Antonio ting | University of Maryland, College Park (original) (raw)

Papers by Antonio ting

Physical Review Letters, 1984

Les etats d'equilibre statistique sont decrits par les solutions d'une equation different... more Les etats d'equilibre statistique sont decrits par les solutions d'une equation differentielle partielle elliptique non lineaire l'equation sin h de Poisson ⊇ 2 φ+λ 2 sin h φ=0 avec limite rectangulaire conductrice. On presente les premieres solutions analytiques generales du probleme aux valeurs limites non lineaires. La construction explicite des solutions montre une superposition non lineaire parmi les solutions

IEEE Conference Record - Abstracts. 2005 IEEE International Conference on Plasma Science, 2005

ABSTRACT Summary form only given. Laser driven accelerators such as the laser wakefield accelerat... more ABSTRACT Summary form only given. Laser driven accelerators such as the laser wakefield accelerator (LWFA) have tremendous advantages over conventional radio-frequency accelerators because of the ultra-high acceleration gradients (>100 GV/m) provided by the large amplitude relativistic plasma waves that are excited by the intense ultra-short laser pulse. These ultra-high gradients were demonstrated in the last decade using a variation of the LWFA called the self-modulated LWFA (SM-LWFA). However, the high energy electrons generated in these schemes have an energy distribution that is essentially thermal in nature. The large energy spread is a consequence of the uncontrolled self-trapping and acceleration of background plasma electrons. Recent experimental results have made breakthroughs both in the first demonstration of controlled acceleration of optically injected electrons at the Naval Research Laboratory (NRL) and the first production of quasi-monoenergetic (~100 MeV) beams at several international institutes. An incorporation of the optical injection and an extended acceleration in a plasma channel can lead to stable and high-quality electron beams in the multi-GeV regime in a single stage. Staging of GeV LWFA's to generate substantially higher energy electrons is also being actively considered. The LWFA experiments at NRL have demonstrated high energy electron production in the optical injection scheme of high-density laser ionization and ponderomotive acceleration (HD-LIPA) and the first two-staged optically injected LWFA. Acceleration of optically injected electrons to >10 MeV was observed indicating an acceleration gradient of -10 GeV/m for the 1 mm acceleration distance. Further experiment to extend the acceleration distance to many centimeters for the demonstration of well controlled injection and acceleration to very high energies is in progress. The details of these injection-acceleration experiments will be presented

The seventh workshop on advanced accelerator concepts, 1997

ABSTRACT

AIP Conference Proceedings, 2017

Proton acceleration by collisionless shocks using a supersonic H 2 gas-jet target and highpower i... more Proton acceleration by collisionless shocks using a supersonic H 2 gas-jet target and highpower infrared laser pulses

Applied Physics Letters, 2018

A scheme to radiate a highly collimated c-ray pulse is proposed through the interaction between a... more A scheme to radiate a highly collimated c-ray pulse is proposed through the interaction between an ultra-intense laser pulse and a narrow tube target. The c-ray pulse, with high conversion efficiency, can be generated as a result of electron acceleration in a longitudinal electric field. In a Particle-in-Cell simulation with a 10-PW laser, 18% of the laser energy is transferred into the forward c-rays in a divergence angle less than 3. It is also found that such a highly collimated c-ray pulse can be produced with a large range of tube diameters and laser intensities. This scheme could be realized in experiment with the coming 10-PW class lasers in the near future.

AIP Conference Proceedings, 2004

... 2. D. Gordon et al., Phys. Rev. Lett. 80, 2133 (1998); S. Fritzler et al., Phys. Rev. Lett. 9... more ... 2. D. Gordon et al., Phys. Rev. Lett. 80, 2133 (1998); S. Fritzler et al., Phys. Rev. Lett. 92, 165006 (2004). ... 6. DF Gordon et al., in Proceedings of the 2003 Particle Accelerator Conference, edited by Joe Chew, Peter Lucas, and Sara Webber (Portland, Oregon, 2003), p. 1846. ...

