To add just a little to that explanation.
As the piston rises on the compression stroke, all the air in the cylinder is squeezed, just like in a gas engine--except that the piston comes all the way to the top of the cylinder forcing all the air into the precombustion chamber. It goes in thru small, calibrated orifices which promote great turbulence or swirl to the air. Thus, when the fuel is sprayed into the this hot, turbulent ball of air, it mixes very thoroughly and begins to burn. As it burns, the increasing pressure forces it back out into the cylinder area where the combustion process continues until all the available air is used forcing the piston down with great force.
Understanding that all the air has to go into, and then, out of the pre-chamber casues me to doubt that the efficiency of a diesel can be significantly raised by typical gas engine speed tricks--like porting, and polishing. They may help---some. But the limiting factor is the size of the holes into the pre chamber. I do not recommend enlargiung them, as they are specifically designed for the difficult task they accomplish. Changing them would affect the swirl and probably reduce the overall efficiency of the design.