Giant magneto-impedance sensor with working point selfadaptation for unshielded human bio-magnetic detection

Background Compared with traditional biomagnetic field detection devices,such as superconducting quantum interference devices(SQUIDs)and atomic magnetometers,only giant magneto impedance(GMI)sensors can be applied for unshielded human brain biomagnetic detection,and they have the potential for application in next-generation wearable equipment for brain-computer interfaces(BCIs).Achieving a better GMI sensor without magnetic shielding requires the stimulation of the GMI effect to be maximized and environmental noise interference to be minimized.Moreover,the GMI effect stimulated in an amorphous filament is closely related to its working point,which is sensitive to both the external magnetic field and the drive current of the filament.Methods In this paper,we propose a new noise reducing GMI gradiometer with a dual-loop self-adapting structure.Noise reduction is realized by a direction-flexible differential probe,and the dual-loop structure optimizes and stabilizes the working point by automatically controlling the external magnetic field and drive current.This dual-loop structure is fully program controlled by a micro control unit(MCU),which not only simplifies the traditional constant parameter sensor circuit,saving the time required to adjust the circuit component parameters,but also improves the sensor performance and environmental adaptation.Results In the performance test,within 2 min of self-adaptation,our sensor showed a better sensitivity and signal-to-noise ratio(SNR)than those of the traditional designs and achieved a background noise of 12 pT/√Hz at 10 Hz and 7pT/√Hz at 200 Hz.Conclusion To the best of our knowledge,our sensor is the first to realize self-adaptation of both the external magnetic field and the drive current.

Design of Microstructure Parameters on a Small Multi-Throttle Aerostatic Guideway in Photolithography

A compact multi-throttle aerostatic guideway is the preferred structure for high precision and acceleration motion in the variable-slit system(VS)of photolithography.The presence of microstructure,such as recesses and grooves,on the guideway working surface has been found to improve the loading performance.Nevertheless,the effects on the guideway performance of changing the microstructure on the micron level are not yet clear.The mesh adaptation method,which was proposed by the authors,is employed in this paper to quantitatively study the influences of four microstructure parameters.The effect of tuning these parameters on the loading performance is revealed.The level of impact determines the proposed design process of the parameters.The characteristic feature of the proposed design process is that the working points of carrying capacity,stiffness,and rotational stiffness are unified under twoway adjusting by means of recess parameters.According to the proposed design process and tuning method,the restriction of supply pressure is lifted to a certain extent and the mutual tradeoff among the loading performances is relieved.The experimental results show that the rotational stiffness of the designed guideway,based on the tuned parameters,reached 2.14×10^(4) Nmrad1 and increased by 69.8%.In a scanning test of the applied VS on argon fluoride laser(ArF)photolithography,the average scanning acceleration reached 67.5 m·s^(-2),meeting the design specification.

Improving nonlinear performance of the HEPS baseline design with a genetic algorithm

A baseline design for the High Energy Photon Source has been proposed, with a natural emittance of 60 pm.rad within a circumference of about 1.3 kilometers. Nevertheless, the nonlinear performance of the design needs further improvements to increase both the dynamic aperture and the momentum acceptance. In this study, genetic optimization of the linear optics is performed, so as to find all the possible solutions with weaker sextupoles and hence weaker nonlinearities, while keeping the emittance at the same level as the baseline design. The solutions obtained enable us to explore the dependence of nonlinear dynamics on the working point. The result indicates that with the same layout, it is feasible to obtain much better nonlinear performance with a delicate tuning of the magnetic field strengths and a wise choice of the working point.

Stabilization of betatron tune in Indus-2 storage ring

Indus-2 is a synchrotron radiation source that is operational at RRCAT, Indore, India. It is essentially pertinent in any synchrotron radiation facility to store the electron beam without beam loss. During the day to day operation of Indus-2 storage ring, difficulty was being faced in accumulating higher beam current. After examination, it was found that the working point was shifting from its desired value during accumulation. For smooth beam accumulation, a fixed desired tune in both horizontal and vertical plane plays a significant role in avoiding beam loss via the resonance process. This required a betatron tune feedback system to be put in the storage ring. After putting ON this feedback, the beam accumulation was smooth. The details of this feedback and its working principle are described in this paper.