摘要:

A double ion chamber can be used to measure absolute intensities of UV light, and the absorptivity and photoionization yield of gases. New methods have been developed and tested which make double ion chambers simpler to build and use. These methods allow for collection regions of unequal length and for a body of absorbing gas in front of the chamber. Such methods make it possible to mount the chamber away from the source of ionizing UV light without displacing other experiments. The methods described use the relationship between the outputs of a chamber of nominal dimensions, over a range of gas pressures, to obtain information about the light and the gas in the chamber and the effective dimensions of the chamber. Some errors due to pressure fluctuations and uncertainties in the construction of the chamber are avoided by these methods.

ISSN:0034-6748    

DOI:10.1063/1.1139704

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A dc strain‐gauge bridge amplifier configuration with automatic compensation of thermal drift using common operational amplifiers is presented. The amplifier operation is divided into two steps: one of auto‐zeroing and other of amplification of the input signal. The zeroing of the input signal is achieved by switching the bridge excitation to zero periodically at a frequency of about 100 Hz, thus limiting the maximum frequency of the input signal to about 8 Hz. With a gain of 5000, the output voltage drift of the amplifier is measured to be about 1 mV for a temperature change of 40 °C.

ISSN:0034-6748    

DOI:10.1063/1.1139705

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The response characteristics of a two‐stage CuSO4solution ‘‘tube’’ resistive divider placed in another CuSO4solution ‘‘tube’’ in a concentric cylindrical configuration for measuring high‐voltage nanosecond pulses have been studied. The test results showed that it was capable of maintaining pulse rise time less than 10 ns, and the hold‐off voltage for pulses with rise times less than 10 ns was 600 kV.

ISSN:0034-6748    

DOI:10.1063/1.1139706

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A simple, flexible, and relatively inexpensive microcomputer‐controlled shutter system intended, principally, for use with molecular‐beam epitaxial reactors is described. Eight pneumatic shutters, each one controlling the molecular‐beam emission of a corresponding effusion cell, can be operated in any combination simultaneously or sequentially. Such a system has been built and is being used to grow heterojunction and superlattice structures of binary and ternary III‐V alloys.

ISSN:0034-6748    

DOI:10.1063/1.1139707

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A low‐cost electronic controller for motorized micrometers has been developed. The circuit provides a variable off period at the end of the micrometer travel and is intended for applications where high reliability over many traverses, but not necessarily precise positioning, is required. Two methods of triggering the controller are described, one using mechanical switching, the other optical switching.

ISSN:0034-6748    

DOI:10.1063/1.1139708

出版商:AIP    

年代:1988

数据来源: AIP