真空中聚苯乙烯交联材料的沿面闪络特性

搭建了真空沿面闪络实验平台,在实验平台上对聚苯乙烯交联材料进行了真空沿面闪络性能测试,探讨了材料的真空沿面闪络电压强度与材料结构、材料内部微量杂质的关系。实验结果表明:随着聚苯乙烯材料交联程度的增加,其真空沿面闪络电压强度先增加后减少;聚苯乙烯交联材料分子链结构对其真空沿面闪络电压强度有重要影响;材料的真空沿面闪络电压强度还与交联材料内部异质分子数量有关系,微量异质结构的分子将导致沿面闪络电压强度的下降。     

真空中聚苯乙烯交联材料的沿面闪络特性

搭建了真空沿面闪络实验平台,在实验平台上对聚苯乙烯交联材料进行了真空沿面闪络性能测试,探讨了材料的真空沿面闪络电压强度与材料结构、材料内部微量杂质的关系。实验结果表明:随着聚苯乙烯材料交联程度的增加,其真空沿面闪络电压强度先增加后减少;聚苯乙烯交联材料分子链结构对其真空沿面闪络电压强度有重要影响;材料的真空沿面闪络电压强度还与交联材料内部异质分子数量有关系,微量异质结构的分子将导致沿面闪络电压强度的下降。     

Spectroscopy of composite scintillators

The spectral and temporal characteristics of X-ray luminescence of composites consisting of microparticles of “heavy” components (oxides, fluorides, sulfates) and an organic polymer binder containing optically active impurities have been investigated. It has been found that, in the case of pulsed X-ray excitation of the composites with a photon energy of 130–150 keV, the fast component (τ < 10 ns) of the luminescence arises whether or not the “heavy” component of the composite is doped with an optically active impurity. A mechanism has been proposed for the formation of the fast component of the luminescence: electrons and low-energy X-ray photons generated during the interaction of high-energy X-ray photons with the “heavy” component of the composite are effectively absorbed by the polymer binder and, thus, induce its luminescence. It has been shown that, in order to produce a composite-based fast scintillator with a high light yield, it is necessary to use a binder prepared from an organic material with a short scintillation decay time and another component prepared from a compound whose composition includes an element of a large atomic number Z.     

Investigation of vacuum polarization in t-channel radiative Bhabha scattering

We discuss the possibility of a precision measurement of vacuum polarization in t-channel radiative Bhabha scattering at a high luminosity collider. For illustration, the achievable precision is estimated for the BaBar experiment at PEP-II and for the OPAL experiment at LEP. Received: 6 June 2001 / Published online: 21 September 2001     

The physics of inorganic scintillators

Boston University, Department of chemistry, Boston, MA 02215, USA. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 4, pp. 209–231, July–August, 1995.     

Investigation of water decomposition by vacuum ultraviolet radiation

The concentrations of products of liquid and gaseous water decomposition under the action of VUV (7n = 172 nm) radiation are calculated. It is shown that the VUV radiation causes efficient formation of highly reactive *OH radicals. The application the products of water photodecomposition is exemplified by the possibility of degradation of polychlorinated biphenyl upon interaction with these products.     

Core–valence luminescence in scintillators

The state of the art of core–valence luminescence (CVL) in a number of halides (BaF₂, CsCl, LiBaF₃, etc.) is analysed. The following items are discussed: common properties of CVL, a suppression of slow emission component in BaF₂, an effect of secondary excitation density on intensity and decay profile of the emission, a neutron–gamma discrimination, spectrum simulations, impurity-associated CVL, an origin of slow- and long-wavelength CVL components, a lattice relaxation, vibrations of lattice environment and phonon broadening of the emission bands.

Experimental results on impurity-associated CVL of Rb_1−xCs_xBr (x<0.2) are presented and discussed. It is shown that the impurity-associated luminescence gives us a convenient way for the improvement of light output and variation of the emission wavelength of the scintillators.     

