Alpha particle trajectories from Li disintegration

[HarryTick]

When a proton is fused with lithium and two alpha particles are formed, how do you know which direction they'll go. I thought they would take roughly the same path as the accelerated proton, but in the explanations of Cockroft and Walton's setup, they show the lithium at a 45 degree angle and the scintillation detector off to the side. http://nobelprize.org/nobel_prizes/physics/laureates/1951/cockcroft-lecture.pdf" If a piece of lithium foil was placed perpendicular to the proton stream, would the alpha particle trajectories be different?

Please bear with me, I am an environmental chemist, not a physicist.

Edit: I can't believe I posted this in the wrong subforum. I meant to post this in the high energy physics section. Can a mod please move this?

 

[Astronuc]

The alignment of the Li target is simply for observing the scintillation while keeping the instrumentation out of the beam, and in this case the axis of the detectors is perpendicular to the beam. The total number of reactions would be a function of the thickness and to some extent the orientation of the target.

 

[HarryTick]

Is there a mod that can move this to the appropriate forum, or should I just edit my post to nothingness and post it in the proper forum?