Enhanced Sensitivity of FeGa Thin-Film Coated SAW Current Sensor

A surface acoustic wave (SAW) device is proposed for sensing current by employing the patterned FeGa thin film as the sensitive interface. The layered media structure of FeGa/SiO2/LiNbO3 was established to reveal the working principle of the sensors, and an SAW chip patterned by delay-line and operating at 150 MHz was fabricated photolithographically on 128° YX LiNbO3 substrate. The FeGa thin film with a larger magnetostrictive coefficient was sputtered onto the acoustic propagation path of the SAW chip to build the sensing device. The prepared device was connected into the differential oscillation loop to construct the current sensor. The FeGa thin film produces magnetostrictive strain and so-called ΔE effect at the magnetic field generated by the applied current, which modulates the SAW propagation velocity accordingly. The differential frequency signal was collected to characterize the measurand. Larger sensitivity of 37.9 kHz/A, low hysteresis error of 0.81%, excellent repeatability and stability were achieved in the experiments from the developed sensing device.

Nonlinear Dynamics of MEMS Resonator in PLL-AGC Self-Oscillation Loop

The work is devoted to the study of a MEMS resonator dynamics under the action of phase-locked and automatic gain control loops. Particular attention is directed to the study of the nonlinearity factor of the resonator elastic restoring force. It was found that the determination of control system parameters based on the stability analysis of the operating resonant mode, in the general case, does not provide the required phase adjustment and stabilization of the oscillation amplitude. Stable multifrequency modes of oscillations are found, an analytical study of the mechanisms of their appearance and evolution is carried out under variation of the key parameters of the system. The real regions of the control system stable operation are determined (which do not coincide, as was found, with the regions of stability of the operating resonant mode, due to the presence of hidden attractors in the phase space of the system). A methodology has been developed for identifying such areas of stable operation. A significant complication of the structure of possible motions in the system with an increase in the Q-factor of the resonator is revealed.

Development of a High Stability Pd-Ni Alloy Thin-Film Coated SAW Device for Sensing Hydrogen

A Pd-Ni alloy thin-film coated surface acoustic wave (SAW) device is proposed for sensing hydrogen. The Pd-Ni thin-film was sputtered onto the SAW propagation path of a SAW device with a delay line pattern to build the chip-sized hydrogen sensor. The prepared sensor chip was characterized by employing a differential oscillation loop. The effect of the Pd-Ni film thickness on sensing performance was also evaluated, and optimal parameters were determined, allowing for fast response and high sensitivity. Excellent working stability (detection error of 3.7% in half a year), high sensitivity (21.3 kHz/%), and fast response (less than 10 s) were achieved from the 40 nm Pd-Ni alloy thin-film coated sensing device.

Noise and Electrical Oscillations Generation during the Investigation of the Resistive Switching in the Yttria Stabilized Zirconia Films by Conductive Atomic Force Microscopy

The effect of resistive switching in the yttria stabilized zirconia (YSZ) thin films on Si substrates has been studied by Conductive Atomic Force Microscopy (CAFM). The resistive switching of the YSZ films from the low conductive state to the highly conductive one has been found to be associated with the increasing of the noise with broad frequency spectrum related to the redistribution of the oxygen vacancies in YSZ. The electrical oscillations in oscillation loop connected in series to the CAFM probe, the sample, and the bias source related to the excitation of the oscillation loop by the noise in the probe-to-sample contact film have been observed. The effect discovered is promising for application in the memristor devices of new generation.

Effect of external resonant fields and limiter biasing on hard X-ray intensity and mirnov oscillations in IR-T1 Tokamak

Runaway electrons in tokamaks can cause serious damage to the first wall of the reactor and decrease its life time. Also, hard x-ray emission generated from high energy runaway electrons lead to the plasma energy loss. Therefore, suggesting methods to minimize runaway electron in tokamaks are very important. Applying external resonant field is one of the methods for controlling the Magneto Hydrodynamic (MHD) activity. Relation between the MHD activity and runaway electrons has already been studied (Jaspers et al. 1994; Ghanbari et al. 2012) Jaspers, R., et al. 1994 Phys. Rev. Lett.72, 4093; Ghanbari, M. R., et al. 2012a Phys. Scr.83, 055501. Present study attempts to investigate the effects of limiter biasing and Resonant Helical magnetic Field (RHF) on the generation of runaway electrons. For this purpose, plasma parameters such as plasma current, MHD oscillation, loop voltage, emitted hard x-ray intensity, Halpha impurity, safety factor in the presence and absence of external fields, were measured. Frequency activity was investigated with FFT analysis. The results show that applying resonant fields can control the MHD activity, and then hard x-ray emitted from the runaway electrons.

Oscillation Loop for a Vibratory Gyroscope and Its Experiment Study

This paper investigates the design of a self-oscillation loop for the gyroscope system. The dynamic equations describing this system are analyzed using the method of averaging, and a criterion for selecting the circuit parameters is established based on the analysis. The validity of the criterion and the effectiveness of the control scheme are verified by the experimental results obtained from the control parameters that satisfy or violate the stability criterion. The performance of the self-oscillation loop with a z-axis gyroscope is also evaluated in light of the experimental results. The self-oscillation loop based on the auto gain control scheme effectively tracks the resonance frequency of a z-axis gyroscope. This frequency corresponds to a standard Allan variance of 0.04 Hz in 8 min at natural frequency. The output signal-to-noise ratio (SNR) is about 90 dB, and the vibratory velocity amplitude shows a deviation of 0.5% in 8 min.