ARGO-YBJ Experiment Research Articles

Simulation of the ARGO-YBJ experiment operated in Scaler Mode

The ARGO-YBJ experiment is a large area full coverage detector operating at high mountain altitude (4300 m a.s.l., Tibet, China, ∼6700 m 2 active surface). In scaler mode, the particle rate is recorded at fixed time intervals (0.5 s), allowing the achievement of an energy threshold as low as E t h ∼ 1 GeV for the photons. This result, together with the estimate of the effective area as a function of the primary energy, has been obtained using the simulation code CORSIKA6201 for the shower development in the atmosphere and a dedicated and detailed detector simulation, ARGOG, based on GEANT3.21. With this simulation chain, and using the known primary proton and helium spectra, we obtained counting rates consistent with the measured ones, making us confident in the expectation of the detector performance as far as the photon shower detection is concerned, which is of crucial importance to determine the capability of the ARGO-YBJ experiment to detect gamma-ray bursts (GRBs).

The Argo YBJ Daq System and the GRID Based Data Transfer

The Argo-YBJ experiment has now reached its final design configuration. The detector system consists of a full coverage array (about 5800 square meters) of resistive plate chambers (RPCs). The throughput depends on the trigger rate and threshold. The DAQ system must be able to sustain a maximum transfer rate of the order of 15 MB/s and a high peak data flow. Data are read out using a typical front-end acquisition chain built around a custom bus. Specialized electronics have been designed and dedicated software has been written to perform this task. Data are sent to the online farm through a switch exploiting a gigabit ethernet protocol. A solution to transfer data from the YBJ laboratory to the laboratories belonging to the Argo-YBJ collaboration exploiting the GRID middleware has also been implemented. In this paper we describe the daq and the data mover main characteristics and performance.

Status of ARGO-YBJ: an overview

Within a Collaboration Agreement between INFN and CAS (Chinese Academy of Science), the ARGO-YBJ experiment is completely installed at the YangBaJing Cosmic Ray Laboratory (4300 m a.s.l., Tibet, P.R. China). ARGO-YBJ is a plane detector, with a total detection area of ∼ 6500 m 2 , made of Resistive Plate Chambers (RPCs) which provide a detailed space-time picture of the charged component of the extensive air showers. At present the detector is completely mounted and the central carpet of 5800 m 2 is operating under a multiplicity trigger N p a d ⩾ 20 , the trigger rate is about 3.5kHz and the data flow is 5MB/s. A 0.5 cm lead converter will be mounted on the detector in summer 2007.

ARGO-YBJ experiment and TeV gamma astronomy

The ARGO-YBJ detector is an extensive air shower array consisting of a carpet of Resistive Plate Chambers (RPCs). Very high energy (VHE) gamma ray astronomy is the main scientific goal of this Chinese-Italian experiment. High altitude and full coverage ensure a low energy threshold (few hundreds of GeV for primary photons), high duty-cycle and large field of view allow a continuous sky survey in the declination range from −10° to +70°. Also many features of the high energy cosmic rays are studied by ARGO-YBJ exploiting the unprecented shower reconstruction.

GRBs search results with the ARGO-YBJ experiment operated in scaler mode

The ARGO-YBJ experiment is almost completely installed at the YangBaJing Cosmic Ray Laboratory (4300 m a.s.l., Tibet, P.R. China). The lower energy limit of the detector (E∼1 GeV) is reached with the scaler mode, i.e., recording the single particle rate at fixed time intervals. In this technique, due to its high altitude location and large area (∼6700 m2), this experiment is the most sensitive among all present and past ground-based detectors. In the energy range under investigation, signals due to local (e.g. solar GLEs) and cosmological (e.g. GRBs) phenomena are expected as significant enhancements of the counting rate over the background. Results on the search for GRBs in coincidence with satellite detections are presented.

The Status of the ARGO Experiment at YBJ

The ARGO-YBJ experiment, located at Yangbajing, Tibet, China, performed by a wide Sino-Italian collaboration, is designed to study cosmic rays, sub-TeV gamma ray sources and GeV Gamma Ray Burst (GRB) emission in the northern hemisphere, by means of detecting small size EAS (Extensive Air Shower) using a full coverage RPC (Resistive Plate Chamber) carpet. The central carpet of the detector is installed and put into operation to date, with 1900m2 of the carpet already operating since December 2004. With a trigger multiplicity of ≥60 hits, corresponding to a primary mode energy of 2 TeV, the angular resolution of EAS measurements is

