Characterization of iLGADs using soft X-rays

Experiments at synchrotron radiation sources and X-ray Free-Electron Lasers in the soft X-ray energy range ($250$eV--$2$keV) stand to benefit from the adaptation of the hybrid silicon detector technology for low energy photons. Inverse Low Gain Avalanche Diode (iLGAD) sensors provide an internal gain, enhancing the signal-to-noise ratio and allowing single photon detection below $1$keV using hybrid detectors. In addition, an optimization of the entrance window of these sensors enhances their quantum efficiency (QE). In this work, the QE and the gain of a batch of different iLGAD diodes with optimized entrance windows were characterized using soft X-rays at the Surface/Interface:Microscopy beamline of the Swiss Light Source synchrotron. Above $250$eV, the QE is larger than $55\%$ for all sensor variations, while the charge collection efficiency is close to $100\%$. The average gain depends on the gain layer design of the iLGADs and increases with photon energy. A fitting procedure is introduced to extract the multiplication factor as a function of the absorption depth of X-ray photons inside the sensors. In particular, the multiplication factors for electron- and hole-triggered avalanches are estimated, corresponding to photon absorption beyond or before the gain layer, respectively.Comment: 16 pages, 8 figure

Hybrid pixel detectors : Characterization and optimization

Vid tidpunkten för disputationen var följande delarbete opublicerat: delarbete 8 inskickat.At the time of the doctoral defence the following paper was unpublished: paper 8 submitted.</p

Simulation of the Spectral Response of a Pixellated X-Ray Imaging Detector in Single Photon Processing Mode

X-ray imaging with spectral resolution, “Color X-ray imaging” is a new imaging technology that is currently attracting a lot of attention. It has however been observed that the quality of spectral response is degraded as the pixel size is reduced. This is an effect of charge sharing where the signal from a photon absorbed close to the border between two pixels is shared between pixels. This effect is caused by both diffusion during the charge transport and X-ray fluorescence in heavy detector materials. In order to understand the behavior of pixellated detectors with heavy detector materials operating in single photon processing mode, we have simulated the X-ray interaction with the sensor and the transport of the charge to the readout electrode using a Monte Carlo model for the X-ray interaction and a drift diffusion model for the charge transport. By combining these models, both signal and noise properties of the detector can be simulated

Readout cross-talk for alpha-particle measurements in a pixelated sensor system

Simulations in Medici are performed to quantify crosstalk and charge sharing in a hybrid pixelated silicon detector. Crosstalk and charge sharing degrades the spatial and spectral resolution of single photon processing X-ray imaging systems. For typical medical X-ray imaging applications, the process is dominated by charge sharing between the pixels in the sensor. For heavier particles each impact generates a large amount of charge and the simulation seems to over predict the charge collection efficiency. This indicates that some type of non modelled degradation of the charge transport efficiency exists, like the plasma effect where the plasma might shield the generated charges from the electric field and hence distorts the charge transport process. Based on the simulations it can be reasoned that saturation of the amplifiers in the Timepix system might generate crosstalk that increases the charge spread measured from ion impact on the sensor

Maximized wood chip impregnation efficiency validated by new miniaturized X-ray fluorescence techniques

