[GEC]

I don't get it. How does aiming a powerful beam of radiation at the spaceship minimize the exposure of the astronauts to radiation? I'm assuming that the radiation from the sun is widespread and unpredictable due to solar flares. The spaceship designs I have read about would place water tanks and batteries around the outside the ship to minimize the exposure to the solar radiation. The beam that drives the sail would be tight enough that the ship's sail could ride along it without any of the radiation hitting the actual ship.

[Physicist]

The beam that drives the sail would be tight enough that the ship's sail could ride along it without any of the radiation hitting the actual ship.

I don't think that's realistic.