Oximetría de pulso fetal y parto por cesárea

An electron beam apparatus for irradiating a target with an electron beam includes a reference sample including at least one reference pattern which has a plurality of lattice structures arranged along the circumference of a circle in a evaluation surface of the reference sample; and an adjustment section for adjusting the electron beam by irradiating the evaluation surface with the electron beam on the basis of electrons generated from the reference sample.