Quadrupole Deflector

An electrostatic quadrupole beam deflector (or DC turning quadrupole/quadrupole bender) uses a DC quadrupole electric field to bend a charged particle beam 90 degrees. The bending can be switched on and off by setting the voltages (+V and -V on opposite rods for 90 degree bending and GND on all rods for no bending). A ground enclosure is placed around the rods to reduce bending outside of the 90 degree quadrant due to fringe fields.

The SIMION Example: bender_cut (turning_quad_xy.gem) included an example geometry in SIMION. This example was updated in SIMION 8.1.2.20 to include the outer enclosure electrode around the rods for proper operation (reduce field outside). This uses circular rods to approximate the quadrupole field (hyperbolic potential lines), much like in SIMION Example: quad, and the ratio between rod radius and half-distance between rods remains the same.

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Fig. 46 SIMION simulation of particles through 90 degree DC quadrupole deflector (based on SIMION Example: bender_cut (turning_quad_xy.gem)

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Fig. 47 3D view of turning_quad_xy.gem example, which includes entrance and exit lenses.