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  • Author or Editor: M. Koskelo x
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Abstract  

The pileup loss from the peak area and peak shape distortion effects are of considerable importance in routine activation analysis where the count rate may vary considerably from one sample to another. In this paper simple linear approximations for the peak shape change and efficiency loss have been used to show that correct results to within 2% are obtainable in the range 1000 cps to 10 000 cps.

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Abstract  

This work discusses the relative merits of parabolic, linear, or step background functions under the photopeak in a SAMPO type fitting algorithm used in the Canberra APOGEE package for a PDP-11 or a VAX-11 minicomputer. Four different variations of the background are subjected to a statistical test of precision under stable measurement conditions and investigated for their behavior as a function of count rate.

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Abstract  

The newly revised ANSI N42.141.2 has provided analysis software developers with a set of well defined, consistent and unbiased procedures designed to evaluate the accuracy and limitations of peak search and peak area analysis programs. This work uses two of the procedures outlined in this standard to evaluate five peak analysis algorithms currently in use in Canberra and Nuclear Data software packages. The first procedure examines a program's behavior as the centroid separation and peak height ratio of a doublet are varied. A previous review of these data3 demonstrated significant peak area inaccuracies at peak separations at or below 1.5 FWHM. We will discuss improvements made to some of these programs and the impact on the doublet results. The second procedure examines a program's behavior as the Compton continuum beneath a fixed peak area is increased. For the same five algorithms we will discuss the dependence of peak area on Compton continuum and also explore the limits of peak detectability.

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Abstract  

In this work we demonstrate that the latest addition to the Canberra/Nuclear Data family of software packages, Genie-PC, performs as well as or better than the older software packages with respect to the doublet tests reported on earlier. In addition, we demonstrate the behavior of the various software packages for a doublet which includes the 511 keV annihilation line. And we show that using other means to break a doublet into its component areas will also lead to accurate overall results.

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Abstract  

To achieve the highest possible sensitivity of analysis for environmental samples it is common practice to use both a high efficiency detector and a close measurement geometry with a large sample size (e.g. Marinelli beaker). Under such conditions, the typical efficiency calibration procedure results in a biased activity value for many nuclides due to the true coincidence summing effect. While there are a few methods to correct for this effect with special calibration standards, such calibrations can be both time consuming and expensive. Due to these calibration difficulties, the true coincidence summing effect is often simply ignored. Recently, it has been demonstrated that the coincidence summing correction can be performed mathematically even for voluminous sources. This new method consists of an integration of the coincidence correction factor over the sample volume while taking into account its chemical composition and the container. In this paper, we will discuss the latest approaches for establishing the peak efficiency and peak-to-total efficiency curves, which are required for this method. These approaches have been tested for HPGe detectors of two different relative efficiencies.

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Abstract  

The American National Standard "Calibration and Use of Germanium Spectrometers for the Measurement of Gamma-Ray Emission Rates of Radionuclides" has been reissued as N42.14-1999. The performance tests in it can be used to make sure that a gamma-spectroscopy program is set up correctly. The same tests can also be used to verify the improvements made by program developers. However, sometimes the tests in this ANSI standard are not enough. To satisfy certain quality assurance requirements, it is necessary to demonstrate that the results are correct either by hand calculations or by comparing the results to known values.

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Abstract  

We have shown that it is sufficiently accurate to use the MCNP peak-to-total calibration results to correct for cascade summing effects in a gamma-spectrum. Also, it is sufficient to use only approximate detector characterization data with empirical peak-to-total to obtain good cascade summing correction results. The intrinsic P/T-curve for detectors with the same efficiency is very similar and it may be considered a common characteristic of the whole detector's family with given efficiency.

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Abstract  

Decommissioning and decontamination work, safeguards related measurements for special nuclear materials, and many other in-situ applications require that the measuring system be taken to the sample and not the other way around. In addition to a portable detector, these types of measurements need a lightweight, rugged, battery operated MCA. Canberra's solution to this need is the versatile InSpector Multi-Channel Analyzer. This single instrument includes the MCA memory management, a high voltage power supply for either a NaI or a Ge detector, a spectroscopy grade amplifier, a digital stabilizer, and an ADC. It has a total weight of 3,2 kg, including batteries.

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Abstract  

Various in-situ gamma-spectroscopy applications need a versatile, multi-purpose, portable multi-channel analyzer (MCA). Recently, Canberra has introduced the Inspector-2000 for this purpose. It uses digital signal processing (DSP) technology and weighs only about 1.2 kg. It also supports CdTe, NaI and Ge detectors. Due to its use of DSP technology, the Inspector-2000 also provides a longer battery life, a better detector resolution and a better temperature stability than most portable MCAs. This paper includes a short description of the Inspector-2000 MCA and its performance characteristics compared to an analog MCA.

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Abstract  

The Idaho National Engineering Laboratory (INEL) has been developing a dual energy pulser for dead time and random summing corrections, and for the assessment of the quality of the data for many years. This effort now includes several revisions of the original concept. Recently, Canberra has developed a version of this dual energy pulser as part of a technology transfer from INEL to Canberra Industries. This new design includes many of the same characteristics as the original INEL design. In this paper, we will present the results of a series of tests performed at NIEL with both the latest INEL pulser design and the Canberra design. These test results include measurement results of pulser peak width, energy equivalence and dead time and random summing correction capability as a function of count rate and temperature. It is demonstrated that both designs perform comparably with count rate and temperature when operated over a limited temperature range. In applications where extreme temperature variations are likely during the measurements, the INEL design is the better choice.

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