Research and development study on multimode system applications in the area of time of flight and coincidence measurements

Technical specifications for multimode digital storage device, and applications to time of flight and coincidence measurement

JUNO Conceptual Design Report

The Jiangmen Underground Neutrino Observatory (JUNO) is proposed to determine the neutrino mass hierarchy using an underground liquid scintillator detector. It is located 53 km away from both Yangjiang and Taishan Nuclear Power Plants in Guangdong, China. The experimental hall, spanning more than 50 meters, is under a granite mountain of over 700 m overburden. Within six years of running, the detection of reactor antineutrinos can resolve the neutrino mass hierarchy at a confidence level of 3-4$\sigma$, and determine neutrino oscillation parameters $\sin^2\theta_{12}$, $\Delta m^2_{21}$, and $|\Delta m^2_{ee}|$ to an accuracy of better than 1%. The JUNO detector can be also used to study terrestrial and extra-terrestrial neutrinos and new physics beyond the Standard Model. The central detector contains 20,000 tons liquid scintillator with an acrylic sphere of 35 m in diameter. $\sim$17,000 508-mm diameter PMTs with high quantum efficiency provide $\sim$75% optical coverage. The current choice of the liquid scintillator is: linear alkyl benzene (LAB) as the solvent, plus PPO as the scintillation fluor and a wavelength-shifter (Bis-MSB). The number of detected photoelectrons per MeV is larger than 1,100 and the energy resolution is expected to be 3% at 1 MeV. The calibration system is designed to deploy multiple sources to cover the entire energy range of reactor antineutrinos, and to achieve a full-volume position coverage inside the detector. The veto system is used for muon detection, muon induced background study and reduction. It consists of a Water Cherenkov detector and a Top Tracker system. The readout system, the detector control system and the offline system insure efficient and stable data acquisition and processing.Comment: 328 pages, 211 figure

Apparatus to control and visualize the impact of a high-energy laser pulse on a liquid target

We present an experimental apparatus to control and visualize the response of a liquid target to a laser-induced vaporization. We use a millimeter-sized drop as target and present two liquid-dye solutions that allow a variation of the absorption coefficient of the laser light in the drop by seven orders of magnitude. The excitation source is a Q-switched Nd:YAG laser at its frequency-doubled wavelength emitting nanosecond pulses with energy densities above the local vaporization threshold. The absorption of the laser energy leads to a large-scale liquid motion at timescales that are separated by several orders of magnitude, which we spatiotemporally resolve by a combination of ultra-high-speed and stroboscopic high-resolution imaging in two orthogonal views. Surprisingly, the large-scale liquid motion at upon laser impact is completely controlled by the spatial energy distribution obtained by a precise beam-shaping technique. The apparatus demonstrates the potential for accurate and quantitative studies of laser-matter interactions.Comment: Submitted to Review of Scientific Instrument

A sub-μs accuracy GPS alternative using electrical transmission grids as precision timing networks

It is widely recognised that over-reliance on GNSS (e.g GPS) for time synchronisation represents an acute threat to modern society, and a diversity of alternatives are required to mitigate the threat of an outage. This paper proposes a GNSS alternative using time dissemination over national scale transmission or distribution networks. The method utilises the same frequency bandwidth and coupling technology as established power line carrier technology in conjunction with modern chirp Spread Spectrum modulation. The basis of the method is the transmission of a time synchronised chirp from a central substation, coupled into the aerial modes of the transmission line. During GNSS operation, all substations can estimate the time of flight by correlating the received chirp with a time-synchronised local copy. During GNSS outage, time sychronisation to the central substation is maintained by correcting for the precalculated time of flight. It is shown that recent advances in chirp spread spectrum allow for a computationally efficient algorithm with the capacity to compute hundreds of thousand of chirp correlations every second, facilitating timing accuracy which satisfies the majority of smart grid applications. ATP-EMTP simulations of the method on large transmission networks demonstrate sub-μs timing accuracy even in the presence of low SNR and impulsive noise. An FPGA prototype demonstrates experimentally sub-μs accuracy for time dissemination over a distance of 700 m. Averaging over time is shown to facilitate satisfactory performance down to -20dB, which could extend the range of the system to a national scale and a time dissemination network invulnerable to wireless spoofing and jamming attack vectors

The FlashCam camera for CTA: trigger verification and fluorescence light detection capabilities

