Limitations on energy resolution of segmented silicon detectors

Abstract

In the paper experimental study of charge division effects and energy resolution of X-ray silicon pad detectors are presented. The measurements of electrical parameters, capacitances and leakage currents, for six different layouts of pad arrays are reported. The X-ray spectra have been measured using a custom developed dedicated low noise front-end electronics. The spectra measured for six different detector layouts have been analysed in detail with particular emphasis on quantitative evaluation of charge division effects. Main components of the energy resolution due to Fano fluctuations, electronic noise, and charge division, have been estimated for six different sensor layouts. General recommendations regarding optimisation of pad sensor layout for achieving best possible energy resolution have been formulated.

Radiation damage effects caused by soft X-rays in silicon pad detectors

“…The PDH outputs are sampled simultaneously for all channels and then read out by four 16 channel ADCs. More details on the design and performance of the detector can be found in [4]. Since the pads are DC coupled to the front-end electronics for this module we can monitor only the total sensor current at the backplane including the current of the active area and of the guard ring.…”

“…Figure 2(b) shows the evolution of inter-pad capacitance during irradiation for frequency test signal of 10 kHz and for a bias voltage of 300 V. After the first annealing session, during which the sensor was kept with no bias and at room temperature we have observed the increase of inter-pad capacitance from 215 fF to 225 fF with no change over 8 days. One may note that the inter-pad capacitance reported in [4] for the same sensor layout was somewhat lower (190 fF), but those measurements were taken between a given pad and its four neighbours while in the current setup we measure the capacitance between a central pad and all other pads on the sensor. The I-V characteristics of the active pad area for different dose, in steps of 20 Gy, are shown in figure 3(a).…”

“…In this paper we report on investigation of radiation effects in silicon pad sensors. We have already investigated the charge division effects in such sensors and their spectroscopic performance [4]. Such sensors combined with low noise front-end electronics allow us to achieve energy resolution of 220 eV FWHM @ 5.9 keV at room temperature.…”

Application of Factorisation Methods to Analysis of Elemental Distribution Maps Acquired with a Full-Field XRF Imaging Spectrometer

“…The investigated object is illuminated by a broad X-ray beam, and the fluorescence radiation is projected onto a 2-D position-sensitive detector through an optical system like, for example, a multihole collimator or a pin-hole camera, as shown in Figure 1 . There is no obvious choice for the type of detector for such applications as typically the energy resolution of position-sensitive detectors is compromised by physical effects, like charge division [ 23 ], and by technical constraints. Different types of detectors have been tried by other groups for such applications: a detector based on a Charge Coupled Device (CCD) used in a special spectroscopic mode [ 21 , 24 , 25 , 26 ], a pixel detector [ 27 , 28 ], a gaseous Micro Hole Strip Plate (MHSP) detector [ 29 ], and a gaseous detector based on the technology of Thick Gas Electron Multiplier (THGEM) [ 22 ], called THCOBRA.…”