The ANTARES Optical Beacon System

ANTARES is a neutrino telescope being deployed in the Mediterranean Sea. It consists of a three dimensional array of photomultiplier tubes that can detect the Cherenkov light induced by charged particles produced in the interactions of neutrinos with the surrounding medium. High angular resolution can be achieved, in particular when a muon is produced, provided that the Cherenkov photons are detected with sufficient timing precision. Considerations of the intrinsic time uncertainties stemming from the transit time spread in the photomultiplier tubes and the mechanism of transmission of light in sea water lead to the conclusion that a relative time accuracy of the order of 0.5 ns is desirable. Accordingly, different time calibration systems have been developed for the ANTARES telescope. In this article, a system based on Optical Beacons, a set of external and well-controlled pulsed light sources located throughout the detector, is described. This calibration system takes into account the optical properties of sea water, which is used as the detection volume of the ANTARES telescope. The design, tests, construction and first results of the two types of beacons, LED and laser-based, are presented.Comment: 21 pages, 18 figures, submitted to Nucl. Instr. and Meth. Phys. Res.

Performance of the First ANTARES Detector Line

In this paper we report on the data recorded with the first Antares detector line. The line was deployed on the 14th of February 2006 and was connected to the readout two weeks later. Environmental data for one and a half years of running are shown. Measurements of atmospheric muons from data taken from selected runs during the first six months of operation are presented. Performance figures in terms of time residuals and angular resolution are given. Finally the angular distribution of atmospheric muons is presented and from this the depth profile of the muon intensity is derived.Comment: 14 pages, 9 figure

Acoustic and optical variations during rapid downward motion episodes in the deep north-western Mediterranean Sea

An Acoustic Doppler Current Profiler (ADCP) was moored at the deep-sea site of the ANTARES neutrino telescope near Toulon, France, thus providing a unique opportunity to compare high-resolution acoustic and optical observations between 70 and 170 m above the sea bed at 2475 m. The ADCP measured downward vertical currents of magnitudes up to 0.03 m s-1 in late winter and early spring 2006. In the same period, observations were made of enhanced levels of acoustic reflection, interpreted as suspended particles including zooplankton, by a factor of about 10 and of horizontal currents reaching 0.35 m s-1. These observations coincided with high light levels detected by the telescope, interpreted as increased bioluminescence. During winter 2006 deep dense-water formation occurred in the Ligurian subbasin, thus providing a possible explanation for these observations. However, the 10-20 days quasi-periodic episodes of high levels of acoustic reflection, light and large vertical currents continuing into the summer are not direct evidence of this process. It is hypothesized that the main process allowing for suspended material to be moved vertically later in the year is local advection, linked with topographic boundary current instabilities along the rim of the 'Northern Current'.Comment: 30 pages, 7 figure

First results of the Instrumentation Line for the deep-sea ANTARES neutrino telescope

In 2005, the ANTARES Collaboration deployed and operated at a depth of 2500 m a so-called Mini Instrumentation Line equipped with Optical Modules (MILOM) at the ANTARES site. The various data acquired during the continuous operation from April to December 2005 of the MILOM confirm the satisfactory performance of the Optical Modules, their front-end electronics and readout system. as well as the calibration devices of the detector. The in situ measurement of the Optical Module time response yields a resolution better than 0.5 ns. The performance of the acoustic positioning system, which enables the spatial reconstruction of the ANTARES detector with a precision of about 10 cm, is verified. These results demonstrate that with the full ANTARES neutrino telescope the design angular resolution of better than 0.3 degrees can be realistically achieved

Изучение взаимосвязей агрохимических показателей почв с видовым составом растений некоторых участков дельты реки Лены, Северная Якутия

