Due to their simplicity and versatility of design, straight strip or rectangular pad anode structures are frequently used with micropattern gas detectors (MPGDs) to reconstruct high-precision space ...points for various tracking applications. The particle impact point is typically determined by interpolating the charge collected by several neighboring strips. However, to effectively extract the inherent positional information, the lateral spacing of the straight strips must be comparable to or preferably smaller than the full extent of the incident charge cloud. In contrast, highly interleaved anode patterns, such as zigzags, can adequately sample the incident charge with a pitch appreciably larger than the charge cloud. This has the considerable advantage of providing the same performance while requiring far fewer instrumented channels. Additionally, the geometric parameters defining such zigzag structures may be tuned to provide a near-uniform detector response along and perpendicular to the sensitive coordinate, without the need for so-called "pad response functions," while simultaneously maintaining excellent position resolution. We have measured the position resolution of a variety of zigzag-shaped anode patterns optimized for various MPGDs, including gas electron multiplyer (GEM), Micromegas, and micro-resistive-well (<inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>RWELL) and compared this performance with the same detectors equipped with straight strips of varying pitch. We report on the performance results of each readout structure, evaluated under identical conditions in a test beam.
We have developed highly interleaved zigzag-shaped electrodes for collecting charge on the readout plane of various micropattern gaseous detectors (MPGDs), including gas electron multiplier (GEM) and ...micromega detectors. An optimized zigzag pad (or strip) anode can greatly enhance charge sharing among neighboring pads compared to traditional straight strip or rectangular pad designs and as a result can deliver excellent position resolution with minimal channel count, while exhibiting a virtually uniform response across the detector. We have systematically studied the effects of varying the parameters that define the zigzag geometry using simulations and have measured several printed circuit boards (PCBs) comprising a range of zigzag designs. Recently, we have employed laser ablation to generate zigzag patterns with pad-to-pad gaps smaller than 1 mil (or 25 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula>). Reducing the gap well below the 3-mil limit imposed by traditional chemical etching has allowed the production of zigzag electrodes with unprecedentedly small feature sizes. In turn, laser-etched zigzag PCBs were shown to exhibit markedly improved performance over earlier generation PCBs, with position resolutions below 50 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> for a 2-mm pitch. This article will explore in detail the dependence of the position resolution on the structural parameters of a zigzag-shaped anode, specifically for the case of a quadruple GEM detector.
Due to their simplicity and versatility of design, straight strip or rectangular pad anode structures are frequently employed with micro-pattern gas detectors to reconstruct high precision space ...points for various tracking applications. The particle impact point is typically determined by interpolating the charge collected by several neighboring pads. However, to effectively extract the inherent positional information, the lateral spacing of the straight pads must be significantly smaller than the extent of the charge cloud. In contrast, highly interleaved anode patterns, such as zigzags, can adequately sample the charge with a pitch comparable to the size of the charge cloud or even larger. This has the considerable advantage of providing the same performance while requiring far fewer instrumented channels. Additionally, the geometric parameters defining such zigzag structures may be tuned to provide a uniform detector response without the need for so-called pad response functions, while simultaneously maintaining excellent position resolution. We have measured the position resolution of a variety of zigzag shaped anode patterns optimized for various MPGDs, including GEM, Micromegas, and micro-RWELL and compared this performance to the same detectors equipped with straight pads of varying pitch. We report on the performance results of each readout structure, evaluated under identical conditions in a test beam.
Les données sous forme de chaîne de symboles sont très variées (ADN, texte, EEG quantifié,…) et ne sont pas toujours modélisables. Une description universelle des chaînes de symboles indépendante des ...probabilités est donc nécessaire. La complexité de Kolmogorov a été introduite en 1960 pour répondre à cette problématique. Le concept est simple : une chaîne de symboles est complexe quand il n'en existe pas une description courte. La complexité de Kolmogorov est le pendant algorithmique de l’entropie de Shannon et permet de définir la théorie algorithmique de l’information. Cependant, la complexité de Kolmogorov n’est pas calculable en un temps fini ce qui la rend inutilisable en pratique.Les premiers à rendre opérationnelle la complexité de Kolmogorov sont Lempel et Ziv en 1976 qui proposent de restreindre les opérations de la description. Une autre approche est d’utiliser la taille de la chaîne compressée par un compresseur sans perte. Cependant ces deux estimateurs sont mal définis pour le cas conditionnel et le cas joint, il est donc difficile d'étendre la complexité de Lempel-Ziv ou les compresseurs à la théorie algorithmique de l’information.Partant de ce constat, nous introduisons une nouvelle mesure d’information universelle basée sur la complexité de Lempel-Ziv appelée SALZA. L’implémentation et la bonne définition de notre mesure permettent un calcul efficace des grandeurs de la théorie algorithmique de l’information.Les compresseurs sans perte usuels ont été utilisés par Cilibrasi et Vitányi pour former un classifieur universel très populaire : la distance de compression normalisée NCD. Dans le cadre de cette application, nous proposons notre propre estimateur, la NSD, et montrons qu’il s’agit d’une semi-distance universelle sur les chaînes de symboles. La NSD surclasse la NCD en s’adaptant naturellement à davantage de diversité des données et en définissant le conditionnement adapté grâce à SALZA.En utilisant les qualités de prédiction universelle de la complexité de Lempel-Ziv, nous explorons ensuite les questions d’inférence de causalité. Dans un premier temps, les conditions algorithmiques de Markov sont rendues calculables grâce à SALZA. Puis en définissant pour la première l’information dirigée algorithmique, nous proposons une interprétation algorithmique de la causalité de Granger algorithmique. Nous montrons, sur des données synthétiques et réelles, la pertinence de notre approche.
Data in the form of strings are varied (DNA, text, quantify EEG) and cannot always be modeled. A universal description of strings, independent of probabilities, is thus necessary. The Kolmogorov complexity was introduced in 1960 to address the issue. The principle is simple: a string is complex if a short description of it does not exist. The Kolmogorov complexity is the counterpart of the Shannon entropy and defines the algorithmic information theory. Yet, the Kolmogorov complexity is not computable in finit time making it unusable in practice.The first ones to make operational the Kolmogorov complexity are Lempel and Ziv in 1976 who proposed to restrain the operations of the description. Another approach uses the size of the compressed string by a lossless data compression algorithm. Yet these two estimators are not well-defined regarding the joint and conditional complexity cases. So, compressors and Lempel-Ziv complexity are not valuable to estimate algorithmic information theory.In the light of this observation, we introduce a new universal information measure based on the Lempel-Ziv complexity called SALZA. The implementation and the good definition of our measure allow computing efficiently values of the algorithmic information theory.Usual lossless compressors have been used by Cilibrasi and Vitányi to define a very popular universal classifier: the normalized compression distance NCD. As part of this application, we introduce our own estimator, called the NSD, and we show that the NSD is a universal semi-distance between strings. NSD surpasses NCD because it gets used to a large data set and uses the adapted conditioning with SALZA.Using the accurate universal prediction quality of the Lempel-Ziv complexity, we explore the question of causality inference. At first, we compute the algorithmic causal Markov condition thanks to SALZA. Then we define, for the first time, the algorithmic directed information and based on it we introduce the algorithmic Granger causality. The relevance of our approach is demonstrated on real and synthetic data.
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