Yes, LINACS is a Scrabble word!

Letter values in Scrabble US: L 1, I 1, N 1, A 1, C 3, S 1.

Is it a valid word?

LINACS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

ions are accelerated along a linear path by voltage differences on electrodes along the path

Also: linear accelerator.