Fluorescence Telescopes Research Articles

Latest results of the CODALEMA experiment: cosmic rays radio detection in a self trigger mode

Dedicated to the measurement of the radio transients coming from the extensive air showers (EAS), the CODALEMA experiment was started in 2001 at the Nançay Observatory, in France. Benefiting of an easy deployment and a low cost compared with Cherenkov detectors or fluorescence telescopes, this alternative method appears to be an interesting tool for the understanding of the physics of high energy cosmic rays observed through EAS. A new configuration of the CODALEMA experiment was implemented in 2011 based on a standalone detection, which will be essential for the next generation of giant detector array. One of the major challenges of this promising detection mode is the control (identification and rejection) of the fluctuating and transient noise events in an inhabited area and the knowledge of the shower radio-detection capabilities such as the effective efficiency and the data purity. Some results concerning this new setup of the experiment will be discussed in this paper.

FAMOUS – A prototype silicon photomultiplier telescope for the fluorescence detection of ultra-high-energy cosmic rays

Due to their high photon detection efficiency, silicon photomultipliers (SiPMs) promise to increase the sensitivity of today's fluorescence telescopes which use photomultiplier tubes to detect light originating from extensive air showers. On the other hand, drawbacks like a small sensitive area, a strong temperature dependence, a high noise rate and a reduced dynamic range have to be managed.We present plans for FAMOUS, a prototype fluorescence telescope using SiPMs and a special light collecting optical system of Winston cones to increase the sensitive area. The prototype will make use of a Fresnel lens. For several different types of SiPMs we measured their characteristics. Moreover, we will present the R&D in compact modular electronics using photon counting techniques. An evaluation of the performance of the optical telescope design is performed by means of a full detector simulation.

Measurement of the proton-air cross-section with the Pierre Auger Observatory

We present the procedure to measure the proton-air cross-section at a center-of-mass energy per nucleon of 57TeV developed by the Pierre Auger Collaboration. The conversion from proton-air to inelastic proton-proton cross-section with an extended Glauber calculation is discussed. The systematic uncertainties of the analysis are summarized and the final result compared to accelerator data and model predictions. The growth of hadronic cross-sections towards ultra-high energies reflects changes in the internal structure of the colliding particles. Due to the nature of QCD it is still not possible to calculate hadronic cross-sections at ultra-high energies from first principles. It is thus of paramount importance to measure hadronic cross-sections in order to guide the development of phenomenological models needed to describe secondary multiparticle production at ultra-high energies. Such models are crucial, for example, for a detailed interpretation of available cosmic-ray air-shower data in terms of the primary mass composition. Without a better understanding of the cosmic-ray mass composition it will be very difficult to distinguish between different scenarios of cosmic-ray acceleration and propagation. We present the measurement of the proton-air cross-section with data of the Pierre Auger Observatory (1). The Pierre Auger Observatory is located close to the town of Malargue in Argentina. It consist of about 1660 water Cherenkov particle detector spread over a surface area of 3000km 2 .D uring clear and moonless nights the atmosphere on top of the surface array is overlooked by 27 fluorescence telescopes. This analysis is based on the observation of the longitudinal air-shower development with the telescopes. By combining the timing data of the surface detectors with that of the fluorescence telescopes a very precise reconstruction of the geometry is achieved (2). This technique is called hybrid reconstruction. It allows us a very accurate measurement of Xmax, the position at which an air-shower deposits the maximum energy per unit of mass of atmosphere traversed (3). With the precise observation of longitudinal air-shower fluctuations it is possible to achieve high sensitivity to the mean free path of the primary cosmic-ray particles and thus to the cross-section. This technique is well known and has been first applied by the Fly's Eye experiment (4). We also discuss systematic uncertainties and limitations of the cross-section measurement. In a last step, the proton-air cross-section measurement is converted into a proton-proton cross-section. This conversion makes use of a Glauber calculation, which has been extended to account for inelastic screening effects.

