Study on the fringe field effects in HEPS booster

Purpose The High Energy Photon Source(HEPS)is a 6 GeV diffraction-limited storage ring light source being built in China.HEPS booster ramps the beam energy from 500 MeV to 6 GeV with a repetition rate of 1 Hz.For the beam dynamics simulations,the consideration of the fringe field effects is not ignorable.Method To this end,several methods based on one-dimensional and three-dimensional magnetic fields are used to model the dipoles and quadrupoles of booster.Results and conclusion In this paper,we evaluate the impacts of magnetic fringe field effects of dipoles and quadrupoles on the optics of the HEPS booster.

Study on the fringe field effect of quadrupoles for CSNS MEBT

Background Medium energy beam transport(MEBT)of the China Spallation Neutron Source matches the beam from RFQ to DTL.It is found in the beam commissioning that the fringe field effect of quadrupoles in MEBT has a great influence on matching.Purpose The aspect ratio of the quadrupoles is 1.67,which induces a strong fringing field effect,and the hard-edge model used in the design needs to be improved.Methods The slicing model was performed,and the accuracy of the quadrupole model was improved.Furthermore,to use the improved model online,based on the premise that the integral field of the quadrupole magnet remains unchanged,an equivalent transfer matrix was worked out to make the beam parameters consistent with the slicing model in the simulation.Results and conclusions In the machine study,with the new model,the beam parameters at the RFQ exit were measured,which is much closer to the RFQ design value.The MEBT lattice was redesigned based on the equivalent transfer matrix.With the new matched MEBT,the transmission rate of DTL reached 99.5%in the beam commissioning,which is increased by a factor of 3%.

The development of perturbation model for fringe field in Open XAL and its application in beam commissioning of CSNS

Background The China Spallation Neutron Source(CSNS)accelerator employs Open XAL as the control software in beam commissioning.The main magnets of CSNS/RCS have serious fringe field effect;however,there is not corresponding model for fringe field in Open XAL.Purpose The purpose is to develop a suitable model for fringe field and append to the online model of Open XAL.Methods On the basis of the requirements of beam commissioning and model features of Open XAL,a perturbation model was developed to correct the effect of fringe field.Results The comparison of the parameters calculated by slice model with the values obtained from Open XAL with perturbation model showed the validity of the model.Furthermore,with the response matrix method,the values obtained from Open XAL with perturbation model were very close to the measured response matrices,which showed the accuracy of the model.Conclusion The perturbation model is effective for correcting the fringe field effect in Open XAL.

A threshold voltage model MOSFETs considering for high-k gate-dielectric fringing-field effect

In this paper, a threshold voltage model for high-k gate-dielectric metal-oxide-semiconductor field-effect transistors （MOSFETs） is developed, with more accurate boundary conditions of the gate dielectric derived through a conformal mapping transformation method to consider the fringing-field effects including the influences of high-k gate-dielectric and sidewall spacer. Comparing with similar models, the proposed model can be applied to general situations where the gate dielectric and sidewall spacer can have different dielectric constants. The influences of sidewall spacer and high-k gate dielectric on fringing field distribution of the gate dielectric and thus threshold voltage behaviours of a MOSFET are discussed in detail.

Phase unwrapping based on deep learning in light field fringe projection 3D measurement

Phase unwrapping is one of the key roles in fringe projection three-dimensional(3D)measurement technology.We propose a new method to achieve phase unwrapping in camera array light filed fringe projection 3D measurement based on deep learning.A multi-stream convolutional neural network(CNN)is proposed to learn the mapping relationship between camera array light filed wrapped phases and fringe orders of the expected central view,and is used to predict the fringe order to achieve the phase unwrapping.Experiments are performed on the light field fringe projection data generated by the simulated camera array fringe projection measurement system in Blender and by the experimental 3×3 camera array light field fringe projection system.The performance of the proposed network with light field wrapped phases using multiple directions as network input data is studied,and the advantages of phase unwrapping based on deep learning in light filed fringe projection are demonstrated.

NUMERICAL ANALYSIS OF THEORETICAL MODEL OF THE RF MEMS SWITCHES

An improved electromechanical model of the RF MEMS(radio frequency microelec- tromechanical systems)switches is introduced,in which the effects of intrinsic residual stress from fabrication processes,axial stress due to stretching of beam,and fringing field are taken into account. Four dimensionless numbers are derived from the governing equation of the developed model.A semi- analytical method is developed to calculate the behavior of the RF MEMS switches.Subsequently the influence of the material and geometry parameters on the behavior of the structure is analyzed and compared,and the corresponding analysis with the dimensionless numbers is conducted too.The quantitative relationship between the presented parameters and the critical pull-in voltage is obtained, and the relative importance of those parameters is given.

