What would happen if one were to fire electrons at a solid mass of alpha particles?
How would you propose to construct a solid mass of alpha particles?
Well, alpha particles are the nuclei of normal helium atoms, so under reasonable conditions if an electron is fired at alpha particles you're going to get some helium gas.
Though as speedybob said, you can't have a solid mass of alpha particles, or helium, without extraordinary conditions, if ever.
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