Speaker
Dr
Angela Gligorova
(CERN)
Description
In antimatter research, the detection and tagging of antiprotons and antihydrogen is usually achieved through the tracking of the annihilation products. In some instances, however, it proves useful to have the antiprotons annihilating directly within the detector volume, with the potential of sensibly improving the resolution on the position determination.
The AEgIS collaboration at CERN aims to study antimatter gravity, i.e. to directly measure the free fall of antihydrogen with a precision of the order of few percent. The design of the experiment requires detection of antihydrogen annihilations with a resolution on the position of the order of 10 um. The R&D of such a position sensitive detector included evaluation of different detector technologies for direct antiproton annihilation.
The first tests and measurements of direct antiprotons annihilations were performed in 2012 on monolithic active pixel and 3D sensors within the main AEgIS apparatus. The promising results lead to the development of a dedicated facility for detector tests and R&D, GRACE, which is operational since 2015. This beam line makes use of the secondary branch of the existing antiproton beam line at the Antiproton Decelerator, which it shares with the AEgIS experiment. GRACE exploits simple beam optics and an electrostatic deflector to provide antiprotons with very low energy (1-8 keV).
Over the last two years GRACE has been employed to study the performance of the Timepix3 as a direct annihilation detector. The Timepix3 is an ASIC developed within the Medipix3 collaboration, characterized by an extremely high spatial resolution and accurate TOA (time-of-arrival) and TOT (time-over-threshold) information. For our application, the Timepix3 chip was coupled to a particularly thick (675 um) silicon sensor, allowing a much-improved tracking length. These characteristics make it ideal to tag the typical signature of antiproton annihilation, where several charged products depart from the annihilation point, with typical energies of hundreds of MeV, creating a signature star-shaped event.
Part of the beam time on GRACE was used for antiproton annihilation measurements with CsI crystals, Cr-39 foils, as well as cryogenic tests of the Timepix3 detector.
The talk will include an overview of the AEgIS experiment, as well as data analysis and results from several test beams on GRACE with different detector technologies.
Primary author
Dr
Angela Gligorova
(CERN)
