PAMELA detector
Organization | PAMELA group |
---|---|
Mission Type | Cosmic Ray
|
Host Satellite | Resurs DK1
|
Launch | 15 June 2006 |
Launch vehicle | Soyuz-FG |
Launch site | Baikonur Cosmodrome |
Mission duration | 3 years (planned), 9 years, 7 months and 23 days (achieved) |
Mission end | 7 February 2016 |
Mass | 470 kg |
Max length | 1300 mm |
Power consumption | 335 Watts |
Webpage | PAMELA homepage |
Orbital elements (Resurs DK1) | |
Inclination
|
70 degrees |
Orbit | quasi-polar elliptical |
Min altitude | 360 km |
Max altitude | 604 km |
Period | 94.02 min |
PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) was a
Development and launch
PAMELA was the largest device up to the time built by the Wizard collaboration, which includes Russia, Italy, Germany and Sweden and has been involved in many satellite and balloon-based cosmic ray experiments such as Fermi-GLAST. The 470 kg, US$32 million (EU€24.8 million, UK£16.8 million) instrument was originally projected to have a three-year mission. However, this durable module remained operational and made significant scientific contributions until 2016.
PAMELA is mounted on the upward-facing side of the
on 15 June 2006. PAMELA has been put in a polar elliptical orbit at an altitude between 350 and 610 km, with an inclination of 70°.Design
The apparatus is 1.3 m high, has a total mass of 470 kg and a power consumption of 335 W. The instrument is built around a permanent magnet spectrometer with a silicon microstrip tracker that provides rigidity and dE/dx information. At its bottom is a silicon-tungsten imaging calorimeter, a neutron detector and a shower tail scintillator to perform lepton/hadron discrimination. A Time of Flight (ToF), made of three layers of plastic scintillators, is used to measure the velocity and charge of the particle. An anticounter system made of scintillators surrounding the apparatus is used to reject false triggers and albedo particles during off-line analysis.[5]
Particle | Energy Range |
---|---|
Antiproton flux | 80 MeV – 190 GeV |
Positron flux | 50 MeV – 270 GeV |
Electron flux | up to 400 GeV |
Proton flux | up to 700 GeV |
Electron/positron flux | up to 2 TeV |
Light nuclei (up to Z=6) | up to 200 GeV/n |
Light isotopes (D, 3He) | up to 1 GeV/n |
Antinuclei search | sensitivity better than 10−7 antiHe/He |
Results
Preliminary data (released August 2008, ICHEP Philadelphia) indicate an excess of positrons in the range 10–60 GeV. This is thought to be a possible sign of dark matter annihilation:[6][7] hypothetical
The first two years of data were released in October 2008 in three publications.[8][9] The positron excess was confirmed and found to persist up to 90 GeV. Surprisingly, no excess of antiprotons was found. This is inconsistent with predictions from most models of dark matter sources, in which the positron and antiproton excesses are correlated.
A paper, published on 15 July 2011, confirmed earlier speculation that the
Boron and carbon flux measurements were published in July 2014,[14] important to explaining trends in cosmic ray positron fraction.[15]
The summary document of the operations of PAMELA was published in 2017.[2]
Sources of error
Between 1 and 100 GeV, PAMELA is exposed to one hundred times as many electrons as antiprotons. At 1 GeV there are one thousand times as many protons as positrons and at 100 GeV ten thousand times as many. Therefore, to correctly determine the antimatter abundances, it is critical that PAMELA is able to reject the matter background. The PAMELA collaboration claimed in "The electron hadron separation performance of the PAMELA electromagnetic calorimeter" that less than one proton in 100,000 is able to pass the calorimeter selection and be misidentified as a positron when the energy is less than 200 GeV.
The ratio of matter to antimatter in cosmic rays of energy less than 10 GeV that reach PAMELA from outside the
See also
- AMS-02 is a high energy physics experiment mounted to the exterior of the International Space Station featuring advanced particle identification and large acceptance of 0.3m2sr. AMS-02 has been in operation since May 2011. More than 100 billion charged cosmic ray events were recorded by AMS so far.
References
- ^ a b c Vincenzo Buttaro (ed.). "The Space Mission PAMELA". Retrieved 4 September 2009.
- ^ S2CID 119078426.
- ^ "Recognized Experiments at CERN". The CERN Scientific Committees. CERN. Retrieved 20 January 2020.
- ^ "RE2B/PAMELA : A Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics". CERN. Retrieved 20 January 2020.
- S2CID 119608020.
- PMID 18704050.
- S2CID 73574983.
- S2CID 119187767.
- S2CID 11675154.
- .
- ^ Than, Ker (10 August 2011). "Antimatter Found Orbiting Earth—A First". National Geographic Society. Archived from the original on 10 October 2011. Retrieved 12 August 2011.
- Science. Archived from the originalon 24 October 2011. Retrieved 12 August 2011.
- ^ Chung, Emily (8 August 2011). "Antimatter belt surrounds Earth". CBC News. Retrieved 12 August 2011.
- S2CID 53002540.
- S2CID 96470471.