Impact of diffusion on the ionisation channel of a diamond XBPM® detector

• Main Authors: Christina, Weiss, Helmut, Frais-Kölbl, Erich, Griesmayer, Pavel, Kavrigin, Julian, Melbinger
• Format: Conference Proceeding
• Language: English
• Subjects: Atomic properties; Current carriers; Diamonds; Electrons; Ion charge; Ionization; Light sources; Measuring instruments; Position measurement; Synchrotrons; Thermal conductivity; Thickness; X-rays
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/5.0168374

Nowadays in Synchrotron Light Sources, the state-of-the-art beam position monitors are Diamond XBPM® [1, 2]. They are used in experimental X-ray beam lines for precision measurements and fast control of the beam position and intensity. Diamond is the best-suited low-absorbing detector material due to its low atomic number Z and the use of pure diamond yields a linear signal response. For hard X-rays the application of Diamond XBPM® has no limit. The limits at low photon energies are determined by the thickness of the sensor and the transmission. Diamond detectors can be produced as thin as 3 μm [3], which is adequate with 1.6 keV X-Rays at 50% transmission. Standard thicknesses are 10 μm for 4.3 keV, 20 μm for 5.4 keV and 50 μm for 7.2 keV at 90% transmission. The superior thermal conductivity of diamond allows the highest ionisation levels and highest X-ray beam intensities. Diamond XBPM® are four-quadrant measurement devices. The technological limit for the gap size between the pads is 1 μm. With Diamond XBPM®, however, even beams as small as 60 nm were measured with the highest precision. This is helped by the diffusion of the ionization charge. Diffusion causes a lateral widening of the ionisation channel which increases the measurement precision for small beams. In this paper, we discuss the effect of charge-carrier diffusion in Diamond XBPM®.