X-Ray Detection Using Superconducting Tunnel Junction Shaped Normal-Distribution-Function

Tohru TAINO  Tomohiro NISHIHARA  Koichi HOSHINO  Hiroaki MYOREN  Hiromi SATO  Hirohiko M. SHIMIZU  Susumu TAKADA  

IEICE TRANSACTIONS on Electronics   Vol.E90-C   No.3   pp.566-569
Publication Date: 2007/03/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e90-c.3.566
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Innovative Superconducting Devices and Their Applications)
superconducting tunnel junction,  normal-distribution-function shape,  the dispersion parameters σ,  X-ray detector,  

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A normal-distribution-function-shaped superconducting tunnel junction (NDF-STJ) which consists of Nb/Al-AlOx/Al/Nb has been fabricated as an X-ray detector. Current - voltage characteristics were measured at 0.4 K using three kinds of STJs, which have the dispersion parameters σ of 0.25, 0.45 and 0.75. These STJs showed very low subgap leakage current of about 5 nA. By irradiating with 5.9 keV X-rays, we obtained the spectrum of these NDF-STJs. They showed good energy resolution with small magnetic fields of below 3 mT, which is about one-tenth of those for conventional-shaped STJs.