| 1. |
- Fröjdh, Anna, 1986-, et al.
(författare)
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Processing and characterization of a MEDIPIX2-compatible silicon sensor with 220 mu m pixel size
- 2011
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 633:Suppl 1, s. S78-S80
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Tidskriftsartikel (refereegranskat)abstract
- Pixellated silicon detectors with a pixel size of 220 um have been fabricated at Mid Sweden University. The detectors will be bonded to the MEDIPIX2 [1] readout chip. The purpose is to investigate the performance of an energy sensitive X-ray imaging sensor with reduced charge sharing.The detectors were fabricated on high purity silicon with a wafer thickness of 500 um and a resistivity of more than 15 kohmcm. One reason for the choice of material was to get experience for future work with very thick detectors requiring ultra high resistivity in order to be depleted. During the initial work in this project some issued were found concerning inter pixel resistance and the efficiency of the guard rings. This led to a study of existing papers on the subject [2,3,4,5] and to extensive simulations of the electric field and the charge transport in different parts of the device.A modified process has been developed using alternating p+ and n+ guard rings and an outer n+ doping. The results of the simulations and the process will be described as well as an outline for a process for fabrication of very thick detectors with limited guard ring extension.References[1] - X. Llopart, M. Campbell, R. Dinapoli, D. San Segundo and E. Pernigotti, IEEE Trans. Nucl. Sci., vol. 49, 2279-2283, October 2002.[2] – L. Evensen, A. Hanneborg, B Sundby Avset, M. Mese, Nuclear Instruments and Methods in Physics Research A 337 (1993) 44 – 52[3] – T. Pavalainen, T. Tuuva, K. Leinonen, Nuclear Instruments and Methods in Physics Research A 573 (2007) 277 – 279[4] – Z. Li, W. Huang, L. J. Zhao, IEEE Trans. Nucl. Sci., vol. 47, No. 3. 729 – 735 , June 2000.[5] – D. Han, C. Wang, G. Wang, S. Du, L. Shen, X. Tian, X. Zhang, IEEE Transactions on Electron devices, Vol. 50, No. 2, 537 – 540, February 2003
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| 2. |
- Fröjdh, Christer, et al.
(författare)
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Characterization of area sensitivity in 55 um pixellated CdTe X-ray imaging detectors
- 2007
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Ingår i: IEEE Nuclear Science Symposium Conference Record. - New York : IEEE conference proceedings. - 9781424409228 ; , s. 1234-1236
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Konferensbidrag (refereegranskat)abstract
- X-ray imaging detectors with energy resolution, based on a single photon processing CMOS readout circuit attached to a detector chip, are being developed by different groups. In order to achieve high quantum efficiency it is preferable to use high-Z semiconductor materials. However the fluorescent X-ray photons of such materials have high energies and are able to travel long distances thereby reducing both the spatial resolution and the energy resolution of the detector. In addition charge sharing in the detector and non-uniformities in both the detector and the readout electronics will affect the signal. In this work we have characterized a 1 mm thick CdTe detector with a pixel size of 55 um x 55 um, bump bonded to the MEDIPIX2 single photon processing readout chip. The area sensitivity of the detector is evaluated using a narrow X-ray beam of monoenergetic photons. From these measurements the effects of fluorescence and charge sharing can be evaluated.
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| 3. |
- Fröjdh, Erik, 1984-, et al.
(författare)
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Spectral response of a silicon detector with 220 mu m pixel size bonded to MEDIPIX2
- 2011
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 633:Supplement 1, s. S125-S127
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Tidskriftsartikel (refereegranskat)abstract
- The standard detector used with the MEDIPIX2 [1] readout chip suffers from severe charge sharing that reduces the spectral performance of the device. This problem is expected to be solved in the MEDIPIX3 [2] design. In order to significantly reduce the charge sharing and to make a detector which could be expected to have a similar response to MEDIPIX3 we have fabricated detectors with a pixel size of 220 um and bonded these detectors to the MEDIPIX2 chip using only a limited number of pixels on the readout chip. This makes the active area of the pixel comparable with the area covered by the charge summing in MEDIPIX3.The charge collection properties of the device have been tested by scanning a narrow beam over a pixel. The spectral response has been measured by taking a flood exposure at different tube voltages and comparing the result with the spectrum obtained from exposing the centre of the pixel with a narrow beam thus eliminating the charge sharing. This work represents an improved characterisation as compared to [3].Some initial images of different objects have been taken by placing the device in an X-ray microscope with a nanofocus X-ray tube imaging objects with magnification to simulate the original pixel size of 55 um.References[1] - X. Llopart, M. Campbell, R. Dinapoli, D. San Segundo and E. Pernigotti, IEEE Trans. Nucl. Sci., vol. 49, 2279-2283, October 2002.[2] - R. Ballabriga, M. Campbell, E. H. M. Heijne, X. Llopart, L. Tlustos, IEEE Trans. Nucl. Sci., Vol. 54, No. 5, October 2007.[3] – B. Norlin, C. Fröjdh, G. Thungström, D. Greiffenberg, NSS Conference record,19-25 Oct. 2008, Pages:3464 – 3469, Digital Object Identifier 10.1109/NSSMIC.2008.4775083
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| 4. |
- Norlin, Börje, 1967-, et al.
