Workshop on X-rays from electron beams with special emphasis on possible developments at ELBE

Workshop on X-rays from electron beams with special emphasis on possible developments at ELBE

This thesis investigates the response of Gallium Arsenide (GaAs) detectors to ionizing irradiation. Detectors based on π-υ junction formed by deep level centers doping. The detectors have been irradiated with 137Cs γ-rays up to 110 kGy, with 6 MeV mean energy neutron up to approximately 6 · 1014 n/cm2, with protons and mixed beam up to 1015 p/cm2. Results are presented for the effects on leakage currents and charge collection efficiencies for minimum ionizing electrons and alpha particles. The signal from minimum ionizing electrons was well separated from the noise even after the highest delivered exposures and the diodes are thus still operational as detectors. Saturation of the effects of radiation damage is observed in both the I-V characteristics and charge collection efficiency measurements. The requirements for detectors e.g. at present and planned hadron colliders is very high in terms of radiation hardness. Detectors for tracking applications close to the interaction point will receive charged particle doses in the range of 110 kGy and fast neutron fluences of 1014 n/cm2 during the lifetime of an experiment. In this thesis it is confirmed that GaAs detectors are radiation resistant to neutron irradiation for fluences up to 1015 n/cm2 and that GaAs detectors are feasible as inner trackers. Most of this work was performed in the framework of the RD8 collaboration at CERN. / <p>QC 20100920</p>

<p> The main motivation of the Compact Muon Solenoid (CMS) experiment is to explore and to discover physics underlying electro-weak asymmetry breaking. Beside this, CMS detector provides an opportunity to do various experiments for detecting new physics signatures beyond the Standard Model (SM). Investigation of these signatures requires the identification and precise energy and moment measurement of electrons, muons, photons, and jets. The objective of this thesis is the calculation of the efficiencies for the measurement of W charge asymmetry in inclusive <i>pp</i> &rarr; <i>W</i> (&mgr;&upsi;) production. The charge asymmetry is defined to be the difference between W⁺ and W^&minus; bosons, normalized to the sum. This asymmetry is sensitive to the u-quark and d-quark ratios in the proton and precise measurement of the W charge asymmetry can provides new insights to the proton structure functions. Therefore, to improve understanding of SM backgrounds in search for new physics, the moun trigger, isolation, reconstruction, identification efficiencies has been studied using partial data collected by the CMS detector during pp collisions at the LHC in 2011. The dataset corresponds to an integrated luminosity of 2.31 fb^&minus;1. The efficiencies are measured as functions of the decay muon pseudo rapidity and transverse momentum based on "tag and probe" method. The efficiency measurements are compared to their estimated value from the Monte Carlo simulations so as to provide scaling factors to correct to the residual mis-modeling of the CMS muon performance. The comparison with simulations based on MC simulations opens a gate for validation of the detector simulation and optimization of selection strategies.</p>

<p> Abstract not available.</p>

<p> Abstract not available.</p>

<p> The Lithium Tokamak Experiment (LTX) is a spherical tokamak designed to study the lowrecycling regime through the use of lithium-coated shells conformal to the last closed flux surface (LCFS). A lowered recycling rate is expected to flatten core <i>T</i>_e profiles, raise edge <i>T</i>_e, strongly affect <i>n</i>_e profiles, and enhance confinement.</p><p> To study these unique plasmas, a Thomson scattering diagnostic uses a &le; 20 J, 30 ns FWHM pulsed ruby laser to measure <i>T</i>_e and <i>n</i>_e at 11 radial points on the horizontal midplane, spaced from the magnetic axis to the outer edge at a single temporal point for each discharge. Scattered light is imaged through a spectrometer onto an intensified CCD. The diagnostic is absolutely calibrated using a precision light source and Raman scattering. Measurements of <i>n</i>_e are compared with line integrated density measurements from a microwave interferometer. Adequate signal to noise is obtained with ne &ge; 2 &times;10¹⁸ m^&ndash;3.</p><p> Thomson profiles of plasmas following evaporation of lithium onto room-temperature plasmafacing components (PFCs) are used in conjunction with magnetic equilibria as input for TRANSP modeling runs. Neoclassical calculations are used to determine <i> T</i>_i profiles, which have levels that agree with passive charge exchange recombination spectroscopy (CHERS) measurements. TRANSP results for confinement times and stored energies agree with diamagnetic loop measurements. Results of &chi;_e result in values as low as 7 m²/s near the core, which rise to around 100 m²/s near the edge. These are the first measurements of &chi;e in LTX, or its predecessor, the Current Drive Experiment-Upgrade (CDX-U), with lithium PFCs.</p>

