Unique particle beams and energies at CERN applied to radiation testing of electronics

The radiation environment in space poses unique challenges to the successful operation of electronic components exposed to it. Hence, it is important to test the devices sufficiently before integrating them in space missions. Even better to do so already during their design phase. Likewise, radiation effects on electronics also represent reliability and availability threats for high-energy accelerator applications. The work performed in the frame of this thesis focuses on the investigation of beams mimicking space and accelerator environments. Radiation such as Ultra-High Energy (UHE) heavy ions and Very High Energy (VHE) electrons play an important role in this context. Since UHE heavy ions are mostly present in the Galactic Cosmic Radiation (GCR) environment and electrons are mostly trapped around planets such as the Earth and Jupiter, their interaction with matter and the resulting radiation effects are of special interest. Aspects such as nuclear fragmentation and energy deposition mechanisms are relevant when estimating the possible impact on electronic components of radiation present in space or on the ground. Hence, tests have been performed to study this response to the radiation exposure particle types in dedicated test facilities. During such experiments, the dosimetry and beam parameters must be in full control. UHE heavy ion test campaigns and experiments with VHE electrons at CERN have served as an excellent opportunity to investigate the interaction with matter of various particle species and energies similar to the GCR and electron-rich environments in space, such as around Jupiter. Due to their high penetration depth, one of the advantages of UHE heavy ion beams at CERN is to test without decapsulation. Moreover, these beams offer the opportunity to work with particles of identical Linear Energy Transfer (LET) and energies to the ones in space. That is interesting, because on the contrary it is a well-established standard to perform radiation tests for space applications with low energy heavy ions. With regards to high-energy electrons, the implications of an exponential increase in Single Event Effects (SEEs) connected to testing at a high instantaneous electron flux [1] and the resulting nuclear electron processes [2] need to be considered. These observations deserve to be characterised and understood, even if they might represent an experimental artefact. For these reasons, the central research questions in this work are: - Is testing with particles of the same LET, but different energy compared to the space environment representative enough? - How can electron beams at CERN be used to test electronics for future space missions, which will be exposed to electron-rich environments? Are there non-linear effects related to high instantaneous intensities of electron fluxes by changing the charge density per pulse? This work has contributed to the understanding of physical phenomena occurring in electronics caused by radiation present in space and in accelerators environments, such as fusion and nuclear fragmentation processes and energy deposition in different materials and volumes. Ground level experimental work in related particle beams, as well as Monte Carlo simulations tools like FLUKA have served for the investigations presented in this PhD thesis

Error rate estimation of DDR4-SDRAM buffers in space mass memories

DDR4-SDRAMs are key components widely used in modern computing systems on ground and in future space applications, where the sensitivity to ionizing radiation effects and the corresponding data integrity performance is of special interest. In this paper, an example DDR4-SDRAM buffer memory partition inside a high-performance mass memory system is described. For this buffer, two different EDAC implementations, which are Reed-Solomon single-symbol-error-correction and Reed-Solomon double-symbol-error-correction are compared in terms of data integrity performance. This comparison is based on the word error probabilities taking into account DDR4-SDRAM component specific single event effects and possible mitigation such as scrubbing and power cycling. The approach described in this work quantifies the design decision for a certain EDAC architecture as well as highlighting the impact of design parameters such as scrubbing and power cycling periods.PeerReviewe

Determination of EPID convolution kernels for portal imaging using carbon target bremsstrahlung

Improving the accuracy and reproducibility during patient positioning is of paramount importance. Hence, the goal of this work is to characterize the aspects of image blurring occurring during carbon target bremsstrahlung portal imaging and to assess the applicability of a deconvolution algorithm. Blurring effects involved in this method of portal imaging are electron scattering inside the EPID, geometric blurring due to the photon source size and photon scattering inside the patient. These effects can all be described by convolutions using as the convolutional kernel a Lorentz function, whose FWHM is 2λ. The λ values measured for these effects range from 0.2 mm to 0.45 mm, and an iterative 2D-deconvolution of carbon target portal images was performed accordingly. A significant decrease in the image blurring of test objects has been achieved and confirmed by analyzing the RMTF. However for clinical images, the deconvolution method is presently faced with the problem of the associated increase of image noise

Measurements of ultra-high energy lead ions using silicon and diamond detectors

A silicon detector and a diamond detector have been used at the SPS experimental North Area at CERN for diagnostics of beams of ultra-high energy lead ions (150 GeV/nucleon). The detectors are operated in pulse mode using a fast digital electronic chain. The discrimination capability of the two detectors is investigated using deposited energy and pulse shape analysis. It is shown that the detectors have good beam monitoring performances and can discriminate the main lead ion beam component from contamination of light and heavy fragments

Pulsed Electron Beam induced SEU Effects in a SRAM memory

Single Event Effects (SEEs) correlated to pulsed beam effects induced by high energy electrons in a very well-established device, such as the ESA SEU (Singe Event Upset) monitor, are investigated in this paper. Measurements with different electron intensities have been performed at VESPER (The Very energetic Electron facility for Space Planetary Exploration missions in harsh Radiative environments) at the CERN Linear Electron Accelerator for Research (CLEAR) focused on very high dose rates per pulse. The possible contribution of electron nuclear events and flash effects is discussed

