Last Update: October 2000

WiZard (Trieste, Firenze, Roma 2, LNF, Bari)

ITALIAN COLLABORATION (P.I. Prof. P.G. PICOZZA)

Sezione INFN e Dipartimento di FISICA Tor Vergata

V. Bidoli, M. Casolino,V. Cocco, M.P. De Pascale, G. Furano, A. Morselli, L. Narici, P.Picozza, C. Pittori, A. Salamon, R.Sparvoli

Sezione INFN e Dipartimento di INGEGNERIA ELETTRONICA

S. Bertazzoni, R. Cardarilli, M. Iannuccelli, A. Salsano

Sezione INFN e Dipartimento di FISICA Trieste

G. Barbiellini, M. Boezio, W. Bonvicini, U. Bravar, P. Schiavon, A. Vacchi, N. Zampa

Sezione INFN, Dipartimento di FISICA e IROE Firenze

O. Adriani, G. Castellini, R. DAlessandro, N. Finetti, M. Grandi, P.Papini, A.Perego, S. Piccardi, P. Spillantini, F. Taccetti, V. Vignoli

Sezione INFN e Dipartimento di FISICA Bari

M.L. Ambriola, R. Bellotti, F. Cafagna, F.Ciacio, M.Circella, G. De Cataldo, C.N. De Marzo, N. Giglietto, B. Marangelli, N. Mirizzi, P. Spinelli

Laboratori Nazionali INFN Frascati

S. Bartalucci, G. Mazzenga, L. Marino, M. Ricci

INTERNAZIONAL COLLABORATION

New Mexico State University, Las Cruces, NM, USA

NASA/Goddard Space Flight Center, Maryland, USA

Royal Institute of Technology, Stockholm, Sweden

Univesitat Siegen, Siegen, Germany

Centre de Recherches Nucleaires, Strasbourg-Cedex, France

Tata Institute of Fundamental Research, Bombay, India

MEPHI, Mosca, Russia

LEBEDEV, Mosca, Russia

IMBP, Mosca, Russia

IOFFE, S. Pietroburgo, Russia

1. Goal of the experiment

The WIZARD experimental program is devoted to the extensive study of cosmic ray spectra (particles, antiparticles, isotopes, abundances and search for antimatter) in several energy ranges achievable through different apparata on board stratosferic balloons and long duration satellite missions.

Balloon program

The first WIZARD balloon flight dates back to the 1989 and after that four more successful launches (1991, 1993, 1994, 1997-98) took place. CAPRICE98 (Cosmic AntiParticle Ring Imaging Cherenkov Experiment,1998) is the latest detector built and flown by the WIZARD collaboration. The CAPRICE98 instrument is composed of a superconducting magnet spectrometer associated to a tracking system made of three drift chambers, a gas RICH, a Time of Flight system and a silicon-tungsten electromagnetic calorimeter. The CAPRICE98 primary science goals were to measure the absolute spectra of positrons and antiprotons up to 50 GeV along with muon spectra in the atmosphere. A large part of positrons and antiprotons impinging on Earth are produced in high-energy interactions between cosmic rays nuclei with the interstellar medium. Their spectra can provide an insight on the origin, production and propagation of cosmic rays in our galaxy. Any observed flux larger than that predicted by the Leaky Box Model (LBM), the ``standard'' model of cosmic ray propagation, could indicate exotic sources of antimatter. The predictions of the propagation models are different above 10 GeV where more refined measurements are needed.

Muon energy spectra at different atmospheric depths are considered extremely important in the context of the atmospheric neutrino anomaly since they can help normalize the Monte Carlo predictions of neutrino fluxes. Recently, the importance of the primary spectra, used as an input for these calculations, has been pointed out; therefore, it is important to measure together primary and secondary spectra with the same detector, in the same day, in order to reduce systematic errors.

CAPRICE98 was successfully launched on the 28th of May 1998 from Ft. Sumner, NM, USA (340N,1040W), using the NASA National Science Balloon Facility (NSBF). The effective geomagnetic vertical cut-off is 4 GV/c for this site. The payload flew for 20h at a float altitude of 5g/cm2, corresponding to about 36 Km. More than 5 million triggers were collected during the flight and all detectors performed normally.

Satellite program

NINA and NINA/MITA missions

The mission NINA-1 has been conceived to detect cosmic ray nuclei of galactic, solar or anomalous origin, from hydrogen to iron, between 10 and 200 MeV/n in regime of full containment, and up to a few GeV/n when the particles cross the detector. The experiment is carried out on board the satellite Resurs-01 n.4, developed by the Russian Space Company VNIIEM, which was launched in July 1998 from the base of Baikonur (Kazakistan) towards a polar sun-synchronous orbit at 840 km of altitude.

The weight and electric power of the complete telescope are respectively 40 kg and 40 W, in accordance with the constraints imposed by the satellite.

NINA-1, as per contract with the Russian Space Agency, has taken data until the end of 1999. During the year 1999 most of the work has been concentrated in the mission control and data taking and analysis. Results span over nuclear and isotopic composition of low energy cosmic particles, galactic cosmic rays, solar energetic particles and anomalous cosmic rays.