Manufacturing of chemi-thermomechanical pulp (CTMP) is increasing due to increased demand for packaging materials such as cardboard as well as tissue and other hygiene products. Today high yield pulp (HYP) is produced from different wood species. It is well-known that chip-refining is normally responsible for more than 60% of the electric energy consumption in most high yield pulping process. There are opportunities to improve energy efficiency and quality stability in defibration processes by means of optimizing impregnation. Impregnation is a key unit operation in CTMP production as well as in all chemical pulping and biorefinery systems. The efficiency of the impregnation is known to be crucial (Ferritsius et al. 1985; Gorski et al. 2010). Early research showed difficulties to achieve even distribution of sulphite and sodium ions in wood chips resulting in inhomogeneous fibre properties (Bengtsson et al. 1988). Increased and homogenous sulphonation leads to reduced shive content, which is a key factor in all end product applications. To address this issue developing a new type miniaturized X-ray based technique (XRF) to measure local concentration of sulphur and sodium across wood chips and in individual fibres could become a key tool.   The presence of elements as sulphur and sodium can be detected by X-ray fluorescence (XRF) or spectral absorption. At the XRF, images the surface of the sample using specific energies from K-shell or L-shell fluorescence. This method is investigated at the X-ray laboratory in Mid Sweden University research centre STC (Sensitive Things that Communicate) (Norlin et al. 2018). At the spectral absorption, images specific K-shell absorption energies in transmission X-ray images of the sample, a method widely used in medical diagnosis. This transmission method might also be further investigated for this application in the future (Frojdh et al. 2013; Reza et al. 2013). Both methods can be validated by using monoenergetic radiation from synchrotron facilities.   An XRF imaging system uses a collimated X-ray source and a spectroscopic detector. The sample is scanned to make an image of the content of the substances of interest. A specific challenge in this case is that the low energy fluorescence photons from sulphur (S) and sodium (Na) are easily absorbed in air, which makes imaging in a different atmosphere necessary.   The measurement setup has been simulated using MCNP (C. J. Werner, 2017) to validate the system setup and to select the correct, geometry, shielding, filtering and atmosphere for the measurement. The solution was to use a titanium box flooded with helium to minimise the absorption of fluorescence photons and to shield from scattered photons that might disturb the measurement, fig 1. A filter has been added to the X-ray source to make it nearly monoenergetic and to avoid emission of photons with energies close to the expected fluorescence. The system has been used to estimate sodium and sulphur content in low grammage handsheet (CTMP) or single wood chip samples. It is possible to build a laboratory instrument similar to the prototype setup to obtain the distribution of sodium and sulphur in XRF imaging.                                   Figure 1: Photograph of XRF measurement setup with of moveable Helium atmosphere Ti box However, the technique we are developing can become useful in mills to improve and control process efficiency, product properties and to find solutions to process problems in future. In addition, a more even distribution of the sulphonation can reduce specific energy demand in chip refining at certain shive content.   References   1.      Bengtsson, G., Simonson, R., Heitner, C., Beatson, R., and Ferguson, C. (1988): Chemimechanical pulping of birch wood chips, Part 2: Studies on impregnation of wood blocks using scanning electron microscopy and energy dispersive x-ray analysis, Nord. Pulp Paper Res. J. 3 (3), 132-138. 2.      C. J. Werner, (2017): MCNP User's manual, Code Version 6.2, Los Alamos National Laboratory report, LA-UR-17-29981. 3.      Ferritsius, O., and Moldenius, S. (1985): The effect of impregnation method on CTMP properties. In International Mechanical Pulping Conference Proceedings, SPCI, Stockholm (p. 91). 4.      Frojdh, C., Norlin, B. and Frojdh, E. (2013): Spectral X-ray imaging with single photon processing detectors, Journal of Instrumentaion, Volume 8, Article number C02010.   5.      Gorski, D., Hill, J., Engstrand, P., and Johansson, L. (2010): Reduction of energy consumption in TMP refining through mechanical pre-treatment of wood chips, Nord. Pulp Paper Res. J, 25(2), 156-161. 6.      Norlin, B., Reza, S., Fröjdh, C. and Nordin, T. (2018): Precision scan-imaging for paperboard quality inspection utilizing X-ray fluorescence, Journal of Instrumentation, Volume: 13, Article number C01021. 7.      Reza, S., Norlin, B. and Thim, J. (2013): Non-destructive method to resolve the core and the coating on paperboard by spectroscopic x-ray imaging, Nord. Pulp Paper Res. J. 28 (3), 439-442.

Maximized wood chip impregnation efficiency validated by new miniaturized X-ray fluorescence techniques

