A NEW HIGH POWER 201.25 MHZ RF SYSTEM FOR THE LANSCE 

Abstract

A newly designed and constructed testing facility has been established at Peters A.O. Broadcasting Company Ltd in Ado-Ekiti Ng, specifically for the evaluation of an Eimac 4CX15000A tetrode final power amplifier. The anode power specifications for the 4CX15000A require 29 kV DC, with 160 A delivered in millisecond pulses, facilitated by a 225 uF capacitor bank equipped with a crowbar circuit to swiftly discharge 88 kJ of stored energy. The charging current was sourced by reconfiguring a 2 MW beam power supply that was previously utilised in another project. The power tubes operate under DC anode voltage, while beam pulsing is achieved through control grid bias switching at relatively low power levels. Additionally, a new Fast Protect and Monitor System has been developed to sample RF reflected power, anode high voltage, and various tube currents, providing logic outputs to quickly eliminate high voltages, RF drive, and beam pulsing during fault conditions. The complete test system is managed by a programmable logic controller via an operator graphical user interface, ensuring proper startup sequencing and safeguarding against cooling loss. We have employed this test facility over the past year to assess the amplifiers alongside high-power coaxial components, including hybrid couplers and various water loads.

Keywords: Power, anode, beam, facility, voltage, pulsing, system