Source Configuration Research Articles

Alternating Current-Based Technique for Separate Extraction of Parasitic Resistances in MISFETs With or Without the Body Contact

We report a novel technique for separating the parasitic source (RS) and drain (RD) resistances in MISFETs using the open drain and the open source configurations based on an alternating-current(AC) signal. We conducted impedance analysis for the AC signal in the open drain for RS and the open source configuration for RD. The proposed technique is independent of the I-V equation of MISFETs with various influencing parameters for separate extraction of RS and RD through the physics-based equivalent circuit of MISFETs. So the proposed technique is applicable to every single device as long as the device is an insulated gate MISFET structure, regardless of the presence or absence of the body terminal. This technique is applied to amorphous oxide semiconductor thin-film transistors with the gate length =10μm without the body contact. As a result, parasitic resistances were separately extracted to be R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</sub> = 2.1 kΩ, R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</sub> = 1.7 kΩ for W = 600μm, R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</sub> = R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</sub> =1.1 kΩ for W = 1000μm, and R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</sub> = R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</sub> = 0.6 kΩ for W = 2000μm independent of gate bias.

An efficient solver for the generalized normal modes of non-uniform open optical resonators

Modal expansion is an attractive technique for solving electromagnetic scattering problems. With the one set of resonator modes, calculated once and for all, any configuration of near-field or far-field sources can be obtained almost instantaneously. Traditionally applied to closed systems, a simple and rigorous generalization of modal expansion to open systems using eigenpermittivity states is also available. These open modes are suitable for typical nanophotonic systems, for example. However, the numerical generation of modes is usually the most difficult and time-consuming step of modal expansion techniques. Here, we demonstrate efficient and reliable mode generation, expanding the target modes into the modes of a simpler open system that are known. Such a re-expansion technique is implemented for resonators with non-uniform permittivity profiles, demonstrating its rapid convergence. Key to the method's success is the inclusion of a set of longitudinal basis modes.

Development of an algorithm for gamma dose mapping in irradiated product using TOPSIS and its validation

Achieving technological perseverance and retention of quality of the products are being carried out through gamma irradiation. The conventional methodology for dose mapping in products is a complex and time-consuming process. In general, the operator spends lots of time to gain experience and fix the optimal irradiation parameters. Considering the complex geometrical configuration of product box and source, an efficient and simple methodology is needed for estimating dose profile. The estimation of various process parameters for product irradiation such as dose uniformity ratio, minimum and maximum dose is pre-requisite for routine operation. The irradiation process starts with the transport of identical product boxes to the irradiation cell through a guided path. The carriers are irradiated at known positions in the cell for the ideal process conditions defined by various parameters such as the bulk density of product, distance from the source, conveyer speed, duration of irradiation, irradiation temperature, etc. This research proposes a multi-criteria decision-making methodology to select the best strategy for dose mapping. Analytical Hierarchy Process (AHP) and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) have been used to optimize the process variables. To validate the robustness of the proposed methodology, the experimental data set has been generated during the commissioning of the desired configuration of source and product using a leave-one-out strategy. The proposed methodology has been applied for dosimetry of homogeneous product containing sawdust and rice husk. The dose uniformity ratio using the proposed methodology is found to be better than the conventional commissioning dosimeter. The statistical parameters can be evaluated with the Y-set in contrary to that of obtained from the Z set of conventional methods. The methodology is generic and can help the operator with/without experience, while mapping dose in products. • An algorithm based on AHP & TOPSIS is used for the map of gamma dose in gamma irradiator. • The algorithm is validated during commissioning dosimetry of gamma irradiator. • The proposed algorithm is faster than convention dosimetry procedure. • Z-set of dose mapping may be avoided using the proposed algorithm. • Operating parameters and throughput of gamma irradiator can better optimize.

