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Measurement procedure for EAW. The measurement track is divided into 64 data segments. In each data segment, a single tone with a density of 300 kfci was recorded. A repeated second write (“write-2”) was performed in the window . The lower plot shows the observed signal as seen on a spectrum analyzer in zero span mode. In a second experiment, an additional recording was made in the time window after the single tone of 300 kfci and before write-2 was performed. This recording was made only once and is shown dashed.
Spectrum analyzer outputs for selected sectors before and after write-2 cycles (head 1).
(Color) Map of all 64 spectrum analyzer traces before (left) and after (right) write-2 passes. The dark strip between 15 and 20 μs corresponds to the time window where the write-2 was performed (head 1).
EAW activity in all 64 sectors after 1000 write-2 passes for different types for write-2: ac, positive and negative dc polarity for write-2 (head 2).
(Color) Evolution of the EAW activity in the presence of rumble strips. The rumble strips were placed at a cross-track position of half a track width to either side of the main track (head 3). The labels indicate how many write-2 processes that have been performed.
Illustration of the rumble strips used in our experiments at . The location of these “rumble strips” can be varied. The pattern shown is the most efficient rumble strip pattern as it is used in the servosector.
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