Upgrade of the SLAC SLED-II pulse compression system based on recent high power tests

In the Next Linear Collider (NLC) it is expected that the high power RF components be able to handle peak power levels in excess of 400 MW. We present recent results of high power tests designed to investigate the RF breakdown limits of the X-band pulse compression system used at SLAC. (SLED-II). Results of these tests show that both the TE/sub 01/-TE/sub 10/ mode converter and the 4-port hybrid have a maximum useful power limit of 220-250 MW. Based on these tests, modifications of these components have been undertaken to improve their peak field handling capability. Results of these modifications will be presented.