Obliquity dependence of the formation of the martian polar layered deposits

Mars' polar layered deposits (PLD) are comprised of layers of varying dust-to-water ice volume mixing ratios (VMR) that may record astronomically-forced climatic variation over Mars' recent orbital history. Retracing the formation of these layers by quantifying the sensitivity of deposition rates of polar material to astronomical forcing is critical for the interpretation of this record. Using a Mars global climate model (GCM), we investigate the sensitivity of annual polar water ice and dust surface deposition to various obliquities and surface water ice distributions at zero eccentricity, providing a reasonable characterization of the evolution of the PLD during recent low-eccentricity epochs. For obliquities between 15{\deg} - 35{\deg}, predicted net annual accumulation rates range from -1 to +14 mm/yr for water ice and from +0.003 to +0.3 mm/yr for dust. GCM-derived rates are ingested into an integration model that simulates polar accumulation of water ice and dust over 5 consecutive obliquity cycles (~700 kyrs) during a low eccentricity epoch. A subset of integration simulations predict combined accumulation of water ice and dust in the north at time averaged rates that are near the observationally-inferred value of 0.5 mm/yr. Three types of layers are produced per obliquity cycle: a ~30 m-thick dust-rich (~25% dust VMR) layer forms at high obliquity, a ~0.5 m-thick dust lag forms at low obliquity, and two ~10 m-thick dust-poor (~3%) layers form when obliquity is increasing/decreasing. The ~30 m-thick dust-rich layer is reminiscent of a ~30 m feature derived from visible imagery analysis the north PLD, while the ~0.5 m-thick dust lag is a factor of ~2 smaller than observed "thin layers". Overall, this investigation provides further evidence for obliquity forcing in the PLD climate record, and demonstrates the importance of ice-on-dust nucleation in polar depositional processes.

Modelling of magnetic bead transport in a microvascular network

Abstract In in vivo applications of magnetic particles one crucial aspect is the control of their transport in the tissue microvasculature and their release to target areas. These mechanisms can be driven and influenced by external magnetic fields with large gradients. Experimental results can be elucidated with the aid of in silico models that can also be employed to design optimized multifunctional particles and magnetic field sources. In this framework, we have developed a numerical model that enables us to calculate the trajectory of an ensemble of magnetic nano/microbeads injected in a blood vessel and manipulated by an applied magnetic field. The model combines Navier-Stokes equations for the fluid dynamics simulation of blood flow with classical Newtonian mechanics for bead motion, performing the analysis in a 3D vessel segment reconstructed from a computed tomography scan. The numerical model is applied to study the influence of bead properties (size and magnetic moment) on both transport and adhesion rate, taking into account the interplay of magnetic and viscous drag forces, as well as magnetic dipole–dipole and steric interactions. We also consider different configurations of the external magnetic field source, in order to optimize bead accumulation and adhesion to the vessel wall in a specific target region, processes that can be driven by magnetic forces.

Mapping Fuzzy Energy Management Strategy for PEM Fuel Cell–Battery–Supercapacitor Hybrid Excavator

By replacing conventional supplies such as fossil fuels or internal combustion engines (ICEs), this paper presents a new configuration of hybrid power sources (HPS) based on the integration of a proton-exchange membrane fuel cell (PEMFC) with batteries (BATs) and supercapacitors (SCs) for hydraulic excavators (HEs). In contrast to conventional architectures, the PEMFC in this study functions as the main power supply, whereas the integrated BAT–SC is considered as an auxiliary buffer. Regarding shortcomings existing in the previous approaches, an innovative energy management strategy (EMS) was designed using a new mapping fuzzy logic control (MFLC) for appropriate power distribution. Comparisons between the proposed strategy with available approaches are conducted to satisfy several driving cycles with different load demands and verify the strategy’s effectiveness. Based on the simulation results, the efficiency of the PEMFC when using the MFLS algorithm increased up to 47% in comparison with the conventional proposed EMS and other approaches. With the proposed strategy, the HPS can be guaranteed to not only sufficiently support power to the system even when the endurance process or high peak power is required, but also extend the lifespan of the devices and achieves high efficiency.

