Commissioning of the third n_TOF spallation target: characterization of the neutron flux and beam profile using PPACs

Beyond their application in fundamental nuclear physics and nuclear astrophysics research, neutron-induced reactions play an increasingly important role in emerging nuclear technologies. For instance, in the fields of sustainable low-carbon power production (ADS, generation four fission and fusion reactors), medicine and industry, neutron data are required with high accuracy in a wide energy range. The measurement of neutron-induced reaction cross sections is therefore crucial and it is indeed the main objective of the n_TOF facility, a pulsed white neutron spallation source at CERN. Recently the facility has been upgraded with the installation of its new third-generation spallation target and a subsequent commissioning was carried out in order to characterize the performances of the experimental areas in terms of neutron flux, energy resolution and background in view of the future experimental campaigns. I was involved in the first phase of the commissioning at CERN, testing the DAQ system and taking care in particular of one of the employed detectors: a fission chamber based on Parallel Plate Avalanche Counters (PPACs). The data collected in the first experimental area (EAR1) were analyzed to obtain the neutron flux from near thermal energy (0.025 eV) to 1 GeV and the spatial beam profile. The flux from the present analysis is compared to the Monte Carlo simulations and to the preliminary results of another flux detector, while the spatial beam profile is compared to the one obtained with a Timepix Quad detector. In addition, a preliminary analysis of the data collected in the second experimental area (EAR2) was also carried out

Studio di un rivelatore per la misura del flusso di neutroni ad alta energia a n_TOF

La ricerca in fisica nucleare fondamentale e le tecnologie nucleari emergenti quali rettori di quarta generazione ed ADS (Accelerator Drive System) necessitano urgentemente, per progredire e raffinarsi, di dati precisi delle sezioni d'urto di fissione indotte da neutroni ad energie al di sopra di 200 MeV che ad oggi non sono disponibili. La loro misura è lo scopo di un esperimento in corso alla facility n_TOF del CERN di Ginevra, dove è disponibile un fascio di neutroni fino ad 1 GeV e tramite il quale si intende misurare la sezione d'urto di fissione indotta da neutroni su 235U, ad oggi uno standard soltanto fino a 200 MeV. Un passo fondamentale dell'esperimento è rappresentato dalla misura del flusso di neutroni del fascio, dato importante nella misura della sezione d'urto, e questa tesi si inserisce proprio in questo ambito studiando il PRT (Proton Recoil Telescope), il rivelatore costruito dall'INFN che permette di caratterizzare il flusso di neutroni incidente misurando i protoni provenienti dallo scattering n-p del fascio su un bersaglio di polietilene. Nello studio delle prestazioni del telescopio, effettuato sulla base di simulazioni Montecarlo considerando bersagli di polietilene e di carbonio di diverso spessore, emerge come punto di forza del rivelatore la segmentazione, caratteristica che permette di guadagnare in precisione eliminando molto background, inteso sia come particelle diverse da protoni, sia come protoni derivanti da reazioni diverse dallo scattering n-p. Infine viene ricavata l'efficienza del rivelatore

Preparing Phase 4 of the n_TOF/CERN facility

After CERN's Long Shutdown 2, the n_TOF facility infrastructure was largely upgraded. The biggest change is the installation of a new lead spallation target, the performance of which needs to be carefully examined. During Summer 2021, the facility's two flight paths were characterised in terms of neutron beam energy distribution, profile and resolution. In this work, the characterisation of the facility is described and the first results are given

Multicenter randomized trial comparing compression with elastic stocking versus bandage after surgery for varicose veins

Objectives: Postoperative limb compression is widely used after venous surgery to prevent thromboembolism and to reduce hemorrhage, edema, hematoma, and pain. Only limited studies have been published regarding the most adequate postoperative compression therapy after varicose vein surgery. This study evaluated the effectiveness of a new stocking kit used for postoperative limb compression. Methods: The study compared the clinical practicability, ease to use, effectiveness, and safety of a postoperative stocking system (23 to 32 mmHg at the ankle) with compression bandages (control group). This prospective, randomized, open-label clinical trial, was performed in three Italian centers specializing in venous surgery. Sixty consecutive patients (classification CEAP C2,S) underwent unilateral varicose vein surgery at one of the three centers. After surgery, patients were randomized for postoperative compression therapy with a new stocking system (Sigvaris Postoperative Kit; Ganzoni Sigvaris Corp, Winterthur, Switzerland) or standard stretch bandages (30 patients per group). Primary end points were incidence of venous thromboembolism, hemorrhage, limb hematoma, or edema