Commissioning and Calibration of the ALICE TPC

ALICE (A Large Ion Collider Experiment) is the dedicated heavy ion experiment at the Large Hadron Collider at CERN. The main tracking device of ALICE is a large volume TPC. The milestones of the TPC commissioning as well as the current status of the detector calibration are presented. The obtained resolutions in transverse momentum, position as well as in specific energy loss (dE/dx) are presented and results from noise and electron drift velocity measurements are addressed.Comment: 4 pages, 4 figures- To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse

Nuclear modification of J/psi production in Pb-Pb collisions at sqrt(s_NN)=2.76 TeV

ALICE is the dedicated heavy-ion experiment at the LHC. Due to the unique particle identification capabilities of the central barrel detectors (|eta|<0.9), J/psi can be measured in the di-electron channel in the very demanding environment of central Pb-Pb collisions at the LHC. In addition J/psi are measured at forward rapidity (2.5<y<4) with a dedicated muon spectrometer. ALICE is the only LHC experiment with an acceptance for J/psi that reaches down to p_T=0 at both, mid- and forward rapidity. Preliminary results on the nuclear modification factor of the inclusive J/psi production at mid- and forward rapidity in Pb-Pb collisions at sqrt(s_NN)=2.76 TeV are presented.Comment: 4 pages, 7 figures, proceedings for the 5th international conference on hard and electromagnetic probes of high-energy nuclear collisions (Hard Probes 2012), Cagliari, Ital

Measurement of the J/psi inclusive production cross-section in pp collisions at sqrt(s)=7TeV with ALICE at the LHC

ALICE measures the J/psi production at mid-rapidity (|y| < 0.9) in the di-electron decay channel as well as at forward rapidity (2.5 < y < 4.0) in the di-muon decay channel. In both channels the acceptance goes down to zero transverse momentum. We present the rapidity dependence of the inclusive J/psi production cross-section and transverse momentum spectra.Comment: Proceedings: Rencontres de Moriond QCD and High Energy Interactions 201

Online Calibration of the TPC Drift Time in the ALICE High Level Trigger

ALICE (A Large Ion Collider Experiment) is one of four major experiments at the Large Hadron Collider (LHC) at CERN. The High Level Trigger (HLT) is a compute cluster, which reconstructs collisions as recorded by the ALICE detector in real-time. It employs a custom online data-transport framework to distribute data and workload among the compute nodes. ALICE employs subdetectors sensitive to environmental conditions such as pressure and temperature, e.g. the Time Projection Chamber (TPC). A precise reconstruction of particle trajectories requires the calibration of these detectors. Performing the calibration in real time in the HLT improves the online reconstructions and renders certain offline calibration steps obsolete speeding up offline physics analysis. For LHC Run 3, starting in 2020 when data reduction will rely on reconstructed data, online calibration becomes a necessity. Reconstructed particle trajectories build the basis for the calibration making a fast online-tracking mandatory. The main detectors used for this purpose are the TPC and ITS (Inner Tracking System). Reconstructing the trajectories in the TPC is the most compute-intense step. We present several improvements to the ALICE High Level Trigger developed to facilitate online calibration. The main new development for online calibration is a wrapper that can run ALICE offline analysis and calibration tasks inside the HLT. On top of that, we have added asynchronous processing capabilities to support long-running calibration tasks in the HLT framework, which runs event-synchronously otherwise. In order to improve the resiliency, an isolated process performs the asynchronous operations such that even a fatal error does not disturb data taking. We have complemented the original loop-free HLT chain with ZeroMQ data-transfer components. [...]Comment: 8 pages, 10 figures, proceedings to 2016 IEEE-NPSS Real Time Conferenc

Measurement of spark probability of GEM detector for CBM muon chamber (MUCH)

The stability of triple GEM detector setups in an environment of high energetic showers is studied. To this end the spark probability in a shower environment is compared to the spark probability in a pion beam.Comment: 5 pages, 10 figure

