A FET based kicker for a charge booster for the TRIUMF ISAC project

Abstract

Summary form only given, as follows. A charge booster unit is required for part of an upgrade to the ISAC facility at TRIUMF. ISAC is an isotope separator coupled to an accelerator. ISAC is presently capable of accelerating only isotopes with atomic mass up to 30. The charge booster will allow ISAC to accelerate all the masses in the periodic table. A fast kicker system is required to study the characteristics of an existing charge booster, designed by ISN in Grenoble, to assess the suitability of using this charge booster at TRIUMF. This fast kicker will subsequently be used in the TRIUMF ISAC facility for time of flight separation of the chosen charge and to recycle the higher and lower charges back to the charge booster, which will increase the efficiency from 10% to 60%. The kicker system includes a pair of deflector plates. One plate is charged up to -4 kV by a FET based modulator, while the other plate is held at ground potential. The modulator consists of two stacks of FETs operating in push pull with variable output voltage, pulse width, and repetition rate from virtually DC to greater than 50 kHz. The specifications for the kicker call for rise and fall times of less than 100 ns and a minimum pulse width of 500 ns. The maximum pulse width is dependent upon the repetition rate. The large dynamic range for the repetition rate and pulse width require a novel circuit design and control technique, which also results in a relatively energy efficient kicker system. This paper describes the design of the kicker system and shows the results of measurements.