Results from the Pierre Auger Observatory

The Pierre Auger Observatory has been designed to investigate the origin and the nature of Ultra High Energy Cosmic Rays using a hybrid detection technique. It is located in the Province of Mendoza, Argentina, and consists of a surface array of about 3000 km 2 overlooked by 27 air fluorescence telescopes grouped in four sites, which together provide a powerful instrument for air shower reconstruction. The combination of information from the surface array, measuring the lateral distributions of secondary particles at the ground, and the fluorescence telescopes, observing the longitudinal profile, enhances the reconstruction capability with respect to the individual detector components. Ultra High Energy Cosmic Rays offer also the unique chance of investigating particle interactions over an energy range well beyond the one covered by present and future ground-based particle accelerators. A review of selected results is presented with the emphasis given to the measurement of energy spectrum, arrival directions, chemical composition and the search for photons and neutrinos as primary particles.

Mass composition working group report

We present a summary of the measurements of mass sensitive parameters at the highest cosmic ray energies done by several experiments. The Xmax distribution as a function of energy has been measured with fluorescence telescopes by the HiRes, TA and Auger experiments and with Cherenkov light detectors by Yakutsk. The 〈Xmax〉 or the average mass (〈lnA〉) has been also inferred using ground detectors, such as muon and water Cherenkov detectors. We discuss the different data analyses elaborated by each collaboration in order to extract the relevant information. Special attention is given to the different approaches used in the analysis of the data measured by fluorescence detectors in order to take into account detector biases. We present a careful analysis of the stability and performance of each analysis. The results of the different experiments will be compared and the discrepancies or agreements will be quantified.

New detection technologies for ultra-high energy cosmic rays and neutrinos

Even with an accumulated data set from an integrated six years of lifetime from the Auger experiment, no point sources of charged cosmic rays have be identified at the highest energies. Significantly increased apertures such as promised by the JEMEUSO mission will be required to identify these sources from the cosmic ray signatures themselves. However, in employing water-cherenkov surface detectors as well as fluorescence telescopes, Auger has demonstrated the power provided by the hybrid technology approach. New detection technologies thus provide a valuable tool, in particular for the study of systematic effects.

Results from the Pierre Auger Observatory

The Pierre Auger Observatory has been designed to investigate the origin and the nature of Ultra High Energy Cosmic Rays using a hybrid detection technique. It islocated in the Province of Mendoza, Argentina, and consists of a surface array of about 3000 km2 overlooked by 27 air fluorescence telescopes grouped in four sites, which together provide a powerful instrument for air shower reconstruction. The combination of information from the surface array, measuring the lateral distributions of secondary particles at the ground, and the fluorescence telescopes, observing the longitudinal profile, enhances the reconstruction capability with respect to the individual detector components. Ultra High Energy Cosmic Rays offer also the unique chance of investigating particle interactions over an energy range well beyondthe one covered by present and future ground-based particle accelerators. A review of selected results is presented with the emphasis given to the measurement of energy spectrum, arrival directions, chemical composition and the search for photons and neutrinos as primary particles.

Mass sensitive observables of the Pierre Auger Observatory

In this article we will discuss measurements of the longitudinal development of air showers at the Pierre Auger Observatory. The longitudinal development of the electromagnetic component can be directly observed by the fluorescence telescopes of the Auger Observatory and we will present the results on the evolution of the average shower maximum and its fluctuations as a function of energy. Moreover, two observables from the surface detector, the asymmetry of the rise time of the station signals and the muon production depth, will be discussed and the measurements will be compared to predictions from air shower simulations for different primary particle types.

