Ultra-thin optical grade scCVD diamond as X-ray beam position monitor

Abstract

Results of measurements made at the SIRIUS beamline of the SOLEIL synchrotron for a new X-ray beam position monitor based on a super-thin single crystal of diamond grown by chemical vapor deposition (CVD) are presented. This detector is a quadrant electrode design processed on a 3 µm-thick membrane obtained by argon-oxygen plasma etching the central area of a CVD-grown diamond plate of 60 µm thickness. The membrane transmits more than 50% of the incident 1.3 keV energy X-ray beam. The diamond plate was of moderate purity (∼1 p.p.m. nitrogen), but the X-ray beam induced current (XBIC) measurements nevertheless showed a photo-charge collection efficiency approaching 100% for an electric field of 2 V µm(-1), corresponding to an applied bias voltage of only 6 V. XBIC mapping of the membrane showed an inhomogeneity of more than 10% across the membrane, corresponding to the measured variation in the thickness of the diamond plate before the plasma etching process. The measured XBIC signal-to-dark-current ratio of the device was greater than 10(5), and the X-ray beam position resolution of the device was better than a micrometer for a 1 kHz sampling rate.

Pulse-resolved intensity measurements at a hard X-ray FEL using semi-transparent diamond detectors

“…X-ray pulse intensities at XFELs are sufficiently high to give a strong detector signal even if the absorption is only 1% or below. Si detectors are available down to 5 mm (Fuchs et al, 2008) and diamond detectors are now reaching thicknesses down to 20 mm (Shimaoka et al, 2016) for large areas and even less if the diamond crystal is thinned down over a limited region (Desjardins et al, 2014). However, already at a thickness of 40 mm, diamond absorbs less than 22% for energies above 5 keV (see Fig.…”

“…Single-crystalline chemical vapor deposited (scCVD) diamond detectors have been used previously at synchrotron sources, either as intensity monitors De Sio et al, 2007;Keister & Smedley, 2009) or as quadrant beam position monitors (BPMs) (Morse et al, , 2010Bohon et al, 2010;Keister et al, 2011;Desjardins et al, 2014). In addition, homogeneous BPMs using electrodes on each crystal edge (Pomorski et al, 2009) are available.…”

Current advances in synchrotron radiation instrumentation for MX experiments

“…For monochromatic X-ray beams, a variety of position monitors are used: CVD diamond quadrant electrode photo current monitors with a polycrystalline (Shu et al , 1998, Sehr et al , 2004), (Dectris Rigi) or a single crystalline membrane (Desjardins et al , 2014, Marinelli et al , 2012, Muller et al , 2012), quadrant diode monitors detecting backscatter fluorescence from a metal foil (Alkire et al , 2000) and split electrode ion chambers (Menk et al , 2006, Sato et al , 2004, Schildkamp & Pradervand, 1995). All of these can double as intensity monitors.…”

X-ray position-sensitive duo-lateral diamond detectors at SOLEIL

“…it does not need any photolithography or precise coating processes. Furthermore, the PSD is an all-carbon device; therefore it represents a good solution for low-energy applications (Desjardins et al, 2014;Gaowei et al, 2015). However, the possible disadvantages, with respect to the quadrant detector, come from the PSD resistive coating, which generates an additional noise source and makes it slower due to the higher RC constant.…”