It's fine for what it is. But I think a particle detector that most people imagine is really something you want to be able to hold portably in the air and detect ambient/impinging radiation from unknown sources, rather than have to put samples in a closed container.
If there were some modification that made that possible (getting around the light-tight requirement), that would make this incredibly more useful.
this is possible! you can use a thin foil made from e.g. mylar, for example taken from a cracked-open old large foil capacitor and superglue one layer on the rim of the diode's metal case. It can then point through a hole into the outside of the tin box if not held into direct sunlight (some additional foam ring can be used to help block more light). Using one of the sturdy aluminum die-cast cases I've listed in the schematic should be favored in a mobile scenario. Much less affected by vibrations/microphonic effect.
It's fine for what it is. But I think a particle detector that most people imagine is really something you want to be able to hold portably in the air and detect ambient/impinging radiation from unknown sources, rather than have to put samples in a closed container.
If there were some modification that made that possible (getting around the light-tight requirement), that would make this incredibly more useful.