Correlation of Electron Beams and Hard X‐ray Emissions in ISTTOK Tokamak

The paper reports on experimental studies of electron beams in the ISTTOK tokamak, those were performed by means of an improved four‐channel detector. The Cherenkov‐type detector measuring head was equipped with four radiators made of two types of alumina‐nitrate (AlN) poly‐crystals: machinable and translucent ones, both of 10 mm in diameter and 2.5 mm in thickness. The movable support that enabled the whole detectors to be placed inside the tokamak vacuum chamber, at chosen positions along the ISTTOK minor radius. Since the electron energy distribution is one of the most important characteristics of tokamak plasmas, the main aim of the study was to perform estimations of an energy spectrum of the recorded electrons. For this purpose the radiators were coated with molybdenum (Mo) layers of different thickness. The technique based on the use of Cherenkov‐type detectors enabled the detection of fast electrons (of energy above 66 keV) and determination of their spatial and temporal characteristics in the ISTTOK experiment. Measurements of hard X‐rays (HXR), which were emitted during ISTTOK discharges, have also been performed. Particular attention was paid to the correlation measurements of HXR pulses with run‐away electron beams. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A quantum dissipative system in an anisotropic non-linear absorbing environment

A canonical quantization scheme is represented for a quantum system interacting with a non-linear absorbing environment. The environment is taken anisotropic and the main system is coupled to its environment through some coupling tensors of various ranks. The non-linear response equation of the environment against the motion of the main system is obtained. The non-linear Langevin-Schrödinger equation is concluded as the macroscopic equation of motion of the dissipative system. The effect of non-linearity of the environment is investigated on the spontaneous emission of an initially excited two-level atom imbedded in such an environment.     

Real time NDE of laser shock processing with time-of-flight of laser induced plasma shock wave in air by acoustic emission sensor

Acoustic emission sensor is used to research the time-of-flight of the shock wave induced by laser-plasma in air for real time nondestructive evaluation (NDE) of laser shock processing. The time-of-flight of the shock wave propagating from the source to the sensor declines nonlinearly and similarly at the different distances for different laser energies. The velocity of the shock wave at the distance of 30 mm increases faster than that of the distance of 35 mm. The relationship between the laser energy and the distance is almost linearly when the signal with distortion is measured by acoustic emission sensor. Finally, Taylor solution is used to analyze the experimental results, and the empirical formula between the energy of the shock wave and the laser energy is established, which will provide a theoretical basis for real time NDE of laser shock processing.     

35MeV/u 40 Ar+197 Au反应中热核的碎裂密度

许多提取核反应过程中熵产生的方法只适用于高能核反应过程 ,而约化d的产额方法可以用于较低能量的重离子核反应中 .对于 3 5MeV/u40 Ar+ 197Au的核反应过程 ,利用这种方法所得的熵和约化带电粒子多重性提取的熵结果一致 .对于后角热核发射体系 ,实验提取的核温度为 ( 4.7± 1 .2 )MeV ,熵为S/A =2 .5± 0 .5,根据实验提取的熵和核温度可以确定其碎裂密度小于 0 .1 ρ0     

35MeV/u~(40)Ar ~(197)Au中的熵产生

根据量子统计模型 (QSM )的计算分析 ,找到了一个提取核反应过程中熵产生的新的可观测量 .核反应过程中约化d的产额d/ (d t 3 He 4 He)和熵有单调的函数关系 ,并且和体系的碎裂密度 (ρ/ ρ0 )及体系的N/Z都无关 ,可以作为提取核反应过程中熵产生的一个观测量 .和目前已经有的其他方法相比 ,约化d产额这一提取熵方法可以用于较低能量的重离子核反应中 ,并且数据处理分析简单 .对于 35MeV/u4 0 Ar 197Au的核反应过程所提取的熵和利用约化带电粒子多重性提取的熵结果一致 .结合后角类靶热核发射体系实验提取的同位素核温度为 4 7±1 2MeV及S/A =2 5± 0 5 ,根据熵和核温度的关联关系 ,可以确定其Breakup密度接近但小于 0 1(ρ/ ρ0 )     

Properties of noninteger moments in a first passage time problem

We calculate the moments t ^q , whereq is not necessarily an integer, of the first passage time to trapping for a simple diffusion problem in one dimension. If a characteristic length of the system isL and t _q ~L (q) asL, then we show that there is a phase transition atq=q _c such that whenq<q _c ,(g)=0, and forq>q _c , (q) is a linear function ofq. These analytical results can be used to explain results for large moments for diffusion on a hierarchic structure. We also show how to calculate noninteger moments in terms of characteristic functions.     

Back focal plane imaging of Tamm plasmons and their coupled emission

The unique optical properties of Tamm plasmons (TPs) – such as flexible wavevector matching conditions including inplane wavevector within the light line, and existing both S‐ and P‐polarized TPs − facilitate them for direct optical excitation. The Tamm plasmon‐coupled emission (TPCE) from a combined photonic–plasmonic structure sustaining both surface plasmons (SPs) and TPs is described in this paper. The sensitivity of TPCE to the emission wavelength and polarization is examined with back focal plane imaging and verified with the numerical calculations. The results reveal that the excited probe can couple with both TPs and SPs, resulting in surface plasmon‐coupled emission (SPCE) and TPCE, respectively. The TPCE angle is strongly dependent on the wavelength allowing for spectral resolution using different observation angles. These Tamm structures provide a new tool to control the optical emission from dye molecules and have many potential applications in fluorescence‐based sensing and imaging.     

Synthesis of resonant cavities having continuum spectra by genetic algorithm

This paper proposes a novel method for generating continuum spectra with possible applications in WDM access networks. This new method would allow the development of a simple continuum laser structure with better performances in terms of cost and simplicity than those of present supercontinuum sources. In this aim, we will analyze the possibility to broaden the resonant modes of a Fabry–Perot cavity by operating only on the design of one of the cavity's Bragg mirrors. Firstly we considered the conditions which a Bragg grating must satisfy in order to broaden the resonant modes of a resonant cavity. Because an exact solution is not physical possible, the genetic algorithm is the best available tool for the design of such a grating. An active medium is then added inside the cavity and its behavior below threshold is simulated. The spectra thus simulated are continuum over 5–15 nm.     

Acoustic source localization

In this article different techniques for localizing acoustic sources are described and the advantages/disadvantages of these techniques are discussed. Some source localization techniques are restricted to isotropic structures while other methods can be applied to anisotropic structures as well. Some techniques require precise knowledge of the direction dependent velocity profiles in the anisotropic body while other techniques do not require that knowledge. Some methods require accurate values of the time of arrival of the acoustic waves at the receivers while other techniques can function without that information. Published papers introducing various techniques emphasize the advantages of the introduced techniques while ignoring and often not mentioning the limitations and weaknesses of the new techniques. What is lacking in the literature is a comprehensive review and comparison of the available techniques; this article attempts to do that. After reviewing various techniques the paper concludes which source localization technique should be most effective for what type of structure and what the current research needs are.