Analysis and Optimization of Stability of CAS-LIBB Single Ion Microbeam

Single ion microbeam is the most advanced technology which can emit a single ion for precise localization. A single-ion microbeam facility has been constructed at the Key Laboratory of Ion Beam Bioengineering （LIBB）, Chinese Academy of Sciences （CAS）, with a spatial resolutions of about 5 μm. Based on CAS-LIBB microbeam, three key elements affecting the quality of the system are assessed： the size of beam spot, the energy range and the counting accuracy of implanting ions. Various contributions to the ion beam stability, including the ion source, the terminal voltage of electrostatic accelerator and the components in beam pipeline, are discussed. Analysis shows that the improvement of terminal voltage stability is the most important issue for future optimization of CAS-LIBB facility. Some preliminary investigations and project aimed at optimization and development are proposed as well.

Improvement of Laser Frequency Stabilization for the Optical Pumping Cesium Beam Standard

A method is presented to improve the laser frequency stabilization for the optical pumping cesium clock. By comparing the laser frequency stabilization of different schemes, we verify that the light angle is an important factor that limits the long-term frequency stability. We minimize the drift of the light angle by using a fiber- coupled output, and lock the frequency of a distributed-feedback diode laser to the fluorescence spectrum of the atomic beam. The measured frequency stability is about 3.5 ×10^-11 at i s and reaches 1.5 × 10^-12 at 2000s. The Allan variance keeps going down for up to thousands of seconds, indicating that the medium- and long-term stability of the laser frequency is significantly improved and perfectly fulfills the requirement for the optical pumping cesium clock.

An efficient Galerkin meshfree formulation for shear deformable beam under finite deformation

This paper proposes a geometrically nonlinear total Lagrangian Galerkin meshfree formulation based on the stabilized conforming nodal integration for efficient analysis of shear deformable beam.The present nonlinear analysis encompasses the fully geometric nonlinearities due to large deflection,large deformation as well as finite rotation.The incremental equilibrium equation is obtained by the consistent linearization of the nonlinear variational equation.The Lagrangian meshfree shape function is utilized to discretize the variational equation.Subsequently to resolve the shear and membrane locking issues and accelerate the computation,the method of stabilized conforming nodal integration is systematically implemented through the Lagrangian gradient smoothing operation.Numerical results reveal that the present formulation is very effective.

BOUNDARY FEEDBACK CONTROL OF ELASTIC BEAM EQUATION WITH STRUCTURAL DAMPING AND STABILITY

In this paper, we consider the partial differential equation of an elastic beam with structuraldamping by boundary feedback control. First, we prove this closed system is well--posed; then weestablish tbe exponential stability for this elastic system by using a theorem whichbelongs to F. L.Huang; finally, we discuss the distribution and multiplicity of the spectrum of this system. Theseresults are very important and useful in practical applications.

Method for active spatial alignment and stabilization of laser beams in multi-beam systems

We propose a new method for the development of multi-beam systems for the spatial alignment and stability of beams based on the error separation technique.This method avoids alignment errors caused by coupling effect of piezoelectric devices,inaccurate correction calculations,and detection mode of the angular deviation.According to the results by external detectors,the error value of spatial alignment and the root mean square[RMS]of deviations under control during 1 h can be equivalent to approximately 0.87 and 1.06 nm at the sample plane under an oil immersion lens[focal length f=2 mm].The RMS of deviations is less than one-third of those currently reported for multi-beam systems;therefore,higher alignment and stability accuracy can be achieved with our proposed method.

The broadband laser source and an active beam stabilization device for laser calibration systems

Purpose Currently,the calibration for astronomical telescopes requires a broadwavelength range of several hundred nanometers.Therefore,a simple and compact wavelength broadening device is applied to generate a variety of wavelengths.In addition,a beam stabilization system is designed to automatically correct the beam deviation due to vibration and temperature fluctuation.Methods We broaden the laser spectrum by nonlinear effect between the noble gas in a hollow-core fiber and the laser electric field.By selecting the species and pressure of the noble gases,one can control the spectral broadening.The active beam stabilization system consists of two mirror mounts with motorized actuators and two CCD cameras.After acquiring the centroid of the laser beam and comparing it with the target position,an algorithm is implemented to correct the beam pointing.Results Both experimental and simulation results show that the spectral range of the laser is greatly broadened.Besides,we have attained the phase of pulses.These parameters can be used to monitor the laser’s running status over time.The active stabilization system can quickly correct the deviation of beam pointing and simultaneously obtain the beam profile,allowing for nominally perfect control of the beam.Conclusion In our design,both the broadband laser source and beam stabilizer are involved in the laser calibration system,providing us with various wavelengths and a high-precision pointing with outstanding intrinsic long-term stability.

Design of precision acquisition system for precision power supply of photon source

Purpose Photon source has developed to the fourth generation.The requirements for beam stability and power supply output current stability have been greatly improved.In this paper,a precision acquisition system is designed for improving the stability for power supply output current.Method The acquisition system consists of two parts,the analog to digital converter(ADC)system and the temperature control system.The composition and software simulation analysis are given in this paper.Results A prototype is made and tested.The test results showed that the acquisition system has an effective resolution of 15.5 bits,signal-to-noise ratio(SNR)of 98 dB,and integral nonlinearity(INL)of 86 ppm.The internal temperature stable range is±0.06℃.Conclusions The acquisition system can fully meet the requirements of the developed photon source.