Complementary safety assessments of the French nuclear facilities

EDF has conducted, after the Fukushima event, complementary safety assessments of its nuclear facilities. The aim of this in-depth review was to assess the resilience of each plant to extreme external hazards, situations that could lead to severe accident conditions. These analyses demonstrate a good level of safety for all of EDFʼs nuclear facilities. Supplementary measures post-Fukushima have been put forward to the ASN with the aim of continuing to improve the level of safety at the plants.Once the ASN position is issued, EDF will develop an action plan over several years, covering both supplementary studies and modifications that have been identified.     

Configuration interactions constrained by energy density functionals

A new method for constructing a Hamiltonian for configuration interaction calculations with constraints to energies of spherical configurations obtained with energy-density-functional (EDF) methods is presented. This results in a unified model that reproduced the EDF binding-energy in the limit of single-Slater determinants, but can also be used for obtaining energy spectra and correlation energies with renormalized nucleon–nucleon interactions. The three-body and/or density-dependent terms that are necessary for good nuclear saturation properties are contained in the EDF. Applications to binding-energies and spectra of nuclei in the region above ²⁰⁸Pb are given.     

铒纤长度对EDFA增益斜率影响的实验研究和数值模拟

基于掺铒光纤放大器(EDFA)的增益斜率随着铒纤(EDF)长度变化的实验现象,对EDFA的增益斜率进行了分析,研究了不同EDF长度对EDFA的增益斜率的影响,从理论上对实验现象进行了解释。然后用OptiSystem模拟不同EDF长度下的EDFA增益谱,与实验室增益斜率数据相一致,得出了用EDF的长度来控制EDFA增益斜率的方法。     

Erbium doped fiber ring laser for optical wavelength conversion

We experimentally investigate the gain saturation effect of a piece of 8 m long Erbium doped fiber (EDF), we introduce a theoretical model for the EDF ring loop, and our simulation results show very good cross-gain modulation (XGM) and wavelength conversion. We also experimentally investigate the XGM in an EDF ring loop system. Based on the study of the XGM in the EDF ring loop system, a wavelength conversion is designed with the EDF ring loop system. The EDF ring loop systems as a wavelength conversion is experimentally demonstrated by converting a sinusoidal modulated optical signal at wavelength of 1551 nm to an optical signal at wavelength of 1553.3 nm.     

Electron boltzmann kinetic equation averaged over fast electron bouncing and pitch-angle scattering for fast modeling of electron cyclotron resonance discharge

The electron distribution function (EDF) in an electron cyclotron resonance (ECR) discharge is far from Maxwellian. The self-consistent simulation of ECR discharges requires a calculation of the EDF on every magnetic line for various ion density profiles. The straightforward self-consistent simulation of ECR discharges using the Monte Carlo technique for the EDF calculation is very computer time expensive, since the electron and ion time scales are very different. An electron Boltzmann kinetic equation averaged over the fast electron bouncing and pitch-angle scattering was derived in order to develop an effective and operative tool for the fast modeling (FM) of low-pressure ECR discharges. An analytical solution for the EDF in a loss cone was derived. To check the validity of the FM, one-dimensional (in coordinate) and two-dimensional (in velocity) Monte Carlo simulation codes were developed. The validity of the fast modeling method is proved by comparison with the Monte Carlo simulations. The complete system of equations for FM is presented and ready for use in a comprehensive study of ECR discharges. The variations of plasma density and of wall and sheath potentials are analyzed by solving a self-consistent set of equations for the EDF.     

Optimization of a Raman/EDFA hybrid amplifier based on dual-order stimulated Raman scattering using a single-pump

Based on dual-order stimulated Raman scattering (SRS) of a single 1395 nm Raman fiber laser in 75 km single mode fiber and its corresponding dispersion compensation module, a hybrid Raman/Erbium doped fiber amplifier (EDFA) for long wavelength band (L-band) amplification is realized by inserting a segment of EDF within the span. By comparing the performance of gain and noise in four hybrid amplifiers with different span configurations, we find that the distribution of the secondary L-band amplification obtained from the EDF along the link has a great influence on the performance of the hybrid amplifier. Both gain and noise performance of hybrid amplifier can be improved significantly by optimizing the location of the EDF. Moreover, we can extend the flat gain bandwidth from L-band to central wavelength band (C-band) plus L-band by recycling the residual first-order SRS to pump a segment of EDF with proper length.     

Fiber-ring laser with tunable optical bistability

The structure of combining two segments of erbium-doped fiber (EDF) together—one EDF acting as an amplifier and the other as an absorber—has a special gain characteristic curve which has a maximum gain with an increase in the input signal power. This special gain characteristic curve can lead to an optical bistability (OB) phenomenon in a fiber-ring laser employing an EDF of this structure. By adjusting the pump light power injected into the second segment of the EDF, we can change the behavior of the absorber and can, therefore, control the range of the bistability region. A method is proposed to calculate the tunable optical bistability, and the calculation result is in accordance with our experiment.     

Passive Q-switching of a fiber laser using a side-polished birefringent fiber with index matching gel spread on the flat side

We experimentally demonstrate the use of a side-polished birefringent fiber with index matching gel spread on the flat side as a passive Q-switch for the implementation of an all-fiberized, erbium-doped fiber (EDF)-based Q-switched laser. It is shown that Q-switched pulses with a ~2.5-μs temporal width are readily achievable from an EDF ring cavity using the side-polished birefringent fiber-based Q-switch. The tuning capability of the pulse width and the repetition rate by changing the pump power is also investigated.     

Nuclear Symmetry Energy with QCD Sum Rule

We calculate the nucleon self-energies in an isospin asymmetric nuclear matter using QCD sum rule. Taking the difference of these for the neutron and proton enables us to express an important part of the nuclear symmetry energy in terms of local operators. Calculating the operator product expansion up to mass dimension six operators, we find that the main contribution to the difference comes from the iso-vector scalar and vector operators, which is reminiscent to the case of relativistic mean field type theories where mesons with aforementioned quantum numbers produce the difference and provide the dominant mechanism for nuclear symmetry energy.     

端面附近缺陷在掺铒光纤中引起的振荡

实验研究了由于掺铒光纤（ＥＤＦ）端面附近存在缺陷引起光反射而导致的振荡，这种振荡发生在掺铒光纤放大的自发辐射（ＡＳＥ）谱的峰值波长处，由于较长掺铒光纤的放大的自发辐射谱近似于其小信号增益谱，因此也可以认为发生在掺铒光纤放大器（ＥＤＦＡ）的最大增益处，对其增益产生不良影响。     

Deformation properties of lead isotopes

The deformation properties of a long lead isotopic chain up to the neutron drip line are analyzed on the basis of the energy density functional (EDF) in the FaNDF⁰ Fayans form. The question of whether the ground state of neutron-deficient lead isotopes can have a stable deformation is studied in detail. The prediction of this deformation is contained in the results obtained on the basis of the HFB-17 and HFB-27 Skyrme EDF versions and reported on Internet. The present analysis reveals that this is at odds with experimental data on charge radii and magnetic moments of odd lead isotopes. The Fayans EDF version predicts a spherical ground state for all light lead isotopes, but some of them (for example, ¹⁸⁰Pb and ¹⁸⁴Pb) prove to be very soft—that is, close to the point of a phase transition to a deformed state. Also, the results obtained in our present study are compared with the predictions of some other Skyrme EDF versions, including SKM*, SLy4, SLy6, and UNE1. By and large, their predictions are closer to the results arising upon the application of the Fayans functional. For example, the SLy4 functional predicts, in just the same way as the FaNDF⁰ functional, a spherical shape for all nuclei of this region. The remaining three Skyrme EDF versions lead to a deformation of some light lead isotopes, but their number is substantially smaller than that in the case of the HFB-17 and HFB-27 functionals. Moreover, the respective deformation energy is substantially lower, which gives grounds to hope for the restoration of a spherical shape upon going beyond the mean-field approximation, which we use here. Also, the deformation properties of neutron-rich lead isotopes are studied up to the neutron drip line. Here, the results obtained with the FaNDF⁰ functional are compared with the predictions of the HFB-17, HFB-27, SKM*, and SLy4 Skyrme EDF versions. All of the EDF versions considered here predict the existence of a region where neutron-rich lead isotopes undergo deformations, but the size of this region is substantially different for the different functionals being considered. Once again, it is maximal for the HFB-17 and HFB-27 functionals, is substantially narrower for the FaNDF⁰ functional, and is still narrower for the SKM* and SLy4 functionals. The two-neutron drip line proved to be A_drip²ⁿ = 266 for all of the EDF versions considered here, with the exception of SKM*, for which it is shifted to A_drip²ⁿ(SKM*) = 272.     

激光聚变黑腔中等离子体的热流研究

辐射流体采用限流的局域Spitzer-Harm(S-H)电子热流近似,在预估等离子体状态时可能与实验观察存在偏差.利用一维(1D3V)含碰撞的粒子模拟程序,研究了激光聚变黑腔中金等离子体的电子分布函数和电子热流.分析表明,在等离子体的冕区,α=Z(νos/νte)^2>1,电子分布函数表现为超高斯分布(m=3.34),克努森数λe/Le=0.011大于局域S-H理论的临界值2×10^-3.这导致了局域S-H电子热流远大于实际热流.这种实际热流受限现象将导致辐射流体模拟给出的冕区电子温度高于神光实验测量值.而在等离子体的高密度区域,电子分布函数仍表现为超高斯分布(m=2.93),克努森数λe/Le=7.58×10^-4小于局域S-H理论的临界值,限流的局域S-H电子热流具有一定的适用性.但电子热流严重依赖于限流因子,辐射流体模拟需要根据不同位置的光强和电子温度调整的大小.     

