Testing the Properties of Beam-Dose Monitors for VHEE-FLASH Radiation Therapy

Very High Energy Electrons (VHEE) of 50 - 250 MeV are an attractive choice for FLASH radiation therapy (RT). Before VHEE-FLASH RT can be considered for clinical use, a reliable dosimetric and beam monitoring system needs to be developed, able to measure the dose delivered to the patient in real-time and cut off the beam in the event of a machine fault to prevent overdosing the patient. Ionisation chambers are the standard monitors in conventional RT; however, their response saturates at the high dose rates required for FLASH. Therefore, a new dosimetry method is needed that can provide reliable measurements of the delivered dose in these conditions. Experiments using 200 MeV electrons were done at the CLEAR facility at CERN to investigate the properties of detectors such as diamond beam loss detectors, GEM foil detectors, and Timepix3 ASIC chips. From the tests, the GEM foil proved to be the most promising

REFLECT – Research flight of EURADOS and CRREAT: Intercomparison of various radiation dosimeters onboard aircraft

Aircraft crew are one of the groups of radiation workers which receive the highest annual exposure to ionizing radiation. Validation of computer codes used routinely for calculation of the exposure due to cosmic radiation and the observation of nonpredictable changes in the level of the exposure due to solar energetic particles, requires continuous measurements onboard aircraft. Appropriate calibration of suitable instruments is crucial, however, for the very complex atmospheric radiation field there is no single reference field covering all particles and energies involved. Further intercomparisons of measurements of different instruments under real flight conditions are therefore indispensable. In November 2017, the REFLECT (REsearch FLight of EURADOS and CRREAT) was carried out. With a payload comprising more than 20 different instruments, REFLECT represents the largest campaign of this type ever performed. The instruments flown included those already proven for routine dosimetry onboard aircraft such as the Liulin Si-diode spectrometer and tissue equivalent proportional counters, as well as newly developed detectors and instruments with the potential to be used for onboard aircraft measurements in the future. This flight enabled acquisition of dosimetric data under well-defined conditions onboard aircraft and comparison of new instruments with those routinely used. As expected, dosimeters routinely used for onboard aircraft dosimetry and for verification of calculated doses such as a tissue equivalent proportional counter or a silicon detector device like Liulin agreed reasonable with each other as well as with model calculations. Conventional neutron rem counters underestimated neutron ambient dose equivalent, while extended-range neutron rem counters provided results comparable to routinely used instruments. Although the responses of some instruments, not primarily intended for the use in a very complex mixed radiation field such as onboard aircraft, were as somehow expected to be different, the verification of their suitability was one of the objectives of the REFLECT. This campaign comprised a single short flight. For further testing of instruments, additional flights as well as comparison at appropriate reference fields are envisaged. The REFLECT provided valuable experience and feedback for validation of calculated aviation doses

patogeni floematici della vite : identificazione, epidemiologia, prevenzione

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patogeni floematici della vite : identificazione, epidemiologia, prevenzione

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Extracts of Calpurnia aurea leaves from southern Ethiopia attract and immobilise or kill ticks

Calpurnia aurea extracts are used in southern Ethiopia to protect stock against ticks. Acetone, hexane and water leaf extracts of C. aurea collected in southern Ethiopia were tested for repellent/attractant and acaricidal properties on unfed adult Rhipicephalus pulchellus ticks. In contrast to many other plant species evaluated, C. aurea extracts did not have repellent properties, but rather had a slight attractant capacity. With 20% and 10% acetone extracts, all ticks were either killed or their mobility severely compromised after 1 μl of extract was topically applied on the abdomen. At a 5% concentration, 85% of ticks were still affected. A 10% aqueous solution also had a marked effect. The results prove the efficacy of the traditional use of this extract and may lead to a product that can be used commercially to protect animals against tick infestation, under subsistence as well as industrialized conditions.National Research Foundation in South Afric

Optical filtering based neutron/γ-ray discrimination in a phoswich detector

Neutron/-ray (∕) discrimination is a crucial issue in neutron measurements and is usually accomplishedemploying detectors transparent to-rays (3He proportional counters), or techniques forrejection (such asPulse Shape Discrimination). The aim of this work is to test a system able to perform a quasi-digital∕discrimination without using techniques based on pulse shape analysis. The system is based on a phoswichconsisting of a LiCAF:Eu crystal sensitive to neutrons and two LuAG:Ce ceramics sensitive to-rays. Opticalfiltering allows obtaining two separate acquisition channels, which selectively collect the light emitted by onlyone of the two scintillators. Photon induced events are then discarded through an anti-coincidence algorithm.The results show that the proposed technique is actually capable of discarding-induced events, but theimplemented setup downgrades the LiCAF:Eu light collection because of the light attenuation of glasses servingas filters. In some situations, it is preferable to employ the LiCAF:Eu crystal alone, discarding the-inducedevents on the basis of the signal amplitude. Therefore, the discrimination technique proposed with this setupis intended for situations in which the energy of the incoming photons or the pile-up effects related to thehigh fluence rate can generate pulses whose amplitude is comparable to a neutron event. In addition, it wasnoted that some optical filters contain impurities (10B in our case) which capture neutrons lowering the systemdetection efficiency.A Monte Carlo model was also implemented to replicate the system response and predict an optimalconfiguration for further development