Inadequacy of plume rise information to predict the ground level pollutant concentration in vicinity of small cooling towers

Dispersion of pollutant emitted from cooling towers is investigated to discover the pollution concentration distribution at the ground level. The objective is to find the proper arrangement of the cooling towers leading to a lesser concentration of pollutant on the ground. This can be very useful for sustainable development of areas in vicinity of the towers. Comprehensive plume rise data available in the literature has greatly helped to understand how an exhaust plume disperses in a cross wind. In this article, it is shown that the concentration of pollutant on the ground deduced from the plume rise behavior differs from what obtained via direct calculation. The maximum concentration of pollutant on the ground is found to occur once towers are placed in tandem. That is in contrast with what is inferred from the behavior of plume rise. For side by side towers, the plume rise occurs at a lower altitude which can mislead one to conclude that more pollutant would reach the ground surface. The evolution of vortices is employed to explain such discrepancy between the results of direct calculation and those deduced from the plume rise behavior. Similar discussions are presented for square and diamond configurations of multi-flue sources.

Induced polarization effect on grounded-wire transient electromagnetic data from transverse electric and magnetic fields

Transient electromagnetic (TEM) data can be seriously distorted by induced polarization (IP) phenomena when a polarizable body is present. The TEM field generated by a grounded-wire source contains transverse electric (TE) and transverse magnetic (TM) modes. The IP effect is most commonly studied with the TEM total field, rather than considering the difference between TE and TM fields. To investigate the effect of IP phenomena on the TE and TM fields, we have performed a detailed analysis on IP-distorted TEM data based on numerical and field examples. We first compare the IP effect on the TE and TM fields when polarizable bodies with different polarizable parameters are present. The TM field is more severely affected by the IP effect than the TE field. Compared to a single grounded-wire source, a double-line grounded-wire source can generate a larger TM field in the horizontal electric field. We compare the IP effect on TEM data from single- and double-line grounded-wire TEM configurations, and find that the data from the double-line configuration have a higher TM/TE ratio and are more severely affected by IP phenomena than in the single-line case. Thus, it would be easier to identify and extract the IP response from field data acquired with a double-line grounded-wire source configuration. These results have been verified by a field survey of the Kalatongke copper-nickel ore district, which has predominantly layered geology, in Xinjiang, China.

Impact of temperature on RF characteristics and electrical noise analysis of an L‐shaped gate tunnel FET with hetero‐stacked source configuration

In this article, a pocket doped hetero-stacked L-shaped gate silicon-on-insulator (SOI) tunnel FET (HS-LG-TFET) has been proposed and investigated. The band-to-band tunneling (BTBT) feature of LG-TFET in a direction perpendicular to the channel facilitates higher ON current due to relatively larger tunneling area. The channel appears to be U-shaped that is primarily distributed along the vertical direction, which increases the device scalability. Besides, the HS source architecture owns an upper source layer, which consists of larger bandgap material silicon and an underlying source layer, which consists of smaller bandgap material germanium. This underlying layer of smaller bandgap material in HS-LG-TFET provides enhanced ON current as well as steeper subthreshold swing behavior. The electrical noise behavior of the proposed structure is addressed to test its viability. Furthermore, a complete radio frequency (RF) characterization, including transconductance, capacitances, cutoff frequency, gain bandwidth product, maximum oscillation frequency, transit time, and minimum noise figure of the proposed device are analyzed to examine its analog applicability. Moreover, for checking the reliability issues associated with temperature, the temperature dependence on transfer and RF characteristics are also explored and presented. Further, the non-quasi-static equivalent circuit of the proposed structure is presented to analyze its behavior in the high frequency range.

Modeling of a Spherical Tokamak as an Extended Neutron Source Using ASTRA and MCNP

