Note: Measuring capacitance and inductance of a helical resonator and improving its quality factor by mutual inductance alteration (original) (raw)

Studies and development of a helical resonator for Penning trap application

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2020

A high quality factor helical resonator is required for the non-destructive resonant detection of eigenfrequencies of charged particles confined in a Penning trap. A 20 MHz helical resonator has been designed utilizing both the analytical and numerical methods. The performance of the helical resonator has been studied extensively by varying its dimensions and properties of the materials. The design parameters have been optimized and a prototype resonator is fabricated. The important parameters of the resonator like resonance frequency, quality factor, effective inductance and capacitance have been measured. The results obtained from the finite element analysis method are in good agreement with the experimentally measured values. It has been found that the distance between the radiofrequency probe and the open end of the helix plays an important role in maximizing the power coupling between the input and output terminals. Simulation studies have been performed to study the variation of power coupling with the change in the length of the probe and its radial position inside the resonator. The results have been verified experimentally. The maximum power coupling has been obtained by varying the length of the probe, where the resonance frequency and Q-factor were kept nearly same as the unloaded condition. The tank circuit with increased power coupling can be utilized to detect the feeble trap signal with high quality factor.

Ion storage in a radio-frequency trap with semi-spherical electrodes

International Journal of Mass Spectrometry and Ion Physics

The theory of the ion motion in a radio-frcqucncy quadrupolc ion trap with rlcctrodcs of semi-spherical cross-sections is clevelopcd. The radii of the electrode surfaces of the ion trap are chosen such that, at the same inter-electrode spacing, the resultant potential distribution near the center of the trap is closest to that of an idcal ion trap with hypcrbolic electrodes. It is found that the optimum values of the radii are 2.6Ozc and 0.55r0 for the end-cap electrodes and the ring electrode, rcspcctivcly, where zc and rn arc the characteristic dimensions of the ion trap. The diagram of stability is given. The effect of higher-order multigolc terms on the ion motion secular frequency is cstimatcd. These results arc compared with the storage properties of an ideal hyperbolic quadrupole ion trap.

Parametric excitations of trapped ions in a linear rf ion trap

Physical Review A, 2002

The parametric resonant behavior of ions inside a linear rf ion trap is studied both theoretically and experimentally. Theoretically, the resonant motion of ions inside an ideal ion trap is described by approximating the trapping rf field as a harmonic pseudopotential with the ions being excited by an additional quadrupolar ac voltage. The resulting damped Mathieu equation is studied and the regions of resonant instability are predicted by investigating the solutions. Experimentally, the parametric excitation of Mg ϩ ions is observed by subjecting the cloud of trapped ions to an additional quadrupolar ac field. The various ion motion resonances are detected through the disappearance of the laser-induced fluorescence signal. Weak damping is introduced by the presence of a low-pressure buffer gas. The experimental results are compared with the theoretical predictions.

Electronic Detection of Ions in an RF Trap

Confining charged particles may have been a relatively recent technique developed in research, but has grown to influence many areas of modern science, particularly that of mass spectrometry. This investigation aimed to look into the theory of how ions are trapped, and then attempted to non-destructively observe such ions inside an RF (Paul) trap using electronic detection. This method of detection is an alternative to the modern standard, which requires high-precision laser alignment in order to detect atomic fluorescence. It can be employed easily, adjusted effortlessly mid-experiment, and importantly, does not require additional atomic interactions. This report details the simulation, construction and testing of such an electronic ‘tank’ circuit, and although no conclusive data could be drawn from this particular investigation, there are indications that with improvements to the setup, a positive result could be obtained in the future.

Successive Resonances for Ion Ejection at Arbitrary Frequencies in an Ion Trap

The use of successive resonances for ion ejection is demonstrated here as a method of scanning quadrupole ion traps with improvement in both resolution and sensitivity compared with single frequency resonance ejection. The conventional single frequency resonance ejection waveform is replaced with a dual-frequency waveform. The two included frequencies are spaced very closely and their relative amplitudes are adjusted so that the first frequency that ions encounter excites them to higher amplitudes where space charge effects are less prominent, thereby giving faster and more efficient ejection when the ions come into resonance with the second frequency. The method is applicable at any arbitrary frequency, unlike double and triple resonance methods. However, like double and triple resonance ejection, ejection using successive resonances requires the rf and AC waveforms to be phase-locked in order to retain mass accuracy and mass precision. The improved performance is seen in mass spectra acquired by rf amplitude scans (resonance ejection) as well as by secular frequency scans.

New Schemes for resonant ejection in r.f. quadrupolar ion traps

International Journal of Mass Spectrometry and Ion Processes, 1990

In order to achieve relative ion number measurement with the best possible accuracy, a systematic investigation of ion detection by resonant ejection has been performed. The first experiment is described here. Ions stored in a radiofrequency quadrupole trap were subjected, for a short time, to a sinusoidal voltage of small amplitude, the frequency of which was variable from zero to half of the r.f. drive frequency. This pulse, of duration 10 ms, was applied to the trap electrodes in either the dipolar or quadrupolar mode. The signal formed by ions ejected out of the trap was observed at two different times which permitted differentiation of ion ejection along the z direction from combined ion ejection along the x, y and z directions. As the frequency composition of the pulse is swept through the above range, the observed ion signals show absorptions at secular frequencies w,~, w:, doubled frequencies, and combinations of w, and w;. These lines show anharmonicities and space charge perturbation. The second experiment attempts to analyze the effect of an initial pulse (or tickle) of a fixed frequency with a second pulse, the frequency of which is variable as described above, in order to explore the spectrum of ion motion under the influence of this tickle.

A Radio Frequency Helical Deflector for keV Electrons

Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment

This paper describes a helical deflector to perform circular sweeps of keV electrons by means of radio frequency fields in a frequency range 500-1000 MHz. By converting the time dependence of incident electrons to a hit position dependence on a circle, this device can potentially achieve extremely precise timing. The system can be adjusted to the velocity of the electrons to exclude the reduction of deflection sensitivity due to finite transit time effects. The deflection electrodes form a resonant circuit, with quality factor Q in excess of 100, and at resonance the sensitivity of the deflection system is around 1~mm per V of applied RF input.

The Helical Resonator: A Scheme for Radio Frequency Plasma Generation

Applied Sciences

The helical resonator is a scheme for the production of high voltage at radio frequency, useful for gas breakdown and plasma sustainment, which, through a proper design, enables avoiding the use of a matching network. In this work, we consider the treatment of the helical resonator, including a grounded shield, as a transmission line with a shorted end and an open one, the latter possibly connected to a capacitive load. The input voltage is applied to a tap point located near the shorted end. After deriving an expression for the velocity factor of the perturbations propagating along the line, and in the special case of the shield at infinity also of the characteristic impedance, we calculate the input impedance and the voltage amplification factor of the resonator as a function of the wave number. Focusing on the resonance condition, which maximizes the voltage amplification, we then discuss the effect of the tap point position, dissipation and the optional capacitive load, in terms...