Nuclear science Research Papers - Academia.edu (original) (raw)

We report on the development of the front-end electronics for rat conscious animal positron emission tomography (RatCAP), a portable and miniature positron emission tomography scanner. The application-specific integrated circuit (ASIC) is... more

We report on the development of the front-end electronics for rat conscious animal positron emission tomography (RatCAP), a portable and miniature positron emission tomography scanner. The application-specific integrated circuit (ASIC) is realized in a complementary metal-oxide-semiconductor 0.18 μm technology and is composed of 32 channels of charge sensitive preamplifier, third-order semi-Gaussian bipolar shaper, timing discriminator with independent channel adjustable threshold, and a 32-line address serial encoder to minimize the number of interconnections between the camera and the data acquisition system. Each chip has a maximum power dissipation of 125 mW. A mathematical model of the timing resolution as a function of the noise and slope at the discrimination point as well as the photoelectron statistics was developed and validated. So far, three ASIC prototypes implementing part of the electronics were sent to fabrication. Results from the characterization of the first two prototypes are presented and discussed.

The activity concentrations of 226 Ra, 232 Th, and 40 K from 102 building materials samples were determined using a high-purity germanium (HPGe) detector. The activity concentrations were evaluated for possible radiological hazards to the... more

The activity concentrations of 226 Ra, 232 Th, and 40 K from 102 building materials samples were determined using a high-purity germanium (HPGe) detector. The activity concentrations were evaluated for possible radiological hazards to the human health. The excess lifetime cancer risks (ELCR) were also estimated, and the average values were recorded as 0.42 ± 0.24 Â 10 À3 , 3.22 ± 1.83 Â 10 À3 , and 3.65 ± 1.85 Â 10 À3 for outdoor, indoor, and total ELCR respectively. The activity concentrations were further subjected to RESRAD-BUILD computer code to evaluate the long-term radiation exposure to a dweller. The indoor doses were assessed from zero up to 70 years. The simulation results were 92 ± 59, 689 ± 566, and 782 ± 569 mSv y À1 for indoor external, internal, and total effective dose equivalent (TEDE) respectively. The results reported were all below the recommended maximum values. Therefore, the radiological hazards attributed to building materials under study are negligible.

Proccedings of the International Symposium on Solid State Dosimetry, Volume 3. 2016

This research reports the annual effective dose of dwellers based on the finding of natural radioactivity concentrations in Malaysian tiles. A total of 30 tiles samples obtained from the manufacturer or bought directly from local hardware... more

This research reports the annual effective dose of dwellers based on the finding of natural radioactivity concentrations in Malaysian tiles. A total of 30 tiles samples obtained from the manufacturer or bought directly from local hardware store. Natural radioactivity was analyzed using gamma spectrometry system for 12 h counting times. The activity concentration of 226 Ra, 232 Th, and 40 K in the analyzed samples ranged from 37.50-158.05 Bq kg-1 , 42.22-80.19 Bq kg-1 and 349.46-750.18 Bq kg-1 , respectively. The determined radium equivalent activity was below than the recommended limit of 370 Bq kg-1. The external dose received by dwellers due to natural radionuclides in tiles were projected for 1, 5, 10, 20 and 50 years through six exposure pathways using Resrad-build computer code. The results showed that the annual effective dose received by dwellers increased for the investigated timelines but still lower than the annual recommended limit of 1500 µSv. The simulation result also indicates that radon gas was the primary radiation exposure which contributes 80-94 % from the total radiation exposure to dwellers.

Seismic noise limits Earth based gravitational wave interferometric detectors at low frequencies. The detection threshold can be lowered down to a few Hz using a seismic attenuation system based on Inverted Pendulum (IP) which sustains... more

Seismic noise limits Earth based gravitational wave interferometric detectors at low frequencies. The detection threshold can be lowered down to a few Hz using a seismic attenuation system based on Inverted Pendulum (IP) which sustains interferometer optical components by means of a pendula chain. The IP, acting as a mechanical low pass filter, is able to filter out seismic noise and at the same time it provides a quasi-inertial stage where the suspension point of the pendula chain lies. The IP is a three degrees of freedom system, it has two translational and one rotational modes. Therefore, to fully determinate its position, three independent sensors are mounted at the periphery of the IP top table. For the same reason, three independent actuators are used to move the IP. The geometrical position of the sensors is different from actuator positions, in addition, both of them are not connected to the normal modes of the IP. Each sensor will be sensitive in all the three IP normal modes and each actuator will generate movements which are a mix of the three modes. To take advantage of controlling a SISO (Single Input Single Output) system instead of a MIMO (Multiple Input Multiple Output) system, a diagonalization of the actuation and detection system is needed. An original and model independent experimental procedure for determining the system dynamic, giving an effective diagonalization has been developed and tested.

We present a model to describe the origin of non-proportional dependence of scintillator light yield on the energy of an ionizing particle. The non-proportionality is discussed in terms of energy relaxation channels and their linear and... more

We present a model to describe the origin of non-proportional dependence of scintillator light yield on the energy of an ionizing particle. The non-proportionality is discussed in terms of energy relaxation channels and their linear and non-linear dependences on the deposited energy. In this approach, the scintillation response is described as a function of the deposited energy deposition and the kinetic rates of each relaxation channel. This mathematical framework allows both a qualitative interpretation and a quantitative fitting representation of scintillation non-proportionality response as function of kinetic rates. This method was successfully applied to thallium doped sodium iodide measured with SLYNCI, a new facility using the Compton coincidence technique. Finally, attention is given to the physical meaning of the dominant relaxation channels, and to the potential causes responsible for the scintillation non-proportionality. We find that thallium doped sodium iodide behaves...