PAMELA - A Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics

TL;DR

PAMELA addresses the measurement of charged cosmic-ray antiparticles with high precision across a broad energy range, enabling tests of cosmic-ray propagation, solar modulation, and potential dark matter signatures. The instrument integrates a 0.43 T permanent magnet spectrometer with six silicon planes, a time-of-flight system, a silicon-tungsten electromagnetic calorimeter, anticoincidence shields, a shower tail catcher, and a helium-3 neutron detector, all managed by a space-qualified data acquisition and trigger chain. The paper presents the design, space qualification, and on-ground performance (beam tests and pre-flight data), with in-orbit performance to be discussed in future publications. The anticipated high statistics (e.g., antiprotons and positrons) and sensitivity to antihelium allow stringent tests of standard propagation models and potential exotic sources such as dark matter annihilations.

Abstract

The PAMELA experiment is a satellite-borne apparatus designed to study charged particles in the cosmic radiation with a particular focus on antiparticles. PAMELA is mounted on the Resurs DK1 satellite that was launched from the Baikonur cosmodrome on June 15th 2006. The PAMELA apparatus comprises a time-of-flight system, a magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail catcher scintillator and a neutron detector. The combination of these devices allows antiparticles to be reliably identified from a large background of other charged particles. This paper reviews the design, space qualification and on-ground performance of PAMELA. The in-orbit performance will be discussed in future publications.

Figures (27)

• Figure 1: Recent experimental ${\rm \overline{p}}$ spectra (BES-S00 and BES-S99 asa02, AMS agu02, CAPRICE98 boe01a, BES-S95+97 ori00, MASS91 bas99, CAPRICE94 boe97, IMAX92 mit96) along with theoretical calculations for pure ${\rm \overline{p}}$ secondary production (solid lines: sim98, dashed line: ber99b) and for pure ${\rm \overline{p}}$ primary production (dotted line: ull99, assuming the annihilation of neutralinos of mass 964 GeV/c$^2$). The expected PAMELA performance, in case of a pure secondary component (full boxes) and of an additional primary component (full circles), are indicated. Only statistical errors are included in the expected PAMELA data.
• Figure 2: The positron fraction as a function of energy measured by several experiments (gol87mul87cle96 and MASS89 gol94, TS93 gol96, HEAT94+95 bar98, CAPRICE94 boe00, AMS alc00, CAPRICE98 boe01b, HEAT00 bea04). The dashed pro82 and the solid mos98 lines are calculations of the secondary positron fraction. The dotted line is a possible contribution from annihilation of neutralinos of mass 336 GeV/c$^2$bal99. The expected PAMELA performance, for a pure secondary component (full boxes) and of an additional primary component (full circles), are indicated. Only statistical errors are included in the expected PAMELA data.
• Figure 3: The ratio of anti-helium to helium in the cosmic radiation shown as a function of rigidity hebar. No observation of antihelium has been made to date and so upper limits are shown. The expectation for PAMELA after a 3 year long mission is shown.
• Figure 4: The PAMELA instrument. Top: a schematic overview of the apparatus. Bottom: a photograph taken just prior delivery to Russia for integration with the Resurs DK1 satellite. The detector is approximately 1.3 m tall. The magnetic field lines in the spectrometer are oriented along the y direction.
• Figure 5: A schematic overview of the Time of Flight system. The distance between the S1 and S3 planes is 77.3 cm.