Radiofrequency Generator Research Articles

Incremental high power radiofrequency ablation with multi-electrodes for small hepatocellular carcinoma: a prospective study

Radiofrequency ablation (RFA) offers a minimally invasive treatment for small hepatocellular carcinoma (HCC), but it faces challenges such as high local recurrence rates. This prospective study, conducted from January 2020 to July 2022, evaluated a novel approach using a three-channel, dual radiofrequency (RF) generator with separable clustered electrodes to improve RFA’s efficacy and safety. The study employed a high-power, gradual, stepwise RFA method on HCCs (≤ 4 cm), utilizing real-time ultrasound-computed tomography (CT)/magnetic resonance imaging (MRI) fusion imaging. Involving 110 participants with 116 HCCs, the study reported no major complications. Local tumor progression (LTP) and intrahepatic remote recurrence (IRR) rates were low, with promising cumulative incidences at 1, 2, and 3 years for LTP (0.9%, 3.6%, 7.0%) and IRR (13.9%, 20.5%, 31.4%). Recurrence-free survival (RFS) rates were similarly encouraging: LTP (99.1%, 96.4%, 93.0%) and IRR (86.1%, 79.5%, 68.6%). This innovative gradual, incremental high-power RFA technique, featuring a dual switching monopolar mode and three electrodes, represents an effective and safer management option for small HCCs.Trial registrationclinicaltrial.gov identifier: NCT05397860, first registered on 26/05/2022.

Microwave and Radiofrequency Ablation: A Comparative Study between Technologies in Ex Vivo Tissues

In this paper, we report on the use of a purpose-built hybrid solid-state microwave and radiofrequency generator operating at frequencies of 2.45 GHz and/or 480 kHz for cancer ablation in various tissues. The hybrid generator was tested ex vivo on chicken breast and bovine liver and has demonstrated that the high accuracy of the power delivered to the sample can be achieved by controlling the emitted power versus the temperature profile of the treated sample. In particular, the hybrid generator incorporates control systems based on impedance or reflected power measurements that allow controlled ablation without causing unwanted carbonization and without including areas where tissue damage is not desired. The results of the ex vivo tests showed that radiofrequency ablation (RFA) could be effective for performing controlled ablations with minimally invasive probes, such as cardiac pathologies, small lesions, and tissues with particular composition, while microwave ablation (MWA) could be optimal for performing large ablations in highly vascularized tissues, such as liver cancer, where it is necessary to achieve higher temperatures.

Void closure in a pulsed complex plasma in microgravity

A new experimental method for creating void-free complex (dusty) plasmas under microgravity conditions is presented. The method is based on a pulsed operation mode of a four-channel radio frequency generator for plasma sustainment. A dust cloud of micrometer-sized particles can be immersed in the bulk of a low temperature plasma under microgravity conditions. It typically contains a central volume depleted of particles—the void—that prevents the generation of large, continuous clouds. Experiments performed at different neutral gas pressures and discharge volumes during the microgravity phase of a parabolic flight show that the central void is closed completely once the pulsed operation mode is applied. The particle cloud shape and the density distribution within the cloud are practically independent of the pulse period within the investigated parameter range and mainly depend on the overall discharge parameters neutral gas pressure and discharge volume. This indicates that the pulsed operation of the plasma source does not introduce new physical effects on the particles aside from the void closure. The proposed method has great potential for future application in experimental facilities dedicated to fundamental studies of large three-dimensional, homogeneous complex plasma systems in microgravity.

A Wearable Real-Time System for Simultaneous Wireless Power and Data Transmission to Cortical Visual Prosthesis.