Compton scattered x-rays can be generated using a configuration consisting of a single, ultra-int... more Compton scattered x-rays can be generated using a configuration consisting of a single, ultra-intense laser pulse, and a shaped gas target. The gas target incorporates a hydrodynamically formed density spike, which nonlinearly scatters the incident pump radiation, to produce a counter-propagating electromagnetic wiggler. This self-generated wiggler field Compton scatters from electrons accelerated in the laser wakefield of the pump radiation. The nonlinear scattering mechanism in the density spike is examined theoretically and numerically in order to optimize the Compton scattered radiation. It is found that narrow-band x-rays are produced by moderate intensity pump radiation incident on the quarter-critical surface of the density spike, while high fluence, broadband x-rays are produced by high intensity pump radiation reflected near the critical surface.

Applied Optics, 2016

We have constructed a 180-m-long distributed, continuously variable atmospheric turbulence genera... more We have constructed a 180-m-long distributed, continuously variable atmospheric turbulence generator to study high-power laser beam propagation. This turbulence generator operates on the principle of free convection from a heated surface placed below the entire propagation path of the beam, similar to the situation in long-distance horizontal propagation for laser communications, power beaming, or directed energy applications. The turbulence produced by this generator has been characterized through constant-temperature anemometry, as well as by the scintillation of a low-power laser beam.

Laser Acceleration of Electrons, Protons, and Ions III; and Medical Applications of Laser-Generated Beams of Particles III, 2015

ABSTRACT An intense laser pulse propagating through a near-critical density plasma is capable of ... more ABSTRACT An intense laser pulse propagating through a near-critical density plasma is capable of generating a high peak current electron beam (~100kA) by means of a laser wakefield operating in the bubble regime. This beam drives surface currents on the sheath of the cavitation that produces large azithumal magnetic fields (~100 MG) and induces an on-axis electron current. These effects lead to a Z-pinch of the ambient plasma ions. Eventually the field confining the pinch relaxes and the ions explode radially due to self-repulsive forces. If this process occurs at a sharp exit gradient, the ions acquire some forward momentum consistent with the magnetic vortex acceleration mechanism. Fully 3D simulations indicate that the highest energy ions are emitted conically with a secondary lower energy ion beam accelerated on the axis.

Controlling the gas density gradient and profile is important for electron and proton acceleratio... more Controlling the gas density gradient and profile is important for electron and proton acceleration. Using an optimized gas density profile, we have demonstrated 40 times higher electron energy compared to a Gaussian gas jet without lost of charge or stability. Propagation of a shock wave through a gas jet can modify the gas density profile and create sharp density gradients [1, 2]. Using different shock waves energies and shock originating positions, we were able to modify the plasma density profile of a ``typical'' Gaussian gas jet into a variety of profiles, from thin (foil-like) structure to elongated profiles with fast rise and slow fall. We used a plasma bubble Cherenkov diagnostic [3, 4] to optimize the acceleration process. Accelerated electron energy and charge were cross-correlated with the second harmonic diagnostic signal. The optimized gas density profile generated stable 0.5 nC of 40 MeV electrons using a 10 TW laser. The shock wave modified gas jet can be used ...

Propagtion of intense short laser pulses in plasmas is strongly affected by relativistic correcti... more Propagtion of intense short laser pulses in plasmas is strongly affected by relativistic corrections to the plasma index of refraction. If the peak laser power P0 is slightly above the critical power Pr for relativistic focusing, the center of the pulse will be focused, and the front and back will expand due to diffraction. Pondermotive expulsion of plasma electrons substantially

Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. Z39.18 Public reporting burden for this col... more Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. Z39.18 Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 5a. CONTRACT NUMBER a. REPORT 19a. NAME OF RESPONSIBLE PERSON 19b. TELEPHONE NUMBER

2006 Conference on Lasers and Electro-Optics and 2006 Quantum Electronics and Laser Science Conference, 2006

Abstract: An appropriately tailored laser pulse can propagate many meters underwater at moderate ... more Abstract: An appropriately tailored laser pulse can propagate many meters underwater at moderate intensity, then quickly converge to an intense focus at a controlled location. Optical breakdown can then generate an acoustic pulse at this location. ©2005 Optical Society of America ...

