L. del Peral

A new composition-sensitive parameter for ultra-high energy cosmic rays

Abstract A new family of parameters intended for composition studies in cosmic ray surface array detectors is proposed. The application of this technique to different array layout designs has been analyzed. The parameters make exclusive use of surface data combining the information from the total signal at each triggered detector and the array geometry. They are sensitive to the combined effects of the different muon and electromagnetic components on the lateral distribution function of proton and iron initiated showers at any given primary energy. Analytical and numerical studies have been performed in order to assess the reliability, stability and optimization of these parameters. Experimental uncertainties, the underestimation of the muon component in the shower simulation codes, intrinsic fluctuations and reconstruction errors are considered and discussed in a quantitative way. The potential discrimination power of these parameters, under realistic experimental conditions, is compared on a simplified, albeit quantitative way, with that expected from other surface and fluorescence estimators.

The Atmospheric Monitoring System of the JEM-EUSO space mission

An Atmospheric Monitoring System (AMS) is a mandatory and key device of a space-based mission which aims to detect Ultra-High Energy Cosmic Rays (UHECR) and Extremely-High Energy Cosmic Rays (EHECR) from Space. JEM-EUSO has a dedicated atmospheric monitoring system that plays a fundamental role in our understanding of the atmospheric conditions in the Field of View (FoV) of the telescope. Our AMS consists of a very challenging space infrared camera and a LIDAR device, that are being fully designed with space qualification to fulfil the scientific requirements of this space mission. The AMS will provide information of the cloud cover in the FoV of JEM-EUSO, as well as measurements of the cloud top altitudes with an accuracy of 500 m and the optical depth profile of the atmosphere transmittance in the direction of each air shower with an accuracy of 0.15 degree and a resolution of 500 m. This will ensure that the energy of the primary UHECR and the depth of maximum development of the EAS ( Extensive Air Shower) are measured with an accuracy better than 30% primary energy and 120 g=cm 2 depth of maximum development for EAS occurring either in clear sky or with the EAS depth of maximum development above optically thick cloud layers. Moreover a very novel radiometric retrieval technique considering the LIDAR shots as calibration points, that seems to be the most promising retrieval algorithm is under development to infer the Cloud Top Height (CTH) of all kind of clouds, thick and thin clouds in the FoV of the JEM-EUSO space telescope.

Jovian electrons in the heliosphere: new insights from EPHIN on board SOHO

Abstract The electron spectrum in the energy range 150 keV to 10 MeV, measured by EPHIN sensor on board SOHO observatory during 1996 quiet time periods, is presented. The results show that the dominant electron population is of jovian origin. The spectral indexes obtained range from 1.5 to 1.8. In this work an estimation of the emission intensity of electrons from the jovian magnetosphere is also obtained. Unexpected recurrence of jovian electrons at the middle of 1996 during poor Earth–Jupiter magnetic connection has been observed.

Observation of ultra-high energy cosmic rays in cloudy conditions by the space-based JEM-EUSO Observatory

JEM-EUSO is a space observatory that will be located on-board the Japanese Experiment Module at the International Space Station. It will observe Extensive Air Showers (EAS) induced by ultra-high energy cosmic rays using the Earths atmosphere as detector. In addition to clear sky observations, EAS are also observable in cloudy conditions if a sufficiently large part of the EAS development occurs above the cloud. The atmospheric monitoring system plays a fundamental role in our understanding of the atmospheric conditions in the field of view of the telescope.

Particle charge evolution during acceleration processes in solar flares

It has been customary to assume that the charge state of energetic particles corresponds to the ionization equilibrium of the ambient plasma within the acceleration region. Nonetheless, we ascribe to a different opinion, by suggesting that charge interchange mechanisms may be activated during the ensuing acceleration process. We substantiate our claim by the calculated behaviour of charge states corresponding to energized ions while they are accelerated in the source regions. These computations are based on the electron capture and loss cross sections. Results from the analysis allow us to conclude that, contrary to the general assumption, charge exchange processes may be invoked during the acceleration of energized ions in solar flares.

An electronic device that suits space research requirements for ion detection

An electronics system for low-energy cosmic ion detection has been designed and built. This instrument was designed to he shipped onboard a satellite with a mission to detect solar energetic particles (SEP) and to study the anomalous component of cosmic rays. The electronics of the instrument were verified by four functional tests. In the first of these tests, its response to well-known electronic pulses, analogous to those produced in the detectors, was checked. During the second test, the coincidence-anticoincidence performances have been verified. The third test consisted of the calibration of each detector and its corresponding electronics chain with alpha particles from a /sup 241/Am source. All these preliminary tests were carried out in an Alcala University laboratory. The final test was done with nuclear reaction fragments at the VICKSI (Van de Graaff Isochron Cyctotron Kombination fur Schwere Ionen) heavy ion accelerator facility of the Hahn Meitner Institute in Berlin. The trails proved to be successful, with satisfactory results when compared with those achieved by standard nuclear instrumentation.

