Generation of polarized particle beams at relativistic laser intensities

The acceleration of polarized electrons,positrons,protons and ions in strong laser and plasma fields is a very attractive option for obtaining polarized beams in the multi-mega-electron volt range.Recently,there has been substantial progress in the understanding of the dominant mechanisms leading to high degrees of polarization,in the numerical modeling of these processes and in their experimental implementation.This review paper presents an overview on the current state of the field,and on the concepts of polarized laser–plasma accelerators and of beam polarimetry.

A Differential Algebraic Method for the Solution of the Poisson Equation for Charged Particle Beams

The design optimization and analysis of charged particle beam systems employing intense beams requires a robust and accurate Poisson solver.This paper presents a new type of Poisson solver which allows the effects of space charge to be elegantly included into the system dynamics.This is done by casting the charge distribution function into a series of basis functions,which are then integrated with an appropriate Green’s function to find a Taylor series of the potential at a given point within the desired distribution region.In order to avoid singularities,a Duffy transformation is applied,which allows singularity-free integration and maximized convergence region when performed with the help of Differential Algebraic methods.The method is shown to perform well on the examples studied.Practical implementation choices and some of their limitations are also explored.

Progress in particle-beam-driven inertial fusion research: Activities in Japan

Research activities in Japan relevant to particle beam inertial fusion are briefly reviewed.These activities can be ascended to the 1980s.During the past three decades,significant progress in particle beam fusion,pulsed power systems,accelerator schemes for intense beams,target physics,and high-energy-density physics research has been made by a number of research groups at universities and accelerator facilities in Japan.High-flux ions have been extracted from laser ablation plasmas.Controllability of the ion velocity distribution in the plasma by an axial magnetic and/or electric field has realized a stable high-flux low-emittance beam injector.Beam dynamics have been studied both theoretically and experimentally.The efforts have been concentrated on the beam behavior during the final compression stage of intense beam accelerators.A novel accelerator scheme based on a repetitive induction modulator has been proposed as a cost-effective particle-beam driver scheme.Beam-plasma interaction and pulse-powered plasma experiments have been investigated as relevant studies of particle beam inertial fusion.An irradiation method to mitigate the instability in imploding target has been proposed using oscillating heavy-ion beams.The new irradiation method has reopened the exploration of direct drive scheme of particle beam fusion.

IDENTIFICATION OF ALTERNARIOL, ALTERNARIOL MONOMETHYL ETHER AND ZEARALENONE BY PARTICLE BEAM LC/MS

A method for simultaneously analyzing altemariol(AOH), altemariol monomethyl ether (AME) and zearalenone(ZEA) by particle beam LC/MS was established, LC separation was accompiished with a solvent system of methanol and water (80:20 v/v). The followed particle beam LC/MS analysis gave searchable spectra of AOH. AME and ZEA. Application of this technique to analysis of an alternaria culture confirmed the presence of AOH and AME.

Electromagnetic Scattering of a High-Order Bessel Trigonometric Beam by Typical Particles

The scattering of an electromagnetic high-order Bessel trigonometric beam by several typical homogeneous dielec- tric particles is investigated. The incident beam is represented by the vector expressions in Cartesian coordinates. The scattering problems involving homogeneous dielectric particles are formulated with the surface integral equation method. As an example, the effects of the beam＇s parameters on the differential scattering cross section for a sphere are analyzed in detail. Then the numerical results for the scattering of a high-order Bessel trigonometric beam by three typical nonspherieal particles, including a spheroid, a cylinder, and a cube, are presented.

On the limitations of linear beams for the problems of moving mass-beam interaction using a meshfree method

This paper deals with the capabilities of linear and nonlinear beam theories in predicting the dynamic response of an elastically supported thin beam traversed by a moving mass. To this end, the discrete equations of motion are developed based on Lagrange＇s equations via reproducing kernel particle method （RKPM）. For a particular case of a simply supported beam, Galerkin method is also employed to verify the results obtained by RKPM, and a reasonably good agreement is achieved. Variations of the maximum dynamic deflection and bending moment associated with the linear and nonlinear beam theories are investigated in terms of moving mass weight and velocity for various beam boundary conditions. It is demonstrated that for majority of the moving mass velocities, the differences between the results of linear and nonlinear analyses become remarkable as the moving mass weight increases, particularly for high levels of moving mass velocity. Except for the cantilever beam, the nonlinear beam theory predicts higher possibility of moving mass separation from the base beam compared to the linear one. Furthermore, the accuracy levels of the linear beam theory are determined for thin beams under large deflections and small rotations as a function of moving mass weight and velocity in various boundary conditions.