The Pierre Auger Research and Development Array (RDA) in southeastern Colorado – R&D for a giant ground array

The Pierre Auger Research and Development Array (RDA) was originally designed to be the precursor of the northern Auger observatory, a hybrid array of 4400 surface detector stations and 39 fluorescence telescopes deployed over 20,000 square kilometers. It is conceived as a test bed aiming at validating an improved and more cost-effective 1-PMT surface detector design and a new peer-to-peer communication system. The array of ten surface detector stations and ten communication-only stations is currently being deployed in southeastern Colorado and will be operated at least until late 2013. It is configured in such a way that it allows testing of a new peer-to-peer communication protocol, as well as a new surface detector electronics design with a larger dynamic range aiming at reducing the distance from the shower core where saturation is observed. All these developments are expected in the short term to improve the performance of the Pierre Auger Observatory and enable future enhancements. In the longer term, it is hoped that some of these new developments may contribute to the design of a next-generation giant ground array.

Identification of the primary mass of inclined cosmic ray showers from depth of maximum and number of muon parameters

In the present work we carry out a study of the high energy cosmic rays mass identification capabilities of a hybrid detector employing both fluorescence telescopes and particle detectors at ground using simulated data. It involves the analysis of extensive showers with zenith angles above 60° making use of the joint distribution of the depth of maximum and muon size at ground level as mass discriminating parameters. The correlation and sensitivity to the primary mass are investigated. Two different techniques – clustering algorithms and neural networks – are adopted to classify the mass identity on an event-by-event basis. Typical results for the achieved performance of identification are reported and discussed. The analysis can be extended in a very straightforward way to vertical showers or can be complemented with additional discriminating observables coming from different types of detectors.

On the possibility of neutrino flavor identification at the highest energies

High energy astrophysical neutrinos carry relevant information about the origin and propagation of cosmic rays. They can be created as a by-product of the interactions of cosmic rays in the sources and during propagation of these high energy particles through the intergalactic medium. The determination of flavor composition in this high energy flux is important because it presents a unique chance to probe our understanding of neutrino flavor oscillations at gamma factors >10^21. In this work we develop a new statistical technique to study the flavor composition of the incident neutrino flux, which is based on the multipeak structure of the longitudinal profiles of very deep electron and tau neutrino horizontal air showers. Although these longitudinal profiles can be observed by means of fluorescence telescopes placed over the Earth's surface, orbital detectors are more suitable for neutrino observations owing to their much larger aperture. Therefore, we focus on the high energy region of the neutrino spectrum relevant for observations with orbital detectors like the planned JEM-EUSO telescope.

The non-linearity between [formula omitted] and [formula omitted] induced by the acceptance of fluorescence telescopes

The measurement of the average depth of the shower maximum is the most commonly used observable for the possible inference of the primary cosmic-ray mass composition. Currently, different experimental Collaborations process and present their data not in the same way, leading to problems in the comparability and interpretation of the results. Whereas 〈Xmax〉 is expected to be proportional to 〈lnA〉 in ideal conditions, we demonstrate that the finite field-of-view of fluorescence telescopes plus the attenuation in the atmosphere introduce a non-linearity into this relation, which is specific for each particular detector setup.

Influence of the photonuclear effect on electron-neutrino-induced electromagnetic cascades under the Landau-Pomeranchuk-Migdal regime in standard rock

The observation of earth skimming neutrinos has been proposed as a rather sensitive method to detect ultra-high energy (UHE) cosmic neutrinos. Energetic cosmic neutrinos can interact inside the rock and produce leptons via a charged current interaction. In the case of an incoming ${\ensuremath{\nu}}_{e}$ undergoing a charged current interaction, the produced UHE electron will induce an underground electromagnetic shower. At high energy (above 7.7 TeV in standard rock), such showers are subject to LPM (Landau, Pomeranchuk, and Migdal) suppression of the radiative processes cross sections (bremsstrahlung and pair production). The consequence of this suppression is that showers are elongated. This effect will increase the detection probability of such events allowing deeper showers to emerge with detectable energies. On the other hand, the photonuclear processes which are usually neglected in electromagnetic showers with respect to radiative processes, turn out to become dominant in the LPM regime and will reduce the shower length. In this work, we have performed a complete Monte Carlo study of an underground shower induced by UHE electrons by taking into account both the LPM suppression and the photonuclear interaction. We will discuss the effects of both of these processes on the shower length and on the detectability of such events by ground arrays or fluorescence telescopes. We show that limits on neutrino fluxes that were obtained using simulations that were obviously neglecting photonuclear processes are overoptimistic and should be corrected.

