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The Large Observatory For x-ray Timing (LOFT) is a mission concept which was proposed to ESA as M3 and M4 candidate in the framework of the Cosmic Vision 2015-2025 program. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument and the uniquely large field of view of its wide field monitor, LOFT will be able to study the behaviour of matter in extreme conditions such as the strong gravitational field in the innermost regions close to black holes and neutron stars and the supra-nuclear densities in the interiors of neutron stars. The science payload is based on a Large Area Detector (LAD, > 8m(2) effective area, 2-30 keV, 240 eV spectral resolution, 1 degree collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e. g., GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the current technical and programmatic status of the mission.

ATLAS is a multi-purpose detector for the LHC and will detect proton-proton collisions with center of mass energy of 14 TeV. Part of the central inner detector, the Semi-Conductor Tracker (SCT) barrels, were assembled and tested at Oxford University and later integrated at CERN with the TRT (Transition Radiation Tracker) barrel. The barrel SCT is composed of 4 layers of silicon strip modules with two sensor layers with 80 micro m channel width. The design of the modules and the barrels has been optimized for low radiation length while maintaining mechanical stability, bringing services to the detector, and ensuring a cold and dry environment. The high granularity, high detector efficiency and low noise occupancy (< 5*10^-4) of the SCT will enable ATLAS to have an efficient pattern recognition capability. Due to the binary nature of the SCT read-out, a stable read-out system and the calibration system is of critical importance. SctRodDaq is the online software framework for the calibration and also the physics running of the SCT and has been developed and tested during construction and commissioning of the detector with cosmics. It reliably measures the SCT performance parameters for each of the 6.3*10^6 channels in the SCT, identifies defects and problematic modules and writes them to an offline database for access from Athena, the ATLAS offline software framework. This dataflow chain has been exercised during the cosmics run at CERN, where a 5*10^5 cosmics sample for the combined SCT and TRT detectors was collected with a scintillator based trigger. It is now being commissioned in the ATLAS pit.

In space experiments that study Charged Cosmic Rays (CCRs), a calorimeter combined with a tracker is used to identify the incoming particles. The back-scattered particles from the calorimeter can enter the tracker creating additional hits. The timing measurement for each hit can be utilized to distinguish between the back-scattered and primary hits. Low Gain Avalanche Detector (LGAD) is a promising technology for detecting particles with timing precision O(10) ps being developed for High-Energy Physics (HEP) experiments. With the current LGAD technology, it is difficult to achieve fine segmentation of sensors into channels. The typical size of an LGAD sensor is O(1 mm2) for HEP experiments whereas, silicon strip sensors in space applications have 50-60 cm long channels with 100 μm pitch, resulting in a channel area of about 1 cm2. The goal of this thesis is to evaluate the use of LGADs for timing in space. In view of this, the channel size of LGADs needs to be modified to O(1 cm2) to be utilized in space experiments. The larger channel size poses challenges for the time resolution of the sensors. First, the issues due to signal shape non-uniformity in pads and strips have been investigated, which can affect the timing performance of the sensors. Second, the fill factor problem due to the segmentation of LGADs is studied. The segmentation of LGADs results in the reduced active area of the sensor. Two different LGAD technologies namely RSD and TI-LGADs have been characterized as a possible solution to the segmentation problem. Finally, the work related to the scaling of the channel size of the LGADs from 1 mm2 to 1 cm2 is presented. TCAD simulations have been performed to obtain the process parameters for the gain layer to achieve a gain of 100 thought to improve the time resolution for larger channel areas. A batch of 16 wafers has been produced to study the adaptation of LGADs for space applications. The fabrication parameters have been optimized using TCAD simulations. This thesis contains the first characterization of the batch. This work aims to provide the instruments to advance the understanding of the fundamental properties of the universe and contribute to the development of LGADs technology for astroparticle physics experiments in space.

