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In the present work we studied an influence of different types of surface etching and surface passivation of high resistivity CdZnTe-based semiconductor detector material. The aim was to find the optimal conditions to improve the properties of metal-semiconductor contact. The main effort was to reduce the leakage current and thus get better X-ray and gamma-ray spectrum, ie to create a detector operating at room temperature based on this semiconductor material with sufficient energy resolution and the maximum charge collection efficiency. Individual surface treatments were characterized by volt-ampere characteristics, spectral analysis and by determination of the profile of the internal electric field.

Macromolecular X-ray crystallography (MX) is currently the dominant technique for the structural eluci- dation of macromolecules at near atomic resolution. However, the progression and deleterious effects of radiation damage remains a major limiting factor in the success of diffraction data collection and subsequent structural solution at modern third generation synchrotron facilities. For experiments conducted at 100 K, protein specific damage to particular amino acids has been widely reported at doses of just several MGy, before any observable decay in average diffraction intensities. When undetected, such artefacts of X-ray irradiation can lead to significant modelling errors in protein structures, and ultimately the failure to derive the correct biological function from a model. It is thus vital to develop tools to help MX experimenters to detect and correct for such damage events. This thesis presents the development of an automated program, RIDL, which is designed to objectively quantify radiation-induced changes to electron density at individual atoms, based on F_obs,n − F_obs,1 Fourier difference maps between different dose states for a single crystal. The high-throughput RIDL program developed in this work provides the ability to systematically investigate a wide range of macromolecular systems. To date, damage to the broad class of nucleic acids and nucleoprotein complexes has remained largely uncharacterised, and it is unclear how radiation damage will disrupt the validity of such models derived from MX experiments. This thesis presents the first systematic investigations on a range of nucleic acid, protein-RNA and protein-DNA complex case studies. In general, it is concluded that nucleic acids are highly robust to radiation damage effects at 100K, relative to control protein counterparts across the tested systems. For protein crystals at 100K, cleavage of the phenolic C-O bond in tyrosine has disseminated through the MX radiation damage literature as a dominant specific damage event at 100K, despite the absence of any energetically favourable cleavage mechanism. To clarify the radiation susceptibility of tyrosine, this thesis presents a systematic investigation on radiation damage to tyrosine in a wide range of MX protein radiation damage series retrieved from the Protein Data Bank. It is concluded that the tyrosine C-O bond remains intact following X-ray irradiation, however the aromatic side-group can undergo radiation-induced displacement. This thesis also presents further applications of the RIDL program. A protocol is introduced to calculate explicit half-dose values for the electron density at individual atoms to decay to half of their initial value at zero absorbed dose. In addition, a methodology is developed to detect radiation-induced changes to electron density occurring over the course of the collection of a single MX dataset of diffraction images, all of which are required for structural solution. These protocols aim to advise experimenters of when previously-undetected site-specific damage effects may have corrupted the quality of their macromolecular model. Overall, the work in this thesis is highly applicable to both the future understanding of radiation damage in macromolecular structures, as well as of interest to the wider crystallographic community.

Acquisition of X-ray crystallographic data is always accompanied by structural degradation owing to the absorption of energy. The application of high-fluency X-ray sources to large biomolecules has increased the importance of finding ways to curtail the onset of X-ray-induced damage. A significant effort has been under way with the aim of identifying strategies for protecting protein structure. A comprehensive model is presented that has the potential to explain, both qualitatively and quantitatively, the structural changes induced in crystalline protein at 100 K. The first step is to consider the qualitative question: what are the radiation-induced intermediates and expected end products? The aim of this paper is to assist in optimizing these strategies through a fundamental understanding of radiation physics and chemistry, with additional insight provided by theoretical calculations performed on the many schemes presented.

Despite significant improvements in medical sciences over the last decade, cancer still continues to be a major cause of death in humans throughout the world. Parallel to the efforts of understanding the intricacies of cancer biology, researchers are continuously striving to develop effective cancer detection and treatment strategies. Use of nanotechnology in the modern era opens up a wide range of possibilities for diagnostics, therapies and preventive measures for cancer management. Although, existing strategies of cancer detection and treatment, using nanoparticles, have been proven successful in case of cancer imaging and targeted drug deliveries, they are often limited by poor sensitivity, lack of specificity, complex sample preparation efforts and inherent toxicities associated with the nanoparticles, especially in case of in-vivo applications. Moreover, the detection of cancer is not necessarily integrated with treatment. X-rays have long been used in radiation therapy to kill cancer cells and also for imaging tumors inside the body using nanoparticles as contrast agents. However, X-rays, in combination with nanoparticles, can also be used for cancer diagnosis by detecting cancer biomarkers and circulating tumor cells. Moreover, the use of nanoparticles can also enhance the efficacy of X-ray radiation therapy for cancer treatment. This dissertation describes a novel in vitro technique for cancer detection and treatment using X-ray radiation and nanoparticles. Surfaces of synthesized metallic nanoparticles have been modified with appropriate ligands to specifically target cancer cells and biomarkers in vitro. Characteristic X-ray fluorescence signals from the X-ray irradiated nanoparticles are then used for detecting the presence of cancer. The method enables simultaneous detection of multiple iv cancer biomarkers allowing accurate diagnosis and early detection of cancer. Circulating tumor cells, which are the primary indicators of cancer metastasis, have also been detected where the use of magnetic nanoparticles allows enrichment of rare cancer cells prior to detection. The approach is unique in that it integrates cancer detection and treatment under one platform, since, X-rays have been shown to effectively kill cancer cells through radiation induced DNA damage. Due to high penetrating power of X-rays, the method has potential applications for in vivo detection and treatment of deeply buried cancers in humans. The effect of nanoparticle toxicity on multiple cell types has been investigated using conventional cytotoxicity assays for both unmodified nanoparticles as well as nanoparticles modified with a variety of surface coatings. Appropriate surface modifications have significantly reduced inherent toxicity of nanoparticles, providing possibilities for future clinical applications. To investigate cellular damages caused by X-ray radiation, an on-chip biodosimeter has been fabricated based on three dimensional microtissues which allows direct monitoring of responses to X-ray exposure for multiple mammalian cell types. Damage to tumor cells caused by X-rays is known to be significantly higher in presence of nanoparticles which act as radiosensitizers and enhance localized radiation doses. An analytical approach is used to investigate the various parameters that affect the radiosensitizing properties of the nanoparticles. The results can be used to increase the efficacy of nanoparticle aided X-ray radiation therapy for cancer treatment by appropriate choice of X-ray beam energy, nanoparticle size, material composition and location of nanoparticle with respect to the tumor cell nucleus.

