Detecting the failure of LED
The "12 V LED" is likely an LED in series with a resistor. You'll need to get access to the intermediate node between the LED and the resistor. Or else get rid of your "12 V LED" and use a separate LED and resistor of your choosing.

Now, what you'll do is apply voltage to the LED-resistor combo first. And monitor the voltage at the intermediate node with a couple of comparators. If that voltage is less than maybe 1 V, it means the LED has failed short. If the voltage is greater than 2 or 3 V (depending on the LED color) it means the LED has failed open. Two comparators can check these two conditions. If you use open-drain output comparators, you can make a wired-AND connection at their outputs, and connect this to your control circuit. Only if both comparators give the expected output, you turn on your ray gun.







simulate this circuit &ndash; Schematic created using CircuitLab

The common name for this circuit is a window comparator.

None of this will work if the failure mode of the LED is, for example, somebody spilled paint on it.