In order to reach the maximum energy gain and high-quality beam with small energy spread, the dephasing length should be less than the pump depletion length due to pulse-front erosion, i. The abovementioned injection schemes provide us with high-quality electron beam injectors for a front end of multi-staged high-energy accelerators such as a multi-GeV laser plasma accelerator for compact X-ray FELs, 20 , 21 , 58 a GeV large-scale laser plasma acceleration experiment, 57 TeV-range laser plasma colliders.
In laser wakefield acceleration, an accelerated electron beam induces its own wakefield and cancels the laser-driven wakefield. Thus, a loaded charge is calculated as. Here we overview the experiments on laser wakefield acceleration from methodological point of view in optical guiding, characterized as self-guiding and channel-guiding.
Most of the laser pulse resides inside the electron density depression and thereby can be guided. Hence, the very front of the laser pulse continuously erodes away due to diffraction so that the degree of guiding the remaining pulse is varying along the laser pulse. As r L is reduced from the matched spot size, diffraction loss tends to increase. Beyond the pump depletion limit, the pulse is so severely etched that it is no longer intense enough to excite a wake and thereby no longer guided.
For guiding intense laser pulses over many Rayleigh lengths without diffraction that limits the acceleration distance to a few mm in a uniform plasma, a preformed plasma density channel with a parabolic radial distribution has been developed. Plasma waveguides for guiding ultraintense short laser pulses in plasmas are produced by a number of methods, including laser-induced hydrodynamic expansion, 63 — 65 pulsed discharges of an ablative capillary 66 — 69 or a gas-filled capillary.
Laser-induced plasma channels need a fast ignition by a few ns prior to propagating a main laser pulse, while a slow pulsed discharge capillary needs a jitter free trigger within a few ns. To guide ultraintense laser pulses, plasma channels must be produced in fully ionized gases with low atomic number Z such as hydrogen or helium.
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Not fully ionized particles will be further ionized by the laser, disturbing the electron density profile. Plasma density channels stabilize propagation of relativistically intense laser pulses under the matched condition, preventing laser-plasma nonlinear instabilities, such as filamentation and hosing that often occur in the self-guiding. For the last two decades, a number of laser-plasma accelerator experiments have been carried out under various conditions. Comparing these data with theoretical laser wakefield acceleration models, it may be useful to find a correct scaling law capable of predicting energy gain, accelerated electron charge and the required laser-plasma conditions.
Beam energy scaling of GeV-class laser wakefield accelerators: a The comparison of measured electron beam energies with the energy scaling formula Eq. For applications of unique particle beam and radiation sources, one needs proper formulas for designing laser plasma accelerators to meet the requirement of electron beam parameters such as energy and charge, complying with the scaling law obtained from laser plasma accelerator experiments.
In the square bracket on the right hand side, the first term represents free-space propagation, the second and third terms correspond to relativistic self-focusing and ponderomotive channeling, respectively. The analyses of the wave equation with the standard paraxial form provide the matched spot radius r L under the condition for the beam propagating with a constant spot size, i. For a given energy E b GeV and charge Q b pC, the parameters of self-guided laser wakefield accelerators can be designed as follows.
First, using Eq. Then, the operating plasma density is determined from Eq. The accelerator length equal to the dephasing length, i. Since the dephasing length should be less than the pump depletion length, i. This technology called as extreme ultraviolet lithography EUVL is capable of providing resolution below 30 nm that had been impossible with conventional optical lithography utilizing deep ultraviolet DUV light sources with wavelengths of nm or nm. The current technologies for generating high power EUV radiation at The current LPP radiation sources have a serious obstacle on the way to a high volume manufacturing HVM source such as small efficiency of the radiation source, a limited set of discrete wavelengths and the mitigation of the plasma debris required for the protection of the EUV optics.
Free-Electron Laser FEL based radiation sources have evident advantages in wavelength tunability, high efficiency and high output power, compared to current LPP radiation sources. The problem of debris mitigation does not exist at all. A proposed FEL 81 producing a kW-level average output power of EUV radiation utilizes high-energy electron beams of the order of 1 GeV generated from a radio-frequency-based linear accelerator RF linac. The alternating magnetic fields of the undulator force relativistic electrons in a bunch to emit EUV radiation coherently on a sinusoidal trajectory due to the microbunching process, called as self-amplified spontaneous emission SASE FEL.