Wireless, miniaturised and distributed neural interfaces are emerging neurotechnologies. Although extensive research efforts contribute to their technological advancement, the need for real-time systems enabling simultaneous wireless information and power transfer toward distributed neural implants remains crucial. Here we present a complete wearable system including a software for real-time image capturing, processing and digital data transfer; an hardware for high radiofrequency generation and modulation via amplitude shift keying; and a 3-coil inductive link adapt to operate with multiple miniaturised receivers. The system operates in real-time with a maximum frame rate of 20 Hz, reconstructing each frame with a matrix of 32 × 32 pixels. The device generates a carrier frequency of 433.92 MHz. It transmits the highest power of 32 dBm with a data rate of 6 Mbps and a variable modulation index as low as 8 %, thus potentially enabling wireless communication with 1024 miniaturised and distributed intracortical microstimulators. The system is primarily conceived as an external wearable device for distributed cortical visual prosthesis covering a visual field of 20 °. At the same time, it is modular and versatile, being suitable for multiple applications requiring simultaneous wireless information and power transfer to large-scale neural interfaces.

Research on Construction of Test Environment for Assessment of RF-Induced Heating Effects of Implants

In magnetic resonance examination, the interaction between implants and the radio frequency (RF) fields induces heating in human tissue and may cause tissue damage. To assess the RF-induced heating of implants, three steps should be executed, including electromagnetic model construction, electromagnetic model validation, and virtual human body simulations. The crucial step of assessing RF-induced heating involves the construction of a test environment for electromagnetic model validation. In this study, a hardware environment, comprised of a RF generation system, electromagnetic field measurement system, and a robotic arm positioning system, was established. Furthermore, an automated control software environment was developed using a Python-based software development platform to enable the creation of a high-precision automated integrated test environment. The results indicate that the electric field generated in this test environment aligns well with the simulated electric field, making it suitable for assessing the RF-induced heating effects of implants.

Real-time characterization of radiofrequency lesions by local multifrequency impedance with thermal correction

Abstract Background/Introduction Recent studies have shown that measuring local impedance (LI) at a single frequency can be useful for real-time characterization of radiofrequency (RF) lesion size during arrhythmia ablation procedures. (1) However, these systems do not take into account the effect of the increase in tissue temperature on the impedance measurement itself, which could be avoided by comparing the impedance at different frequencies. Purpose The aim of this study was to evaluate the ability of local multifrequency impedance (LMI) to characterize the size of RF lesions in real-time, while correcting for the thermal effect on the measurement. Methods Lesions were performed on the epicardium in 5 anesthetized pigs while measuring IML (from 1 to 209 kHz) before, during, and after ablations (20W/30W/40W, 60s, >10g) through a conventional irrigated electrocatheter connected to a cardiac navigation system and a RF generator. In these measurements, the thermal effect on the tissue was corrected by assuming that the changes in impedance at high frequency were only due to the temperature variation and not to the injury itself. Local voltage (Vuni) was also measured before and after ablations, and catheter-measured temperature and contact force were monitored. At the end of the procedure, the animals were sacrificed, and a histological study of the lesions was performed. Results A total of 43 effective lesions (11±2 per animal) were performed. The 40W lesions were deeper and wider than the 20W lesions (6,6 ± 3,3 mm vs. 5,4 ± 2,0 mm vs. 4,0 ± 1,9 mm; ANOVA p<0.05) and presented a significant decrease in unipolar voltage that was similar among the different lesions (40W vs. 20W: 56% vs. 40%; ANOVA p=ns; Figure). Four seconds after the start of the ablation the 40W lesions had a greater decrease in IML than the 30W and 20W lesions (73±14Ω vs. 85±4Ω vs. 100±12Ω; ANOVA p<0.05). After thermal adjustment, IML recorded 30 and 55 seconds after the start of the ablation correlated better with the final depth of the lesion than IL or Vuni (Table). Conclusions The measure of IML during ablation allows a better quantification of the changes in the structural characteristics of myocardial tissue than local impedance at a single frequency. The increase in tissue temperature during ablation influences the values of local impedance and should be considered when creating new impedance-based metrics to predict the chronic size of the RF lesion.Figure.Lesion quantification by LMITable.Correlation analysis

Boosting radio frequency radiation with collisional processes in picosecond laser filamentation

When focused in air, ultrashort pulse lasers generate a plasma that produces ultrabroadband radio frequency (RF) radiation via both ponderomotive and plasma wake field current mechanisms. We have performed experiments with high energy pulses and pulse durations up to 5 ps, while holding the power constant. These longer pulses drive much higher electron densities and temperatures, especially as collisional processes become important, and we in turn have measured substantially increased RF generation. We have also developed a Drude numerical model of the ionization within the laser pulse, the heating due to collisions, and the ensuing current density evolution. We find that the low frequency scaling of the simulated current matches the experimental data, which indicates that the ponderomotive currents dominate the RF generation for these atmospheric pressure plasmas. However, the experimentally measured spectra also show an additional low frequency (1–10 GHz) component that grows with laser pulse length, which is consistent with the plasma wake surface wave RF also becoming important as the plasma temperature approaches 100 eV.

