Toward Pulse by Pulse Dosimetry Using an SC CVD Diamond Detector

Solid state detectors with nanosecond response timesto incoming radiation are increasingly present at the forefrontof radiotherapy dosimetry research. The fast response time ofmaterials, such as diamond, allow pulse by pulse dosimetry. Thereis a trend in radiotherapy to move towards shorter treatments,using fewer but more intense pulses with varying pulse rates andintensities. This makes the possibility of measuring individualpulses very attractive and would allow intervention during thetreatment and not just afterwards. Here an analogue front endhas been developed and combined with a CVD diamond detectorto provide real time, pulse by pulse beam intensity measure-ments.The front end design is discussed and the experimentalresults obtained using a medical LINAC are presented. Theresults show that pulse by pulse The device is capable of pulseby pulse beam intensity measurements up to pulse rates wellabove 1 kHz. The system performs so well that its variations arenegligible compared to the pulse to pulse intensity variations.The dosimetric performance of our system was compared toa commercially available, integrating diamond detector, themicroDiamond by PTW. The dose and dose-rate linearity of oursystem is comparable with the one of the microDiamond and hasthe additional advantage of being able to measure the depositeddose per pulse

Modelling and development of tissue-equivalent dosimeters for small field radiotherapy.

A radiotherapy treatment is a clinical treatment which makes use of ionizing radiation to treat cancerous diseases. However, the ionizing radiation interacting within the cells can lead to DNA damage in both the cancerous and normal tissues. Therefore the exact knowledge of the dose delivered to the patient is essential because it greatly affects the effectiveness of the treatment. Dosimetry is usually performed by air ionization chambers however their use in the dosimetry of small photon beams is limited by their large sensitive volume. The ideal detector has a small, water-equivalent sensitive volume but the design of the detector and the presence of the encapsulation materials placed in close proximity to the sensitive volume can cause perturbations to the radiation fluence. The Monte Carlo method is the ideal tool because it allows a detailed investigation of the perturbation effects of each detector component but a Monte Carlo model often requires detailed information of the device which can be difficult to access. In this study, an experimental approach involving the use of CT scans and fluorescence spectroscopy in the measurements of the physical properties of a liquid ion chamber was explored. The performance of eight single crystal CVD diamond detectors in the dosimetry of photon beams was also assessed. One of the drawbacks of diamond detectors is the dose rate dependence. The evaluation of the dose rate dependence using clinical photon beams is controversial because the dose rate can be varied by either changing the source to detector distance or the Pulse Repetition Frequency of the LINAC machine. A simple analytical model of the charge collection dynamics was written in the Matlab code to understand the effects introduced by a pulsed radiation beam. The outcome of this study correlates the PRF dependence with the presence of deeper traps

The NASA SBIR product catalog

The purpose of this catalog is to assist small business firms in making the community aware of products emerging from their efforts in the Small Business Innovation Research (SBIR) program. It contains descriptions of some products that have advanced into Phase 3 and others that are identified as prospective products. Both lists of products in this catalog are based on information supplied by NASA SBIR contractors in responding to an invitation to be represented in this document. Generally, all products suggested by the small firms were included in order to meet the goals of information exchange for SBIR results. Of the 444 SBIR contractors NASA queried, 137 provided information on 219 products. The catalog presents the product information in the technology areas listed in the table of contents. Within each area, the products are listed in alphabetical order by product name and are given identifying numbers. Also included is an alphabetical listing of the companies that have products described. This listing cross-references the product list and provides information on the business activity of each firm. In addition, there are three indexes: one a list of firms by states, one that lists the products according to NASA Centers that managed the SBIR projects, and one that lists the products by the relevant Technical Topics utilized in NASA's annual program solicitation under which each SBIR project was selected

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

Research Report 2011-2012

El Centro Nacional de Aceleradores (CNA) es un centro mixto de la Universidad de Sevilla, la Junta de Andalucía y el Consejo Superior de Investigaciones Científicas, que tiene como misión el desarrollo de la investigación en aceleradores de partículas y sus múltiples aplicaciones. El CNA, reconocido como Instalación Científico-Técnica Singular (ICTS) es un centro abierto para que la comunidad científica y tecnológica nacional e internacional pueda desarrollar investigaciones utilizando sus instalaciones. Esta memoria es una introducción a la estructura, el personal, y el equipamiento del centro, y contiene la investigación realizada durante los años 2011 y 2012. Mostramos las capacidades del CNA, con el ánimo de favorecer el establecimiento de colaboraciones con los sectores científicos y tecnológicos.N

