Speakers
Description
The capabilities of the Coincident Doppler-Broadening Spectrometer at the Neutron-induced Positron Source Munich (NEPOMUC) will be presented. In addition an overwiew of planned expansions will be given.
Two beam modes are available: standard operations provide a beam spot of $> 300\ \mu\textrm{m}$ (FWHM) and micro beam for scanning with a reduced diameter of $33\ \mu$m (FWHM). Mearsurements may either be conducted as standard Doppler-broadening spectroscopy (DBS) where the signal at each detector is treated separately or in coincident Doppler-broadening mode (CDBS) where the detectors are run as coincidence pairs. CDBS provides a greatly improved signal to noise ratio ($10^{8}$) allowing the analysis of the chemical surrundings of defect. Currently four different sample holders are available: i) a piezo x-y stage for precision 2D scanning and hence 3D defect imaging, ii) a heatable sample holder with T$_{max}=1100\ \textrm{K}$ for T dependent defect spectroscopy, iii) a cryostat with T$_{min}=40\ \textrm{K}$, iv) a device for in situ tensile tests. Ongoing improvement works include: an automated beam optimization system from which especially the micro beam mode will greatly profit. A planned increase in the number of detectors combined with an upgrade of the readout electronics, which should considerably reduce measurement times.
