Superconducting NbTaAlAlOxAl X-ray detectors with spatial resolution
Abstract Superconducting X-ray detectors based on SIS tunnel junctions offer potential for high spectral resolution and single photon efficiency. When used in a double junction geometry, they also offer spatial resolution needed for focal plane imaging. We are developing NbTaAlAlOxAl detectors for space-based X-ray astronomy applications. The design employs superconductor bandgap engineering for improved charge collection and adaptability for double junction geometries. For irradiation of a single junction device with 6 keV X-rays at a single location, the detectors have an energy resolution of 87 eV at 0.27 K. Initial studies of double junction detectors show a spectral resolution of 178 eV and an inferred spatial resolution of 4 μm over an effective length of 60 μm.
Single photon imaging X-ray spectrometers using low noise current preamplifiers with dc voltage bias
We have developed superconducting single-photon imaging X-ray detectors with an energy resolution of 54 eV at 6 keV and a spatial resolution of 1 /spl mu/m over an effective length of 40 /spl mu/m. They utilize a current-sensitive low-noise preamplifier with a dc voltage bias. It has a signal bandwidth of 300 kHz, current noise of i/sub n/=0.26 pA//spl radic/(Hz) and voltage noise of e/sub n/=0.5 nV//spl radic/(Hz) with an input capacitance of 200 pF under operating conditions. Injected pulses with a charge Q=3.7/spl middot/10/sup 6/ electrons have been measured with a standard deviation /spl sigma/Q=3400 electrons, corresponding to an electronic noise of 13 eV at 6 keV.
One hundred percent tumor induction in mouse skin after repeated beta irradiation in a limited dose range.
Repeated beta irradiation of the backs of mice three times a week with radiation doses of 250 to 1180 cGy per exposure induced 100% incidence of tumors. The incidence of skin tumors appeared to be determined by the total number of repeated exposures in this dose range. An abrupt delay in tumor emergence was observed when the radiation dose was reduced from 250 to 150 cGy per exposure, indicating the existence of a critical threshold. Mouse skin resembles human skin rather than rat skin in its response to radiation.