Longitudinal Direct Ionization Impact of Heavy Ions on See Testing for Ultrahigh Energies

Ultrahigh-energy (UHE) heavy ions show various advantages at testing single-event effect (SEE) in modern technologies, due to their highly penetrating nature. However, the intercepting material in the beam line contributes to the modification of the beam structure by generation of fragments produced via nuclear interactions. This is especially relevant for UHE heavy ion beams, representative of energies in space, which are not fully investigated through conventional ground-level testing. This article is dedicated to the study of the longitudinal energy deposition mechanisms in silicon by the aforementioned heavy ion beams and their fragments. The presented studies have been carried out using Monte Carlo simulations triggered by experimentally observed phenomena

Heavy Ion Nuclear Reaction Impact on SEE Testing: From Standard to Ultra-high Energies

We perform Monte Carlo (MC) simulations to describe heavy ion (HI) nuclear interactions in a broad energy range (4 MeV/n–150 GeV/n), focusing on the single event effect (SEE) sub-linear energy transfer (LET) impact. Previously retrieved single event latch-up (SEL) experimental data have indicated that standard energy ions (~10 MeV/n) can produce high-LET secondaries through fusion reactions which are expected to strongly influence the SEE cross section in the sub-LET region. Alternatively, interactions of higher energy ions (>100 MeV/n) yield secondaries of a similar LET distribution as from the projectile, for projectile-like fragments, and high-energy proton reactions, for target-like fragments. Hence, the factor of relevance to the sub-LET SEE cross section is correlated to low-energy

VHEE beam dosimetry at CERN Linear Electron Accelerator for Research under ultra-high dose rate conditions

The aim of this work is the dosimetric characterization of a plane parallel ionization chamber under defined beam setups at the CERN Linear Electron Accelerator for Research (CLEAR). A laser driven electron beam with energy of 200 MeV at two different field sizes of approximately 3.5 mm FWHM and approximately 7 mm FWHM were used at different pulse structures. Thereby the dose-per-pulse range varied between approximately 0.2 and 12 Gy per pulse. This range represents approximately conventional dose rate range beam conditions up to ultra-high dose rate (UHDR) beam conditions. The experiment was based on a water phantom which was integrated into the horizontal beamline and radiochromic films and an Advanced Markus ionization chamber was positioned in the water phantom. In addition, the experimental setup were modelled in the Monte Carlo simulation environment FLUKA. In a first step the radiochromic film measurements were used to verify the beamline setup. Depth dose distributions and dose profiles measured by radiochromic film were compared with Monte Carlo simulations to verify the experimental conditions. Second, the radiochromic films were used for reference dosimetry to characterize the ionization chamber. In particular, polarity effects and the ion collection efficiency of the ionization chamber were investigated for both field sizes and the complete dose rate range. As a result of the study, significant polarity effects and recombination loss of the ionization chamber were shown and characterized. However, the work shows that the behavior of the ionization chamber at the laser driven beam line at the CLEAR facility is comparable to classical high dose-per-pulse electron beams. This allows the use of ionization chambers on the CLEAR system and thus enables active dose measurement during the experiment. Compared to passive dose measurement with film, this is an important step forward in the experimental equipment of the facility

Single Event Effect Testing With Ultrahigh Energy Heavy Ion Beams

Single event effect (SEE) testing with ultrahigh energy (UHE) heavy ions, such as the beams provided at CERN, presents advantages related to their long ranges with a constant linear energy transfer value. In the present work, the possibility to test components in parallel is being examined, and results from the CERN 2018 UHE Pb test campaigns are studied. Furthermore, the generation of multibit upsets by the UHE Pb ions is evaluated, and the contribution of possible fragments to the SEE measurements is discussed

FPGA SEE Test with Ultra-High Energy Heavy Ions

The use of System-on-Chip (SoC) solutions in the design of space-borne data handling systems is an important step towards further miniaturization in space. In cubesats and in many aggressive commercial missions, use of Commercial-Off-The-Shelf (COTS) components is becoming the rule, rather than the exception and many of those are complex SoC, multiprocessor system-on-chip (MPSoC), SiP (System in package) or AMS-SoC (Analog/Mixed Signal SoC). Those changes are triggering attempts to modify the way we approach and conduct radiation tolerance and testing of electronics. Among the changes that have an impact on Single Event Effect (SEE) testing are scaling of geometries, supply voltages, new materials, new packaging technologies, and overall speed and device complexity challenges. In the frame of the ESA-CERN cooperation agreement, certain ESA projects had access to the most intense beam of ultra-high energy heavy ions available at the Super Proton Synchrotron (SPS) particle accelerator. This paper will present challenges and advantages of SEE tests of complex electronic devices in this new environment and its relevance for future space missions