Construction of a low-temperature gun and high-resolution field emission spectra from a Nb superconductor

Abstract To investigate the fine structures in high-resolution field electron emission (FE) spectra from superconductors, we have constructed new apparatuses including a low-temperature FE gun, which can be operated at about 2.2 K. The FE patterns have been observed with an optical-fiber measuring system and the electrons emitted in the direction of the tip axis are analyzed with the resolution of ∼1 meV. By using this experimental apparatus, we have observed a sharp peak at the Fermi level in FE spectra from a niobium superconducting emitter.