The next generation of Gamma-ray observatory - Cherenkov Telescope Array (CTA) - aims at improving the detection capabilities at a broad energy range of the gamma-ray spectrum by a factor of 10 in sensitivity. The FlashCam camera is one of the camera types mounted on the medium-sized telescopes (MST) of CTA, responsible for the observation of the core energy range between 150 GeV and 5 TeV. The first part of this thesis assumed the task of verifying the trigger system of FlashCam. Studies of the trigger efficiency and night-sky background light trigger response were performed, whilst also improving the Monte-Carlo description of the detector. The second part was dedicated to the research of the fluorescence light detection capabilities of the full 25 FlashCam-MST sub-array using simulations. A trigger logic was developed, which allows the detection of air showers with primary energies higher than 1 PeV through their fluorescence emission. The effective area of this detection method was determined and the angular resolution using a shower axis reconstruction calculated. The combination of these individual studies allowed the estimation of the sensitivity on point-like gamma-ray sources emitting in the energy range above 1 PeV

High-Power Laser Systems for Driving and Probing High Energy Density Physics Experiments

This thesis describes the construction of a hybrid OPCPA and Nd:Glass based laser system to provide advanced diagnostic capabilities for the MAGPIE pulsed power facility at Imperial College London. The laser system (named Cerberus) is designed to provide one short pulse 500 fs beam for proton probing and two long pulse beams, one for x-ray backlighting and one for Thomson scattering. The aim of this project is to accurately determine plasma parameters in a range of demanding experimental environments. The thesis is split into two sections; the first section provides details about the design and implementation of the laser system while the latter chapters present experimental data obtained on the MAGPIE facilty. The front end for the laser system is based on optically synchronised Optical Parametric Chirped Puled Amplification (OPCPA) which is supplemented by large aperture flashlamp pumped Nd:Glass power amplifiers in the latter stages to increase the energy to the Joule level. The use of optical parametric amplifiers (OPAs) in the pre-amplifier stages reduces gain narrowing, B-integral and improves contrast. Simulations of the dispersive optics for the Chirped Pulse Amplification (CPA) system are described in detail. Spatially resolved Thomson scattering was used to measure temperature and velocity of ablation streams in aluminium and tungsten cylindrical wire arrays. The measurements show a peak ow velocity of 120 km/s and agree well with 3D MHD simulations for the case of aluminium. There is discrepancy with the tungsten data caused by the difficulty in handling of collisionality calculations. Novel data showing the self-emission of ions from tungsten radial wire arrays is presented as a key step towards laser driven proton probing of MAGPIE. It is observed that the bulk of the emission corresponds to low energy protons with energies of ~ 100 keV. Protons with energy > 600 keV were observed to emanate from the collapsing magnetic jet using a coded aperture camera. These results offer interesting new prospects in diagnosing wire arrays.Open Acces

Development of an ultrafast laser ultra-precision machining platform

Ultra-precision manufacturing is commonplace in today’s society. It is used in a huge number of applications from electronics, medical devices to energy devices. Most devices manufactured using ultra-precision methods are made in high quantities where the volume of the components is required to outweigh the cost of the production equipment. However, there are few technologies targeting the manufacture of prototypes or small batches and those that are costly in terms of time or resources. Thus, there is a demand for a high speed, flexible manufacturing platform that is capable of ultra-precise manufacture. Currently, manufacturing techniques using ultrafast lasers are limited with regards to accuracy and repeatability. This body of work investigates how to develop an ultra-precision ultrafast laser manufacturing platform. From literature it was found that there are a significant number of avenues that could be investigated to improve the precision of an ultrafast laser machining process. This included the integration of metrology to perform closed-loop processing, studies of laser stability, new machining strategies and the effect of processing on plume formation. A significant proportion of the research presented was focused on the development of the ultra-precision platform. This work was carried out to provide a basis for this research but also for those that will use the platform in the future. One of the key outputs from this development was a graphical user interface that integrated with the range of devices on the platform such as the laser, 5-axis stage and beam diagnostic tools. This interface provides methods for automatic tilt correction, autofocus for the laser, angular ablation machining methods and other diagnostic tools. The interface is setup to capture the required data to provide traceability and diagnostics on the laser machining process. This aided the research carried out into improving the accuracy and repeatability of the laser-based process. First, an investigation into the characteristics of the laser installed on the ultra-precision platform was undertaken to determine the long-term stability of the laser with regards to the pointing stability, power stability and beam diameter stability. These characteristics are significant because they all affect the fluence at the focal spot which is responsible for ablating material. Variance in any of those parameters can have an effect and therefore influence the accuracy and repeatability of the process. The effect of duty cycle on power repeatability and the implications of this on machining was examined. Finally, a simulation was created to demonstrate the effect of laser stability on quality of machining. The ability to machine on angled planes enabled an investigation of the effect of angle on plume formation and the ablation threshold of the material. The ablation threshold for silicon was found at angles between normal and 45 degrees. It was found that the threshold could not be correlated with change of incident angle on the area of the focal spot. A range of different powers and angles were captured using the holographic camera and the effect on plume development was assessed. Overall, a range of tasks was completed which enabled several developments of the ultra-precision platform. These included in-process monitoring, the establishment of a novel machining strategy, and the capture of the effect of angular ablation on plume formation using a holographic camera. The platform is now placed to continue further development and integrate with other metrology technologies to provide closed-loop machining capabilities which will lead into a laser-based process which will be used for MEMS and similar device manufacture.EPSR

