CMA - SIMION

From SIMION

A cylindrical mirror analyzer (CMA) consists of two concentric cylindrical electrodes held at different potentials. Charged particles of only a certain kinetic energy, called the pass energy, can pass through the electrodes at constant radius, so the system acts as a narrow band KE filter. It is similar to an HDA.

In an idealized CMA, the the cylindrical electrodes are infinitely long (2D, planar symmetry in SIMION), having a simple analytic formula for potential V at radius r with inner and outer surface radii R1 and R2:

 V(r) = V(R1) + k ln(r / R1)

where

 k = (V(R2) - V(R1)) / ln(R2 / R1)

Here's a GEM file for a typical 2D CMA with R1 = 75 mm and R2 = 94 mm.

; cma2d.gem
pa_define(101,101,1,p,xy)
; outer electrode, R2
e(45.1570) { fill { notin  { circle(0,0,93) } } }
; inner electrode, R1
e(0)       { fill { within { circle(0,0,75) } } }

The radius in the "notin" command is one grid unit less than R2 for improved accuracy.

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Info: CMA

From SIMION

See also