Effect of Addition of Al to Sn-Zn Solder Alloys

Conventional solders consist of Lead, that was found to be toxic and carcinogenic. Hence, restrictions were put on its use by the industrially developed nations. To counter the use of Lead, active research was pursued into the development of Lead-free solders. In our project, we fabricated alloys of composition 3:15:82, 7:43:50 and 10:80:10 (in terms of Aluminium, Zinc and Tin respectively), under furnace cooled and air-cooled conditions. The use of Aluminium was made so as to increase the resistance of the solder to atmospheric corrosion, and also to improve the wettability of the samples. Optical micrographs were obtained for each sample so as to analyze their microstructures. For a deeper understanding, SEM images of each sample were obtained, and EDX analysis was performed side-by-side so as to understand the elemental composition of different phases present in the sample. DSC and TG tests were conducted to determine the melting point of the solder alloy, and the weight gain in the alloy on oxidation respectively. The wettability of each sample was also analyzed. We recorded and plotted down the trends in each case. We then tried to evaluate the most effective solder composition on the basis of the above tests. The near-eutectic composition was considered so as to avoid the formation of a pasty phase that will cause disruption in electrical work

Master of Science

thesisThis thesis encompasses the experimentation and development of neutron activation analysis protocols for the University of Utah Nuclear Engineering Program (UNEP). The University of Utah TRIGA Reactor (UUTR) was used as a neutron source to activate various materials to examine the inorganic elements. The Activity Estimator calculator was developed to approximate the activities of activated isotopes. Gamma ray activities, from activated samples, were acquired and measured on high purity germanium gamma spectroscopy detectors. Using the data collected from the gamma spectroscopy activated isotopes were identified and quantified. The activities from the identified isotopes were used to calculate the elemental concentrations of the sample materials using the Elemental Concentration Calculator and SRM Ratio Calculator. Complete NAA protocols and procedures were developed for a wide variety of materials and uses such as: criminal forensics, metals in soil, rock and water as well as minerals in fruits and vegetables

Radiation detectors and sources enhanced with micro/nanotechnology

The ongoing threat of nuclear terrorism presents major challenges to maintaining national security. Currently, only a small percentage of the cargo containers that enter America are searched for fissionable bomb making materials. This work reports on a multi-channel radiation detection platform enabled with nanoparticles that is capable of detecting and discriminating all types of radiation emitted from fissionable bomb making materials. Typical Geiger counters are limited to detecting only beta and gamma radiation. The micro-Geiger counter reported here detects all species of radiation including beta particles, gamma/X-rays, alpha particles, and neutrons. The multi-species detecting micro-Geiger counter contains a hermetically sealed and electrically biased fill gas. Impinging radiation interacts with tailored nanoparticles to release secondary charged particles that ionize the fill gas. The ionized particles collect on respectively biased electrodes resulting in a characteristic electrical pulse. Pulse height spectroscopy and radiation energy binning techniques can then be used to analyze the pulses to determine the specific radiation isotope. The ideal voltage range of operation for energy discrimination was found to be in the proportional region at 1000VDC. In this region, specific pulse heights for different radiation species resulted. The amplification region strength which determines the device sensitivity to radiation energy can be tuned with the electrode separation distance. Considerable improvements in count rates were achieved by using the charge conversion nanoparticles with the highest cross sections for particular radiation species. The addition of tungsten nanoparticles to the microGeiger counter enabled the device to be four times more efficient at detecting low level beta particles with a dose rate of 3.2uR/hr (micro-Roentgen per hour) and just under three times more efficient than an off the shelf Geiger counter. The addition of lead nanoparticles enabled the gamma/X-ray microGeiger counter channel to be 28 times more efficient at detecting low level gamma rays with a dose rate of 10uR/hr when compared to a device without nanoparticles. The addition of 10B nanoparticles enabled the neutron microGeiger counter channel to be 17 times more efficient at detecting neutrons. The device achieved a neutron count rate of 9,866 counts per minute when compared to a BF3 tube which resulted in a count rate of 9,000 counts per minute. By using a novel micro-injection ceramic molding and low temperature (950°C) silver paste metallizing process, the batch fabrication of essentially disposable micro-devices can be achieved. This novel fabrication technique was then applied to a MEMS neutron gun and water spectroscopy device that also utilizes the high voltage/temperature insulating packaging

Radioactive contamination in neutrino experimental physics: the cases of NEXT and super-kamiokande experiments

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física Teórica. Fecha de lectura: 26-09-201

Tube-based field-portable x-ray fluorescence (FPXRF) as a qualitative screening tool for resource conservation and recovery act (RCRA) metals in children’s products and comparison to total metals analyses to predict hazardous waste metals toxicity characteristic