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The aim of the study was to investigate the effect of X-rays used in micro X-ray computer tomography (µXCT) on the mechanical performance and microstructure of a variety of dental materials. Standardised bending beams (2 × 2 × 25 mm3) were forwarded to irradiation with an industrial tomograph. Using three-dimensional datasets, the porosity of the materials was quantified and flexural strength was investigated prior to and after irradiation. The thermal properties of irradiated and unirradiated materials were analysed and compared by means of differential scanning calorimetry (DSC). Single µXCT measurements led to a significant decrease in flexural strength of polycarbonate with acrylnitril-butadien-styrol (PC-ABS). No significant influence in flexural strength was identified for resin-based composites (RBCs), poly(methyl methacrylate) (PMMA), and zinc phosphate cement (HAR) after a single irradiation by measurement. However, DSC results suggest that changes in the microstructure of PMMA are possible with increasing radiation doses (multiple measurements, longer measurements, higher output power from the X-ray tube). In summary, it must be assumed that X-ray radiation during µXCT measurement at high doses can lead to changes in the structure and properties of certain polymers.

Cette thèse est centrée sur la mesure et l'interprétation du rayonnement X mou ([1 keV; 15 keV] environ) dans les Tokamaks. Le chapitre 2 montre que ce rayonnement véhicule des informations sur la température et la densité du plasma, sur sa configuration magnétique, et sur son contenu en impuretés. Malheureusement les mesures effectuées sont intégrées spatialement et spectralement et résultent des contributions de tous les ions présents.Le diagnostic X mou de Tore Supra s'articule autour de diodes semi-conductrices présentée dans le chapitre 3 aux côté d'un détecteur à gaz testé avec succès. Une nouvelle méthode de détermination de la réponse spectrale d'un photodétecteur n'utilisant qu'un tube X mou portable est également décrite.Les inversions tomographiques, qui permettent d'accéder au champ d'émissivité reconstruit dans une section poloidale, font l'objet du chapitre 4. Les améliorations apportées à un algorithme particulier sont détaillées.Une comparaison systématique entre les positions horizontales du maximum d'émissivité et de l'axe magnétique est présentée au chapitre 5.Le chapitre 6 décrit une hypothèse concernant la résilience de la fonction de rayonnement X mou d'une impureté vis-à-vis du transport de cette impureté. Cette hypothèse permet de déduire la densité d'une impureté de son émissivité X mou. Les processus physiques justifiant cette hypothèse, ainsi que leur domaine de validité sont analysés avec soin.Le chapitre 7 présente les asymétries poloidales d'émissivité X mou. Les premiers résultats d'expériences mises en oeuvres à ASDEX-U pour vérifier les dépendences paramétriques de deux types particuliers d'asymétries sont détaillés. / This thesis focuses on measuring and interpreting the Soft X-Ray (SXR) radiation (approximately [1 keV; 15 keV]) in Tokamaks.As explained in Chapter 2, this radiation conveys information about the plasma density, temperature, magnetic equilibrium and impurity content. However, the measured data is spectrally and spatially-integrated and results from several physical phenomena affecting every ion species. Tore Supra's SXR diagnostics is based on semiconductor diodes presented in Chapter 3, along with a new gas detector successfully tested in laboratory and on Tore Supra. A new methodology for absolute spectral characterisation of photo detectors using a portable SXR tube is presented. Tomographic inversion algorithms, that grant access to reconstructions of the SXR emissivity field in a poloidal cross-section, are presented in Chapter 4. Improvements implemented on one particular algorithm are detailed with examples of application. A comparison between the position of the SXR emissivity maximum and the magnetic axis reconstructed by an equilibrium code is presented in Chapter 5.Chapter 6 presents an approach used to derive an impurity density from its SXR emissivity using the robustness of its SXR cooling factor with respect to impurity transport. The physics accounting for this robustness is studied and a first map of the domain of validity of this method is provided. Chapter 7 addresses poloidal asymmetries of the SXR emissivity field. Two types of asymmetries are presented as well as experiments conducted on ASDEX-U to verify their parametric dependences. A new type of SXR asymmetry, observed on Tore Supra is introduced.