An electron gun 901 capable of suppressing an uneven temperature distribution at an extraction electrode and a length-measuring SEM 900 are provided. The electron gun 901 is equipped with: a charged particle source 1; an extraction electrode 3 for extracting charged particles from the charged particle source 1 and allowing some of the charged particles to pass while blocking some other charged particles; and an auxiliary structure 5 disposed in contact with the extraction electrode 3. The length-measuring SEM 900 is equipped with the electron gun 901 and a computer system 920 for controlling the electron gun 901.

An electron gun 901 capable of suppressing an uneven temperature distribution at an extraction electrode and a length-measuring SEM 900 are provided. The electron gun 901 is equipped with: a charged particle source 1; an extraction electrode 3 for extracting charged particles from the charged particle source 1 and allowing some of the charged particles to pass while blocking some other charged particles; and an auxiliary structure 5 disposed in contact with the extraction electrode 3. The length-measuring SEM 900 is equipped with the electron gun 901 and a computer system 920 for controlling the electron gun 901.

An electron beam adjustment method includes measuring a current density distribution of an electron beam to reach a target object, calculating a feature amount of a measured current density distribution, and increasing, in the case of the feature amount being outside the range of a threshold, a temperature of an electron beam emission source.

An electron beam adjustment method includes measuring a current density distribution of an electron beam to reach a target object, calculating a feature amount of a measured current density distribution, and increasing, in the case of the feature amount being outside the range of a threshold, a temperature of an electron beam emission source.

Provided are a structure for particle acceleration and a charged particle beam apparatus, which enable the suppression of electric field concentration occurring near a negative electrode part. The structure for particle acceleration includes: a ceramic body 1 having a through hole 10 formed by an inner wall surface; and a negative electrode 2 and a positive electrode 3 which are arranged, respectively, on one end and the other end of the through hole 10 in the ceramic body. The inner wall surface of the ceramic body 1 is configured such that a first region 22, which is electrically connected with the negative electrode 2, and a second region 23, which is electrically connected with the positive electrode 3, are electrically connected to each other. The surface resistivity of the first region 22 is lower than the surface resistivity of the second region 23.

Provided are a structure for particle acceleration and a charged particle beam apparatus, which enable the suppression of electric field concentration occurring near a negative electrode part. The structure for particle acceleration includes: a ceramic body 1 having a through hole 10 formed by an inner wall surface; and a negative electrode 2 and a positive electrode 3 which are arranged, respectively, on one end and the other end of the through hole 10 in the ceramic body. The inner wall surface of the ceramic body 1 is configured such that a first region 22, which is electrically connected with the negative electrode 2, and a second region 23, which is electrically connected with the positive electrode 3, are electrically connected to each other. The surface resistivity of the first region 22 is lower than the surface resistivity of the second region 23.