Effects of quasiparticle recombination and photoelectron escape in Al-superconducting tunnel junction detectors

A slight deviation from linearity has been detected for single aluminum sup erconducting tunnel junction detectors (100 x 100 x 0.52/0.35 mum(3)) in th e energy range between E = 1.74 keV and E = 6.49 keV, The nonlinearity can be explained by the escape of recombination phonons into the substrate, Var ying the size of the junction shows that the recombination of the quasipart icles takes place after their diffusive propagation across the junction, ho t spot effects m e not observed Energy resolution obtained with aluminum tu nnel junction detectors so far is not affected by recombination effects, Pu lse shape analysis allows to deconvolve the double-peak structure of the pu lse height spectra and to identify background events that are caused by the range of photo- and Auger -electrons. The range of photoelectrons (E-kin = 4.34 keV) is determined to be 0.2 mum in aluminum. In the pulse height spe ctrum, the escape of photoelectrons produces a flat background.