Intense slow positron production at the 15 MeV LINAC at Argonne National Laboratory

An intense slow positron beam using a 15 MeV LINAC (average current 1.25 × 10¹⁵ e⁻/s) at the Radiation and Photochemistry Group, Chemistry Division of Argonne National Laboratory (ANL) has been proposed and studied. Computer simulated results optimizing the positron yield and distribution of energy and angle show that a slow positron production at 10¹⁰ e⁺/s is possible. A proposed design of an intense slow positron beam with optimal conditions of incident electron, converter/moderator configurations, and extraction/transportation is presented.     

Application of egs4 computer code for determination of gamma ray spectrum and dose rate distribution in gammacell 220

The EGS4 a Monte Carlo electron-photon transport simulation package together with a locally developed computer program “GCELL” has been used to simulate the transport of the gamma rays in Gammacell 220. An additional lead attenuator has been inserted in the chamber, has been included for those cases where lower dose rates were required.

For three cases of 0, 1.35 and 4.0 cm thickness of added lead attenuators, the gamma spectrum, and dose rate distribution inside the chamber have been determined. For the case of no attenuator present, the main shield around the source cage has been included in the simulation program and its albedo effects have been investigated.

The calculated dose rate distribution in the Gammacell chamber has been compared against measurements carried out with Fricke, PMMA and Gafchromic film dosimeters.     

生产井井间距离对增强型地热系统影响分析

为揭示生产井井间距离对增强型地热系统(EGS)的影响，以中国青海共和盆地增强型地热系统为研究对象，采用数值模拟方法，建立了考虑生产井井间距离不同的三维热-固-流耦合热采模型。分析得到生产井井间距离为600 m, 700 m, 800 m, 900 m, 1000 m对EGS温度场、产出流体温度、储层寿命、总产热量、最大主应力以及最大主应变影响规律。研究结果表明，随着热开采进行，储层裂隙周围岩体温度下降，产出温度随开采年限增加而降低；从产出温度、储层寿命和总产热量三方面考虑，最优生产井井间距离为800 m;生产井井间距离对第一主应力及第一主应变影响显著，应结合实际情况选择最优生产井井间距离。