Measurement and interpretation of laser accelerated protons at GSI

  • This thesis is structured into 7 chapters: • Chapter 2 gives an overview of the ultrashort high intensity laser interaction with matter. The laser interaction with an induced plasma is described, starting from the kinematics of single electron motion, followed by collective electron effects and the ponderamotive motion in the laser focus and the plasma transparency for the laser beam. The three different mechanisms prepared to accelerate and propagate electrons through matter are discussed. The following indirect acceleration of protons is explained by the Target Normal Sheath Acceleration (TNSA) mechanism. Finally some possible applications of laser accelerated protons are explained briefly. • Chapter 3 deals with the modeling of geometry and field mapping of magnetic lens. Initial proton and electron distributions, fitted to PHELIX measured data are generated, a brief description of employed codes and used techniques in simulation is given, and the aberrations at the solenoid focal spot is studied. • Chapter 4 presents a simulation study for suggested corrections to optimize the proton beam as a later beam source. Two tools have been employed in these suggested corrections, an aperture placed at the solenoid focal spot as energy selection tool, and a scattering foil placed in the proton beam to smooth the radial energy beam profile correlation at the focal spot due to chromatic aberrations. Another suggested correction has been investigated, to optimize the beam radius at the focal spot by lens geometry controlling. • Chapter 5 presents a simulation study for the de-neutralization problem in TNSA caused by the fringing fields of pulsed magnetic solenoid and quadrupole. In this simulation, we followed an electrostatic model, wherethe evolution of both, self and mutual fields through the pulsed magnetic solenoid could be found, which is not the case in the quadrupole and only the growth of self fields could be found. The field mapping of magnetic elements is generated by the Matlab program, while the TraceWin code is employed to study the tracking through magnetic elements. • Chapter 6 describes the PHELIX laser parameters at GSI with chirp pulse amplification technique (CPA), and Gafchromic Radiochromic film RCF) as a spatial energy resolver film detector. The results of experiments with laser proton acceleration, which were performed in two experimental areas at GSI (Z6 area and PHELIX Laser Hall (PLH)), are presented in section 6.3. • Chapter 7 includes the main results of this work, conclusions and gives a perspective for future experimental activities.
  • Eine wichtige Folge der Chirped-Puls-Verstärkungstechnik war die Entwicklung von Lasersystemen, die ultrakurze (Femtosekunden) Laserpulse mit über ein Terawatt produzieren können. Die Fokussierung der Laserpulse auf wenige Mikrometer erhöht die Laserintensit¨at enorm, man erreicht heute 1018 W/cm2 Die ultrakurzen und ultraintensiven Laserpulse erreichen elektrische Feldstärken, welche die atomaren Felder überschreiten. Sie ionisieren umgehend die getroffene Metalloberfläche, was zu einem Vorplasma führt. Die Elektronen absorbieren direkt einen Teil der Laserenergie durch diese Wechselwirkung. Die Elektronen mit hoher Energie propagieren durch das Taget und bauen beim Austritt das beschleunigende Feld für Ionen auf, die aus der Targetrückseite gelöst und beschleunigt werden. Diese Ionen erreichen eine Energie von mehreren MeV mithilfe von ultrahohen elektrostatischen Feldern - bis zu TV/m. Die beschleunigten Ionen sind ganz überwiegend Protonen aus den Adsorbaten der Targetoberfläche. Die gewonnenen Protonen und der Elektronenpuls verlassen die Targetückseite als quasi neutrale Verteilung. Diese Beschleunigung aus der nicht bestrahlten Targetoberfl¨ache durch das quasistatische elektrische Feld wird als TNSA (Target Normal Shearth Acceleration) bezeichnet.

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Author:Husam Al-Omari
Place of publication:Frankfurt am Main
Referee:Ingo HofmannGND, Ulrich RatzingerORCiD
Document Type:Doctoral Thesis
Date of Publication (online):2014/05/07
Year of first Publication:2014
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Granting Institution:Johann Wolfgang Goethe-Universität
Date of final exam:2014/04/28
Release Date:2014/05/07
Page Number:XXI, 151, 4
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik
Licence (German):License LogoDeutsches Urheberrecht