Download or read book Intra pulse Dynamics of Laser driven Ion Acceleration in Ultra thin Foils written by Hersimerjit Padda and published by . This book was released on 2017 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt: Through variation of the target foil thickness, the opening angle of the ring is shown to be correlated to the point in time during the laser pulse interaction at which the target becomes transparent to the laser (in a process termed relativistic induced transparency). The ring is largest when transparency occurs close to the peak of the laser intensity.

Download or read book Ion Acceleration in Ultra thin Foils Undergoing Relativistically Induced Transparency written by Haydn W. Powell and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis reports on experimental and numerical investigations of ion acceleration and the underlying mechanisms of energy transfer in the interaction of intense laser pulses with ultra-thin foils undergoing relativistic induced transparency. The optimisation and optical control of the ion beam properties including the beam flux, maximum energy and energy spread is important for the development of applications of laser-driven ion beams. Multiple laser-ion acceleration mechanisms, driven by sheath fields, radiation pressure and transparency enhancement occur in intense laser pulse interactions with an ultra-thin foil. This is experimentally and numerically demonstrated in the work presented in this thesis. Results from an experimental investigation of ion acceleration from ultra-thin (nanometer-thick) foils using the Vulcan petawatt laser facility are presented. Spatially separating the multiple beam components arising from the differing acceleration mechanisms enables the underlying physics of the individual mechanisms to be investigated. In the case of foils undergoing relativistic induced transparency, it is shown that an extended channel and resulting jet is formed in the expanding plasma at the rear of the target, resulting in higher laser energy absorption into electrons and enhanced ion acceleration in a localised region. This results from volumetric heating of electrons by the laser pulse propagating within the channel. The measured maximum energy of the protons in the enhanced region of the jet is found to be highly sensitive to the laser pulse contrast and rising edge intensity profile of the laser. It is shown, using a controlled pre-expansion of the target, that an increase in the maximum proton energy by a factor two is achievable. Numerical investigations of the interaction, using particle-in-cell (PIC) simulations, show that an idealised sharp rising edge Gaussian laser intensity profile produces the highest proton energy, though this condition could not be achieved experimentally. The simulations show that controlled pre-expansion of the target, by variation of the rising edge intensity profile, enables better conditions for channel formation and energy coupling to electrons and thus protons. A detailed numerical (PIC) investigation of the mechanisms of laser energy transfer to electrons and ions in thin foils undergoing relativistically induced transparency is also presented. The role of streaming instabilities in the transfer of energy between particle species is investigated. It is found that in addition to the relativistic Buneman instability, which arises from streaming of the volumetrically heated relativistic electrons with the background ions during transparency, ionion streaming in the expanding plasma also plays a role in enhancing the final ion energy. Enhancement of proton maximum energies via ion-ion streaming from shock-accelerated aluminium ions is observed in 1D PIC simulations and the energy exchange is demonstrated to be sensitive to the plasma density. Energy transfer between co-directional ion species is also observed in higher dimension 2D simulations. The simulations show that the greatest enhancement in proton energy is due to streaming of electrons in the region of the plasma jet formed in the expanding plasma.

Download or read book Ion acceleration and extreme light field generation based on ultra short and ultra intense lasers written by Liangliang Ji and published by Springer Science & Business Media. This book was released on 2014-01-23 with total page 93 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is dedicated to the relativistic (laser intensity above 1018 W/cm2) laser-plasma interactions, which mainly concerns two important aspects: ion acceleration and extreme-light-field (ELF). Based on the ultra-intense and ultra–short CP lasers, this book proposes a new method that significantly improves the efficiency of heavy-ion acceleration, and deals with the critical thickness issues of light pressure acceleration. More importantly, a series of plasma approaches for producing ELFs, such as the relativistic single-cycle laser pulse, the intense broad-spectrum chirped laser pulse and the ultra-intense isolated attosecond (10-18s) pulse are introduced. This book illustrates that plasma not only affords a tremendous accelerating gradient for ion acceleration but also serves as a novel medium for ELF generation, and hence has the potential of plasma-based optics, which have a great advantage on the light intensity due to the absence of device damage threshold.

