Radio Frequency Electric Field Research Articles

Dissociation Kinetics in Quadrupole Ion Traps: Effective Temperatures under Dipolar DC Collisional Activation Conditions.

Ions stored in an electrodynamic ion trap can be forced from the center of the ion trap to regions of higher radio frequency (RF) electric fields by exposing them to a dipolar DC (DDC) potential applied across opposing electrodes. Such ions absorb power from the trapping RF field, resulting in increased ripple motion at the frequency of the trapping RF. When a bath gas is present, ions undergo energetic collisions that result in "RF-heating" sufficient to induce fragmentation. DDC is therefore a broad-band (i.e., mass-to-charge-independent) means for collisional activation in ion traps with added bath gas. Under appropriate conditions, the internal energy distribution of an ion population undergoing dissociation can be approximated with an effective temperature, Teff. In such cases, it is possible to determine thermal activation parameters, such as Arrhenius activation energies and A-factors, by measuring dissociation kinetics. In this work, the well-studied thermometer ion, protonated leucine enkephalin, was subjected to DDC activation under rapid energy exchange conditions and in two separate bath gases, N2 and Ar, to measure Teff as a function of the ratio of DDC and RF voltages. As a result, an empirically derived calibration was generated to link experimental conditions to Teff. It was also possible to quantitatively evaluate a model described by Tolmachev et al. that can be used to predict Teff. It was found that the model, which was derived under the assumption of an atomic bath gas, accurately predicts Teff when Ar was used as the bath gas but overestimates Teff when N2 was the bath gas. Adjustment of the Tolmachev et al. model for a diatomic gas resulted in an underestimate of Teff. Thus, use of an atomic gas can provide accurate activation parameters, while an empirical correction factor should be used to generate activation parameters using N2.

Combining computer aided food engineering and electro-heating applications as contribution to food processing sustainability

Can the combination of computer aided food engineering and electro-heating applications contribute to food processing sustainability? To what United Nations Sustainable Development Goal (SDG) this combination could contribute? Those are the questions addressed in this perspective. SDG7 is aimed to ensure the access to affordable, reliable, and sustainable and modern energy for all. According to World Bank, ensuring access to modern food cooking solutions is a key component to achieving for SDG7, and -since cooking is mainly based on heating processing- also the access to modern food heating solutions must be considered as a key component to achieving for SDG7. Electro-heating applications (EHA) in food processing include all processes using the interaction of a food material or product with an electromagnetic field, as in microwave, radio-frequency, and moderate electric fields processing. These technologies involve the use of electrical and -more recently- electronic circuits and require professional figures in their design. As result, the installation cost of these technologies is way higher than installation cost for heating processes using fossil sources, as fuel for fire boilers, as an example. Furthermore, at industrial level, these technologies may require ad-hoc design. Consequently, the food processing industry is quite slow in embracing such technologies along the productive lines. Computer aided food engineering (CAFE) has been recognized as valuable approach to shifts the paradigm from trial-and-error-based design to model-based design, using digital tools for the virtual representation of a food product or process, predicting the behavior of it. The combination of CAFE and EHA is the only way to help the food industry to embrace sustainability in most operations in which the heat transfer is involved. This paper presents a viewpoint on the challenges and opportunity to combine CAFE and EHAs as contribution to food processing sustainability.

Laser cooling of trapped ions in strongly inhomogeneous magnetic fields

Hybrid traps for the simultaneous confinement of neutrals and ions have recently emerged as versatile tools for studying interactions between these species at very low temperatures. Such traps rely on the combination of different types of external fields for the confinement of either species raising the question of interactions between the individual traps. Here, the influence of a strongly inhomogeneous magnetic field used for trapping neutrals on the trapping and laser cooling of a single ion in a radiofrequency ion trap is studied theoretically using molecular-dynamics simulations based on multilevel rate equations. The inhomogeneous magnetic field couples the different components of the ion motion and introduces position-dependent Zeeman splittings. Nonetheless, laser cooling is still found to work efficiently as the ion samples different magnetic field strengths and directions along its trajectory. Offsetting the centres of the two traps generates a linear magnetic-field gradient so that multiple lasers are required to address the resulting range of Zeeman splittings in order to ensure efficient cooling. The present study yields detailed insights into the ion cooling dynamics in combined magnetic and radiofrequency electric fields relevant for the characterisation and optimisation of hybrid trapping experiments.