Constraints on Lorentz Invariance Violation through the study of energy-dependent photonic time dispersion utilizing observations from current gamma-ray instruments

La Gravedad Cuántica podría establecerse como el puente que conectase las leyes de la física que rigen los fenómenos a mayor y a menor escala en el universo - actualmente explicados por la Relatividad General y la Teoría Cuántica de campos, respectivamente - que desembocaría en la integración, dentro de una única teoría, de todos los fenómenos físicos: la llamada "Teoría del todo". Pese a que la Relatividad General y la Teoría Cuántica de Campos han sido intensamente probadas dentro de sus dominios de aplicabilidad, todavía presentan ciertas incompatibilidades fundamentales que han derivado en el continuo, aunque todavía inacabado, esfuerzo de definir teóricamente el comportamiento cuántico del campo gravitatorio, esfuerzo que comenzó en 1930. Desde ese momento y hasta hoy en día, han surgido un gran número de teorías de la Gravedad Cuántica, pero todavía no se ha alcanzado un marco teórico definitivo capaz de integrar simultáneamente todas las fuerzas fundamentales.Un punto de partida para discriminar entre las diferentes teorías, así como para continuar impulsando el desarrollo teórico, es la búsqueda de las posibles consecuencias físicas que generaría el hecho de que el campo gravitatorio tuviese un comportamiento cuántico. Entre estas posibles consecuencias, se encuentra la modificación de simetrías asociadas al espacio-tiempo, en particular la desviación respecto de la simetría de Lorentz, cuyo estudio ha dado lugar a uno de los campo de investigación más activos dentro de la fenomenología asociada a la Gravedad Cuántica.La escala de energía en la que los fenómenos asociados a un campo gravitatorio cuántico comenzarían a ser relevantes, se sitúa en torno a la escala de Planck. Dicha energía está varios órdenes de magnitud por encima del rango de sensibilidad de la generación actual de experimentos. Sin embargo, pequeñas desviaciones de la simetría de Lorentz integradas en largas distancias, fenómeno conocido como violación de la invarianza Lorentz, podrían producir efectos relevantes a energías más bajas, dentro del alcance experimental. Uno de los tests que tratan de medir estas pequeñas desviaciones se denomina "Tiempo de vuelo" ("Time-of-Flight" en inglés). Dicho test trata de buscar desviaciones dependientes de la energía en la velocidad de propagación de fotones, con respecto a su velocidad teórica, es decir, la velocidad de la luz en el vacío.La presente tesis se centra en esta rama de la fenomenología de Gravedad Cuántica, estudiando las desviaciones mencionadas, mediante rayos gamma de muy alta energía, procedentes de fuentes lejanas. Los rayos gamma son ideales para este tipo de estudio, puesto que viajan a través del universo sin que les afecten los campos magnéticos. Además, han sido detectados procedentes de fuentes muy distantes (z=1) y presentan energías muy altas, hasta varias decenas de TeV. Estos dos últimos factores están directamente relacionados con la intensidad del efecto que produce la ruptura de la invariancia Lorentz y, por tanto, con la capacidad de detectar estas pequeñas desviaciones de forma experimental.En esta tesis se presentan resultados obtenidos usando el método de "Tiempo de vuelo" y haciendo uso de los rayos gamma procedentes de la galaxia lejana Mrk 421, detectados durante un periodo de muy alta actividad por los telescopios MAGIC en 2014. La emisión detectada está formada por cientos de eventos que alcanzan energías de hasta 30 TeV, convirtiéndola en una de las más energéticas jamás empleadas para tests de "Tiempo de vuelo" hasta la fecha. El análisis de esta emisión para detectar pequeñas desviaciones en la velocidad de los fotones se ha llevado a cabo con