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

Abstract

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. Subject headings : cosmic rays È elementary particles È ISM : abundances

The Alpha Magnetic Spectrometer (AMS) on the International Space Station: Part I – results from the test flight on the space shuttle

“…4.15 our data are only marginally in agreement with the spectrum used to calculate atmospheric neutrino spectra [31]. Our results are compared to recent balloon experiment results [23,28,53,54] in Fig. 4.16.…”

“…For comparision with balloon measurements [21,23,53,54] the data has been scaled by E 2:5 K as shown in Fig. 4.13.…”

“…12 The spectrum has been ÿt [45] over the rigidity range 20 ¡ R ¡ 200 GV. To avoid [23], LEAP [21], BESS [53], IMAX [54]. The systematic uncertainty in was estimated from the uncertainty in the track resolution (0.013) and the variation of the selection criteria (0.008).…”

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“…A precise knowledge of such spectra is of particular importance to interpret the observational data from muon and neutrino detectors deep underground [12]. The measurement of the primary proton spectrum has been performed by means of satellite and balloon borne experiments [13][14][15][16][17][18][19][20][21][22][23][24][25][26] and indirectly derived by using ground based detectors [27][28][29][30]. In the region of tens of TeV, however, direct measurements lack statistics and moreover their energy determinations are not calorimetric and depend on the interaction parameters and their fluctuations.…”

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“…Figure 1. Left: Calculated proton interstellar spectrum (LIS) and modulated spectrum (Φ = 750 MV) with data [8][9][10][11]. Right: Calculatedp interstellar spectrum (LIS) and modulated spectrum (Φ = 400 MV) with data [12,13].…”