Particle accelerators that use electromagnetic fields to increase a charged particle's energy have greatly advanced the development of science and industry since invention. However, the enormous cost and size of conventional radio-frequency accelerators have limited their accessibility. Here we demonstrate a mini-accelerator powered by terahertz pulses with wavelengths 100 times shorter than radio-frequency pulses. By injecting a short relativistic electron bunch to a 30-mm-long dielectric-lined waveguide and tuning the frequency of a 20-period terahertz pulse to the phase-velocity-matched value, precise and sustained acceleration for nearly 100% of the electrons is achieved with the beam energy spread essentially unchanged. Furthermore, by accurately controlling the phase of two terahertz pulses, the beam is stably accelerated successively in two dielectric waveguides with close to 100% charge coupling efficiency. Our results demonstrate stable and scalable beam acceleration in a multistage mini-accelerator and pave the way for functioning terahertz-driven high-energy accelerators.
Plasma wakefield accelerators driven by particle beams are capable of providing accelerating gradient several orders of magnitude higher than currently used radio-frequency technology, which could reduce the length of particle accelerators, with drastic influence on the development of future colliders at TeV energies and the minimization of x-ray free-electron lasers. Since inter-plasma components and distances are among the biggest contributors to the total accelerator length, the design of staged plasma accelerators is one of the most important outstanding questions in order to render this t…
Controlling external injection in laser-plasma accelerators with terahertz frequency bunch manipulation
The Cockcroft Institute（科克沃尔研究所）；Science and Technology Facilities Council（科学与技术设施委员会）；The University of Manchester（曼彻斯特大学）；University of Liverpool（利物浦大学）
Plasma accelerators driven by intense laser or particle beams provide gigavolt-per-meter accelerating fields, promising to drastically shrink particle accelerators for high-energy physics and photon science. Applications such as linear colliders and free-electron lasers (FELs) require high energy and energy efficiency, but also high stability and beam quality. The latter includes low energy spread, which can be achieved by precise beam loading of the plasma wakefield using longitudinally shaped bunches, resulting in efficient and uniform acceleration. However, the plasma wavelength, which sets…
High power ($\sim 100$ kW) industrial electron linear accelerators (linacs) are used for irradiation applications e.g., for pasteurization of food products, disinfection of medical waste, etc. We propose that high power electron beam from such an industrial linac can be first passed through an undulator to generate powerful terahertz (THz) radiation, and the spent electron beam coming out of the undulator can still be used for industrial applications. This will enhance the utilisation of a high power industrial linac. We have performed calculation of spontaneous emission in the undulator to sh…
Theoretical and experimental studies of PXR and diffracted radiation of an oscillator in crystals combined with the development of VFEL generators with photonic crystals give a promising basis for creation of X-ray and THz sources using the same table-top accelerator. Multi-modal medical facility can be developed on the basis of one dedicated table-top electron accelerator of some tens of MeV energy. Such a system could find a lot of applications in medical practice and biomedical investigations.
A vacuum autoresonance accelerator scheme for electrons, which employs terahertz radiation and currently available magnetic fields, is suggested. Based on numerical simulations, parameter values, which could make the scheme experimentally feasible, are identified and discussed.
