We investigate the model of a disk/coronal accretion flow into a black hole. We build a numerical code to ascertain whether the inner regions of an accretion disk in X-ray binaries can transform from a cool standard disk to an advection-dominated flow through the known properties of Coulomb interaction in a two-temperature plasma, taking into account viscous heating, standard radiation processes, and thermal conduction. A hot, diffuse corona covering the whole disk is powered by accretion, but it exchanges energy with the underlying cool disk through radiative interactions and conduction. If the accretion rate is low enough, at some intermediate radius the corona begins to evaporate the cool disk away, leaving an advective coronal flow to continue towards the hole as consistent with X-ray observations that I have studied using XMM-Newton and Chandra. We show that if the accretion rate increases sufficiently, complete evaporation does not occur and the cool inner disk remains, proceeding inward to the innermost stable orbit. During spectral transitions an intermediate state has been observed whose nature is unclear, but which shows the presence of cold matter near an X-ray emitting source, along with an additional component that could come from an advective coronal flow. We build a steady-state model that includes these effects and mass exchange between the two flows through evaporation and recondensation during the soft/hard transition and create a "hysteresis" similar to that observed, along with representative spectra for each X-ray state.

Quantum optical metrology deals with estimation of an unknown parameter by exploiting the non-classical properties of the light. The unknown parameter that we are trying to estimate is the optical phase. Precise optical phase measurement has been a well-known problem and has many applications, most notably the gravitational wave detection. In this thesis we investigate the interferometric measurement schemes. We consider the parity detection for a class of input states that have been shown to exhibit sub-shot noise limited phase estimate with their respective detection schemes. Our results indicate that the parity detection applies to all these strategies with various input states and thus acts as a unified detection scheme towards the goal of interferometric phase estimates beyond the shot-noise limit. We also consider the performance of the so-called optimal state with the canonical phase measurement scheme that was proposed by Sanders and Milburn [Phys. Rev. Lett. 75, 2944 (1995)] in presence of photon loss. The model for photon loss is a generic fictitious beam splitter and the analytical treatment requires density matrix approach rather than the state-vector formalism. We present full density-matrix calculations. Our results indicate that, for a given amount of loss, the phase estimate saturates but does not diverge as one would expect with increasing the loss. Finally, we study the continuous measurement and feedback scheme with optical homodyne detection for a single optical qubit. We found a protocol that speeds up the rate of increase of the average purity of the system and generates a deterministic evolution for the purity in the limit of strong feedback.

Dynamical systems involving black holes are one of the most promising sources of detectable gravitational waves. Additionally, one expects strong electromagnetic signals whenever matter sources are present. In this dissertation, we study different astrophysical scenarios pertaining the interaction of matter with a black hole. We first investigate the possibility to localize scalar field configurations surrounding a (dynamic) black hole. The analytical study is illustrated by performing numerical simulations that show the evolution of a Klein-Gordon-like scalar field shell surrounding a black hole. Second, we present a method to estimate the gravitational wave frequency at the end of the inspiral phase of a compact binary. This method is applied to study the possibility of a neutron stars tidal disruption occurring before plunging into the companion black hole, and to provide a way of improving gravitational wave data analysis when using match filtering techniques. Last, we study the effects of a black hole merger on a circumbinary disk. We consider separately the effects of central mass reduction (due to the energy loss through gravitational waves) and black hole recoil (due to asymmetric emission of gravitational radiation), presenting possibly detectable electromagnetic signatures.

In this work, we present some applications of the theory of General Relativity. First, we show a numerical scheme to account for relativistic effects in the Global Positioning System. Then, a couple of applications of astrophysical interest are worked out. These are the study of the gravitational collapse of stars and the dynamical evolution of a three-dimensional Einstein-Klein-Gordon field.

Improved neutron and neutrino detection using water Cherenkov detectors loaded with gadolinium has been proposed for potential application in both large and small volume detectors. In this thesis, work performed to determine the effect on transparency resulting from use of GdCl3 in stainless steel constructed water Cherenkov detectors is presented. In addition, results of an experiment performed using a small volume water Cherenkov de- tector are reported. This was the first use of gadolinium loaded water to detect reactor antineutrinos.

