Aim of this thesis, begun in November 2019, is the development of an innovative Cerenkov detector for measurements of 17 MeV gamma-rays emitted by the D-T fusion reaction in an intense neutron field. With the spread of the COVID-19 pandemics in Northern Italy in February 2020, it became clear that the original program planned for my PhD work had to be significantly changed, since experimental activities to be carried out in the UNIMIB/CNR laboratories in Milan and at the Joint European Torus in the UK had to be cancelled. In agreement with my tutors I volunteered together with other scientists to contribute to a project called Mechanical Ventilator Milan (MVM). The MVM project involved an international team of more than 150 scientists and has produced over the very short period of less than three months a mechanical ventilator approved by the American Food and Drug Administration for use at the intensive care unit of hospitals to treat patients affected by COVID-19. The activities of the MVM project led to the development of a new fast oxygen sensor for medical application, about one year later. The sensor measures the oxygen consumption in real time during a single breath. The thesis is organized in three parts. The first part is focused on the development of a gamma-ray counter optimized for the measurement of the D-T fusion power produced in a magnetic confinement fusion device. The research team I have joined is developing a novel technique for the measurement of DT fusion power in a magnetic confinement device based on the detection of 17 MeV gamma-rays also produced by the D+T->5He* reaction. The 5He* nucleus promptly decays usually emitting an alpha particle and a neutron, but it may de-excite to the ground level emitting a gamma-ray with a probability of the order of 10^-5. These gamma-rays have been detected in the recent DT campaign at JET with a gamma spectrometer based on LaBr3 and a fast digital data acquisition. Since the efficiency of the scintillator to high energy gamma-rays and neutrons are comparable, the use of a dedicated LiH based neutron attenuator to observe the weak gamma-ray signal is needed. To overcome the limitations posed by the sensitivity of LaBr3 detectors to neutrons, I designed a gamma-ray gas detector optimized to work in the presence of an intense neutron field. The detector is based on the Cherenkov effect and simulations indicate that it is 10^6 times more sensitive to gamma-rays than to neutrons. The next step would be to build a prototype of the detector to validate the simulation results and to test it on a D-T neutron source. The second part of the thesis describes the design and build of the IFOx sensor, an ultra-fast oxygen sensor that can be used for lung analysis by working in the so called mainstream configuration. Since the working principle of the IFOx sensor somewhat resembles the one of a scintillator detector, this is an example of knowledge transfer from nuclear diagnostics to a different application. The prototype that was built features excellence time response and was used in a trial study on healthy volunteers to measure the Functional Residual Capacity. The excellent results of the trial study on healthy volunteers has opened up the possibility to carry out a clinical study on intensive care unit patients in the near future, by integrating the oxygen sensor with mechanical ventilators. The last part of the thesis is about the MVM project and describes the ventilator design aimed to the production of a ventilator composed of a few parts so that it can be rapidly built on large scales even during the disruption of the components supply chain. I was able to contribute to the project thanks to my knowledge of gas systems, advanced real time controls, and I participated in the measurement required for the certification. The key results that led to a full certification for usage on patient by the European Commission are also described in this work.

Lo scopo di questa tesi, iniziata a novembre 2019, è lo sviluppo di un rivelatore Cherenkov per misurare i raggi gamma da 17 MeV emessi dalla reazione di fusione D-T. Con l'espandersi della pandemia da COVID-19 nel nord Italia, a metà febbraio 2020, è divenuto evidente che il piano iniziale del mio lavoro di tesi dovesse essere fortemente cambiato, a causa della cancellazione delle attività sperimentali che avrebbero dovuto svolgersi nei laboratori UNIMIB/CNR a Milano e al Joint European Torus nel Regno Unito. In accordo con i miei tutor ho iniziato, insieme ad altri ricercatori, a lavorare su base volontaria ad un progetto denominato Mechanical Ventilator Milano (MVM). Il progetto MVM ha coinvolto un gruppo internazionale di più di 150 scienziati e ha prodotto in meno di tre mesi un ventilatore meccanico certificato dalla Food and Drugs Administration per uso su pazienti affetti da COVID-19 in terapia intensiva. L'attività su MVM ha portato, circa un anno dopo, allo sviluppo di un nuovo sensore di ossigeno veloce per applicazioni mediche. Il sensore è in grado di misurare il consumo di ossigeno di un individuo in tempo reale e durante un singolo respiro. La tesi è divisa in tre parti. La prima parte si concentra sullo sviluppo di un contatore di raggi gamma ottimizzato per la misura della potenza di fusione in un reattore a confinamento magnetico. Il gruppo di ricerca in cui mi sono inserito sta sviluppando un metodo innovativo per la misura della potenza prodotta dalle reazioni di fusione basato sulla rivelazione dei raggi gamma da 17 MeV prodotti durante la reazione D+T->5He*. Tipicamente il nucleo di 5He* decade emettendo una particella alfa e un neutrone, ma può anche diseccitarsi sullo stato fondamentale dell'5He, prima che questo si disintegri in una particella alfa e un neutrone, con una probabilità di 10^-5. Questi raggi gamma sono stati misurati al JET nella campagna DT appena conclusa con uno spettrometro gamma basato su un cristallo di LaBr3 e una acquisizione dati digitale veloce. Poiché l'efficienza ai raggi gamma e ai neutroni del LaBr3 è simile, è stato necessario usare un attentatore neutronico dedicato per osservare il debole segnale dovuto ai raggi gamma. Per superare i problemi dovuti alla sensibilità del LaBr3 ai neutroni ho progettato un rivelatore gamma a gas ottimizzato per funzionare in presenza di un intenso fondo neutronico. il rivelatore è basato sull'effetto Cherenkov e le simulazioni indicano che è 10^6 volte più sensibile ai raggi gamma che ai neutroni. Il prossimo passo sarà quello di costruire un prototipo del rivelatore per validare le simulazioni e provarlo su una sorgente di neutroni D-T. La seconda parte della tesi descrive lo sviluppo del sensore IFOx, un sensore di ossigeno ultra-veloce che può essere utilizzato per l'analisi polmonare. Poiché il principio di funzionamento del sensore è simile a quello di uno scintillatore, è un esempio di trasferimento di conoscenze dal campo delle diagnostiche nucleari ad applicazioni diverse. Il prototipo del sensore è caratterizzato da un'eccellente risposta temporale ed è stato utilizzato per misurare la Capacità Funzionale Residua in volontari sani. I risultati eccellenti del test sui volontari sani hanno aperto la via per uno studio clinico su pazienti intubati, durante il quale il sensore verrà integrato con un ventilatore polmonare. L'ultima parte della tesi riguarda MVM e descrive la progettazione di un ventilatore che necessita poche parti e che può essere costruito in tempi brevi anche durante una interruzione della catena di approvvigionamento dei materiali. Ho contribuito al progetto grazie alla mia esperienza sui sistemi gas e sui controlli software in tempo reale, e ho partecipato alle misure necessarie ad ottenere la calibrazione. I risultati principali che hanno portato alla certificazione per uso umano da parte della Comunità Europea sono descritti nella tesi.