Enhancements to the Southern Pierre Auger Observatory

The southern Pierre Auger Observatory has been detecting cosmic rays above 1018eV since 2004, exploiting a hybrid air shower detection technique, with 1660 water Cherenkov detectors together with 24 air fluorescence telescopes on a 3000 km2 site. As low energy enhancements to the observatory, 3 additional telescopes with elevated fields of view were built (HEAT). The detector density was increased in the HEAT fields of view by a factor of four in an area of about 25 km2. This setup enables unbiased hybrid data taking above 1017eV. The infilled area is also being equipped with large underground scintillator muon detectors (AMIGA). Finally, a prototype array of radio antenna stations (AERA), working from 30 to 80 MHz, has been installed in a part of the infill. Properties and status of AMIGA, HEAT, and AERA are presented.

SiPM interdisciplinary application in the fields of astroparticle physics and bio-molecular science

In the last few years we have developed a sub-μs 256 channel camera using Silicon Photomultipliers (SiPMs) for interdisciplinary application in various fields such as astroparticle physics and bio-molecular science.The camera consists of 256 pixels of SiPMs (16×16-ch Hamamatsu MPPCs) read by 16 of 16-ch ASICs, and two data processing system boards which are capable of a sampling data rate of 166MHz.The technology of this camera is based on a space-borne fluorescence telescope, JEM-EUSO [1]. Also, the SiPMs that we use for the camera are the ones developed for astroparticle physics applications in imaging atmospheric Cherenkov telescopes (IACTs) such as MAGIC/MAGIC-II (Albert et al., 2008 [2]) and CTA [3].The fast, high spatial and temporal resolution camera with single photon counting capability enables us to open a new window not only in astroparticle physics but also in bio-molecular science.Here we report on the camera development. Also, status of the applications in imaging air Cherenkov events and protein dynamics observations, molecular motor dynamics observations will be reported.

R&D in photosensors and data acquisition systems for a new generation of Cosmic Ray Cherenkov and Fluorescence Imaging focal planes

In this work we present the design, first prototypes and experimental R&D activities on the development of novel imaging cameras for Imaging Atmospheric Cherenkov and Fluorescence Telescopes. The baseline solution for the focal plane is based on a photosensor architecture instrumented with Silicon Photomultipliers (SiPMs). To decrease the trigger threshold and improve the signal-to-noise ratio for low-energy events, the Photon Counting technique is used. For very bright events the conventional Charge Integration approach is retained. The large number of channels requires a compact and modular design with minimal cabling and distance between the photosensors and the frontend. Other design requirements are an efficient light concentration system treated with an anti-reflective coating, a liquid cooling system able to keep the SiPMs at a temperature of −20°C to −10°C, a low-power frontend electronics down to 1kW/m2 and an easy field maintenance, high reliability data acquisition and trigger system. In the baseline design, the data acquisition system is partitioned in on-board frontend and off-detector high-level trigger electronics. Extensive use of mixed-signal ASICs and low-power FPGAs for early data reduction (Level 1 trigger), compatible with a liquid cooling sub-system for temperature control is adopted. The off-detector data acquisition and higher trigger (Level 2 and Level 3) architecture is based on the VME64X standard. The boards are connected by multi-Gbps optical links to the focal plane camera. Trigger primitives are sent asynchronously to the trigger boards via data links running at their own clocks. Data and slow-control data streams are also sent over the same links with the parallel VME64X backplane kept for trigger board configuration, slow-control and final data readout. Each 8-slot 6U crate can process up to about 3.6×104 SiPM channels.

