Sharif Digital Repository

In this paper, the development of the MCNPX-ESUT (MCNPX-Energy Engineering of Sharif University of Technology) computer code for simulation of neutron/gamma pulse height distribution is reported. Since liquid organic scintillators like NE-213 are well suited and routinely used for spectrometry in mixed neutron/gamma fields, this type of detectors is selected for simulation in the present study. The proposed algorithm for simulation includes four main steps. The first step is the modeling of the neutron/gamma particle transport and their interactions with the materials in the environment and detector volume. In the second step, the number of scintillation photons due to charged particles such... 

Considering the results of baryonic compact massive objects searches through microlensing [1], cool molecular hydrogen (H2 - He) clouds should now be seriously considered as a possible major component of the Galactic hidden matter. It has been suggested that a hierarchical structure of cold H 2 could fill the Galactic thick disk [8] or halo [3], providing a solution for the Galactic hidden matter problem. This gas should form transparent "clumpuscules" of ∼ 10 AU size, with a column density of 1024-25cm-2, and a surface filling factor smaller than 1%. The OSER project (Optical Scintillation by Extraterrestrial Refractors) is proposed to search for scintillation of extra-galactic sources... 

A new air shower experiment of the Alborz Observatory, Alborz-I, located at the Sharif University of Technology, Iran, will be constructed in near future. An area of about 30×40 m2 will be covered by 20 plastic scintillation detectors (each with an area of 50×50 cm2). A series of experiments have been performed to optimize the height of light enclosures of the detectors for this array and the results have been compared to an extended code simulation of these detectors. Operational parameters of the detector obtained by this code are cross checked by the Geant4 simulation. There is a good agreement between the extended-code and Geant4 simulations. We also present further discussions on the... 

In this paper, a novel idea is developed to construct energy spectrum of inorganic scintillator detector (e.g. NaI(Tl)) using energy spectrum of organic scintillator detector (e.g. NE102) by means of a model-free method. For this purpose, support vector machine (SVM) accompanied with different kernel functions (i.e. linear, polynomial, and Gaussian) is applied. The spectra of NE102 and NaI(Tl) detectors of the single radioisotopes (i.e. Co60, Cs137, Na22, and Am241) are utilized for training of SVM. In other words, data of NE102 detector are input spectrums of training patterns and data of NaI(Tl) detector are target spectrums of training patterns. To construct an appropriate mapping... 

Wax deposition inside pipelines is a major concern in oil and gas industries, and it must be continuously monitored. In this paper, a mathematical-experimental combined method based on the Compton scattering was proposed to determine the thickness of the wax deposited inside the industrial pipes. For this purpose, first, the relationship between the intensity of the backscattered gamma-rays and the thickness of the wax inside the pipe was mathematically modeled. Then, an experimental setup was prepared for measuring the intensity of the backscattered gamma-rays from the pipes with different wall thicknesses and different wax widths. Finally, the experimentally measured counts were used by... 

An array including five scintillation detectors at Sharif University of Technology in Tehran (35°43′N, 51°20′E, 1200m a.s.l= 897 gcm−2), over a year from October 2016 to October 2017, collected more than 5.6×105 extensive air shower (EAS) events in the energy range between 0.03PeV and 3PeV. Data from the array were used to examine the cosmic ray shadow of the Moon in the energy range mentioned. The observation of a deficit of cosmic rays in the direction of the moon can be an estimate of the accuracy of the measurement of the primary particles of the air showers. The deficit of cosmic rays from the direction of the moon, in fact, is due to the presence of the moon in the early direction of... 

