CZECH TECHNICAL UNIVERSITY IN PRAGUE Faculty of Nuclear Sciences and Physical Engineering Department of Physics Bachelor Thesis Study of Thermonuclear Plasma Using Semiconductor Detectors Peter vihra Supervisor: Ing. Michal Mar£i²ovský Consultant: Ing. Martin Hejtmánek Prague, 2015 ESKÉ VYSOKÉ UENÍ TECHNICKÉ V PRAZE Fakulta Jaderná a Fyzikáln¥ Inºenýrská Katedra fyziky Bakalá°ská práce Studium termojaderného plazmatu polovodi£ovými detektory Peter vihra Vedoucí práce: Ing. Michal Mar£i²ovský Konzultant: Ing. Martin Hejtmánek Praha, 2015 Na toto místo p°ijde svázat zadání bakalá°ské práce! V jednom z výtisk· musí být originál zadání, v ostatních kopie. Declaration I hereby declare, that I've written this thesis by myself and I've used only the materials stated in the references section. I have no reason to object to use this work according to the section 60 of Act No. 121/2000 Coll.,On Copyright, on Rights Related to Copyright, and on Change of Some Acts (Copyright Act) Prague, date........................... Peter vihra Acknowledgement I would like to express my gratitude to everyone who supported me during the creation of this work. I am very grateful to my supervisor Ing. Michal Mar£i²ovský and to my consultant Ing. Martin Hejtmánek for their patience, willingness and professional assistance during writing this thesis. My thanks also belong to Ing. Jakub Cikhardt for his help with operating the plasma focus PFZ200. Thesis title: Study of Thermonuclear Plasma Using Semiconductor Detectors Author: Peter vihra Field of study: Physics and Technology of Thermonuclear Fusion Thesis type: Bachelor thesis Supervisor: Ing. Michal Mar£i²ovský Consultant: Ing. Martin Hejtmánek Abstract: Plasma physics and thermonuclear fusion provide a promising route to a new reliable en- ergy source. This thesis investigates properties of plasma behaviour using semiconductor pixel detectors. These detector systems are well understood as semiconductor trackers have been extensively employed in particle physics. Plasma is a quasineutral state of matter that exhibits collective behaviour. Ther- monuclear fusion occurs when dense plasma is heated to high temperatures. The reaction between light nuclei releases excessive binding energy. Currently, a number of experiments using magnetic or inertial connement are being developed as tools for harvesting this energy. Possibility of investigation of plasma properties is to some extent determined by the choice of detectors of the plasma burst products. The theoretical part of this thesis covers processes of interaction of ionizing radiation with matter. The relevant characteristics of semiconductor detectors are explored in detail. Designing a new diagnostic method consists of three phases: simulation, construction and measurement. Design characteristics of PFZ-200 plasma focus and Medipix2, Timepix semiconductor pixel detectors are given. The results from the measurement show that employing this approach provides new opportunities of plasma diagnostics. However, a comparison to other methods and threshold energy specication is advised for suitable interpretation. Keywords: thermonuclear fusion, plasma focus PFZ-200, Medipix2 MXR, Timepix, silicon particle detector Název práce: Studium termojaderného plazmatu polovodi£ovými detektory Autor: Peter vihra Obor: Fyzika a technika termojaderné fúze Druh práce: Bakalá°ská práce Vedoucí práce: Ing. Michal Mar£i²ovský Konzultant: Ing. Martin Hejtmánek Abstrakt: Fyzika plazmatu a termonukleární fúze poskytuje slibnou cestu k novému a spolehlivému zdroji energie. Tato práce zkoumá vlastnosti plazmatu pomocí polovodi£ových pixelových detektor·. Problematika polovodi£ových senzor· je velmi dob°e známa p°edev²ím pro jejich pouºití v £ásticové fyzice. Plazma je kvazineutrální skupenství hmoty vykazující kolektivné chování. Termonuk- leární fúze nastává, kdyº je husté plazma zah°áto na vysokou teplotu. Tato reakce mezi dv¥ma atomy lehkých jader uvol¬uje p°ebyte£nou vazebnou energii. V sou£asnosti je vyvíjeno velké mnoºství experiment· pouºívajících magnetické nebo inerciální udrºení jako nástroj· ur£ených k získávání této energie. Moºnost zkoumání vlastností plazmatu je v jisté mí°e ur£ena volbou detektor· plaz- mových výbuch·. Teoretická £ást této práce pokrývá procesy interakce ionizujícího zá°ení s látkou. D·leºité vlastnosti polovodi£ových detektor· jsou do detail· prozkoumány. Návrh nové diagnostické metody sestává ze t°í fází: simulace, konstrukce a m¥°ení. Uvedeny jsou rovn¥º konstruk£ní parametry plazma fokusu PFZ-200 a polovodi£ových pixelových detektor· Medipix2 a Timepix. Výsledky m¥°ení poukazují, ºe pouºití této metody poskytuje nové moºnosti diagnostiky plazmatu. Av²ak, pro vhodnou interpretaci je doporu£eno porovnání s jinými metodami a stanovení prahové energie. Klí£ová slova: termojaderná fúze, plazma fokus PFZ-200, Medipix2 MXR, Timepix, k°emíkový detektor £ástic Contents Contents XI List of Figures XIII Introduction XV 1 Plasma Physics and Experiments 1 1.1 Thermonuclear fusion . .2 1.2 Experiments . .5 1.2.1 Tokamak . .5 1.2.2 Inertial fusion . .5 1.2.3 Magnetic Pinch . .7 1.2.4 Plasma focus . .8 2 Plasma Instabilities 11 2.1 Bennett Equilibrium . 