A comprehensive study on the electron cyclotron resonance effect in a weakly magnetized capacitively coupled RF plasma: experiment, simulation and modeling

The electron cyclotron resonance (ECR) effect in a weakly magnetized capacitively coupled radio frequency (RF) plasma was previously observed with optical emission spectroscopy (OES) in experiments and analyzed by particle-in-cell/Monte Carlo collision (PIC/MCC) simulations (Zhang et al 2022 Plasma Sources Sci. Technol. 31 07LT01). When the electron cyclotron frequency equals the RF driving frequency, the electron can gyrate in phase with the RF electric field inside the plasma bulk, being continuously accelerated like microwave ECR, leading to prominent increases in the electron temperature and the excitation or ionization rate in the bulk region. Here, we study further the basic features of the RF ECR and the effects of the driving frequency and the gas pressure on the RF ECR effect by OES and via PIC/MCC simulations. Additionally, a single electron model is employed to aid in understanding the ECR effect. It is found that the maximum of the measured plasma emission intensity caused by ECR is suppressed by either decreasing the driving frequency from 60 MHz to 13.56 MHz or increasing the gas pressure from 0.5 Pa to 5 Pa, which shows a qualitative agreement with the change of the excitation rate obtained in the simulations. Besides, the simulation results show that by decreasing the driving frequency the electron energy probability function (EEPF) changes from a convex to a concave shape, accompanied by a decreased electron temperature in the bulk region. By increasing the gas pressure, the EEPF and the electron temperature show a reduced dependence on the magnitude of the magnetic field. These results suggest that the ECR effect is more pronounced at a higher frequency and a lower gas pressure, primarily due to a stronger bulk electric field, together wih a shorter gyration radius and lower frequency of electron–neutral collisions.

Gold cluster encapsulated liposomes: theranostic agent with stimulus triggered release capability

Cancer is a major cause of death worldwide. Cancer-resistant to chemo or radiotherapy treatment is a challenge that could be overcome by a nanotechnology approach. Providing a theranostic nano-platform for different cancer treatment strategies could be revolutionary. Here we introduce a multifunctional theranostic nanostructure which has the capacity for improving cancer diagnosis and treatment through better chemo and radiotherapy and current x-ray imaging systems through co-encapsulation of a small gold cluster and anticancer drug doxorubicin. 2nm gold clusters represent good heating under radio frequency electric field (RF-EF) exposure and have been used for in vitro hyperthermia treatment of cancerous cells. Liposomal doxorubicin (169 ± 19.8nm) with gold clusters encapsulation efficiency of 13.2 ± 3.0% and doxorubicin encapsulation efficiency of 64.7 ± 0.7% were prepared and studied as a theranostic agent with a high potential in different cancer treatment modalities. Exposure to a radiofrequency electric field on prepared formulation caused 20.2 ± 2.1% drug release and twice decreasing of IC50 on colorectal carcinoma cells. X-ray attenuation efficiency of the liposomal gold cluster was better than commercial iohexol and free gold clusters in different concentrations. Finally, treatment of gold clusters on cancerous cells results in a significant decrease in the viability of irradiated cells to cobalt-60 beam. Based on these experiments, we concluded that the conventional liposomal formulation of doxorubicin that has been co-encapsulated with small gold clusters could be a suitable theranostic nanostructure for cancer treatment and merits further investigation.

In-vivo measurement of radio frequency electric fields in mice brain

With the development of novel technologies, radio frequency (RF) energy exposure is expanding at various wavelengths and power levels. These developments necessitate updated approaches of RF measurements in complex environments, particularly in live biological tissue. Accurate dosimetry of the absorbed RF electric fields (E-Fields) by the live tissue is the keystone of environmental health considerations for this type of ever-growing non-ionizing radiation energy. In this study, we introduce a technique for direct in-vivo measurement of electric fields in living tissue. Proof of principle in-vivo electric field measurements were conducted in rodent brains using Bismuth Silicon Oxide (BSO) crystals exposed to varying levels of RF energy. Electric field measurements were calibrated and verified using in-vivo temperature measurements using optical temperature fibers alongside electromagnetic field simulations of a transverse electromagnetic (TEM) cell.

A High-Efficiency Fiber-Coupled Rydberg-Atom Integrated Probe and Its Imaging Applications

Atomic sensing and electric field measurements based on the use of the all-optical electromagnetic induction transparency (EIT) spectrum of Rydberg atoms have attracted great interest due to the advantages of self-calibration, Le Système International d'unités traceability, and a broadband spectrum. At the same time, this methodology also promotes the development of atomic sensor technology. We present a novel high-efficiency Rydberg-atom radio-frequency (RF) electric (E) field integrated probe (Rydberg Field Probe or RFP). The high-efficiency RFP consists of a 10 mm cubic 133Cs vapor cell, a dichroic mirror, three collimating lenses, and three fibers. This system can be used to independently control two counterpropagating lasers passing through a vapor cell, easing the design effort. In addition, the overall system efficiency can reach a value of 40.4%, reducing the EIT power broadening doe conventional RFPs. Based on the designed high-efficiency RFP, near-field electric field measurement and imaging of a C-band horn antenna at 4.48 GHz are performed by using the resonant RF field of the 133Cs atomic Rydberg state at room temperature with a spatial resolution of λ/6. These results promote the development of atomic sensing technology and show great application potential for the measurement of measuring high-resolution radio frequency electric fields and arrays of RFPs.

