Development of a tracking detector to study the 12C(,)16O ... Duarte- Declaration of Authorship

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Transcript of Development of a tracking detector to study the 12C(,)16O ... Duarte- Declaration of Authorship

  • Università degli Studi della Campania - Luigi Vanvitelli

    Doctoral Thesis

    Development of a tracking detector to study the 12C(α,γ)16O reaction

    Author:

    Jeremias Garcia Duarte

    Supervisor:

    Prof. Lucio Gialanella

    Doctor Europaeus Referees:

    Prof. Shawn Bishop

    Prof. Marialuisa Aliotta

    Dottorato di Ricerca in Matematica, Fisica e applicazioni - 31◦ ciclo

    Settori scientifico-disciplinari MIUR: FIS/01 e FIS/04

    A thesis submitted in fulfillment of the requirements

    for the degree of Doctor of Philosophy in Physics

    and Doctor Europaeus

    in the

    Dipartimento di Matematica e Fisica

    April 2019

    https://www.unina2.it/ https://www.unina2.it/ http://lattes.cnpq.br/9251619340346010 http://www.matfis.unina2.it/dipartimento-205/persone/docenti/item/16-gialanella-lucio http://www.professoren.tum.de/en/bishop-shawn/ https://www.ph.ed.ac.uk/people/marialuisa-aliotta https://www.matfis.unina2.it/

  • Contents

    Contents

    Declaration of Authorship iv

    Abstract vi

    Abstract in Italiano vii

    Acknowledgements viii

    1 Introduction - Stellar Evolution 3

    1.1 Stellar nucleosynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

    1.2 Hydrostatic Helium burning . . . . . . . . . . . . . . . . . . . . . . . . . . 4

    1.3 Cross section in the Gamow energy region . . . . . . . . . . . . . . . . . . 5

    1.4 Experimental overview of 12C(α,γ)16O . . . . . . . . . . . . . . . . . . . . 6

    1.5 Aim of this work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

    2 Experimental Setup 10

    2.1 CIRCE Facility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

    2.2 The recoil mass separator ERNA . . . . . . . . . . . . . . . . . . . . . . . 10

    2.3 Angular and energy distributions of 16O-recoils . . . . . . . . . . . . . . . 11

    2.4 The 12C(α,γ)16O reaction mechanism . . . . . . . . . . . . . . . . . . . . 15

    2.5 Angular distribution of γ-rays . . . . . . . . . . . . . . . . . . . . . . . . . 16

    2.5.1 Ground state transitions . . . . . . . . . . . . . . . . . . . . . . . . 16

    2.5.2 Cascade transitions . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

    2.6 Monte Carlo simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

    2.6.1 Ground state transitions . . . . . . . . . . . . . . . . . . . . . . . . 23

    2.6.2 Cascade transitions . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

    2.6.3 The ∆E/E, θ16O correlation . . . . . . . . . . . . . . . . . . . . . . 25

    2.6.4 Energy, angle correlation after ERNA transport . . . . . . . . . . . 26

    2.6.5 The separation of E1 and E2 g.s. contributions . . . . . . . . . . . 27

    2.6.6 The 12C leaky beam . . . . . . . . . . . . . . . . . . . . . . . . . . 30

    3 Detector design 34

    i

  • Contents ii

    3.1 A single stage tracking detector: TPC-GEM . . . . . . . . . . . . . . . . . 34

    3.2 Start 2D detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

    3.2.1 Electron production . . . . . . . . . . . . . . . . . . . . . . . . . . 35

    3.2.2 Electron collection and transport . . . . . . . . . . . . . . . . . . . 38

    3.2.2.1 Electron collection: Acceleration grid . . . . . . . . . . . 39

    3.2.2.2 Electron collection: Acceleration rings . . . . . . . . . . . 42

    3.2.2.3 Electron transport: Electrostatic mirror . . . . . . . . . . 42

    3.2.2.4 Electron transport: Magnetic mirror . . . . . . . . . . . . 46

    3.2.3 Electron detection: MCP with delay line anode (DLA) . . . . . . . 46

    3.2.4 The detector final design . . . . . . . . . . . . . . . . . . . . . . . 50

    3.2.5 The construction process . . . . . . . . . . . . . . . . . . . . . . . 61

    3.3 Stop 2D detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

    3.3.1 The position sensitive parallel wire plane . . . . . . . . . . . . . . 65

    3.3.2 Detector construction . . . . . . . . . . . . . . . . . . . . . . . . . 66

    3.4 Electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

    3.4.1 Signal processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

    4 Data Taking and Analysis 72

    4.1 ERNA alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

    4.2 ERNA mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

    4.2.1 Undeflected beam mapping . . . . . . . . . . . . . . . . . . . . . . 75

    4.2.2 ±30 mrad mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 4.2.3 SS6 and SS7 scan test . . . . . . . . . . . . . . . . . . . . . . . . . 77