Acceleration and manipulation of ultrashort electron bunches are the basis behind electron and X-ray devices used for ultrafast, atomic-scale imaging and spectroscopy. Using laser-generated THz drivers enables intrinsic synchronization as well as dramatic gains in field strengths, field gradients and component compactness, leading to shorter electron bunches, higher spatio-temporal resolution and smaller infrastructures. We present a segmented THz electron accelerator and manipulator (STEAM) with extended interaction lengths capable of performing multiple high-field operations on the energy an…
The cost, size and availability of electron accelerators is dominated by the achievable accelerating gradient. Conventional high-brightness radio-frequency (RF) accelerating structures operate with 30-50 MeV/m gradients. Electron accelerators driven with optical or infrared sources have demonstrated accelerating gradients orders of magnitude above that achievable with conventional RF structures. However, laser-driven wakefield accelerators require intense femtosecond sources and direct laser-driven accelerators and suffer from low bunch charge, sub-micron tolerances and sub-femtosecond timing …
The concept of large-radius multistage coaxial cyclotrons having separated orbits is described, to generate proton beams of 120-2000 MeV energy at tens of GW pulsed and hundreds of MW in continuous beam power operation. Accelerated beam losses must be less than 0.1 W/m for the intercepted average beam power linear density. The concept is inherently configured to actively compensate the longitudinal and transverse space charge expansion in beam bunches. These are based on (1) actively varying the bunch acceleration equilibrium phase while maintaining isochronism, independently for each cyclotro…
THz radiation promises breakthrough advances in compact advanced accelerators due to the high frequency and GV/m fields achievable, orders of magnitude larger than in conventional radiofrequency (RF) based accelerators. Compared to laser-driven schemes, the large phase acceptances of THz-driven accelerators are advantageous for operation with sizable charge. Despite burgeoning research, THz sources, particularly laser-based ones, cannot yet compete with the efficiency of RF amplifiers for high average current accelerators. Nevertheless, THz-based phase space manipulation is of immediate intere…
Ultrashort electron beams with narrow energy spread, high charge, and low jitter are essential for resolving phase transitions in metals, semiconductors, and molecular crystals. These semirelativistic beams, produced by phototriggered electron guns, are also injected into accelerators for x-ray light sources. The achievable resolution of these time-resolved electron diffraction or x-ray experiments has been hindered by surface field and timing jitter limitations in conventional RF guns, which thus far are <200 MV/m and >96 fs, respectively. A gun driven by optically-generated single-cycle THz …
A radioactive waste transmutation system based extensively on existing nuclear power technology is presented. By replacing the control rods with neutron sources, we could maintain good power distribution and perform long-lived waste burning in high flux subcritical reactors. The design is based on a small pressurized water reactor, fission electric cell (FEC), target-distributed accelerator (TDA) and power monitoring system with in-core gamma-ray detectors, now under development in several countries. The TDA, in which an FEC electric field compensates for lost beam energy in the target, offers…
Coherent collective amplification of terahertz microbunching seeded by laser frequency beating in relativistic electron beams
Shanghai Advanced Research Institute, Chinese Academy of Sciences（中国科学院上海高等研究院）；Extreme Light Infrastructure – Nuclear Physics (ELI-NP), Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH)（极光大设施-核物理（ELI-NP），霍里亚·胡卢贝伊国家物理与核工程研发研究所（IFIN-HH））
Longitudinally resolved measurement of energy-transfer efficiency in a plasma-wakefield accelerator
Deutsches Elektronen-Synchrotron DESY（德国电子同步加速器）；University of Strathclyde（斯特拉斯克莱德大学）；The Cockcroft Institute（科克克罗夫特研究所）；University College London（伦敦大学学院）；Universität Hamburg（汉堡大学）
The sub-luminal phase velocity of electromagnetic waves in free space is generally unobtainable, being closely linked to forbidden faster than light group velocities. The requirement of effective sub-luminal phase-velocity in laser-driven particle acceleration schemes imposes a fundamental limit on the total acceleration achievable in free-space, and necessitates the use of dielectric structures and waveguides for extending the field-particle interaction. Here we demonstrate a new travelling-source and free space propagation approach to overcoming the sub-luminal propagation limits. The approa…
Collimation systems in particle accelerators are designed to dispose of unavoidable losses safely and efficiently during beam operation. Different roles are required for different types of accelerator. The present state of the art in beam collimation is exemplified in high-intensity, high-energy superconducting hadron colliders, like the CERN Large Hadron Collider (LHC), where stored beam energies reach levels up to several orders of magnitude higher than the tiny energies required to quench cold magnets. Collimation systems are essential systems for the daily operation of these modern machine…