Multiplication Model of EMCCD Based on Single Type of Carrier

The avalanche multiplication principle of electron multiplication CCD (EMCCD) was discussed on the basis of single type of carrier, and the multiplication model was built by using a classic piecewise ionization rate model and avalanche multiplication integral formula. Wolff's ionization rate model was selected according to the structure and the multiplication gate amplitude of the actual devices. Compared the theoretical result with the multiplication curve of the actual device, it was found that only enough fringing field strength and multiplication area length could lead to adequate signal charge multiplication. The relationship between the multiplication gate amplitude and the total gain of the cascaded boosting EMCCD can be conveniently determined by using this model.

A 90° mixed-mode twisted nematic liquid-crystal-on-silicon with an insulating protrusion structure

A 90°mixed-mode twisted nematic liquid-crystal-on-silicon(90°-MTN LCoS) with protrusion located between the adjacent pixels is proposed to reduce the effect of fringing field. The influence of the protrusion with different widths from0.5 μm to 0.9 μm and different heights from 0.3 μm to 0.7 μm is investigated. The results demonstrate that the invalid pixel region width can be reduced by 31.5% via using the protrusion with the suitable width and height compared with no protrusion case, which provides a higher display quality, such as the higher reflectance and contrast ratio.

A PNPN tunnel field-effect transistor with high-k gate and Iow-k fringe dielectrics

A PNPN tunnel field effect transistor（TFET） with a high-k gate dielectric and a low-k fringe dielectric is introduced.The effects of the gate and fringe electric fields on the TFET＇s performance were investigated through two-dimensional simulations.The results showed that a high gate dielectric constant is preferable for enhancing the gate control over the channel,while a low fringe dielectric constant is useful to increase the band-to-band tunneling probability.The TFET device with the proposed structure has good switching characteristics,enhanced on-state current,and high process tolerance.It is suitable for low-power applications and could become a potential substitute in next-generation complementary metal-oxide-semiconductor technology.

A threshold voltage model of short-channel fully-depleted recessed-source/drain(Re-S/D) SOI MOSFETs with high-k dielectric

In this paper, a surface potential based threshold voltage model of fully-depleted（FD） recessed-source/drain（Re-S/D）silicon-on-insulator（SOI） metal-oxide semiconductor field-effect transistor（MOSFET） is presented while considering the effects of high-k gate-dielectric material induced fringing-field. The two-dimensional（2D） Poisson＇s equation is solved in a channel region in order to obtain the surface potential under the assumption of the parabolic potential profile in the transverse direction of the channel with appropriate boundary conditions. The accuracy of the model is verified by comparing the model＇s results with the 2D simulation results from ATLAS over a wide range of channel lengths and other parameters,including the dielectric constant of gate-dielectric material.

Modeling of cylindrical surrounding gate MOSFETs including the fringing field effects

A physically based analytical model for surface potential and threshold voltage including the fringing gate capacitances in cylindrical surround gate（CSG） MOSFETs has been developed.Based on this a subthreshold drain current model has also been derived.This model first computes the charge induced in the drain/source region due to the fringing capacitances and considers an effective charge distribution in the cylindrically extended source/drain region for the development of a simple and compact model.The fringing gate capacitances taken into account are outer fringe capacitance,inner fringe capacitance,overlap capacitance,and sidewall capacitance.The model has been verified with the data extracted from 3D TCAD simulations of CSG MOSFETs and was found to be working satisfactorily.

Design for the lattice with 4-DBA structure of the compact laser-electron storage ring

We try to design the lattice with 2 super periods and 4-DBA structure in order to provide more drifts for the future development of the TTX source. Due to the space limitation in the lab, the 4-DBA lattice is suitable.In the paper,we present the lattice design with a 4-DBA structure mainly for the pulse mode of the compact laser-electron storage ring （LESR）. Element parameters of the lattice are optimized with the help of the professional software and beam dynamics such as intra-beam scattering （IBS） and Compton scattering （CS） are calculated. Besides, the fringe field effect is analyzed with the numerical method.