Speaker
Mr
amiya mitra
(TRIUMF)
Description
A new intermediate power amplifier (IPA) is currently being designed to improve the reliability of the main rf system of the 500 MeV Cyclotron at TRIUMF. A four-way matching pi-network circuit divides the power output from the present 100 KW IPA which drives four power amplifiers to produce 1 MW of rf power. Poor isolation between the four outputs makes it difficult to tune the power amplifiers. This deficiency can be overcome by using four independent 25 KW IPA. This paper describes design of such a 23 MHz 25 KW CW amplifier using EIMAC 4CW25000A tetrode. EIMAC tube performance computer has been used to establish the dc and rf parameters of the amplifier. As an alternate to the EIMAC performance calculation, accurate model in SPICE was investigated. The advantage of the SPICE model is that the circuit elements and inputs can be modified easily and the results can be seen in the simulation almost immediately. SPICE Subcircuit Architecture was developed to model the tube’s constant current curves. The results from PSPICE and EIMAC tube performance are presented. The output cavity of the amplifier is 23 MHz quarter wave resonator. Ansoft HFSS has been used to simulate the output cavity and compute shunt impedance and Q of the cavity and also design the coupling loop and the tuning elements for frequency tuning. Solid Works and HFSS helped to optimize both mechanical and electromagnetic design of the output cavity. Input circuit and neutralization of the amplifier are also discussed here. Prototype design of output cavity provides three alternative frequency tuning elements: movable shorting plate, vacuum variable capacitor and passive rotating tuning loop. Final option for output cavity frequency tuning will be defined after the tests. HFSS has also being used to compute parasitic modes of the amplifier.
Author
Mr
amiya mitra
(TRIUMF)
Co-authors
Mr
I Naidu
(UVIC)
Mr
Joseph Lu
(TRIUMF)
Mr
M Battig
(University of Waterloo)
Mr
Richard Shanks
(TRIUMF)
Mr
S Gillan
(UVIC)
Mr
V Peplov
(INR, MOscow)
Mr
Vladimir Zvyagintsev
(TRIUMF)
Mr
Yuri Bylinskii
(TRIUMF)
Mr
Zlatko Bjelic
(TRIUMF)