Download or read book Ion Acceleration from the Interaction of Ultra Intense Lasers with Solid Foils written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The discovery that ultra-intense laser pulses (I> 10[sup 18] W/cm[sup 2]) can produce short pulse, high energy proton beams has renewed interest in the fundamental mechanisms that govern particle acceleration from laser-solid interactions. Experiments have shown that protons present as hydrocarbon contaminants on laser targets can be accelerated up to energies> 50 MeV. Different theoretical models that explain the observed results have been proposed. One model describes a front-surface acceleration mechanism based on the ponderomotive potential of the laser pulse. At high intensities (I> 10[sup 18] W/cm[sup 2]), the quiver energy of an electron oscillating in the electric field of the laser pulse exceeds the electron rest mass, requiring the consideration of relativistic effects. The relativistically correct ponderomotive potential is given by U[sub p] = ([1 + I[lambda][sup 2]/1.3 x 10[sup 18]][sup 1/2] - 1) m[sub o]c[sup 2], where I[lambda][sup 2] is the irradiance in W [micro]m[sup 2]/cm[sup 2] and m[sub o]c[sup 2] is the electron rest mass. At laser irradiance of I[lambda][sup 2] [approx] 10[sup 20] W [micro]m[sup 2]/cm[sup 2], the ponderomotive potential can be of order several MeV. A few recent experiments--discussed in Chapter 3 of this thesis--consider this ponderomotive potential sufficiently strong to accelerate protons from the front surface of the target to energies up to tens of MeV. Another model, known as Target Normal Sheath Acceleration (TNSA), describes the mechanism as an electrostatic sheath on the back surface of the laser target. According to the TNSA model, relativistic hot electrons created at the laser-solid interaction penetrate the foil where a few escape to infinity. The remaining hot electrons are retained by the target potential and establish an electrostatic sheath on the back surface of the target. In this thesis we present several experiments that study the accelerated ions by affecting the contamination layer from which they originate. Radiative heating was employed as a method of removing contamination from palladium targets doped with deuterium. We present evidence that ions heavier than protons can be accelerated if hydrogenous contaminants that cover the laser target can be removed. We show that deuterons can be accelerated from the deuterated-palladium target, which has been radiatively heated to remove contaminants. Impinging a deuteron beam onto a tritiated-titanium catcher could lead to the development of a table-top source of short-pulse, 14-MeV fusion neutrons. We also show that by using an argon-ion sputter gun, contaminants from one side of the laser target can be selectively removed without affecting the other side. We show that irradiating a thin metallic foil with an ultra-intense laser pulse produces a proton beam with a yield of 1.5-2.5 10[sup 11] and temperature, kT = 1.5 MeV with a maximum proton energy> 9 MeV. Removing contaminants from the front surface of the laser target with an argon-ion sputter gun, had no observable effect on the proton beam. However, removing contaminants from the back surface of the laser target reduced the proton beam by two orders of magnitude to, at most, a yield of [approx] 10[sup 9] and a maximum proton energy 4 MeV. Based on these observations, we conclude that the majority ( 99%) of high energy protons (E> 5 MeV) from the interaction of an ultra-intense laser pulse with a thin foil originate on the back surface of the foil--as predicted by the TNSA model. Our experimental results are in agreement with PIC simulations showing back surface protons reach energies up to 13 MeV, while front surface protons reach a maximum energy of 4 MeV. Well diagnosed and controllable proton beams will have many applications: neutron radiography, material damage studies, production of medical isotopes, and as a high-resolution radiography tool for diagnosing opaque materials and plasmas. Well collimated and focusable ion beams may also prove beneficial for alternative inertial-fusion concepts such as proton fast ignition, a potentially viable method for achieving a controlled fusion reaction in the laboratory earlier than expected.