diversas técnicas, algunas de ellas desarrolladas como parte de este trabajo. Los resultados obtenidos se emplean para acotar la escala de energía esperada para Gravedad Cuántica.Adicionalmente, se presentan los resultados del primer análisis combinado empleando la técnica de "Tiempo de vuelo". Este análisis ha sido desarrollado en colaboración entre todos los telescopios terrestres Cherenkov actualmente en funcionamiento (H.E.S.S., MAGIC y VERITAS) y hace uso simultáneo de datos de varias fuentes detectadas por los diferentes telescopios.El hecho de combinar diferentes fuentes en un análisis, permite discriminar entre efectos temporales debidos a la ruptura de la invarianza Lorentz frente a otros efectos temporales relativos a las propias fuentes. Sin embargo, esta combinación también requiere un gran control de las incertidumbres asociadas a la forma de detección de cada experimento. La siguiente generación de telescopios terrestres Cherenkov, el observatorio llamado "Cherenkov Telescope Array", proveerá muchas nuevas fuentes con emisiones que permitan estudiar más en profundidad la ruptura de invariancia Lorentz. Asimismo, presentará avances técnicos tales como mejoras en la resolución angular y de energía de estos telescopios. Estos factores desembocarán en una disminución de las incertidumbres sistemáticas que de seguro llevará a una mejora en los resultados obtenidos hasta la fecha.Esta tesis está dividida en 6 capítulos y un anexo. El capítulo 1 introduce el tema de Gravedad Cuántica, así como la evolución y los tipos de teorías propuestos a lo largo de la historia, centrándose especialmente en la ruptura de la invariancia Lorentz y los diferentes tests experimentales que tratan de estudiarla. El capítulo 2 presenta el campo de la astrofísica conocido como astronomía gamma. En él se tratan los mecanismos de producción de este tipo de radiación, las técnicas empleadas para su detección, así como los diferentes tipos de fuentes que la generan. El capítulo 3 se centra en los tests experimentales que buscan señales de ruptura de invariancia Lorentz y que son llevados a cabo por telescopios terrestres Cherenkov, con un énfasis especial en los tests de "Tiempo de vuelo". El capítulo 4 describe en detalle los telescopios terrestres Cherenkov llamados MAGIC, sus componentes físicos y el procedimiento seguido para la reducción sus datos. El capítulo 5 contiene los resultados originales de esta tesis, obtenidos mediante el método de "Tiempo de vuelo" y usando los datos de una emisión destacada de Mrk 421. El capítulo detalla cómo se seleccionó la fuente para el estudio, los datos sobre la observación y una descripción minuciosa de los diferentes métodos de análisis. Al final del capítulo, se presentan los resultados así como las conclusiones que se derivan de ellos. Por último, el capítulo 6 contiene los resultados del análisis de la ruptura de la invariacia Lorentz, realizado en colaboración por todos los telescopios terrestres Cherenkov activos en la actualidad. El capítulo muestra las diferentes fuentes empleadas, el método de análisis y su calibración, y termina con los resultados y los siguientes planes para la colaboración.El anexo A contiene el trabajo desarrollado como contribución en la construcción del primer telescopio del nuevo observatorio "Cherenkov Telescope Array", basado en el diseño de las calibraciones del sistema de trigger de dicho telescopio. Puesto que el tema y los objetivos de dicho trabajo difieren considerablemente del hilo conductor del resto de la tesis, se ha decidido separarlo del cuerpo principal y situarlo en un anexo. Sin embargo, esta tarea ha requerido una cantidad considerable del tiempo dedicado a esta tesis y ha supuesto una parte importante en la formación del autor, por lo que se considera que merece su lugar en este trabajo.<br /