Laser and radio frequency technologists in the treatment of degenerative polysegmental pathologies of the spine in elderly people

The article discusses outcomes after treating 88 elderly patients with degenerative pathologies of the spine, 42 of whom had previous decompression- stabilizing surgical interventions. Clinical manifestations of the disease were characterized by prolonged pain syndrome, lumboishialgia caused by degenerative-dystrophic changes in the arch-process joints and progressive degeneration of the intervertebral discs. Surgical intervention in 65 patients included puncture laser ablation of the medial branch of the spinal nerve in the facet joint. In 23 patients, ablation of the medial branch of the spinal nerve was performed at two (n = 8) and three (n = 15) levels using four-channel radio frequency generator COSMAN G4.Excellent and good results after surgery were found in 58 (65.9%) patients. The researchers assessed intermediate results within 3 years in 55 patients, and 37 (42.01%) of them had a stable positive state. Minimally invasive laser and radiofrequency technologies in the treatment of degenerative polysegmental pathologies of the spine in elderly and old people is justifi ed, and it is an important component of their rehabilitation

Bipolar catheter ablation with dedicated radiofrequency system for highly refractory ventricular arrhythmia-Does the rate of success depend on arrhythmia origin?

Despite rapid technological progress, some arrhythmias are still resistant to standard unipolar ablation. These include arrhythmias arising from the base of the heart, cardiac crux, or epicardium. Bipolar radiofrequency ablation (B-RFA) may be useful in some cases, however, data on the efficacy of this approach in various arrhythmia localizations are scarce. The aim of this study was to assess the efficacy of B-RFA in patients with ventricular arrhythmias originating from various locations, occurring refractory to standard unipolar ablation approaches. An observational, single center study was conducted over a 30-month period. B-RFA were performed using dedicated radio frequency (RF) generator and electroanatomic mapping system. Twenty-four procedures, in 23 patients with a median (range) of 1 (1-2) previously failed unipolar ablation procedures, were included in the final analysis. There were 12 ablations of ventricular arrhythmias originating from interventricular septum with an acute success rate of 75%, and 12 from left ventricular (LV) summit with an acute success rate of 58%. The midterm success rate (medianinterquartile range follow-up of 205 days [188-338]) was 66% and 50%, respectively. B-RFA is a promising method of catheter ablation for refractory cardiac arrhythmias. A higher success rate was observed in ablation for difficult ventricular arrhythmias originating from interventricular septal region than LV summit.

A fully integrated nanosecond burst RF generator for quantum technologies

AbstractQuantum technologies is an emerging field of physics and engineering based on exploiting properties of quantum mechanics such as entanglement, superposition, or tunneling, and which is expected to impact many applications, such as communications, simulation, computation, or sensing and metrology. The operation of quantum technologies is based on the manipulation of the quantum states of certain devices, either to induce transitions between states or to detect the transitions. Irrespective of the practical realization of these quantum devices, their manipulation requires interacting with their quantum resonant states, for which very narrow radio‐frequency (RF) bursts in the range of the GHz are required. Arbitrary waveform generators are used to generate these signals for test purposes, but this is not suitable for practical quantum technology applications, which will need to produce the required bursts by specific circuit building blocks with low power and small dimensions. Here, an integrated RF burst generator capable of producing GHz bursts shorter than 1 ns is presented. The proposed architecture is tested using a 5 GHz quadrature LC‐tank voltage‐controlled oscillator (LC‐VCO), showing that the four equally spaced phases can be switched every 500 ps, which allows the generation of more complex RF bursts for optimized quantum state manipulation.

