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For over a decade now there has been much research into the use of superconductors in X-ray, gamma ray and other particle detectors. Detectors based on superconductor-insulator-superconductor(SIS) and superconductor-insulator-normal metal(SIN) tunnel junctions have been widely developed. To date, the predicted excellent energy resolving ability of such detectors has not been realised. Various energy loss processes have been suggested as possible causes for the failure to obtain energy resolutions close to the thermodynamic and quantum limits predicted. In my experiments, I have used both SIS and SIN tunnel junctions to investigate the transport of quasiparticles and phonons in structures similar to the proposed detector designs. I have used multiple distributed junction geometries to perform injection-detection type experiments. One junction is used to inject quasiparticles and/or phonons into the device structure, whilst the current-voltage characteristic of a second junction is monitored for a response to the injected quasiparticles/phonons. Using this type of experimental set-up, I have measured the transport of non-thermal equilibrium quasiparticles in an epitaxial niobium film. Using a simple random walk model, I have calculated an effective lifetime for quasiparticles. I have not observed the process of quasiparticle mulitiplication that has been observed by other researchers - I attribute this to differences in the microstructure of my devices and comment on the implications of this to possible quasiparticle loss mechanisms. I have investigated the energy transport in a device with a number of SIN tunnel junctions connected to a common normal metal electrode. Phonon transport via the substrate is found to be the dominant coupling process between the tunnel junctions, although the device design can result in some junctions being effectively shielded from the substrate phonons by the common electrode. Finally, the possibilities of using a superconducting heterostructure to control the rate at which quasiparticles recombine and emit phonons have been explored. Excessive recombination is believed to limit the effectiveness of large areas SIN tunnel junctions as thermometers for particle detecting bolometers.

This thesis presents an analysis of the central exclusive production (CEP) of χ_c mesons in proton-proton collisions at a centre-of-mass energy of 8 TeV, using data collected with the LHCb detector corresponding to an effective integrated luminosity of 126.3 ± 4.3 pb⁻¹. Candidate χ_c decays are reconstructed in the K⁺K⁻ and π⁺π⁻ final states, where the final state particles have pseudorapidities between 2.5 and 4.5. The products of the cross sections and branching fractions are measured as σ x B(χ_c0 → K⁺K⁻) = 28.0 ± 2.8 ± 13.9 pb, σ x B(χ_c0 → π⁺π⁻) = 20.3 ± 2.4 ± 8.1 pb, σ x B(χ_c2 → K⁺K⁻) < 12.1 pb, σ x B(χ_c2 → π⁺π⁻) < 10.5 pb, where the first uncertainties are statistical and the second systematic, and limits are set at the 95% confidence level. A major source of systematic uncertainty is the determination of the fraction of the selected data which is CEP rather than inelastic backgrounds. Also described is HERSCHEL, a new subdetector installed at LHCb during the first long shutdown of the LHC. This is a system of forward shower counters which will provide CEP analyses with event-by-event rejection of inelastic backgrounds. The pseudorapidity coverage and detection efficiency of HERSCHEL are determined using Monte Carlo simulations. The pseudorapidity coverage extends to |η&| ≥ 10 due to the showering of collision products at the aperture limit. With a photoelectron threshold yield of 0.2 times the yield in the mean minimum bias event, the detection efficiency for single diffractive events is predicted to be 89% in the forward direction and 91% in the backward direction.

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Orientadores: Ernesto Kemp, Anderson Campos Fauth / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-20T22:56:12Z (GMT). No. of bitstreams: 1 Daniel_Bruno_M.pdf: 8374007 bytes, checksum: 352eb3cb6108ee55f40579c9db6d47a4 (MD5) Previous issue date: 2012 / Resumo: O Observatório Pierre Auger foi desenvolvido com o objetivo de estudar os raios cósmicos de energia ultra-alta (maior que 10¹8 eV ), cujo fluxo é extremamente baixo. Sua configuração híbrida consiste em 1600 detectores de radiação Cherenkov, produzida pela passagem de partículas dos chuveiros atmosféricos na água, e 4 estações com telescópios de fluorescência, que detectam a emissão de luz que ocorre após a excitação das moléculas de nitrogênio da atmosfera. O observatório cobre uma área de cerca de 3000 km² . Neste trabalho será feita uma descrição detalhada dos detectores de superfície e de seu procedimento de reconstrução de eventos, no qual são determinadas a energia e direção de chegada do raio cósmico primário. Serão mostrados alguns resultados da caracterização e teste do tanque Cherenkov de Campinas e análises realizadas sobre o procedimento de reconstrução, nas quais são estudadas as consequências da exclusão de uma estação e o impacto da utilização de tanques irregulares, com fotomultiplicadoras de ganho alterado ou desligadas. Os resultados destes estudos mostram que os procedimentos de calibração e seleção de eventos atualmente utilizados no Observatório Pierre Auger são eficientes, garantindo a qualidade dos dados, mas que algumas modificações poderiam trazer um aumento na taxa de detecção, e também que a configuração mencionada em algumas propostas de expansão do observatório, com apenas uma fotomultiplicadora por tanque, pode reduzir a confiabilidade dos eventos / Abstract: The Pierre Auger Observatory was designed to study the ultra-high energy (> 10¹8 eV ) cosmic rays, whose flux is extremely low. Its hybrid configuration consists on 1600 detectors of Cherenkov radiation, produced by the passage of particles from the air showers by water, and 4 fluorescence telescope stations, to detect light emitted after the excitation of nitrogen molecules of the atmosphere. The observatory covers an area of 3000 km² . This work will give a detailed description of the surface detectors and its event reconstruction procedure, where the energy and arrival direction of the primary cosmic ray is determined. Some results of the characterization and test of the Cherenkov tank of Campinas will be showed, and also some analysis about the reconstruction, with studies of the consequences of the exclusion of a station and the impact of the use of irregular tanks, with photomultiplier\\\'s operating in low gain or turned of. This studies show that the calibration and event selection procedures used at the Pierre Auger Observatory are efficient, providing high quality for the data taken, but some modifications could bring an increase of the detection rate. It is also shown that the configuration for the tanks mentioned in some proposals of expansion of the observatory, with a single photomultiplier by tank, could reduce the con#ability of the events / Mestrado / Física / Mestre em Física

The first 900 four-anode Photomultiplier Tubes (PMTs) have been evaluated for use in the 2013 Hadronic Forward (HF) calorimeter upgrade. HF is a part of the Compact Muon Solenoid (CMS), which is one of the two large general-purpose particle detectors of the Large Hadron Collider (LHC) at CERN in Geneva, Switzerland. HF requires 1728 PMTs. These small tubes are the sensitive light detectors that provide the output signals of HF. Before installing PMTs in HF, their quality control demands need to be satisfied. These tests, done at the University of Iowa, are designed in three categories to test seventeen different parameters for each PMT. The three most basic and most important groups of parameters are: dark current, gain (anode and cathode), and timing. There are secondary tests which are performed on a smaller percentage of the PMTs such as surface uniformity, double pulse and single photo-electron resolution. The PMTs that meet the specifications of HF will be sent to CERN where they are expected to be in use for at least a decade.

Aukštųjų energijų fizikos eksperimentuose plačiai taikomi puslaidininkiniai pin struktūros dalelių detektoriai jonizuojančiosioms dalelėms registruoti. Radiacinė spinduliuotė sukuria defektus medžiagoje ir neigiamai įtakoja detektorių parametrus, todėl būtina charakterizuoti apšvitintus detektorius ieškant būdų, kaip juos patobulinti. Apšvitintų detektorių charakterizavimui taikomi volt-amperinių, volt-faradinių būdingųjų dydžių matavimai ir analizė, giliųjų lygmenų talpinė bei šiluma skatinamų srovių spektroskopija. Tačiau stipriai apšvitintuose detektoriuose, kai defektų koncentracija viršija legirantų koncentraciją bei išauga nuotėkio srovė, šie metodai negali būti taikomi siekiant korektiškai įvertinti radiacinių defektų parametrus. Šiame darbe buvo sukurti modeliai, apibūdinantys slinkties sroves, tekančias detektoriuje dėl elektrinio lauko persiskirstymo keičiantis išorinei įtampai arba elektriniame lauke judant injektuotam krūviui. Šie modeliai buvo pritaikyti naujų metodikų sukūrimui, kurios įgalina įvertinti krūvio pernašos, pagavimo, rekombinacijos/generacijos parametrus stipriai apšvitintuose detektoriuose po apšvitos. Sukurti metodai buvo pritaikyti defektų spektroskopijai ir skersinei žvalgai sluoksninėse struktūrose bei defektų evoliucijos tyrimams apšvitos metu. Disertacijoje pateikti ir aptarti apšvitintų detektorių ir apšvitos metu pasireiškiančios parametrų kaitos rezultatai. Elektronikos grandynuose plačiai naudojami galios pin struktūros diodai, kurie... [toliau žr. visą tekstą] / In high energy physics experiments the semiconductor particle detectors of pin structure are commonly employed for tracking of the ionising particles. However, ionising radiation creates defects and consequently affects the parameters of particle detectors. Therefore, it is necessary to characterize irradiated detectors and search for the new approaches on how to suppress or control the degradation process. Measurements of current-voltage, capacitance-voltage characteristics as well as deep level transient spectroscopy, thermally stimulated currents spectroscopy are employed for the characterization of irradiated particle detectors. At high irradiation fluences when defects concentration exceeds that of dopants, a generation current increases and, thus, the above mentioned techniques can not be applied for the correct evaluation of defect parameters. In this work, models describing displacement currents in detectors due to redistribution of electric field determined by variations of external voltage or a moving charge in electric field are discussed. These models were applied for creation of the advanced techniques which allow evaluating of charge transport, trapping and recombination/generation parameters in heavily irradiated detectors after irradiation. These techniques were applied for the spectroscopy of deep levels associated with defects, for cross-sectional scans within layered junction structures as well as for examination of defects evolution during irradiation. In... [to full text]

