Attenuation length
（重定向自Absorption length）
In physics, the attenuation length or absorption length is the distance ![\lambda](/Images/godic/202412/19/e05a30d96800384dd38b22851322a6b54756.png")
into a material when the probability has dropped to ![1/e](/Images/godic/202412/19/77ba8b5890d6b78574f77b26713dbc1b4756.png")
that a particle has not been absorbed. Alternatively, if there is a beam of particles incident on the material, the attenuation length is the distance where the intensity of the beam has dropped to , or about 63% of the particles have been stopped.