An Experimental Comparison of Single Crystal CVD Diamond and 4H-SiC Synchrotron X-Ray Beam Diagnostics
21
C.E. Houghton, C. Bloomer, L. Bobb
DLS, Oxfordshire, United Kingdom
As synchrotron beamlines increasingly use micro-focus techniques with detectors sampling at kHz rates, the need for real-time monitoring of the beam position at similar bandwidths is vital. Commercially available single-crystal CVD diamond X-ray diagnostics are well established as excellent non-destructive monitors for synchrotron X-ray beamlines. Silicon carbide (4H-SiC) X-ray beam position monitors (XBPMs) are a recent development with the potential to provide the same benefits as their diamond counterparts with larger usable apertures and lower cost. At Diamond Light Source a comparison between single-crystal CVD diamond and 4H-SiC XBPMs has been carried out. The sc-diamond and 4H-SiC beam position monitors are mounted in-line along the beam path, so that synchronous kHz measurements of the synchrotron X-ray beam motion can be measured. Several tests of the two position monitors performance are presented: comparing kHz beam position measurements from the detectors, temporal response, and signal uniformity across the face of the detectors. Each test is performed with varying bias voltages applied to the detectors. A discussion of the benefits and limitations of 4H-SiC and diamond detectors is included.
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Single-Crystal Diamond Pixelated Radiation Detector with Buried Graphitic Electrodes
158
C. Bloomer, L. Bobb
DLS, Oxfordshire, United Kingdom
M.E. Newton
University of Warwick, Coventry, United Kingdom
A new type of transmissive pixel detector has been developed for synchrotron radiation diagnostics at Diamond Light Source. A thin single-crystal CVD diamond plate is used as the detector material, and a pulsed-laser technique has been used to write conductive graphitic electrodes inside the diamond plate. Instead of using traditional electrodes formed from a layer of surface metallisation, the graphitic electrodes are buried under the surface of the diamond and result in an all-carbon imaging detector. Within the instrument’s transmissive aperture there are no surface structures that could be damaged by exposure to radiation beams, and no surface metallization that could introduce unwanted absorption edges. The instrument has successfully been used to image the X-ray beam profile and measure the beam position to sub-micron accuracy at 100 Hz at Diamond Light Source. A novel modulation lock-in technique is used to read out all pixels simultaneously. Presented in this work are measurements of the detector’s beam position resolution and intensity resolution. Initial measurements of the instrument’s spread-function are also presented. Numerical simulations are used to identify potential improvements to the electrode geometry to improve the spatial resolution of similar future detectors. The instrument has applications in both synchrotron radiation instrumentation, where real-time monitoring of the beam profile is useful for beam diagnostics and fault-finding, and particle tracking at colliders, where the electrode geometries that buried graphitic tracks can provide increased the charge collection efficiency of the detector.
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