Using a pulsed deflector for extraction of pulsed beams from the TRIUMF cyclotron
In the normal mode of operation, the TRIUMF cyclotron accelerates H/sup -/ ions to produce 500 MeV proton beams of 160 /spl mu/A with 4 nsec pulses separated by 43 nsec. A proposed experiment (/spl mu//spl rarr/e conversion) requires a 500 MeV beam with 100-200 nsec pulses separated by 1-2 /spl mu/ sec with an average intensity of 200 /spl mu/A. Two methods have been investigated to achieve this time structure. Both incorporate a pulsed electric deflector and take advantage of extraction by stripping. In the first case, a deflector with a thin septum deflects radially up to six accumulated turns onto a stripping foil in one turn. In the second, a pair of vertically deflecting plates are pulsed at a frequency to excite a coherent vertical growth, and the particles are eventually intercepted by a stripping foil. Under certain conditions extraction occurs in almost perfect synchronism with the driving pulse. Both methods will be described in detail and results of computer simulations will be presented.
Measurements on a FET based 1 MHz, 10 kV pulse generator
A prototype pulser, which incorporates thirty-two 1 kV field-effect transistor (FET) modules, has been built and tested at TRIUMF. The pulser has been developed for application in a scheme for pulsed extraction from the TRIUMF 500 MeV cyclotron. Deflection of the beam will be provided by an electric field between a set of 1 m long deflector plates. The pulser generates a continuous, unipolar, pulse train at a fundamental frequency of approximately 1 MHz and a magnitude of 10 kV. The pulses have 38 ns rise and fall times and are stored on a low-loss coaxial cable which interconnects the pulse generator and the deflector plates. The circuit performance was evaluated with the aid of PSpice in the design stage and confirmed by measurements on the prototype. Temperature measurements have been performed on 1 kV FET modules under DC conditions and compared with temperatures under operating conditions to ensure that switching losses are acceptable. Results of various measurements are presented and compared with simulations.
Prototype studies of a 1 MHz chopper for the kaon factory
The 1.025-MHz beam chopper will create 108-ns gaps in the 1GeV/c H/sup -/ beam to allow enough time for the magnetic field to be established in the kicker magnets in each of the 5 accumulator rings of the kaon factory at the Tri-University Meson Facility (TRIUMF). The required deflection of 1 mrad can be achieved with a set of plates 5-cm apart in which the product of voltage difference and plate length is 37.7 kV-m. The kick must have a rise and fall time of less than 39ns and a flat top of 49ns, and 92ns on alternate pulses. The 1-MHz chopper concept involves an energy storage system where the electric pulses are stored in a large-diameter low-loss coaxial cable. Measurements of the performance of a high-voltage prototype are presented. Results show that this novel design can be implemented successfully for the kaon factory.<<ETX>>