Download or read book Theoretical and Numerical Study of the Laser plasma Ion Acceleration written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The laser driven ion acceleration is a burgeoning field of resarch and is attracting a growing number of scientists since the first results reported in 2000 obtained irradiating thin solid foils by high power laser pulses. The growing interest is driven by the peculiar characteristics of the produced bunches, the compactness of the whole accelerating system and the very short accelerating length of this all-optical accelerators. A fervent theoretical and experimental work has been done since then. An important part of the theoretical study is done by means of numerical simulations and the most widely used technique exploits PIC codes ("Particle In Cell'"). In this thesis the PIC code AlaDyn, developed by our research group considering innovative algorithms, is described. My work has been devoted to the developement of the code and the investigation of the laser driven ion acceleration for different target configurations. Two target configurations for the proton acceleration are presented together with the results of the 2D and 3D numerical investigation. One target configuration consists of a solid foil with a low density layer attached on the irradiated side. The nearly critical plasma of the foam layer allows a very high energy absorption by the target and an increase of the proton energy up to a factor 3, when compared to the ``pure'' TNSA configuration. The differences of the regime with respect to the standard TNSA are described The case of nearly critical density targets has been investigated with 3D simulations. In this case the laser travels throughout the plasma and exits on the rear side. During the propagation, the laser drills a channel and induce a magnetic vortex that expanding on the rear side of the targer is source of a very intense electric field. The protons of the plasma are strongly accelerated up to energies of 100 MeV using a 200PW laser.

Download or read book Characterization of Laser driven Proton Acceleration with Contrast enhanced Laser Pulses written by Georg Becker and published by . This book was released on 2021* with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, various novel aspects of laser-driven ion acceleration with contrast-enhanced laser pulses have been characterized. The maximum ion energies' dependence on the pulse energy and the foil thickness was investigated in a campaign at the POLARIS laser using a plasma mirror for contrast enhancement. The steepest increase of the ion energies depending on the pulse energy was measured for a 5 nm thin foil and linear polarization. Above a certain pulse energy, the onset of the foil's transparency correlated with a stop of the ion energies' increase. Consequently, additional enhancements of the temporal intensity contrast (TIC) and higher laser pulse intensities are required to exploit ion acceleration with such thin foils. The ring-like beam profile formed by protons with low kinetic energy, which originated from submicron thick plastic foils, was characterized. Simulations support the explanation that such structures are a consequence of the proton density's spatial distribution during the acceleration with the target normal sheath acceleration mechanism (TNSA). These findings deepen the understanding of ion acceleration with thin foils and may help to distinguish features of other acceleration mechanisms in the beam profile from those attributed to TNSA. In an experiment with water microdroplets, the effects of the laser's TIC and the incidence angle in the polarization plane were investigated. It was found that both parameters have a significant influence on the kinetic energy of the accelerated protons. An optical probe laser was used to observe the plasma expansion on a picosecond timescale. A correlation between the expansion and the maximum proton energy was found. The proton beam profile exhibited a reproducible net-like pattern depending on the irradiation geometry as well. The results show that the use of microdroplets irradiated with frequency-doubled laser pulses and optically probed gives new insights into laser-plasma interaction.

Download or read book Laser Ion Acceleration from the Interaction of Ultra Intense Laser Pulse with Thi Foils written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The discovery that ultra-intense laser pulses (I> 10[sup 18] W/cm[sup 2]) can produce short pulse, high energy proton beams has renewed interest in the fundamental mechanisms that govern particle acceleration from laser-solid interactions. Experiments have shown that protons present as hydrocarbon contaminants on laser targets can be accelerated up to energies> 50 MeV. Different theoretical models that explain the observed results have been proposed. One model describes a front-surface acceleration mechanism based on the ponderomotive potential of the laser pulse. At high intensities (I> 10[sup 18] W/cm[sup 2]), the quiver energy of an electron oscillating in the electric field of the laser pulse exceeds the electron rest mass, requiring the consideration of relativistic effects. The relativistically correct ponderomotive potential is given by U[sub p] = ([1 + I[lambda][sup 2]/1.3 x 10[sup 18]][sup 1/2] - 1) m[sub o]c[sup 2], where I[lambda][sup 2] is the irradiance in W[micro]m[sup 2]/cm[sup 2] and m[sub o]c[sup 2] is the electron rest mass. At laser irradiance of I[lambda][sup 2] [approx] 10[sup 20] W[micro]m[sup 2]/cm[sup 2], the ponderomotive potential can be of order several MeV. A few recent experiments--discussed in Chapter 3 of this thesis--consider this ponderomotive potential sufficiently strong to accelerate protons from the front surface of the target to energies up to tens of MeV. Another model, known as Target Normal Sheath Acceleration (TNSA), describes the mechanism as an electrostatic sheath on the back surface of the laser target. According to the TNSA model, relativistic hot electrons created at the laser-solid interaction penetrate the foil where a few escape to infinity. The remaining hot electrons are retained by the target potential and establish an electrostatic sheath on the back surface of the target.