Fast neutrons can perform two functions that are critical to the nuclear power industry: breed fissile material from fertile material and burn minor actinides in spent fuel. The fusion reaction in a fusion reactor between deuterium and tritium nuclei yields an alpha particle and a neutron with 14.5-MeV energy. These neutrons can easily convert fertile material (such as 238U and 232Th) into fissile material (such as 239Pu and 233U) and destroy minor actinides (Pu, Np, Am, and Cm) present in the spent nuclear fuel and significantly reduce its radiotoxicity. However, each neutron generated implies one tritium consumed and tritium is generated by nuclear reactions between a neutron and lithium nuclei. Therefore, neutron economy becomes a crucial issue and an adequate neutronic modeling of the neutron source becomes critical. In this article, the Automatic System for TRansport Analysis (ASTRA) and Monte Carlo N-Particle (MCNP) codes are used in conjunction to characterize the neutron flux coming out of a low-aspect-ratio tokamak machine. ASTRA is first used to determine temperature and density profiles within the plasma volume and MCNP is used to evaluate the neutron flux. Since the simulation of an extended neutron source with complex geometry such as the confined plasma inside the tokamak is difficult, steps are taken to simplify the geometry by defining two simple sources, a cylindrical wall and a disk, which should have similar neutron emission distributions to the volumetric source. This reduction is done using a preprocessing Monte Carlo algorithm to establish probability density functions of neutron emission for the cylindrical wall as a function of the height and for the disk as a function of the radius, based on the emission characteristics of the extended source. The results that compare the neutron flux leaving a volume for four different configurations of neutron sources (isotropic source at the geometrical origin, ring source at the plasma geometrical center, cylindrical wall source, and distributed multipoint source) are presented. It is found that the processing of the two simple sources has a higher computational cost in terms of both processing time and random number consumption.

Evaluation of chemistry and key reactor parameters for industrial water treatment applications of the UV/O3 process

In this study, the main influence factors of combined UV/O3 process in practical industrial application were explored through laboratory trials and industrial pilot tests. Dimethyl phthalate (DMP) was analyzed as the research subject through different experiments in laboratory. The degradation effect of organic compounds by O3 and UV/O3 processes in different air distribution methods was compared independently, and the mechanism of free radical generation by the two processes was analyzed. This study found that the combined UV/O3 process for organic matter mineralization is clearly better than that of independent effect of O3 process as mixed gas-liquid distribution method was superior to the bubble aeration method. The experimental conditions included inlet O3 concentration between 70 and 75mg/L, reactor internal relative pressure at 0.3MPa, contact reaction time of 12min, DMP mineralization efficiency reaching 63.07%. The calculated dosing ratio of O3 in the dynamic experiment was around 0.74mg CODCr/mg O3. The results showed that the best effect in wastewater treatment was achieved when the conditions of ultraviolet lamp irradiation intensity and the O3 dosage reached 822.88W/m2 15mg/L and utilized in conjunction with biochemical reactions. The resulting CODCr concentration of effluent reached 39.8mg/L. Finally, it is determined that the main influence factors affecting the economically efficient operation of UV/O3 process were the efficient O3 distribution mode, control of the relative pressure within the reactor, proportion of ozone addition and light source configuration.

Comparing the broadband acoustic frequency response of single, clustered, and arrays of marine air guns

Field data acquired from a seismic vessel by a seabed hydrophone is used to analyze the broadband response (10 Hz to 62.5 kHz) for various source configurations: single air guns, clustered air guns, and a full array consisting of 30 air guns. The various parts of the acoustic signal are analyzed in detail, and it is found that a high-frequency signal arriving prior to the main peak of a single air-gun signal most likely is caused by small vapor cavities collapsing at or close to the surface of the gun. This is confirmed by high-speed photographs taken when a small air gun is fired in a water tank. When the full array is used, a second type of cavitation signal is observed: ghost cavitation caused by acoustic stimulation by the negative pressure that is backscattered from the free surface. As this ghost signal from 30 different guns arrives at a specific location in the water, cavities might be formed, and they create a high-frequency acoustic signal.

Multilevel inverter with improved basic unit structure for symmetric and asymmetric source configuration

An improved multilevel inverter (MLI) topology using a new basic unit structure with a reduced number of components is proposed in this study. Its single compact module is made up of two basic units connected to the left and right sides of a packed H‐bridge. The topology produces 9‐Level output when operated symmetrically and 17‐Level output when operated asymmetrically. Identical magnitude of DC sources is used for the symmetrical operation, while non‐identical magnitudes in a trinary sequence are used for the asymmetrical operation. The low‐frequency modulation scheme is applied for the switching control where the switching angles are pre‐calculated. The mathematical formulations for the switching are also considered to reduce the total harmonic distortion (THD) at the output. The proposed topology is also found to be superior in terms of the required number of switches per output level and total blocking voltage compared to conventional and recently reported MLIs. With these merits, real‐time installation of the proposed topology will potentially require lesser space and become cheaper. The feasibility of the proposed topology is validated for its 9‐Level and 17‐Level operations through experimental verification on output characteristics, THD, blocking voltage, power‐sharing and efficiency.