SPIE Proceedings, 2014

This paper discusses an advanced target in the loop (ATIL) system with its performance based on a... more This paper discusses an advanced target in the loop (ATIL) system with its performance based on a nonlinear phase conjugation scheme that performs rapid adjustment of the laser beam wavefront to mitigate effects associated with atmospheric turbulence along the propagation path. The ATIL method allows positional control of the laser spot (the beacon) on a remote imaged-resolved target. The size of this beacon is governed by the reciprocity of two counterpropagating beams (one towards the target and another scattered by the target) and the fidelity of the phase conjugation scheme. In this presentation we will present the results of the thorough analysis of ATIL operation, factors that affect its performance, its focusing efficiency and the comparison of laboratory experimental validation and computer simulation results.

IEEE Journal of Selected Topics in Quantum Electronics, 1999

The ionosphere plays a prominent role in the performance of critical civilian and military commun... more The ionosphere plays a prominent role in the performance of critical civilian and military communication systems. The properties of the ionosphere can be affected by Ionospheric Modification (IM). The key instrument in IM research is a powerful, ground-based, high frequency source of electromagnetic waves known as a heater. Existing heaters operate with large, fixed location antenna arrays. With a mobile heater, investigators would be able to conduct IM research at different latitudes without building a costly permanent installation. For developing a mobile heater with a much smaller antenna array, a new highly efficient megawatt-class Radio Frequency (RF) source is required to reduce the overall power demands on a fully deployable system. The concept of such a source has been described previously [Beaudoin et al., J. Electromagn. Waves Appl. 31(17), 1786–1801 (2017)]. Here, experimental results using an electron beam produced by a gridded thermionic electron gun to drive an externa...

Journal of Electromagnetic Waves and Applications, 2017

Abstract A mobile heater for ionospheric modification studies requires a new megawatt (MW) class ... more Abstract A mobile heater for ionospheric modification studies requires a new megawatt (MW) class radio frequency (RF) source operating with an antenna array 1/20 the area of the High-Frequency Active Auroral Research Program (HAARP). To deliver an effective power density comparable to HAARP, the total source power must be in the range of 16 MW, thus demanding highly efficient sources. While the development of a whole multi-megawatt system for mobile ionospheric heaters is a complex engineering problem, in the present paper we describe only the work of our group on studying main features of a prototype MW-class vacuum electronics RF source for such system. The source design we are currently pursuing assumes class D operation using a modified version of the inductive output tube. The electron beam is a thin annular beam, switched on and off by a mod-anode as opposed to a grid. The beam is then passed through a decelerating gap, and its kinetic energy is extracted using a tunable resonant circuit that presents a constant impedance in the range of 3–10 MHz. With this design the beam is almost completely decelerated at all frequencies, thus achieving high efficiency.

Physics of Plasmas, 2017

For mobile ionospheric heaters, it is necessary to develop highly efficient RF sources capable of... more For mobile ionospheric heaters, it is necessary to develop highly efficient RF sources capable of delivering radiation in the frequency range from 3 to 10 MHz with an average power at a megawatt level. A promising source, which is capable of offering these parameters, is a grid-less version of the inductive output tube (IOT), also known as a klystrode. In this paper, studies analyzing the efficiency of grid-less IOTs are described. The basic trade-offs needed to reach high efficiency are investigated. In particular, the trade-off between the peak current and the duration of the current micro-pulse is analyzed. A particle in the cell code is used to self-consistently calculate the distribution in axial and transverse momentum and in total electron energy from the cathode to the collector. The efficiency of IOTs with collectors of various configurations is examined. It is shown that the efficiency of IOTs can be in the 90% range even without using depressed collectors.

1990 Plasma Science IEEE Conference Record - Abstracts, 1990

Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of Information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. t. REPORT DATE (DD-MM-YYYY) 2. REPORT TYPE 3. DATES COVERED (From-To) 27-06-2006 Interim May-June 2006 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Incoherent Combining of High-Power Fiber Lasers for 5b. GRANT NUMBER Long-Range Directed Energy Applications 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER