Compensation Electrodes Research Articles

Direct Phase Measurement and Compensation to Enhance MEMS Gyroscopes ZRO Stability

This research introduces a closed-loop method to improve the zero-rate output (ZRO) stability of amplitude-modulated (AM) capacitive MEMS gyroscopes, even in absence of quadrature compensation electrodes. The method relies on the direct measurement and closed-loop compensation of the variation of the relative phase between the quadrature output, modulated by the drive carrier frequency, and the demodulation reference. The closed loop includes a phase meter, whose output regulates the phase of the lock-in amplifier inside the sense-mode, open-loop, demodulation chain. The proposed technique, tested on the pitch axis of a consumer-grade commercial monolithic 3-axis gyroscope, brings up to 300-fold stability improvements over temperature transients, without affecting noise and scale-factor performance. Stability limits depend on the phase meter resolution and on the lock-in granularity in regulating the phase. Overall, a mdps/K stability is obtained with a one-time calibration at ambient temperature and no post-acquisition processing. [2021-0049]

Design and test of large-range wave height sensor based on water resistance measurement and fuzzy system

Aiming at the easily damaged capacitive wave height sensor and the requirement for large-range wave height measurement in large-scale wave-making experiment, a large-range wave height sensor based on measuring water resistance is proposed. The mechanical structure, detection circuit, and the selection of main components of the sensor are described in detail. The parallelism of the two measuring electrodes is guaranteed by tensioning and rotating mechanism. In order to overcome the polarization phenomenon of water in the state of electrification, AC power supply is used as signal source. Compensation electrodes are installed to compensate for the effects of water quality and temperature changes. In addition, this paper uses the T-S fuzzy system theory to realize the fault diagnosis of the wave height sensor. Through linearity test, water quality change test, and contrast test with visual wave height measurement system, it can be seen that the sensor has high linearity and is not affected by water quality change, and the measurement results are accurate and reliable.

Minimally Invasive Microneedle Array Electrodes Employing Direct Electron Transfer Type Glucose Dehydrogenase for the Development of Continuous Glucose Monitoring Sensors

Closed loop systems hinge on the accuracy and precision of the continuous glucose monitoring sensors. Most of the commercially available continuous glucose monitoring sensors is implanted subcutaneously for a period of 7-14 days. The subsequent biofouling effects have implications on the performance of the sensors over time especially at low glucose concentrations. In addition, the commercially available sensors are sensitive to the presence of interfering species such as acetaminophen in the skin compartment. We report here on the marriage of minimally invasive, continuous glucose sensors and a direct electron transfer type glucose dehydrogenase enzymatic system. Whilst the microneedles here are designed to sit in the dermal interstitial fluid over a 24-48 hour period to minimize the biofouling effect, the direct electron transfer enzyme allows operation of the electrochemical sensor at lower potentials to minimize the effect of interference. The microneedle structure design also enables the use of compensation electrodes for background subtraction to further nullify the effects of interference.

Design of the Ion Trap and Vacuum System for 171Yb-ion Optical Frequency Standard

We are developing a frequency standard based on the ultra-narrow electric octupole transition of the ytterbium-ion (171Yb+), which is in the optical wavelength region. In this article, we describe optimized design of our end-cap type Paul trap which will be used for trapping single ions for precision frequency metrology. Selection of the materials for fabricating different parts of the trap assembly is also described. Customized design of the ultra-high vacuum chamber, which houses the ion trap, oven producing ytterbium atomic beam, compensation electrodes and high numerical aperture fluorescence collection lens together with four pairs of optical viewports is lastly described.

Study on Vertical Dynamics Compensation for Wobbling Effect Mitigation of Electrostatically Levitated Gyroscope

We present a study of vertical dynamics control of an electrostatically levitated gyro-accelerometer considering the wobbling effect and propose a tilt stabilization method with newly introduced control electrodes. Typically, a rotor in a vacuum rotates at high velocity, which may create a drift rate and lead to displacement instability due to the tilt angle of the rotor. To analyze this, first we set up a vertical dynamic equation and determined simulation results regarding displacement control. After deriving an equation for drift dynamics, we analyzed the drift rate of the rotor and the wobbling effect for displacement control quantitatively. Then, we designed new sub-electrodes for moment control that will decrease the drift amplitude of wobbling dynamics. Finally, a simulation study demonstrated that the vertical displacement control with the wobbling compensation electrodes mitigated the rotor’s drift rate, showing the effectiveness of the newly proposed control electrodes.