Manufacturing of chemi-thermomechanical pulp (CTMP) is increasing due to increased demand for packaging materials such as cardboard as well as tissue and other hygiene products. Today high yield pulp (HYP) is produced from different wood species. It is well-known that chip-refining is normally responsible for more than 60% of the electric energy consumption in most high yield pulping process. There are opportunities to improve energy efficiency and quality stability in defibration processes by means of optimizing impregnation. Impregnation is a key unit operation in CTMP production as well as in all chemical pulping and biorefinery systems. The efficiency of the impregnation is known to be crucial (Ferritsius et al. 1985; Gorski et al. 2010). Early research showed difficulties to achieve even distribution of sulphite and sodium ions in wood chips resulting in inhomogeneous fibre properties (Bengtsson et al. 1988). Increased and homogenous sulphonation leads to reduced shive content, which is a key factor in all end product applications. To address this issue developing a new type miniaturized X-ray based technique (XRF) to measure local concentration of sulphur and sodium across wood chips and in individual fibres could become a key tool.   The presence of elements as sulphur and sodium can be detected by X-ray fluorescence (XRF) or spectral absorption. At the XRF, images the surface of the sample using specific energies from K-shell or L-shell fluorescence. This method is investigated at the X-ray laboratory in Mid Sweden University research centre STC (Sensitive Things that Communicate) (Norlin et al. 2018). At the spectral absorption, images specific K-shell absorption energies in transmission X-ray images of the sample, a method widely used in medical diagnosis. This transmission method might also be further investigated for this application in the future (Frojdh et al. 2013; Reza et al. 2013). Both methods can be validated by using monoenergetic radiation from synchrotron facilities.   An XRF imaging system uses a collimated X-ray source and a spectroscopic detector. The sample is scanned to make an image of the content of the substances of interest. A specific challenge in this case is that the low energy fluorescence photons from sulphur (S) and sodium (Na) are easily absorbed in air, which makes imaging in a different atmosphere necessary.   The measurement setup has been simulated using MCNP (C. J. Werner, 2017) to validate the system setup and to select the correct, geometry, shielding, filtering and atmosphere for the measurement. The solution was to use a titanium box flooded with helium to minimise the absorption of fluorescence photons and to shield from scattered photons that might disturb the measurement, fig 1. A filter has been added to the X-ray source to make it nearly monoenergetic and to avoid emission of photons with energies close to the expected fluorescence. The system has been used to estimate sodium and sulphur content in low grammage handsheet (CTMP) or single wood chip samples. It is possible to build a laboratory instrument similar to the prototype setup to obtain the distribution of sodium and sulphur in XRF imaging.                                   Figure 1: Photograph of XRF measurement setup with of moveable Helium atmosphere Ti box However, the technique we are developing can become useful in mills to improve and control process efficiency, product properties and to find solutions to process problems in future. In addition, a more even distribution of the sulphonation can reduce specific energy demand in chip refining at certain shive content.   References   1.      Bengtsson, G., Simonson, R., Heitner, C., Beatson, R., and Ferguson, C. (1988): Chemimechanical pulping of birch wood chips, Part 2: Studies on impregnation of wood blocks using scanning electron microscopy and energy dispersive x-ray analysis, Nord. Pulp Paper Res. J. 3 (3), 132-138. 2.      C. J. Werner, (2017): MCNP User's manual, Code Version 6.2, Los Alamos National Laboratory report, LA-UR-17-29981. 3.      Ferritsius, O., and Moldenius, S. (1985): The effect of impregnation method on CTMP properties. In International Mechanical Pulping Conference Proceedings, SPCI, Stockholm (p. 91). 4.      Frojdh, C., Norlin, B. and Frojdh, E. (2013): Spectral X-ray imaging with single photon processing detectors, Journal of Instrumentaion, Volume 8, Article number C02010.   5.      Gorski, D., Hill, J., Engstrand, P., and Johansson, L. (2010): Reduction of energy consumption in TMP refining through mechanical pre-treatment of wood chips, Nord. Pulp Paper Res. J, 25(2), 156-161. 6.      Norlin, B., Reza, S., Fröjdh, C. and Nordin, T. (2018): Precision scan-imaging for paperboard quality inspection utilizing X-ray fluorescence, Journal of Instrumentation, Volume: 13, Article number C01021. 7.      Reza, S., Norlin, B. and Thim, J. (2013): Non-destructive method to resolve the core and the coating on paperboard by spectroscopic x-ray imaging, Nord. Pulp Paper Res. J. 28 (3), 439-442.

Maximized wood chip impregnation efficiency validated by new miniaturized X-ray fluorescence techniques

