Neutron source for neutron capture therapy

1. A Boron neutron cancer treatment system, comprising:

a moderator chamber filled with liquid or granular moderator material except for a central treatment chamber, the moderator chamber having parallel upper and lower surfaces;

a plurality of neutron generators, each comprising a pre-moderator block of moderating material having an upper surface, a lower surface, a first and a second end, opposite side surfaces, a first length, a first width less than the first length, and a first thickness, a cylindrical acceleration chamber having a first diameter the first width of the pre-moderator block, sealed at one end to the upper surface of the pre-moderator block adjacent the first end of the pre-moderator block, with a vertical axis perpendicular to the upper surface, the acceleration chamber having a height and a top cover at a second end away from the pre-moderator block, a vacuum pump engaging the acceleration chamber, evacuating the acceleration chamber to a high vacuum, a plasma ion chamber opening into the acceleration chamber through an ion extraction iris through the top cover of the acceleration chamber on the vertical axis of the acceleration chamber, a gas source providing deuterium gas to the plasma ion chamber, a microwave energy source ionizing the gas in the plasma ion chamber, a cylindrical primary isolation well extending a distance into the pre-moderator block from the upper surface, centered on the vertical axis of the acceleration chamber, a secondary isolation well in a shape of a hollow cylinder surrounding the primary isolation well, to a depth somewhat less than the distance of the primary isolation well, within the first diameter of the acceleration chamber, a water-cooled titanium target disk having a target surface orthogonal to the axis of the acceleration chamber, the target disk having a diameter smaller then a diameter of the isolation well, positioned at a lower extremity of the isolation well, the target disk biased to a negative DC voltage, and electrically grounded metal cladding covering all otherwise exposed surfaces of the pre-moderator block; and mechanical adjustable carriers for the neutron generators, each carrier supporting one neutron generator, and enabled to translate the neutron generator toward and away from the central treatment chamber, and to rotate the neutron generators in a plane parallel to a plane of the parallel upper and lower surfaces of the moderator chamber;

wherein the modular generators and the mechanical adjustable carriers are fully immersed in the liquid or granular moderator material of the moderator chamber.