Electrically Compensated Fourier Transform Ion Cyclotron Resonance Cell for Complex Mixture Mass Analysis

Complex natural organic mixtures such as petroleum require ultrahigh mass spectral resolution to separate and identify thousands of elemental compositions. Here, we incorporate a custom-built, voltage-compensated ICR cell for Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS), based on a prior design by Tolmachev to produce optimal mass resolution. The compensated ICR cell installed in a custom-built 9.4 T FTICR mass spectrometer consists of seven cylindrical segments with axial proportions designed to generate a dc trapping potential that approaches an ideal three-dimensional axial quadrupolar potential. However, the empirically optimized compensation voltages do not correspond to the most quadrupolar trapping field. The compensation electrodes minimize variation in the reduced cyclotron frequency by balancing imperfections in the magnetic and electric field. The optimized voltages applied to compensation electrodes preserve ion cloud coherence for longer transient duration by approximately a factor of 2, enabling separation and identification of isobaric species (compounds with the same nominal mass but different exact mass) common in petroleum, such as C(3) vs SH(4) (separated by 3.4 mDa) and SH(3)(13)C vs (12)C(4) (separated by 1.1 mDa). The improved performance of the ICR cell provides more symmetric peak shape and better mass measurement accuracy. A positive ion atmospheric pressure photoionization (APPI) petroleum spectrum yields more than 26,000 assigned peaks, Fourier-limited resolving power of 800,000 at m/z 500 (6.6 s transient duration), and 124 part per billion root mean square (rms) error. The tunability of the compensation electrodes is critical for optimal performance.

Fourier transform ion cyclotron resonance cell with dynamic harmonization of the electric field in the whole volume by shaping of the excitation and detection electrode assembly

A new principle of formation of the effective electric field distribution in a Penning trap is presented. It is based on the concept of electric potential space averaging via charged particle cyclotron motion. The method of making hyperbolic-type field distribution in the whole volume of a cylindrical Penning trap is developed on the basis of this new principal. The method is based on subdividing the cell cylindrical surface into segments with shapes producing quadratic dependence on axial coordinate of an averaged (along cyclotron motion orbit) electric potential at any radius of cyclotron motion. The cell performance is compared in digital experiments with the performance of a Gabrielse-type cylindrical cell with four compensation electrodes and is shown to be more effective in ion motion harmonization at higher cyclotron radii and axial oscillation amplitude.

高感度同軸対称鏡型電子エネルギー分析器の製作と評価，コインシデンス分光への応用

We have developed a coaxially symmetric mirror electron energy analyzer with a high sensitivity, which was originally proposed by Kai Siegbahn in 1997. The analyzer, however, had a weak point; i.e. the performance is degraded by disturbance of the electric field near the end plates. We have improved the point by adopting compensation electrodes. Simulation with SIMION 3D version 7.0 predicts that the energy resolution (E/ΔE, FWHM) would be 300 for a pointed electron source and a solid angle of 1.2 sr. This value is about 3 times as much as the predicted value for the cylindrical mirror analyzer (CMA) used in previous EICO apparatuses. The resolution of the electron energy analyzer was obtained at UVSOR BL-2B1 by measuring an Au : 4f photoelectron spectrum of a gold film. The actual energy resolution was evaluated to be 110-130. Some improvements and applications to coincidence spectroscopy are also described.

Construction and evaluation of an electron-ion coincidence apparatus using a large transmission coaxially symmetric mirror electron energy analyzer

We have developed an electron ion coincidence (EICO) apparatus using a coaxially symmetric mirror electron energy analyzer with a large transmission. The electron energy analyzer originally proposed by Kai Siegbahn in 1997 had a weak point that the performance is degraded by disturbance of the electric field near the end plates. We have improved this by adopting compensation electrodes. Simulation with SIMION 3D version 7.0 predicts that the energy resolution (FWHM) is E/Δ E=300 for a pointed beam and a solid angle of 1.2 sr. This value is about three times better than the predicted value for the cylindrical mirror analyzer (CMA) used in the previous EICO apparatus. The measured electron energy resolution is E/Δ E=120 for a beam size of 2 mm×1 mm, which is about 1.5 times better than that for the previous CMA. Auger electron photoion coincidence measurement of condensed H 2O at 4 a 1←O 1s resonance showed that the measurement time required for a certain coincidence ion counts is reduced by one order of magnitude in comparison with the previous EICO.