(2023). Development of a Cherenkov based diagnostic for gamma-rays from fusion plasmas and advanced medical applications. (Tesi di dottorato, Università degli Studi di Milano-Bicocca, 2023).

Development of a Cherenkov based diagnostic for gamma-rays from fusion plasmas and advanced medical applications

PUTIGNANO, OSCAR
2023

Abstract

Aim of this thesis, begun in November 2019, is the development of an innovative Cerenkov detector for measurements of 17 MeV gamma-rays emitted by the D-T fusion reaction in an intense neutron field. With the spread of the COVID-19 pandemics in Northern Italy in February 2020, it became clear that the original program planned for my PhD work had to be significantly changed, since experimental activities to be carried out in the UNIMIB/CNR laboratories in Milan and at the Joint European Torus in the UK had to be cancelled. In agreement with my tutors I volunteered together with other scientists to contribute to a project called Mechanical Ventilator Milan (MVM). The MVM project involved an international team of more than 150 scientists and has produced over the very short period of less than three months a mechanical ventilator approved by the American Food and Drug Administration for use at the intensive care unit of hospitals to treat patients affected by COVID-19. The activities of the MVM project led to the development of a new fast oxygen sensor for medical application, about one year later. The sensor measures the oxygen consumption in real time during a single breath. The thesis is organized in three parts. The first part is focused on the development of a gamma-ray counter optimized for the measurement of the D-T fusion power produced in a magnetic confinement fusion device. The research team I have joined is developing a novel technique for the measurement of DT fusion power in a magnetic confinement device based on the detection of 17 MeV gamma-rays also produced by the D+T->5He* reaction. The 5He* nucleus promptly decays usually emitting an alpha particle and a neutron, but it may de-excite to the ground level emitting a gamma-ray with a probability of the order of 10^-5. These gamma-rays have been detected in the recent DT campaign at JET with a gamma spectrometer based on LaBr3 and a fast digital data acquisition. Since the efficiency of the scintillator to high energy gamma-rays and neutrons are comparable, the use of a dedicated LiH based neutron attenuator to observe the weak gamma-ray signal is needed. To overcome the limitations posed by the sensitivity of LaBr3 detectors to neutrons, I designed a gamma-ray gas detector optimized to work in the presence of an intense neutron field. The detector is based on the Cherenkov effect and simulations indicate that it is 10^6 times more sensitive to gamma-rays than to neutrons. The next step would be to build a prototype of the detector to validate the simulation results and to test it on a D-T neutron source. The second part of the thesis describes the design and build of the IFOx sensor, an ultra-fast oxygen sensor that can be used for lung analysis by working in the so called mainstream configuration. Since the working principle of the IFOx sensor somewhat resembles the one of a scintillator detector, this is an example of knowledge transfer from nuclear diagnostics to a different application. The prototype that was built features excellence time response and was used in a trial study on healthy volunteers to measure the Functional Residual Capacity. The excellent results of the trial study on healthy volunteers has opened up the possibility to carry out a clinical study on intensive care unit patients in the near future, by integrating the oxygen sensor with mechanical ventilators. The last part of the thesis is about the MVM project and describes the ventilator design aimed to the production of a ventilator composed of a few parts so that it can be rapidly built on large scales even during the disruption of the components supply chain. I was able to contribute to the project thanks to my knowledge of gas systems, advanced real time controls, and I participated in the measurement required for the certification. The key results that led to a full certification for usage on patient by the European Commission are also described in this work.
TARDOCCHI, MARCO
NOCENTE, MASSIMO
fusione nucleare; raggi gamma; neutroni; sensore ossigeno; ventilatore meccanic
nuclear fusion; gamma-ray; neutrons; oxygen sensor; mechanic ventilator
FIS/03 - FISICA DELLA MATERIA
Italian
19-gen-2023
FISICA E ASTRONOMIA
35
2021/2022
embargoed_20260119
(2023). Development of a Cherenkov based diagnostic for gamma-rays from fusion plasmas and advanced medical applications. (Tesi di dottorato, Università degli Studi di Milano-Bicocca, 2023).
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/402358
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