Evaluation of Lumbar Adhesiolysis Using a Radiofrequency Catheter During Epiduroscopy in the Treatment of Failed Back Surgery Syndrome (FBSS).

Failed back surgery syndrome (FBSS) is a complication of spinal surgery that results in severe and disabling back/leg pain. Epiduroscopy is a percutaneous minimally invasive surgical technique used in the treatment of lumbar radicular pain that enables both direct visualization of epidural adhesions in patients with FBSS and the mechanical release of fibrotic scars in the epidural space. Although the use of a balloon catheter during epiduroscopy can usually remove adhesions between the dura and the vertebrae, in the thickest areas of fibrosis, the use of a catheter with a molecular quantum resonance radiofrequency generator may resect hard epidural fibrotic obstructions. The aim of this study was to evaluate the efficacy and safety of this radiofrequency catheter in the treatment of severe epidural fibrotic scars. Ninety-three patients with FBSS were enrolled in this study. In 49 cases, a thick area of fibrosis was visualized during epiduroscopy and the use of a balloon catheter could not remove the fibrotic scars. In all of these cases, we used a molecular quantum resonance radiofrequency catheter to remove dense fibrotic areas. Intraoperatively during epiduroscopy, we could directly visualize lysis of the fibrotic scars. Immediately after the procedure and at 1-month and 6-month follow-up, the patients reported significant pain reduction. Pain reduction and patient satisfaction were also reported at 12 months in all but 5 cases. This study found a clinically relevant reduction of pain at 1 and 6 months after epiduroscopy in patients with FBSS. The use of a radiofrequency catheter is safe and effective in resection of hard and thick epidural scars.

Efficacy and safety aspects of renal denervation in treatment of arterial hypertension: a systematic review and meta-analysis

Abstract Introduction Current guidelines for the management of arterial hypertension 2018 of European Society for Cardiology (ESC) do not recommend use of renal denervation (RDN) (as device-based therapy) for treatment of hypertension except as part of clinical studies. However, in the meantime several randomized sham-controlled clinical trials were designed using second generation radiofrequency (RF) (SPYRAL HTN-OFF MED, SPYRAL HTN-ON MED), ultrasound (RADIANCE-HTN SOLO, RADIANCE-HTN TRIO) or alcohol-mediated renal denervation (TARGET BP-OFF) devices. We aimed to perform a comprehensive meta-analysis from all published and unpublished randomized, sham-controlled clinical trials which explored the effects of renal denervation on blood pressure across different devices. Methods We searched MEDLINE and Embase via OVID@ for eligible trials. Of note, we also included unpublished data from the SPYRAL-ON Extension and TARGET BP OFF trials. Pooling the data from all studies, we explored the efficacy (ambulatory and office systolic and diastolic BP) and safety (all cause death, vascular complication, renal artery stenosis >70%, hypertensive crisis) of RDN. Results Analysis included 9 eligible trials (i.e. SYMPLICITY HTN-3, ReSET, SPYRAL HTN OFF MED, Desch et al., RADIANCE-HTN SOLO, RADIANCE-HTN TRIO, RADIANCE, TARGET BP OFF, SPYRAL HTN ON MED extension) comprising 2,091 patients (Table 1). RDN reduced ambulatory systolic (-3.10 mmHg, 95% CI -4.22, -1.97, p<0.00001) and office systolic (-5.15 mmHg, 95% CI -6.65, -3.66, p<0.00001) BP and ambulatory diastolic (-1.58 mmHg, 95% CI -2.54, -0.63, p=0.001) and office diastolic (-2.74 mmHg, 95% CI -3.65, -1.83, p<0.00001) BP compared with sham groups. There was no difference concerning ambulatory SBP reduction between trials with ON medication design (-2.94 mmHg, p<0.0001) and those with OFF medication design (-3.37 mmHg, p<0.0001) (p for interaction 0.69). Similarly, office SBP reduction was comparable between trials with (-4.38 mmHg, p<0.0001) and without concomitant antihypertensive drugs prescription (-6.27 mmHg, p<0.00001) (p for interaction 0.22). The rate of vascular complications (OR 1.21, 95% CI 0.28, 5.25, p=0.80), renal artery stenosis (OR 1.50, 95% CI 0.06, 36.97, p=0.80), hypertensive crisis (OR 1.39, 95% CI 0.50, 3.92, p=0.53) and all cause death (OR 0.52, 95% CI 0.10, 2.83, p=0.45) was not different between treatment and sham groups. Conclusions RDN is associated with clinically significant reductions in ambulatory and office SBP as compared with sham in the presence and absence of antihypertensive medication. The procedure use was not associated with an excess in safety events compared with sham group.

