High-field synchrocyclotron

  • US 7,696,847 B2
  • Filed: 04/17/2009
  • Issued: 04/13/2010
  • Est. Priority Date: 01/19/2006
  • Status: Active Grant
First Claim
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1. A synchrocyclotron magnet structure including a magnetic yoke comprising a pair of poles that define an acceleration chamber including a median acceleration plane and a central axis orthogonal to the median acceleration plane,wherein the magnetic yoke defines passages about the acceleration chamber and on opposite sides of the median acceleration plane for mounting a pair of magnetic coils,wherein the poles are joined at a perimeter and separated to form a pole gap of at least 3.8 cm across and throughout the acceleration chamber,wherein each pole has an inner surface that is tapered to produce a perimeter pole wing distal from the central axis and proximate the passages for the coils, a central pole tip proximate the central axis and distal from the passages for the coils, and a peak pole gap at an intermediate distance between the central pole tips and the perimeter pole wings, the peak pole gap being at least triple the pole gap between the central pole tips and at least triple the pole gap between the perimeter pole wings at all radial angles about the central axis, andwherein the poles are tapered to shape a combined magnetic field jointly produced by the magnetic yoke and by magnetic coils in the passages so that, when the magnetic coils directly generate a central magnetic field in the median acceleration plane of at least 5 Tesla and fully magnetize the magnetic yoke, the combined magnetic field across the median acceleration plane decreases with increasing radius and a weak-focusing field index parameter, n, is in the range from 0 to 1 from the central pole tips to the perimeter pole wings, where n=−

  • (r/B)(dB/dr), and where B is the magnetic field, and r is the radius from the central axis.

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