The SPS 200 MHz TWC impedance after the LIU upgrade

As a part of the LHC Injectors Upgrade project (LIU) the 200 MHz Travelling Wave Cavities (TWC) of the Super Proton Synchrotron (SPS) will be upgraded. The two existing five-section cavities will be rearranged into four three-section cavities (using two existing spare sections), thereby increasing the total voltage from 7 MV (I$_{RF}$ = 1.5 A) to 10 MV (I$_{RF}$ = 3.0 A). Projections of the HL-LHC (High Luminosity Large Hadron Collider) era are conceived by the macro-particle simulation code BLonD, that makes use of an impedance model of the SPS, developed from a thorough survey of machine elements. This paper analyses the impedance contribution of the 200 MHz cavities in the two configurations, using electromagnetic simulations. Measurements of the existing cavities in the SPS and a single-section prototype are also presented.