Design and Performance of Fast, a Tracker for Antiproton Physics

The antiproton annihilation cross section on different nuclei was measured by the OBELIX collaboration at LEAR (CERN) during the '80s and '90s; its dependence on the atomic mass number A, in the momenta range 200-800 MeV/c, was found to be A^2/3. Low statistics measurements at lower energies (60 MeV/c) showed some anomalies that suggested the need for new experiments to investigate about them and to increase statistics. For these reasons, a new pbar cross section experiment has been proposed at the end of 2004, and a scintillating fiber tracker (FAST, Fiber Antiproton Scintillating Tracker) has been built to perform a direct annihilation cross section measurement at the Antiproton Decelerator (AD) at CERN. This thesis work decribes the design and the development of the detector, its assembly and commissioning phase results. The tests with a prototype and the comparisons with a Montecarlo simulation are reported too. In the last part, the data taking setups of September 2006 and July 2007 are presented

Optical Channeling of Low Energy Antiprotons in Thin Crystal Targets

A relevant aspect of the interactions between charged fermions and crystal targets is coherence, which can exist at both classical and quantum levels. In the case of antiprotons crossing crystal targets, there are theories and measurements of classical-level coherence effects, in particular, channeling effects. For the present study, we assume the existence of a low-energy regime where the electrostatic interactions between an antiproton and the crystal atoms lead to a local loss in the beam flux as their leading effect. We expect this assumption to be well-justified for antiproton (p over bar ) energies below 100 eV, with a progressive transition to a standard "Rutherford regime" in the energy range 100-1000 eV. Under these conditions, the target can be treated as an optical absorber with a periodical structure, which can be simplified by considering a multi-layer planar structure only. As in standard optics, wave absorption is accompanied by interference and diffraction. Assuming sub-nanometer ranges for the relevant parameters and a realistic angular spread for the antiproton beam, we find narrow-angle focusing effects that reproduce the classical channeling effect at a qualitative level. We also find that diffraction dominates over interference, although this may strongly depend on the target details

A hydrogen beam to characterize the ASACUSA antihydrogen hyperfine spectrometer

The antihydrogen programme of the ASACUSA collaboration at the antiproton decelerator of CERN focuses on Rabi-type measurements of the ground-state hyperfine splitting of antihydrogen for a test of the combined Charge-Parity-Time symmetry. The spectroscopy apparatus consists of a microwave cavity to drive hyperfine transitions and a superconducting sextupole magnet for quantum state analysis via Stern-Gerlach separation. However, the small production rates of antihydrogen forestall comprehensive performance studies on the spectroscopy apparatus. For this purpose a hydrogen source and detector have been developed which in conjunction with ASACUSA's hyperfine spectroscopy equipment form a complete Rabi experiment. We report on the formation of a cooled, polarized, and time modulated beam of atomic hydrogen and its detection using a quadrupole mass spectrometer and a lock-in amplification scheme. In addition key features of ASACUSA's hyperfine spectroscopy apparatus are discussed.

VIABILIDADE DA HÉLICE CONTÍNUA NA CONSTRUÇÃO CIVIL

The present work will present a brief study on the viability of the use of continuous propeller in civil construction, through a bibliographic review on the stages about this process of execution of deep foundations. It presents the advantages and disadvantages of this process and also how it is carried out. The objective of this study is to verify the constructive aspects of the design of foundations in continuous helix. The methodology is that of bibliographic review. As a result, it became evident that the continuous propeller driven piles are getting closer to being controlled by other, more technical ways, due to the availability of computer systems capable of monitoring the entire executive process, and that, nowadays, there is a representative value on the number of equipment in operation in the civil construction market, which confirms the good performance of this process in the technical environment. Keywords: Continuous propeller; Execution; Foundation.El presente trabajo presenta un breve estudio sobre la factibilidad del uso de hélice continua en la construcción civil, a través de una revisión bibliográfica sobre las etapas de este proceso de implementación de cimentaciones profundas. Presenta las ventajas y desventajas de este proceso y también cómo se lleva a cabo. El objetivo de este estudio es verificar los aspectos constructivos del diseño de cimentación de hélice continua. La metodología es la revisión bibliográfica. Como resultados, se evidenzó que los picos continuos tipo hélice están cada vez más cerca de ser controlados de otras formas más técnicas, debido a la disponibilidad de sistemas informáticos capaces de monitorear todo el proceso ejecutivo, y que, actualmente, ya existe un valor representativo en el número de equipos en operación en el mercado de la construcción, lo que confirma el buen desempeño de este proceso en el entorno técnico.O presente trabalho apresenta um breve estudo referente a viabilidade sobre a utilização da hélice contínua na construção civil, por meio de uma revisão bibliográfica sobre as etapas deste processo de execução das fundações profundas. Apresenta-se as vantagens e desvantagens deste processo e também como é realizado. O objetivo deste estudo é verificar os aspectos construtivos de projeto de fundações em hélice contínua. O metodologia é a de revisão bibliográfica. Como resultados evidenciou-se que as estacas cravadas do tipo hélice contínua estão cada vez mais próximas de serem controladas por outras maneiras mais técnicas, devido à disposição de sistemas de computadores capazes de realizar o monitoramento de todo o processo executivo, e que, atualmente já existem um valor representativo sobre o número de equipamentos em operação no mercado da construção civil, o que confirma a boa atuação deste processo no meio técnico. &nbsp

