A new multidetector system with magnetic spectrograph for study of cosmic ray extensive air shower components

An array of detectors for simultaneous observation of different components of cosmic ray extensive air showers (EAS) is described. The detector array, comprising plastic scintillation counters as electron detectors, magnetic spectrograph units and a muon flash tube chamber as muon detectors and a large volume multiplate cloud chamber as hadron detector has been set up and is now being operated at NBU campus. The array of detectors is sensitive to air showers initiated by cosmic primaries of energy in the range 10¹⁴–10¹⁵ eV.     

Extensive air shower experiment at Kolar Gold Fields

An experiment to determine the nature of primary cosmic rays of energy > 10¹⁴ eV by studying high energy (> 220 GeV) muons and their correlations with other parameters of extensive air showers generated by them, was carried out at Kolar Gold Fields, India (atmospheric depth of 920 g cm⁻²). An accurate estimate of shower parameters in showers as small as 10⁴ particles was achieved by means of a closely packed array of large area detectors and by employing special methods of analysis. In this paper, the details of the array, the data recording system, the procedure of data analysis and error estimates are described.     

Results from the Pierre Auger Observatory

The southern part of the Pierre Auger Observatory located in Province of Mendoza, Argentina, is now completed and fully operational. Data are routinely recorded since 2004, even during the construction phase. It consists of a ground array of more than 1.600 water-Cherenkov detectors spread over an area of 3000 km², overlooked by 24 wide-angle fluorescence telescopes placed in four sites on the array boundary. Southern Observatory is taking data in hybrid mode making it the first hybrid detector for studying the origin and the nature of cosmic rays at extreme energies. Current characteristics of the observatory and recent results on primary cosmic ray spectrum, arrival directions and composition are presented.     

Cosmic ray physics with the ARGO-YBJ experiment

Cosmic ray physics in the 10¹²–10¹⁵ eV primary energy range is among the main scientific goals of the ARGO-YBJ experiment. The detector, located at the Cosmic Ray Observatory of Yangbajing (Tibet, P.R. China) at 4300 m a.s.l., is a full coverage Extensive Air Shower array consisting of a carpet of Resistive Plate Chambers of about 6000 m². The apparatus layout, performance and location offer a unique possibility to make a deep study of several characteristics of the hadronic component of the cosmic ray flux in an energy window marked by the transition from direct to indirect measurements. In this work we will focus on the experimental results concerning the measurements of the primary cosmic ray energy spectrum and of the proton-air cross-section. The all-particle spectrum has been measured, by using a bayesian unfolding technique, in the 1–100 TeV energy region. The proton-air cross-section has been measured at the same energies, by exploiting the cosmic ray flux attenuation for different atmospheric depths (i.e. zenith angles). The total proton–proton cross-section has then been estimated at center of mass energies between 70 and 500 GeV, where no accelerator data are currently available.     

TANGO Array.: 1. The instrument

TANGO Array is an air shower experiment which has been constructed in Buenos Aires, Argentina. It was commissioned during the year 2000 becoming fully operational in September, 2000. The array consists of four water Cherenkov detectors enclosing a geometrical area of $\text{∼30,000}\text{m}{}^2$ and its design has been optimized for the observation of Extended Air Showers produced by cosmic rays near the “knee” energy region $\text{∼4×10}{}^{15}\text{eV}$. Three of the detectors have been constructed using 12,000-l stainless-steel tanks, and the fourth has been mounted in a smaller, 400-l plastic container. The detectors are connected by cables to the data acquisition room, where a very simple system, which takes advantage of the features of a four-channel digital oscilloscope, was set for data collection. This data collection setup allows a fully automatic experiment control which does not require operator intervention. It includes monitoring, data logging, and daily calibration of all detectors. This paper describes the detectors and their associated electronics, and details are given on the data acquisition system, the triggering and calibration procedures, and the operation of the array. Examples of air shower traces, recorded by the array, are presented.     

Modelling radiation loads to detectors in a SNAP mission

In order to investigate the degradation of optical detectors of the Supernova Acceleration Project (SNAP) space mission because of irradiation, a three-dimensional model of the satellite has been developed. A realistic radiation environment at the satellite orbit, including both galactic cosmic rays and cosmic ray trapped in radiation belts, has been taken into account. The modelling has been performed with the MARS14 Monte Carlo code. In a current design, the main contribution to dose accumulated in the photo-detectors is shown to be due to trapped protons. The contribution of primary alpha particles is estimated. Predicted performance degradation for the photodetector for a four-year space mission is 40% and this can be reduced further by means of shielding optimisation.     

A new method to detect gamma ray extensive air showers which directly measures angles and identifies muons

We describe an extensive air shower array (GRAND™) ⁷ which is currently under construction. It is dedicated to recording ultrahigh energy (UHE) gamma rays from stellar point sources by measuring the angle of charged secondaries with proportional wire chamber tracking detectors. This new method is designed to give 0.25° angular resolution for the primary gamma direction with 100 detected secondary electrons. These same tracking detectors make possible a new, inexpensive detector for muons thereby enabling the rejection of muon-rich hadronic shower background.     

Measuring cosmic ray radio signals at the Pierre Auger Observatory

The recent results of the LOPES and CODALEMA experiments open the door to a renewal of the radio technique for cosmic ray induced shower measurements. The demonstration has been done of its potential and performances at energies below 10¹⁸ eV, this upper limit being due to the small scale of the current experiments. A natural stage toward the improvement of the method is thus to install radio detectors in association with a large cosmic ray detector such as Auger. Besides surface and fluorescence detection, radio detection could be an alternative method, providing a complementary information. The Pierre Auger Collaboration has thus engaged a R&D effort which will lead to the installation of a radio engineering array covering 20 km² on its southern site. Outline of the technique, results of the first phase of the tests and current plans for the future engineering array will be presented.     

Advanced passive detectors for neutron dosimetry and spectrometry

Different neutron detectors have been developed in the past which exploit electrical and electrochemical processes in plastic foils and thin-film capacitors (namely metal-oxide-silicon devices) to trigger avalanche processes, which greatly facilitate the detection of neutron-induced charged particles. These detectors are: (i) spark-replica counter of neutron-induced fission-fragment holes in plastic films, thin-film breakdown counter of neutron-induced fission fragments, and electrochemically etched detectors of neutron-induced recoils in plastic foils. The major shortcomings of damage-track detectors for the measurement of low neutron fluencies, such as those of cosmic ray neutrons at civil aviation altitudes, are their large and unpredictable background and their small signal-to-noise ratio. These shortcomings have been overcome respectively by using long exposure times and large detector areas and counting coincidence-track events on matched pairs of detectors even for a few-micron-long tracks such as those of neutron recoils. The responses of all these detectors have been analysed both with neutrons with energy up to approximately 200 MeV and protons up to tens of gigaelectron volts. Applications of these detectors for the cosmic ray neutron dosimetry and/or spectrometry will be mentioned.     

Amplitude calibration of a digital radio antenna array for measuring cosmic ray air showers

Radio pulses are emitted during the development of air showers, where air showers are generated by ultra-high energy cosmic rays entering the Earth's atmosphere. These nano-second short pulses are presently investigated by various experiments for the purpose of using them as a new detection technique for cosmic particles. For an array of 30 digital radio antennas (LOPES experiment) an absolute amplitude calibration of the radio antennas including the full electronic chain of the data acquisition system is performed, in order to estimate absolute values of the electric field strength for these short radio pulses. This is mandatory, because the measured radio signals in the MHz frequency range have to be compared with theoretical estimates and with predictions from Monte Carlo simulations to reconstruct features of the primary cosmic particle. A commercial reference radio emitter is used to estimate frequency dependent correction factors for each single antenna of the radio antenna array. The expected received power is related to the power recorded by the full electronic chain. Systematic uncertainties due to different environmental conditions and the described calibration procedure are of order 20%.     

High energy gamma ray observatories for the study of cosmic ray electrons above 1014 eV

We have studied in detail the possibility of detecting cosmic ray electrons of energy ?10¹⁴ eV using high energy γ-ray detectors. Such instruments would detect synchrotron γ-rays radiated by the electrons, while traversing the Earth's magnetic field. These radiated γ-rays are expected to be incident along a straight line in the detector for an unambiguous identification of an electron event. Our analysis shows that small γ-ray detectors such as those in SAS-2 and COS-B satellites cannot be used for this purpose. The high energy γ-ray detector to be flown on the GRO satellite may be able to detect electrons, if the energy spectrum of electrons at high energies is modified by the influence of a nearby source. Such exciting possibilities can be observed with large area γ-ray instruments, which are aslo capable of detecting γ-rays through Compton scattered electrons. We have, in this investigation, suggested ways of utilizing future large area γ-ray observatories to open up a new avenue for the study of ultra high energy cosmic ray electrons.     

Small pixel CZT detector for hard X-ray spectroscopy

A new small pixel cadmium zinc telluride (CZT) detector has been developed for hard X-ray spectroscopy. The X-ray performance of four detectors is presented and the detectors are analysed in terms of the energy resolution of each pixel. The detectors were made from CZT crystals grown by the travelling heater method (THM) bonded to a 20×20 application specific integrated circuit (ASIC) and data acquisition (DAQ) system. The detectors had an array of 20×20 pixels on a 250 μm pitch, with each pixel gold-stud bonded to an energy resolving circuit in the ASIC. The DAQ system digitised the ASIC output with 14 bit resolution, performing offset corrections and data storage to disc in real time at up to 40,000 frames per second. The detector geometry and ASIC design was optimised for X-ray spectroscopy up to 150 keV and made use of the small pixel effect to preferentially measure the electron signal. A ²⁴¹Am source was used to measure the spectroscopic performance and uniformity of the detectors. The average energy resolution (FWHM at 59.54 keV) of each pixel ranged from 1.09±0.46 to 1.50±0.57 keV across the four detectors. The detectors showed good spectral performance and uniform response over almost all pixels in the 20×20 array. A large area 80×80 pixel detector will be built that will utilise the scalable design of the ASIC and the large areas of monolithic spectroscopic grade THM grown CZT that are now available. The large area detector will have the same performance as that demonstrated here.     

Horn Coupled Multichroic Polarimeters for the Atacama Cosmology Telescope Polarization Experiment

Multichroic polarization sensitive detectors enable increased sensitivity and spectral coverage for observations of the cosmic microwave background. An array optimized for dual frequency detectors can provide 1.7 times gain in sensitivity compared to a single frequency array. We present the design and measurements of horn coupled multichroic polarimeters encompassing the 90 and 150 GHz frequency bands and discuss our plans to field an array of these detectors as part of the ACTPol project.     

Energy determination of cosmic ray showers in surface arrays using signal inference at a single distance from the core

In most high energy cosmic ray surface arrays, the primary energy is currently determined from the value of the lateral distribution function at a fixed distance from the shower core, r₀. The value of r₀ is mainly related to the geometry of the array and is, therefore, considered as fixed independently of the shower energy or direction. We argue, however, that the dependence of r₀ on energy and zenith angle is not negligible. Therefore, in the present work we propose a new characteristic distance, which we call r_opt, specifically determined for each individual shower, with the objective of optimizing the energy reconstruction. This parameter may not only improve the energy determination, but also allow a more reliable reconstruction of the shape and position of rapidly varying spectral features. We show that the use of a specific r_opt determined on a shower-to-shower basis, instead of using a fixed characteristic value, is of particular benefit in dealing with the energy reconstruction of events with saturated detectors, which are in general a large fraction of all the events detected by an array as energy increases. Furthermore, the r_opt approach has the additional advantage of applying the same unified treatment for all detected events, regardless of whether they have saturated detectors or not.     

GRAPES-3—A high-density air shower array for studies on the structure in the cosmic-ray energy spectrum near the knee

The change in the spectral index from about -2.7 to -3.1 at 3×10¹⁵ eV in the all-particle energy spectrum of primary cosmic rays is very significant for learning about the nature of cosmic sources of ultra-high energy particles and their acceleration and propagation in the galactic disk. Any observation of a fine structure in the spectrum would be important for improving our understanding of these physical processes. The GRAPES-3 air shower array has been designed to achieve higher precision in determination of various shower parameters to enable observation of any fine structure in the energy spectrum, if it exists. The details of the shower detectors, shower trigger and the data acquisition system are presented here along with estimates of trigger efficiencies from Monte Carlo simulations for primary photons (γ-rays) and several nuclei.     

A silicon counter array for 2He detection

A multicounter array consisting of four Si detector telescopes was developed for the coincidence measurement of two protons with small relative energy (²He). Silicon detectors were designed and fabricated so that they have large solid angles when they are assembled to form a counter array. A total effective solid angle of 5–7 msr was achieved for the detection of 20–50 MeV ²He with relative energy lower than 1 MeV. A compact amplifier system was developed using low-noise hybrid ICs to treat many signals from the counter array.     

