Within the framework of plane-wave angular spectrum analysis of the electromagnetic field structure, a solution valid for tightly focused radially polarized few-cycle laser pulses propagating in vacuum is presented. T...Within the framework of plane-wave angular spectrum analysis of the electromagnetic field structure, a solution valid for tightly focused radially polarized few-cycle laser pulses propagating in vacuum is presented. The resulting field distribution is significantly different from that based on the paraxial approximation for pulses with either small or large beam diameters. We compare the electron accelerations obtained with the two solutions and find that the energy gain obtained with our new solution is usually much larger than that with the paraxial approximation solution.展开更多
The direct acceleration of electrons by using two linearly polarized crossed Bessel-Gaussian （BG） beams with equal frequency and amplitude in vacuum is proposed and studied. It is shown that two linearly polarized B...The direct acceleration of electrons by using two linearly polarized crossed Bessel-Gaussian （BG） beams with equal frequency and amplitude in vacuum is proposed and studied. It is shown that two linearly polarized BG beams of the same order （0 or 1） with a π-rad phase difference have a resultant non-zero longitudinal electric field on the z-axis and can be used, in principle, to accelerate electrons.展开更多
An electron beam is obtained using laser wakefield electron accelerator, and converted into a γ-ray source after undergoing bremsstrahlung radiation in a dense material. A quasi-monoenergetic structure is observed wh...An electron beam is obtained using laser wakefield electron accelerator, and converted into a γ-ray source after undergoing bremsstrahlung radiation in a dense material. A quasi-monoenergetic structure is observed when the length of the plasma channel was modified. The structure has a 58-MeV peak energy, 15- mrad （full-width at half-maximum） divergence angle, and 340-pC charge. The γ-ray source generated by this high-quality electron beam is brighter and has higher spatial and temporal resolutions than other conventional sources. A γ-ray radiography demonstrational experiment is performed. Pictures of a ball with different layers made of different materials are taken. The results show a clear structure and density resolution.展开更多
A linearly polarized Laguerre–Gaussian(LP-LG)laser beam with a twist index l=−1 has field structure that fundamentally differs from the field structure of a conventional linearly polarized Gaussian beam.Close to the ...A linearly polarized Laguerre–Gaussian(LP-LG)laser beam with a twist index l=−1 has field structure that fundamentally differs from the field structure of a conventional linearly polarized Gaussian beam.Close to the axis of the LP-LG beam,the longitudinal electric and magnetic fields dominate over the transverse components.This structure offers an attractive opportunity to accelerate electrons in vacuum.It is shown,using three-dimensional particle-in-cell simulations,that this scenario can be realized by reflecting an LP-LG laser off a plasma with a sharp density gradient.The simulations indicate that a 600 TW LP-LG laser beam effectively injects electrons into the beam during the reflection.The electrons that are injected close to the laser axis experience a prolonged longitudinal acceleration by the longitudinal laser electric field.The electrons form distinct monoenergetic bunches with a small divergence angle.The energy in the most energetic bunch is 0.29 GeV.The bunch charge is 6 pC and its duration is approximately 270 as.The divergence angle is just 0.57°(10 mrad).By using a linearly polarized rather than a circularly polarized Laguerre–Gaussian beam,our scheme makes it easier to demonstrate the electron acceleration experimentally at a high-power laser facility.展开更多
Real-time single-shot measurement of the femtosecond electron beam duration in laser wakefield accelerators is discussed for both experimental design and theoretical analysis that combines polarimetry and interferomet...Real-time single-shot measurement of the femtosecond electron beam duration in laser wakefield accelerators is discussed for both experimental design and theoretical analysis that combines polarimetry and interferometry.The probe pulse polarization is rotated by the azimuthal magnetic field of the electron beam and then introduced into a Michelson-type interferometer for self-interference. The electron beam duration is obtained from the region size of the interference fringes, which is independent of the pulse width of the probe laser. Using a larger magnification system or incident angle, the measurement resolution can be less than 1 fs.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.10734130,10935002,and 11075105)the National Basic Research Program of China (Grant No.2009GB105002)
文摘Within the framework of plane-wave angular spectrum analysis of the electromagnetic field structure, a solution valid for tightly focused radially polarized few-cycle laser pulses propagating in vacuum is presented. The resulting field distribution is significantly different from that based on the paraxial approximation for pulses with either small or large beam diameters. We compare the electron accelerations obtained with the two solutions and find that the energy gain obtained with our new solution is usually much larger than that with the paraxial approximation solution.
基金Project supported by the National Natural Science Foundation of China （Grant No 10574097）.
文摘The direct acceleration of electrons by using two linearly polarized crossed Bessel-Gaussian （BG） beams with equal frequency and amplitude in vacuum is proposed and studied. It is shown that two linearly polarized BG beams of the same order （0 or 1） with a π-rad phase difference have a resultant non-zero longitudinal electric field on the z-axis and can be used, in principle, to accelerate electrons.
基金supported by the China Acdamy of Engineering Physics Project (No. 2006Z0202)the StateKey Program of the National Natural Science of China(No. 10535030)the National Natural Science Foundation of China (No. 10975121)
文摘An electron beam is obtained using laser wakefield electron accelerator, and converted into a γ-ray source after undergoing bremsstrahlung radiation in a dense material. A quasi-monoenergetic structure is observed when the length of the plasma channel was modified. The structure has a 58-MeV peak energy, 15- mrad （full-width at half-maximum） divergence angle, and 340-pC charge. The γ-ray source generated by this high-quality electron beam is brighter and has higher spatial and temporal resolutions than other conventional sources. A γ-ray radiography demonstrational experiment is performed. Pictures of a ball with different layers made of different materials are taken. The results show a clear structure and density resolution.
基金Y.S. acknowledges the support by USTC Research Funds of the Double First-Class Initiative, Strategic Priority Research Program of CAS (Grant No. XDA25010200)CAS Project for Young Scientists in Basic Research (Grant No. YSBR060)+1 种基金Newton International Fellows Alumni follow-on fundingD.R.B. and A.A. acknowledge the support by the National Science Foundation (Grant No. PHY 1903098)。
文摘A linearly polarized Laguerre–Gaussian(LP-LG)laser beam with a twist index l=−1 has field structure that fundamentally differs from the field structure of a conventional linearly polarized Gaussian beam.Close to the axis of the LP-LG beam,the longitudinal electric and magnetic fields dominate over the transverse components.This structure offers an attractive opportunity to accelerate electrons in vacuum.It is shown,using three-dimensional particle-in-cell simulations,that this scenario can be realized by reflecting an LP-LG laser off a plasma with a sharp density gradient.The simulations indicate that a 600 TW LP-LG laser beam effectively injects electrons into the beam during the reflection.The electrons that are injected close to the laser axis experience a prolonged longitudinal acceleration by the longitudinal laser electric field.The electrons form distinct monoenergetic bunches with a small divergence angle.The energy in the most energetic bunch is 0.29 GeV.The bunch charge is 6 pC and its duration is approximately 270 as.The divergence angle is just 0.57°(10 mrad).By using a linearly polarized rather than a circularly polarized Laguerre–Gaussian beam,our scheme makes it easier to demonstrate the electron acceleration experimentally at a high-power laser facility.
基金supported by the National Natural Science Foundation of China(Nos.11127901,11425418,11505263,and 61521093)the Strategic Priority Research Program(B)(No.XDB16)+2 种基金Shanghai Sailing Program(Nos.17YF1421100 and 18YF1426000)the Youth Innovation Promotion Association CASthe State Key Laboratory Program of the Chinese Ministry of Science and Technology
文摘Real-time single-shot measurement of the femtosecond electron beam duration in laser wakefield accelerators is discussed for both experimental design and theoretical analysis that combines polarimetry and interferometry.The probe pulse polarization is rotated by the azimuthal magnetic field of the electron beam and then introduced into a Michelson-type interferometer for self-interference. The electron beam duration is obtained from the region size of the interference fringes, which is independent of the pulse width of the probe laser. Using a larger magnification system or incident angle, the measurement resolution can be less than 1 fs.
