From Black Mesa: Wiki

A render of the Tau Cannon as it appears in Black Mesa.

Overview

The Tau Cannon is a prototype particle weapon built by scientists in the Black Mesa Research Facility. The Tau Cannon fires highly charged tau particles taken from Depleted Uranium. It is possible to store up to 100 units of DU but the reserve is shared with the Gluon Gun [1].

The player obtains this weapon in the chapter Questionable Ethics, right after a guard accidentally blows up a scientist and himself by letting it overcharge.

Primary Function

Fires a rapid barrage of minimum-charge tau particles at a cost of 2 uranium ammo per shot.

Secondary Function

Charges the tau cannon when held, letting the cannon do more damage per shot at a cost of more ammo. Can also be used to fire a shot using only 1 uranium charge, but at a lower rate of fire than the primary fire.

WARNING: Do not let the Tau Cannon overcharge! When ammunition stops being depleted by the cannon, you only have a short amount of time to fire the shot before the cannon overcharges, damaging and potentially killing you.

Media

The Tau Cannon model.

An in-game screenshot of the Tau Cannon.

Trivia

• The Tau Cannon is also commonly referred to alternatively as the "Gauss Gun". This is because of the original use of the weapon; When Valve turned it into an experimental energy weapon partway through development, they neglected to change the name in the code.