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Images of atmospheric EAS Cherenkov light have been recorded in connection with the EAS-TOP experiment. We describe the technique (based on a multianode photomultiplier Philips XP4702) and present some preliminary data analysis.

Different fluxes and spectra of galactic cosmic rays (GCR) and solar cosmic rays result in a wide variety of radioactive and stable-nuclides production rates. The records of cosmic-ray interactions, have been studied in terrestrial archives, in meteorites, cosmic dust and lunar samples. We present here some results obtained in our laboratory on the study of cosmogenic radionuclides produced in meteorites which fell in the last century. The laboratory is situated in the underground station of Monte dei Cappuccini, Torino, at a depth of 70 m water equivalent to reduce the cosmic-ray background level. To measure γ-activity in meteorites we have set up a highly efficient and selective Ge−NaI(Tl) γ-ray spectrometer surrounded by a passive shield. The solar modulation affects the intensity of GCR and therefore the isotopes production rates in meteorites. The 11 y solar cycle is well reproduced by the variations of22Na (T 1/2=2.6 y) in meteorites which fell during the past three solar cycles. The44Ti (T 1/2=66.6 y) activity measured in eight chondrites which fell in the last 110 y is qualitatively consistent with the century-scale solar-activity variation, called the Gleissberg cycle. The increase is roughly four times higher, than expected (about 5%) for a GCR flux calculated by a model in which the solar-activity modulation is determined solely by the sunspot number indexR. This result suggests a much weakened modulation of GCR during the prolonged Gleissberg minimum during which highly ordered magnetic fields set up in the heliosphere.

We have measured the thermoluminescence (TL) profile of the Mediterranean Sea core CT85.5 at the same depths where the cosmogenic-isotope10Be production peak at 35 ky BP was found. Strong TL peaks are evident at 37.5 ky and 35.6 ky BP. The Fourier analysis of the TL time series running from 32.5 ky to 42.6 ky at 100 y sampling interval shows 2500 y and 500 y periodicities. We suggest that the Sun was «active» at the time of the10Be enhancement.

An accurate dating of recent Ionian Sea sediment cores has been performed by the210Pb radiometric method and by a detailed tephroanalysis. The markers of the historical volcanic eruptions which occurred in the Campanian area (Vesuvius, Phlegrean Fields, Ischia) during the last two millenia have been identified along the cores. Among the others, the famous Plinian Vesuvius eruption of 79 AD, which buried the Roman town of Pompei, has been recognized. Direct210Pb dating is limited to the last two centuries. The tephroanalysis demonstrates that the sedimentation rate estimated by the210Pb method is correct and it is constant, at least for the last 2 ky. The presence of the137Cs peak due to the intense activity of nuclear-weapon testing in the atmosphere in 1963–64 AD assures that the top of the core is present and not disturbed. The high precision of the core dating allows to transform the depth scale into a time scale with an accuracy of ∼1%. The analysis of several cores taken in the same area demonstrates that the results presented here are of general validity, at least in this region. The carbonatic mud deposited in the last millennia in the Gallipoli Terrace can be successfully utilized for investigating the environmental conditions in the recent past.

The muon-hadron detector of EAS-TOP is a 270 m2 calorimeter constructed inside the air shower array on the top of the underground Gran Sasso Laboratory (Italy). The general layout of the detector and the performances of the active part (streamer and proportional chambers) are presented.

The EAS-TOP Extensive Air Shower array, on top of the under-ground Gran Sasso Laboratory, is fully operating as a γ-ray astronomy observatory since the beginning of 1989. After showing the measured angular resolution of the detector, we present the results obtained from the analysis of 280 days of measurements in 1989–1990, with the purpose of investigating possible emission (d.c. and sporadic) from the candidate sources in the Northern hemisphere at an energy, >200 TeV.

