Effects of ICRF induced density modifications on LH wave coupling at JET

Lower hybrid (LH) wave coupling is modified and usually degraded when the system is powered simultaneously with the ion cyclotron range of frequency (ICRF) antennas magnetically connected to the launcher. This has been attributed to scrape-off layer density modifications by the RF sheaths. LH reflection coefficients dependences on various parameters are investigated and shown to be consistent with RF sheath physics. Gas puffing near the launcher has been used to improve the coupling of LH waves