Abstract: Window constructions for use in particle accelerators to separate an evacuated accelerator beam chamber from a gas or liquid filled target area, which window structure enhances cooling of the foil covering the window opening and reduces stresses on the foil. For preferred embodiments, the window opening is shaped and dimensioned to provide high length-to-width aspect ratio and a rectangular shape with rounded corners. The openings should generally be as narrow as possible while still being wide enough to assure efficient transmission of the ion beam. Stresses in the foil is reduced by providing controlled bowing of the portions of the foil covering the window. This may be accomplished by providing some slack in the foil, at least in one dimension, but is preferably accomplished by pressing the foil between mating curved surfaces selectively extending from the edges of the window openings, resulting in the desired bow in the foil in the window area.

Abstract: A high energy, high voltage pulsed power source is provided which is capable of operating at high repetition rates while not having significantly high voltages appearing at any point in the circuit except on the output line. This eliminates the need for Freon cooling the source, permitting conventional water cooling and/or air cooling techniques to be utilized, and also permits air to be used as a dielectric in the source. These advantages are achieved by commutating the voltage across a charged capacitor, using a solid state SCR or other suitable switching device, passing the resultant signal through at least one compressor stage, which reduces the pulse duration and increases the pulse voltage, and applying the output from the compressor in parallel to a primary winding on each of a plurality of transformer coils having a single wire passing therethrough. The output on the wire is equal to the compressor output voltage multiplied by the number of cores.

Abstract: A high energy, charged particle accelerator, and radiation sources utilizing such accelerator are provided. More particularly, a high yield neutron generator and apparatus for the use of such generator are provided. The generator utilizes an ion source, a target adapted to generate neutrons when bombarded by high energy ions and an accelerator tube between the source and target. A multistage cascade rectifier is paraxial with the accelerator tube and has a voltage gradient which substantially matches that of the accelerator tube. The cascade rectifier preferably surrounds the accelerator tube and has equipotential metal plates on each side of each stage, the potential gradients between each pair of plates being substantially uniform and being substantially equal to the voltage gradient in the adjacent section of the accelerator tube. Generator elements may be enclosed in a pressure vessel and a moderator may be provided in the vessel, near the target to thermalize neutrons emitted from the target.

Abstract: This invention relates to a laser amplifier which achieves substantially enhanced gains by diverging the laser beam in a gain medium having a substantially rectangular shape. In particular, at least one laser beam is passed through a lens or other suitable means to cause it to diverge at a predetermined angle and the diverging beam or beams are caused to pass through the gain medium in a manner such that a beam makes only a single pass through any section of the medium, with the total number of passes through the medium by the beam(s) applied to the medium being an even number. The angle at which the beam diverges should be such as to maintain a near optimum laser power extraction efficiency for the beam. If a single beam is supplied to the medium, it makes an even number of passes through the medium with mirrors, prisms, or other suitable means being provided as the beam exits the medium after each pass except the last pass to fold the beam back into the medium for a subsequent pass.

Abstract: A high voltage multistage cascade rectifier power supply is provided which maintains uniform potential between the stages of the rectifier, and thus uniformly grades the electric potential, by providing equipotential conductor plates on each side of each stage of the power supply. The plates include both AC and DC plates, with capacitors being provided between each pair of plates defining a stage. Discrete capacitors may be provided between each pair of plates or the plates may form part of the capacitors with dielectric material being provided between the plates. The plates are selectively interconnected by diodes to form the cascade rectifier. Stray capacitance in the cascade rectifier is compensated for with an inductor across the input to the rectifier, which inductor is selected to tune out the stray capacitance. The frequency of the input drive may be automatically adjusted to compensate for changes in the system, including changes in stray capacitance.

Abstract: An improved method and apparatus for generating a pulsed RF power signal is provided. A DC pulse signal is generated which is compressed to increase its power to a predetermined level. The compressed pulse signal is applied to rapidly charge capacitive elements of a frozen wave generator. The capacitive elements may for example be lumped capacitors or transmission line segments. The charging step is accomplished in a manner such that the level and/or polarity of the charge for alternate stages are different than the level and/or polarity for the remaining stages. This may be accomplished by initially charging all stages to the same level and polarity and then either flipping the charge for alternate stages or otherwise altering the charge for such alternate stages or by initially charging alternate ones of the stages to a different level and/or polarity than the remaining stages.

Abstract: An energy substraction medical imaging system which is used for imaging a body part impregnated with a radio-opaque dye such as iodine is provided. The system includes an electron beam target having a target surface which, when excited by a high-energy electron beam, generates radiation having strong K.sub..alpha. at energy levels slightly above and slightly below the K-edge energy level of the dye. The target surface is preferably formed of a compound containing lanthanum, such as lanthanum oxide. The target may also be formed of a compound containing a material having a K.sub..alpha. line at an energy level slightly above the dye K-edge and a material with K.sub..alpha. line slightly below the dye K-edge or with separate sections containing such materials which are alternately excited. The target is excited by a high-energy electron beam from a suitable source, the electron beam having sufficient energy to provide a high photon yield at the K.sub..alpha.

Abstract: A high current (0.2 to at least 2 milliamperes), low-energy (2.2 to 4 MV) ion beam is generated and is utilized to produce clinically significant quantities of medical isotopes useful in applications such as positron emission tomography. For a preferred embodiment, a tandem accelerator is utilized. Negative ions generated by a high current negative-ion source are accelerated by an electrostatic accelerator in which the necessary high voltage is produced by a solid state power supply. The accelerated ions then enter a stripping cell which removes electrons from the ions, converting them into positive ions. The positive ions are then accelerated to a target which is preferably at ground potential.