Harald Schieler

Test of high-energy interaction models using the hadronic core of EAS

Using the large hadron calorimeter of the KASCADE experiment, hadronic cores of extensive air showers have been studied. The hadron lateral and energy distributions have been investigated in order to study the reliability of the shower simulation program CORSIKA with respect to particle transport, decays, treatment of low-energy particles, etc. A good description of the data has been found at large distances from the shower core for several interaction models. The inner part of the hadron distribution, on the other hand, reveals pronounced differences among interaction models. Several hadronic observables are compared with CORSIKA simulations using the QGSJET, VENUS and SIBYLL models. QGSJET reproduces the hadronic distributions best. At the highest energy, in the 10 PeV region, however, none of these models can describe the experimental data satisfactorily. The expected number of hadrons in a shower is too large compared with the observed number, when the data are classified according to the muonic shower size.

Radar reflection off extensive air showers

We investigate the possibility of detecting extensive air showers by the radar technique. Considering a bistatic radar system and different shower geometries, we simulate reflection of radio waves off the static plasma produced by the shower in the air. Using the Thomson cross-section for radio wave reflection, we obtain the time evolution of the signal received by the antennas. The frequency upshift of the radar echo and the power received are studied to verify the feasibility of the radar detection technique.

Characterization of Hamamatsu 64-channel TSV SiPMs

Abstract The Hamamatsu UV-light enhanced 64-channel SiPM array of the newest generation ( S13361-3050AS-08 ) has been examined for the purpose of being used for the Silicon Elementary Cell Add-on (SiECA) of the EUSO-SPB balloon experiment. At a room temperature of 19 . 5 ° C , the average measured breakdown voltage of the array is ( 51 . 65 ± 0 . 11 ) V, the average gain is measured to ( 2 . 10 ± 0 . 07 ) ⋅ 1 0 6 and the average photon detection efficiency results to ( 44 . 58 ± 1 . 80 ) % at a wavelength of ( 423 ± 8 ) nm and a bias voltage of 55 . 2 V. The average dark-count rate is ( 0 . 69 ± 0 . 12 ) MHz, equivalent to a dark count rate per SiPM area of ( 57 ± 12 ) kHz ∕ mm 2 , and the crosstalk probability is measured to ( 3 . 96 ± 0 . 64 ) % . These results confirm the information given by the manufacturer. Measurements performed with the newly installed Single Photon Calibration Stand at KIT (SPOCK) show the improved sensitivity to photons with wavelengths lower than 400 nm compared to the SiPM array S12642-0808PA-50 , which was also investigated for comparison. Additional measurements confirm the strong temperature dependence of the SiPM characteristics as given in the data sheet. All the characterized parameters appear to be sufficiently uniform to build up a focal surface of SiPM arrays fulfilling the requirements for a telescope detecting photons in the UV range.

Ground Calibration of MAPMT and SiPM for JEM-EUSO

In order to unveil the mystery of ultra-high energy cosmic rays (UHECRs), JEM-EUSO (Extreme Universe Space Observatory on-board Japanese Experiment Module) will observe extensive air showers induced by UHECRs from the International Space Station (ISS) orbit with a huge acceptance. To discuss the origin of UHECRs precisely with the observed results, it is essential to calibrate the detector pre-flight with utmost precision. The technical readiness level of JEM-EUSO is demonstrated with several pathfinder missions, e. g. EUSO-Balloon, EUSO-TA, and Mini-EUSO. These pathfinder missions also provide the perfect environment to investigate the capability of new state of the art photo sensors based on Geiger mode avalanche photodiodes (G-APDs), so called silicon photomultipliers (SiPMs). A first concept design for a JEM-EUSO elementary cell based on SiPMs is presented to be used with one of the pathfinder experiments. For the case of EUSO-TA comparison studies have been performed for MAPMTand SiPM-response to fluorescence light. To absolutely calibrate and characterize different types of photo sensors, an universal calibration and test setup is built at the Karlsruhe Institute of Technology (KIT). It consists of a photon shielding dark box (1.5 m×1 m×1 m), a diffuse uniform light source with a calibrated optical output and several readout electronics for MAPMTs and SiPMs. The light source can be used in singlephoton mode (pulsed light) and other modes, ranging from a few tens of photons to continuous light. The spectral output is around (377±6) nm. Further wavelengths will be implemented with respect to the emission lines of the nitrogen fluorescence spectrum. Former measurements with SiPMs have shown a temperature dependence of dark count and gain. Therefore, a temperature control has been implemented into the setup. With this the photo detection efficiency of various photo sensors can be measured for different wavelengths and temperatures. The present status of the calibration and test setup as well as of the design and comparison studies with SiPMs will be reported.