Usually partial blockage is worse, because you end up with a spray of secondary particles instead of a single ray.

Maybe the secondaries could be blocked by different/lighter materials ? Basically a Whipple Shield for radiation. :)

Stopping power is basically correlated with mass.

Makes intuitive sense, thanks for the insight.

A second layer blockage for the secondary particles wouldn't have to be as dense or am I missing important physics?

(I guess a lot of gamma radiation would still reach this second layer so please ignore my question :)

Keep adding layers until you get to 1.3 feet of lead and it’ll work.

haha thanks for the correction - I was under the Turtles All the Way Down mindset :)

Isn't that more like how you make bombs than armors more effective - with backside spalling and secondary fragmentations?

can you block a hemisphere? the other 2pi steradians are shielded by the earth...

This may be true for high energy particles, but the majority of TID damage is done by higher flux lower energy, for which shielding is often viable!

The point is that shielding turns a single high energy particle that would otherwise strike and probably destroy a single transistor, into a veritable spray of lower energy particles causing bit flips or worse all over the circuit. This spray of particles can be stopped... with 1.3 feet of lead shielding.