Planck-Scale Gravity Test at PETRA

Quantum or torsion gravity models predict unusual properties of space-time at very short distances. In particular, near the Planck length, around 10-35 m, empty space may behave as a crystal, singly or doubly refractive. This hypothesis, however, remains uncheckable for any direct measurement since the smallest distance accessible in experiment is about 10-19 m at the LHC. Here we propose a laboratory test to measure space birefringence or refractivity induced by gravity. A sensitivity 10-31 m for doubly and 10-28 m for singly refractive vacuum could be reached with PETRA 6 GeV beam exploring UV laser Compton scattering.

Design and development of an ACCT for the Shanghai advanced proton therapy facility

The Shanghai advanced proton therapy facility is a proton cancer treatment device designed and built by the Shanghai Institute of applied physics at the Chinese academy of sciences.The accelerator part comprises a proton linear accelerator(linac)injector and a circular synchrotron.An alternating current current transformer(ACCT)is used for non-intercepting beam current measurement at the drift tube linac exit.According to the beam characteristics,the ACCT is required to complete real-time beam current and pulse width measurements at currents of3-30 mA,frequencies of 1-10 Hz,and pulse widths of40-400μs.In this paper,we report the design and development of an ACCT.The designed ACCT was simulated using CST Microwave Studio,and calibrated using an oscilloscope and signal generator.Variations in the output signal of the ACCT were investigated as a function of ceramic gap size,number of coil turns,and resistance.According to the simulation and experimental results,the optimal number of coil turns was found to be 30.In addition,a low-pass filter was adopted to filter the noise introduced during long-distance signal transmission using a coaxial cable with the length of 20 m.The calibration results show that the corresponding rise time of the ACCT is 800 ns with the sensitivity of 8.2 V/A and a droop of less than 1%,meeting the design requirements.

High Power THz Undulator Radiation from Linear Accelerator

A 30-MeV femto-second electron linac is built at the Shanghai Institute of Applied Physics, which can produce high power, coherent THz undulator radiation. We report the experimental facility and measurement of the power, frequency spectrum. First experiments show the averaged power at THz to be about 20mW.

Theoretical Design of a 104MHz Ladder Type IH-RFQ Accelerator

Beam dynamics and rf designs of a 104 MHz ladder type IH-RFQ （L-IH-RFQ） accelerator are finished at Peking University for the acceleration of 14C＋ from 40 keV to 500 keV. As a specific feature, the output beam energy spread is as low as 0.6% achieved with the internal discrete bunching method, which makes potential applications of RFQ feasible, such as accelerator mass spectrometry and ion implantation. Tolerances of the beam dynamics design are studied by means of changing the input beam parameters, and the results are quite satisfying. On the other hand, the L-IH-RFQ structure is employed, taking advantage of its mechanical stability and the absence of inter-electrode voltage asymmetry. Radio-frequency properties are studied and optimized for reducing power loss with Microwave Studio （MWS）. Tuning of the field flatness and frequency is investigated in principle.

Progress in AMS Measurement of 182Hf at CIAE

Accelerator mass spectrometry （AMS） is one of the most promising methods to detect minute amounts of 182Hf. However, the sensitivity of 5×10^-11 for ^182Hf/180Hf obtained previously by the AMS method at China Institute of Atomic Energy （CIAE） cannot meet the requirement of some applications. We present some new improvements of measurement method for AMS measurement of 182Hf at the CIAE HI？13 tandem accelerator system. As a result, a sensitivity of 1.0×10^-11 for 182Hf/180Hf is achieved.

Focusing of high polarization order axially-symmetric polarized beams

We study the high numerical aperture focusing properties and typical applications of axially-symmetric polarized beams （ASPBs） with high polarization orders. We calculate the field distribution near focus of an aplanatic system for incident ASPBs with different polarization orders and initial azimuthal angles, and based on the simulation results, we find some unique focusing properties of the beams, such as ever on-axis energy null, strong longitudinal field, and flowerlike intensity distribution at focus. In addition, we can manipulate the three-dimensional （3D） focused field distribution flexibly by use of diffractive optical elements （DOEs）, which will give rise to some interesting applications, and we also discuss possible applications and present an example of a 3D optical chain at last.

Surface plasmon interference formed by tightly focused higher polarization order axially symmetric polarized beams

We numerically study the surface plasmon interference formed by tightly focused higher polarization order axially symmetric polarized beams （ASPBs） based on the vectorial diffraction theory. The definition of ASPBs is stated, and the optical setup for surface plasmon polariton （SPP） excitation and mathematical expressions for interfering SPP fields are proposed. The simulation results show that the interfering SPP fields present a multi-focal spot pattern. In addition, the number of spots is related to the polarization order of the incident beams P as 2×（P-1）, indicating potential utilization in near-field multiple optical trapping and near-field imaging and sensing. The unique interfering phenomenon is also explained.

