Dependence of secondary electron emission on the emergent angle of 2.5-MeV protons penetrating a thin carbon foil
Dependence of secondary electron emission on the emergent angle of 2.5-MeV protons penetrating a thin carbon foil
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二次电子发射对穿透薄碳箔的 2.5 MeV 质子出射角的依赖性
DOI：
10.1103/physreva.68.052901
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
N. Sakamoto
中科院分区：
文献类型：
--
作者：
H. Ogawa;H. Tsuchida;N. Sakamoto
用2.5MeV质子束入射到厚度为1.8 μg/cm 2的碳膜上，测量了在0.0 ~ 2.0mrad范围内，每0.5mrad步长同时发射的二次电子数随离子出射角的统计分布.在入射光束的前向和后向分别进行了SE的测量。对于所有的测量角度，同时n电子发射每个弹丸，W n的概率，表现出大致的指数下降，增加n。然而，直到0.1mrad，随着出射角的增加，减小速率变小。另一方面，W n在较大角度处达到饱和。这种行为对于前向和后向SE发射是共同的。根据这种角度依赖性，在前向方向γ F和后向方向γ B，每个射弹的平均SE产额在1.0 mrad时比在0.0 mrad时增加高达约50%，并且在更大的角度处饱和。作为一个Monte Carlo模拟的结果，考虑到在一个质子与碳原子的单次碰撞中的碰撞参数依赖的能量损失，它被发现，计算的能量损失表现出非常相似的出射角依赖于测量的SE产率。
With 2.5-MeV proton beams incident on a carbon foil of 1.8 μg/cm 2 in thickness, the statistical distributions of the number of simultaneously emitted secondary electrons (SEs) have been measured as a function of the emergent angle of ions penetrating the foil in the range from 0.0 mrad to 2.0 mrad for every 0.5-mrad step. The measurement of SEs was carried out at the forward and backward directions of the incident beam separately. For all of the measured angles, the probability of simultaneous n electron emission per projectile, W n , exhibits roughly an exponential decrease with increasing n. Up to ∼ 1 mrad, however, the decreasing rate becomes smaller with an increase in the emergent angle. On the other hand, W n reaches saturation at larger angles. This behavior is common to the forward and backward SE emission. In terms of this angular dependence, the average SE yields per projectile at the forward direction, γ F , and at the backward direction, γ B , increase as high as about 50% at 1.0 mrad compared with corresponding ones at 0.0 mrad and saturate at larger angles. As a result of a Monte Carlo simulation taking account of the impact parameter dependent energy loss in a single collision of a proton with a carbon atom, it is found that the calculated energy losses exhibit a quite similar emergent angle dependence to that of the measured SE yields.