A New Three-Dimensional Code for Simulation of Ion Beam Extraction: Ion Optics Simulator

A new thee-dimensional code, ion optics simulator （IOS）, to simulate ion beam extraction is developed in visual C＋＋ language. The theoretical model, the flowchart of code, and the results of calculation as an example are presented.

Evaluation of Clinical Efficacy of Wumen Acupuncture in the Adju-vant Treatment of Non-arteriticAnterior Ischemic Optic Neuropathy

[Objectives]To explore the clinical efficacy of Wumen acupuncture in the adjuvant treatment of non-arteritic anterior ischemic op-tic neuropathy(NAION).[Methods]From June 2023 to April 2024,40 NAION patients were randomly divided into treatment group(Wu-men acupuncture method+methylprednisolone sodium succinate+compound Danshen dripping pills orally)and control group(methylpred-nisolone sodium succinate+compound Danshen dripping pills orally).The clinical symptoms such as fundus condition and visual field were compared between the two groups before treatment,after 2 courses of treatment and 6 months after the first diagnosis.[Results](i)After 2 courses of treatment,the patients with optic disc edema in the treatment group were more than those in the control group,and the difference was significant(P<0.05).The number of patients with retinal hemorrhage in the treatment group was less than that in the control group,and the difference was significant(P<0.05).The color of the optic nerve in the treatment group was less than that in the control group,and the difference was not significant(P>0.05).(ii)Six months after the first diagnosis,the improvement of fundus in the treatment group was bet-ter than that in the control group(P<0.05).After 2 courses of treatment and 6 months after the first diagnosis,the visual evoked potential was significantly improved compared with the control group(P<0.05).After 2 courses of treatment and 6 months from the first diagnosis,the number of lines of visual acuity improvement in the treatment group was greater than that in the controlgroup(P<0.05).After 2 courses of treatment and 6 months from the first diagnosis,the average visual field defect in the treatment group was lower than that in the control group(P<0.05).[Conclusions]Wumen acupuncture method can significantly improve the symptoms of patients with non-arteritic anterior ische-mic optic neuropathy,which is worthy of clinical promotion.

Particle Simulation of Three-Grid ECR Ion Thruster Optics and Erosion Prediction

Ion optics is a critical component of ion thrusters. A two-dimensional axisymmetric model is developed to study the characteristics of three-grid electron cyclotron resonance ion thruster optics. The code is based on a particle-in-cell combined with the Monte Carlo collision method to simulate ion dynamics and charge-exchange processes in the grid region. The simulation results show that the mode can give a reasonable estimate of the physics characteristics of the ion optics. The design of the ion optics satisfies the requirement of preventing electron backstreaming. Charge-exchange ions can cause damage to the grids, especially to the accelerator grid. ＇Barrel＇ erosion can increase the accelerator grid aperture radius at a rate of 1.91~ 10-11 m/s, while the decelerator grid plays an important role in reducing ＇pits-and-grooves＇ erosion.

Numerical Simulation of Ion Extraction Through Ion Thruster Optics

Based on the particle-in-cell （PIC） method, a two-dimensional numerical scheme was developed to investigate the ion beam extraction phenomena through the ion thruster optics. According to the calculated results, the plasma sheath upstream of the screen grid, the electric field in the calculation domain, and the ion and electron spatial distributions are obtained for different accelerator grid voltages. The results indicate that the accelerator grid voltage affects the plasma sheath upstream of the screen grid significantly. It is found that a moderate accelerator grid voltage results in an ion optical performance better than either a higher or lower voltage, from a point of ion extraction from the discharge chamber and erosion mitigation of the accelerator grid due to the direct ion impingement.

Generation of Continuous-Wave 194 nm Laser for Mercury Ion Optical Frequency Standard

A 194-nm cw laser is an essential part in the mercury ion optical frequency standard. We report the generation of over 2mW continuous-wave radiation at 194nm in a beta barium borate crystal using a simple sum frequency mixing （SFM） system. One source beams at 718nm is resonantly enhanced with a cavity and the other at 266mn makes a single pass. Considering the walk-off effect in SFM, the source beam waists are designed to be elliptical, thus the conversion efficiency can be promoted. The 266-nm beam produced by frequency doubling of 532-nm laser is shaped close to the diffraction limit to achieve better mode matching.