Manufacturing of chemi-thermomechanical pulp (CTMP) is increasing due to increased demand for packaging materials such as cardboard as well as tissue and other hygiene products. Today high yield pulp (HYP) is produced from different wood species. It is well-known that chip-refining is normally responsible for more than 60% of the electric energy consumption in most high yield pulping process. There are opportunities to improve energy efficiency and quality stability in defibration processes by means of optimizing impregnation. Impregnation is a key unit operation in CTMP production as well as in all chemical pulping and biorefinery systems. The efficiency of the impregnation is known to be crucial (Ferritsius et al. 1985; Gorski et al. 2010). Early research showed difficulties to achieve even distribution of sulphite and sodium ions in wood chips resulting in inhomogeneous fibre properties (Bengtsson et al. 1988). Increased and homogenous sulphonation leads to reduced shive content, which is a key factor in all end product applications. To address this issue developing a new type miniaturized X-ray based technique (XRF) to measure local concentration of sulphur and sodium across wood chips and in individual fibres could become a key tool.   The presence of elements as sulphur and sodium can be detected by X-ray fluorescence (XRF) or spectral absorption. At the XRF, images the surface of the sample using specific energies from K-shell or L-shell fluorescence. This method is investigated at the X-ray laboratory in Mid Sweden University research centre STC (Sensitive Things that Communicate) (Norlin et al. 2018). At the spectral absorption, images specific K-shell absorption energies in transmission X-ray images of the sample, a method widely used in medical diagnosis. This transmission method might also be further investigated for this application in the future (Frojdh et al. 2013; Reza et al. 2013). Both methods can be validated by using monoenergetic radiation from synchrotron facilities.   An XRF imaging system uses a collimated X-ray source and a spectroscopic detector. The sample is scanned to make an image of the content of the substances of interest. A specific challenge in this case is that the low energy fluorescence photons from sulphur (S) and sodium (Na) are easily absorbed in air, which makes imaging in a different atmosphere necessary.   The measurement setup has been simulated using MCNP (C. J. Werner, 2017) to validate the system setup and to select the correct, geometry, shielding, filtering and atmosphere for the measurement. The solution was to use a titanium box flooded with helium to minimise the absorption of fluorescence photons and to shield from scattered photons that might disturb the measurement, fig 1. A filter has been added to the X-ray source to make it nearly monoenergetic and to avoid emission of photons with energies close to the expected fluorescence. The system has been used to estimate sodium and sulphur content in low grammage handsheet (CTMP) or single wood chip samples. It is possible to build a laboratory instrument similar to the prototype setup to obtain the distribution of sodium and sulphur in XRF imaging.                                   Figure 1: Photograph of XRF measurement setup with of moveable Helium atmosphere Ti box However, the technique we are developing can become useful in mills to improve and control process efficiency, product properties and to find solutions to process problems in future. In addition, a more even distribution of the sulphonation can reduce specific energy demand in chip refining at certain shive content.   References   1.      Bengtsson, G., Simonson, R., Heitner, C., Beatson, R., and Ferguson, C. (1988): Chemimechanical pulping of birch wood chips, Part 2: Studies on impregnation of wood blocks using scanning electron microscopy and energy dispersive x-ray analysis, Nord. Pulp Paper Res. J. 3 (3), 132-138. 2.      C. J. Werner, (2017): MCNP User's manual, Code Version 6.2, Los Alamos National Laboratory report, LA-UR-17-29981. 3.      Ferritsius, O., and Moldenius, S. (1985): The effect of impregnation method on CTMP properties. In International Mechanical Pulping Conference Proceedings, SPCI, Stockholm (p. 91). 4.      Frojdh, C., Norlin, B. and Frojdh, E. (2013): Spectral X-ray imaging with single photon processing detectors, Journal of Instrumentaion, Volume 8, Article number C02010.   5.      Gorski, D., Hill, J., Engstrand, P., and Johansson, L. (2010): Reduction of energy consumption in TMP refining through mechanical pre-treatment of wood chips, Nord. Pulp Paper Res. J, 25(2), 156-161. 6.      Norlin, B., Reza, S., Fröjdh, C. and Nordin, T. (2018): Precision scan-imaging for paperboard quality inspection utilizing X-ray fluorescence, Journal of Instrumentation, Volume: 13, Article number C01021. 7.      Reza, S., Norlin, B. and Thim, J. (2013): Non-destructive method to resolve the core and the coating on paperboard by spectroscopic x-ray imaging, Nord. Pulp Paper Res. J. 28 (3), 439-442.

Discrimination of aluminum from silicon by electron crystallography with the Jungfrau detector

The crystal structure of a chemical compound serves several purposes: its coordinates represent three-dimensional information about the connectivity between the atoms; it is the only technique that determines the absolute configuration of chiral molecules; it enables determining structure–function relations; and crystallographic data at atomic resolution distinguish between element types and serve as a confirmation of synthesis protocols. Here, we collected electron diffraction data from albite and from a Linde Type A (LTA) type zeolite. Both compounds are aluminosilicates with well-defined silicon and aluminum crystallographic sites. Data were recorded with the “adJUstiNg Gain detector FoR the Aramis User station” (JUNGFRAU detector) and we made use of its capability of energy discrimination to suppress noise. For both compounds, crystallographic refinement distinguishes correctly between silicon and aluminum, even though these elements have very similar electron scattering factors. These results highlight the quality of the electron diffraction data and the reliability of the models for chemical interpretation. Further development in this direction will provide enormous opportunities for structure–function studies by diffraction.ISSN:2073-435

Spectral response of the energy-binning Dosepix ASIC coupled to a 300 mu m silicon sensor under high fluxes of synchrotron radiation

The Dosepix hybrid pixel detector was designed for dosimetry and radiation monitoring applications. It has three programmable modes of operation: photon counting mode, energy integration mode, and dosimetry mode. The dosimetry mode measures the energy of individual X-ray photons and automatically sorts events into pre-defined energy bins. The output is a histogram representing the measured X-ray energy spectrum, permitting a dose reconstruction that accounts for the attenuation of photons at each energy bin. This presents a potential radiation protection and dosimetry instrument in medical radiodiagnostic practices, including high flux systems such as computed tomography (CT). In this paper, we characterise the Dosepix chip by investigating the energy response and count rate capabilities when coupled to a 300 pm silicon sensor under high fluxes of monochromatic synchrotron radiation. Under nominal settings, the Dosepix detector can detect photons down to 3.5 keV, with an energy resolution of 16.5% FWHM for 8.5 keV photons and 8% FWHM for 40 keV photons. The chip can count up to 1.67 Mcps/mm(2) of 40 keV photons whilst maintaining linear counting behaviour. This count rate range can be further increased by changing the programmable operating settings of the detector, making it suitable for a range of photon dosimetry applications