聚苯乙烯相对分子量对薄壁聚苯乙烯空心微球质量的影响北大核心CSCD

激光惯性约束聚变(ICF)作为探索受控核聚变的有效途径,有望获得清洁无污染的能源,而薄壁聚苯乙烯(PS)空心微球是ICF物理实验中亟需的一类微球。针对薄壁空心微球因径厚比(直径/壁厚)增大导致其在干燥、使用中易开裂的问题,研究了PS原料对薄壁微球质量的影响,探讨了其影响机制。结果表明:当油相PS质量分数为4%时,随着油相粘度增加,W1/O/W2复合乳粒稳定性逐渐提高;当油相质量分数不低于8%时,复合乳粒稳定性良好。PS原料对微球表面粗糙度影响较小,微球球形度和壁厚均匀性随初始油相粘度的增大而降低,在干燥过程中微球开裂率随原料力学性能提高而减小。在外水相中引入氟苯(FB)液滴,延缓固化速率,可减小油相粘度增加对微球球形度和壁厚均匀性的不利影响。     

Development of muon polarization preserved scintillators

We measured the residual μ⁺ polarizations in various liquid scintillators to search for an ideal material for an active muon stopper in which the muon spin polarization can be preserved and at the same time their energy loss and tracks can be measured by scintillation lights from the stopper material. We found the residual polarizations of mineral‐oil base liquid scintillators were \sim 4 times larger than that of a plastic scintillator. Further increase of the residual polarization was observed with a mixture of CCl₄. This revised version was published online in August 2006 with corrections to the Cover Date.     

Spectroscopy of electron-induced fluorescence in organic liquid scintillators

Emission spectra of several organic liquid-scintillator mixtures which are relevant for the proposed LENA detector have been measured by exciting the medium with electrons of ∼10 keV. The results are compared with spectra resulting from ultraviolet light excitation. Good agreement between spectra measured by both methods has been found.     

Investigation of ion behavior associated with anode-spot modetransition in vacuum arcs

The ion behavior phenomenon associated with transitions of the anode discharge mode to the anode-spot mode is studied by measuring the wall ion current and by spectroscopic observation in vacuum arcs. The anode mode transfers when the wall ion current attains a certain magnitude that is independent of the cathode, but dependent on the anode. The ion-current function to the arc current increases when the arc current increases in the diffuse arc. Spectral-line intensity of Cu III emitted from the plasma in the anode region increases with an instantaneous arc current of a 5-kA peak (kAp) sinusoidal half-wave. These findings suggest an idea for the mode transition, that an ion generation region appears, and that an increase in the ion density produces a positive potential hump near the anode, which results in the negative anode voltage drop triggering the mode transition. After the mode transition, an arc current is found to reduce the ion current near the crest of a sinusoidal current in a copper arc. This appears to be significant for the arc on a small anode. The decrease in the ion current is attributed to the recombination of ions decelerated by anode vapor with electrons emitted from the hot spot on the anode     

Investigation of polyaniline films produced by vacuum deposition method

Using FTIR and optical spectroscopy techniques, as well as electron scanning microscope, we investigated polyaniline films obtained by the method of fractional thermal vacuum deposition. The structure of produced polyaniline films depends essentially on the deposition temperature and molecular weight of the initial polymer. For a polymer with low molecular weight at temperature below 250°C a homogeneous oligomeric film is produced. At higher temperatures (higher than 300°C) linkages of oligomeric fragments occur leading to appearance of more complex structural formations. This is reflected in the morphology of films deposited at different temperatures. The films have a high transparency and relatively high, for polymers, index of refraction in the visible and near infrared ranges of spectrum.     

论管状电阻网络的阻值

利用周期性条件严格地计算了管状电阻网络的电阻问题,得到了管状网络中任意两点间阻值与管状网络周期的函数关系式.同时借助三维图,形象地分析了周期性条件对管状电阻网络阻值的影响,并指出无限大平面和无限长梯状电阻网络是无限长管状电阻网络的特例.     

On the necessity of light transport simulation in scintillators

In this study, the light transport simulation in scintillators is introduced, the wavelength-dependencies in the process are taken into account, the effect of different shapes/lengths of lightguides on the response of the scintillation detectors are investigated and finally the need for such a simulation in addition to the particle transport simulation in a perfect response function predicting code is explained.