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

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

Transmission of Grapevine virus A and Grapevine leafroll-associated virus 3 by Heliococcus bohemicus

Heliococcus bohemicus Sulc is very frequently found in vineyards in Northern Italy, where grapevine leafroll is widespread. Grapevine leafroll-associated virus 1 (GLRaV-1) and Grapevine leafroll-associated virus 3 (GLRaV-3) are also quite frequently observed, often in association with Grapevine virus A (GVA). The capacity of the mealybug to transmit these viruses to vine was therefore evaluated. Virus-free insects were fed on infected vines and then transferred to healthy test-plants. GLRaV-3 was transmitted to two out of 77 inoculated test-plants and GVA to one out of 38; GLRaV-1 was not transmitted. This is the first report of GVA transmission by H. bohemicus and the first report of the capacity of this mealybug to transmit GLRaV-3 to grapevine in Italy