The time-domain automatic network analyser (TDANA) is described. It utilizes time-domain measurements and the fast Fourier transform to obtain frequency-domain scattering parameters. A TDANA consists of a pulse generator, sampling oscilloscope, and a minicomputer. The present state of the art for TDANA's includes frequency coverage from dc to 18 GHz in a single instrument and complex scattering parameter measurement uncertainties of the order of 1 percent.

Automatic network measurements in the time domain

Time response of plastic scintillators

A calibration technique for a time domain reflectometry and transmission (TDR and TDT) measurement system as applied to network analysis is presented. The calibration corrects for the errors caused by the response of the measurement system. A complete physically-based model is established for the system. A set of calculable standards is developed to satisfy the time domain requirements for calibration. The calibration technique was applied to determining the model parameters of a commercial TDR and TDT system. The calibration enhanced the system bandwidth from 8 GHz to about 20 GHz. Experimental verification is given to demonstrate the validity and accuracy of the calibration technique. >

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Calibration of time domain network analyzers

Radiation pulses 50 ps in duration have been attained at the EG&G/AEC electron linear accelerator by isolation of individual microstructure groups of electrons which normally occur at the fundamental accelerating frequency. Pulse compression by means of velocity modulation techniques has been used to increase the intensity of these pulses from 0.02 nC to 1.5 nC per pulse, or 30 A for the 50-ps pulse length. The injector pulse is synchronized to the RF acceleration frequency with a precision of 30 ps, which results in pulse-to-pulse reproducibility to within a few percent, permitting recurring pulse measurements to be made with sampling oscilloscopes. These intense short bursts of radiation allow the study of radiation detectors, scintillators, and chemical systems in the subnanosecond time domain. Neutron time-of-flight measurements with a total resolution of 400-500 ps have also been demonstrated. The calculated charge enhancement resulting from velocity-modulation bunching is compared to measured performance, and the system is described in detail.

Velocity Modulation System for Enhancement of 50 Picosecond Radiation Pulse

Properties of four types of microchannel plate photomultipliers have been studied, with emphasis on applications to plasma diagnostic experiments. Detector pulse shapes, peak linear currents, pulse rate effects, and ionic feedback effects have been documented. Minimum FWHM of 210 ps was observed. Peak linear currents up to 11 A were documented.

Characterization of Microchannel Plate Photomultipliers for Plasma Diagnostics

The 30-A, 50-ps electron pulse generated by the EG&G/AEC linear accelerator permits the measurement of scintillator response functions and the study of other subnanosecond phenomena. To take advantage of this capability, a system for fast pulse monitoring has been developed. Faraday cups and nonintercepting monitors have been designed to measure the electron beam current, and are used in conjunction with a unique data-acquisition system for fast pulse measurements. This system uses the fastest available sampling oscilloscopes, modified for remote operation of the sampling elements, thus eliminating the signal distortion of the coaxial cable between the experimental measurement point and the data-recording area. The digitized output of the sampling oscilloscope is stored in a magnetic memory and repeatedly averaged to increase the signal-to-noise ratio, allowing the measurement of signals that are approximately 100 ps in duration and a few millivolts in amplitude. The digital information, recorded on either magnetic or paper tape, is compatible with computerized data-reduction techniques. This data-acquisition system may be used on any recurring fast pulse and offers a sensitivity-bandwidth improvement of about 105 over the best traveling-wave oscilloscopes.

https://epaper.kek.jp/p69/pdf/pac1969_0927.pdf

R. K. Hanst

Papers

Picosecond Beam Monitors and Data-Acquisition System