Pusat Pengajian Sains Fizik - Tesis
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- PublicationMulti-layer Radiation Shielding Design For Compact Proton Therapy System Using Monte Carlo Simulation(2024-09)Aliyah, FitrotunProton therapy has emerged as a highly effective treatment for various cancers due to its precision in targeting tumor cells while minimizing radiation exposure to surrounding healthy tissues. However, the design of compact proton therapy facilities poses significant challenges, particularly in terms of shielding requirements, cost, and environmental impact. This study aims to develop a novel shielding design for proton therapy systems that complies with regulatory dose limits while reducing the overall cost and footprint by utilizing alternative materials through a multilayer structure model. The research begins with the characterization of natural aggregate and steel slag as potential alternative materials for concrete admixture, then continues with experimental evaluations of radiation attenuation properties using PuBe, LINAC, and CT-Scan as radiation sources. To further develop and optimize the shielding design, the study employed Monte Carlo simulations using the Particle and Heavy Ion Transport code System (PHITS). These simulations facilitated the creation of innovative shielding configurations, incorporating both single-layer and multilayer structures composed of Portland concrete (PC), steel slag concrete (SSC) , iron (Fe), borated polyethylene (BPE), and recycled high-density polyethylene (HDPE). The experiment results demonstrate that steel slag concrete offers superior radiation shielding performance compared to conventional concrete. The PHITS simulation results demonstrate that the material combination model of PC-SSC on the treatment room wall and PC-SSC-Fe-HDPE on the Maze 1 wall is the optimal configuration with ambient dose equivalent rate value ranging from 13 to 773 mSv/year.
- PublicationCharacterization Of Multilayer ZnO/METAL/ZnO As pH Sensor(2019-07)Rasheed, Hiba SaadThis study focused on the synthesis and characterisation of ZnO/metal/ZnO multilayer thin films for extended gate field effect transistors in pH sensor devices by using a physical method. Multilayer structures ZnO/metal/ZnO and ZnO single layer were deposited on glass substrate via radio frequency and direct current magnetron sputtering.
- PublicationOptically Pumped Lasing Properties Of ZnO Nanorods(2018-11)Nordin, Muhammad NuriThe purpose of this study is to investigate the characteristics of optically pumped laser from the ZnO nanorods grown by using the two-step chemical bath deposition (CBD). Samples are grown on two types of substrates, glass and sapphire wafer, AI2O3. Various conditions and treatments of the samples have been introduced to observe the optical emission mainly by manipulating the thickness of ZnO seed layer thin film and the heat treatment condition. The procedures for CBD process is fixed for four hours at 97“C for growth process with the solutions of 0.05 M of zinc nitrate (Zn(NO.3)2.6H2O) and 0.05 M of hexamethylenetetramine (11 MT).
- PublicationModelling Of Potential Field Data For Shallow Thermal And Crustal Structure Beneath Peninsular Malaysia(2022-12)Yaro, Usman YahayaThis thesis has taken advantage of the global compilation of potential field data to derive the first regional thermal structure as well as the most resolved crustal thickness model for the entire Peninsular Malaysia and neighbouring regions. Bore-hole heat flow data can provide the most precise information about the thermal structure of the crust, but these measurements are extremely difficult to obtain (expensive, sparse, and limited to shallow depths). The depth to bottom of magnetic sources (DBMS) has traditionally been used as alternative to surface heat flow data. In this study, DBMS are derived assuming random uncorrelated and fractal magnetisation models. DBMS using fractal distribution of sources (~ 17 – 46 km with a mean of 29 km) are found to be lower than the values computed using conventional random method (29 – 67.4 km with a mean value of 49.3 km) and reasonably well while considering other tectonic and geophysical constraints. Despite, the differences in the derived DBMS for the two methods, visual inspection and cross plots shows that they are linearly correlated, and they have the same pattern and trends. Crustal thickness for the study area varies from ~ 27.4 – 34.6 km with an average of 30.8 km. A comparison between the derived DBMS and crustal thickness shows that the upper mantle beneath the west Sumatra, Singapore, Malay basin, NW Peninsular Malaysia, and southern Thailand are significantly magnetised. The presence of magnetic upper mantle point to the stability of these regions attributable to low heat flow, geothermal gradient, and serpentinization.
- PublicationBlack Silicon Fabricated By Silver-Assisted Chemical Etching For Flexible Solar Cells(2023-03)Omar, Halo DalshadMonocrystalline silicon (mono c-Si) dominates more than 90% of photovoltaic market due to increasing solar cell efficiencies, technology maturity and reducing technology cost. Currently, photovoltaic manufacturing uses solar cells with 180 μm thickness. To reduce the technology cost, one promising strategy is by reducing the c-Si wafer thickness below 100 μm, whereby the wafer becomes flexible. Furthermore, flexible c-Si introduces new features including flexibility, light weight and makes thin c-Si highly attractive for flexible solar cells. Most importantly, thin c-Si solar cells usually demonstrate higher open circuit voltage (Voc) due to the lower bulk recombination and more efficient electron-hole pair extraction. However, one big challenge of the thin c-Si is the insufficient light absorption due to the indirect bandgap of the c-Si. Additionally, planar c-Si exhibits a high broadband reflection of around 35% within 300-1100 nm wavelength region, which further reduces the light absorption in the c-Si. To improve the light absorption in the thin c-Si wafers, black silicon (b-Si) offers a great potential for solar cell application since it yields a superior broadband light absorption within 300-1100 nm wavelength region. This is attributed to refractive index (n) grading effect,