Simon Bacholle

A Cockcroft-Walton High-Voltage Power Supply for the EUSO Instruments

The future JEM-EUSO instrument is a UV telescope to be installed on the International Space Station (ISS) with the goal of observing Extensive Air Showers created by Ultra-High Energy Cosmic rays. EUSO-balloon is a pathfinder mission for JEM-EUSO which flew in a stratospheric balloon from Timmins, Canada in August 2014. Due to its placement on the ISS, two major specifications of the JEM-EUSO instrument are that: i) the power allocated for the entire instrument should be no more than 1000 W; requiring that the power allocated to polarize the Photomultiplier Tubes (PMTs) should be less than∼50 W (using normal resistive voltage dividers requires nearly 2 kW), and ii) the light intensity reaching JEM-EUSO has a dynamic range larger than 106, going from the background illumination (about one photoelectron per pixel per 2.5 μs) up to Transient Luminous objects. Our solution for i) is to use a Cockcroft-Walton circuit to effectively create a separate power supply for each dynode, regrouping identical dynodes at the same power supply. These groups will be at the level of the Elementary Cell (EC, 4 PMTs). The required dynamic range will be provided by a switching circuit, giving an overall dynamic range of 106 in steps of 102 and in a time of several microseconds. Here we present the Cockcroft-Walton high voltage power supply design used in EUSO-Balloon. This design resulted in a power consumption of 630 mW to polarize the entire EUSO-Balloon focal surface (36 PMTs ), and the switching circuit was capable of reducing the focal surface collection efficiency within 2.5 μs.

Night time measurement of the UV background by EUSO-Balloon

Š. Mackovjak∗1, A. Neronov1, P. Bobík2, M. Putiš2, L. Del Peral1, 3, M. D. Rodríguez Frías1, 3, 8, K. Shinozaki4, C. Catalano5, J. F. Soriano3, G. Sáez-Cano3, C. Moretto6, S. Bacholle7 for the JEM-EUSO Collaboration 1 ISDC Data Centre for Astrophysics, University of Geneva, Switzerland 2 Department of Space Physics, IEP, Slovak Academy of Sciences, Košice, Slovakia 3 SPace & AStroparticle (SPAS) Group, UAH, Madrid, Spain 4 Institute for Astronomy and Astrophysics, University of Tübingen, Germany 5 Institut de Recherche en Astrophysique et Planétologie, CNRS-UPS Toulouse, France 6 Laboratoire de l’Accélérateur Linéaire, Université Paris Sud, France 7 Laboratoire AstroParticule et Cosmologie, Université Paris Diderot, France 8 IFIC, CSIC, Dpto. Física Atómica, Molecular y Nuclear, Universitat de València, Spain

EUSO-Balloon: Observation and Measurement of Tracks from a Laser in a Helicopter

EUSO-Balloon is a prototype detector of the Extreme Universe Space Observatory on the Japanese Experiment Module (JEM-EUSO). EUSO-Balloon was flown successfully as a balloon payload from the Timmins Stratospheric Balloon Launch Facility in Ontario, Canada on 2014 August 24-25 at an altitude of 38 km. To simulate the optical signatures of UV fluorescence photons emitted from cosmic ray air showers generated in the atmosphere, a pulsed UV laser and two UV flashers (LED and Xe) were used. These sources were fired in the instrument field of view for about 2 hours from a helicopter that circled at an altitude of 3 km under the balloon. UV signals were effectively detected, including 270 laser track events. We describe the helicopter laser system and the geometric reconstruction of the laser events that were generated by this system. We report here on the reconstruction of the laser events starting from the information contained in the observed tracks. We note that this work represents the first observation and measurement of aircraft based laser tracks by an optical fluorescence detector flown at near space altitudes.

EUSO-Balloon trigger efficiency in preparation of a long duration flight

EUSO-Balloon is a pathfinder for the JEM-EUSO experiment, devoted to the observation of ultrahigh-energy cosmic rays (UHECRs) from space. It operates on a stratospheric balloon at an altitude of ∼ 38 km. A first flight took place in August 2014, during a single night [1]. Here, we investigate the acceptance of a new version of the instrument in view of a forthcoming long duration flight. We use the ESAF simulation code [2], adapted to the EUSO-Balloon design, to determine the trigger efficiency as a function of energy. We then convolve the results with the cosmic-ray spectrum and derive the number of events expected to be detected in the range between 1017.5 eV and 1019 eV. We conclude that EUSO-Balloon is well-designed to be the first fluorescence telescope to detect cosmic-ray showers from above.

Performance of the EUSO-Balloon electronics

The 24th of August 2014, the EUSO-BALLOON instrument went for a night flight for several hours, 40 km above Timmins (Canada) balloon launching site, concretizing the hard work of an important part of the JEM-EUSO collaboration started 3 years before. This instrument consists of a telescope made of two lenses and a complex electronic chain divided in two mains sub-systems: the PDM (photo detector module) and the DP (data processing). Each of them is made of several innovative elements developed and tested in a short time. This paper presents their performances before, during and after the flight.

The EUSO@Turlab Project: Results from Phase II

The TurLab facility is a laboratory, equipped with a 5 m diameter and 1 m deep rotating tank,located in the Physics Department of the University of Turin. Originally built mainly to study problems where system rotation plays a key role in the fluid behaviour such as in atmospheric and oceanic flows at different scales, in the past few years the TurLab facility has been used to perform experiments related to observation of Extreme Energy Cosmic Rays from space using the fluo-rescence technique, as in the case of the JEM-EUSO mission, where the diffuse night brightness and artificial light sources can vary significantly in time and space inside the Field of View of the telescope. The description of the EUSO@TurLab project and its first results have been presented in the past. During the last two years many upgrades have been performed on the instrumenta-tion mainly related to the read-out electronics: SPACIROC-1 (employed in EUSO-Balloon and EUSO-TA prototypes) and SPACIROC-3 (EUSO-SPB and Mini-EUSO) which allowed to test a fully equipped Elementary Cell of JEM-EUSO. This phase has been named Phase II. Moreover, the Focal Surface of EUSO-Balloon with the level 1 trigger logic implemented in the Photo-Detector Module has been tested at TurLab after the Canada flight. Finally, tests related to the possibility to employ a EUSO-like detector for other type of applications such as wave monitor- ing and imaging detector have been pursued. The tests and results obtained in EUSO@TurLab Project - Phase II are described.