Evaluation of the nonlinear surface resistance of REBCO coated conductors for their use in the FCC-hh beam screen

To assess the feasibility of using high-temperature superconductors for the beam screens of future circular colliders, we have undertaken a study of the power dependence of the microwave surface resistance in state-of-the-art REBCO coated conductors at about 8GHz and 50K. We have employed a dielectric resonator to produce radio-frequency electromagnetic fields on the surface of the coated conductors having amplitudes similar to those generated by proton bunches circulating in the vacuum chamber of the proposed hadron-hadron Future Circular Collider at CERN. We show that surface resistances in REBCO coated conductors without artificial pinning centers are more affected by a radio-frequency magnetic field than those containing nano-inclusions. Despite that, at 8GHz, 50K, and 9T, most REBCO coated conductors studied outperform copper in terms of surface resistance, with the best sample having a 2.3mΩ surface resistance while being subject to an RF field 2.5 times stronger than that in the FCC-hh. We also extrapolate the measured data to 16T and 1GHz, the actual FCC-hh dipole magnetic field, and mid beam frequency spectrum, demonstrating the possibility of lowering the surface resistance of the vacuum chamber by up to two orders of magnitude compared to copper. Further, we discuss the correlation between the time structure of the electromagnetic fields provided by vector network analyzers compared to the proton bunches' time structure in the collider and present the effect of low alternating magnetic fields on vortex displacement and the possibility of demagnetization of superconducting samples.

Coercivity Dependence of Microwave Characteristics in Mechanically Alloyed SrFe11.9-yMny/2Tiy/2In0.1O19 (y = 0; 0,3; and 1.2)

Recent investigation on indium substituted SrFe11.9In0.1O19 has shown excellent remanence to the saturation magnetization ratio of much greater than the 0.5 that most suitable for isotropic permanent magnets. In this work, such material SrFe12-xInxO19 (x = 0; 0,05; 0,1; 0,2; and 0,5) with the highest value of remanent magnetization was modified by the co-substitution of Fe+3 in SrFe11.9In0.1O19 with Mn and Ti ions to reduce the coercivity which suitable for radar absorbing applications. A series of magnetic material with SrFe11.9-yMny/2Tiy/2In0,1O19 (y = 0,3; 0,6; 1,0 and 1,2) compositions were prepared by mechanical alloying process. The hysteresis loop for SrFe11.9-yMny/2Tiy/2In0,1O19 samples showed that the coercivity was progressively reduced from 300 kA/m for y = 0,6 to 100 kA/m for y = 1.2 with the remanence remained significantly un-changed. The reflection loss (RL) which calculated from S-parameters of vector network analyzers (VNA) has resulted in excellent absorption characteristics of SrFe11.9-yMny/2Tiy/2In0,1O19 driven by high remanent magnetization and reduced coercivity.

Reference Breast Phantoms for Low-Cost Microwave Imaging

Microwave imaging provides an alternative method for breast cancer screening and the diagnosis of cerebrovascular accidents. Before a surgical operation, the performance of microwave imaging systems should be evaluated on anatomically detailed anthropomorphic phantoms. This paper puts forward the advances in the development of breast phantoms based on 3D printing structures filled with liquid solutions that mimic biological tissues in terms of complex permittivity in a wide microwave frequency band. In this paper; four different experimental scenarios were created, and measurements were performed, and although there are many vector network analyzers on the market, the miniVNA used in this study has been shown to have potential in many biomedical applications such as portable computer-based breast cancer detection studies. We especially investigated the reproducibility of a particular mixture and the ability of some mixes to mimic various breast tissues. Afterwards, the images similar to the experimentally created scenarios were obtained by implementing the inverse radon transform to the obtained data.

A Low-Cost Electronic System for Human-Body Communication

Human-body communication (HBC) has increasingly gained attention from academia and industry. Most current works focus on characterizing the use of human-body tissues as a physical medium to enable reliable communication. However, designing coupling hardware and communication circuits for reliable data transmission (e.g., high throughput and low latency) is a demanding task, especially for achieving a compact full electronic implementation. For this purpose, there are few commercial devices, mainly differential probes and balun transformers, employed with electrical analysis instruments such as oscilloscopes and vector network analyzers. Although these devices are widely used, they are expensive and are difficult to miniaturize and integrate into real-world HBC-specific applications (e.g., data security). This article presents a low-cost electronic system that transfers collected data using a secondary channel: the ionic environment (the primary channel would be the wireless environment). We design an electronic system as an experimental setup for studying HBC, allowing the communication between instruments, sensors, and actuators by human-body tissues. The experimental evaluation of the proposed system follows (i) a phantom composed of saline (0.9%) and (ii) a real human forearm through adhesive surface electrodes.

Analysis of Time and Frequency Response for Single/Multi-Tone Stimulus Harmonic Phase-Reference Based on Prime Number Algorithm

We present a spectrally-dense phase-reference and its calibration for nonlinear vector network analyzers (NVNAs) using a step recovery diode (SRD) comb-generator with a multi-tone stimulus. Frequency selection for multi-tone stimulus based on prime number algorithms was used with the Digital Real-Time Oscilloscope (DRTO) to avoid the sub-Nyquist spurs components and to increase the effective sampling rate so that the waveform can be observed in greater detail. The measured results were calibrated to minimize drift and jitter and achieved excellent agreement between the prime number and the exact frequency strategies except at the sub-Nyquist frequencies. The analysis indicates that the prime number selected frequencies show significantly improved performance by avoiding the DRTO distortion components. We have verified the validity of the method described in this paper by experimental measurement results.

How (and why) to determine NMR spectrometer’s noise figure?

In the last decade or two, it seems that the trend of technological advance in NMR spectroscopy cannot follow the trend of desire to measure NMR samples with gradually lower response signals. Recently, an accurate noise model, based on the concept of noise figure, of the most sensitive part of the NMR spectroscopy system from the aspect of noise, which is its probe-to-spectrometer receiving chain, was introduced. The main purpose of this model is to optimize the used NMR spectroscopy system and, ultimately, enable measuring NMR samples with even lower response signals than the ones measured today. All the parameters of the NMR spectroscopy system, used in the introduced model, can be easily measured using vector network analyzers and noise figure meters, or can be found in the datasheets of the respective elements, except the spectrometer’s receiving chain noise figure. In this contribution, the process of spectrometer’s receiving chain noise figure measurement, performed using the Twice Power Method, is described. A block diagram representation of the spectrometer’s receiving chain is presented here, as well as its approximative model. The respective noise figure measurement results, which are also presented, explain the general tendency of using the mid-range of the spectrometer’s gain control level when performing the actual NMR measurements.

A Method for Measuring LC Resonance Frequency by Impulse Response

LC circuit resonance frequency measurement often requires the use of professional analysis instruments such as LCR meters, vector network analyzers, but currently such instruments on the market are expensive, and it is difficult for non-professional institute personnel to access. Here comes unnecessary trouble. In view of this situation, a test method for measuring the resonance frequency using only a digital storage oscilloscope is proposed. Using the impulse signal to obtain the system response, the response waveform period can be observed through the oscilloscope.