Direct Laser Cooling Al^＋ Ion Optical Clocks

The Al^＋ ion optical clock is a very promising optical frequency standard candidate due to its extremely small black-body radiation shift. It has been successfully demonstrated with the indirect cooled, quantum-logic-based spectroscopy technique. Its accuracy is limited by second-order Doppler shift, and its stability is limited by the number of ions that can be probed in quantum logic processing. We propose a direct laser cooling scheme of AI＋ ion optical clocks where both the stability and accuracy of the clocks are greatly improved. In the proposed scheme, two Al^＋ traps are utilized. The first trap is used to trap a large number of Al^＋ ions to improve the stability of the clock laser, while the second trap is used to trap a single Al^＋ ion to provide the ultimate accuracy. Both traps are cooled with a continuous wave 167nm laser. The expected clock laser stability can reach 9.0 × 10^-17/√τ. For the second trap, in addition to 167nm laser Doppler cooling, a second stage pulsed 234nm two-photon cooling laser is utilized to further improve the accuracy of the clock laser. The total systematic uncertainty can be reduced to about 1 × 10^-18. The proposed Al^＋ ion optical clock has the potential to become the most accurate and stable optical clock.

Theoretical calculations of hyperfine splitting,Zeeman shifts,and isotope shifts of^(27)Al^(+)and logical ions in Al^(+)clocks

Based on the multiconfiguration Dirac-Hartree-Fock(MCDHF)method,similar models are employed to simultaneously calculate the first-order and second-order Zeeman coefficients as well as the hyperfine interaction constants of the related energy levels of ^(27)Al^(+)and its logical ions ^(9)Be^(+)and^(25)Mg^(+)in the^(27)Al^(+)optical clock.With less than 0.34%deviations from experimental values in Zeeman coefficients of^(27)Al^(+),these calculated parameters will be of great help for better evaluation of the systematic uncertainty.We also calculate the isotope shift parameters of the related energy levels,which could extend our knowledge and understanding of nuclear properties of these ions.

Progress on the^40Ca^+ion optical clock

Progress of the ^40Ca^+ion optical clock based on the 4^2S1/2-3d ^2D5/2 electric quadrupole transition is reported.By setting the drive frequency to the“magic”frequencyΩ0,the frequency uncertainty caused by the scalar Stark shift and second-order Doppler shift induced by micromotion is reduced to the 10^-19 level.By precisely measuring the differential static scalar polarizability∆α0,the uncertainty due to the blackbody radiation(BBR)shift(coefficient)is reduced to the 10^-19 level.With the help of a second-order integrating servo algorithm,the uncertainty due to the servo error is reduced to the 10^-18 level.The total fractional uncertainty of the ^40Ca^+ion optical clock is then improved to 2.2×10^-17,whereas this value is mainly restricted by the uncertainty of the BBR shift due to temperature fluctuations.The state preparation is introduced together with improvements in the pulse sequence,and furthermore,a better signal to noise ratio(SNR)and less dead time are achieved.The clock stability of a single clock is improved to 4.8×10^-15√τ(in seconds).

Copper Ion Beam Irradiation-Induced Effects on Structural,Morphological and Optical Properties of Tin Dioxide Nanowires

The 0.8 Me V copper （ Cu） ion beam irradiation-induced effects on structural, morphological and optical properties of tin dioxide nanowires （Sn02 NWs） are investigated. The samples are irradiated at three different doses 5 × 10^12 ions/cm2, 1 ×10^13 ions/cm2 and 5 × 10^13 ions/em2 at room temperature. The XRD analysis shows that the tetragonal phase of Sn02 NWs remains stable after Cu ion irradiation, but with increasing irradiation dose level the crystal size increases due to ion beam induced coalescence of NWs. The FTIR spectra of pristine Sn02 NWs exhibit the chemical composition of SnO2 while the Cn-O bond is also observed in the FTIR spectra after Cu ion beam irradiation. The presence of Cu impurity in SnO2 is further confirmed by calculating the stopping range of Cu ions by using TRM/SRIM code. Optical properties of SnO2 NWs are studied before and after Cu ion irradiation. Band gap analysis reveMs that the band gap of irradiated samples is found to decrease compared with the pristine sample. Therefore, ion beam irradiation is a promising technology for nanoengineering and band gap tailoring.

