Laser-driven Ion Beams Research Articles

Fast ion ignition with ultra-intense laser pulses

Fast ignition by laser-driven ion beams benefits from the strong collisional interaction of energetic ions with the imploded fuel. However, conditions for an efficient transformation of the laser pulse energy into ion kinetic energy and for the transport of these ions from the acceleration region to the fusion pellet core without significant temporal and angular spread have to be clarified. The laser ponderomotive force may provide efficient ion acceleration in bulk dense targets such as a precompressed DT capsule and evacuate a channel for further laser beam propagation. The main characteristics of ponderomotive ion acceleration and channel formation inferred from analytical theory and confirmed by particle-in-cell simulations are applied for the design of a new scheme of ion fast ignition. Contrary to schemes based on the mechanism of target normal sheath ion acceleration, at least two laser pulses are used in our proposal. The first pulse (or a sequence of several pulses) creates a channel with a diameter of ∼20 µm through the plasma corona up to a fuel density of ∼1 g cm−3. The second pulse with a higher intensity of ∼1022 W cm−2 accelerates the deuterium and tritium ions at the head of this channel to energies 5–25 MeV on a time scale less than 1–3 ps. The overall ignition energy in this proposal is relatively high, ≳100 kJ, but no additional target arrangements will be required. This feature makes the scheme attractive for a high repetition rate operation.

Toward integrated laser-driven ion accelerator systems at the photo-medical research center in Japan

Goals and early progress at the Photo-Medical Research Center are summarized. Laser-driven ion beam radiotherapy can require compact repetition-rated laser systems with peak powers approaching the PW level. Laser development at PMRC is outlined. Our parallel experimental and simulation efforts aimed at the development of a prototype ion beamline as an integrated laser-driven ion accelerator system are presented. In addition some of our first medical and radiobiological experimental investigations, proton-induced double strand breaking in human cancer cells and simulations of optimum dose distributions for ocular melanoma are discussed. Recommended components of a balanced and comprehensive PMRC agenda are given.

Application of laser-accelerated protons to the demonstration of DNA double-strand breaks in human cancer cells

We report the demonstrated irradiation effect of laser-accelerated protons on human cancer cells. In vitro (living) A549 cells are irradiated with quasimonoenergetic proton bunches of 0.8–2.4 MeV with a single bunch duration of 15 ns. Irradiation with the proton dose of 20 Gy results in a distinct formation of γ-H2AX foci as an indicator of DNA double-strand breaks generated in the cancer cells. This is a pioneering result that points to future investigations of the radiobiological effects of laser-driven ion beams. Unique high-current and short-bunch features make laser-driven proton bunches an excitation source for time-resolved determination of radical yields.

Progress and prospects of ion-driven fast ignition

Fusion fast ignition (FI) initiated by laser-driven ion beams is a promising concept examined in this paper. FI based on a beam of quasi-monoenergetic ions (protons or heavier ions) has the advantage of a more localized energy deposition, which minimizes the required total beam energy, bringing it close to the ≈10 kJ minimum required for fuel densities ∼500 g cm−3. High-current, laser-driven ion beams are most promising for this purpose. Because they are born neutralized in picosecond timescales, these beams may deliver the power density required to ignite the compressed DT fuel, ∼10 kJ/10 ps into a spot 20 µm in diameter. Our modelling of ion-based FI include high fusion gain targets and a proof of principle experiment. That modelling indicates the concept is feasible, and provides confirmation of our understanding of the operative physics, a firmer foundation for the requirements, and a better understanding of the optimization trade space. An important benefit of the scheme is that such a high-energy, quasi-monoenergetic ignitor beam could be generated far from the capsule (⩾1 cm away), eliminating the need for a reentrant cone in the capsule to protect the ion-generation laser target, a tremendous practical benefit. This paper summarizes the ion-based FI concept, the integrated ion-driven FI modelling, the requirements on the ignitor beam derived from that modelling, and the progress in developing a suitable laser-driven ignitor ion beam.

Laser-driven proton acceleration: source optimization and radiographic applications

Ion acceleration from solid targets irradiated by high-intensity pulses is a burgeoning area of research, currently attracting large interest worldwide. The properties of laser-driven ion beams (high brightness and laminarity, high-energy cut-off, ultrashort burst duration) are, in several respects, markedly different from those of ‘conventional’ accelerator beams. In view of these properties, laser-driven ion beams have the potential to be employed in a number of innovative applications in the scientific, technological and medical areas. The scope of this paper is to briefly review the state of the art in this area and discuss in this context some recent results obtained by our group and collaborators, aimed at studying the acceleration mechanism, optimizing the source properties and applying the beams as a diagnostic tool in scientific experiments. An application that has already produced important results is the use of laser-accelerated protons as a particle probe for the detection of electric and magnetic fields in plasmas. Examples of these results will be presented and discussed.

Progress on ion based fast ignition

Research at Los Alamos on fusion fast ignition (FI) [1] initiated by laser-driven ion beams heavier than protons has produced encouraging results. The minimum requirements for FI are relatively well understood [2]. Based on simple considerations and on those requirements, it is shown that FI of the compressed DT fuel using laser-driven heavy ion beams has advantages compared to laser-driven proton or electron beams, along with different risks compared to those approaches. Using a technologically convenient light-ion species such as Carbon, ∼ 100-fold fewer ions may deliver the energy necessary to ignite, simplifying target fabrication. Key requirements for success include the generation of a monoenergetic beam (energy spread ≤ ∼ 10%), a sufficiently high ion kinetic energy (∼ 450 MeV for C), and a sufficiently high conversion efficiency of laser to beam energy. An important benefit of this scheme is that such a high-energy, quasi-monoenergetic beam may be generated far from the capsule (∼ 1 cm away), eliminating the need for a reentrant cone in the capsule, a tremendous practical benefit. This paper summarizes our progress in meeting those requirements, and the results of an integrated 2D design for a proof of principle FI experiment based on this concept.

Laser-driven proton oncology — a unique new cancer therapy?

In 2000, the University of Strathclyde, collaborating with the Rutherford Appleton Laboratory, organized the first workshop dealing with the potential of high-power laser technology in medicine. Two areas of potential were identified: firstly the production of positron emission tomography (PET) isotopes; and secondly, the potential for laser-accelerated proton and heavy ion beams for therapy. The attendees, mainly clinicians and radiation physicists, emphasised that the laser community should concentrate on developing laser and target technology for therapy rather than isotope production because of the potential advantages over conventional accelerator technology for that purpose. On the 30 March 2007, the universities of Strathclyde and Paisley organized a follow-up meeting to identify the progress made in laser-driven proton and ion beam technology with applications leading to proton and ion beam therapy for deep-seated tumours. The meeting was supported by the Scottish Universities Physics Alliance (SUPA)--an organization set up in Scotland to bring together all of the physics departments collaborating with life scientists to work on ground-breaking new science which no single university could attempt. This is a summary of the meeting.

Focusing of high-current laser-driven ion beams

Using a two-dimensional relativistic hydrodynamic code, it is shown that a dense high-current ion beam driven by a short-pulse laser can be effectively focused by curving the target front surface. The focused beam parameters essentially depend on the density gradient scale length of the preplasma Ln and the surface curvature radius RT. When Ln⩽0.5λL (λL is the laser wavelength) and RT is comparable with the laser beam aperture dL, a significant fraction of the accelerated ions is focused on a spot much smaller than dL, which results in a considerable increase in the ion fluence and current density. Using high-contrast multipetawatt picosecond laser pulses of relativistic intensity (∼1020W∕cm2), focused ion (proton) current densities approaching those required for fast ignition of DT fuel seem to be feasible.

Laser-accelerated high-energy ions: state of-the-art and applications

The acceleration of high-energy ion beams (up to several tens of MeV per nucleon) following the interaction of short (t < 1ps) and intense (Iλ2> 1018 W cm−2 μm−2) laser pulses with solid targets has been one of the most important results of recent laser-plasma research. The acceleration is driven by relativistic electrons, which acquire energy directly from the laser pulse and set up extremely large (∼TV/m) space charge fields at the target interfaces. In view of a number of advantageous properties, laser-driven ion beams can be employed in a number of innovative applications in the scientific, technological and medical areas. Among these, their possible use in hadrontherapy, with potential reduction of facility costs, has been proposed recently. This paper will briefly review the current state-of-the-art in laser-driven proton/ion source development, and will discuss the progress needed in order to implement some of the above applications. Recent results relating to the optimization of beam energy, spectrum and collimation will be presented.

LASER-ACCELERATED PROTONS: PERSPECTIVES FOR CONTROL/OPTIMIZATION OF BEAM PROPERTIES

The acceleration of high-energy ion beams (up to several tens of MeV per nucleon) following the interaction of short ( t &lt; 1ps ) and intense (Iλ2 &gt; 1018W cm-2μm2) laser pulses with solid targets has been one of the most active areas of research in the last few years. The exceptional properties of these beams (high brightness and high spectral cutoff, high directionality and laminarity, short burst duration) distinguish them from those of the lower energy ions accelerated in earlier experiments at moderate laser intensities. In view of these properties, laser-driven ion beams can be employed in a number of groundbreaking applications in the scientific, technological and medical areas. This paper reviews the current state-of-the-art, highlights recent developments and indicate future directions of this research area.

Laser-driven generation of fast particles

AbstractThe great progress in high-peak-power laser technology has resulted recently in the production of ps and subps laser pulses of PW powers and relativistic intensities (up to 1021 W/cm2) and has laid the basis for the construction of multi-PW lasers generating ultrarelativistic laser intensities (above 1023 W/cm2). The laser pulses of such extreme parameters make it possible to produce highly collimated beams of electrons or ions of MeV to GeV energies, of short time durations (down to subps) and of enormous currents and current densities, unattainable with conventional accelerators. Such particle beams have a potential to be applied in numerous fields of scientific research as well as in medicine and technology development. This paper is focused on laser-driven generation of fast ion beams and reviews recent progress in this field. The basic concepts and achievements in the generation of intense beams of protons, light ions, and multiply charged heavy ions are presented. Prospects for applications of laser-driven ion beams are briefly discussed.

Laser accelerated heavy particles – Tailoring of ion beams on a nano-scale

Abstract Intense lasers of femtosecond pulse duration are known to be drivers for intense electron and ion beams. Those beams, generated at laser intensities exceeding 10 19 W/cm 2 , are known to have unique characteristics and are therefore a subject of intense research world wide. Recently, the parameters of laser driven ion beams have been measured using new methods and it has been demonstrated, that beam patterns on a nanometer scale can be generated and propagated over long distances. We report on recent results and prospects for future application with special respect to further laser developments.

Fast Ion Generation by High-Intensity Laser Irradiation of Solid Targets and Applications

The acceleration of high-energy ion beams (up to several tens of mega-electron-volts per nucleon) following the interaction of short (t < 1 ps) and intense (I λ 2 > 1018 W˙cm-2˙μm-2) laser pulses with solid targets has been one of the most active areas of research in the last few years. The exceptional properties of these beams (high brightness and high spectral cutoff, high directionality and laminarity, and short burst duration) distinguish them from the lower-energy ions accelerated in earlier experiments at moderate laser intensities. In view of these properties, laser-driven ion beams can be employed in a number of groundbreaking applications in the scientific, technological, and medical areas. This paper reviews the main experimental results obtained in this area in recent years, the properties of the accelerated beams, the relevant theoretical and computational models, and the main applications that have been implemented or proposed.

New Detection Device for Thomson Parabola Spectrometer for Diagnosis of the Laser-Plasma Ion Beam

A new detection device for evaluating the ion energy distributions of a laser-plasma ion source is demonstrated. The Imaging Plate (IP) with no protective layer as ion detector device for the Thomson Parabola spectrometer is used. The Imaging Plate Thomson Parabola spectrometer (IPTPS) is applicable for the analysis of the energy distribution of the laser-driven ion beam using an opto-electric digitizing technique.

Laser-ablation treatment of short-pulse laser targets: Toward an experimental program on energetic-ion interactions with dense plasmas

This new project relies on the capabilities collocated at LosAlamos in theTrident laser facility of long-pulse laser drive, for laser-plasma formation, and high-intensity short-pulse laser drive, for relativistic laser-matter interaction experiments. Specifically, we are working to understand quantitatively the physics that underlie the generation of laserdriven MeV0nucleon ion beams, in order to extend these capabilities over a range of ion species, to optimize beam generation, and to control those beams. Furthermore, we intend to study the interaction of these novel laser-driven ion beams with dense plasmas, which are relevant to important topics such as the fast-ignition method of inertial confinement fusion ~ICF!, weapons physics, and planetary physics. We are interested in irradiating metallic foils with the Trident short-pulse laser to generate medium to heavy ion beams ~Z 20–45! with high efficiency. At present, target-surface impurities seem to be the main obstacle to reliable and efficient acceleration of metallic ions in the foil substrate.Inordertoquantifytheproblem,measurementsofsurfaceimpuritiesontypicalmetallic-foillasertargetswere made. To eliminate these impurities, we resorted to novel target-treatment techniques such as Joule-heating and laser-ablation, using a long-pulse laser intensity of ;10 10 W0cm 2 . Our progress on this promising effort is presented in this paper, along with a summary of the overall project.

Energetic ions generated by laser pulses: A detailed study on target properties

We present the results of a detailed study on the acceleration of intense ion beams by relativistic laser plasmas. The experiments were performed at the 100 TW laser at the Laboratoire pour L'Utilisation des Lasers Intenses. We investigated the dependence of the ion beams on the target conditions based on theoretical predictions by the target normal sheath acceleration mechanism. A strong dependence of the ion beam parameters on the conditions on the target rear surface was found. We succeeded in shaping the ion beam by the appropriate tailoring of the target geometry and we performed a characterization of the ion beam quality. The production of a heavy ion beam could be achieved by suppressing the amount of protons at the target surfaces. Finally, we demonstrated the use of short pulse laser driven ion beams for radiography of thick samples with high resolution.