Tools for Modelling and Identification with Bond Graphs and Genetic Programming

The contributions of this work include genetic programming grammars for bond graph modelling and for direct symbolic regression of sets of differential equations; a bond graph modelling library suitable for programmatic use; a symbolic algebra library specialized to this use and capable of, among other things, breaking algebraic loops in equation sets extracted from linear bond graph models. Several non-linear multi-body mechanics examples are pre- sented, showing that the bond graph modelling library exhibits well-behaved simulation results. Symbolic equations in a reduced form are produced au- tomatically from bond graph models. The genetic programming system is tested against a static non-linear function identification problem using type- less symbolic regression. The direct symbolic regression grammar is shown to have a non-deceptive fitness landscape: perturbations of an exact pro- gram have decreasing fitness with increasing distance from the ideal. The planned integration of bond graphs with genetic programming for use as a system identification technique was not successfully completed. A catego- rized overview of other modelling and identification techniques is included as context for the choice of bond graphs and genetic programming

Inbetriebnahme und Kalibrierung der ALICE-TPC

ALICE (A Large Ion Collider Experiment), is the dedicated heavy-ion experiment at the Large Hadron Collider (LHC) at CERN. It is optimised to reconstruct and identify the particles created in a lead-lead collision with a centre of mass energy of 5.5TeV. The main tracking detector is a large-volume time-projection chamber (TPC). With an active volume of about 88m^3 and a total readout area of 32.5m^2 it is the most challenging TPC ever build. A central electrode divides the 5m long detector into two drift regions. Each readout side is subdivided into 18 inner and 18 outer multi-wire proportional read-out chambers. The readout area is subdivide into 557568 pads, where each pad is read out by and electronics chanin. A complex calibration is needed in order to reach the design position-resolution of the reconstructed particle tracks of about 200um. One part of the calibration lies in understanding the electronic-response. The work at hand presents results of the pedestal and noise behaviour of the front-end electronics (FEE), measurements of the pulse-shaping properties of the FEE using results obtained with a calibration pulser and measurements performed with the laser-calibration system. The data concerned were taken during two phases of the TPC commissioning. First measurements were performed in the clean room where the TPC was built. After the TPC was moved underground and built into the experiment, a second round of commissioning took place. Noise measurements in the clean room revealed a very large fraction of pads with noise values larger than the design specifications. The unexpected high noise values could be explained by the 'ground bounce' effect. Two modifications helped to reduce this effect: A desynchronisation in the the start of the readout of groups of channels and a modification in the grounding scheme of the FEE. Further noise measurements were carried out after the TPC has been moved to the experimental area underground. Here even a larger fraction of channels showed too large noise values. This could be traced back to a common mode current injected by the electronics power supplies. To study the shaping properties of the FEE a calibration pulser was used. To generate signals in the FEE a pulse is injected to the cathode wires of the read-out chambers. Due to manufacturing tolerances slight channel-by-channel variations of the shaping properties are expected. This effects the determination of the arrival time as well as the measured integral signal of the induced charge and has to be corrected. The measured arrival time variations follow a Gaussian distribution with a width (sigma) of 6.2ns. This corresponds to an error of the cluster position of about 170um. The charge variations are on the level of 2.8%. In order to reach the intrinsic resolution on the measurement of the specific energy loss of the particles (6%) those variations have to be taken into account. The photons of the laser-calibration system are energetic enough to emit photo electrons off metallic surfaces. Most interesting for the detector calibration are photo electrons from the central electrode. The laser light is intense enough to get a signal in all readout channels of the TPC. Since the central electrode is a smooth surface, differences in the arrival time between sectors reveal mechanical displacements of the readout sectors and can be used to correct for this effect. In addition the measurements can be used to determine the electron drift velocity in the TPC gas. The drift velocity measurements have shown a vertical as well as a radial