Computational and Experimental Studies on Dark Current and Field Emission in βg = 0.92, 650 MHz Elliptic SRF Cavities in a Vertical Test Stand (VTS)

This article presents a novel methodology to estimate dark current in the superconducting cavity as a function of acceleration gradient during its qualification in a vertical test stand (VTS). The estimation is done by comparing the measured radiation dose during the cold test in a VTS with results from radiation transport simulations using
FLUKA
, where a particle tracking code developed in-house provides the required input for
FLUKA
simulations. By employing this methodology, estimation of dark current from a 650-MHz, 5-cell,
$\beta _{g} = 0.92$
elliptic superconducting radio-frequency (SRF) cavities has been done for different acceleration gradients and the estimates agree very well with the predictions from an analytical formula for dark current based on a field emission model using Fowler–Nordheim equation.