Radiation Hardness Assurance for the JEM-EUSO Space Mission

Reliability assessment is concerned with the analysis of devices and systems whose individual components are prone to fail. This reliability analysis documents the process and results of reliability determination of the JEM-EUSO Photomultiplier tube component using the methods 217 Plus, Quantum efficiency degradation and radiation hardness assurance. In conclusion, the levels of damage suffered by the PMTs which comprise the focal surface of JEMEUSO Space Telescope, are acceptable. The results show as well that the greatest contribution to the failure is due to radiation SET. The guaranteed performance of this equipment is a 99.45%, an accepted value of reliability thus fulfilling the objectives and technological challenges of JEM-EUSO. It should be noted that the reliability values of the Standard 217Plus, despite being a standard improved, and an updated version of MIL-HDBK-217 Plus does not have sections that include the analysis of radiation of space electronic equipment. The recommendation from this study is the inclusion of all real failure effects may face an electronic, mechanical, optical space equipment.This analysis documents the process and results of reliability determination of the PhotoMultiplier Tube (PMT) components of the JEM-EUSO telescope under the different radiation sources, UV radiation, Total Ionizing Doses (TIDs), and Single Event Transients. In terms of UV Ionization, the transmittance of the glass of the PMTs during the 5-year duration of the mission is greater than 99.98%, thereby ensuring the desired 20% value for quantum efficiency. Of the 4932 PMTs covering the focal surface of the telescope, we estimate that of order 7 may fail due to TID and about 16 may fail due to SET. Therefore, it can be concluded that around 99% of the PMTs will complete their operation without failure, ensuring the success of the mission as far as TIDs and SETs radiation is concerned. PMTs suffer basically due to high brightness effects, reducing the transmittance of the crystal window. However, the result of this study, taking into account the values produced by the model based on the TID, as well as the darkening of the glass, show similar values in terms of degradation. Therefore, as a preliminary result, it is possible to conclude that the TID model proposed here for PMTs can be “validated”.

Detector system for low-energy cosmic ions study

Abstract A low-energy cosmic ion detector system composed of a telescope and its amplification electronics has been designed and constructed. The detector system is able to detect ions from hydrogen to iron in the energy range of 1–50 MeV/nucleon. The amplification electronics has been designed using space components so that its weight, dimensions and power consumption would be small enough to allow the telescope to be used for cosmic ion detection in space aboard a satellite. The system was calibrated in a heavy ion accelerator, and the results show good charge and mass discrimination for the registered ions as well as a good response from the amplification electronics.

Cherenkov light shape of gamma and hadronic VHE air showers: Fit to analytical formulae

Abstract A detailed Monte Carlo simulation of Cherenkov light (300–480 nm) from electromagnetic and hadronic cascades in the atmosphere has been performed in the energy range 10 12 –10 14 eV of γ, proton, oxygen, and iron primary cosmic rays for vertically incident showers. In the calculations of both cascade development and Cherenkov light production, the CORSIKA (COsmic Ray SImulator for KAscade) code [J.N. Capdevielle et al., Kerforschungszentrum Karlsruhe GmbH, Repr. KfK 4998 (1992)] has been used to allow for all, electromagnetic and hadronic, interactions. The main aim of our simulation is to obtain possibly accurate information on the lateral spread, longitudinal development, and temporal profile of Cherenkov light, from both pure electromagnetic and hadronic cascades, in order to obtain information to separate both. Time profile Cherenkov light pulse and primary cosmic ray dependence have been obtained. Parametrization of Cherenkov light pulses has been performed making use of gamma distributions. Apart from their value as new results, they may be used for the design, of current studies at mountain altitude. We also seek to provide relations to interpret the experimental data, for those who do not have detailed simulation calculations available.

Charge systematic errors associated with identification methods for heavy-ion ΔE–E telescopes

Abstract The contribution of identification methods to charge systematic errors for heavy-ion Δ E – E multidetector telescopes is studied. In this context, a new identification method is presented in two versions: the first uses one Δ E value and second uses all Δ E data for each event. A Monte Carlo simulation of the response of a solid-state telescope to an isotropic flux of heavy ions is used to test the systematic errors induced by this method and by the Seamster and range methods.