Radiation Risks and Mitigation in Electronic Systems

Electrical and electronic systems can be disturbed by radiation-induced effects. In some cases, radiation-induced effects are of a low probability and can be ignored; however, radiation effects must be considered when designing systems that have a high mean time to failure requirement, an impact on protection, and/or higher exposure to radiation. High-energy physics power systems suffer from a combination of these effects: a high mean time to failure is required, failure can impact on protection, and the proximity of systems to accelerators increases the likelihood of radiation-induced events. This paper presents the principal radiation-induced effects, and radiation environments typical to high-energy physics. It outlines a procedure for designing and validating radiation-tolerant systems using commercial off-the-shelf components. The paper ends with a worked example of radiation-tolerant power converter controls that are being developed for the Large Hadron Collider and High Luminosity-Large Hadron Collider at CERN.Comment: 19 pages, contribution to the 2014 CAS - CERN Accelerator School: Power Converters, Baden, Switzerland, 7-14 May 201

What are the evolutionary constraints on larval growth in a trophically transmitted parasite?

For organisms with a complex life cycle, a large larval size is generally beneficial, but it may come at the expense of prolonged development. Individuals that grow fast may avoid this tradeoff and switch habitats at both a larger size and younger age. A fast growth rate itself can be costly, however, as it requires greater resource intake. For parasites, fast larval growth is assumed to increase the likelihood of host death before transmission to the next host occurs. Using the tapeworm Schistocephalus solidus in its copepod first intermediate host, I investigated potential constraints in the parasite’s larval life history. Fast-growing parasites developed infectivity earlier, indicating there is no functional tradeoff between size and developmental time. There was significant growth variation among full-sib worm families, but fast-growing sibships were not characterized by lower host survival or more predation-risky host behavior. Parental investment also had little effect on larval growth rates. The commonly assumed constraints on larval growth and development were not observed in this system, so it remains unclear what prevents worms from exploiting their intermediate hosts more aggressively

Parasite Population Regulation: Lethal and Sublethal Effects of \u3ci\u3eLeptorhynchoides thecatus\u3c/i\u3e (Acanthocephala: Rhadinorhynchidae) on \u3ci\u3eHyalella azteca\u3c/i\u3e (Amphipoda)

The hypothesis that Leptorhynchoides thecatus populations are regulated by mortality of heavily infected intermediate hosts, Hyalella azteca, was examined experimentally. Mortality related to the infection process could not be demonstrated because no survivorship difference occurred between amphipod groups exposed to L. thecatus and unexposed control groups after 24 hours Likewise, amphipod mortality could not be associated with infection intensity during this period. Amphipod mortality, growth, and infection intensity were monitored for 25 days after a 24-hour exposure period. Cystacanths were infective to fish after 25 days. Survivorship of exposed amphipods was at least as great as that of unexposed controls. Infection intensity in exposed male survivors did not differ significantly from that in males that died during the study. Infection intensities in females and survivors of undetermined sex were significantly higher than in Hyallela that died. The effect of time on amphipod size (as indicated by head length) was significant for male survivors and all females, but not for males that died. No negative effect of infection intensity on growth was demonstrated, nor was there significant correlation between amphipod size and infection intensity for either sex of amphipod at any time during the 25-day experiment. No evidence of lethal effects or sublethal effects on growth was detected

Development of radiation tolerant components for the Quench Protection System at CERN

This paper describes the results of irradiation campaigns with the high resolution Analog to Digital Converter (ADC) ADS1281. This ADC will be used as part of a revised quench detection circuit for the 600 A corrector magnets at the CERN Large Hadron Collider (LHC) . To verify the radiation tolerance of the ADC an irradiation campaign using a proton beam, applying doses up to 3,4 kGy was conducted. The resulting data and an analysis of the found failure modes is discussed in this paper. Several mitigation measures are described that allow to reduce the error rate to levels acceptable for operation as part of the LHC QPS

Radiation tolerant power converter controls

The Large Hadron Collider (LHC) at the European Organisation for Nuclear Research (CERN) is the world's most powerful particle collider. The LHC has several thousand magnets, both warm and super-conducting, which are supplied with current by power converters. Each converter is controlled by a purpose-built electronic module called a Function Generator Controller (FGC). The FGC allows remote control of the power converter and forms the central part of a closed-loop control system where the power converter voltage is set, based on the converter output current and magnet-circuit characteristics. Some power converters and FGCs are located in areas which are exposed to beam-induced radiation. There are numerous radiation induced effects, some of which lead to a loss of control of the power converter, having a direct impact upon the accelerator's availability. Following the first long shut down (LS1), the LHC will be able to run with higher intensity beams and higher beam energy. This is expected to lead to significantly increased radiation induced effects in materials close to the accelerator, including the FGC. Recent radiation tests indicate that the current FGC would not be sufficiently reliable. A so-called FGClite is being designed to work reliably in the radiation environment in the post-LS1 era. This paper outlines the concepts of power converter controls for machines such as the LHC, introduces the risks related to radiation and a radiation tolerant project flow. The FGClite is then described, with its key concepts and challenges: aiming for high reliability in a radiation field

Backbone-modified oligonucleotides containing a butanediol-1,3 moiety as a 'vicarious segment' for the deoxyribosyl moiety--synthesis and enzyme studies.

Sequential single replacement of nucleosides within the decanucleotide d[GGGAATTCCC] (7) by means of a butanediol-1,3 residue allowed us to obtain a set of ten decanucleotides containing 'vicarious' (V) carbon-phosphate fragments. These analogues were further used as substrates for svPDE, nuclease PI and EcoR1 endonuclease. Interestingly, replacement of any of the nucleosides within the canonical sequence ...GAATTC... by the butanediol-1,3 'vicarious' segment discriminates such constructs 8c-h as substrates for Eco-R1 enzyme