The Hypothesis of Strangelets in the Cosmic Rays

The experimental confirmation of the presence of a penetrating component in cosmic rays is presented. Unlike previous experiments, it is shown that the component is not born in the lead of the detectors, but is present in the primary radiation. In this case, the particles forming the penetrating component must be stable. Among the nuclear-active particles, there are only two stable variants. These are nuclei, among which the most penetrating are protons, and hypothetical particles of strange quark matter—strangelets (quasi-nuclei). The analysis of the muon component is not consistent with the proton variant.

     

Characteristics of the underwater explosion of a nonideally detonating aluminum-rich energetic material

An experimental study of the characteristics of the explosion of mixtures of ammonium perchlorate, aluminum, and nitromethane with a large excess of aluminum (1.45 to 1.66 g/cm³ in density) confined in plastic enclosures and immersed in small elastic-wall reservoirs with water is conducted. It is shown that composite charges, 20 mm in diameter, surrounded by a water layer of thickness 20–30 cm and detonate in a nonideal detonation mode. High-speed cinematography records show the possibility of the intense mixing of the detonation products with the surrounding water and of the burning of excess aluminum particles in a heterogeneous cloud. The time scales of the development of secondary energy release by burning of aluminum particles in water are estimated. The possibility of controlling the characteristics of the pressure waves generated by the explosion, for example, by means of a preliminary bubbling of the water with air near the charge, is demonstrated.     

A radial compression scheme for cooled antiprotons

A novel method is proposed for achieving a fast and efficient radial compression of antiproton clouds trapped and cooled in high magnetic field. The basic operation takes place in a low field solenoid during the transfer of the cooled antiprotons from one trap to the next. It makes use of a special device that imparts to the particles a transverse momentum which compensates exactly their initial generalized momentum. They can therefore be focused onto the solenoid axis and injected in the next high field region with a relatively small radial envelope. After standard trapping and cooling procedures a strongly radial extension is obtained. The operation can be repeated to lead to very small size of the final antiproton cloud. It can be estimated that an initial 1 cm radial extension can be reduced to 1 mm in a first stage and to less than 0.1 mm in a second stage. In this way highest densities (approaching the space charge limit) of trapped antiprotons can be obtained in a relatively short time.     

Combined mass spectrometer and electron spectrometer for investigation of solids

The possibility to develop the electron-and-ion energy analyzer and mass spectrometer combined in one optical system for the investigation of the properties of solids has been considered. This device allows one to obtain information on the chemical composition and energy spectrum for all the particles emitted by the surface of a solid subjected to various effects in one experiment. The combined spectrometers are based on the source of the particle flux, which transforms the mass spectrum into the energy spectrum due to the effect of electric-field pulses on the ion flux, and the high-resolution electrostatic energy analyzer. The particles appear in the source as a result of the interaction of the exciting radiation from an independent source with the surface of the solid under study. The type of exciting radiation (fluxes of ions, atoms, electrons, and laser radiation) is chosen depending on the goals of the study. Numerical modeling of the device operation, which confirms the possibility of its implementation in the form of a compact informative system for the investigation of characteristics of solids, has been performed.     

A durable plastic substrate for surface-enhanced Raman spectroscopy

A novel durable substrate has been prepared for surface-enhanced Raman spectroscopy (SERS). The substrate is fabricated by reduction of silver nitrate using poly(vinyl pyrrolidone) (PVP) polymer as stabilizers. The SERS-active particles are based on poly(methylmethacrylate) (PMMA) materials, producing stable and optically translucent substrates. The stability of silver particles on the substrate was demonstrated by characterizing the localized surface plasmon resonance (LSPR) band of the elemental silver particles. The SERS activity was evaluated by detecting the signal from Raman probe molecules, Rhodamine 6G (R6G). This plastic substrate material is easy to prepare, inexpensive, and sturdy for SERS applications.     

Experimental Results of Radar Sounding of Subsurface Oil-Polluted Areas

We present experimental estimates of the possibility to use an adapted ground penetrating radar (GPR) for mapping subsurface zones (lenses) polluted by oil products as a result of ecological accidents. The radar was tested at the site of a large lens with air kerosene at a depth of about 6 m. On the basis of comparison of radar measurements and geological data obtained by well-boring it is shown that use of GPRs for mapping subsurface lenses with oil products is expedient.     

Description of a biofluorescence optical particle counter

A bioaerosol fluorescence detection system is being constructed using an ellipsoid reflector-based optical particle counter. The flux measuring device is to size submicron marine spray aerosol particles smaller than 100 nm in diameter. It will simultaneously non-destructively excite and detect fluorescence from organic matter contained in the aerosol. Chlorophyll-a is the primary fluorophor target, used as a marker for detecting phytoplankton (or derivatives thereof) in the particles. Particles have been sized to 500 nm in diameter and fluorescence detection testing is underway. The device will aid the quantification and identification of this organic material contained in marine spray aerosols, providing improved inputs into climate models and air quality assessments.     