<p>In high-energy collisions of gold nuclei at the Relativistic Heavy Ion Collider (RHIC) and of lead nuclei at the Large Hadron Collider (LHC), a new state of matter known as the Quark-Gluon Plasma (QGP) is formed. This strongly-coupled, deconfined state of quarks and gluons represents the high energy-density limit of quantum chromodynamics. The QGP can be probed by high-momentum quarks and gluons (collectively known as partons) that are produced in hard scatterings early in the collision. The partons traverse the QGP and fragment into collimated "jets" of hadrons. Studies of parton energy loss within the QGP, or medium-induced jet quenching, can lead to insights into the interactions between a colored probe (a parton) and the colored medium (the QGP).</p><p> Two analyses of jet quenching in relativistic heavy ion collisions are presented here. In the jet-hadron analysis, the distributions of charged hadrons with respect to the axis of a reconstructed jet are investigated as a function of azimuthal angle and transverse momentum (<i>p</i>_T). It is shown that jets that traverse the QGP are softer (consisting of fewer high-<i>p</i>_T fragments and more low-<i>p</i>_T constituents) than jets in <i>p+p</i> collisions. There are also indications that the shapes of the distributions of charged hadrons about the jet axis are modified by interactions with the QGP. The results are quantitatively consistent with two models of medium-induced radiative parton energy loss.</p><p> A measurement of jet <i>v</i>₂, defined as the correlation between reconstructed jets and the reaction plane or 2<i>^nd</i>-harmonic participant plane (approximated by the 2<i>^nd</i>-harmonic event plane), provides information about the medium-induced pathlength-dependence of parton energy loss. The event plane is reconstructed with detectors at forward pseudorapidity in order to reduce the artificial jet &ndash; event plane bias, which results from jet fragments being included in the event plane calculation. A non-zero jet <i>v</i>₂ is measured, indicating that more jets are reconstructed with a higher energy in-plane compared to out-of-plane, which demonstrates that the parton energy loss depends on the length of the parton's path through the QGP.</p><p> The data analyzed here were collected in [special characters omitted] = 200 GeV Au+Au and <i>p+p</i> collisions at the STAR detector at RHIC. A novel method for measuring jet <i>v</i>₂ is also proposed and tested in simulation.</p>

Lung diseases affect the lives of millions of people across the UK and result in the thousands of deaths every year. It is therefore vitally important to continue to develop a wide range of diagnostic techniques to improve our understanding of lung diseases and how they can be treated. This thesis provides an overview of the main methods of assessing lung condition before focussing on developments in two specific areas: Forced Oscillation Technique (FOT) and Hyperpolarised (HP) gas MRI. FOT is an inexpensive, non-invasive lung function test that measures the acoustic impedance of the airways by applying an oscillating waveform via a mouthpiece. FOT cannot be used to image the lung but instead provides information on a variety of other physiological parameters. Two FOT studies are presented in this thesis: a multi-site phantom study and a patient based study. The phantom study confirmed the validity of the Nottingham FOT system used in the patient study and investigated the effects of lung stiffness and airway obstruction on measured FOT parameters using a 3D printed lung phantom, as well as comparing phantom results between three different FOT devices (an in-house device from the University of Nottingham, an Erich Jaeger Master-Screen IOS and a tremoFlo C-100 airwave oscillometry system) at two sites (the University of Nottingham and Glenfield Hospital, Leicester). It was found that changes in lung stiffness and airway obstruction are observable in the reactive and resistive (respectively) components of measured impedance. A difference was seen between the Jaeger IOS system and the other two devices. The patient based study was undertaken to investigate the efficacy of FOT, in comparison to spirometry, in differentiating between three patient groups, healthy, asthmatic and chronic obstructive pulmonary disease (COPD), with a particular focus on investigating the effect of a bronchodilator on measured FOT parameters. It was found that both FOT and Spirometry were effective at differentiating between the patient groups, however, they provided different information about patient response to bronchodilator thus demonstrating that both techniques should be performed to obtain the maximum information about a patient's disease state. HP gas MRI uses isotopes of noble gases, such as 3He and 129Xe, to either image the lungs or perform non-imaging measurements of parameters such as the Apparent Diffusion Coeffcient (ADC). A short study using 3He was performed comparing ADC measurements at two different time scales between two sites (the University of Nottingham, 13ms, and the University of Sheffield, 2ms) with a secondary aim of investigating the effect of age on ADC. A study on HP 129Xe MRI is presented covering developments that have been made in various imaging techniques including breathing protocols and scanning techniques. The objective of this study is to establish a reliable scanning protocol using healthy volunteers before expanding the study to investigate different disease states including COPD and idiopathic pulmonary Fibrosis (IPF). Although progress has been made in testing the validity of various imaging techniques, with ventilation images at 25mm and 10mm slice thicknesses obtained, more development is still needed to improve the quality of the images in order for them to be useful in a clinical setting.

A range of experimental techniques for application in reaction studies between ionic and neutral atoms/molecules and high resolution spectroscopy experiments with sympathetically cooled molecular ions are presented. A novel ion trap loading scheme using the photo-ionisation of atoms generated by the pulsed laser ablation of a solid calcium target has been characterised. We have identified the range of ablation laser fluences that must be used in order to produce a flux of neutral calcium atoms, which is a prerequisite for isotope selective ion trap loading. Calcium ions are trapped and laser cooled in a linear radio-frequency ion trap. We have developed a spectroscopy scheme that allows the entire fluorescence spectrum of trapped ions to be rapidly collected with high precision while maintaining a low ion temperature and good ion localisation throughout interrogation. The scheme has been demonstrated by measuring the saturation intensity of the calcium ion 4S1/2→4P1/2 transition. We have developed a novel scheme to measure the secular motion of trapped ions and demonstrated the application of the technique to ion-neutral collision reaction experiments. Employing pulsed excitation and Doppler velocimetry, we have measured the centre-of-mass mode frequency of single ions as well as large ion crystals with a frequency precision better than 2x10-3 within an interrogation time on the order of seconds. This method has been used to measure the mass of ions and observe charge exchange collisions between trapped calcium isotopes. In particular, we have measured the 44Ca++40Ca!40Ca++44Ca reaction cross section and demonstrated the single-event resolution of the technique. Finally, we have developed a novel all-optical broadband scheme for exciting, amplifying and measuring the secular motion of ions in the trap. Oscillation induced by optical excitation has been coherently amplified to control and measure the ion's secular motion. Requiring only a single interrogation laser, the ion's oscillation amplitude can be precisely controlled. The application of this technique to non-destructive spectroscopy of trapped molecular ions is discussed.