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Overall view of the LOX impeller (aka "Impeller, Oxidizer," part number 459742).

The LOX turbopump is at the top of the turbopump assembly, and the impeller is immediately aft of the inducer.

One of our hosts told me that the bevelled edge above the impeller vanes is where material was removed from the impeller to balance it.

The LOX impeller is a shrouded impeller (the vanes of the impeller are covered, rather than being open). The oxidizer enters via the inlet at the top of the impeller and is accelerated to a high speed via the impeller's slinger vanes.

It seems counter-intuitive to me (I'm not really a rocket scientist; I just play one on TV): The fluid is not "cupped" by the concave side of the vanes, but rather "flung off" the convex side of the vanes.