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Stable generation of GeV-class electron beams from self-guided laser-plasma channels
Hafz, Nasr A. M.,Jeong, Tae Moon,Choi, Il Woo,Lee, Seong Ku,Pae, Ki Hong,Kulagin, Victor V.,Sung, Jae Hee,Yu, Tae Jun,Hong, Kyung-Han,Hosokai, Tomonao,Cary, John R.,Ko, Do-Kyeong,Lee, Jongmin Springer Science and Business Media LLC 2008 Nature photonics Vol.2 No.9
Nasr Hafz,C. B. Kim,G. H. Kim,김종욱,H. Suk,Jongmin Lee 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.44 No.52
We propose a novel experimental scheme for a compact and tunable X-ray source capable of producing X-ray pulses with a few tens of femtosecond duration. The method is based on the Thomson scattering of a terawatt femtosecond laser from a relativistic plasma-accelerated electron beam. We present particle-in-cell simulations for ultrashort e-beam generation from laser-wakeeld accelerator scheme utilizing a plasma density transition as a self-injector; then, we present the basic characteristics of ultrashort X-ray generation.
Laser-driven Electron Acceleration and Future Applications to Compact Light Sources
N. Hafz,T. M. Jeong,S. K. Lee,J. H. Sung,최일우,T. J. Yu,J. Lee 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.1
Laser-driven plasma accelerators are gaining much attention by the advanced accelerator community due to the potential these accelerators hold in miniaturizing future high-energy and mediumenergy machines. In the laser wakefield accelerator (LWFA), the ponderomotive force of an ultrashort high-intensity laser pulse excites a longitudinal plasma wave or bubble. Due to huge charge separation, electric fields created in the plasma bubble can be several orders of magnitude higher than those available in conventional microwave and RF-based accelerator facilities, which are limited (up to~100 MV/m) by material breakdown. Therefore, if an electron bunch is injected into the bubble in phase with its field, it will gain relativistic energies within an extremely short distance. Here, in the LWFA, we show the generation of high-quality and high-energy electron beams up to the GeV-class within a few millimeters of gas-jet plasmas irradiated by tens-of- terawatt ultrashort laser pulses. Thus, we realize approximately four orders of magnitude acceleration gradients,higher than available by conventional technology. As a practical application of the stable high-energy electron beam generation, we are planning on injecting the electron beams into a fewmeter-long conventional undulator in order to realize compact X-ray synchrotron (immediate) and Free Electron Laser (future) light sources. Stable laser-driven electron beam and radiation devices will surely open a new era in science, medicine, and technology and will benefit a larger number of users in those fields.
Laser Acceleration of Electron Beams to the GeV-class Energies in Gas Jets
Nasr A. M. Hafz,Tae Moon Jeong,Seong Ku Lee,최일우,Ki Hong Pae,Victor V. Kulagin,Jae Hee Sung,Tae Jun Yu,John R. Cary,고도경,Jongmin Lee 한국광학회 2009 Current Optics and Photonics Vol.13 No.1
In a laser-plasma wakefield accelerator, the ponderomotive force of an ultrashort high intensity laser pulse excites a longitudinal wave or plasma bubble in a way similar to the excitation of a wake wave behind a boat as it propagates on the water surface. Electric fields inside the plasma bubble can be several orders of magnitude higher than those available in conventional RF-based particle accelerator facilities which are limited by material breakdown. Therefore, if an electron bunch is properly phase-locked with the bubble’s acceleration field, it can gain relativistic energies within an extremely short distance. Here, in the bubble regime we show the generation of stable and reproducible sub GeV, and GeV-class electron beams. Supported by three-dimensional particle-in-cell simulations, our experimental results show the highest acceleration gradients produced so far. Simulations suggested that the plasma bubble elongation should be minimized in order to achieve higher electron beam energies.
최일우,김형택,Nasr Hafz,유태준,JaeHee Sung,Ku Lee,김철민,IJong Kim,Young-Chul Noh,고도경,Jongmin Lee 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.2
We have designed and constructed various experimental systems to perform interaction experimentswith a 100-TW Ti:sapphire laser and a solid or a gas target, and we have used them forproton, electron, and X-ray generations. They consist of a laser beam delivery system, a targetchamber, a laser focusing and monitoring system, a target manipulation system, and target diagnosticsystems, such as a visible emission imager and an X-ray pinhole camera. The laser beamcan be focused with a peak intensity as large as ~1021 W/cm2 and a focal spot size as small as ~4μm. The solid target is precisely positioned at the laser focus with an accuracy of 20 μm, whichis much smaller than the Rayleigh range of the focused laser beam. The target diagnostic systemsallow us to investigate the status of laser-target interactions with real-time and online operationwhen the laser and the target conditions are optimized to obtain the desired characteristics forthe proton, electron, and X-ray sources. Strong correlations between the images in the diagnosticsystems and monoenergetic electron and higher-energy proton generations are presented.
J. U. KIM,C. KIM,G. H. KIM,H. SUK,N. HAFZ 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.44 No.52
It is well known that when a laser or an intense electron beam passes through a downward density transition in a plasma, some portion of the background electrons are trapped in the laser (or electron) wakeeld and the trapped electrons are accelerated to relativistically high energies over a very short distance in the plasma. In the present study, by using a two-dimensional particle-in-cell (PIC) simulation, we suggest an experimental method for electron-beam generation in a plasma, by using the so- called T3 (table-top-terawatt) laser system and plasma interaction, which can manipulate electron trapping and acceleration across a parabolic plasma density channel. The experimental method suggested in this study is easier to produce and is more feasible for applications to laser wakeeld acceleration experiments. Moreover, we present a brief ongoing experimental research plan for using the newly developed high-power T3 laser system at the Korea Electrotechnology Research Institute (KERI).
Choi, I W,Kim, C M,Sung, J H,Kim, I J,Yu, T J,Lee, S K,Jin, Y-Y,Pae, K H,Hafz, N,Lee, J IOP Pub 2009 Measurement Science and Technology Vol.20 No.11
<P>A proton energy spectrometer system is composed of a time-of-flight spectrometer (TOFS) and a Thomson parabola spectrometer (TPS), and is used to characterize laser-accelerated protons. The TOFS detects protons with a plastic scintillator, and the TPS with a CR-39 or imaging plate (IP). The two spectrometers can operate simultaneously and give separate time-of-flight (TOF) and Thomson parabola (TP) data. We propose a method to calibrate the TOFS and IP by comparing the TOF data and the TP data taken with CR-39 and IP. The absolute response of the TOFS as a function of proton energy is calculated from the proton number distribution measured with CR-39. The sensitivity of IP to protons is obtained from the proton number distribution estimated with the calibrated TOFS. This method, based on the comparison of the simultaneously measured data, gives more reliable results when using laser-accelerated protons as a calibration source. The calibrated spectrometer system can be used to measure absolutely calibrated energy spectra for the optimization of laser-accelerated protons.</P>