Cosmic ray background effects on the neutron intercepting silicon chip (NISC)

Cosmic rays are mainly composed of galactic and solar particles. Galactic particles have enormous energies and interact in the atmosphere causing cascades of secondary particles, which can travel through the atmosphere and reach sea level. The origin of the cosmic terrestrial neutrons is galactic particles and these neutrons contribute almost 97% of the cosmic rays at sea level. Solar particles originate from the sun and have less energy compared to galactic particles. Almost all the solar particles are absorbed in the atmosphere before reaching sea level. The solar particle flux depends on the 11-year solar cycle and varies by multiple orders of magnitude between these cycles. In this study, cosmic ray induced soft errors in the neutron intercepting silicon chip (NISC) are investigated via the NISC Soft Error Analysis Tool (NISCSAT), which uses Geant4 as the transport and tracking engine. The NISC is a new unconventional neutron monitoring/detection system, designed to enhance the soft error occurrences in the semiconductor memories by introducing ¹⁰B-enriched regions in the memory node structure. The main driving force comes from the reaction products of ¹⁰B (n,α) ⁷Li reaction because both α and ⁷Li particles can induce soft errors in the memory. Since the ¹⁰B (n,α) ⁷Li reaction strictly depends on the incoming neutron energy and has a high cross-section at the thermal neutron energies, effects of the background cosmic thermal neutrons on the NISC are investigated in this study.     

The Italian national survey of aircrew exposure: I. Characterisation of advanced instrumentation

The survey of aircrew exposure required the characterisation and/or the development of a diverse array of both passive and active instruments, which were not available at any one laboratory. To ensure the availability of the most advanced dosimetric systems and the relevant calibration facilities needed for the survey, an international collaboration was formed, which was facilitated by multinational research contracts promoted by the Commission of the European Communities. Close cooperation among scientists with long-term experience in different disciplines, such as cosmic ray measurement in space and radiation protection dosimetry, made it possible to exploit successfully damage track detectors for the accurate evaluation of very low fluences of particles with high energy and high charges. For a long time, the major concern for the assessment of aircrew exposure has been the accurate evaluation of the cosmic ray neutron dose. In this paper, four different dosimetric systems are considered, the response of which is sensitive to both low and high energy neutrons. All these dosimetric systems have provided consistent results when exposed together to the high energy beam facility at CERN, which is considered to approximate the cosmic ray field.     

Application of CLTD’s for High Resolution Mass Identification and for Stopping Power Measurements of Heavy Ions

An array of calorimetric low temperature detectors (CLTD’s) for energy sensitive detection of heavy ions was combined with time-of-flight (TOF) detectors to obtain a detector system for high resolution mass identification of low energy heavy ions. In addition the same setup was used to prove the ability of CLTD’s to be used in electronic stopping power measurements for heavy ions in matter. Experiments with 50?MeV ⁶³Cu and ⁶⁵Cu ions at the tandem accelerator at the MPI at Heidelberg, and with 25 to 250?MeV ²³⁸U ions at the UNILAC accelerator at GSI at Darmstadt have been performed. For ^63,65Cu at 50?MeV a mass resolution of Δm(FWHM)=0.9?amu, and for ²³⁸U in an energy range of 65 to 150?MeV a resolution of Δm(FWHM)=1.28?amu, was obtained. The results for stopping powers of ²³⁸U in carbon and gold are presented and compared with theoretical predictions and data from the literature.     

Establishment of a simple neutron calibration field using a moderated 252Cf source: Part II. Experimental characterization of simple neutron calibration field

This paper describes the development and experimental standardization of neutron fields simply arranged for detector calibrations used for radiation control and environmental measurement. These fields are the following: (1) bare ²⁵²Cf fission field, (2) iron-moderated ²⁵²Cf field, (3) carbone-moderated Cf field, and (4) polyethylene-moderated ²⁵²Cf field. These fields are most suitable for calibrating the detectors used in and around nuclear and radiation facilities, since the fields are designed to simulate the typical neutron fields in and around the facilities.The direct neutron components of these fields have been standardized by the following two methods: (1) calculation by the ANISN code, and (2) measurements with and without a shadow shield by detectors standardized in the national standard field at the Electrotechnical Laboratory (ETL). The neutron emission rates of the ²⁵²Cf source have been calibrated also at ETL. We have standardized only direct components because of their independence of room size and peripheral structures. The standardized values are energy spectra and dose equivalent rates of the direct neutron components; the accuracies have also been evaluated to be 20% below 100 keV, 15% at 1 MeV, and 50% above 5 MeV. These fields including room scattered components have also been characterized especially to calibrate neutron detectors having sensitivity to low energy room scattered neutrons, because of large errors caused by shadow shield subtraction.