The miniature transmission X‐ray tube is widely used in energy dispersive X‐ray Fluorescence Analysis (EDXRFA) . The miniature transmission X‐ray tube with a small ,low power consumption ,X‐ray emission efficiency that can be made the ex‐citation source of handheld X‐ray energy dispersive fluorescence analyzer .Beryllium (Be) is the most commonly used X‐ray win‐dow material .But beryllium is expensive and toxic .At the same time set filtering window by aluminum (Al) to reducing low‐en‐ergy scattering rays .This paper be adopted Al for exit window material of miniature transmission X‐ray tube ,achieve high‐ener‐gy rays transmission and low‐energy scattered radiation shielding ,at the same time reduce production cost and difficulty .The present paper simulate the X‐ray tube output spectrum of silver (Ag) target and aluminum window with different thickness by MCNP5 .We consider the X‐ray of low energy part is completely shielded when aluminum windows thickness is greater than 1.5 mm .We can conclude that 2 μm and 0.8 mm are the best combination of target thickness and aluminum windows through com‐parative analysis of existing research results .Then we can get flux of high energy part is big and low energy part is small when the target is 2 μm thick Ag and the window is 0.8 mm thick Al .%微型透射式X射线管广泛应用于能量色散X射线荧光分析领域，具有体积小、功耗低、X射线发射效率高等特点，可作为手持式X射线荧光分析仪器的激发源。目前常用铍（B e ）作为出射窗材料，成本高，而且有毒性。同时为减少低能散射射线，在射线管前端放置铝（Al）作为过滤窗。本文拟采用Al为微型透射式X射线管出射窗材料，透射高能射线，屏蔽低能散射射线，降低制作成本和难度。文中采用蒙特卡洛模拟软件MCNP5模拟计算不同银（Ag）靶厚度和Al窗厚度的X射线管输出谱。结果表明，Al窗对低能射线的屏蔽作用强于对高能射线的屏蔽作用，在Al窗厚度超过1.5 mm时，低能射线完全被屏蔽，高能射线有部分透射。通过和已有研究成果[1，5]对比分析，在Ag靶厚度为2μm ，Al窗厚度为0.8 mm时，低能射线所占的比例仅为0.0878％，高能射线产生率为0.00273％，既能有效屏蔽低能射线，又能保证高能射线较高的出射率，能够满足野外现场能量色散 X射线荧光分析的需要。
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