FCN-Based 3D Reconstruction with Multi-Source Photometric Stereo

As a classical method widely used in 3D reconstruction tasks, the multi-source Photometric Stereo can obtain more accurate 3D reconstruction results compared with the basic Photometric Stereo, but its complex calibration and solution process reduces the efficiency of this algorithm. In this paper, we propose a multi-source Photometric Stereo 3D reconstruction method based on the fully convolutional network (FCN). We first represent the 3D shape of the object as a depth value corresponding to each pixel as the optimized object. After training in an end-to-end manner, our network can efficiently obtain 3D information on the object surface. In addition, we added two regularization constraints to the general loss function, which can effectively help the network to optimize. Under the same light source configuration, our method can obtain a higher accuracy than the classic multi-source Photometric Stereo. At the same time, our new loss function can help the deep learning method to get a more realistic 3D reconstruction result. We have also used our own real dataset to experimentally verify our method. The experimental results show that our method has a good effect on solving the main problems faced by the classical method.

FEMfuns: A Volume Conduction Modeling Pipeline that Includes Resistive, Capacitive or Dispersive Tissue and Electrodes

Applications such as brain computer interfaces require recordings of relevant neuronal population activity with high precision, for example, with electrocorticography (ECoG) grids. In order to achieve this, both the placement of the electrode grid on the cortex and the electrode properties, such as the electrode size and material, need to be optimized. For this purpose, it is essential to have a reliable tool that is able to simulate the extracellular potential, i.e., to solve the so-called ECoG forward problem, and to incorporate the properties of the electrodes explicitly in the model. In this study, this need is addressed by introducing the first open-source pipeline, FEMfuns (finite element method for useful neuroscience simulations), that allows neuroscientists to solve the forward problem in a variety of different geometrical domains, including different types of source models and electrode properties, such as resistive and capacitive materials. FEMfuns is based on the finite element method (FEM) implemented in FEniCS and includes the geometry tessellation, several electrode-electrolyte implementations and adaptive refinement options. The Python code of the pipeline is available under the GNU General Public License version 3 at https://github.com/meronvermaas/FEMfuns. We tested our pipeline with several geometries and source configurations such as a dipolar source in a multi-layer sphere model and a five-compartment realistically-shaped head model. Furthermore, we describe the main scripts in the pipeline, illustrating its flexible and versatile use. Provided with a sufficiently fine tessellation, the numerical solution of the forward problem approximates the analytical solution. Furthermore, we show dispersive material and interface effects in line with previous literature. Our results indicate substantial capacitive and dispersive effects due to the electrode-electrolyte interface when using stimulating electrodes. The results demonstrate that the pipeline presented in this paper is an accurate and flexible tool to simulate signals generated on electrode grids by the spatiotemporal electrical activity patterns produced by sources and thereby allows the user to optimize grids for brain computer interfaces including exploration of alternative electrode materials/properties.

On Reconfiguring 5G Network Slices

The virtual resources of 5G networks are expected to scale and support migration to other locations within the substrate. In this context, a configuration for 5G network slices details the instantaneous mapping of the virtual resources across all slices on the substrate, and a feasible configuration satisfies the Service-Level Objectives (SLOs) without overloading the substrate. Reconfiguring a network from a given source configuration to the desired target configuration involves identifying an ordered sequence of feasible configurations from the source to the target. The proposed solutions for finding such a sequence are optimized for data centers and cannot be used as-is for reconfiguring 5G network slices. We present Matryoshka, our divide-and-conquer approach for finding a sequence of feasible configurations that can be used to reconfigure 5G network slices. Unlike previous approaches, Matryoshka also considers the bandwidth and latency constraints between the network functions of network slices. Evaluating Matryoshka required a dataset of pairs of source and target configurations. Because such a dataset is currently unavailable, we analyze proof of concept roll-outs, trends in standardization bodies, and research sources to compile an input dataset. On using Matryoshka on our dataset, we observe that it yields close-to-optimal reconfiguration sequences 10X faster than existing approaches.

