Speaker
Mr
Michael Karus
(KIT)
Description
The JEM-EUSO mission strives for the UV-fluorescence detection of extremely high energy cosmic rays (EHECRs) from space using Earth's atmosphere as a calorimeter. Further scientific goals are the identification of sources and source regions for EHECRs. JEM-EUSO will also be used to examine Neutrinos, Gammarays, the galactic magnetic fields, meteors and meteoroids as well as Earth’s atmosphere. The JEM-EUSO telescope consists of three Fresnel lenses and a focal surface made of multi-anode photomultiplier tubes (MAPMTs). The telescope will be attached to the International Space Station (ISS). With a very large field of view of 60° and the ISS-Orbit of 400 km altitude, the JEM-EUSO telescope will have an observation area on ground of around 1.4*105 km2. The detection of extensive air showers (EASs) will be done via UV-light detection. The main component of EASs are electrons which excite Nitrogen molecules of the atmosphere and thus produce isotropic fluorescence light. The particles in EASs travel faster than the speed of light in air and produce Cherenkov light directed towards the Earth. The ultraviolet fluorescence light as well as reflected and scattered Cherenkov light will be detected by the JEM-EUSO telescope. The focal surface (FS) consists of roughly 5000 MAPMTs located on the surface of a sphere with a radius of 2.5m. Every MAPMT has 8x8 pixels and is glued with an UV-filter that transmits UV-light from 330nm – 400nm. Four MAPMTs form one elementary cell (EC) and nine ECs form one photo detector module (PDM). 137 of these PDMs form the whole FS of the telescope. For fluorescence detection of cosmic rays it is essential to calibrate the detector pre-flight with utmost precision and to monitor the performance of the detector throughout the whole mission time.
Through the complex structure of the MAPMTs special boards for power supply and signal extraction had to be designed. The front-end readout is achieved by custom made electronics using 64-channel ASICs that process data from one MAPMT. Because of recent developments in the field of Silicon photomultipliers (SiPM) these alternative devices for photon detection are very interesting for the JEM-EUSO mission. In comparison to MAPMTs they require no high voltage, are much lighter and are not as prone to high magnetic fields as MAPMTs. However, they still have a high temperature dependency, are not optimized for the wavelength spectrum of fluorescence light, and need a faster readout. With the present development of integrated SiPM-ASICs with fast readout an application for JEM-EUSO seems possible.
In this contribution a short overview of the JEM-EUSO mission and a description of the present calibration device and procedure is given. We will further discuss our ideas for future SiPM use within JEM-EUSO.
Primary author
Mr
Michael Karus
(KIT)
