Patricia Goncalves

Modeling the Response of the ESAPMOS4 RADFETs for the ALPHASAT CTTB Experiment

The Component Technology Test-Bed (CTTB) is one of the main components of the ALPHASAT spacecraft radiation Environment and Effects Facility (AEEF), an European Space Agency (ESA) Technology Demonstration Payload. In-flight data collected by the CTTB experiments will be used to validate ground test protocols, perform prediction models for new component technologies and to provide in-flight evaluation of critical component technologies for use in future missions. The relation between the RADFETs gate threshold voltage shift and the dose can strongly depend on the production processes parameters and needs to be experimentally determined before its use in space. A calibration test campaign of ESAPMOS4 RADFETs was conducted at the ESA/ESTEC Cobalt-60 facility. Irradiation runs were performed at three nominal temperatures: room temperature, 60°C, and 80°C. After the irradiation runs, the units underwent annealing, under similar temperature and bias configuration settings. A model capable of describing the RADFET temperature dependent response during irradiation, at low and high dose rate regimes, is presented in this paper, along with the analysis of the RADFET response during isothermal annealing, following irradiation.

The Ring Imaging Cherenkov detector of the AMS experiment: test beam results with a prototype

The Alpha Magnetic Spectrometer (AMS) to be installed on the International Space Station (ISS) will be equipped with a proximity Ring Imaging Cherenkov (RICH) detector for measuring the velocity and electric charge of the charged cosmic particles. This detector will contribute to the high level of redundancy required for AMS as well as to the rejection of albedo particles. Charge separation up to iron and a velocity resolution of the order of 0.1% for singly charged particles are expected. A RICH protoptype consisting of a detection matrix with 96 photomultiplier units, a segment of a conical mirror and samples of the radiator materials was built and its performance was evaluated. Results from the last test beam performed with ion fragments resulting from the collision of a 158 GeV/c/nucleon primary beam of indium ions (CERN SPS) on a lead target are reported. The large amount of collected data allowed to test and characterize different aerogel samples and the sodium fluoride radiator. In addition, the reflectivity of the mirror was evaluated. The data analysis confirms the design goals.

The low energy magnetic spectrometer on Ulysses and ACE response to near relativistic protons

Aims. We show that the Heliosphere Instrument for Spectra Composition and Anisotropy at Low Energies (HISCALE) on board the Ulysses spacecraft and the Electron Proton Alpha Monitor (EPAM) on board the Advance Composition Explorer (ACE) spacecraft can be used to measure properties for ion populations with kinetic energies in excess of 1 GeV. This previously unexplored source of information is valuable for understanding the origin of near relativistic ions of solar origin. Methods. We model the instrumental response from the low energy magnetic spectrometers from EPAM and HISCALE using a Monte Carlo approach implemented in the Geant4 toolkit to determine the response of different energy channels to energies up to 5 GeV. We compare model results with EPAM observations for 2012 May 17 ground level solar cosmic ray event, including directional fluxes. Results. For the 2012 May event, all the ion channels in EPAM show an onset more than one hour before ions with the highest nominal energy range (1.8 to 4.8 MeV) were expected to arrive. We show from Monte Carlo simulations that the timing at different channels, the ratio between counts at the different channels, and the directional fluxes within a given channel, are consistent with and can be explained by the arrival of particles with energies from 35 MeV to more than 1 GeV. Onset times for the EPAM penetrating protons are consistent with the rise seen in neutron monitor data, implying that EPAM and ground neutron monitors are seeing overlapping energy ranges and that both are consistent with GeV ions being released from the Sun at 10:38 UT.

ISOTOPE SEPARATION WITH THE RICH DETECTOR OF THE AMS EXPERIMENT

The Alpha Magnetic Spectrometer (AMS), to be installed on the International Space Station (ISS) in 2008, is a cosmic ray detector with several subsystems, one of which is a proximity focusing Ring Imaging Cherenkov (RICH) detector. This detector will be equipped with a dual radiator (aerogel+NaF), a lateral conical mirror and a detection plane made of 680 photomultipliers and light guides, enabling precise measurements of particle electric charge and velocity. Combining velocity measurements with data on particle rigidity from the AMS Tracker it is possible to obtain a measurement for particle mass, allowing the separation of isotopes. A Monte Carlo simulation of the RICH detector, based on realistic properties measured at ion beam tests, was performed to evaluate isotope separation capabilities. Results for three elements -- H (Z=1), He (Z=2) and Be (Z=4) -- are presented.

Applications of GEANT4 in astroparticle experiments

The GEANT4 Monte Carlo radiation transport toolkit, developed by the RD44 and GEANT4 Collaborations, aims to become a tool of generalized application in high energy physics, nuclear physics, astrophysics, and medical physics research. Due to its object-oriented design, GEANT4 is a distinct new approach for the development of flexible simulation applications. A wide energy range coverage for both electromagnetic and hadronic physics processes is offered. GEANT4 provides also an optical physics process category, allowing the production and propagation of scintillation and Cherenkov emitted light to be described. Such capabilities are well tailored for the requirements of the new generation of astrophysics experiments to be installed on the International Space Station, like EUSO and AMS. In this paper, the system architecture of a GEANT4 based simulation framework and its application to EUSO/ULTRA and AMS/RICH performance studies are presented.

