Prompt Gamma-Ray Neutron Activation Analysis (PGNAA) offers a non-destructive, relatively rapid on-line method for determination of elemental composition of bulk and other samples. However, PGNAA has an inherently large background. These backgrounds are primarily due to the presence of the neutron excitation source. It also includes neutron activation of the detector and the prompt gamma rays from the structure materials of PGNAA devices. These large backgrounds limit the sensitivity and accuracy of PGNAA. Since Most of the prompt gamma rays from the same element are emitted in coincidence, a possible approach for further improvement is to change the traditional PGNAA detection technique and introduce the gamma-gamma coincidence technique. It is well known that the coincidence technique can eliminate most of the interference backgrounds and improve the signal-to-noise ratio. A new Monte Carlo code CEARCPG is being developed at CEAR to predict coincidence counting in coincidence PGNAA. Compared to the other existing Monte Carlo code, a new algorithm of sampling the prompt gamma rays, which are produced from neutron capture reaction and neutron inelastic scattering reaction, is developed in this work. All the prompt gamma rays are taken into account by using this new algorithm. Before this work, the commonly used method is to interpolate the prompt gamma rays from the pre-calculated gamma-ray table. It works fine for the single spectrum. However it limits the capability to simulate the coincidence spectrum. This new algorithm is to sample the prompt gamma rays from the nucleus scheme. It makes possible to simulate the coincidence spectrum by using Monte Carlo method. The primary nuclear data library used to sample the prompt gamma rays comes from ENSDF library. Three cases are simulated and the simulated results are checked with the experiments. The first case is the prototype for ETI PGNAA application. This case is designed to check the capability of CEARCPG for sing.

The normal prompt gamma-ray neutron activation analysis for either bulk or small beam samples inherently has a small signal-to-noise (S/N) ratio due primarily to the neutron source being present while the sample signal is being obtained. Coincidence counting offers the possibility of greatly reducing or eliminating the noise generated by the neutron source. The present report presents our results to date on implementing the coincidence counting PGNAA approach. We conclude that coincidence PGNAA yields: (1) a larger signal-to-noise (S/N) ratio, (2) more information (and therefore better accuracy) from essentially the same experiment when sophisticated coincidence electronics are used that can yield singles and coincidences simultaneously, and (3) a reduced (one or two orders of magnitude) signal from essentially the same experiment. In future work we will concentrate on: (1) modifying the existing CEARPGS Monte Carlo code to incorporate coincidence counting, (2) obtaining coincidence schemes for 18 or 20 of the common elements in coal and cement, and (3) optimizing the design of a PGNAA coincidence system for the bulk analysis of coal.

Keywords: PGNAA, Coincidence measurement, Monte Carlo, MCNP.

After configuring the proper electronic system to be used, the initial observations of the gamma-gamma coincidence approach were presented. These observations included hydrogen peak elimination, background and sum peak elimination, pulse pile up reduction, and two dimensional spectra. Three practical applications of the coincidence counting approach were presented in this work. The first application was performing elemental analysis for a mixture of radioisotopes using Library Least Squares (LLS). The LLS was applied to the coincidence data as well as the normal single detector data. The coincidence results showed to be much closer to the original activity values of the radioisotopes than the singles. In addition, the coincidence approach greatly reduced the background, summing, and pulse pile up effects. The second application was the two dimensional diagonal summing. The main advantages from this application were improving the peak resolution and greatly reducing the background (Compton Continuum). In addition, it was shown that different diagonal sums can be examined by use of the same set of data from the current electronic system (and software). The two dimensional diagonal summing was used for identifying coincidence schemes and for elemental analysis. The obtained spectra showed to be very promising and could be effectively used for these purposes. The third practical application was using a new NaI detector arrangement. The arrangement was designed to deal with the problem of the low detection probability of the high energy gamma rays of interest in the oil well logging industry. This arrangement consisted of two NaI detectors, one of which was a well type. The detectors were designed to fit in each other. Coincidence data were collected using this new arrangement. The results show that this new arrangement enhances the count rate in the coincidence data, thus increasing the Signal to Noise Ratio, as opposed to two separate detector setups. Finally, a Monte.

Prompt gamma activation analysis (PGAA) is a unique, non-destructive nuclear analytical method with multi-element capabilities. It is most effective if intense neutron beams (especially cold beams) of nuclear reactors are used to induce the prompt gamma radiation. Based largely on the authors' pioneering research in cold neutron PGAA, the handbook describes the methodology in self-contained manner and reviews recent applications. The library of prompt gamma ray data and spectra for all natural elements is a unique aid to the practitioner. The level is understandable by a broad audience, which facilitates teaching and training. The Handbook of Prompt Gamma Activation Analysis is a comprehensive handbook written for those practising the method, wanting to implement it at a reactor facility, or just looking for a powerful non-destructive method of element analysis. The book is also useful for nuclear physics, chemistry and engineering scientists, scholars and graduate students interested in neutron-induced gamma ray spectroscopy and nuclear analytical methods.