ARGO-YBJ: Status and First Results

Very high energy gamma ray astronomy is one of the scientific goals of the ARGO-YBJ experiment. The detector, which is located in Tibet (China) at 4300 m a.s.l., is a full coverage Extensive Air Shower array consisting of a carpet of Resistive Plate Chambers (RPCs) of about 7000m 2 . The high altitude and the full coverage ensure a very low energy threshold (few hundreds of GeV for primary photons), while the detector time resolution ( σ t ≃ 1 ns ) gives a good pointing accuracy, thus allowing a high sensitivity to γ -ray sources, with a field of view of more than 2 sr and a duty cycle close to 100%. The detector layout, performance and location, offer a unique possibility to make also a deep study of several characteristics of the hadronic component of the cosmic ray flux up to energies of several hundreds of TeV. In particular, the topological structure of the shower, the lateral distribution, the energy spectrum and the space and time flux modulations can be measured with high sensitivity. Moreover, the use of a full coverage detector with a high space granularity gives detailed images of the shower front, that can be used to test different hypotheses on the cosmic ray interaction model, the shower development in the atmosphere and particle physics at very high energies. In this work the general layout of the detector and its performance will be described, together with the first results coming from the analysis of a data sample collected with a relevant fraction of the apparatus that is already in continuous data taking.

Performance of the resistive plate chambers in the ARGO-YBJ experiment

The ARGO-YBJ experiment is designed for the detection of Extensive Air Showers (EAS) in the primary energy range 100 GeV–10 TeV. Its full-coverage feature allows to lower the energy threshold about one order of magnitude with respect to sampling EAS detectors. Here the performance of the RPC array is described and the current status of the experiment is presented.

The DAQ System for the ARGO-YBJ experiment

ARGO-YBJ is a full coverage air shower detector which is reaching its final design configuration. The physical goals of the experiment require the ability to study with high efficiency the low energy showers. The Data Acquisition (DAQ) System must be able to collect data from many front-end channels and sustain a high data transfer rate (up to 10–20 mega bytes per second). In this paper, the design and performance of the DAQ system are described.

ARGO-YBJ data acquisition system

The ARGO-YBJ experiment is reaching its final design configuration. An array of single layer Resistive Plate Counters (RPCs) covering an area of ∼ 5800 m 2 will collect a huge amount of data. The throughput required from the final detector strongly depends on the trigger rate. The DAQ system must be able to sustain a data transfer rate estimated to be the order of 15 MB/s and a high peak of data flow. Data are read out using a typical front-end acquisition chain built around a custom bus. Specialized electronics have been designed and efficient software had to be written to perform this task. Data are then sent to the on-line farm through a switch exploiting gigabit-ethernet protocol. In this paper we will describe the design of the DAQ system, the software which deals with data collection and network sending and the performances. The architecture of the on-line farm is also described together with the monitoring system.

Searching for emission from gamma-ray bursts with the ARGO-YBJ detector

The ARGO-YBJ experiment has been designed to decrease the energy threshold of typical Extensive Air Shower arrays by exploiting the high altitude location (Tibet, People's Republic of China, 4300 m a.s.l.) and the full coverage. The lower energy limit of the detector (a few GeV) is reached with the single particle technique, recording the counting rate at fixed time intervals. We present first results concerning the search for emission from Gamma-Ray Bursts in coincidence with satellite detections

Layout and performance of RPCs used in the Argo-YBJ experiment

The layout of the RPCs, used in the Argo-YBJ experiment to image with a high space-time granularity the atmospheric shower, is described in this paper. The detector has been assembled to provide both digital and analog informations in order to cover a wide particle density range with a time accuracy of 1 ns. The experimental results obtained operating the chambers in streamer mode at sea level with a standard gas mixture are presented.

SELECTION OF THE PRIMARY COSMIC RAY LIGHT COMPONENT WITH ARGO-YBJ

The ARGO-YBJ experiment, currently under construction at the YangBaJing High Altitude Cosmic Ray Laboratory (Tibet, P.R. China, 4300 m a.s.l.), may be upgraded with a large muon detector (~ 2500 m2) both to extend the sensitivity to γ-ray sources to energies ≥ 20 TeV and to perform a cosmic ray primary composition study. In this paper we discuss the capability of the upgraded ARGO-YBJ detector to select the primary cosmic ray light component in the knee energy region.

Sensitivity of ARGO-YBJ to different composition models in the energy range 10 ÷ 500 TeV

The ARGO-YBJ experiment is currently under construction at the Yangbajing Cosmic Ray Laboratory (4300 m a.s.l.).The detector consists of a central carpet, 74 × 78 m 2 , made of a single layer of Resistive Plate Counters (RPCs), and surrounded by a partially instrumented guard ring for a total instrumented area of about 6700 m 2 . The digital read-out, performed by means of pick-up electrodes 6.7 × 62 cm 2 ( strip ), allows to measure the charged particle number of small size air showers. The technique of counting the number of fired strips on the ARGO carpet corresponds to operate in the 10÷500 TeV energy region where both direct and indirect measurements on the primary cosmic radiation have been performed. Many composition models have been proposed by different experiments. In this work we discuss the ability of the ARGO detector to discriminate among some models.