This research was performed to assess the efficacy of tube-based field portable x-ray fluorescence (FXPXRF) devices to evaluate RCRA heavy metal concentrations in children\u27s products and determine potential hazardous waste toxicity characteristics by comparative analysis to inductively coupled plasma (ICP) yields per SW6010B. Sample sets consisting of wood, plastic, rubber, bulk, plated/coated, and metal matrices were purchased, size-reduced as necessary and directly analyzed three-times for 120 seconds each via FPXRF operated in the Consumer Goods/Test All mode. Subsequently, the same samples were prepared in accordance to SW3050B and analyzed via ICP at an accredited contract laboratory. Side-by-side results analysis indicates that FPXRF consistently exhibits positive bias compared to standard laboratory methods in the majority of matrices due to XRFs abilities to estimate total metallic analyte concentrations versus extract-labile substances only. Instances in which FPXRFs positive bias was absent were believed attributed to suboptimal sample homogeneity or limited sample area compared to total sample volume of SW3050B extraction. Though FPXRFs overestimation of metallic analyte concentrations does not directly correlate to SW6010B ICP yields without application of correction factors, it does provide a better indication of total versus liberated analyte presence

The Development of Microdosimetric Instrumentation for Quality Assurance in Heavy Ion Therapy, Boron Neutron Capture Therapy and Fast Neutron Therapy

This thesis presents research for the development of new microdosimetric instrumentation for use with solid-state microdosimeters in order to improve their portability for radioprotection purposes and for QA in various hadron therapy modalities. Monte Carlo simulation applications are developed and benchmarked, pertaining to the context of the relevant therapies considered. The simulation and experimental findings provide optimisation recommendations relating to microdosimeter performance and possible radioprotection risks by activated materials. The first part of this thesis is continuing research into the development of novel Silicon-on-Insulator (SOI) microdosimeters in the application of hadron therapy QA. This relates specifically to the optimisation of current microdosimeters, development of Monte Carlo applications for experimental validation, assessment of radioprotection risks during experiments and advanced Monte Carlo modelling of various accelerator beamlines. Geant4 and MCNP6 Monte Carlo codes are used extensively in this thesis, with rigorous benchmarking completed in the context of experimental verification, and evaluation of the similarities and differences when simulating relevant hadron therapy facilities. The second part of this thesis focuses on the development of a novel wireless microdosimetry system - the Radiodosimeter, to improve the operation efficiency and minimise any radioprotection risks. The successful implementation of the wireless Radiodosimeter is considered as an important milestone in the development of a microdosimetry system that can be operated by an end-user with no prior knowledge

Material radioassay and selection for the XENON1T dark matter experiment

The XENON1T dark matter experiment aims to detect weakly interacting massive particles (WIMPs) through low-energy interactions with xenon atoms. To detect such a rare event necessitates the use of radiopure materials to minimize the number of background events within the expected WIMP signal region. In this paper we report the results of an extensive material radioassay campaign for the XENON1T experiment. Using gamma-ray spectroscopy and mass spectrometry techniques, systematic measurements of trace radioactive impurities in over one hundred samples within a wide range of materials were performed. The measured activities allowed for stringent selection and placement of materials during the detector construction phase and provided the input for XENON1T detection sensitivity estimates through Monte Carlo simulations

Alternative design concepts for the electron to photon converter in the accelerator based production of technetium-99m

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1997.Includes bibliographical references (p. 75).The photonuclear production of radioisotopes using electron LINAC bremsstrahlung sources offers an industry alternative to reactor and ion beam production methods. One such method under development is the utilization of the Giant Dipole Resonance in the (y,n) reaction cross-section. This method is being studied for use in the production of 99mTc from enriched 100Mo by electron beam induced bremsstrahlung photons. Of primary concern to any radioisotope production system is the specific activity it is able to create of the radioisotope. In a photoneutronic production system maximizing the number of GDR photons on a given target increases the specific activity. Proper design and optimization of the electron-to-photon converter maximizes the number of GDR photons. This study examines some alternative types of converter design. MCNP is used to predict isotope yields and energy deposition in the converter assemblies and an Excel Spreadsheet is used to analyze the heat-transfer capabilities of the systems. Optimized designs are presented for the different types of converters studied. A radiantly cooled converter is presented as a low-yield design, while a circulating loop of molten lead is analyzed for use in a high-yield system.by Jess L. Iverson.S.M

Remodelling a multi-anode ionisation chamber detector for accelerator mass spectrometry of 53Mn

Accelerator Mass Spectrometry (AMS) is a single-atom counting technique that measures the abundance of rare, long-lived radioisotopes using only milligrams of sample. The astrophysical radioisotopes 53Mn and 60Fe have been utilised for many applications including meteoritics, exposure dating, and the search for near-Earth supernovae. 53Mn measurements at the ANU have been limited to sensitivities above 10^-13 by insufficient suppression of the stable isobar, 53Cr. To expand the applications accessible to 53Mn analysis, a new detector was commissioned that will improve the available sensitivity. This thesis covers the implementation of the new Flexible Anti-Scatter Multi-Anode (FASMA) detector. Simulations were conducted to determine the optimal placement of the detector inside the gas-filled magnet, and to assist with the design of a new multi-anode configuration. The FASMA detector was successfully tested and full spectra were recorded. These preliminary results indicate an improvement in the achievable sensitivity, even without the suppression of scattered particles. With further work, the FASMA detector should reach a sensitivity at or below 10^-14, which is competitive with the best reported level in the field. Long-lived radionuclides, such as 53Mn and 60Fe, are important for extracting the exposure history of meteorites, both in space and on Earth, as well helping to identify their origin. In light of this, cosmogenic 53Mn and 60Fe ratios were measured in ten meteorite samples. Since the available data on live 53Mn and 60Fe is scarce, these measurements will improve the constraints on current production rate models for meteorites