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.
Design for a FET based 1 MHz, 10 kV pulse generator
A pulse generator consisting of a coaxial cable and a high voltage modulator, incorporating two stacks of field-effect transistor (FET) switches operating in "push-pull" mode, has been designed and built. The modulator generates a continuous, unipolar, pulse train at a fundamental frequency of 1 MHz and a magnitude of 10 kV. The rise and fall times of the pulses are less than 39 ns. The two stacks each utilize 14 FETS, which are individually rated at 1 kV. The design incorporates a low-loss coaxial cable on which pulses are stored. Extensive PSpice simulations have been carried out to evaluate various design options. Subsequent measurements on the prototype pulse generator confirm the PSpice predictions.
Initial operating experience with the auxiliary accelerating cavity for the TRIUMF cyclotron
A 92-MHz auxiliary accelerating cavity has been installed in the TRIUMF cyclotron. The cavity operates at the fourth harmonic of the main RF frequency with a planned peak voltage of 150 kV. At full power it will almost double the present energy gain per turn in the 400-500 MeV range, reducing by 25% the stripping loss of the H/sup -/ beam. Low-current beam tests have been conducted at voltages of up to 90 kV and a maximum voltage of 145 kV has been attained. The cavity has also been used to flattop the integrated energy gain per turn. A description of the cavity design and a summary of the operating experience are given.<<ETX>>