The trigger system of the ARGO-YBJ experiment

The ARGO-YBJ experiment has been designed to detect air shower events over a large size scale and with an energy threshold of a few hundreds GeV. The building blocks of the ARGO-YBJ detector are single-gap Resistive Plate Counters (RPCs). The trigger logic selects the events on the basis of their hit multiplicity. Inclusive triggers as well as dedicated triggers for specific physics channels or calibration purposes have been developed. This paper describes the architecture and the main features of the trigger system.

Feasibility of measurements of cosmic ray composition by means of RPC digital read out in ARGO-YBJ

The ARGO-YBJ experiment is currently under construction at the Yangbajing Cosmic Ray Laboratory (4300 m a.s.l.). The detector will cover 74×78m2 with a single layer of Resistive Plate Counters (RPCs), surrounded by a partially instrumented guard ring. Signals from each RPC are picked up with 80 read out strips 6.7cm wide and 62cm long. The strip read out allows one to count the number of secondary charged particles from air showers induced by cosmic rays with an energy threshold of a few TeV. In this paper, we show that the digital response of the RPC can be used to discriminate between different models concerning the composition of the primary cosmic rays up to an energy of a few hundreds of TeV. In order to extend the dynamical range up to PeV energies, an analog read out has been implemented by instrumenting each RPC with two large size electrodes (Big Pads).

Local Station: the data read-out basic unit for the ARGO-YBJ experiment

ARGO-YBJ is a full coverage layer of Resistive Plate Counters (RPCs) covering an area of about 5.800 m 2 to be installed at the YangBaJing Laboratory (Tibet, China) at 4.300 m a.s.l . The DAQ system is based on a Central Station which receives the detector information from distributed readout electronics. Data from each RPC are acquired from a Receiver Card which reads out and digitizes the space and time information from 10 pick-up pads and gives out the pad multiplicity for trigger purposes. The Receiver Cards are hosted in Local Stations which Group 12 RPCs. On trigger occurrence, each Local Station sends the collected data to the Central Station. Both the detector and the electronics allow 1 ns accuracy in time measurements. In this work a detailed description of the Local Station and the Trigger System are presented.

Results from the ARGO-YBJ test experiment

A resistive plate counters (RPCs) carpet of ∼50 m 2 has been put in operation in the Yangbajing Laboratory (Tibet, P.R. China) at 4300 m a.s.l., in order to study the RPCs performance at high altitude and the detector capability of imaging the EAS disc. This test has been performed in view of an enlarged use of RPCs for the ARGO-YBJ experiment. This experiment will be devoted to a wide range of fundamental issues in cosmic rays and astroparticle physics, including in particular γ-ray astronomy and γ-ray bursts physics at energies ⩾100 GeV. In this paper we present and discuss the procedures adopted to calibrate the detector and reconstruct the shower direction. Results concerning many shower features as the angular distribution, the density spectrum, the time profile of the shower front, are found well consistent with the expectation.

FPGAs widen the ARGO-YBJ experiment's eyes

The ARGO-YBJ experiment is presently under construction at the Yangbaijing High-Altitude Cosmic Ray Laboratory (4300 m a.s.l), 90 km north to Lhasa (Tibet, People's Republic of China). ARGO will study fundamental issues in cosmic ray and astroparticle physics by detecting small-size air showers. The detector covers 74 /spl times/ 78 m/sup 2/ with single layer resistive plate counters (RPCs), surrounded by a partially instrumented guard ring. The ARGO Data Acquisition System is designed around static random access memory (SRAM)-based field programmable gate arrays (FPGAs), in order to achieve a fully reconfigurable architecture. In this environment, the same hardware platform performs different functions provided by companion FPGAs' configuration files. Control and monitoring software exploits a web browser to deliver commands and perform diagnostic tests on the boards. In this paper, we describe the hardware and the software strategies that allow the ARGO DAQ to benefit from the flexible architecture of in-system reconfigurable FPGAs.

Results from the analysis of data collected with a 50m 2 RPC carpet at YangBaJing

An RPC carpet covering ∼10 4 m 2 (ARGO-YBJ experiment) will be installed in the YangBaJing Laboratory (Tibet, People's Republic of China) at an altitude of 4300 m a.s.l. A test-module of ∼50 m 2 has been put in operation in this laboratory and about 10 6 air shower events have been collected. The RPC performance at high altitude and the carpet capability of reconstructing the shower features are presented.