NINA-1 has been joined in space by a twin detector, NINA-2, also placed in a polar orbit but at a lower altitude (450 Km). NINA-2 is housed on board the Italian Space Agency Satellite MITA which was launched on July 2000 from the Plesetsk launch site in Russia by means of a Cosmos launcher.

NINA-2 mission plans to continue the NINA-1 mission extending its observational characteristics over time. NINA-2 was selected as the first payload of the technological flight of the satellite MITA. The detector is identical to the first one but makes use of the extensive computer and telemetry capabilities of MITA to improve active data acquisition time.

PAMELA mission

The observational objectives of the PAMELA experiment are the measurement of the spectra of antiprotons, positrons and nuclei in a wide range of energies, to search for primordial antimatter and to study the cosmic ray fluxes over half a solar cycle. The physical issues addressed by these observations include:

1. Role of Grand Unified Theories in Cosmology in relation to antimatter and dark matter.
2. Processes of acceleration and propagation of cosmic rays.
3. The relationship between solar, terrestrial and heliospheric processes and energetic particle propagation in the heliosphere.

This will be obtained through observation of:

1. Antiproton spectrum from 80 MeV to 100 GeV (current limit 12 GeV).
2. Positron spectrum from 80 MeV to 100 GeV (current limit 30 GeV).
3. Search of antinuclei with sensitivity of 10-8 for antihelium/helium ratio (two orders of magnitude above current measurements).
4. Study of energetic and temporal distribution of solar flare phenomena.

The PAMELA experiment will be installed on the up-ward side of the Resource-01 n.5 satellite that will be continuously oriented down-ward to the Earth during all its mission, in order to fulfill a program of Earth surface observation. Furthermore the satellite will travel in a quasi-circular, about 690 km high, polar orbit with inclination of 98.5 deg. This is an optimal situation for the observation of cosmic rays.

2. Physics achievements during 2000

Balloon program

The data collected in the recent balloon flights have been analyzed. A new measurement of the electron and positron spectra during the solar minimum activity have been published. The absolute energy spectra were determined in the region at the top of the atmosphere between 0.46 and 43.6 GeV for electrons and between 0.46 and 14.6 GeV for positrons. The observed positron spectra and the positron fraction are consistent with a pure secondary origin. Proton and helium spectra, gathered during the same flights, have been measured as well: they are in good agreement with other recent measurements over 10 GeV.

Satellite program

NINA and NINA/MITA missions

With the NINA payload, it has been possible to study nine Solar Energetic Particles events (SEP). For each of these events it has been possible to reconstruct the spectrum of 4He in the energy range 10-50 MeV/n; the power-law behaviour has spectral indexes varying from 1.78 up to 6.80. The ratio 3He/4He has been calculated and shows the enrichment in 3He in some of the SEP events. The helium isotope masses have been reconstructed with a resolution of 0.16 amu. One SEP shows a high flux of heavy particles: it allows, then, to reconstruct carbon and oxygen fluxes.

The behaviour of the NINA/MITA payload in several solar flares events is under analysis.

PAMELA mission

Activity in the year 2000 has been carried on the development of the qualification model of the instrument for each detector involved. Calibrations and beam tests have been performed at CERN and specific vibration, thermal and electromagnetic tests have taken place at different european facilities for space qualification. The assembly and integration laboratory, provided with two clean rooms, has been completed at the INFN Section of Roma 2. Radiation hardness tests of electronic components have been performed at INFN Laboratori Nazionali del Sud, Catania, at the ENEA Casaccia irradiation facility and at GSI, Darmstadt to verify and characterize such components for radiation tolerance in space.

3. INFN contribution to the experiment in terms of manpower and financial support

Manpower: 25 researchers, 4 technicians and the electronics and mechanics workshops in the five INFN sections.

Financial INFN support: 1340 ML

4. Number of publications in refereed journals

4

5.Number of talks to conferences

10

6.Number of undergraduate and doctoral thesis on the experiment

Undergraduate: 6

Doctoral thesis: 4

7. Leadership role in the experiment

- Spokeperson of the WiZard International Collaboration is Piergiorgio Picozza, from Roma 2 Section.

- Spokeperson of the Russian Italian Mission is Piergiorgio Picozza, from Roma 2 Section.

- Scientific Principal Investigator for the satellite programs is Piero Spillantini, from Firenze Section.

- System Manager of the PAMELA experiment is Guido Castellini, from Firenze Section.

8. Innovative instruments

The technological significance of the WiZard activities are:

- R&D of straw tubes for space applications.

-development of space qualified electronics for system controls and data taking (CPU, Mass Memories, memory pipelines).

- radiation hardness qualification for memory chips.

9. Competing experiments

Balloon flights. Competing experiments: BESS, for antiproton search, HEAT for electron/positron spectra.

NINA, NINA/MITA. No competing experiments at present.

PAMELA. Competing experiments: AMS for antinuclei search.

10. International Committee which has reviewed the experiment