Linear beam raster magnet driver based on H-bridge technique
An improved raster magnet driver for a linear particle beam is based on an H-bridge technique. Four branches of power HEXFETs form a two-by-two switch. Switching the HEXFETs in a predetermined order and at the right frequency produces a triangular current waveform. An H-bridge controller controls switching sequence and timing. The magnetic field of the coil follows the shape of the waveform and thus steers the beam using a triangular rather than a sinusoidal waveform. The system produces a raster pattern having a highly uniform raster density distribution, eliminates target heating from non-uniform raster density distributions, and produces higher levels of beam current.
1. A system for producing a highly homogenous raster density distribution having at least 98% linearity and at least 95% uniformity at a high energy level of at least 100 A of linear current swing at 25 kHz comprising:
an H-bridge circuit including a center portion and four ends;
four branches of power HEXFETs forming a two by two switch;
a raster air-core magnet at said center portion;
a high voltage power supply connected at two of said four ends;
an H-bridge controller connected to said HEXFETs;
electrical pathways connecting said HEXFETs, said raster air-core magnet, said high voltage supply, and said H-bridge controller; and
said H-bridge controller capable of switching said HEXFETs in an order and at a frequency to produce a triangular current waveform having a constant linear sweep velocity and a minimum turning time at the waveform peak.
2. The system of claim 1 wherein said constant linear sweep velocity is 1000 m/s.
3. The system of claim 2 wherein said minimum turning time at the waveform peak is 50 ns.