for by transmission modulation and phase‐sensitive detection of the output. We show that the use of the filter as a monochromator is in many respects superior to the other devices which have been used previously for rapid scanning. The filter may also be used as a light modulator or multiple‐beam spectrophotometer and, by virture of its electronic control and ease of interfacing with digital computers, can be considered to be a programmable light source.

ISSN:0034-6748    

DOI:10.1063/1.1134681

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

In this schlieren system the probing laser beam is attenuated by a neutral density wedge (instead of the usual knife edge) so that the intensity is proportional to the deflection angle, which in turn is proportional to the density gradient. Time integration of the attenuated probe beam intensity yields the absolute refractive index variation across moving objects. The device is tested by measuring the density jump across a Mach 9 shock wave.

ISSN:0034-6748    

DOI:10.1063/1.1134682

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

We show that the autocorrelation function of an optical signal may be simply obtained using a signal averager and a weighted signal‐averaging technique. The method applies to the measurement of either intensity fluctuations or photocount fluctuations, and we present expressions for the weighted signal average and its error for each case. Finally we test the results experimentally and compare the data with the corresponding theoretical expressions.

ISSN:0034-6748    

DOI:10.1063/1.1134683

出版商:AIP    

年代:1976

数据来源: AIP