The overall size of a RF linac-driven FEL-based EUV light source may require a m long facility for a linac-based light source or a m long, 60 m wide area for a recirculator-based light source. The costs for construction and operation of such facility may turn out incredibly so large as to hinder the FEL-based EUV light sources from industrial realization of the next generation lithography technology.
A saturation length L sat required to saturate the amplification can be expressed as. The input P in and saturated power P sat are related to an electron beam power P b according to. A high-quality Gamma-beam generated from inverse Compton scattering off relativistic electron beams interacting with an intense laser pulse arouses interest in photonuclear physics and nuclear astrophysics research, characterization of nuclear materials or radioactive waste and so on.
Here, we present a table-top all-optical laser plasma accelerator-based Gamma beam source comprising a high power laser system with synchronous dual outputs, a GeV-class laser plasma accelerator, and a scatter optics whereby the laser pulse is focused onto the electron beam to generate a Gamma-beam via inverse Compton scattering with photon energy of 2—20 MeV. In the laboratory frame, the differential cross section of Compton scattering 85 is given by. All photons in this energy range are scattered to the forward direction within a half-cone angle.
Thus, the total Gamma-beam flux is given by.
When a nucleus absorbs photons equal to the excitation energy, the nucleus is excited to the definite state due to resonant excitation, instantaneously followed by decaying mainly to a lower state with a re-emission of the radiation equivalent to the absorbed energy. Since this resonant property of NRF is in unique contrast to other nuclear absorption phenomena such as photonuclear reactions and the giant dipole resonance, involving the continuum states of nuclei with broad absorption spectra, the NRF interrogation is capable of characterizing a nucleus in the nuclear structure and its excited states in terms of their energy, lifetime, angular momentum, and parity.
The absorption cross section for a nucleus in the state i to capture a photon and be directly excited to the state j , taking into account the Doppler broadening due to the thermal motion of the nucleus at the resonance, is given by The all-optical laser plasma accelerator-based Gamma-beam source at photon energy of 2. Using the design formulas Eqs. Here the values in brackets correspond to the performance of the Gamma-beam source at the operation of 1 kHz. There exist neutral resonance particles coupling to two photons at the different energy scales over three orders of magnitude.
Generally speaking, testing photon-photon interactions provides us with crucial information on particle physics and cosmology. For generating the incident photons with energy of 0. The luminosity of head-on colliding two-photon bunches with three dimensional Gaussian distributions can be given by. Provided the IP is separated at a short distance d , e. The distance d is set to be a length that is required for spatially separating counter-propagating electron bunches in the strong magnetic field placed at the IP, e.
An electron beam from LPA is collimated by a beam focusing system comprising a set of permanent-magnet-based quadrupoles. This transport system can be designed so as to have the transverse r. Assuming that the laser pulse length is set to a Rayleigh length, i.
This application relates to a new external-beam radiation therapy system using very-high-energy VHE electron beams with energy of 50— MeV, generated by a centimeter-scale laser plasma accelerator built in a robotic system. Most types of external-beam radiation therapy are delivered outside the body in the form of photon beams with energies of 6—20 MV from a machine called a medical linear accelerator driven by radio frequency RF power amplifiers in conjunction with modern radiation therapy technologies for effective shaping of 3-dimensional dose distributions and spatially accurate dose delivery with imaging verification such as 3-dimensional conformal radiation therapy 3D-CRT , intensity-modulated radiation therapy IMRT , image guided radiation therapy IGRT , stereotactic body radiation therapy SBRT and hadron therapy.
However, the limited penetration depth and low quality of the transverse penumbra at such electron beams delivered from the present RF linear accelerators prevent the implementation of advanced modalities in current cancer treatments. These drawbacks can be overcome if electron energy is increased above 50 MeV, more specifically to the range of 50— MeV.
The drive laser pulse is guided through a vacuum transport optics and focused onto the laser plasma accelerator, both of which are installed in the robotic gantry. The requirement of electron beam charge is determined by the radiation therapy treatment plan, for example, a 10 cc lung tumor treatment with MeV electrons to a dose of 10 Gy in 1 second.
This treatment requires that a 1 nC charge of MeV electrons should be deposited over a 10 cc tumour volume in 1 second. The laser plasma accelerator for delivering VHE electron beams with charge of 10 pC and variable energies in the range from 50 MeV to MeV can be designed by exploiting the formulas Eqs. The inset shows a laser plasma accelerator comprising an injector and accelerator gas cells.
