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Scientists Are Fine-tuning China's "Monkey King" Dark Matter Probe

Jan 25, 2016     Email"> PrintText Size

China's first dark matter probe 'Monkey King' is returning data and being calibrated in order to produce more accurate data, scientists have revealed.

The Dark Matter Particle Explorer (DAMPE) Satellite, named "Wukong" (Monkey King) from the epic Journey to the West by a public competition, was launched on a Long March 2D rocket from the Jiuquan Satellite Launch Centre in December.

Since then, Wukong has been in a Sun-synchronous orbit, carrying out both indirect detection of dark matter and studies into high energy cosmic rays, returning around 20GB of data per day. 

Chang Jin, DAMPE chief scientist and vice director of Purple Mountain Observatory of the Chinese Academy of Sciences in Nanjing, told Xinhua that Wukong has already collected more than 100 million high energy particles, including protons, alpha and cosmic-ray particles and nuclides. 

Dark matter particles do not interact with or emit electromagnetic radiation, meaning we are unable to see them directly. Therefore DAMPE is looking to make indirect detection.

The 1,900kg probe has four main payloads - a plastic scintillator detector, a silicon-Tungsten Tracker, a BGO calorimeter and a neutron detector - together comprising around 76,000 mini detectors. 

The design of the DAMPE/Wukong (credit: Chinese Academy of Sciences) 

Professor Fan Yizhong, a member of the DAMPE team, told gbtimes the probe is using these instruments to measure the spectra of gamma rays and cosmic rays with very high energy resolution. 

Fan explains that dark matter particles may annihilate or decay to produce high energy gamma rays or cosmic rays, and in particular electron/positron pairs. If so, DAMPE should be able to pick up the signals.
Crucially, the satellite is believed to have the most sensitive and accurate detectors designed for dark matter, and could thus make a big contribution.

"Now the payload looks perfect, but it's not enough. If the calibration goes well, the signs we seek will pop out from the data," Chang said.

Another team member, Zang Jingjing, told Xinhua all the data will be analysed by a special computer equipped with 128 10-cored CPUs.

"After calibration, the detectors will collect more useful data and screen out signal noises. That will save us a lot of time," said Zang.

Wukong, built in collaboration with the University of Geneva and Italian universities in Bari, Lecce and Perugia and tested at CERN, is designed to operate for a lifetime of at least three years, with scientists hoping it will last five years.

Constant interaction with high-energy particles means it will need to undergo constant calibration during its mission. Initial data is expected to be released after six months.

The hunt for dark matter

The nature of dark matter to be one of the most fundamental questions for physicists and astrophysicists. There is believed to be around five times more dark matter than normal matter in terms of the mass-energy make-up of the universe.   

Chris Impey, distinguished professor of astronomy at the University of Arizona, explains that while scientists don't know what dark matter is, they know it is there, and discovering its nature is a question of fundamental importance.

"The dark matter particle is an extension to the otherwise very successful standard model of particle physics, most probably the lightest stable particle in models of supersymmetry.

"But awkwardly for this expectation, the LHC [Large Hadron Collider at CERN] has not affirmed the most likely supersymmetry models, so the battleground has shifted to a set of underground physics detectors trying identify the particle by its occasional and weak interactions with normal matter.

"Hence the intense interest in astronomy missions like DAMPE that have a chance of pinning down dark matter or giving us a clue to its nature.

"The stakes are very high and it's is one of the biggest unanswered questions in both physics and astronomy."


(Editor: CHEN Na)



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