We study the total carbonate profiles of three coastal cores extracted from the continental shelf in the Ionian Sea and of two deep-sea cores extracted from the Tyrrhenian abissal plane. An overall similarity between the two deep-sea profiles and among the three coastal profiles is observed, indicating the complete reproductibility of this type of experimental measurements. In the case of the coastal cores, a constant sedimentation rates=(0.0646±0.0007) cm/y has been determined by radiometric methods and by tephroanalysis. For the deep-sea cores, the spectra of the upper and lower halves of the carbonate depth profiles display the same periodic components, suggesting that the sedimentation rate is nearly the same along the entire deep cores as well. The use of a careful tephroanalysis, the recognition of the Ignimbrite layers of Campanian origin at the expected depths and the similarity between the upper part (5000y) of the carbonate profile of the deep-sea core with that of the coastal cores provide the indication that, on the average, 1 cm of sediment is deposited in about 100 y. We show that the trend of the carbonate record in the deep-sea core is well approximated by a signal obtained by linearly superposing the obliquity and the precession parameters of the Earth rotation axis. Since these astronomical factors contribute to the temporal variations of the Earth insolation, and since the CaCO3 content of the sediment is presumably affected by climatic factors, this result supports the evidence of astronomical control on the Earth's climate, as already pointed out by several authors who analysed the power spectra of δ18O, δD and CO2 temporal series from sediment and ice cores. After removal of the «astronomical» trend, the carbonate record displays a dominant periodicity at approximately 12000 y. The 12000 y wave, taken with the opposite sign, corresponds to the trend of the radiocarbon record in tree-rings. This result becomes particularly relevant in view of the existence of common periodicities of about 200 y waves (Suess wiggles) which have already been detected in the carbonate profiles of the coastal cores and in tree-ring radiocarbon data.

First results on the lateral and temporal structures of EAS obtained from the EAS-TOP array are presented. A correlation between the slope of the lateral distribution function and the time delay of EAS particles with respect to the shower front at fixed core distance is found and discussed.

A large-volume HPGe gamma-ray spectrometer in a NaI(Tl) well has been set up underground at 70 m.w.e. depth for whole body counting of cosmogenic radionuclides in meteorites. The detectors are housed in a 20 cm thick lead shield with a lining of cadmium and OFHC copper. The scintillator is simultaneously operated in anticoincidence as well as in coincidence in selected energy channels to achieve low background levels (in the range of counts per day) and high specificity. In this way a large number of radionuclides such as26Al,44Ti,60Co,22Na,54Mn, and shorter-lived nuclides produced in extraterrestrial materials like meteorites and lunar rocks can be analysed. Results on Bouvante and Bereba achondrites and Dhajala and Torino chondrites are presented.

EAS-TOP is a detector of the extensive air showers that very high-energy cosmic rays (E 0≥1014eV) produce in the atmosphere. The array is located on top of the underground Gran Sasso Laboratory in central Italy; a subarray (11 modules of the e.m. detector) has been operating since the end of 1987. From such data the stability of the detector, and the accuracies in the determination of the arrival directions and in the reconstruction of the electron lateral distribution and of the shower size are derived. The results obtained on VHE-UHE γ-ray sources in the first months of operation are presented.

An air shower array on top of the underground Gran Sasso Laboratory (GSL) can give valuable information in the field of high-energy cosmic-ray physics. We discuss the performances of a specific apparatus (EAS-TOP) operating both in coincidence with the underground array (i.e. for measuring the total primary energy of multimuon events) and as an autonomous air shower detector (for studies of ultra-high-energy gamma-ray astronomy, cosmic-ray anisotropies and primary composition).

The thermoluminescence profile of an Ionian Sea recent sedimentary core, constructed with 467 equispaced data points and spanning 18 centuries from 170 to 1974 A.D. is studied. Several time series analysis methods reveal two evident periodicities on the centennial time scale, at 137 years and 118 years, both with their second harmonics. Together with these slow cyclic variations two sharp periodicities appear on the decennial time scale, at 12.1 years and 10.8 years. In the present study the amplitude and phase of these waves have been determined and it is shown that their summation accounts for more than 50% of the standard deviation of the whole time series and that they correctly reproduce the basic characteristics of the data.

The lower limits of the nucleon lifetime obtainable with radiochemical and geochemical methods are discussed. The background rate produced by the cosmic radiation at great depths is evaluated, leading to the result of τ≤2·1030y. To improve this limit it seems necessary to use other methods which, however, are model dependent.