The ultrashort intense laser pulse is focused by a spherical mirror or off-axis parabolic mirror on the entrance of a two-stage gas cell, of which the first cell referred to an injector is filled with a mixed gas, e. The gases are fed through a gas flow control system to the two-stage gas cell separately at the different pressures. According to the abovementioned mechanism, in the injector of the gas cell, the laser pulse excites large-amplitude plasma wakefields, of which an accelerating electric field can trap plasma electrons exclusively out of the inner shell electrons and accelerate them owing to ionization-induced injection.
A collimated electron beam from the laser plasma accelerator is provided to the target in the patient by the beam focusing system comprising permanent quadrupole magnets. Recently there is a growing interest in rapid progress on laser-driven plasma-based accelerators by exploiting petawatt-class lasers, whereby high-quality electron beams can be accelerated to multi-GeV energies in a centimeter-scale plasma thanks to laser wakefield acceleration mechanism, as reported so far, e. The state-of-the-art of PW-class lasers allows us to study the feasibility of laser plasma accelerators toward GeV in a full scale experiment.
The experiments are proposed for implementing the demonstration of a GeV electron beam acceleration by means of a laser plasma accelerator driven with a multi-PW laser capable of delivering 3. Such a large-scale laser plasma accelerator comprises a gas jet or a short gas cell, which acts as an injector, followed by a long, uniform, low-density plasma or preformed plasma channel plasma waveguide , which acts as the accelerating medium. Accelerated beams are detected and analyzed using diagnostic system composed of high-resolution spectrometers and beam imaging detectors. According to the design formulas Eqs.
Electron beams can be produced and accelerated in the injector stage driven by the same laser pulse as that in the accelerator stage, relying on the self-injection mechanism such as an expanding bubble self-injection mechanism, 49 or the ionization-induced injection mechanism 54 — 56 with a short mixed gas cell. Preformed plasma density channels for guiding ultra-intense short laser pulses are produced by a number of methods, including laser-induced hydrodynamic expansion, pulsed discharges of an ablative capillary or a gas-filled capillary.
An alternative method may be a hollow dielectric capillary tube filled with neutral gas for guiding intense short laser pulses over several meters. Since laser is guided by Fresnel reflection at the inner capillary wall, this method relies on neither laser power nor plasma density. A design of the neutral gas-filled plasma waveguide for GeV laser plasma accelerators has been presented in Ref.
Electron beams from a laser plasma accelerator comprising an injector and a plasma waveguide are deflected through a spectrometer dipole magnet, and detected on imaging plates placed at several positions apart from the spectrometer magnet so that beam energy can be evaluated precisely by reconstructing a track of the electron beam.
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In order to hold and align the injector, the plasma waveguide and diagnostic system in the centre of the vacuum target chamber, a structure, called as an inserter, with the function of precisely positioning the experimental setup will be built. A schematic view of the setup for GeV ascent experiments at the multi-PW laser facility. A multi-PW laser blue beamline is focused on an injector plasma target placed at the center of the vacuum chamber, where a produced electron beam is accelerated by laser wakefields generated in a plasma waveguide yellow beamline.
We have overviewed electron acceleration on the view of strong laser field-electron interaction in vacuum and plasma, whereby the acceleration mechanism is often referred to as the vacuum- or plasma-based accelerator. Nowadays a breakthrough concept of laser acceleration 17 has led to great progress on laser-driven plasma-based accelerators combined with ultra-intense lasers that had emerged from chirped pulse amplification technique.
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As shown in Fig. Here some of examples have been illustrated by designing the embodiment so as to meet requirements in the practical application, based on the design formulas for laser plasma accelerators, which are deduced from a recent understanding of laser wakefield acceleration and the experimental results. The laser plasma accelerator-based EUV-FEL 84 is a long outstanding objective that exemplifies advantageous properties of laser plasma accelerators over the conventional accelerator-based system in compactness and high-brightness.
The all-optical gamma beam source 84 based on GeV-class laser plasma accelerators is deemed to be a new promising tool for particle and nuclear physics research, 89 — 94 the interrogation of nuclear materials 86 and the assay of radioactive wastes, 87 , 88 of which system is planned by exploiting a combination between a conventional electron accelerator and a high-repetition rate laser. As an example of medical applications, the VHE electron beam therapy system driven by a laser plasma accelerator might become a reality in the earliest future because of great interest for medical science.