In high energy physics experiments the semiconductor particle detectors of pin structure are commonly employed for tracking of the ionising particles. However, ionising radiation creates defects and consequently affects the parameters of particle detectors. Therefore, it is necessary to characterize irradiated detectors and search for the new approaches on how to suppress or control the degradation process. Measurements of current-voltage, capacitance-voltage characteristics as well as deep level transient spectroscopy, thermally stimulated currents spectroscopy are employed for the characterization of irradiated particle detectors. At high irradiation fluences when defects concentration exceeds that of dopants, a generation current increases and, thus, the above mentioned techniques can not be applied for the correct evaluation of defect parameters. In this work, models describing displacement currents in detectors due to redistribution of electric field determined by variations of external voltage or a moving charge in electric field are discussed. These models were applied for creation of the advanced techniques which allow evaluating of charge transport, trapping and recombination/generation parameters in heavily irradiated detectors after irradiation. These techniques were applied for the spectroscopy of deep levels associated with defects, for cross-sectional scans within layered junction structures as well as for examination of defects evolution during irradiation. In... [to full text] / Aukštųjų energijų fizikos eksperimentuose plačiai taikomi puslaidininkiniai pin struktūros dalelių detektoriai jonizuojančiosioms dalelėms registruoti. Radiacinė spinduliuotė sukuria defektus medžiagoje ir neigiamai įtakoja detektorių parametrus, todėl būtina charakterizuoti apšvitintus detektorius ieškant būdų, kaip juos patobulinti. Apšvitintų detektorių charakterizavimui taikomi volt-amperinių, volt-faradinių būdingųjų dydžių matavimai ir analizė, giliųjų lygmenų talpinė bei šiluma skatinamų srovių spektroskopija. Tačiau stipriai apšvitintuose detektoriuose, kai defektų koncentracija viršija legirantų koncentraciją bei išauga nuotėkio srovė, šie metodai negali būti taikomi siekiant korektiškai įvertinti radiacinių defektų parametrus. Šiame darbe buvo sukurti modeliai, apibūdinantys slinkties sroves, tekančias detektoriuje dėl elektrinio lauko persiskirstymo keičiantis išorinei įtampai arba elektriniame lauke judant injektuotam krūviui. Šie modeliai buvo pritaikyti naujų metodikų sukūrimui, kurios įgalina įvertinti krūvio pernašos, pagavimo, rekombinacijos/generacijos parametrus stipriai apšvitintuose detektoriuose po apšvitos. Sukurti metodai buvo pritaikyti defektų spektroskopijai ir skersinei žvalgai sluoksninėse struktūrose bei defektų evoliucijos tyrimams apšvitos metu. Disertacijoje pateikti ir aptarti apšvitintų detektorių ir apšvitos metu pasireiškiančios parametrų kaitos rezultatai. Elektronikos grandynuose plačiai naudojami galios pin struktūros diodai, kurie... [toliau žr. visą tekstą]