Performance and applications of the UVscope instrument

Abstract UVscope is a portable multi-pixels photon detector developed at IASF-Pa to support experimental activities in the high-energy astrophysics and cosmic rays field. The instrument, working in single photon counting mode, is designed to directly measure light flux in the wavelengths range 300–650 nm. Thanks to its features and operational flexibility, the instrument can be used in a wide field of applications where the knowledge of the environmental luminosity is required, as in the characterization of sites for ground-based Cherenkov and fluorescence telescopes, and for cross-calibration of their cameras. The present version of UVscope is based on a Multi Anode Photo Multiplier Tube and it is completed by a motorized mount and a filter wheel which allow to make low-light measurements, at programmed pointing directions and at different filter wavelengths. In this paper, the instrument is firstly presented in all its components; then the procedures adopted for its absolute and relative calibration are detailed. The performance of UVscope is evaluated and, finally, current and planned scientific applications are described.

HEAT – a low energy enhancement of the Pierre Auger Observatory

The High Elevation Auger Telescopes (HEAT) are three tiltable fluorescence telescopes which represent a low energy enhancement of the fluorescence telescope system of the southern site of the Pierre Auger Observatory in Argentina. The Pierre Auger Observatory is a hybrid cosmic ray detector consisting of 24 fluorescence telescopes to measure the fluorescence light of extensive air showers complemented by 1600 water Cherenkov detectors to determine the particle densities at ground. In this configuration air showers with a primary energy of 10^18 eV and above are investigated. By lowering the energy threshold by approximately one order of magnitude down to a primary energy of 10^17 eV, HEAT provides the possibility to study the cosmic ray energy spectrum and mass composition in a very interesting energy range, where the transition from galactic to extragalactic cosmic rays is expected to happen. The installation of HEAT was finished in 2009 and data have been taken continuously since September 2009. Within these proceedings the HEAT concept is presented. First data already demonstrate the excellent complement of the standard Auger fluorescence telescopes by HEAT.

The Fluorescence Detector of the Pierre Auger Observatory

The Pierre Auger Observatory is a facility designed for the study of ultra-high energy cosmic rays. The Observatory combines two different types of detectors: a surface array of 1600 water Cherenkov stations placed on a 1.5 km triangular grid covering over 3000 km2; and a fluorescence detector of 24 telescopes located in 4 buildings at the perimeter of the surface array. The fluorescence telescopes, each consisting of 440 photomultipliers, collect the ultraviolet light produced when the charged secondary particles in an air shower excite nitrogen molecules in the atmosphere. Because the intensity of the nitrogen fluorescence is proportional to the energy deposited in the atmosphere during the air shower, the air fluorescence measurements can be used to make a calorimetric measurement of the cosmic ray primary energy. Showers observed independently by the surface array and fluorescence telescopes, called hybrid events, are critical to the function of the Observatory, as they allow for a model-independent calibration of the surface detector. In this paper I describe the detector and the most important measurements.

First results from the Telescope Array

The Telescope Array Project is a successor to the High Resolution Flyʼs Eye (HiRes) and AGASA (Akeno Giant Air Shower Array) experiments. It is the largest ultra high energy cosmic ray experiment in the northern hemisphere. The Telescope Array observatory has been collecting data since 2008 using a hybrid of fluorescence telescopes and scintillator surface detectors. Some of the first results from the experiment are presented including the monocular spectrum from the Middle Drum fluorescence site and the spectrum from the scintillator array. These are in good agreement with the spectrum from the High Resolution Flyʼs Eye. In addition, a first pass at a composition measurement is made and indicates a predominantly light composition in the 10 19 eV region. Finally, some of the ongoing work of the group is presented including a novel technique for an end to end calibration of the telescopes involving a 40 MeV linear accelerator.