Wolfgang Menn

A time-of-flight scintillator system (ToF) has been developed for the PAMELA satelliteborne cosmi... more A time-of-flight scintillator system (ToF) has been developed for the PAMELA satelliteborne cosmic ray experiment, mounted on the Resurs DK1 satellite and launched from the Baikonur cosmodrome on June 15 th 2006. PAMELA was built to measure charged particles in the cosmic radiation with a particular focus on antiparticles. The ToF scintillator system provides the fast trigger to the experiment, the rejection of albedo particles, and in combination with a magnetic spectrometer the possibility to distinguish electrons from anti-protons up to about ~1 GeV and to separate light isotopes at low energies. Ionising energy loss measurements in the scintillator planes allow the absolute charge of traversing particles to be determined. The in-orbit performance of the ToF system is presented.

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The Absolute Flux of Protons and Helium at the Top of the Atmosphere Using IMAX

Astrophysical Journal, 2000

The cosmic-ray proton and helium spectra from 0.2 GeV nucleon~1 to about 200 GeV nucleon~1 have b... more The cosmic-ray proton and helium spectra from 0.2 GeV nucleon~1 to about 200 GeV nucleon~1 have been measured with the balloon-borne experiment Isotope Matter-Antimatter Experiment (IMAX) launched from Lynn Lake, Manitoba, Canada, in 1992. IMAX was designed to search for antiprotons and light isotopes using a superconducting magnet spectrometer together with scintillators, a time-of-Ñight system, and Cherenkov detectors. Using redundant detectors, an extensive examination of the instrument efficiency was carried out. We present here the absolute spectra of protons and helium corrected to the top of the atmosphere and to interstellar space. If demodulated with a solar modulation parameter of / \ 750 MV, the measured interstellar spectra between 20 and 200 GV can be represented by a power law in rigidity, with (1.42^0.21) ] 104R~2.71B0.04 (m2 GV s sr)~1 for protons and (3.15^1.03) ] 103R~2.79B0.08 (m2 GV s sr)~1 for helium.

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Measurement of 0.25-3.2 GeV Antiprotons in the Cosmic Radiation

Physical Review Letters, 1996

The balloon-borne Isotope Matter-Antimatter Experiment (IMAX) was flown from Lynn Lake, Manitoba,... more