Alpha particle detector based on micropixel avalanche photodiodes

The main goal of this work is to study the possibility of detecting alpha particles with a micropixel avalanche photodiode (MAPD) in combination with Lutetium Fine Silicate (LFS) scintillators (500 μm thick). The results show that alpha detectors based on the MAPD are expected to be useful in many applications: public security (associated particle imaging for explosives and drugs detection), radioactive contamination monitoring in various environments, and detection of charged particles from nuclear reactions.     

SCINTILLATION COUNTER ARRAY LOCALIZATION SYSTEM

A scintillation counter array localization system, i.e, scintillation counter hodoscope, was studied and made for selecting events and triggering the streamer chamber in 1980. With this facility the penetrating position of the charged particles can be determined and it can be used as a trigger counter too. As soon as the charged particles penetrated this array and other scintillation telescope, the generated coincidence signal triggers the control system of the streamer chamber with the time delay 74 ns.On the other hand, this system also has a ability of selecting charged particle number penetrating the counter array, thus, the streamer chamber is able to record the event with certain multiplicity.This hodoscope contains a 8×8 scintillation counter array. Each plastic scintillator (type ST401) has the dimensions of 40×5×0.6 cm³ and the type of photomultipliers used is GDB50. The array area is 40×40 cm².The fast electronics and data handling system were made by ourselves. The whole system works well during the test with the on-line microcomputer TRS-80 and is not expensive.     

CYSP: A new cylindrical directional neutron spectrometer. Conceptual design

This communication describes in detail the design of a new cylindrical neutron spectrometer (CYSP) embedding 7 active thermal neutron detectors in a moderating structure made of polyethylene, borated plastic and lead. The device provides a strong directional response within the energy interval from thermal to hundreds of MeV, being nearly insensitive to neutrons coming from directions other than the cylinder axis with energies up to about 10 MeV. Therefore it will be especially suitable for applications where the neutron spectrum as a function of the emission angle needs to be measured. The Monte Carlo transport code MCNPX has been used to reach the final configuration for the spectrometer in terms of size, collimator, and arrangement of borated plastic and lead layers, number and position of the detectors. Moreover, MCNPX has been also used to calculate the response matrix of the instrument.     

室内空气中颗粒状污染物的计数技术

室内环境空气污染对人体健康影响很大。文中指出影响人体健康的致病因子,并详细分析先进的光散射理论,在此基础上建立异轴采光数学模型,分析单个微粒的光通量和粒径之间的关系。鉴于单个颗粒的散射光信号很弱,本文提出一种方法,把光辉器的内腔（开放腔）作为颗粒注入区,利用激光器的内腔功率谱密度远大于腔外功率密度的特点,结合先进的激光散射理论,对空气中的颗粒进行计数的粒径分档。实践证明,该方法对较小粒径的颗粒检测     

HL-2A装置偏滤器位形超声分子束注入深度观测

用22道Hα辐射测量阵列观测了HL-2A装置偏滤器位形超声分子束的注入过程。观测结果表明：在HL-2A装置偏滤器位形下,当分子束注入气源压强大于1MPa时,Hα辐射沿径向分布存在两个峰值,其第二个Ha辐射峰值位于r/a~0.8附近,表明大部分氢粒子在等离子体边缘(SOL区域)即被离解或电离,但仍有部分氢粒子沉积在分界面内5cm。     

Multiple penetrating particles with narrow separation associated with extensive air showers (EAS)

An experiment has been carried out at a vertical depth of 580 m.w.e. at Kolar Gold Fields, to investigate various characteristics of energetic muons (E _mln ⋍ 150 GeV) associated with extensive air showers (EAS). Double parallel penetrating particles with narrow separations (<1m) have an exponential decoherence distribution withe-folding separation of ⋍ 25 cm.     

一种改进的光滑粒子流体动力学前处理方法

为了便于对任意边界形状的计算域快速地布置均匀粒子,提出了一种改进的光滑粒子流体动力学前处理方法.该方法是在2012年Colagrossi等提出的算法基础上进行改进后得到的.Colagrossi等提出的算法能够计算一些简单外形分布比较均匀的粒子.然而当光滑长度与初始粒子间距的比值较大时该方法在计算过程中会出现较强的数值震荡问题,收敛速度慢;而且在计算过程中可能会遭遇流体粒子穿透固体壁面的问题.本文通过引入未知因素修正的平滑粒子动力学模型来提高计算稳定性,并通过对边界附近的流体粒子施加边界力来避免流体粒子穿透固体壁面.算例验证结果表明,利用改进后的光滑粒子流体动力学前处理方法能够快速地对各种边界形状的计算域分布均匀粒子,并且避免了流体粒子穿透固体壁面的问题.     