gradient. The first can be explained by the temperature gradient, which naturally builds up in the 5m high detector. The second gradient is most probably caused by a relative conical deformation of the readout plane and the central electrode.ALICE (A Large Ion Collider Experiment), eines der Experimente am LHC (Large Hadron Collider) des europäischen Kernforschungszentrums CERN, ist darauf optimiert, die geladenen primären und sekundären Teilchen, die in einer Blei-Blei-Kollision bei einer Schwerkpunktenergie von 5.5TeV entstehen, einzeln zu rekonstruieren und zu identifizieren. Der Hauptdetektor für die Spurrekonstruktion der in der Kollision entstehenden Teilchen ist mit einem aktiven Volumen von ca. 88m^3 die größte bis jetzt gebaute Spurendriftkammer (Time-Projection Chamber - TPC). Eine zentrale Elektrode teilt den 5m langen Detektor in zwei Ausleseseiten, deren Enden mit jeweils 18 inneren und 18 äußeren Vieldraht-Proportionalkammern bestückt sind. Die insgesamt 32.5m^2 umfassende Auslesefläche der Kammern ist dabei in 557568 einzelne Ausleseeinheiten (Pads) segmentiert. Um die vorgesehene Präzision der Rekonstruierten Spuren von ca. 200um zu erreichen, ist eine komplexe Kalibrierung notwendig. Ein Teil dieser Kalibrierung umfasst eine genaue Kenntnis der von der Elektronik erzeugten Signale. Die vorliegende Arbeit beschäftigt sich mit der Bestimmung der Pedestalwerte und der Analyse des Elektronikrauschens der verwendeten 'Front-End Elektronik' (FEE). Zur Bestimmung des Pulsformverhaltens jedes einzelnen Auslesekanals wurden Messungen mit einem Kalibrations-Pulser durchgeführt und ausgewertet. Des Weiteren wurden Daten analysiert, die mit dem Laser-Kalibrations-System der TPC erzeugt wurden. Die analysierten Daten wurden während zwei Phasen der Inbetriebnahme genommen. Die ersten Messungen fanden in einem Reinraum, in dem der Detektor auch bereits montiert wurde. Weitere Messungen wurden durchgeführt nachdem der Detektor in der unterirdischen Kaverne im ALICE-Experiment eingebaut worden ist. Bei den Messungen im Reinraum wurde festgestellt, dass ein sehr großer Anteil der Auslesekanäle ein zu hohes Elektronikrauschen aufweist. Das unerwartet hohe Rauschen konnte durch den 'ground bounce' Effekt erklärt werden. Zwei Maßnahmen konnten diesen Effekt wesentlich verringern. Zum einen bietet die Elektronik die Möglichkeit die Auslese einzelner Gruppen von Kanälen zu einem verschiedenen Zeitpunkt zu starten, um den momentan fließenden Strom zu verringern. Zum anderen konnte das Rauschen weiter reduziert werden, indem die Erdung der FEE verbessert wurde. Durch diese beiden Änderungen wurde das Rauschen auf den erforderlich Wert gesenkt. Nachdem die TPC im Experiment eingebaut wurde ergaben die Messungen des Elektronikrauschens abermals zu hohe Werte. Dies konnte auf die Verwendeten Netzgeräte zurück geführt werden, die eine Gleichtaktstörung außerhalb der Spezifikationen aufwies. Mit Hilfe eines Kalibrations-Pulsers, der ein Signal auf die Kathodendrahtebene der Vieldraht-Proportionalkammern einspeist, wurde das Pulsformverhalten der Elektronik untersucht. Bedingt durch den Herstellungsprozess variiert dieses von Kanal zu Kanal. Das wirkt sich sowohl auf die Bestimmung der Ankunftszeit, als auch der gemessenen Ladung aus. Mit den Kalibrations-Pulser-Messungen lassen sich die Daten auf diese beiden Effekte hin korrigieren. Die gemessenen Variationen der Ankunftszeit folgen einer Normalverteilung mit einer Breite (Sigma) von 6.2ns. In der Ortsauflösung der Elektronen-Cluster entlang der Teilchenspur entsteht dadurch ein Fehler von etwa 170um. Für die gemessene relative Ladungsverteilung erhält man ebenfalls eine Normalverteilung. Ihre Breite entspricht einer relativen Abweichung von 2.8%. Um die intrinsische Auflösung des spezifischen Energieverlustes von ca. 6% zu erreichen, müssen die Variationen berücksichtigt werden. Die Photonen des Laser-Kalibrations-Systems sind energetisch genug, um beim Auftreffen auf metallische Oberflächen Photoelektronen zu erzeugen. Interessant für die Detektorkalibration sind Photoelektronen von der Zentralelektrode. Die ausgelösten Elektronen sind so zahlreich, dass in jedem Auslesepad ein Signal gemessen werden kann. Da die Zentralelektrode eine stetige Fläche ist, können Sprünge in der Ankunftzeitmessung als Fehljustage der Auslesekammern interpretiert und anschließend darauf korrigiert werden. Des Weiteren ist es möglich mit Hilfe der Daten der Zentralelektrode die mittlere Elektronen-Driftgeschwindigkeit sowie Driftgeschwindigkeitsgradienten zu messen. Die Messungen zeigten einen vertikalen Driftgeschwindigkeitsgradienten, sowie eine radiale Abhängigkeit in der Ankunftszeitmessung. Der erste Effekt lässt sich durch die Temperaturabhängigkeit der Driftgeschwindigkeit erklären: Auf Grund der Höhe der TPC bildete sich ein Temperaturgradient. Der zweite Effekt wird sehr wahrscheinlich von einer relativen konische Verformung der Ausleseebene zur Zentralelektrode verursacht

