In the last decade, several studies have concluded that elevated concentrations of radon gas in soil or groundwater could be the sign of an imminent earthquake. It is believed that in case of sudden movement of rocks before earthquake, radon is released from the depth of ground and reached the surface. In this way, by measuring Radon concentration change, earthquake prediction is possible. In this study, for the purpose of the feasibility of using microstrip gas detector in monitoring Radon change, initially for the verification of the code, the range of radon alpha particles and its progeny in the air has been obtained in the standard condition, which is consistent with the experimental results. Then detector geometry has been simulated by MCNPX code and after examining the average of detector response to decay, the output code is calibrated considering the information about the radon changes in Jowshan hot spring. The results have shown that the detector response is comparable to the experimental data and can be used as an earthquake pre-indicator.

In gas detectors with UV absorbing gas mixture, the Self-Quenched Streamer (SQS) mode can be achieved following the proportional mode, which leads to appear the light column. In this study, the design, simulation and construction of three micro pattern gas-detector, THGEM, with different geometric dimensions are presented. Moreover, the ability of operation in SQS mode to determine incident rays position without using any conventional imaging system is investigated. In the presence of UV absorbing gas mixtures, the proportional mode of the gas detector operation is followed by SQS mode as soon as the visible light column appears at the ray entrance location. In the employed method, each THGEM hole as an image pixel can operate in the SQS mode with emerging a light column, independent of other holes. As a consequence, it can be used for alpha beam detection since the brightness of each hole at a certain voltage is proportional to the number of primary electrons entered the hole.

In this paper, we have designed an all-optical controllable gas detector by doping 3-level Λ type nanocrystals in the moving arms' mirror of Michelson interferometer and used electromagnetically induced transparency (EIT) phenomenon to change its refractive index. By this means, we have created a controllable phase difference between light beams in two arms of the Michelson interferometer, where reflection phase of the EIT-based mirror changes about p radiant. Also, the signal reflection from EIT-based mirror changes between 0% and 100% approximately, while the second arm's signal is reflected completely. This EIT-based mirror's refractive index change can be a good alternative for conventional Michelson interferometer-based gas detector with one mechanical moving arm mirror (Undergraduate Instrumental Analysis, 6th edn. Marcel Dekker, New York, 2005), where long response time and unfix moving speed were its main drawbacks. While, in this scheme, not only these disadvantages are removed but also the response time can reach the electron transient time between the atomic energy levels. Then, by this all-optical tunable gas detector, we have achieved many modifications such as response time in sub-nanoseconds, high resolution, and high accuracy, or less cross sensitivity to other gas species.

In this study, a computational technique is used to investigate the ability of a new Micro Electro-Mechanical System (MEMS) gas actuator Microscale In-plane Knudsen Radiometric Actuator (MIKRA) for detecting and sensing gas mixture. In this actuator, the temperature difference of two arms in a rectangular domain in a rarefied condition induces a Knudsen force which is associated with physical properties of the gas. Both 2D and 3D approaches were applied to simulating the ow inside the model. In order to de ne the ow feature of low-pressure gas inside the micro gas actuator, a high-order equation of Boltzmann should be solved to attain reliable results. Since the domain of this micro gas is non-equilibrium, Direct Simulation Monte Carlo (DSMC) method was applied to the simulation of the model. According to obtained results, the three-dimensional model achieved more reliable results and the existence of a gap for the three-dimensional model clearly demonstrated the impact of this parameter on the effective Knudsen force.

In this paper, the sensitivity of the micro-cantilever infrared detector has been increased by optimizing its geometric dimension. The detector's main body consists of an absorbing area, bi-material, and isolation legs, which are made up of silicon dioxide. Bi-material regions (absorbing area and bi-material legs) include a thin film layer of aluminum, which is placed on the main body layer. In this detector, the amount of bending at the end of the tip detector depends on the thickness of insulating and metal layers and the width of isolating and bi-material legs. Furthermore, it has been proved that the detector's displacement and sensitivity are optimized when the thickness of the metal layer is selected the half of the thickness of the absorbing layer. The results of the calculations show that by applying boundary conditions for 100 pW/μm2 constant thermal flux on the absorber, amount of displacement, thermomechanical, power, displacement, and body temperature sensitivities are increased by 26%, 27%, 28%, 2.3%, and 26%, respectively. In addition, the calculation results show that the sensitivities and response time are improved to 4.24, 54, 12.4, 12.8, 54, 4.2, 54.48, 54, and 1.5 times, respectively, in the vacuum environment if the leg’s width, the isolating and metal layers’ thicknesses are selected as 1μm, 0.1μm, and 0.05μm, respectively.

In this paper a one dimentional position-sensitive X-ray gas detector has been designed, simulated and constructed based on Multi Wire Proportional Chamber (MWPC) with delay line position readout. These kinds of detectors are useful in soft X-ray imaging and are capable of being extended to two dimensions position readout easily. The position resolution of this detector is estimated to be 230µ m