As a primary step of establishment of an extensive air shower array consisting 20 scintillation detectors we optimized an individual detector. Square shaped scintillators are placed under a metal pyramid Light Enclosure with a photomultiplier tube (PMT) at the vertex of it. A set of experiments are performed to optimize the height of light enclosures by comparing 4 different heights 0.1, 0.2, 0.3 and 0.4 m. These experiments are supported by a Monte Carlo simulation of detection process. In this article, by considering experimental and simulation results we concluded that 20 cm is an optimum height for light enclosures  

The response function of NE102 plastic scintillator to gamma rays has been simulated using a joint FLUKA+PHOTRACK Monte Carlo code. The multi-purpose particle transport code, FLUKA, has been responsible for gamma transport whilst the light transport code, PHOTRACK, has simulated the transport of scintillation photons through scintillator and lightguide. The simulation results of plastic scintillator with/without light guides of different surface coverings have been successfully verified with experiments  

In the present paper, the light output distribution due to poly-energetic neutron/gamma (neutron or gamma) source was calculated using the developed MCNPX-ESUT-PE (MCNPX-Energy engineering of Sharif University of Technology-Poly Energetic version) computational code. The simulation of light output distribution includes the modeling of the particle transport, the calculation of scintillation photons induced by charged particles, simulation of the scintillation photon transport and considering the light resolution obtained from the experiment. The developed computational code is able to simulate the light output distribution due to any neutron/gamma source. In the experimental step of the... 

The motivation of this study is development of a technique to construct energy spectrum of higher price/high resolution detectors (e.g. NaI (Tl)) using spectrum of lower price/low resolution detectors (e.g. NE102). Since there is no explicit mathematical model between these type of detectors (i.e. organic and inorganic scintillator detectors), it is necessary to utilize model-free methods. Construction of mapping function to generate spectrum of inorganic scintillator using spectrum of organic scintillator can be done by supervised model-free methods. Different supervised learning methods including localized neural networks, statistical methods, feed-forward neural networks, and conditional... 

Aims. Stars twinkle because their light propagates through the atmosphere. The same phenomenon is expected on a longer time scale when the light of remote stars crosses an interstellar turbulent molecular cloud, but it has never been observed at optical wavelengths. The aim of the study described in this paper is to fully simulate the scintillation process, starting from the molecular cloud description as a fractal object, ending with the simulations of fluctuating stellar light curves. Methods. Fast Fourier transforms are first used to simulate fractal clouds. Then, the illumination pattern resulting from the crossing of background star light through these refractive clouds is calculated... 

Aims. Stars twinkle because their light propagates through the atmosphere. The same phenomenon is expected at a longer time scale when the light of remote stars crosses an interstellar molecular cloud, but it has never been observed at optical wavelength. In a favorable case, the light of a background star can be subject to stochastic fluctuations on the order of a few percent at a characteristic time scale of a few minutes. Our ultimate aim is to discover or exclude these scintillation effects to estimate the contribution of molecular hydrogen to the Galactic baryonic hidden mass. This feasibility study is a pathfinder toward an observational strategy to search for scintillation, probing... 

In this report we outline the study of the development of calorimeter detectors using bright scintillating crystals. We discuss how timing information with a precision of a few tens of pico seconds and below can significantly improve the reconstruction of the physics events under challenging high pileup conditions to be faced at the High-Luminosity LHC or a future hadron collider. The particular challenge in measuring the time of arrival of a high energy photon lies in the stochastic component of the distance of initial conversion and the size of the electromagnetic shower. We present studies and measurements from test beams for calorimeter based timing measurements to explore the ultimate... 

A new small array of cherenkov detectors has been deployed in Tehran, 1200 m above sea level. This array contains of four tanks full of distilled water with diameter of 64 cm and height of 130 cm. The effective area of each tank is about 6.5 × 103cm2 . They are used to detect the air showers and to record the arrival time of the secondary particles. We have collected about 486643 EAS in 5270 h of observation time from Nov-2006 to May-2007. We find zenith and azimuth distribution of EAS with this array. A cosn θ distribution with n = 7.3±0.1 was obtained for zenith angle. Since this tank of distilled water is cheaper and more available than Scintillators it is preferable to use them instead... 

This paper presents the developed computer codes based on the Adaptive Group of Ink Drop Spread (AGIDS) algorithm [1] for the reconstruction of the energy spectrum of the neutron source. The required data are generated via simulation of the neutron pulse height distributions due to randomly generated energy spectra with the MCNPX-ESUT computer code [2]. The simulated neutron pulse height distributions and corresponding randomly generated energy spectra are the input and output data of the developed computer code, respectively. As a case study, the 241Am-9Be neutron source is studied and the simulation of the neutron pulse height distribution of the NE-213 liquid organic scintillator is...