Response of Large Nb-Based Tunnel Junction to X-Rays
High quality Nb-based tunnel junctions with surface areas of 100×100μm<SUP>2</SUP> and 200×200μm<SUP>2</SUP> were tested by irradiating X-rays. According to the decrease in the disappearance of quasiparticles before tunneling, the 200×200μm<SUP>2</SUP> junction exhibited better X-ray response than that of 100×100μm<SUP>2</SUP> one. In the operation of the 200×200μm<SUP>2</SUP> junction, two kinds of stable operation modes with different pulse heights were found by applying a magnetic field with different ramping speeds. The higher pulse height mode was observed with a ramping-speed faster than about 200G/s. After tuning of the bias current in the higher mode operation, the energy required for single electron collection was obtained to be 6.5meV and the junction detected 5.9keV X-rays of <SUP>55</SUP>Mn with an energy resolution (FWHM) of 93eV. The 200×200μm<SUP>2</SUP> junction has the largest dimension among tunnel junctions exceeding silicon-semiconductor detectors in energy resolution.
- Journal of nuclear science and technology
Journal of nuclear science and technology 34(10), 979-982, 1997-10-25
Atomic Energy Society of Japan