A Surface-to-Borehole TEM System Based on Grounded-wire Sources: Synthetic Modeling and Data Inversion

The surface-to-borehole transient electromagnetic (TEM) method, which uses a rectangular loop as its source, has shown great potential in mineral exploration at greater depth. However, recent studies have demonstrated that a grounded-wire source can resolve the resistive targets and provide detection at greater depths than the loop source. Thus, we propose a surface-to-borehole TEM method using a grounded wire as a transmitter at short offsets. We conducted numerical experiments to explain the variation of different parameters and its comparable effects on the TEM transients. Similarly, a systematic comparison of the cross-sectional electric field distribution maps, borehole profiles of the time derivatives of the magnetic field, qualitatively reveal that the proposed method induces detectable responses for conductive and resistive targets at greater depths. In the present study, unlike the loop source configuration, the time derivative of an underground magnetic field in horizontal direction showed high sensitivity to resistive bodies. Furthermore, 1-D inversion was performed to provide quantitative interpretation of the borehole data. The 1-D inversion of the surface and borehole data was realized using an Occam-type inversion scheme. The results of both synthetic and field data indicate that inverting the surface or borehole data separately resulted in degraded resolution in both shallow and deep earth. Thus, we also compared the results from the inversions of surface and borehole data in order to explore the merits of joint inversion in resolving shallow and deep structures.

Iron Line Tomography of General Relativistic Hydrodynamic Accretion around Kerr Black Holes

Abstract We consider a temporal response of relativistically broadened line spectrum of iron from black hole accretion irradiated by an X-ray echo under strong gravity. The physical condition of accreting gas is numerically calculated in the context of general relativistic hydrodynamics under steady-state axisymmetry in Kerr geometry. With the onset of a point-like X-ray flare of a short finite duration just above the accretion surface, the gas is assumed to be ionized to produce a neutral iron fluorescent line. Using a fully relativistic ray-tracing approach, the response of line photons due to the X-ray illumination is traced as a function of time and energy for different source configurations around Schwarzschild and Kerr black holes. Our calculations show that the X-ray echo on the accretion surface clearly imprints a characteristic time-variability in the line spectral features depending on those parameters. Simulated line profiles, aimed for the future microcalorimeter missions of large collecting area such as Athena/X-IFU for typical radio-quiet Seyfert galaxies, are presented to demonstrate that state-of-the-art new observations could differentiate various source parameters by such an X-ray tomographic line reverberation.

An Eye Gaze Tracking Method of Virtual Reality Headset Using A Single Camera and Multi-light Source

For the problems the hardware configuration of multi-camera and multi-light source is complicated and the eye image of little auxiliary light source is too dark in the eye gaze tracking system, A new eye gaze tracking system based on two-dimensional mapping model is proposed, which achieved the transformation from two-dimensional coordinates to three-dimensional coordinates combined attitude angle of virtual reality headset. In this paper, the mapping relationship between visual features and eye gaze points is established by improving the method of pupil image recognition and eye gaze estimation based pupil-corneal, which the accuracy of eye gaze estimation is further improved. The experimental results show that the error of eye gaze tracking system is less than 1.1 °, which achieved the good effect of eye gaze tracking.

Coherence time characterization method for hard X-ray free-electron lasers.

Coherence time is one of the fundamental characteristics of light sources. Methods based on autocorrelation have been widely applied from optical domain to soft X-rays to characterize the radiation coherence time. However, for the hard X-ray regime, due to the lack of proper mirrors, it is extremely difficult to implement such autocorrelation scheme. In this paper, a novel approach for characterizing the coherence time of a hard X-ray free-electron laser (FEL) is proposed and validated numerically. A phase shifter is adopted to control the correlation between X-ray and microbunched electrons. The coherence time of the FEL pulse can be extracted from the cross-correlation. Semi-analytical analysis and three-dimensional time-dependent numerical simulations are presented to elaborate the details. A coherence time of 218.2 attoseconds for 6.92 keV X-ray FEL pulses is obtained in our simulation based on the configuration of Linac Coherent Light Source. This approach provides critical temporal coherence diagnostics for X-ray FELs, and is decoupled from machine parameters, applicable for any photon energy, radiation brightness, repetition rate and FEL pulse duration.