I think it would be possible with a plasma FIB. They use xenon instead of gallium and are 50 times faster than typical Ga-FIBs. A Tescan Fera microscope is equipped with a plasma FIB, for example. Another method would be pulsed laser material removal inside a Zeiss Auriga Laser microscope. It is even faster than the Xe-FIB, but also rougher.

A third and much cheaper method would be to embed the tube and to grind and polish it until the middle is exposed, but I am not an expert in this embedding stuff.. Then you could use a simple SEM for imaging.

Thank you for the solutions!