Modelling of multi-line Brillouin/erbium fibre lasers

Laser sources with unique properties can be produced using a combination of nonlinear Brillouin gain in single-mode optical fibre (SMOF) and gain in erbium-doped fibre (EDF). Narrow bandwidth nonlinear gain from stimulated Brillouin scattering in SMOF determines the wavelength of operation, and gain in EDF allows efficient operation and large power extraction. Various cascading schemes based on the Brillouin/erbium fibre laser (BEFL) as well as distinctive multi-wavelength versions of the BEFL were proposed, being able to produce 10GHz combs of over 30 lines at 1550 nm. These multi-wavelength sources may be of use in future dense wavelength-division multiplexing systems. We explore fundamental aspects of BEFLs configured to generate multiple wavelengths with particular focus on the effects of the Brillouin and EDF pumps on the number of lines and the relationship between the intensities of the individual lines in the comb.     

Passive erbium-doped fiber seed photon generator for high-power Er(3+)-doped fiber fluorescent sources with an 80-nm bandwidth

A novel structure that converts wasted backward amplified spontaneous emission (ASE) to seed photons for the amplifier stage is suggested for a high-power erbium-doped fiber (EDF) broadband source. A considerable increase in output power and bandwidth extension was achieved by placement of a segment of passive EDF in front of the amplifier stage, thus recycling backward ASE as the secondary pumping source for the passive EDF seed photon generator. Experimental results showed a dramatic increase in output ASE power of more than 10 dB for most radiation bands from 1540 to 1620 nm with the simple addition of an unpumped EDF segment to the ordinary fluorescence-source structure.     

Study of the amplification characteristics of a coaxial EDF with varying coupling conditions

A coaxial erbium doped fiber (EDF) designed to show inherent gain flattening for one of its propagating modes in general supports two or more modes with different gains. In this paper, we show that when such an amplifying coaxial EDF is spliced to a single mode transmission fiber carrying the signal, in general, more than one mode is excited each with its excitation coefficient strongly dependent on wavelength. Due to the interference between these modes, the amplified output coupled to an output single core transmission fiber can be a very sensitive function of the coaxial EDF length, especially around the phase matching wavelength (PMW), and does not show inherent gain flattening. However, due to interference between the two modes, the coaxial fiber acts as a band reject filter at the phase matching wavelength with attenuation and bandwidth depending on fiber parameters. This property can be employed for inherent gain flattening when both modes are excited.     

基于掺铒光纤/喇曼混合放大的光纤激光器布喇格光栅传感系统

提出了一种提高长距离光纤布喇格光栅信噪比以进行准分布测量的新方法.该方法基于掺铒光纤/喇曼混合放大的光纤激光器结构,掺铒光纤和滤波器构成的环形结构产生激光作为光源,喇曼光纤放大器对布喇格光栅信号进行低噪音的双向放大,置于远处的掺铒光纤利用剩余的泵浦功率产生自发辐射光和放大传感信号,为远处掺铒光纤之后的布喇格光栅传感器提供信号光以及补偿由于长距离传输造成的光纤损耗.实验显示,与使用宽带光源的传感方式相比,系统的性能得到显著提高,仅使用小功率泵浦,分布在50 km光纤上的FBG均获得了超过58 dB的优良信噪比.     

Enhancement of Gain in L-Band Bismuth-Based Erbium-Doped Fibre Amplifier Using an Un-pumped EDF and Midway Isolator

A hybrid L-band erbium-doped fibre amplifier (EDFA) with enhanced gain characteristic is demonstrated without a significant noise figure penalty. It uses a backward C-band amplified stimulated emission from both the ends of a bismuth-based EDFA system to pump an unpumped erbium-doped fibre (EDF) for gain enhancing. The maximum gain enhancement of 4.0dB is obtained at wavelength 1604nm with EDF length of 20m. The gain spectrum is reasonably fiat in this amplifier compared with the amplifier without an EDF. The gain varies from 27.4 dB to 30.2 dB at wavelength region 1564-1608 nm with incorporation of 20 m EDF. Noise figure also varies from 6.0 to 7.TdB at this wavelength region.     

Widely Tunable Fiber Ring Laser with High Concentration Erbium-Doped Fiber

We report a high power and widely tunable erbium-doped fiber (EDF) ring laser using 1480nm pump and high concentration EDF. Large tuning range up to 105nm (1513-1618 nm) has been obtained by optimizing of the EDF length.