Superconducting Tunnel Junction Array Development for High-Resolution Energy-Dispersive X-ray Spectroscopy

Cryogenic energy-dispersive X-ray detectors are being developed because of their superior energy resolution (10 eV FWHM for keV X-rays) compared to that achieved in semiconductor energy-dispersive spectrometry (EDS) systems. So far, their range of application is limited because of their comparably small size and low count rate. We present data on the development of superconducting tunnel junction (STJ) detector arrays to address both of these issues. A single STJ detector has a resolution of around 10 eV below 1 keV and can be operated at count rates of the order 10,000 counts/sec. We show that the simultaneous operation of several STJ detectors does not dimish their energy resolution significantly, and it increases the detector area and the maximum count rate by a factor given by the total number of independent channels.

Cryogenic high-resolution X-ray spectrometers for SR-XRF and microanalysis

Experimental results are presented obtained with a cryogenically cooled high-resolution X-ray spectrometer based on a 141 × 141 µm Nb-Al-Al2O3-Al-Nb superconducting tunnel junction (STJ) detector in an SR-XRF demonstration experiment. STJ detectors can operate at count rates approaching those of semiconductor detectors while still providing a significantly better energy resolution for soft X-rays. By measuring fluorescence X-rays from samples containing transition metals and low-Z elements, an FWHM energy resolution of 6–15 eV for X-rays in the energy range 180–1100 eV has been obtained. The results show that, in the near future, STJ detectors may prove very useful in XRF and microanalysis applications.