A framework for statistical modelling of plastic yielding initiated cleavage fracture of structural steels

The well established consensus that cleavage fracture is preceded by plastic deformation in structural steels implies that plastic yielding is the threshold stress state for a volume element to incur cleavage fracture. An accurate compliance with this consensus underlies the normalisation of cumulative cleavage fracture probability and the justification of constraint effect on cleavage fracture. These understandings lead to the proposal of a framework for statistical modelling of cleavage fracture in structural steels. The framework takes the spatial microcrack distribution into account to formulate the cumulative failure probability model that allows for a pertinent physical interpretation of Weibull statistics, and derives the fracture probability of an elemental volume in conformity with the yielding condition from a set of commonly adopted microcrack size or strength distributions. Alternative approaches to calibrating model parameters are suggested based on frequency analysis of brittle particles as cleavage initiators and on statistical analysis of cleavage fracture stress. The strict adherence to plastic yielding as a prerequisite to cleavage fracture also reveals the probabilistic nature of notch brittleness and ductile-to-brittle transition behaviour.     

一种基于SiPM的新型起始时间探测器研制

本文介绍了一种新型起始时间探测器的研制。该探测器的灵敏面积为60 mm×60 mm,利用120根直径为1 mm的塑料闪烁光纤分成两层错位紧致排布,且上下相邻的3根光纤作为一个探测单元,每个探测单元均采用硅光电倍增管从双端读出信号。采用90Sr放射源对单根光纤进行了性能测试,结果表明,闪烁光沿着光纤方向的有效传播速度约为17 cm/ns,对应的时间分辨优于600 ps。此外,利用中国科学院近代物理研究所第二条放射性束流线（RIBLL2）提供的240 MeV/u的15N次级束研究了该探测器的性能。束流测试结果表明:该探测器的时间分辨为（150±15）ps,纵向位置分辨为（1.8±0.2）cm,并且结合该探测器以及RIBLL2束流线外靶实验终端上的其他探测器,可以对实验中产生的5 ≤ Z ≤ 8的各种同位素进行非常好的粒子鉴别。     

Motion of the spin of particles and nuclei of arbitrary spin in the electric field of crystals

The possibility of verifying the conclusions of quantum theory on the motion of the spin of particles and nuclei of arbitrary spin in an electric field is analyzed. The theory predicts that the planar channeling of particles and nuclei with higher spins (one or more) through straight crystals is accompanied by the rotation of their spin. For some nuclei, the spin-rotation angle per unit length is about 10^?1 rad/cm. For ultrarelativistic nuclei undergoing planar channeling through bent crystals, the spin-rotation angle per unit length is on the order of 1 rad/cm, which makes it possible to verify the validity of the Bargmann-Michel-Telegdi equation for particles and nuclei of higher spins.     

The “filler-effect” in organic ionic plastic crystals: Enhanced conductivity by the addition of nano-sized TiO2

The addition of nano-sized ceramic particles to the plastic crystal ethyl-methyl pyrrolidinium bis(trifluoromethane sulfonyl)amide (P₁₂TFSA) has been investigated by means of DSC and conductivity. The thermal behaviour of the plastic crystal as a function of filler content suggests that the filler particles decrease the onset temperature of the melting slightly at high loadings, however they do not decrease the crystallinity of the material. Furthermore, the IV → III transition decreases in intensity, indicating that the addition of filler increases the possibility for the crystal to remain in metastable rotator phases also at lower temperatures. The conductivity shows a more than one order of magnitude increase with the addition of filler, with a filler concentration dependence that levels out above ∼ 10 wt.% TiO₂.     

墙体对微波脉冲的衰减特性

 研究墙体对微波脉冲的衰减特性，测量了微波脉冲垂直入射墙体后的脉冲信号，经过计算得到普通砖混墙、普通钢筋混凝土墙、钢筋网混凝土墙对窄带微波和超宽带微波的衰减值；分析了微波脉冲穿越不同墙体的频谱变化。研究结果表明，普通钢筋混凝土墙和普通砖混墙对窄带微波脉冲的衰减为0.342～0.699 dB/cm，对超宽带信号的衰减为0.134～0.183 dB/cm。钢筋网混凝土墙（厚65 cm）对超宽带信号的衰减较大（29.07～45.79 dB），同时使穿透墙体的超宽带信号频率分布向高频位移。