Dielectric structures driven by laser-generated terahertz (THz) pulses may hold the key to overcoming the technological limitations of conventional particle accelerators and with recent experimental demonstrations of acceleration, compression and streaking of low-energy (sub-100 keV) electron beams, operation at relativistic beam energies is now essential to realize the full potential of THz-driven structures. We present the first THz-driven linear acceleration of relativistic 35 MeV electron bunches, exploiting the collinear excitation of a dielectric-lined waveguide driven by the longitudina…
We present the first demonstration of THz-driven bunch compression and timing stabilization of a few-fC relativistic electron beam with kinetic energy of 2.5 MeV using quasi-single-cycle strong field THz radiation in a shorted parallel-plate structure. Compression by nearly a factor of 3 produced a 39 fs rms bunch length and a reduction in timing jitter by more than a factor of 2, to 31 fs rms, offering a significant improvement to beam performance for applications like ultrafast electron diffraction. This THz-driven technique provides a critical step towards unprecedented timing resolution in…
A method for producing narrow-band THz radiation proposes passing an ultra-relativistic beam through a metallic pipe with small periodic corrugations. We present results of a measurement of such an arrangement at Brookhaven's Accelerator Test Facility (ATF). Our pipe was copper and was 5 cm long; the aperture was cylindrically symmetric, with a 1 mm (radius) bore and a corrugation depth (peak-to-peak) of 60 um. In the experiment we measured both the effect on the beam of the structure wakefield and the spectral properties of the radiation excited by the beam. We began by injecting a relatively…
We propose a physical design of a compact all optical terahertz (THz)-driven electron source. The 300 mm accelerator beamline, powered by Joule level laser system, is easily to be integrated to tabletop scale. A dual-feed THz-driven electron gun with an exponential impedance, a tapered dielectric loaded cylindrical waveguide, THz-driven bunch compressors and permanent magnet solenoids (PMS) have been designed and optimized. Dynamics simulations show that the electron source can deliver a 19 fC, 3 MeV electron beams with a normalized transverse emittance of 0.079 π.mm.mrad. A minimum relative e…
A method for producing narrow-band THz radiation proposes passing an ultra-relativistic beam through a metallic pipe with small periodic corrugations. We present results of a measurement of such an arrangement at Brookhaven's Accelerator Test Facility (ATF). Our pipe was copper and was 5 cm long; the aperture was cylindrically symmetric, with a 1 mm (radius) bore and a corrugation depth (peak-to-peak) of 60 um. In the experiment we measured both the effect on the beam of the structure wakefield and the spectral properties of the radiation excited by the beam. We began by injecting a relatively…
High peak power, tunable, narrowband terahertz emitters are becoming sought after given their portability, efficiency, and ability to be deployed in the field for industrial, medical, and military applications. The use of accelerator systems producing THz frequencies via Cherenkov radiation, generated by passing an electron beam through a slow-wave wakefield structure, is a promising method to meet future THz requirements. To date, efforts have been dedicated to analysis and design of sources utilizing laser seeded bunched electron beam drivers with relativistic energies beyond 5 MeV. Presente…
Structure wakefield acceleration (SWFA) is one of the most promising AAC schemes in several recent strategic reports, including DOE's 2016 AAC Roadmap, report on the Advanced and Novel Accelerators for High Energy Physics Roadmap (ANAR), and report on Accelerator and Beam Physics Research Goals and Opportunities. SWFA aims to raise the gradient beyond the limits of conventional radiofrequency (RF) accelerator technology, and thus the RF to beam energy efficiency, by reducing RF breakdowns from confining the microwave energy in a short (on the order of about 10 ns) and intense pulse excited by …
University of Oslo（奥斯陆大学）；Deutsches Elektronen-Synchrotron DESY（德国电子同步加速器）；Laboratoire d’Optique Appliquée (LOA), CNRS, École Polytechnique, ENSTA , Institut Polytechnique de Paris（应用光学实验室，法国国家科学研究中心，巴黎综合理工学院，国立高等电信学院，巴黎理工学院）；SLAC National Accelerator Laboratory（斯坦福直线加速器中心）；John Adams Institute for Accelerator Science, Department of Physics , University of Oxford（牛津大学物理系约翰亚当斯加速器科学研究所）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）
The use of photonic structures in the terahertz (THz) spectral region may enable the essential characteristics of confinement, modal control, and electric field shielding for very high gradient accelerators based on wakefields in dielectrics. We report here an experimental investigation of THz wakefield modes in a 3D photonic woodpile structure. Selective control in exciting or suppressing of wakefield modes with non-zero transverse wave vector is demonstrated by using drive beams of varying transverse ellipticity. Additionally, we show that the wakefield spectrum is insensitive to the offset …