Abstract 15366: Quantification of Recent Reporting Rates of Atrioesophageal Fistula After Left Atrial Ablation for the Treatment of Atrial Fibrillation

Introduction: Atrio-esophageal fistulas (AEF) are a feared and fatal complication of left atrial ablation for the treatment of atrial fibrillation (AF). The recent POTTER-AF survey suggests that AEFs continue to occur despite best efforts to prevent them. A quantification of recent incidence rates and outcomes of AEF reported to the Manufacturer and User Facility Device Experience (MAUDE) database of the U.S. FDA may further elucidate trends in this complication. Research Question(s): What are the recent trends in reporting rates of AEF, and what are the outcomes? Purpose: To quantify the number of AEF reports as well as any reported outcomes of atrioesophageal fistulas and determine any trends over the last 4 years. Methods: We reviewed data from the Manufacturer and User Facility Device Experience (MAUDE) database for complications under the category of fistula that occurred over the last 4 years (2019 to 2022 inclusive). Reports were reviewed for any descriptions of outcome, and narratives were compared in an attempt to identify and exclude any duplicate reporting. Results: In total, three product codes resulted in 121 reported AEFs. Of these, 50 (41%) were listed as fatal. When provided, the time frame of death ranged from 12 days to several weeks after the index procedure. Product codes reporting AEFs included LPB (88 cases), OAE (22 cases), and OAD (11 cases), with codes representing cardiac ablation catheters and radiofrequency generators. Incidence by year showed a generally increasing trend (21 in 2019, 22 in 2020, 41 in 2021, and 37 in 2022, Figure 1). Conclusion: The annual rate of reported AEFs has not decreased over the last 4 years, and instead shows a generally increasing trend. Reported fatality rates remain high at 41%.

Obstetric outcome after ultrasound guided transvaginal radiofrequency ablation of uterine myomas

Purpose: The objective is to report the obstetric outcome of 8 pregnancies with uterine fibroids who conceived after RFA. Methods: A study was conducted on 115 women with symptomatic uterine fibroids undergoing transvaginal RFA using a bipolar radiofrequency generator and an internally cooled electrode. Data on pregnancies and outcomes were collected. Results: After the procedure, eight pregnancies occurred. Fibroid volume reduction exceeded 50% in half of the patients, with an average reduction rate of 43%. Six resulted in live births, with a cesarean section rate of 2/3, one in an ectopic pregnancy, and one in a miscarriage. Pregnancy complications were limited, and all newborns showed normal development. Conclusion: Minimally invasive ultrasound-guided RFA is effective in shrinking the myomas and may not carry an obstetric risk. Although the number of reported cases is low, no obstetric complications specifically associated with transvaginal radiofrequency ablation of uterine fibroids have been observed.

Comparison of transseptal puncture using a dedicated RF wire versus a mechanical needle with and without electrification in an animal model.