Observed Reductions in the Infectivity of Bioaerosols Containing Bovine Coronavirus Under Repetitively Pulsed RF Exposure.

The purpose of the present study is to investigate the inactivation of bioaerosols containing Bovine Coronavirus, BCoV, under repetitively pulsed radio frequency (RF) electromagnetic exposure. These experiments were performed in a waveguide containing a flowing aerosol stream and were limited to a single RF waveform: ∼2 μs square envelope, 5.6 GHz, 4.8 kHz repetition rate. Aerosol streams were exposed to RF electric field amplitudes in the range of 41.9 +/-6.2 kV/m. Under laminar flow conditions, 75% of the total collected aerosol stream spends 0.85 seconds or less in the RF exposure region. Application of the RF waveform changed mean survival rate of the aerosolized BCoV by -0.58 decades (roughly a 74% reduction) and impacted the variance and standard deviation of the experimental results, with the RF exposure data showing an 800% increase in variance and 196% increase in standard deviation over the control results. Experimental results were compared to those from an analytic electromagnetic-heating inactivation model. The comparison indicated the feasibility that the observed reduction in BCoV survival rate might be due to a combination of thermal effects and non-thermal electric field effects. Developing better insight into the mechanisms of inactivation is important for understanding the potential limits of efficacy for this method. Additionally, these results contribute an important baseline for the impact of electromagnetic fields on aerosolized pathogens.

Radio-Frequency Electric Field Sensing Based on a Single Solid-State Spin

Nanoscale amplitude and phase sensing of a rf electromagnetic field can benefit broad frontiers in science and technology. The imaging applications in these research areas demand a nanoscale sensor able to detect rf electric fields over a wide frequency range under ambient conditions, which remains a challenge. Here, we present a rf electrometry based on the forbidden magnetic dipole transition of a single shallow nitrogen-vacancy center in diamond and experimentally demonstrate the detection of rf electric fields at frequencies ranging from 13.85 MHz to 2.02 GHz. A sensitivity of $265\phantom{\rule{0.2em}{0ex}}{\mathrm{V}\phantom{\rule{0.2em}{0ex}}\mathrm{cm}}^{\ensuremath{-}1}\phantom{\rule{0.2em}{0ex}}{\mathrm{Hz}}^{\ensuremath{-}1/2}$ for amplitude measurement and a standard deviation of ${0.2}^{\ensuremath{\circ}}$ for phase measurement are achieved. The potential applications of nanoscale sensing and imaging of electromagnetic field are discussed.

Dissociation of N2 by electron impact in electric and magnetic RF fields

Rate coefficients for electron impact dissociation of the N2 molecule under the influence of crossed radio-frequency (RF) electric and magnetic fields were calculated for field frequencies of 13.56, 100 and 200 MHz and for root mean square values of the reduced electric field strength of 300 and 500 Td. The root mean square values of the reduced magnetic field were varied from 0 to 2000 Hx. ?he effects of the strength of the RF fields and their frequency on the rates for the dissociation to neutral fragments and for the dissociative ionization are discussed. The temporal evolution of the rate coefficients during one period of the RF field is shown and discussed.

Radio Frequency Electric Field Measurement with Rydberg Atoms

Radio Frequency Electric Field Measurement with Rydberg Atoms

Development of low power and high voltage RF signal generator

Ion confinement technology can be widely used in quantum computation and precision measurement. In ion trapping system, ions are stably trapped in ion trap by the action of external forces.Multi-ion confinement requires the joint action of electric field and magnetic field to make the trapped ions overcome the interaction force between ions and be stably confined in the same specific space. Therefore, the stability of the electric force and the magnetic force determines the stability of ion confinement. Although the electric field and magnetic field provided by traditional commercial instruments is stable, it is not conducive to the miniaturization of the device. According to the previous experiment of ion confinement, we have designed a radio frequency(RF) signal generator that can provide continuous low power and stable high voltage RF electric field for multi-ion confinement system to guarantee the stability of trapped ions in quadrupole linear ion trap, also to improve the tapped ions density.

