Design and analysis of TWIN source extraction system grids with indigenous manufacturing feasibility assessment

A 3 grid extractor and accelerator system is to be coupled to the two driver RF negative ion source test bed to extract and accelerate H- ion beams up to 50 keV. One of the aims of the TWIN test bed is to characterize and benchmark the optics design of such an accelerator system (1:4 scale) which has been modelled for the 8 driver diagnostic neutral beam negative ion source. A cooling scheme based on analysis and indigenous manufacturing assessment has been selected. In order to enable indigenous manufacturing of embedded cooling channel of such an accelerator a route of vacuum brazing has been considered to close the water cooling channels of the 3 grid segments as against the conventional route of 1 mm thick electrodeposited layer of copper. It will be an attempt to replace copper electro-deposition which has limited availability across the globe. The optimal geometrical requirements for establishing brazing to close the water cooling channels has been successfully realized and validated experimentally by subjecting the developed prototype braze coupon under high heat flux facility at IPR. The selected cooling scheme choice has then been utilized on a strip model (Grid segment) to perform thermo-mechanical analysis under operating load conditions to study thermal profile, stresses, out of plane deformations and aperture displacements (misalignment).