Silicon radiation detectors fabricated at the IMB-CNM (CSIC) Clean Room facilities using the most innovative techniques in detector technology are presented in this thesis. TCAD simulation comprises an important part in this work as becomes an essential tool to achieve exhaustive performance information of modelled detectors prior their fabrication and subsequent electrical characterization. Radiation tolerance is also investigated in this work using TCAD simulations through the potential and electric field distributions, leakage current and capacitance characteristics and the response of the detectors to the pass of different particles for charge collection efficiencies. Silicon detectors investigated in this thesis were developed for specific projects but also for applications in experiments which can benefit from their improved characteristics, as described in Chapter 1. Double-sided double type columns 3D (3D-DDTC) detectors have been developed under the NEWATLASPIXEL project in the framework of the CERN RD50 collaboration for the ATLAS Inner Detector upgrades and the introduction of a new pixel layer called Insertable B-Layer. The radiation tolerance of slim-edge (“edgeless”) detectors, whose current terminating structure reduces the insensitive area of detectors to 50 μm, for close-to-beam experiments like the TOTEM experiment at HL-LHC, have been simulated under the EU TOSTER project. Ultra-thin 3D detectors, which combine 3D detector technology and thin membrane fabrication process, are also studied in this work. They provide an alternative to the present Neutral Particle Analyzers at the International Thermonuclear Experimental Reactor (ITER) in the ions detection for plasma diagnosis, and they are also being used in neutron detection experiments after being covered with any layer containing 10B whose high capture cross-section of thermal neutrons allows their detection through the emitted alpha. Finally, active-edge detectors have been studied for applications in X-ray beam positioning, X-ray sensors for beamstops and detectors with pad, microstrip and Medipix2 designs for research purposes.

In-vivo dosimetry with diode detectors is used in radiation therapy as a quality assurance tool. The diode sensitivity under radiation depends upon temperature, dose rate and SDD (source-to-detector distance), field size, beam angle, and energy. This dissertation presents the first systematic and quantitative study of dosimetric characteristics for most of the commercial radiation diodes (n-type and p-type) under different radiation beams.In the temperature dependence study, the systematic study on the dose rate dependence of svwt (sensitivity variation with temperature) was performed. It was concluded that sufficient preirradiation can eliminate dose rate dependence of svwt. However, preirradiation cannot eliminate dose rate dependence of the diode sensitivity, S, itself. In the dose rate and SDD dependence study, it was shown that the p-type diodes do not always show less dose rate dependence than the n-type diodes. Preirradiation does not always reduce diode dose rate dependence. SDD dependence of diode sensitivity can be explained by the instantaneous dose rate dependence if sufficient buildup is provided to eliminate electron contamination. An empirical formula was proposed to fit the dose rate dependence of diode sensitivity. In the energy dependence study, the energy dependence diode detectors are quantified. The empirical theory to quantify this effect was developed. Monte Carlo simulation and the cavity theory are used to predict the energy dependence. It was concluded that the energy dependence does not depend on whether the diode is n- or p- type but rather depends mainly on the material around the die (buildup and its geometry). A systematic study of the correction factors for accurate diode dosimetry is presented in this dissertation.This dissertation has established a theoretical foundation for the modeling of the transient electric and radiation properties of the diode detectors, separately. We believe that the Monte Carlo simulations code for radiation transport should be coupled with the continuity equations to describe the charge transport in the diode detector, and thus provides a complete quantitative description of dosimetric characteristics of the diode detectors. The ultimate goal is to use the diode detector as an absolute dosimeter, rather than as a relative dosimeter.

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In this project, the homogeneity of the detection efficiency of two silicon detectors were examined using a radioactive alpha-source, 241Am, to study the surfaces of the detectors by exposing a small part of the detector at a time. By then observing the variations of the deposited alpha-energies at different positions on the detector, one can map the differences in the homogeneity of the surface. Many variations of different magnitudes were found; some variations can reasonably be represented by either variations in the dead layer or residue glue along the edges. Some variations seemed best explained by pieces of dust or dirt on the surface. The possibility of using heavy fission fragments from the decay of 252Cf to compare the effects was explored but shown to be non-feasible in the scope of this project. Finally, proposals for further work and improvements are discussed.