Multiparameter miniaturised sensor arrays for multiple use

A family of electrochemical thick film sensors is presented which are suitable for different applications but are especially designed for the use in biological fluids. One sensor unit typically contains 4–6 different sensors for different analytes. The sensors show a fast response time of <30 s and a lifetime of up to several thousand samples. The sensors are maintenance free and exhibit good selectivity which can be increased by integrated interference compensation electrodes. Sensors for the following analytes have been developed to a stage where most of them are ready to use: sodium, potassium, ionised calcium, ionised magnesium, chloride, pH, pO 2, pCO 2, glucose, lactate, urea, creatinine.

Individual addressing and state readout of trapped ions utilizing rf micromotion

A new scheme for the individual addressing of ions in a trap is described that does not rely on light beams tightly focused onto only one ion. The scheme utilizes ion micromotion that may be induced in a linear trap by dc offset potentials. Thus coupling an individual ion to the globally applied light fields corresponds to a mere switching of voltages on a suitable set of compensation electrodes. The proposed scheme is especially suitable for miniaturized rf (Paul) traps with typical dimensions of about 20-40 microns.

Laser Cooling of Single 174Yb+ Ions Stored in a RF Trap

We demonstrate laser cooling of single 174Yb+ ions stored in a rf trap. Single 174Yb+ ions were loaded using a natural isotope mixture as source. To locate a single ion at the center of the trap, and consequently, to minimize the micromotion caused by the rf driving field, we introduced two compensation electrodes and applied dc voltages to them and to one of the endcap electrodes. We estimated the temperature of a trapped single 174Yb+ ion to be 150 mK from the residual Doppler width of the spectra observed by a frequency sweep of the cooling laser. In the estimation, the saturation broadening in the spectra was substituted by measurement of the power dependence of the spectral width. To count the number of trapped 174Yb+ ions, we detected sudden drops in the fluorescence intensity (quantum jumps) of individual ions caused by pumping to and deexcitation of the 2F7/2 state. We found that deexcitation of the 2F7/2 state is possible by driving the 2F7/2–1D[3/2]3/2 transition at 760 nm and the 2F7/2–3D[9/2]7/2 transition at 828 nm, in addition to the former methods of driving the 2F7/2–1D[5/2]5/2 transition at 639 nm and the 2F7/2–2D5/2 transition at 3.43 µm.

Cylindrical Penning traps with dynamic orthogonalized anharmonicity compensation for precision experiments

Harmonic potentials can be produced in cylindrical ion traps by means of dynamic orthogonalized anharmonicity compensation with use of two (or multiple) sets of compensation electrodes. One special example is for traps with multiple identical electrodes which are not only easy to construct and allow access to the center region of the trap for particle loading and releasing, laser beams, and microwaves, but also flexible in forming harmonic potential wells in many locations. The nested trap configuration and the side-by-side trap configuration are readily available in this special scheme. Analytical solutions for cylindrical traps with multiple sets of compensation potentials are presented. This work will be useful for studies involving Penning trap diagnostics, atomic and molecular interactions (including the production of antihydrogen atoms), accurate mass measurements of exotic particles, and precision measurements of the spin precession frequencies of trapped particles.

Open cell analog of the screened trapped-ion cell using compensation electrodes for Fourier transform ion cyclotron resonance mass spectrometry

