Xin Wu


A compact detector for Gamma Ray Bursts photon polarization measurements

Chinese Space Station (CSS)
CAD models of a POLAR-2 polarimeter module and of the full instrument
POLAR-2 signing ceremony between CSU and UniGe (18 Nov 2019)
Readout setup for the first prototype of POLAR-2 polarimeter module
POLAR-2 SiPM array characterisation
First prototypes of POLAR-2 SiPM readout boards
POLAR-2 spectrometer first tests

Scientific goals of the mission

The POLAR-2 project aims to answer the most important open questions regarding the nature of Gamma-Ray Bursts (GRBs). These events are thought to be the most violent explosions in the Universe since the Big Bang. More than 50 years after their discovery, they remain one of the most researched topics in astrophysics and the origin of the gamma-ray emission from GRBs remains one of the most important unanswered questions in the field. This in spite of intense research by dedicated instruments over the last decades. As the research performed using the conventional methods appears to be inadequate in answering the open questions about GRBs, a novel investigation approach is required. Polarization measurements are perhaps the most promising of such novel approaches as indicated by the large number of theoretical publications devoted to the subject, highlighting their large discovery potential. The first significant set of reliable and detailed polarization measurements was produced recently by POLAR, an instrument fully dedicated to GRB polarimetry which performed data taking as the only international collaboration on the Chinese Tiangong-2 Space Lab. 

The POLAR-2 project aims to launch the next generation GRB polarimeters. This instrument is foreseen to detect approximately 250 GRBs per year and produce 30 polarization measurements per year in the 30-800 keV energy range with a precision higher or equal to those published by POLAR. POLAR-2 would furthermore be the most sensitive detector in its energy range, allowing it to observe even the weakest gamma-ray transients, such as those connected to gravitational waves, and provide triggers to other detectors, thereby increasing the scientific potential of such instruments. In addition to the most sensitive gamma-ray polarimeter ever launched the instrument will contain a set of dedicated spectrometers allowing it to perform detailed spectral and location measurements for GRBs. The POLAR-2 instrument thereby aims to not only make high energy polarization measurements a standard observable for GRB astrophysics but will also play an important role in the upcoming field of multi-messenger astrophysics. 

In summer 2019 the instrument was selected for launch to the China Space Station during early 2024 after which it is foreseen to perform data taking for at least 2 years.

POLAR-2 has the status of CERN Recognized Experiment (RE40) since March 2020.

The POLAR-2 collaboration

The construction of the POLAR-2 Detector is performed in Europe and China by the following institutes:


University of Geneva (Department for Particle and Astroparticle Physics & Observatory):

Xin Wu:     PI of the POLAR-2 project
Merlin Kole:     Project Manager
Nicolas Produit:     Head of POLAR-2 online software system
Jérôme Stauffer:     Head of Front-End development
Nicolas De Angelis:     Detector module development and calibration
Franck Cadoux:     Head of POLAR-2 Mechanics
Johannes Hulsman:     Simulation development
Hancheng Li:     Post-doc at observatory for POLAR/POLAR-2

NCBJ, Poland:

Agnieszka Pollo:     Polish PI
Dominik Rybka:     Head of Back-End development and Low Votage Power Supply development
Slawomir Mianowski:     Component level irradiation tests
Adam Zadrozny:     Online software development

MPE, Germany:

Jochen Greiner:     German PI / Head of spectrometer development MPE
J. Michael Burgess:     POLAR-2 Project scientist

IHEP, China:

Shuang-Nan Zhang:     Chinese PI
Jianchao Sun:     Head of POLAR-2 acceptance test/spectrometer development IHEP
Bobing Wu:     Prof at IHEP working on POLAR/POLAR-2

Open positions

No open position for the moment.

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