Recently the vacuum laser acceleration attracts renewed interest in the all-optical concept of the quest for extremely high field-electron interaction. The author would like to thank Prof. The author would like to express thanks to Prof. Zhang, Prof.
Sheng, Prof. Chen and Prof. Yuan at Shanghai Jiao Tong University in appreciation of their support and long-standing collaboration on applications of laser plasma accelerators, and thanks to Prof. Xu, Prof. Li, Prof. Liu and Prof.
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Nam, Center for Relativistic Laser Science, Institute for Basic Science, in appreciation of the former and current collaboration on PW laser-driven electron acceleration. The author is also grateful to Prof. Homma, Hiroshima University, for his stimulative contribution to laser-plasma based photon colliders. Kazuhisa Nakajima was born in Nagano Prefecture in He received Ph. Tadao Fujii. Maury Tigner at Cornell University, U. Thereafter his experimental research over 20 years was mainly carried out by the collaboration with high power laser facilities at China, Korea and India as well as Japan.
In addition to experimental activities, since he conducted a number of lectures and student supervisions on laser plasma acceleration for graduate course at The Graduate University of Advanced Study, The University of Tokyo, Kyoto University, Shanghai Jiao Tong University, Shanghai Institute of Optics and Fine Mechanics and so on. Since he leads the low-density laser plasma group for the research on laser plasma electron acceleration at the Center for Relativistic Laser Science, Institute for Basic Science, Republic of Korea.
National Center for Biotechnology Information , U. Author information Article notes Copyright and License information Disclaimer. Received Mar 7; Accepted Apr This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract To date active research on laser-driven plasma-based accelerators have achieved great progress on production of high-energy, high-quality electron and photon beams in a compact scale. Keywords: laser plasma accelerators, relativistic laser plasma interaction, laser wakefield acceleration, electron and photon beams. Introduction The exploration searching for the origin of matter and universe requires producing the highest energy state to investigate nature on the smallest scale, which is composed of the fundamental particles and forces.
Nonlinear laser wakefields in the bubble regime Wakefield excitation by relativistic laser pulses in plasma. Open in a separate window. Figure 1.
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Injection of electrons into the plasma bubble. Acceleration of electrons in the plasma bubble. Beam loading of electrons. Laser wakefield acceleration experiments. Self-guided laser wakefield accelerators. Channel-guided laser wakefield accelerators. Scaling of laser wakefield accelerators. The human-like nature of neuromorphic systems, therefore, could place them in the categories of robots many EU citizens would like to see banned in the future.
As neuromorphic systems have become increasingly advanced, some scholars have advocated for granting personhood rights to these systems. If the brain is what grants humans their personhood, to what extent does a neuromorphic system have to mimic the human brain to be granted personhood rights? Critics of technology development in the Human Brain Project , which aims to advance brain-inspired computing, have argued that advancement in neuromorphic computing could lead to machine consciousness or personhood.
However, skeptics of this position have argued that there is no way to apply the electronic personhood, the concept of personhood that would apply to neuromorphic technology, legally. There is significant legal debate around property rights and artificial intelligence. In Acohs Pty Ltd v.
Ucorp Pty Ltd , Justice Christopher Jessup of the Federal Court of Australia found that the source code for Material Safety Data Sheets could not be copyrighted as it was generated by a software interface rather than a human author. Neuromemristive systems are a subclass of neuromorphic computing systems that focus on the use of memristors to implement neuroplasticity.
While neuromorphic engineering focuses on mimicking biological behavior, neuromemristive systems focus on abstraction. There exist several neuron inspired threshold logic functions  implemented with memristors that have applications in high level pattern recognition applications. Some of the applications reported recently include speech recognition ,  face recognition  and object recognition. For ideal passive memristive circuits, it is possible to derive a system of differential equations for evolution of the internal memory of the circuit: .
This equation thus requires adding extra constraints on the memory values in order to be reliable.
From Wikipedia, the free encyclopedia. Integrated circuit technology. Communications of the ACM. Bibcode : Nanot.. Proceedings of the IEEE. January 1, PP 99 : — Bibcode : arXivM. August 1, Applied Computational Intelligence and Soft Computing.
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May A field programmable neural array. Retrieved December 4, Frontiers in Neuroscience. Nature Materials. Bibcode : NatMa.. Mitchell Bibcode : Natur. Archived from the original on March 2, Retrieved February 22, January 29, Bibcode : Sci January 16, IEEE Micro. Retrieved August 17, European Commission.
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