SEP Protons in GEO with the ESA MultiFunctional Spectrometer

The AEEF-TDP8 (ESA Alphasat Environment and Effects Facili ty Technology Demonstration Payload 8) integrates the radiation monitor Multi-Functio nal Spectrometer (MFS) and the CTTB (Component Technology Test Bed). The two units are installe d on the X panel of the Alphasat satellite as a hosted payload. MFS is an instrument specifica lly designed to characterise the Space Radiation environment while CTTB was built to monitor the effect of radiation on electrical components (GaN transistors, Memories and Optical T r nsceivers) in geostationary orbit. The mission lifetime of AEEF/TDP8 is 3 years with possible ex tension to 5 years and TDP8 is expected to be acquiring scientific data during the whole per iod. On ground, correlation between radiation environment and radiation effects can be establi hed. Before launch, MFS was submitted to proton and electron beam tests at Paul Scherrer Instit ute in Switzerland in 2010. The main purpose was the validation and calibration of the MFS protoflight model together with the estimation of particle energy resolution and identification cap ability. A full Geant4 simulation with the MFS in-flight configuration was built and used to validate th results from ground tests. The full detector simulation has proved to be a valuable tool for the unfolding of MFS channel counts into particle spectra based on a Single Value Decomposition (SVD) method. Results for Proton spectra measured with the MFS in GEO will be presented, in par ticular for the case of Solar Energetic Particle (SEP) events registered in 2014 during per iods of maximum solar activity of solar cycle 24.

Simulation of Single Event Effects and Rate Prediction: CODES an ESA Tool

CODES is an ESA GEANT4 based top level engineering tool, to predict Single Event Effects in EEE devices. It consists of different GEANT4 modules with a user friendly web-based interface. The different modules comprise device geometry definition (including packaging and shielding), device sensitivity interpretation based on experimental test data and data analysis. CODES performance and inter-modular communication is assured by a pre-processor. CODES web interface is deployed in a PHP server. CODES perform full simulation of device sensitivity and final rate prediction. CODES validation results have revealed its excellent performance as an engineering tool.

Representativeness of 60 Co testing for EEE components to be flown in JUICE

The major contribution to the Total Ionizing Dose (TID) damage to EEE components to be flown in the ESA JUICE mission to the Jovian system comes from the electron radiation belts of Jupiter and of its moons. However, standard testing of TID degradation of EEE components is performed with 60Co gammas. In this work the representativity of 60Co testing for the Jovian electron environment was tested by comparing TID degradation of selected EEE components when irradiated with 60Co gammas and with electron beams with energy above 10 MeV. In order to perform this verification, typical components used in space systems were irradiated at different facilities, under different conditions with High Dose Rate (HDR) and Low Dose Rate (LDR) 60Co gammas and with 12 MeV and 20 MeV electrons beams up to 100 krad (water). Key parameters of each component were measured before, during (every 20 krad) and after irradiation. The results obtained show no significant sensitivity to radiation type in all components tested. Furthermore, results achieved (the annealing measurement phase is still ongoing) confirm that 60Co testing is representative of the expected response to TID of the five tested component types to be flown in JUICE.

SEP Protons in GEO Measured With the ESA MultiFunctional Spectrometer

The MFS (Multi-Functional Spectrometer) is a radiation monitor that together with CTTB (Component Technology Test Bed) make the AEEF-TDP8 (ESA Alphasat Environment and Effects Facility — Technology Demonstration Payload 8). The two units are hosted in the X panel of the Alphasat satellite in orbit since July 2013. MFS is an instrument specifically designed to characterise the Space Radiation environment while CTTB was built to monitor the effect of radiation on electrical components (GaN transistors, Memories and Optical Transceivers) in geostationary orbit. The mission lifetime of AEEF/TDP8 will be at least of three years and TDP8 is expected to be acquiring scientific data during the whole period. On ground, correlation between radiation environment and radiation effects can be established. Before launch, MFS was submitted to proton and electron beam tests at Paul Scherrer Institute in Switzerland in 2010. The main purpose was the validation and calibration of the MFS proto-flight model together with the estimation of particle energy resolution and identification capability. A full Geant4 simulation with CAD (Computer-aided design) geometry exported to GDML (Geometry Description Markup Language) description the MFS in-flight configuration was built. Ground tests results were validated with Geant4 simulation. The measurements of MFS proton channels and MFS proton response functions are evaluated using comparisons with INTEGRAL/IREM data during the Solar Proton Event (SPE) of January 2014. In addition, an Artificial Neural Network (ANN) unfolding method was developed in order to unfold MFS data. Comparisons show that the derived ANN Alphasat/MFS fluxes are in remarkable agreement with INTEGRAL/IREM proton fluxes.

Solar panels as cosmic-ray detectors

Due to fundamental limitations of accelerators, only cosmic rays can give access to centre-of- mass energies more than one order of magnitude above those reached at the LHC. In fact, extreme energy cosmic rays (1018 eV - 1020 eV) are the only possibility to explore the 100 TeV energy scale in the years to come. This leap by one order of magnitude gives a unique way to open new horizons: new families of particles, new physics scales, in-depth investigations of the Lorentz symmetries. However, the flux of cosmic rays decreases rapidly, being less than one particle per square kilometer per year above 1019 eV: one needs to sample large surfaces. A way to develop large-effective area, low cost, detectors, is to build a solar panel-based device which can be used in parallel for power generation and Cherenkov light detection. Using solar panels for Cherenkov light detection would combine power generation and a non-standard detection device.