Tungsten ion source under double-pulse laser ablation system

New tungsten ion source is produced by using single and double-pulse laser ablation system. Combined collinear Nd：YAG laser beams（266＋1064 nm） are optimized to focus on the sample in air. Optimization of the experimental parameters is achieved to enhance the signal-to-noise ratio of the emission spectra. The velocity distribution of the emitted plasma cloud is carefully measured. The influences of the potential difference between the bias electrodes, laser wavelength and intensity on the current signal are also studied. The results show that the increase in the tungsten ion velocity under the double-pulse lasers causes the output current signal to increase by about three folds. The electron density and temperature are calculated by using the Stark-broadened line profile of tungsten line and Boltzmann plot method of the upper energy levels, respectively. The signal intensity dependence of the tungsten ion angular distribution is also analyzed. The results indicate that the double-pulse laser ablation configuration is more potent technique for producing more metal ion source deposition, thin film formation, and activated plasma-facing component material.

Understanding hydrogen plasma processes based on the diagnostic results of 2.45 GHz ECRIS at Peking University

Optical emission spectroscopy（OES）, as a simple in situ method without disturbing the plasma, has been performed for the plasma diagnosis of a 2.45 GHz permanent magnet electron cyclotron resonance（PMECR） ion source at Peking University（PKU）. A spectrum measurement platform has been set up with the quartz-chamber electron cyclotron resonance（ECR） ion source [Patent Number： ZL 201110026605.4] and experiments were carried out recently. The electron temperature and electron density inside the ECR plasma chamber have been measured with the method of line intensity ratio of noble gas. Hydrogen plasma processes inside the discharge chamber are discussed based on the diagnostic results. What is more, the superiority of the method of line intensity ratio of noble gas is indicated with a comparison to line intensity ratio of hydrogen. Details will be presented in this paper.

Numerical Simulation of Characteristics of CEX Ions in Ion Thruster Optical System

Charge exchange （CEX） ions could inflict severe damages on the ion thruster optical system. This article is aimed at investigating the characteristics of the CEX ions and their influences upon the optical system by means of particle-incell（PIC） ion simulation and Monte Carlo collision（MCC） methods. The results from numerical simulation indicate that despite the fact that CEX ions appear in the entire beamlet region near the ion optical system, the ones that present themselves downstream of the accelerator grid have good reason for attracting more attention. As their trajectories are significantly affected by the local electric field, a great number of CEX ions are accelerated toward grids resulting in sputtering erosion. When the influences of the CEX ions are considered in the nulnerical simulation,there could hardly be observed augments in the screen grid current,but the accelerator grid current increases from zero to 1.4% of the beamlet current. It can be understood from the numerical simulation that the CEX ions formed in the region far downstream of the accelerator grid should be blamed for the erosion on the downstream surface of the accelerator grid.

Design of the IMP microbeam irradiation system for 100 MeV/u heavy ions

A state-of-the-art high energy heavy ion microbeam irradiation system is constructed at the Institute of Modern Physics of the Chinese Academy of Sciences. This microbeam system operates in both full current intensity mode and single ion mode. It delivers a predefined number of ions to pre-selected targets for research in biology and material science. The characteristic of this microbeam system is high energy and vertical irradiation. A quadrupole focusing system, in combination with a series of slits, has been designed to optimize the spatial resolution. A symmetrically achromatic system leads the beam downwards and serves simultaneously as an energy analyzer. A high gradient quadrupole triplet finally focuses a C^6＋ ion beam to 1 μm in the vacuum chamber within the energy range from 10 MeV/u to 100 MeV/u. In this paper, the IMP microbeam system is described in detail. A systematic investigation of the ion beam optics of this microbeam system is presented together with the associated aberrations. Comparison is made between the IMP microbeam system and the other existing systems to further discuss the performance of this microbeam. Then the optimized initial beam parameters are given for high resolution and high hitting efficiency. At last, the experiment platform is briefly introduced.