11 2.2 Instabilities . 12 2.2.1 Sausage Instability . 13 2.2.2 Kink Instability . 13 2.2.3 Rayleigh-Taylor Instability . 14 2.2.4 Diocotron Instability . 14 2.3 Hotspots . 15 3 Ionizing Radiation and Semiconductor Detectors 17 3.1 BetheBloch formula . 17 3.1.1 Interaction of ionizing radiation . 18 3.2 Detectors . 20 3.2.1 Gaseous ionization detectors . 20 3.2.2 Solidstate detectors . 21 3.3 Semiconductor detectors . 21 3.3.1 Microstrip detectors . 22 3.3.2 Pixel detectors . 24 4 Apparatus 25 4.1 PFZ-200 . 25 4.1.1 Parameters . 25 XI XII CONTENTS 4.1.2 Diagnostics . 25 4.2 Medipix2 . 27 4.2.1 Parameters . 27 4.2.2 Readout . 29 4.3 Timepix . 29 4.4 Monte Carlo simulation . 30 4.4.1 Geant4 . 30 5 Results 31 5.1 Simulation . 31 5.1.1 Parameters . 31 5.1.2 Setup . 31 5.1.3 Transmittance . 32 5.2 Construction . 33 5.2.1 First attempt . 33 5.2.2 Second attempt . 34 5.2.3 Third attempt . 36 5.2.4 Fourth attempt . 37 5.3 Measurement . 37 5.3.1 Medipix2 . 37 5.3.2 Timepix . 39 Conclusions 43 Bibliography 45 List of Figures 1.1 Distribution of matter and energy in the universe . .1 1.2 Average binding energy per nucleon, against number of nucleons in nucleus2 1.3 Gamow peak for Maxwellian distribution . .4 1.4 Crosssection and reactivity of selected fusion reactions . .4 1.5 Inertial fusion, comparison of a direct and an indirect drive . .6 1.6 Process of the thermonuclear bomb explosion . .6 1.7 Comparison of z, θ and θz pinch . .7 1.8 Scheme of a plasma focus . .8 1.9 Breakdown phase of a plasma focus . .9 2.1 Sausage instability . 13 2.2 Kink instability . 13 2.3 Developement of Rayleigh-Taylor instability . 14 2.4 Crosssection of diocotron instability . 15 2.5 Schlieren photography of pinch, highlight of hotspots . 15 3.1 Stopping energy for muons in copper . 18 3.2 Detection of electrons and alpha particles depending on absorber thickness 19 3.3 Eect of detector voltage on gas amplication factor and observed count rate for gaseous ionization detectors . 21 3.4 Widening of depletion region . 22 3.5 Specic energy loss calculated for dierent charged particles in silicon . 23 3.6 Mass attenuation coecient for photons in silicon . 23 3.7 Crosssectional view of doublesided silicon strip detector . 23 3.8 Crosssectional view of monolithic and hybrid pixel detector . 24 4.1 Scheme of plasma focus PFZ-200 . 26 4.2 A straight channel electron multiplier . 26 4.3 Microchannel plate . 26 4.4 Principle of schlieren photography . 27 4.5 Schematic and real picture of Medipix2 chipboard . 28 4.6 Medipix2 pixel cell blocks diagram . 28 4.7 USB interface 1.0 . 29 4.8 Pixelman interface . 30 5.1 Simulation of photon transfer through pinhole and detection in sensor . 32 XIII XIV LIST OF FIGURES 5.2 Simulated and real transmittance of lead and aluminium for photons . 33 5.3 The apparatus for the measurement with USB interface 1.0 . 34 5.4 Lost conguration of detector . 35 5.5 The connection of Medipix2 apparatus to the plasma focus device . 35 5.6 The apparatus for the measurement with Muros2 . 36 5.7 Connected Timepix apparatus to the plasma focus device . 37 5.8 Displayed data matrices from Medipix2 . 38 5.9 Displayed data from the microchannel plate detector . 39 5.10 Displayed data matrices from Timepix rst conguration . 40 5.11 Displayed data matrices from Timepix second conguration . 40 Introduction Currently, the annual world primary energy consumption is enormous, roughly 540 EJ. Given these conditions, it is expected that fossil fuels will be exhausted within a couple of decades [1]. Renewable energy sources, e.g. sunlight and wind, have yet to prove their dependability, while ssion is considered dangerous due to a possibility of nuclear and radiation accidents. This situation could be resolved by developing a reliable and stable source of energy such as thermonuclear fusion. Fusion of atoms is a process which requires relatively high initial energies, and even under these conditions happens with a low probability. This probability can be enhanced by achieving fusion in plasma where crosssection of the reaction is large. Although scientists have already managed to execute an operational thermonuclear reaction, many theoretical and technological challenges have to be overcome before thermonuclear power can be eciently harvested. There are two major engineering problems: heating and containment of plasma. This thesis studies a new diagnostic method in plasma research which uses semi- conductor pixel detectors, which are widely employed in particle physics. It focuses on theoretical understanding, numerical simulations, construction of the apparatus and per- forming measurements. Plasma is a quasineutral state of matter that exhibits collective behaviour. Ther- monuclear fusion occurs when dense plasma is heated to high temperatures.