Intervenţii şi strategii pentru renunţarea la fumat

This Best Practice Information Sheet has been derived from a commissioned review undertaken by The Joanna Briggs Institute. This review sought to identify existing systematic reviews on smoking cessation interventions and strategies. Fifteen systematic reviews were identified that met the inclusion criteria and were assessed as being of sufficient methodological quality. Reviews specific to paediatric and obstetric patients were not included in this review.Assisting patients to quit smoking is complex and requires a systematic and  multifaceted approach. The benefits of promoting smoking cessation particularly amongst hospital inpatients are well recognised not only for the individual concerned but the whole community. There are a range of interventions and strategy alternatives that are supported by quality research based evidence. Although they may be effective in isolation, a program of multiple interventions including appropriate pharmacotherapy with advice and support tailored to the individual, are more likely to achieve success. These interventions can only be effectively applied if there are systems in place to screen, assess and follow up patients who wish to quit smoking.Keywords: smoking cessation, intervention, strategies, background, screening, advice to quit, treatment formats, follow-up, assessment, procedures, recommendations.Content available only in Romanian

The professional journey of Saudi nurse graduates: A lived experience

Objective: To illuminate the lived experience of Saudi Nurse graduates during their early years in the workplace as professional nurses encompassing their experiences from being nurse students, preparations to become registered nurses, their struggles from being a student to a professional nurse, their cultural competence towards colleagues and patients in their new workplace, their impression of Nursing as a profession and other challenges they faced in especially on language and communication with their patients and colleagues. Methods: An interpretive phenomenological inquiry was utilized to inquire and discover the lived experiences of Saudi Nurse graduates to their job as nurses in different hospitals in Riyadh, Saudi Arabia. A total of 12 nurses were interviewed for this study in the course of 5 months. The interviews conducted with the 12 nurses were audiotaped recorded and subsequently transcribed in verbatim form and the Collaizi Method was used for the extraction of meanings from the interviews. Results: Five major themes were identified in the transcribed form of the interview and 11 subthemes emerged as well. The five major themes were educational preparation, transition into practice, cultural competence, image of nursing and language and communication. Conclusions: The study described the different challenges faced by Saudi nurse graduates from being students to professionals based from their experiences as newly employed staff nurses in different hospitals in Saudi Arabia. Their stories captured the story of novice nurses not only as a Saudi but may be true for other nationalities. These stories are shared by all nurses across the world who struggle to meet the demands of the nursing profession.Mohammad Alboliteeh, Judy Magarey, Richard Wiechul