Calorimetric low temperature detectors for mass identification of heavy ions

The energy sensitive detection of heavy ions with calorimetric low temperature detectors (CLTDs) is investigated for the energy range E = 0.1-1 MeV/u, commonly used for accelerator mass spectrometry (AMS). Such measurements complement earlier investigations [1, 2] at higher energies (E = 5-300 MeV/u) where an energy resolution of DeltaE/E = 1-2 x 10(-3) was obtained for various ion species. The detectors used consist of sapphire absorbers and superconducting transition edge thermometers operated at T approximate to 1.5 K. They were irradiated with various heavy ion beams (C-13, Au-197, U-238) provided b the VERA tandem accelerator in Vienna, Austria, An energy resolution of DeltaE/E = 5-6 x 10(-3) has been obtained even for heaviest ions like Au-197 and U-238 at E = 0.1-0.3 MeV/u, thereby exceeding the resolution of conventional semiconductor detectors in this energy range by at least one order of magnitude. In addition, no evidence for pulse height defects has been observed, With the achieved performance, the present CLTDs bear a large potential for applications in various fields of heavy ion research. Of special interest is isotope mass identification via combined energy and time-of-flight (TOF) measurement. In present test measurements, including a standard TOF spectrometer, a clear separation of the isotopes Pb-206 and Pb-208 at E approximate to 0.1 MeV/u has been obtained. Such a detection scheme may in future provide substantial background suppression for AMS measurements.