在ICOOL中用ELMS进行液氢μ子冷却的从头算模拟
Ab Initio Liquid Hydrogen Muon Cooling Simulations with ELMS in ICOOL
摘要：
本文给出了μ子通过液氢的新的理论结果，这些结果已在最近的实验中得到证实。这些被用来证明，μ子束可以被压缩电离冷却更有效地比以前的计算所建议的。μ子冷却依赖于μ子能量损失和散射的微分截面。我们从第一性原理和原子数据计算了液态H2的这个截面，避免了传统的假设。然后，通过折叠导出能量损失和散射在mm尺度厚度中的2-D概率图，并存储在数据库中。大的能量损失和散射之间的一阶相关性被发现为H2，这是在其他模拟中不存在。这个代码被命名为ELMS，能量损失和多重散射。单粒子轨迹可以通过蒙特卡罗方法从该数据库中以1 mm或更小的尺度进行采样来跟踪。6-D μ子冷却的显着改善预测与以前的预测的基础上GEANT。这是在各种几何检查。发现大的相关效应对冷却只有很小的影响。在MUSCAT实验中观察到的液态H2的实验散射最近被报道与ELMS预测吻合良好，但与GEANT模拟吻合不佳。
英文摘要：
This paper presents new theoretical results on the passage of muons through liquid hydrogen which have been confirmed in a recent experiment. These are used to demonstrate that muon bunches may be compressed by ionisation cooling more effectively than suggested by previous calculations. Muon cooling depends on the differential cross section for energy loss and scattering of muons. We have calculated this cross section for liquid H2 from first principles and atomic data, avoiding traditional assumptions. Thence, 2-D probability maps of energy loss and scattering in mm-scale thicknesses are derived by folding, and stored in a database. Large first-order correlations between energy loss and scattering are found for H2, which are absent in other simulations. This code is named ELMS, Energy Loss & Multiple Scattering. Single particle trajectories may then be tracked by Monte Carlo sampling from this database on a scale of 1 mm or less. This processor has been inserted into the cooling code ICOOL. Significant improvements in 6-D muon cooling are predicted compared with previous predictions based on GEANT. This is examined in various geometries. The large correlation effect is found to have only a small effect on cooling. The experimental scattering observed for liquid H2 in the MUSCAT experiment has recently been reported to be in good agreement with the ELMS prediction, but in poor agreement with GEANT simulation.
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