Teleportation of a two-particle four-component squeezed vacuum state by linear optical elements

We present a linear optical scheme for achieving a unity fidelity teleportation of a two-particle four- component squeezed vacuum state using two entangled squeezed vacuum states as quantum channel. The devices used are beam splitters and ideal photon detectors capable of distinguishing between odd and even photon numbers. Moreover, we also obtain the success probability of the teleportation scheme.

Reply to “Comment on ＇Focusing of high polarization order axially-symmetric polarized beams＇”[Chin.Opt.Lett.8,1110 （2010）]

This is a reply to the recent comment by Lifeng Li on the paper ＂Focusing of high polarization order axially-symmetric polarized beams [Chin.Opt.Lett.7,938 （2009）]＂.We analyze the errors pointed out by the comment,further perfect the mathematical expressions,and present a numerical simulation at last.

Optical forces exerted on a graphene-coated dielectric particle by a focused Gaussian beam

In this paper, we derive the analytical expression for the multipole expansion coefficients of scattering and interior fields of a graphene-coated dielectric particle under the illumination of an arbitrary optical beam. By using this arbitrary beam theory, we systematically investigate the optical forces exerted on the graphene-coated particle by a focused Gaussian beam. Via tuning the chemical potential of the graphene, the optical force spectra could be modulated accordingly at resonant excitation. The hybridized whispering gallery mode of the electromagnetic field inside the graphene-coated polystyrene particle is more intensively localized than the pure polystyrene particle, which leads to a weakened morphology-dependent resonance in the optical forces. These investigations could open new perspectives for dynamic engineering of optical manipulations in optical tweezers applications.

Measurement of absolute phase shift on reflection of thin films using white-light spectral interferometry

A novel method to measure the absolute phase shift on reflection of thin film is presented utilizing a white-light interferometer in spectral domain. By applying Fourier transformation to the recorded spectral interference signal, we retrieve the spectral phase function Ф, which is induced by three parts： the path length difference in air L, the effective thickness of slightly dispersive cube beam splitter Teff and the nonlinear phase function due to multi-reflection of the thin film structure. We utilize the fact that the overall optical path difference （OPD） is linearly dependent on the refractive index of the beam splitter to determine both L and Teff. The spectral phase shift on reflection of thin film structure can be obtained by subtracting these two parts from Ф. We show theoretically and experimentally that our new method can provide a simple and fast solution in calculating the absolute spectral phase function of optical thin films, while still maintaining high accuracy.

One-dimensional Doppler laser collimation of chromium beam with a novel pre-collimating scheme

A novel pre-collimating scheme in laser-focused chromium （Cr） atomic deposition is presented. It consists of three apertures, which are one main pre-collimating aperture at centre and two probing apertures with uniform dimension at both sides of the central one. The calculations show that the Cr atomic beam is divided into three parts accordingly after going through this scheme, and the full-width at half-maximum （FWHM） of each part decreases while the peak value increases after one-dimensional （1D） Doppler laser collimation, subsequently. Compared with that before laser collimation, the central part does not have displacement, but each part of the other two has the same displacement to the centre after laser collimation. These phenomena which are agreed with experiment prove that the novel pre-collimating scheme is a feasible means to solve the problem which we cannot observe the collimation of Cr atomic beam after substrate in laser-focused deposition with a pre-collimating scheme of only one aperture, because the atoms will be obstructed completely by the substrate.

Correction of ultraviolet single photon counting image distortion

Single photon counting imaging technology has been widely used in space environment detection, astronomy observation, nuclear physics, and ultraweak bioluminescence. However, the distortion of the single photon counting image will badly affect the measurement results. Therefore, the correction of distortion for single photon counting image is very significant. Ultraviolet single photon imaging system with wedge and strip anode is introduced and the influence factor leading to image distortion is analyzed. To correct original distorted image, three different image correction methods, namely, the physical correction, the global correction, and the local correction, are applied. In addition, two parameters, i.e., the position index and the linearity index, are defined to evaluate the performance of the three methods. The results suggest that the correction methods can improve the quality of the initial image without losing gray information of each counting light spot. And the local correction can provide the best visual inspections and performance evaluation among the three methods.

Impact of spontaneous Raman scattering on quantum channel wavelength-multiplexed with classical channel in time domain

In the quantum key distribution system, quantum channel is always affected by spontaneous Raman scattering noise when it transmits with classical channels that act as synchronization and data channels on a shared fiber. To study the effect of the noise exactly, the temporal distribution characteristics of the Raman scattering noise are analyzed theoretically and measured by a single-photon detector. On the basis of this, a scheme to decrease the noise is proposed.