Study of the aberrations of the IMP heavy ion microbeam irradiation system

A high energy heavy ion microbeam irradiation system is constructed at the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences (CAS). A quadrupole focusing system, in combination with a series of slits, has been designed here. The IMP microbeam system is described in detail. The intrinsic and parasitic aberrations associated with the magnets are simulated. The ion beam optics of this microbeam system is investigated systematically. Then the optimized initial beam parameters are given for high spatial resolution and high hitting rates.

Tuning plasmon absorption of unmodified silver nanoplates for sensitive and selective detection of copper ions by introduction of ascorbate

Silver nanoplates as novel optical sensors for Cu^2＋ detection have been demonstrated.Silver nanoplates are synthesized via previous H_2O_2-NaBH_4 cyclic oxidation-reduction reactions.With introduction of ascorbate as mild reductants,Cu^2＋ ions are reduced into Cu~＋ and the Cu^＋ is further reduced to Cu,which is deposited on the surface of the silver nanoplates.The deposition of the Cu on the surface of the silver nanoplates allows a significant red-shift of their plasmon absorption.Therefore,trace Cu^2＋ can be detected.The shift of the plasmon absorption wavelength of silver nanoplates is proportional to the Cu^2＋concentration over a range of 40-340 μmol L^（-1） with a limit of detection of 9.0 μmol L^（-1）.Moreover,such silver nanoplate-based optical sensors provide good selectivity for Cu^2＋ detection,and most other metal ions do not disturb its detection.Moreover,the practicality of the proposed sensor was tested.This Cu^2＋assay is advantageous in its simplicity,selectivity,and cost-effectiveness.

Optical properties and dynamic process in metal ions doped on CdSe quantum dots sensitized solar cells

In recent years, the nanostructure for solar cells have attracted considerable attention from scientists as a result of a promising candidate for low cost devices. In this work, quantum dots sensitized solar cells with effective performance based on a co-sensitized Cd S∕Cd Se：Mn2＋（or Cu2＋） nanocrystal, which was made by successive ionic layer absorption and reaction, are discussed. The optical, physical, chemical, and photovoltaic properties of quantum dots sensitized solar cells were sensitized to Mn2＋and Cu2＋dopants. Therefore, the short current（JSC）of the quantum dot sensitized solar cells is boosted dramatically from 12.351 mA∕cm2 for pure Cd Se nanoparticles to 18.990 mA∕cm2 for Mn2＋ions and 19.915 mA∕cm2 for Cu2＋ions. Actually, metal dopant extended the band gap of pure Cd Se nanoparticles, reduced recombination, enhanced the efficiency of devices, and improved the charge transfer and collection. In addition, Mn2＋and Cu2＋dopants rose to the level of the conduction band of pure Cd Se nanoparticles, which leads to the reduction of the charge recombination, enhances the lightharvesting efficiency, and improves the charge diffusion and collection. The results also were confirmed by the obtained experimental data of photoluminescence decay and electrochemical impedance spectroscopy.

Plasma parameter diagnosis using hydrogen emission spectra of a quartz-chamber 2.45 GHz ECRIS at Peking University

A quartz-chamber 2.45 GHz electron cyclotron resonance ion source(ECRIS) was designed for diagnostic purposes at Peking University [Patent Number: ZL 201110026605.4]. This ion source can produce a maximum 84 m A hydrogen ion beam at 50 k V with a duty factor of 10%. The root-mean-square(RMS) emittance of this beam is less than 0.12π mm mrad. In our initial work,the electron temperature and electron density inside the plasma chamber had been measured with the line intensity ratio of noble gases. Based on these results, the atomic and molecular emission spectra of hydrogen were applied to determine the dissociation degree of hydrogen and the vibrational temperature of hydrogen molecules in the ground state, respectively. Measurements were performed at gas pressures from 4×10^(-4) to 1×10^(-3) Pa and at input peak RF power ranging from 1000 to 1800 W. The dissociation degree of hydrogen in the range of 0.5%-10% and the vibrational temperature of hydrogen molecules in the ground state in the range of 3500-8500 K were obtained. The plasma processes inside this ECRIS chamber were discussed based on these results.