Radiation Damage Effects and Performance of Silicon Strip Detectors using LHC Readout Electronics

Future high energy physics experiments as the ATLAS experiment at CERN, will use silicon strip detectors for fast and high precision tracking information. The high hadron fluences in these experiments cause permanent damage in the silicon.Additional energy levels are introduced in the bandgap thus changing the electrical properties such as leakage current and full depletion voltage V_fd .Very high leakage currents are observed after irradiation and lead to higher electronic noise and thus decrease the spatial resolution.V_fd increases to a few hundred volts after irradiation and eventually beyond the point of stable operating voltages. Prototype detectors with either p-implanted strips (p-in-n) and n-implanted strip detectors (n-in-n) were irradiated to the maximum expected fluence in ATLAS.The irradiation and the following study of the current and V_fd were carried out under ATLAS operational conditions.The evolution of V_fd after irradiation is compared to models based on diode irradiations.The qualitative behaviour of V_fd as a func- tion of time is well described by these models although quantitative differences are observed between the different detectors.For the first time an annealing study is carried out on full size detectors showing that compared to diodes additional effects have to be taken into account.These properties include surface effects,geometric effects and process parameters. Measurements of V_fd on irradiated detectors show a temperature and frequency dependence indicating an influence of deep radiation induced damage levels.The obtained value of V_fd after irradiation can no longer be regarded as an absolute value due to the temperature and frequency dependence. The leakage current after irradiation is dominated by bulk effects.Although currents from the edge regions are much smaller than from the active area,guard rings are necessary to allow stable operation at high voltages after irradiation. It is shown that full size detectors with optimised guard ring design allow stable operation up to more than 400 V after irradiation.Parameters influencing the guard ring performance before irradiation are illustrated on prototype detectors. In general no systematic difference between p-in-n and n-in-n detectors in leak- age current,stability and the time dependence of V_fd is observed during this study. These results and the results from a testbeam with these detectors led to the change of the ATLAS detector baseline from n-in-n to p-in-n detectors. Non-irradiated and irradiated prototype detectors connected to fast analogue frontend electronics designed for LHC are tested with beta-sources and in a pion- testbeam.They show full functionality even after irradiation to the maximum expected fluence in ATLAS.At V_fd the observed signal to noise ratio (S/N) has not saturated which is attributed to the ballistic deficit caused by charge collection times in the order of the shaping time of the read out electronics.A calculation of the S/N increase after depletion as a function of charge collection time is in good agreement with the data.Between irradiated and non-irradiated detectors a decrease in S/N is observed.At sufficiently high voltages above V_fd the difference is explained by a noise increase due to higher leakage current while just above V_fd less signal is registered.The results presented illustrate that even after the maximum expected fluence ATLAS prototype detectors can be operated efficiently with LHC readout electronics

LDEF: 69 Months in Space. Third Post-Retrieval Symposium, part 3

This volume is a compilation of papers presented at the Third Long Duration Exposure Facility (LDEF) Post-Retrieval Symposium. The papers represent the data analysis of the 57 experiments flown on the LDEF. The experiments include materials, coatings, thermal systems, power and propulsion, science (cosmic ray, interstellar gas, heavy ions, micrometeoroid, etc.), electronics, optics, and life science. In addition, papers on preliminary data analysis of EURECA, EOIM-3, and other spacecraft are included

Electronics for Sensors

The aim of this Special Issue is to explore new advanced solutions in electronic systems and interfaces to be employed in sensors, describing best practices, implementations, and applications. The selected papers in particular concern photomultiplier tubes (PMTs) and silicon photomultipliers (SiPMs) interfaces and applications, techniques for monitoring radiation levels, electronics for biomedical applications, design and applications of time-to-digital converters, interfaces for image sensors, and general-purpose theory and topologies for electronic interfaces