Mechanical force to achieve transseptal puncture (TSP) using a standard needle may lead to overshooting and injury, and can potentially be avoided using a radiofrequency (RF)-powered needle or wire. Applying electrocautery to needles and guidewires as an alternative to purpose-built RF systems has been associated with safety risks, such as tissue coring and thermal damage. The commercially available AcQCross needle-dilator system (Medtronic) features a sharp open-ended needle for mechanical puncture, as well as a built-in connector to enable energy delivery for RF puncture. This investigation compares the safety and efficacy of the AcQCross needle to the dedicated VersaCross RF wire system and generator (Baylis Medical/Boston Scientific). In an ex vivo porcine model, VersaCross wire punctures were performed using 1 s, constant mode (approx. 10 W) with maximum two attempts. AcQCross punctures were performed by applying energy for 2 s using a standard electrosurgical generator at 10 W (max. five attempts), 20 W (max. two attempts), and 30 W (max. two attempts). Efficacy was assessed in terms of puncture success and a number of energy applications required for TSP. Safety was assessed quantitatively as force required for TSP, energy required to puncture, and incidence of tissue coring, as well as by qualitative assessment of puncture sites. Additional qualitative observation of tissue cores and debris were obtained from TSP performed in live swine. RF TSP was 100% successful using the VersaCross wire with 1.0 ± 0.0 attempts. When power was used with the AcQCross needle, it failed to puncture at low (10 and 20 W) power settings; TSP was achieved with 30 W of energy with 91% success using 1.53 ± 0.51 attempts (p < .05 vs. VC) with greater variability (F1,33 = 9223.5, p < .0001). Compared to RF puncture using the VersaCross system, mechanical puncture, alone, using the AcQcross needle required six times more force (8 mm additional forward device displacement) to perforate the septum. Qualitative assessment of puncture sites revealed larger defects and more tissue charring with the AcQCross needle at 30 W compared to punctures with VersaCross wire. Tissue coring with the open-ended AcQCross needle was observed in vivo and measured to occur in 57% of punctures using the ex vivo model; no coring was observed with the closed-tip VersaCross wire. The AcQCross needle frequently required higher energy of 30 W to achieve RF TSP and was associated with tissue coring and charring, which have been, previously, reported when electrifying a standard open-ended mechanical needle or guidewire. These findings may limit safety and effectiveness compared to the VersaCross system.

Impact of Micropulse and Radio Frequency Coupling in an Atmospheric Pressure Plasma Jet on the Synthesis of Gold Nanoparticles

Gold nanoparticles have been extensively studied due to their unique optical and electronic properties which make them attractive for a wide range of applications in biomedicine, electronics, and catalysis. Over the past decade, atmospheric pressure plasma jets in contact with a liquid have emerged as a sustainable and environmentally friendly approach for synthesizing stable and precisely controlled dispersions. Within the context of plasma jet/liquid configurations, researchers have explored various power sources, ranging from kHz frequencies to nanopulse regimes. In this study, we investigated the effects of coupling two distinct power supplies: a high-voltage micropulse and a radio frequency (RF) generator. The variations within the plasma induced by this coupling were explored by optical and electrical measurements. Our findings indicated a transition from a bullet plasma propagation mechanism to a capacitive coupling mechanism upon the introduction of RF energy. The impact on the production of metal nanoparticles was also examined as a function of the radio frequency power and of two distinct process gases, namely helium and argon. The characterization of gold nanoparticles included UV-visible spectroscopy, dynamic light scattering, and scanning electron microscopy. The results showed that the size distribution depended on the type of process gas used and on the power supplies coupling. In particular, the incorporation of RF power alongside the micropulse led to a decrease in both average particle size and distribution width. The comparison of the different set up suggested that the current density can influence the particle size distribution, highlighting the potential advantages of the use of a dual-frequency atmospheric pressure plasma jet configuration.

A wireless, solar-powered, optoelectronic system for spatial restriction-free long-term optogenetic neuromodulations.

Numerous wireless optogenetic systems have been reported for practical tether-free optogenetics in freely moving animals. However, most devices rely on battery-powered or coil-powered systems requiring periodic battery replacement or bulky, high-cost charging equipment with delicate antenna design. This leads to spatiotemporal constraints, such as limited experimental duration due to battery life or animals' restricted movement within specific areas to maintain wireless power transmission. In this study, we present a wireless, solar-powered, flexible optoelectronic device for neuromodulation of the complete freely behaving subject. This device provides chronic operation without battery replacement or other external settings including impedance matching technique and radio frequency generators. Our device uses high-efficiency, thin InGaP/GaAs tandem flexible photovoltaics to harvest energy from various light sources, which powers Bluetooth system to facilitate long-term, on-demand use. Observation of sustained locomotion behaviors for a month in mice via secondary motor cortex area stimulation demonstrates the notable capabilities of our device, highlighting its potential for space-free neuromodulating applications.