The measurement of ground motion is important for a wide range of fields. In physics, advanced experiments can involve precise positioning of components. In civil engineering, engineers need to know the characteristics of ground motion to better design large scale structures, and the study of ground motion form distant earth quakes help geologists understand the structure and dynamics of the earth. Each application requires instruments of different specifications. In this thesis I describe the design, fabrication, assembly, and operation of two broad band force balance seismometers and the associated control software. The design, control elements, and methods used in this project can be extended to other applications were specific criteria are needed in the development of custom seismic sensors. A proportional, integral, and derivative (PID) control scheme was written for the negative feedback loop. Along with the control software, I include a user interface to control the feedback and assist in loop tuning. Closed loop operation of each seismometer was successfully accomplished and the step responses were compared to the step response of an ideal model of the seismometers developed in software. Three parameters are useful in the description of a step response: the settling time, overshoot, and deadtime. The ideal model step response has a settling time of 0.09 seconds and an overshoot of less than 30%. The seismometers exhibit settling times of 1 second and 0.5 seconds and overshoots of 20% and 10%. The ideal model does not exhibit a deadtime but the actual seismometer deadtime was just 30 ms.

Purpose: To determine the sensitivity of a topographic stepwedge procedure to energy variations in a helical tomotherapy system. Method and Materials: Topographic procedures were followed using an aluminum stepwedge suspended in air on the end of the couch for a TomoTherapy HI-Art II system. Exit detector data from these procedures, collected and processed using TomoTherapy quality assurance (TQA) software were used to determine the effective beam energy. Energy sensitivity tests of the technique were made by varying the injector current. Topographic procedures were run daily over the lifetime of an x-ray target. Additionally, water phantom scanning data (lateral profiles and percent depth dose) were measured monthly over the same time period. Results: The attenuation data from the stepwedge demonstrated a smooth decrease in effective energy with time over the life of the target. The energy difference showed dramatic spikes in trending due to target changes and injector current adjustments. Monthly lateral and depth-dose profiles showed variations due to an energy change but not while a target was simultaneously degrading. Analysis of the data show that the stepwedge procedure is capable of detecting a change in the effective energy of greater than 2%. Conclusion: The stepwedge topographic procedure provides a good method to monitor the energy difference over time and may be used to help diagnose impending target failures.

Purpose: The purpose of this work was to investigate the potential of a prototype electron multi-leaf collimator (eMLC) to deliver segmented-field electron conformal therapy (ECT) and to improve dose homogeneity to the planning target volume (PTV) by feathering the abutting edge of the higher energy electron fields. Methods: Software was developed to define the eMLC leaf positions that most closely fit a general field shape. Electron beams (6-20 MeV) using a prototype eMLC were commissioned for the pencil beam dose algorithm in the Pinnacle treatment planning system. A discrete (5-step) Gaussian edge spread function was used to match electron dose penumbras of differing energies at a specified depth in a water phantom. The effect of 1D edge feathering on dose homogeneity was computed and measured for segmented-field ECT treatment plans for three 2D PTVs in a water phantom (depths varied along axis parallel to leaf motion) and one 3D PTV (depth varied along both axes normal to beam). Additionally, the effect of 2D edge feathering was computed for the 3D PTV. Results: 1D discrete Gaussian edge feathering reduced the standard deviation of dose in the 2D PTVs by 34, 34, and 39%. In the 3D PTV, 1D discrete Gaussian edge feathering reduced the standard deviation of dose by 19%. The physical constraints (1-cm leaf width) of the eMLC hindered the 2D application of the feathering solution to the 3D PTV, and the standard deviation of dose increased by 10%. However, 2D discrete Gaussian edge feathering with a smooth-aperture (infinitesimal leaf width) reduced the standard deviation of dose in the 3D PTV by 33%. Conclusions: A 5-step discrete Gaussian edge spread function applied in 2D improves the abutment dosimetry but requires an eMLC leaf resolution better than 1 cm.

Purpose: To compare helical tomotherapy (HT) with mixed beam therapy (electron and IMRT) plans for superficial parotid gland and nasal cavity tumors. Methods: Mixed beam and HT dose plans were developed for five patients with superficial tumors (planning target volume or PTV < 5.5 cm depth), three with parotid gland tumors and two with nasal cavity tumors. Seven mixed beam plans included a 5 or 7-field photon IMRT plan optimized on top of a single en-face 16 or 20 MeV electron beam dose distribution. The ratio of photon to electron beam weights (at depth R100) were 1:0 (IMRT only), 2:1, 1:1, 1:2, 1:3, 1:4, and 0:1 (electrons only). Planning objectives for HT plans were set as closely as possible to those in the mixed beam plans, and were determined using our clinical planning protocol for head and neck cancers. The resulting dose distribution from each plan was evaluated using dose-volume quantities, tumor control probability (TCP), normal tissue complication probability (NTCP), and a clinical evaluation by a radiation oncologist. Results: In general, the HT plans showed better target coverage and dose homogeneity index (DHI) than the mixed beam plans. For the parotid patients, the DHI improved an average of 0.056 and 0.035 for the nasal cavity patients compared to the mixed beam plan. TCP was comparable in all patients. NTCP for the mixed beam plan was generally lower or comparable to HT with the largest improvements seen in the contralateral parotid, eye, and lens. Also, the mixed beam plans yielded more favorable PTV and normal tissue results for a single shallow uniform PTV using a heavier weighted electron to IMRT ratio (1:3 or 1:4 ratio of electron to IMRT). Conclusions: The study showed that while HT plans had better target coverage and dose homogeneity, the mixed beam plans (electron and IMRT) had comparable tumor control probability and have the potential for improving NTCP for distal normal tissue for superficial uniform PTVs.

Robertson, Chad Joseph, B.S. Louisiana Tech University, 2006 Master of Science, Spring Commencement, 2006 Major: Medical Physics and Health Physics Prototype Electron Phantom for Radiographic and Radiochromic Film Dosimetry Thesis directed by Professor Kenneth R. Hogstrom Pages in thesis, 133. Words in abstract, 350 ABSTRACT Purpose: The purpose of this work is to develop a solid electron beam film phantom for use with radiographic film (RGF) and radiochromic film (RCF) to measure relative dose distributions in a principal plane containing the central axis for 6¨C20MeV electron beams. It was hypothesized that relative dose distributions measured using film will agree with corresponding diode measurements within ¡À2% of the central-axis maximum dose or ¡À1mm distance-to-agreement (DTA). Method and Materials: Three prototype film phantoms were designed at Mary Bird Perkins Cancer Center and constructed by Gammex-RMI, Inc. Relative dose measurements, planar (2D) dose distributions containing central-axis, were acquired in the phantom using both Kodak-XV RGF and GafChromic-EBT RCF. Correspondingly, diode measurements were acquired utilizing a Scanditronix-Wellhofer 2D-water phantom. For prototype 3, dose distributions were measured at 100-cm SSD using a 15x15-cm2 field-size at 6, 9, 12, 16, and 20 MeV, as well as 2x2-cm2 and 4x4-cm2 field-sizes at 9 and 16 MeV. Relative dose differences were evaluated with respect to regional criteria of acceptability: (1) high dose, low dose-gradient region (¡Ü 2 % dose), (2) high dose-gradient region (¡Ü 2 mm DTA), and (3) low-dose, low dose-gradient region (¡Ü 2 % dose). Results: RGF depth-dose measurements agreed with diode measurements within all criteria for all measurements conditions. 2D dose distributions were in agreement with over 98% of measured dose points agreeing within ¡À2% dose or ¡À1mm DTA for all energies (6¨C20MeV, 15x15-cm2). RCF depth-dose measurements agreed for all measurement conditions in all regions excluding the build-up region (<1¨C2cm depth), where measurements were approximately 3¨C4% low. 2D dose distributions reflected differences seen in the depth-doses with 90% of data points within criteria. Conclusion: With appropriate modifications, the prototype 3 phantom is capable of accurately measuring relative electron dose distributions using RGF sufficiently for clinical use. RCF measurements acquired in the same phantom consistently underestimated diode measurements by 3¨C4% at depths <2-cm. The cause of this systematic error, believed to be a combination of film-edge misalignment and RCF depth-dependency, must be resolved before prototype phantom 3 with appropriate modifications would be acceptable for clinical use.