scope:

Foreword

This standard describes test procedures for amplifiers and preamplifiers that are used with semiconductor, scintillation, and proportional detectors in the spectrometry of ionizing radiation. It supersedes ANSI/IEEE Std 301-1976, IEEE Standard Test Procedures for Amplifiers and Preamplifiers for Semiconductor Radiation Detectors for Ionizing Radiation. The title was changed because the same amplifiers used for semiconductor detectors are applicable to other types.

Amplifier technology has progressed to the point where the spectrometer performance may be limited as much by the multichannel analyzer (MCA) as by the amplifier. Because of this and because of the impracticality of standardizing on one MCA with so many on the market, MCAs, with minor exceptions, are not a part of the measurement procedure in this publication.

In this standard, measuring procedures are given in greater detail than in the earlier publication because with modern amplifiers, perceived performance often depends on the details of measurement. Thus, many of the details of the procedures must be standardized as well as the amplifier specifications.

Tests that are specific to amplifiers with time-variant pulse-shaping filters are not included in this standard, nor are tests for pile-up rejectors. Time-variant filters allow shorter pulse-shaping times than linear filters for the same signal-tonoise ratio (snr), and pile-up rejectors, as the name implies, block pulses that overlap earlier ones, allowing higher count rates for a given spectral-line resolution. Both techniques have the greatest application at the energy extremes: at very low energies because wide pulses must be used to optimize the snr, and at high energies where detector artifacts cause low-side tailing of spectrum lines. The tailing obscures low-intensity lines falling just below higher energy lines, and pile-up causes phantom peaks to appear at energy multiples of the spectrum lines.

In this standard, t_0.5 or t_1/2 (the pulse width at 50% of peak amplitude) is the main-amplifier indicator of shaping time because this parameter best enables a performance comparison among different amplifiers. Also, compared with other parameters, this one is the easiest to measure accurately with an oscilloscope and pulse generator.

Companions to this document are ANSI/IEEE Std 300-1988 [1],¹ ANSI/IEEE Std 325-1986 [2], and IEEE Std 194-1977 [3].

Scope and Object 

These test procedures cover amplifier and preamplifier systems with linear pulse-shaping networks for use with semiconductor, scintillation, and proportional detectors in the spectroscopy of ionizing radiation. The object is to provide a common language and methodology for users and manufacturers of pulse-amplifier systems.

This standard supersedes IEEE Std 301-1976, IEEE Standard Test Procedures for Amplifiers and Preamplifiers for Semiconductor Radiation Detectors for Ionizing Radiation. Test procedures for associated detectors are described in ANSI/IEEE Std 300-1988 [1] and ANSI/IEEE Std 325-1986 [2]. IEEE Std 194-1977 [3] is a companion document for pulse-shape terminology.

Not all of the tests described herein are mandatory, but those that are performed to determine preamplifier and amplifier specifications shall conform to this standard.

The emphasis on the methods of measurement is to enhance sensitivity and improve accuracy by working around the limitations of the test instruments, particularly oscilloscopes that have only a visual display for readout. A null technique is used where possible, thereby reducing basic errors to the inaccuracy of a pair of precision resistors. When use of a bridge is inappropriate, such as in measurements of pulse height with an oscilloscope, the pulse is made to occupy a fixed amplitude and vertical position on the face of the cathode-ray tube (CRT). Some measurements require test instruments or fixtures not commercially available at this writing; circuit diagrams for their construction are given in the Appendix. It is not acceptable to make use of a standard nuclear instrument module to test the performance of an amplifier unless the errors introduced by that module can be corrected for or shown to be less than the error caused by the amplifier. Examples are the use of a crossover-pickoff module to measure crossover walk in a bipolar amplifier, and an MCA to measure nonlinearity and noise.