Jens Buss

Online analysis of high-volume data streams in astroparticle physics

Experiments in high-energy astroparticle physics produce large amounts of data as continuous high-volume streams. Gaining insights from the observed data poses a number of challenges to data analysis at various steps in the analysis chain of the experiments. Machine learning methods have already cleaved their way selectively at some particular stages of the overall data mangling process. In this paper we investigate the deployment of machine learning methods at various stages of the data analysis chain in a gamma-ray astronomy experiment. Aiming at online and real-time performance, we build up on prominent software libraries and discuss the complete cycle of data processing from raw-data capturing to high-level classification using a data-flow based rapid-prototyping environment. In the context of a gamma-ray experiment, we review user requirements in this interdisciplinary setting and demonstrate the applicability of our approach in a real-world setting to provide results from high-volume data streams in real-time performance.

FACT - The G-APD revolution in Cherenkov astronomy

Since two years, the FACT telescope is operating on the Canary Island of La Palma. Apart from its purpose to serve as a monitoring facility for the brightest TeV blazars, it was built as a major step to establish solid state photon counters as detectors in Cherenkov astronomy. The camera of the First G-APD Cherenkov Telesope comprises 1440 Geiger-mode avalanche photo diodes (G-APD), equipped with solid light guides to increase the effective light collection area of each sensor. Since no sense-line is available, a special challenge is to keep the applied voltage stable although the current drawn by the G-APD depends on the flux of night-sky background photons significantly varying with ambient light conditions. Methods have been developed to keep the temperature and voltage dependent response of the G-APDs stable during operation. As a cross-check, dark count spectra with high statistics have been taken under different environmental conditions. In this presentation, the project, the developed methods and the experience from two years of operation of the first G-APD based camera in Cherenkov astronomy under changing environmental conditions will be presented.

FACT - Calibration of Imaging Atmospheric Cerenkov Telescopes with Muon Rings

M. Nothe∗, a M. L. Ahnen b, M. Balbo c, M. Bergmann d , C. Bockermann e, A. Biland b, T. Bretz b, K. A. Brugge a, J. Buss a, D. Dorner d , S. Einecke a, J. Freiwald a, C. Hempfling d , D. Hildebrand b, G. Hughes b, W. Lustermann b, K. Mannheim d , K. Meier d , K. Morik e, S. Muller b, D. Neise b, A. Neronov c, A.-K. Overkemping a, A. Paravac d , F. Pauss b, W. Rhode a, F. Temme a, J. Thaele a, S. Toscano c, P. Vogler b, R. Walter c, and A. Wilbert d Email: maximilian.noethe@tu-dortmund.de

FACT-Tools: Streamed Real-Time Data Analysis

K. A. Brügge b∗, M. L. Ahnena, M. Balboc, M. Bergmannd , A. Bilanda, C. Bockermanne, T. Bretza, J. Bussb, D. Dornerd , S. Eineckeb, J. Freiwaldb, C. Hempflingd , D. Hildebranda, G. Hughesa, W. Lustermanna, K. Mannheimd , K. Meierd , K. Morike, S. Müllera, D. Neisea, A. Neronovc, M. Nötheb, A.-K. Overkempingb, A. Paravacd , F. Paussa, W. Rhodeb, F. Temmeb, J. Thaeleb, S. Toscanoc, P. Voglera, R. Walterc, and A. Wilbertd Email: kai.bruegge@tu-dortmund.de

FACT - Status and Experience from Three Years Operation of the First SiPM Camera

A. Biland∗a, M. L. Ahnena, M. Balbob, M. Bergmannc, T. Bretza,1, K. A. Brugged , J. Bussd , D. Dornerc, S. Einecked , J. Freiwaldd , C. Hempflingc, D. Hildebranda, G. Hughesa, W. Lustermanna, K. Mannheimc, K. Meierc, S. Mullera, D. Neisea, A. Neronovb, M. Nothed , A.-K. Overkempingd , A. Paravacc, F. Paussa, W. Rhoded , F. Temmed , J. Thaeled , S. Toscanob, P. Voglera, R. Walterb, and A. Wilbertc aETH Zurich, Institute for Particle Physics Otto-Stern-Weg 5, 8093 Zurich, Switzerland bUniversity of Geneva, ISDC Data Center for Astrophysics Chemin d’Ecogia 16, 1290 Versoix, Switzerland cUniversitat Wurzburg, Institute for Theoretical Physics and Astrophysics Emil-Fischer-Str. 31, 97074 Wurzburg, Germany dTU Dortmund, Experimental Physics 5 Otto-Hahn-Str. 4, 44221 Dortmund, Germany 1also at RWTH Aachen E-mail: biland@phys.ethz.ch

FACT — LONGTERM MONITORING OF BRIGHT TeV BLAZARS

Since October 2011, the First G-APD Cherenkov Telescope (FACT) is operated successfully on the Canary Island of La Palma. Apart from the proof of principle for the use of G-APDs in Cherenkov telescopes, the major goal of the project is the dedicated long-term monitoring of a small sample of bright TeV blazars. The unique properties of G-APDs permit stable observations also during strong moon light. Thus a superior sampling density is provided on time scales at which the blazar variability amplitudes are expected to be largest, as exemplified by the spectacular variations of Mrk 501 observed in June 2012. While still in commissioning, FACT monitored bright blazars like Mrk 421 and Mrk 501 during the past 1.5 years so far. Preliminary results including the Mrk 501 flare from June 2012 will be presented.

FACT - TeV Flare Alerts Triggering Multi-Wavelength Observations

D. Dorner∗a, M. L. Ahnenb, M. Balbod , M. Bergmanna, A. Bilandb, T. Bretzb1, K. A. Bruggec, J. Bussc, S. Eineckec, J. Freiwaldc, C. Hempflinga, D. Hildebrandb, G. Hughesb, W. Lustermannb, K. Mannheima, K. Meiera, S. Mullerb, D. Neiseb, A. Neronovd , M. Nothec, A.-K. Overkempingc, A. Paravaca, F. Paussb, W. Rhodec, F. Temmec, J. Thaelec, S. Toscanod , P. Voglerb, R. Walterd , and A. Wilberta aUniversitat Wurzburg, Institute for Theoretical Physics and Astrophysics Emil-Fischer-Str. 31, 97074 Wurzburg, Germany bETH Zurich, Institute for Particle Physics Otto-Stern-Weg 5, 8093 Zurich, Switzerland cTU Dortmund, Experimental Physics 5 Otto-Hahn-Str. 4, 44221 Dortmund, Germany dUniversity of Geneva, ISDC Data Center for Astrophysics Chemin d’Ecogia 16, 1290 Versoix, Switzerland 1also at RWTH Aachen E-mail: dorner@astro.uni-wuerzburg.de

FACT - operation of the First G-APD Cherenkov Telescope

Since more than two years, the First G-APD Cherenkov Telescope (FACT) is operating successfully at the Canary Island of La Palma. Apart from its purpose to serve as a monitoring facility for the brightest TeV blazars, it was built as a major step to establish solid state photon counters as detectors in Cherenkov astronomy. The camera of the First G-APD Cherenkov Telesope comprises 1440 Geiger-mode avalanche photo diodes (G-APD aka. MPPC or SiPM) for photon detection. Since properties as the gain of G-APDs depend on temperature and the applied voltage, a realtime feedback system has been developed and implemented. To correct for the change introduced by temperature, several sensors have been placed close to the photon detectors. Their read out is used to calculate a corresponding voltage offset. In addition to temperature changes, changing current introduces a voltage drop in the supporting resistor network. To correct changes in the voltage drop introduced by varying photon flux from the night-sky background, the current is measured and the voltage drop calculated. To check the stability of the G-APD properties, dark count spectra with high statistics have been taken under different environmental conditions and been evaluated.

First study of combined blazar light curves with FACT and HAWC

For studying variable sources like blazars, it is crucial to achieve unbiased monitoring, either with dedicated telescopes in pointing mode or survey instruments. At TeV energies, the High Altitude Water Cherenkov (HAWC) observatory monitors approximately two thirds of the sky every day. It uses the water Cherenkov technique, which provides an excellent duty cycle independent of weather and season. The First G-APD Cherenkov Telescope (FACT) monitors a small sample of sources with better sensitivity, using the imaging air Cherenkov technique. Thanks to its camera with silicon-based photosensors, FACT features an excellent detector performance and stability and extends its observations to times with strong moonlight, increasing the duty cycle compared to other imaging air Cherenkov telescopes. As FACT and HAWC have overlapping energy ranges, a joint study can exploit the longer daily coverage given that the observatories’ locations are offset by 5.3 hours. Furthermore, the better sensitivity of FACT adds a ...

FACT - Novel mirror alignment using Bokeh and enhancement of the VERITAS SCCAN alignment method

S. Muller∗a, M. L. Ahnena, M. Balbob, M. Bergmannc, A. Bilanda, T. Bretza,1, K. A. Brugged , J. Bussd , D. Dornerc, S. Einecked , J. Freiwaldd , C. Hempflingc, D. Hildebranda, G. Hughesa, W. Lustermanna, K. Mannheimc, K. Meierc, D. Neisea, A. Neronovb, M. Nothed , A.-K. Overkempingd , A. Paravacc, F. Paussa, W. Rhoded , F. Temmed , J. Thaeled , S. Toscanob, P. Voglera, R. Walterb, and A. Wilbertc aETH Zurich, Institute for Particle Physics Otto-Stern-Weg 5, 8093 Zurich, Switzerland bUniversity of Geneva, ISDC Data Center for Astrophysics Chemin d’Ecogia 16, 1290 Versoix, Switzerland cUniversitat Wurzburg, Institute for Theoretical Physics and Astrophysics Emil-Fischer-Str. 31, 97074 Wurzburg, Germany dTU Dortmund, Experimental Physics 5 Otto-Hahn-Str. 4, 44221 Dortmund, Germany 1also at RWTH Aachen E-mail: sebmuell@phys.ethz.ch