An investigation into the electro‐tolerance of Escherichia coli treated by radio frequency electric fields

AbstractBACKGROUNDRadio frequency electric field (RFEF) is a novel technology for the microbial disinfection of liquids such as water and fruit juices. Here we investigated the development of microbial tolerance against RFEF to assess the long‐term suitability of this technology. We applied a constant electric field, outlet temperature and treatment time of 14 kV cm−1, 40 °C and 1.275 ms, respectively, to Escherichia coli inoculated in saline water to observe whether the descendants of the surviving bacteria could develop tolerance against RFEF. Escherichia coli that survived the RFEF treatment were recultivated and treated under similar processing conditions for 15 generations.RESULTSThe results showed that although inactivation levels due to RFEF treatments fluctuated during consecutive generations, no significant difference between inactivation at cycles 1 and 15 was observed. Furthermore, inactivation levels during consecutive generations hovered around an average value of 2.18 CFU mL−1. For short‐term effect, which compared untreated cells to treated ones at cycle 1, proteomics showed mixed trends of up‐ and down‐regulated differentially expressed proteins (DEPs). However, in the long term, which compared treated cells at cycles 1 and 15, DEPs involved in stress response, cell wall structure and antioxidant activities were all up‐regulated.CONCLUSIONThe results indicate that although cell wall is the main target for the effect of electric field, they suggest that, in the long term, oxidative stress may also be induced. © 2022 Society of Chemical Industry (SCI).

Ultralow electron emission yield achieved on alumina ceramic surfaces and its application in multipactor suppression

Alumina ceramics used in microwave systems are susceptible to the multiplication of secondary electron emission on the surface due to the influence of resonance between electrons and the radiofrequency electric field, and a detrimental multipactor effect may therefore be triggered. For the alumina-loaded microwave components, it is essential to achieve low secondary electron yield (SEY) on the inserted alumina surfaces to mitigate multipactor. In this work, to achieve an ultralow SEY surface of alumina, two recognized low-SEY treatments were combined. For the primary SEY suppression, a series of microstructures were fabricated on the alumina surfaces with varied porosity and aspect ratio at the hundred-micrometer scale by infrared laser etching. The microstructure with 52.14% porosity and 1.78 aspect ratio showed an excellent low-SEY property, which could suppress the SEY peak value ( δ m ) of alumina from 2.46 to 1.00. For the secondary SEY suppression, the SEY dependence of TiN coating on sputtering parameters was studied, and the lowest δ m of 1.19 was achieved when the gas flow ratio of Ar:N2 was 15:7.5. Thereafter, by depositing TiN ceramic coating onto the laser-etched porous samples, an ultralow SEY, with δ m of 0.69, was achieved on the alumina surfaces. The simulation work revealed the impact of dielectric surface charge on electron multiplication and revealed a mechanism of using low-SEY surfaces to inhibit multipactor. Some coaxial filters filled with alumina were fabricated for verification; the results revealed that the multipactor threshold increased from 125 W to 425 W after applying the TiN-coated porous alumina, and to 650 W after treating another multipactor-sensitive area with the same low-SEY process. This work developed an advisable method to sharply reduce SEY, which is of great significance for the multipactor mitigation of alumina-loaded microwave components.

Origins of Rydberg-Atom Electrometer Transient Response and Its Impact on Radio-Frequency Pulse Sensing

Rydberg atoms show significant promise as the basis for highly sensitive detectors of continuous radio-frequency (rf) electric fields (E fields). Here, we study their time-dependent response to pulse-modulated rf E fields at 19.4 GHz using a cesium vapor cell at room temperature. We use density-matrix simulations to explain the timescales that shape the transient atomic response under different laser conditions, finding them to be limited by dephasing mechanisms, including transit-time broadening, Rydberg-Rydberg collisions, and ionization. Using a matched filter, we demonstrate the detection of individual pulses with durations from 10 \textmu{}s down to 50 ns and amplitudes from 15 000 \textmu{}V ${\mathrm{cm}}^{\ensuremath{-}1}$ down to about 170 \textmu{}V ${\mathrm{cm}}^{\ensuremath{-}1}$, corresponding to a sensitivity of about 240 nV ${\mathrm{cm}}^{\ensuremath{-}1}$ ${\mathrm{Hz}}^{\ensuremath{-}1/2}$. Finally, we highlight the potential of a Rydberg vapor cell as a receiver by detecting pulse trains from a rotating emitter on a simulated passing aircraft.