Thermoluminescence from the different layers of a recent core drilled in the Tyrrhenian Sea has been measured. The sedimentation rate of 0.115 cm y−1 previously determined by the210Pb−226Ra method allows the profile of TL to be obtained in the last 1500 years. We notice that sharp peaks in the TL intensity appear during the years in which records of hystorical supernovae explosions are given. A working model of the process based on the irradiation of dust in the upper atmosphere by γ-rays produced in the SN burst allows a satisfactory energy estimate of the observations to be done. Moreover, the profile shows the modulation of the irradiations of the Earth environment produced by the Sun in the past.

The integral response functions for cosmic-ray muons, at different muon threshold energies, are calculated by taking into account the nuclear composition of the primary cosmic radiation, and showing their contribution also at large zenith angles.

The results of the spectral analysis of the time variations of the thermoluminescence (TL) intensity measured at 4 y intervals in a recent Ionian Sea sediment core from 1500 A.D. to 1974 A.D. are presented. The presence of an 11 y wave is clearly demonstrated not only by the power spectral density analysis but also by two other methods:a) the superposition of the 11 y epochs andb) the stretching index of the 11 y cyclogram. Moreover, the fan map of the stretching index of the cyclograms at different perioditities shows that the oscillations in the band (11±0.5) y are regularly frequency-modulated on a time scale around 90 y. The two kind of periodicities could be related to the Schwabe and the Gleissberg cycles of solar activity which appear in phase with the TL cycles. We confirm, therefore, our previous suggestion that the TL profiles from sea sediments could be a useful tool for monitoring the solar-terrestrial effects in the past.

The profiles of the concentration of210Pb precipitated from the atmosphere are measured in Tyrrhenian Sea cores, all collected in about the same region. From the disequilibrium226Ra−210Pb the sedimentation rate has been found and its uniformity has been tested. The measured activities of210Pb unsupportedin situ in the different layers show an exponential behaviour as a function of depth, thus demonstrating that the sedimentation rate is constant. Moreover the fall-out has been estimated in two different cores, and the agreement is excellent (respectively 62 and 58 atoms/cm2 min). A case of mixing in the top layers during collection mishandling is also presented: the fluctuations in the activity measurements are evident and prevent the sedimentation rate to be univocally determined.

We present the results of a spectral analysis in the frequency domain of the fluctuations of cosmic rays extended to primary rigidity ∼250 GV. The experimental power spectrum is compared with that expected on the basis of the theory of interplanetary scintillations, Forbush effect and the effects of CM passages of solar recurrent active regions. The agreement confirms the influence of heliospheric phenomena up to 250 GV and the presence of nonlinear interactions between particles and interplanetary magnetic fields.

We describe here the LVD experiment (Large-Volume Detector) of the Gran Sasso Laboratory, which is the natural improvement of the LSD experiment (Liquid Scintillation Detector) running in the Mont Blanc Laboratory. The LVD ((31×13) m2 area, height 12 m) consists of ≈1800 tons of liquid scintillator and of a system of streamer tubes on 5 layers for reconstructing tracks of charged particles. As any experiment in an underground laboratory, which has a low statistics of events and requires long running times, the LVD is a multipurpose experiment but with different priorities of the researches. The main goal is neutrino astronomy, firstly detection of neutrinos from collapsing stars and secondly high-energy neutrinos and solar neutrinos. Since the expected number of interactions of neutrinos, from a stellar collapse is very high (of order of 900 for a collapse at the distance of the galactic centre), the LVD is, contrary to the present experiments, a real neutrino observatory, able to make a detailed analysis of the energy and temporal distributions of the burst. In addition to neutrino astrophysics, with the LVD experiment excellent possibilities exist to perform researches in cosmic-ray and high-energy elementary-particle physics.

In this paper we present the thermoluminescence profile of a Tyrrhenian sea core during the time interval 1577–1808 A.D. We have sampled the core every 0.5 cm, which is half the spacing used in a previous experiment covering the time interval 600–1600 A.D. This allows the TL behaviour to be determined every4.35 y. In this way the time series of the measurements can directly be tested for the presence of the 11 y solar cycle. The results obtained give support to the previous suggestion that the TL profile method can be used for monitoring solarterrestrial relations in the past.