The open cell collinear electrode geometry permits the inclusion of an auxiliary set of electrodes adjacent to the trap electrodes to perform several functions. Here they are used as compensation electrodes that virtually eliminate the radial electric field at the z = 0 midplane of the cell. The function of the compensation electrodes in reducing the radial electric field is analogous to the grounded transmissive screen inserted between the trap electrodes and the trapping volume in the closed screened cell whereby the interior of the cell is shielded from the trapping field. Segmenting the trap electrodes and applying oppositely biased potentials to each set of segments reduces the radial electric field at the z = 0 midplane of the cell by superposition of the opposing electric fields. In addition, dynamic adjustment of the potential well contour is performed by adjusting the relative potentials on each set of electrodes. The supplementary voltage applied to the inner set of compensation electrodes reduces the radial electric field by nearly two orders of magnitude and increases the potential well depth for greater ion capacity. In addition, the potential well assumes increased particle-in-a-box character without increasing the physical size of the cell, thereby reducing the effect of space charge. A FORTRAN program is developed that models the cell geometry and predicts the relationship between trap and compensation electrode voltage required to minimize the radial electric field throughout a specified cell volume. A theoretically optimum ratio of -0.33 V applied to the compensation electrodes for 1.0 V applied to the trap electrodes is predicted and is in close agreement with an experimentally determined optimum ratio of -0.36 V applied to the compensation electrodes for 1.0 V applied to the trap electrodes. This ratio reduces the cyclotron frequency shift from -70.8 Hz V -1 in an uncompensated open cell to -0.50 Hz V -1, a reduction of more than 99%. The radial electric field at the z = 0 midplane of the cell and 90% of the cell radius is reduced 97%, from 0.0139 V mm -1 to 0.0004 V mm -1. The reduction in frequency shift is accomplished without compromising mass accuracy. By collisionally damping ions to the center of the cell, mass accuracy over a one-decade range (60–600 u) approaches the mass accuracy of the hyperbolic cell geometry.

Charge exchange between Xe 44+ and H 2 in an ion trap

Extracted Xe 44+ ions from an electron beam ion trap (EBIT) have been decelerated and captured in a cylindrical Penning trap. The voltage induced between the compensation electrodes by the axial ion oscillation is used to measure charge exchange rate coefficients from H 2 to Xe 44+ at low energies and the resistive cooling time constant as well. The experimentally determined reaction rates are found to be in reasonable agreement with the Langevin model for charge exchange.

Coaxial-resonator-driven rf (Paul) trap for strong confinement.

We describe a variant of the quadrupole rf (Paul) ion trap capable of localization of a trapped ion to much less than an optical wavelength (Lamb-Dicke regime). The trapping potentials are generated by a high-Q, vacuum-compatible, quarter-wave resonator driven at about 240 MHz. The binding strength of the trap has been characterized. The trap contains compensation electrodes which allow the cancellation of stray static electric fields within the trap. Secular frequencies of tens of megahertz have been achieved for trapped magnesium and beryllium ions.

Cylindrical Penning traps with orthogonalized anharmonicity compensation

Compensated Penning traps with cylindrical ring and compensation electrodes and flat endcaps are considered as alternatives to high precision traps with hyperbolic ring and endcap electrodes. Cylindrical and flat electrodes can be more easily and precisely constructed, especially for the very small traps which are desirable for ion trapping. They are easily studied since Laplace's equation can be solved by a series expansion which is discussed in most electricity and magnetism textbooks. A central new result is that a judicious choice of the height-to-diameter ratio for a cylindrical trap makes the axial oscillation frequency of a trapped particle independent of adjustments in the compensation potential, just as has been recently proposed for hyperbolic traps. Other properties of such orthogonalized cylindrical traps appear to be adequate for particle trapping so that properly designed cylindrical traps are promising alternatives for high precision work, ready for laboratory testing. Whether or not cylindrical traps will be able to replace hyperbolic traps entirely for the highest precision work, a major point of this paper is that orthogonalized traps can be built with any reasonable electrode geometry. Special access traps with orthogonalized anharmonicity compensation are thus completely feasible, though numerical calculations will be generally required for their design.

Relaxation calculation of the electrostatic properties of compensated Penning traps with hyperbolic electrodes

Spectacular accuracies have been achieved with single elementary particles trapped in hyperbolic Penning traps, but only after anharmonicities have been tuned out of these traps by varying the potential of extra compensation electrodes introduced into the traps. The relaxation calculation reported here is the first theoretical study of the electrostatic properties of such compensated Penning traps. Enough computations have been completed to clarify the basic physics involved in anharmonicity compensation and to provide useful, quantitative information for experiments in progress (especially for testing of anharmonicity systematics). The clearer picture of anharmonicity compensation which emerges suggests that the design of existing Penning traps could be significantly improved. An optimal electrode configuration is proposed which, in principle, makes the harmonic oscillation frequency of a trapped particle independent of changes in the compensation potential.