Electron beam penetration

With the same electron beam welder as described in the report 1, rectangular pulse beams of various duration time were incidented on pure aluminum, aluminum alloy, copper, brass and mild steel under the nearly same other welding conditions and growing process of cavity or penetration depth was observed. The results are summerized as follows; 1 In all metals used, there is a cavity formed rapidly. This penetration speed depends largely upon energy density of electron beam. Whereas shape of the cavity in a pure metal corresponds to higher portion of electron beam energy distribution, that in its alloy corresponds to lower 4 Until a certain short welding time, weld penetration depth in rest metal is the same as that in moving metal. This is resulted from the fact that the diameter ofelectron beam is not infinitesimal and penetration speed of welding is much higher than welding speed so that all specimens are apparently rest until at that time. Journal of the Japanese Welding Society.

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The penetration, scattering, and absorption of electron beams of energy 10 to 20 MeV in water has been mathematically investigated by solving the Lewis equation by the moment method under the continuous slowing-down approximation. Two beam geometries were considered: plane infinite monodirectional beam and point monodirectional beam, both incident on an infinite water medium. For the former, expressions were obtained for the flux, current, rate of energy deposition, rate of charge accumulation, and angular distribution as a function of depth, taking into account not only the incoming primary electrons, but also the contribution of the secondaries. For the latter geometry, expressions were obtained for the root-mean-square average of the flux and energy deposition as a function of depth.

Provisional Patent Application No. More particularly, the present invention relates to linear, straight through electron beam machines that incorporate a feedback strategy that allows the electron beam to be generated with controlled and adjustable penetration depth for therapeutic radiation applications. Even therapeutic radiation used to treat lesions on the skin surface still can penetrate several centimeters below the surface. To allow unaffected normal tissue to recover, the therapeutic radiation is generally delivered in many daily treatments, called fractions. Such fractional treatments rely on the principle that well- oxygenated normal tissues will repair and recover from radiation damage more quickly than the tissues being targeted by the therapeutic radiation.