In connection with climate change and the development of natural resources in the Arctic, increasingly relevant is the problem of revealing the response of tundra vegetation to various natural and anthropogenic impacts, as well as the search for indicators for developing a system of monitoring the state of ecosystems in the Far North. The aim of this work was to describe the floristic composition and structure of plant communities, as well as to search for relationships between agrochemical indicators of soils and the species composition of plants in certain key sites of the Lena River Delta. A total of ten key sites of the Lena delta were studied. Agrochemical analysis of the soil samples was performed using standard methods. The content of biogenic and abiogenic elements was measured using an emission spectrometer. The relationship between the soil parameters and floristic composition was studied using cluster analysis. It was shown that the clustering of sites by standard agrochemical indicators was weakly expressed, while in terms of the content of elements in the mineralized samples and in water extracts the sites were grouped into two clusters at the level of 40 %÷60 % of the differences. The clustering of sites by plant species composition was very weak, and it was not possible to identify clusters with high or medium level of similarity, nor was it possible to detect similarity between cluster diagrams constructed by soil parameters and by plant species composition. As a result of the study, it is shown that the species composition of vascular plants weakly correlates with the properties of the soils of the key sites. The individual features identified manifest themselves in the form of trends and no clear patterns of interrelation of vegetation and soil parameters are discerned.В связи с изменением климата и освоением природных ресурсов Арктики все более актуальной становится проблема выявления ответной реакции тундровой растительности на различные природные и антропогенные воздействия, а также поиск индикаторов для разработки системы мониторинга состояния экосистем Крайнего Севера. Целью данной работы было описание флористического состава и строения растительных сообществ, а также поиск взаимосвязей между агрохимическими показателями почв и видовым составом растений на отдельных ключевых участках дельты реки Лены. Всего было изучено десять ключевых участков дельты Лены. Агрохимический анализ образцов почв был изучен стандартными методами. Содержание биогенных и абиогенных элементов измеряли с помощью эмиссионного спектрометра. Взаимосвязь между показателями почв и флористическим составом выявляли с помощью кластерного анализа. Было показано, что кластеризация участков по стандартным агрохимическим показателям была выражена слабо, тогда как по содержанию элементов в минерализованных образцах и в водных вытяжках участки группировались в два кластера на уровне 40÷60 % различий. Кластеризация участков по видовому составу растений была выражена очень слабо, и выявить кластеры с высоким или средним уровнем сходства не удалось, так же как не удалось обнаружить сходства кластерных диаграмм, построенных по почвенным параметрам и по видовому составу растений. В результате проведенного исследования показано, что видовой состав сосудистых растений слабо коррелировал со свойствами почв ключевых участков. Выявленные отдельные особенности проявлялись в виде тенденций, и четких закономерностей взаимосвязи растительного покрова и показателей почв не прослеживалось

Performance of the front-end electronics of the ANTARES neutrino telescope

ANTARES is a high-energy neutrino telescope installed in the Mediterranean Sea at a depth of 2475 m. It consists of a three-dimensional array of optical modules, each containing a large photomultiplier tube. A total of 2700 front-end ASICs named Analogue Ring Samplers (ARS) process the phototube signals, measure their arrival time, amplitude and shape as well as perform monitoring and calibration tasks. The ARS chip processes the analogue signals from the optical modules and converts information into digital data. All the information is transmitted to shore through further multiplexing electronics and an optical link. This paper describes the performance of the ARS chip; results from the functionality and characterization tests in the laboratory are summarized and the long-term performance in the apparatus is illustrated.Comment: 20 pages, 22 figures, published in Nuclear Instruments and Methods

The data acquisition system for the ANTARES neutrino telescope

The ANTARES neutrino telescope is being constructed in the Mediterranean Sea. It consists of a large three-dimensional array of photo-multiplier tubes. The data acquisition system of the detector takes care of the digitisation of the photo-multiplier tube signals, data transport, data filtering, and data storage. The detector is operated using a control program interfaced with all elements. The design and the implementation of the data acquisition system are described.Comment: 20 pages, 6 figures, accepted for publication in Nucl. Instrum. Meth.