Download or read book Ion Acceleration Driven by Ultra short Ultra intense Laser Pulses written by Rajendra Prasad and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Laser Ion Acceleration from Ultrathin Foils and Application to Radiobiology written by Fiona May Hanton and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Ion Acceleration from the Interaction of Ultra intense Lasers with Solid Foils written by Matthew Mark Allen and published by . This book was released on 2004 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Laser Ion Acceleration from Ultrathin Foils and Application to Radiobiology written by Fiona Hanton and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mechanism and Control of High intensity laser driven Ion Acceleration written by Teh Lin and published by . This book was released on 2005 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book On the Use of Multiple High Intensity Laser Pulses in Ion Acceleration Experiments written by Graeme Gordon Scott and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Compact laser driven ion sources have inspired cautious optimism that they may provide an alternative to conventional accelerators for existing applications, such as in medicine, or aid the realisation of new ones such as fusion energy. However, the sources must be developed, with increased conversion efficiency of laser to proton energy being high on the list of requirements. Recent reports in the literature have shown that record conversion efficiencies can be achieved with double pulse interactions, and this thesis proceeds with this theme. The double pulse operation of the plasma mirror is characterised for the first time, in terms of the post interaction far field quality, and integrated reflectivity. The main pulse reflectivity is significantly enhanced to 96% and the far field remains of high optical quality up to five picoseconds after the prepulse interaction, within the regime for conversion efficiency enhancement. These observations are explained by perturbations of the quasi-near field intensity distribution seeding nonuniformities in the plasma expansion of the plasma mirror surface. A novel plasma half cavity target geometry is investigated which utilises the high fraction of laser energy reflected from an ionised surface and refocuses it such that a double pulse interaction is attained. This new geometry is found to double the laser to proton energy conversion efficiency, compared with planar foil interactions and to modify the low energy region of the proton spectrum. For pulse separations of tens of picoseconds, a long time delay regime is identified for planar foil interactions, where a significant reduction in maximum proton energy and conversion efficiency is reversed, and return to that expected for single pulse interactions. This is explained by the main pulse interacting with bulk target expansion induced by the prepulse. Increased electron temperatures from enhanced absorption in the preplasma are found to mitigate the detrimental effects on ion acceleration, associated with rear surface density scale lengths.

Download or read book Laser Wakefield Electron Acceleration written by Karl Schmid and published by Springer Science & Business Media. This book was released on 2011-05-18 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis covers the few-cycle laser-driven acceleration of electrons in a laser-generated plasma. This process, known as laser wakefield acceleration (LWFA), relies on strongly driven plasma waves for the generation of accelerating gradients in the vicinity of several 100 GV/m, a value four orders of magnitude larger than that attainable by conventional accelerators. This thesis demonstrates that laser pulses with an ultrashort duration of 8 fs and a peak power of 6 TW allow the production of electron energies up to 50 MeV via LWFA. The special properties of laser accelerated electron pulses, namely the ultrashort pulse duration, the high brilliance, and the high charge density, open up new possibilities in many applications of these electron beams.

Download or read book Ion Acceleration by Ultra intense Laser Pulse Interacting with Double layer Near critical Density Plasma written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advances in Shortpulse Laser driven Ion Acceleration written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Relativistic Laser Plasma Dynamics with Ultrathin Foils written by Julia Bränzel and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: