Comparison of Measured Soft X-Ray Yield Versus Pressure for NX1 and NX2 Plasma Focus Devices Against Computed Values Using Lee Model Code

The soft X-ray yield versus pressure curves of NX1 and NX2 plasma focus machines have been measured and published for different pressures and electrode configurations. In this work, the numerical experiments are carried out, using Lee model code. The Lee model code is configured for each of these devices NX1 and NX2 by fitting computed total discharge current waveform against a measured total discharge current waveform. The computed soft X-ray yield versus pressure curves are compared with the laboratory measured soft X-ray yield versus pressure data. The comparison shows agreement between computation and measurement of several important features of the yield versus pressure curves.     

Some Generalised Characteristics of the Electro-dynamics of the Plasma Focus in Its Axial Phase: Illustrated by an Application to Independantly Determine the Drive Current Fraction and the Mass Swept-Up Fraction

We describe the axial phase of the Mather plasma focus by two coupled equations of motion and circuit. We non-dimensionalised these equations resulting in two coupled equations which are characterised by only three scaling parameters α, β and δ which are ratios of electrical to transit times, inductances and impedances respectively. The normalised current waveform, trajectory and speed profile are unique for each combination of α, β, δ which are the ratios of characteristic times (electrical discharge vs. axial transit), inductances (tube inductance vs. static inductance) and impedances (stray resistance vs. electrical surge impedance). This leads to important information and insight into various aspects of the axial phase. In the present work we show that in a time-matched plasma focus shot we deduce the value of axial phase current fraction f_c simply by measuring the calibrated voltage waveform and the uncalibrated current waveform. The scaling parameters β and δ are fixed; and by form-fitting the measured current waveform to the normalised current waveform using the value of α of the shot is determined uniquely; from which the peak current and the ratio of peak to average speed [the speed form factor (SFF)] are obtained. The average transit speed is measured by time-of-flight using the voltage upturn as indicator of end of axial phase. Then the SFF yields the peak speed. The measured voltage (back EMF), peak current and peak axial speed (all at the end of axial phase) allows the unambiguous measurement of f_c. The value of the mass swept-up fraction f_m is deduced from α which is the ratio of the characteristic discharge and the characteristic transit times, both deduced during the non-dimensionalisation of the equations. Analysis of a time-matched shot in the INTI PF at 15 kV, 3 Torr D₂ gave f_c = 0.68 and f_m = 0.05.     

Effects of Power Terms and Thermodynamics on the Contraction of Pinch Radius in Plasma Focus Devices Using the Lee Model

The influence of the power terms Joule heating and radiative losses on the pinch radius in plasma focus devices is studied. Numerical experiments were carried out using the Lee model on three plasma focus devices spanning a large range of storage energy (PF400, INTI PF, PF1000) with different filling gases (N, O, Ne, Ar, Kr, Xe). Six possible regimes each characterized by a combination of significant power terms affecting plasma focus dynamics are found and discussed. These six possible regimes are further moderated by thermodynamic effects related to the specific heat ratio SHR of the plasma. In PF1000, the thermodynamic compression effects are clearly apparent in the radius ratio versus pressure curve for nitrogen which with atomic number Z_n = 7 is less radiative than neon with Z_n = 10, the dominant line radiation being proportional to Z _n ⁴ . In neon radiative compression at optimum pressure is so dominant that it masks thermodynamic compression in the compression versus pressure graph. Results show that plasma radiation losses enhance the contraction of the plasma focus pinch radius within suitable pressure ranges characteristic of each machine for each gas discussed in this paper. The radiation enhancement of compression increases with the atomic number of the gas.     

Practical Optimization of AECS PF-2 Plasma Focus Device for Argon Soft X-ray Operation

For operation of the plasma focus in argon, a focus pinch compression temperature range of 1.4–5 keV (16.3 × 10⁶–58.14 × 10⁶ K) is found to be suitable for good yield of argon soft X-rays (SXR) Ysxr. This is based on reported temperature measurements of argon plasmas working at regime for X-ray output. Using this temperature window, numerical experiments have been investigated on AECS PF-2 plasma focus device with argon filling gas. The model was applied to characterize the 2.8 kJ plasma focus AECS PF-2. The optimum Ysxr was found to be 0.0035 J. Thus, we expect to increase the argon Ysxr of AECS PF-2, without changing the capacitor bank, merely by changing the electrode configuration and operating pressure. The Lee model code was also used to run numerical experiments on AECS PF-2 with argon gas for optimizing soft X-ray yield with reducing L₀, varying z₀ and ‘a’. From these numerical experiments we expect to increase the argon Ysxr of AECS PF-2 with reducing L₀, from the present computed 0.0035 J at L₀ = 270 nH to maximum value of near 0.082 J, with the corresponding efficiency is about 0.03%, at an achievable L₀ = 10 nH.     

Dependence of Plasma Focus Argon Soft X-Ray Yield on Storage Energy, Total and Pinch Currents

Numerical experiments are carried out systematically to determine the argon soft X-Ray yield Y_sxr for optimized argon plasma focus with storage energy E₀ from 1 kJ to 1 MJ. The ratio c = b/a, of outer to inner radii; and the operating voltage V₀ are kept constant. E₀ is varied by changing the capacitance C₀. These numerical experiments were investigated on argon plasma focus at different operational gas pressures (0.41, 0.75, 1, 1.5, 2.5 and 3 Torr) for two different values of static inductance L₀ (270 and 10 nH). Scaling laws on argon soft X-Ray yield, in terms of storage energies E₀, peak discharge current I_peak and focus pinch current I_pinch were found. It was found that the argon X-ray yields scale well with \textY_\textsxr = 8 ×10 ^{- 11} \textI_\textpinch^4.12 {\text{Y}}_{\text{sxr}} = 8 \times 10^{ - 11} {\text{I}}_{\text{pinch}}^{4.12} for the high inductance (270 nH) and \textY_\textsxr = 7 ×10 ^{- 13} \textI_\textpinch^4.94 {\text{Y}}_{\text{sxr}} = 7 \times 10^{ - 13} {\text{I}}_{\text{pinch}}^{4.94} for the low inductance (10 nH), (where yields are in joules and current in kilo amperes). While the soft X-ray yield scaling laws in terms of storage energies were found to be as \textY_\textsxr = 0.05 ×\textE₀^0.94 {\text{Y}}_{\text{sxr}} = 0.05 \times {\text{E}}_{0}^{0.94} at energies in the 1–100 kJ region. The scaling ‘drops’ as E₀ is increased, and Y_sxr scales as \textY_\textsxr = 1.01 ×\textE₀^0.33 {\text{Y}}_{\text{sxr}} = 1.01 \times {\text{E}}_{0}^{0.33} at high energies towards 1 MJ for 10 nH at argon gas pressure of 1 Torr. The optimum efficiencies for SXR yield were found to be 0.00077% with a capacitor bank energy of 112.5 kJ for high inductance (270 nH) and 0.005% with a capacitor bank energy of 4.5 kJ for low inductance (10 nH). Therefore for larger devices, it may be necessary to operate at a higher voltage and use higher driver impedance to ensure increasing X-ray yield efficiency beyond the optimum values. As storage energy is changed the required electrode geometry for optimum yield is obtained and the resultant plasma pinch parameters are found. Required values of axial speed for argon soft X-ray emission were found to be in the range 11–14 cm/μs.     

Modeling of two core photonic crystal fiber modal interferometer for refractive index measurement by equalization wavelength

We propose a modification structure model of in-fiber sensor based on intermodal interference in two core photonic crystal fiber for external refractive index measuring. Essential characteristics and influences of the structure are investigated. Formation of an extreme (equalization wavelength) in phase constant spectral dependence is presented and its using for simple external refractive index determination.     

An adaptive fuzzy handover triggering approach for Long‐Term Evolution network

To cope with the increasing demand for efficient data delivery, self‐organizing networks have been introduced in the Long Term Evolution (LTE) system to provide autonomous and flexible mobility management. The existing handover triggering scheme for LTE is not flexible enough to incorporate new performance metrics, and it introduces handover latency. There are studies on non‐conventional handoff algorithms for LTE applications, for instance, the fuzzy logic approach. However, the fuzzy logic approach needs regular manual tuning to constantly produce optimal output. In this paper, we address this issue by proposing an adaptive fuzzy logic‐based handoff decision algorithm, which can cope with environmental changes and improve efficiency by reducing human intervention. Performance results show that the proposed algorithm can reduce unnecessary handovers by about 20% compared with the fuzzy logic and conventional LTE handover triggering scheme, leading to reduced packet loss rates.     

