The practice for eight-year operation of the cobalt-60 irradiation facility at Beijing Radiation Application Research Center

The radiation facility was made by Sulzer Company in Switzerland. The designed capacity is 3.7 × 10¹⁶Bq( 1MCi) and 12.21 × 10¹⁵Bq(330kCi)of Cobalt -60 source was loaded at the first phase. Current cobalt -60 source-loading is 2.4 × 10¹⁶Bq(650kCi). The equipment assembling and installation regulating and testing were completed at the end of 1988. The facility was put into commissioning in 1989. It operates 7000–8000 hours per year. The facility has been utilized to carry out many research work and irradiate many kinds of items. Lots of economical benefits have been gained since then. Now it is becoming a radiation processing model base in China. This paper summarized the strong and weak points of the design of the facility through in eight years' practice and analysed the economical benefits.     

激光感生碰撞能量转移的四能级理论模型

首次考虑了两个中间态对激光感生碰撞能量转移的影响，发展了激光感生碰撞能量转移的四能级理论模型，推导出态振幅的运动方程，并给出碰撞截面的近似表达式，通过对Ｅｕ－Ｓｒ和Ｃｓ－Ｓｒ系统的数值计算表明，当频率差│ω２１│大小和│ω４３│可以相比时，利用三能级近似理论就难以获得令人满意的计算结果，而四能级理论模型则适合于任何情况下的激光感生碰能量转移。     

用有效折射率／有限元法设计1．55μmTi：LiNbO_3单模条波导及其方向耦合器

应用有效折射率／有限元法（ＥＩ－ＦＥＭ），考虑到ＬｉＮｂＯ３晶体和Ｔｉ扩散的各向异性，折射率增量与寻常光、非寻常光及波长色散的关系，设计了１．５５μｍ光波长下工作的ｚ切ｙ传播Ｔｉ：ＬｉＮｂＯ３单模条波导的制备参数，计算和分析了其单模特性、模式场分布及其变化规律．扩展了ＥＩ－ＦＥＭ，将其用于求解耦合波导系统，确定了方向耦合器的耦合长度及其波长色散特性．     

Picosecond four-wave mixing reflectivity of GaAs at 1.06 μm

The picosecond degenerate four-wave mixing reflectivity of semi-insulating gallium arsenide at 1.06 m is calculated in this paper. The dependence of the reflectivity on the pump and signal fluences is measured. Reflectivities of more than one are possible. The Fourier components of the excited-carrier densities are calculated as a function of the pump fluence. The wavefront-correction property of this reflectivity is demonstrated with a lens group in the signal beam.     

Thermodynamic properties of aqueous mixtures of LiCl and Li2SO4 at different temperatures

Emf measurements were made on the cell without liquid junction: Li?ISE LiCl(m₁), Li₂SO₄(m₂) Ag/AgCl. The performances of the electrode pairs constructed in our laboratory were tested and exhibited near-Nernstian behavior. The mean activity coefficients of LiCl for the system Li⁺?Cl^??SO ₄ ^2? ?H₂O have been investigated by the emf values at temperatures of 0, 15, 35°C and constant total ionic strengths of 0.05, 0.1, 0.5, 1.0, 2.0, 3.0 and 5.0 mol·kg^?1. The activity coefficients decrease with increasing temperature and the ionic strength fraction of Li₂SO₄ in the mixtures. The thermodynamic properties are interpreted by use of Harned's empirical equations and Pitzer's ion interaction approach including the contribution of higher order electrostatic terms. The experimental results obey Harned's rule and are described by using Pitzer equations satisfactorily. The activity coefficients of Li₂SO₄, the osmotic coefficients and the excess free energies of mixing for the system in the experimental temperature range were reported.     

Kinetics of the photodissociation iodine laser with slow pumping

Systematic calculations of maximum inversion were performed for iodine photodissociation laser in dependence on the mixture composition. The flash-lamp radiation was modelled as emanating from an optically thin Xe plasma. Duration of the pumping pulse is about 300 s. The sensitivity of the model to the values of kinetic constants was also tested.     

Nonlinear supersymmetry at HERA-energies

Some consequences of a model whereN=1 supersymmetry is realized nonlinearly are worked out forep-collisions at HERA-energies. The model contains in addition to the standard particles one Goldstone-fermion λ, a neutrino-like Majoranaparticle. The existence of such a particle would be signalled by events with large missing energy and momentum. We present detailed predictions for the following special kinematic regions: (1) events with a tagged small angle electron and a largeE _T jet, (2) events with a large angle electron and a small angle tagged exclusive proton, (3) events with a tagged small angle electron and a tagged small angle exclusive proton. We indicate the region in coupling constant and mass of the Goldstone-fermion which can be explored at HERA and compare with the limits obtainable from existing data one ⁺ e ^? and \(p\bar p\) collisions at high energies.