A Linear Accelerator for Simulated Micrometeors

Theory, design parameters, and construction details are presented for a linac which accelerates charged microparticles in the 1–10 μ diam range to meteoric velocities. The linac is of the Sloan-Lawrence (low-frequency, ac driven) type and contains 92 accelerating gaps with 100 kV accelerating potential applied at each gap. Particles are injected into the linac after preacceleration by a 1.6 MV modified Van de Graaff, giving a total accelerating potential of 10.8 MV for the system. In a significant departure from conventional accelerator practice, the linac is adapted to single particle operation by employing a square wave driving voltage with the frequency automatically adjusted from 12.5 to 125 kHz according to the variable velocity of each injected particle. Radial focusing is entirely second-order and is adequate to contain the particle ``beam'' within 1.8 cm diam. Compared to the Van de Graaff alone, the linac provides a particle mass increase of about 300 times for a given velocity, or a velocity increase of about 2.5 times for a given mass.