Electron–N2 interactions in RF E × B fields

This study reports on rate coefficient data for excitation of electronic states and ionization of N2 molecules by electrons exposed to mutually perpendicular radio frequency electric and magnetic fields. These quantities were obtained by means of a Monte Carlo simulation, which provides mean electron energies and corresponding energy distributions within one oscillation of the external fields. The time-resolved mean electron energies and rate coefficients as well as their period averaged values are presented. Calculations were performed for different field frequencies, including one of the standard frequencies in the industrial use, 13.56 MHz, and for effective reduced electric field values of 300 and 500 Td, while the effective reduced magnetic field was varied up to 2000 Hx. The fundamental aspect of the obtained results is discussed, which is followed by a collection of tabular data for their eventual use in future models of inductively coupled N2 plasma sources.

Quantum Shot Noise Limit in a Rydberg RF Receiver Compared to Thermal Noise Limit in a Conventional Receiver

Electromagnetically induced transparency in a vapor of Rydberg atoms can be used for radio frequency (RF) electric field sensing. Such sensors can be traceable, tunable, compact, and electrically passive. One application for these electric field sensors is as a receiver for RF communications, converting a 5G transmission in free space to a modulated optical signal in a fixed network. Different figures of merit are used for an electric-field sensor and a 5G receiver; so it is not straightforward to determine under which operating conditions a Rydberg RF receiver may outperform a conventional antenna and receiver. Here, we consider two fundamental limiting sources of noise, calculating the quantum shot noise limit in a Rydberg RF receiver and comparing this to the thermal noise limit in a conventional macroscopic receiver. For a typical experimental setup, we show that the quantum shot noise can only fall below the thermal noise floor when the symbol rate is below 1−2 MSymbol/s. Higher order signal modulation will be needed to further increase data rate whilst using this constrained symbol rate to limit the fundamental noise floor.

Enhanced heating in plasma bulk due to electron cyclotron resonance in weakly magnetized capacitively coupled plasmas

An enhanced electron heating mechanism based on a resonance between the cyclotron motion of electrons and radio frequency (rf) electric field in the plasma bulk is reported in weakly magnetized capacitively coupled argon plasmas at low pressure. When the electron cyclotron frequency coincides with the applied power source frequency, the bulk electrons can continuously acquire energy from the background electric field within certain rf periods during the cyclotron motion, inducing overall distinct increase of excitation rate and electron temperature in the plasma bulk. This enhanced electron heating effect has been examined by a combination of kinetic particle simulations, experimental measurements, and an analytical model, and the dynamics of electrons are revealed at resonant conditions.

Stability problem in 3D multipole ion traps

We suggest a concept of ion trapping in three-dimensional multipole electric fields. In this work, we propose a vibromechanical interpretation of an ion localization stability problem in a three-dimensional octupole radio-frequency electric fields and have made a transition to an equivalent autonomous dynamical system. The conditions for stable ion localization in three-dimensional octupole trap in radio-frequency-only-mode and mixed-mode are determined. The ion's effective potential for the mixed-mode is calculated and the coordinates of the stable quasi-equilibrium points are obtained. The sensitivity of the effective potential configuration to the polarity of the DC component is estimated. The ion's dynamics in an original and autonomous systems is considered, and a method for optimizing the shape of trap's electrodes is proposed.

Enhancing the Biological Activities of Food Protein-Derived Peptides Using Non-Thermal Technologies: A Review.

Bioactive peptides (BPs) derived from animal and plant proteins are important food functional ingredients with many promising health-promoting properties. In the food industry, enzymatic hydrolysis is the most common technique employed for the liberation of BPs from proteins in which conventional heat treatment is used as pre-treatment to enhance hydrolytic action. In recent years, application of non-thermal food processing technologies such as ultrasound (US), high-pressure processing (HPP), and pulsed electric field (PEF) as pre-treatment methods has gained considerable research attention owing to the enhancement in yield and bioactivity of resulting peptides. This review provides an overview of bioactivities of peptides obtained from animal and plant proteins and an insight into the impact of US, HPP, and PEF as non-thermal treatment prior to enzymolysis on the generation of food-derived BPs and resulting bioactivities. US, HPP, and PEF were reported to improve antioxidant, angiotensin-converting enzyme (ACE)-inhibitory, antimicrobial, and antidiabetic properties of the food-derived BPs. The primary modes of action are due to conformational changes of food proteins caused by US, HPP, and PEF, improving the susceptibility of proteins to protease cleavage and subsequent proteolysis. However, the use of other non-thermal techniques such as cold plasma, radiofrequency electric field, dense phase carbon dioxide, and oscillating magnetic fields has not been examined in the generation of BPs from food proteins.