Electron beam apparatus and method for controlling electron beam apparatus

An electron beam apparatus that includes an electron gun configured to emit an electron beam and an electron gun chamber to which a sputter ion pump and a non-evaporable getter pump are connected, the electron beam apparatus comprising:

• a gas supply unit configured to supply at least one gas, wherein the gas is at least one of hydrogen, oxygen, carbon monoxide, and carbon dioxide to the electron gun chamber,
• wherein
• the gas supply unit includes a gas generation source configured to generate the at least one gas,
• the gas generation source is an alloy configured to occlude the at least one gas,
• the alloy is a same material as the non-evaporable getter pump, and
• a surface area of the alloy is smaller than a surface area of the non-evaporable getter pump.