Measurement of the antiproton–nucleus annihilation cross section at 5.3 MeV

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The upgrade of the ASACUSA scintillating bar detector for antiproton annihilation measurements

Antiproton annihilations on matter nuclei are usually detected by tracking the charged pions emitted in the process. A detector made of plastic scintillating bars have been built and used in the ASACUSA experiment for the last 10 years. Ageing, movements and transports caused stress on the internal mechanical structure and impacted mostly on the optical readout system which was eventually upgraded: the so far used multi-anode photo-multiplier tubes (PMTs) have been replaced by silicon photomultipliers (SiPM) and the front-end electronics had to be adapted to cope with the new signal formation. This work describes the design and operations of the upgrade, as well as the validation tests with cosmic rays

Intravenous thrombolysis in the emergency department for the treatment of acute ischaemic stroke

BACKGROUND AND AIMS: Thrombolytic therapy with intravenous recombinant tissue plasminogen activator (rt-PA) improves outcome in patients with ischaemic stroke treated within 3 h of symptom onset, but its extended implementation is limited. A pilot study was designed to verify whether evaluation of patients with acute ischaemic stroke and their treatment with intravenous rt-PA in the emergency department (ED), followed by transportation to a semi-intensive stroke care unit, offers a safe and effective organisational solution to provide intravenous thrombolysis to acute stroke patients when a stroke unit (SU) is not available. METHODS: After checking for inclusion and exclusion criteria, ED doctors contacted the stroke team with a single page, located family members and urgently obtained computed tomography scan and laboratory tests. A stroke team investigator clinically assessed the patient, obtained written informed consent and supervised intravenous rt-PA in the ED. After treatment, the patient was transferred to the SU for rehabilitation and treatment of complications, under supervision of the same stroke team investigator. RESULTS: 52 patients were treated with intravenous rt-PA within 3 h of symptom onset. 20 patients (38%) improved neurologically after 24 h, the number increased to 30 (58%) after one week. At 3 months 22 patients had a favourable outcome (43%). The 3-month mortality rate was 12%. Symptomatic cerebral haemorrhage was observed in two patients (4%). CONCLUSIONS: Intravenous rt-PA administration in the ED is an effective organisational solution for acute ischaemic stroke when an SU is not established

Antiparticle cloud temperatures for antihydrogen experiments

An analysis of positron and antiproton cloud temperatures under condition similar to those found in antihydrogen experiments.Some simple general trends are brought out in the analysis, which includes the effects of cloud expansion for the first time

Identification of particles with Lorentz factor up to 10410^{4} with Transition Radiation Detectors based on micro-strip silicon detectors

This work is dedicated to the study of a technique for hadron identification in the TeV momentum range, based on the simultaneous measurement of the energies and of the emission angles of the Transition Radiation (TR) X-rays with respect to the radiating particles. A detector setup has been built and tested with particles in a wide range of Lorentz factors (from about $10^3$ to about $4 \times 10^4$ crossing different types of radiators. The measured double-differential (in energy and angle) spectra of the TR photons are in a reasonably good agreement with TR simulation predictions.Comment: 31 pages, 12 figures, paper published on Nuclear Instruments & Methods