摘要:

An improved double Michelson laser interferometer dilatometer is described. The unit is suitable for the study of materials of arbitrary size or shape with time‐dependent and near zero coefficients of thermal expansion (CTE) over the range 100 to >450 K. Direct recording of four amplified photodetector signals gives a &Dgr;L/Lresolution of 5×10−8and an average CTE error in the 10−10–10−9K−1range. An inexpensive automatic digital counter–microprocessor combination permits recording of instantaneous &Dgr;L/Land CTE values at >30‐s intervals. The resolution of &Dgr;L/Lin this case is <8×10−7while the instantaneous CTE (4 K interval) has an uncertainty of <2×10−7K−1. The latter values are based on a counting unit of &lgr;/2 and interpolating. Smaller counting units reduce errors proportionately to the system noise level and the limitations of the temperature measurement.

ISSN:0034-6748    

DOI:10.1063/1.1137997

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Exit positions and velocities of charged particles passing through an electrostatic spherical analyzer were generated by a computer program which utilizes transformations to the trajectory plane of the particle to obtain an exact solution in the central force field of the analyzer. Entrance and exit planes were treated as a potential jump to zero potential, thus simulating grounded wire meshes at the entrance and exit. It was found that particle input energies could be determined as a function of exit position. A wide variety of designs were tried, varying plate radii, plate voltages, and incoming collimation of the particles. A power‐law relationship between exit radius and input energy was found for designs in which the mean radial position between the plates corresponded to zero potential. However, the total input energy spread &Dgr;Eof the particles passed by an analyzer could never be made to approach twice the mean input energyEof the particles passed. Since a parabolic analyzer can be made to have a &Dgr;E/E=1.92, we conclude that the parabolic analyzer makes a better spectrograph.

ISSN:0034-6748    

DOI:10.1063/1.1137998

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The output energy spread of a microchannel plate has been studied experimentally in a wide range of operating conditions. The energy distribution is found to consist of a sharp main peak with the full width at half‐maximum of a few electron volts and a long tail extending over a wide energy range. These two components are presumably caused by two distinct regions of the potential distribution near the output end produced by the electrode penetrating into a certain depth within the microchannels. The tail component shows a significant change, particularly in the unsaturated operation mode. The resultant variation in the relative number of high‐energy output electrons may have a detrimental effect on the spatial resolution of the image intensifier.

ISSN:0034-6748    

DOI:10.1063/1.1137999

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A simplified model is presented to explain the gain characteristics of a microchannel plate (MCP) operated in the reflection mode for detecting low‐energy positive ions. Analysis, taking into account an automatic preacceleration effect of the potential applied across a MCP on incident ions penetrating into the microchannels, can lead to high gain performance in this operation mode. The resultant calculated gain‐applied potential and gain‐incident ion energy curves fit well to the data reported previously. It is also shown that the gain is almost entirely determined by the transmissibility of incident ions through the microchannels toward the backplate.

ISSN:0034-6748    

DOI:10.1063/1.1138000

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

In this paper the authors describe the construction and the operation of a scintillator hodoscope used in an intense beam. By using a fast scintillator (Pilot U), an XP1910 photomultiplier, and an appropriate electronic chain, a two‐pulse separation of 6 ns per channel and a time resolution (&sgr;) of 210 ps were obtained.

ISSN:0034-6748    

DOI:10.1063/1.1138001

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A new apparatus for production of artificial compositionally modulated materials is presented. It consists of an ion gun that sputters from alternating targets on a rotating assembly, the position of which is controlled by a thickness monitoring crystal. The apparatus is simple, relatively inexpensive, and flexible, in that it allows deposition of metals, semiconductors, and insulators under the same conditions.

ISSN:0034-6748    

DOI:10.1063/1.1138511

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

We have produced single ultrathin Pt wires with diameters as small as 80 A˚, using an extension of the Wollaston composite drawing process. These wires were used in experiments to test the theory of quasi‐one‐dimensional electronic localization and interaction effects at liquid‐helium temperatures. The procedures developed to draw composite wires and remove the outer jacket are described in detail.

ISSN:0034-6748    

DOI:10.1063/1.1138002

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A simple and inexpensive cold stage developed for use with the Cameca IMS‐3fion microscope is described. It is easy to use, and temperatures near to that of liquid nitrogen are obtained. Data are presented showing the first analysis of frozen hydrated biological samples with the ion microscope.

ISSN:0034-6748    

DOI:10.1063/1.1138003

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A cw dye laser was automatically tuned as wide as 100 cm−1with a very simple control system while retaining a narrow spectral width of 15 MHz. This wide scanning was accomplished by repetitive 5‐cm−1sweeps of both the laser cavity and an internal e´talon along with a continuous tuning of a birefringent filter. Mode jumps were prevented by locking the cavity to the internal e´talon by a novel type of integrating servoamplifier which has an auto‐reset function. This scan system proved very useful for a wide‐ranged spectral measurement of the Doppler‐limited resolution. The jumpless scanning with a constant rotational speed of the birefringent filter is extendable up to 230 cm−1at around 1.7×104cm−1.

ISSN:0034-6748    

DOI:10.1063/1.1138484

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A spectral‐streak equalizer was developed for use with an electronic streak camera to correct for material dispersion in optical fibers. Material dispersion occurs because different wavelengths of light travel at different speeds through glass fibers; the resulting difference in transit times broadens light pulses, which can lead to errors in certain scientific applications. This new instrument combines optical equalization and streak equalization techniques; it uses an array of optical fibers, as in the optical equalization technique, to partially compensate for the dispersion and uses the streak camera dynamics, as in the streak equalization technique, to complete the compensation. This paper examines the principles of equalization and compares several techniques, enumerates general and specific design considerations, outlines the calibration procedure, details efficiency estimates, describes testing techniques, gives calibration data and test results for spectral‐streak equalizers currently in use, and draws conclusions from recent experience with these devices.

ISSN:0034-6748    

DOI:10.1063/1.1138485

出版商:AIP    

年代:1985

数据来源: AIP