The back iron is removably attached to the second end of the tooth body and adjacent stator segments are spaced by interfaced adjacent back iron.

The adapter is non-removably coupled to the fill valve and is configured with a larger proximal pathway, and a smaller distal metering pathway for restricting the refill flow rate.

The system has an interface (116) in a wall of the chamber for removably accommodating the first holder (112) or a second holder (118) with a second specimen (120) mounted thereon.