We are planning on installing 7 large magnetic injection coils that can make large enough fields to show up broad-band in DARM. Previously we have been limited to comb injections; this was fine when the coupling was dominated by permanent magnets with simple power function coupling. But now we are dominated by coupling to cables and connectors and the coupling functions are not as simple, so we want to probe more of the spectrum with broad band injections.

We were happy with the prototype (https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=43406), so we are going ahead and planning the next locations. The figure shows the proposed locations, which include the preferred order of installation.