XRF element localization with a triple GEM detector using resistive charge division

Abstract

In this work we show the operation and results of an X-ray fluorescence imaging system using a cascade of three gas electron multipliers (GEM) and a pinhole assembly. The detector operates in Ar/CO 2 (90/10) at atmospheric pressure, with resistive chains applied to the strip readout, which allow to use only five electronic channels: two for each dimension and a fifth for energy and trigger. The corrections applied to the energy spectra to compensate for small changes in the signal amplitude and also differences in gain throughout the sensitive area are described and the clear improvement of the energy resolution is shown.To take advantage of the simultaneous sensitivity to the energy and to the position of interaction, a color scale matching the energy spectrum to the RGB range was applied, resulting in images where the color has a direct correspondence to the energy in each pixel and the intensity is reflected by the brightness of the image. The results obtained with four different color pigments are shown.

Double-GEM based thermal neutron detector prototype

“…In order to reconstruct the event's position, we use Eq. 2.1 [18], where 𝑄 is the charge information collected from the bottom of the last GEM, and 𝐿 𝑥 and 𝐿 𝑦 are the lengths of the sensitive area for each direction. As indicated in Fig.…”

“…14. Slow gain changes due to environmental changes are easily seen as a tendency in the sequence of the points, whose energy spectrum can be drifted by a reasonable amount as it happens in the case reported by [18]. The tendency analysis can be carried out by fitting the behaviour of the difference between each peak position and the average position of all peaks, which we labelled as Δ peak in the Fig.…”

Double-GEM based thermal neutron detector prototype

“…In order to reconstruct the event's position, we use eq. (2.1) [18], where 𝑄 is the charge information collected from the bottom of the last GEM, and 𝐿 𝑥 and 𝐿 𝑦 are the lengths of the sensitive area for each direction. As indicated in figure 4, 𝑋 1 and 𝑋 2 are the signals collected at each end of the resistive chain in the X direction, while 𝑌 1 and 𝑌 2 are the equivalent signals in the Y direction.…”

“…One versatile alternative for neutron detection consists of using one of the referred neutron converter isotopes with the Gas Electron Multiplier (GEM) [13], a microstructure widely used to detect charged particles that can cover large sensitive areas, present fair energy and position resolutions as well as robustness. These aspects consolidated these microstructures, which are already in use in several applications, such as high energy physics [14][15][16], muon tomography [17], X-rays fluorescence imaging [18], and, more recently, neutron detection [19][20][21][22].…”

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

“…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. Application of the Gas Electron Multiplier (GEM) detector with the resistive divider readout has also been tried [ 30 ].…”