    4.2.4 SS6 and SS7 scan . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

    4.2.5 Experimental transport matrix . . . . . . . . . . . . . . . . . . . . 78

    4.2.6 SS6 and SS7 scan - Energy shift . . . . . . . . . . . . . . . . . . . 81

    4.3 Acceptances of ERNA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

    4.3.1 Deflection unit calibration . . . . . . . . . . . . . . . . . . . . . . . 82

    4.3.2 Angular acceptance . . . . . . . . . . . . . . . . . . . . . . . . . . 86

    4.3.3 Energy acceptance . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

    4.3.4 Target effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

    4.3.5 Tunings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

    4.4 MWPC characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

    4.5 CPD characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

    4.6 12C, 16O separation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

    5 Conclusions and Outlook 103

    A erna.2.3.fox 105

    B trackmir.cpp 148

    C Technical drawings of the electrostatic mirror 153

    D Technical drawings of the welding tools 166

    E Technical drawings of the MWPC detector 171

  • Contents iii

    F Preliminary tests of MWPC 176

    F.1 Investigating the source of the noise . . . . . . . . . . . . . . . . . . . . . 177

    G Numerical minimization 179

    References 181

    List of Figures 191

  • Declaration of Authorship

    I, Jeremias Garcia Duarte, declare that this thesis entitled, ’Development of a track-

    ing detector to study the 12C(α,γ)16O reaction’ and the work presented in it are my

    own. I confirm that:

    � This work was done mainly while in candidature for a PhD degree at the University

    of Campania - Luigi Vanvitelli.

    � Where any part of this thesis has previously been submitted for a degree or any

    other qualification at this University or any other institution, this has been clearly

    stated.

    � Where I have consulted the published work of others, this is always clearly at-

    tributed.

    � Where I have quoted from the work of others, the source is always given. With

    the exception of such quotations, this thesis is entirely my own work.

    � I have acknowledged all main sources of help.

    � Where the thesis is based on work done by myself jointly with others, I have made

    clear exactly what was done by others and what I have contributed myself.

    Signed:

    Date:

    iv

  • “If all this is true, stars have a life cycle much like animals. They get born, they grow,

    they go through a definite internal development, and finally they die, to give back the

    material of which they are made so that new stars may live.”

    Hans Albrecht Bethe, Nobel Lecture, 1967

    “My major theme has been that all of the heavy elements from carbon to uranium have

    been synthesized in stars. Let me remind you that your bodies consist for the most part

    of these heavy elements. Apart from hydrogen you are 65 percent oxygen and 18 percent

    carbon with smaller percentages of nitrogen, sodium, magnesium, phosphorus, sulfur,

    chlorine, potassium, and traces of still heavier elements. Thus it is possible to say that

    you and your neighbor and I, each one of us and all of us, are truly and literally a little

    bit of stardust.”

    William Alfred Fowler, Nobel Lecture, 1983

  • UNIVERSITÀ DEGLI STUDI DELLA CAMPANIA - LUIGI VANVITELLI

    Abstract

    Dipartimento di Matematica e Fisica

    Doctor of Philosophy in Physics

    Development of a tracking detector to study the 12C(α,γ)16O reaction

    by Jeremias Garcia Duarte

    12C+4He is of utmost importance in stellar evolution and nucleosynthesis. As a conse-

    quence, many efforts were done in the last decades to determine its stellar rate, that in

    spite of the remarkable progress, is not yet known with the precision required to com-

    pare the predictions of stellar models to observations. In 2005 the ERNA collaboration

    published the results of a measurement exploring, for the first time, the direct detection

    of the 16O recoils using a mass separator. This measurement showed the potentiality of

    this approach, whereas the usefulness of the results was limited by the lack of informa-

    tion on the reaction mechanism and the impossibility to reach an energy lower than Ecm

    = 1.9 MeV. The aim of my work is to develop a new tracking detector and investigate

    the specifications of an improved design of ERNA, for a new