Compact multi-channel radio frequency pulse-sequence generator with fast-switching capability for cold-atom interferometers.

Cold-atom interferometers have matured into a powerful tool for fundamental physics research, and they are currently moving from realizations in the laboratory to applications in the field. A radio frequency (RF) generator is an indispensable component of these devices for controlling lasers and manipulating atoms. In this work, we developed a compact RF generator for fast switching and sweeping the frequencies and amplitudes of atomic-interference pulse sequences. In this generator, multi-channel RF signals are generated using a field-programmable gate array (FPGA) to control eight direct digital synthesizers (DDSs). We further propose and demonstrate a method for pre-loading the parameters of all the RF pulse sequences to the DDS registers before their execution, which eliminates the need for data transfer between the FPGA and DDSs to change RF signals. This sharply decreases the frequency-switching time when the pulse sequences are running. Performance characterization showed that the generated RF signals achieve a 100ns frequency-switching time and a 40 dB harmonic-rejection ratio. The generated RF pulse sequences were applied to a cold-atom-interferometer gyroscope, and the contrast of atomic interference fringes was found to reach 38%. This compact multi-channel generator with fast frequency/amplitude switching and/or sweeping capability will be beneficial for applications in field-portable atom interferometers.

Use of electrical measurements for non-invasive estimation of plasma electron density in the inductively coupled SPIDER ion source

SPIDER (source for the production of ions of deuterium extracted from RF plasma) is the full-scale prototype of the ITER neutral beam injector ion source. The plasma heating takes place inside eight drivers via inductive coupling, through the radiofrequency (RF) coil. To achieve optimum conditions during source operation it is necessary to know the plasma behavior under various operational conditions. One of the essential parameters is the plasma electron density. It is possible to experimentally measure this parameter and, currently, different methods are being explored, such as the estimations coming from a Langmuir probe and optical emission spectroscopy. However, these methods are either available for temporary measurements or require dedicated analyses with large uncertainties. In this regard, alternative, reliable, and fast diagnostic tools will be beneficial for the estimation of the order of magnitude of electron density inside the driver. Two models for the estimation of electron density are recalled, discussed, and further modified in this work: one is based on the classical power balance equation, and the other is recently described in the literature and relies on classical plasma conductivity. Both models use equivalent electrical parameters of the driver derived from available electrical measurements at the output of the RF generator and through the knowledge of the matching network and the transmission line length. This work explicitly focuses on the application of these models to estimate the plasma electron density in a single driver of SPIDER. Furthermore, the estimations are compared with the first experimental results obtained from temporary electrostatic probe measurements and are found to be in good agreement in terms of magnitude and trends.

Modeling and Operation of Series-Parallel Resonant Load in Industrial RF Dielectric Heating Application

Radio Frequency (RF) based heating application is used in multiple industries like drying cross-laminated woods, food and packaging, melting silicon etc. These industrial RF heating plants operate at frequencies of 6.78 MHz, 13.56 MHz, or 27.12 MHz (ISM band). Historically, the high frequency requirement has forced the industry to rely on vacuum tube based RF generator, which are only 60% efficient. Modern semiconductors like wide bandgap (WBG) devices have achieved the high frequency operation that is required to replace the inefficient vacuum tubes. However, a comprehensive study of load network for an industrial RF heating plant has not been undertaken such that an existing plant can be retrofitted with semiconductor based turn-key solution. In this paper the authors present design equations for an industrial RF dielectric heating load structure and suggest necessary modifications required to replace vacuum tube RF generator with voltage source converter (VSC). A new figure of merit (FOM) is defined that impacts the load structure efficiency. Finally, a small-scale prototype load is manufactured as a case study. The prototype demonstrated an output power of 750 W at 6.76 MHz with an overall efficiency of 90% from DC input to RF load which can not be achieved with a vacuum tube technology.