A post-processing method for true random number generators based on hyperchaos with applications in audio-based generators

True random number generators (TRNG) are important counterparts to pseudorandom number generators (PRNG), especially for high security applications such as cryptography. They produce unpredictable, non-repeatable random sequences. However, most TRNGs require specialized hardware to extract entropy from physical phenomena and tend to be slower than PRNGs. These generators usually require post-processing algorithms to eliminate biases but in turn, reduces performance. In this paper, a new post-processing method based on hyperchaos is proposed for software-based TRNGs which not only eliminates statistical biases but also provides amplification in order to improve the performance of TRNGs. The proposed method utilizes the inherent characteristics of chaos such as hypersensitivity to input changes, diffusion, and confusion capabilities to achieve these goals. Quantized bits of a physical entropy source are used to perturb the parameters of a hyperchaotic map, which is then iterated to produce a set of random output bits. To depict the feasibility of the proposed post-processing algorithm, it is applied in designing TRNGs based on digital audio. The generators are analyzed to identify statistical defects in addition to forward and backward security. Results indicate that the proposed generators are able to produce secure true random sequences at a high throughput,which in turn reflects on the effectiveness of the proposed post-processing method.     

Comparison of the performance of copper oxide and yttrium oxide nanoparticle based hydroxylethyl cellulose electrolytes for supercapacitors

Biodegradable solid polymer electrolyte (SPE) systems composed of hydroxylethyl cellulose blended with copper(II) oxide (CuO) and yttrium(III) oxide (Y₂O₃) nanoparticles as fillers, magnesium trifluoromethane sulfonate salt, and 1‐ethyl‐3‐methylimidazolium trifluoromethane sulfonate ionic liquid were prepared, and the effects of the incorporation of CuO and Y₂O₃ nanoparticles on the performance of the SPEs for electric double‐layer capacitors (EDLCs) were compared. The X‐ray diffraction results reveal that the crystallinity of the SPE complex decreased upon inclusion of the Y₂O₃ nanoparticles compared to CuO nanoparticles; this led to a higher ionic conductivity of the Y₂O₃‐based SPE [(3.08 ± 0.01) × 10^?4 S/cm] as compared to CuO [(2.03 ± 0.01) × 10^?4 S/cm]. The EDLC performances demonstrated that the cell based on CuO nanoparticles had superior performance in terms of the specific capacitance, energy, and power density compared to the Y₂O₃‐nanoparticle‐based cell. However, Y₂O₃‐nanoparticle‐based cell displayed a high cyclic retention (91.32%) compared to the CuO‐nanoparticle‐based cell (80.46%) after 3000 charge–discharge cycles. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44636.     

Particle/cell separation on microfluidic platforms based on centrifugation effect: a review

Particle/cell separation in heterogeneous mixtures including biological samples is a standard sample preparation step for various biomedical assays. A wide range of microfluidic-based methods have been proposed for particle/cell sorting and isolation. Two promising microfluidic platforms for this task are microfluidic chips and centrifugal microfluidic disks. In this review, we focus on particle/cell isolation methods that are based on liquid centrifugation phenomena. Under this category, we reviewed particle/cell sorting methods which have been performed on centrifugal microfluidic platforms, and inertial microfluidic platforms that contain spiral channels and multi-orifice channels. All of these platforms implement a form of centrifuge-based particle/cell separation: either physical platform centrifugation in the case of centrifugal microfluidic platforms or liquid centrifugation due to Dean drag force in the case of inertial microfluidics. Centrifugal microfluidic platforms are suitable for cases where the preparation step of a raw sample is required to be integrated on the same platform. However, the limited available space on the platform is the main disadvantage, especially when high sample volume is required. On the other hand, inertial microfluidics (spiral and multi-orifice) showed various advantages such as simple design and fabrication, the ability to process large sample volume, high throughput, high recovery rate, and the ability for multiplexing for improved performance. However, the utilization of syringe pump can reduce the portability options of the platform. In conclusion, the requirement of each application should be carefully considered prior to platform selection.