(författare)
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Energy Resolved X-ray Imaging as a Tool for Characterization of Paper Coating Quality
- 2009
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Ingår i: IEEE Nuclear Science Symposium Conference Record 2009. - : IEEE conference proceedings. - 9781424439621 ; , s. 1703-1706
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Konferensbidrag (refereegranskat)abstract
- Energy resolved X-ray imaging can be used as a tool to analyze the variation in the chemical content of an object. In this work we have used energy resolved X-ray imaging to measure the variation in the chemical content of paper and paper coating. This is an important quality parameter for the paper industry. In order to separate the variation in coating thickness from the variation in paper thickness, energy resolution is used to separate the response of the coating from the response of the paper. The MEDIPIX2 single photon processing X-ray imaging system [1] has been used in the measurements. The measurement results are compared to simulations with MCNP. The influence of charge sharing is discussed and the effects have been studied by comparing results from detectors with 220x220 µm2 pixels and detectors with 55x55 µm2 pixels. There is a trade-off between good spatial resolution obtained with detectors with small pixels and good energy resolution obtained with detectors with large pixels. The requirements on image quality, to achieve the resolution of coating distribution relevant for the application, are discussed.
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| 5. |
- Norlin, Börje, 1967-, et al.
(författare)
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Spectroscopic X-Ray Imaging Using a Pixelated Detector with Single Photon Processing Readout
- 2010
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Ingår i: Proceedings of 2010 IEEE NUCLEAR SCIENCE SYMPOSIUM CONFERENCE. - : IEEE conference proceedings. - 9781424491063 ; , s. 1074-1078
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Konferensbidrag (refereegranskat)abstract
- Color informatics to analyze the object content in Xray images is an emerging technology. Identification of different elements for applications such as medical contrast agent imaging is possible using energy resolving X-ray imaging sensors. In this work RGB representations of transmission images of ground elements achieved with the MEDIPIX system are exemplified.
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| 6. |
- Fröjdh, Anna, et al.
(författare)
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An alpha particle detector for measuring radon levels
- 2010
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Ingår i: Proceedings of Nuclear Science Symposium Conference Record (NSS/MIC), 2010. - : IEEE conference proceedings. - 9781424491063 ; , s. 460-461
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Konferensbidrag (refereegranskat)abstract
- An alpha particle detector for measuring radon levels through measurement of radon progeny concentration has been developed. The detector is a silicon diode optimized for these measurements. Different alternating and non-alternating guard ring structures and different doping profiles have been investigated.
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| 7. |
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| 8. |
- Fröjdh, Anna, et al.
(författare)
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An optimized system for measurement of radon levels in buildings by spectroscopic measurement of radon progeny
- 2011
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 6:12, s. art. no. C12018-
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Tidskriftsartikel (refereegranskat)abstract
- Radon gas, Rn-222, is a problem in many buildings. The radon gas is not harmful in itself, but the decay chain contains charged elements such as Po-218, and Po-214 ions which have a tendency to stick to the lungs when inhaled. Alpha particles from the decay of these ions cause damages to the lungs and increase the risk of lung cancer. The recent reduction in the limits for radon levels in buildings call for new simple and efficient measurement tools [1]. The system has been optimized through modifications of the detector size, changes to the filters and the design of the chamber. These changes increase the electric field in the chamber and the detection efficiency.
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| 9. |
- Harju, Anne
(creator_code:cre_t, creator_code:res_t)
-
Forskarnas galleri #3 : Space & Place: forskning om social hållbarhet i Malmö
- 2017
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Konstnärligt arbeteabstract
- I Malmö bor cirka 330 000 människor. Hälften av invånarna i Malmö är under 35 år och en femtedel är under 18 år. I utställningen Space & Place kan du ta del av hur två forskargrupper undersöker barns och ungas relation till några av stadens rum. Utställningen belyser metoder i forskningsprocessen.Projekten utgår från barns och ungas upplevelser av sin närmiljö. Forskningen är exempel på hur Malmö högskola bidrar till ett socialt hållbart Malmö.
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| 10. |
- Reza, Salim, 1985-
(författare)
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Phase-Contrast and Spectroscopic X-ray Imaging for Paperboard Quality Assurance
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The end-use performance of a paperboard depends on its quality.The major properties of a good quality paperboard include consistencyin the expected ratio between the thickness of the core andthe coating layers, and the uniformity in the coating layer. Measurementsystems using X-rays to monitor these properties could assistthe paperboard industries to assure the quality of their products in anon-destructive and automatic manner. Phase Contrast X-ray Imaging (PCXI) has been used successfullyto look inside a wide range of objects using synchrotron radiationsources. Recent advancements in the grating interferometer basedPCXI technique enables high quality phase-contrast and dark-fieldimages to be obtained using conventional X-ray tubes. The darkfieldimages map the scattering inhomogeneities inside objects andis very sensitive to micro-structures, and thus, can reveal useful informationabout the object’s inner structures, such as, the fibre structuresinside paperboards. In this thesis, methods, using spectroscopic X-ray imaging andPCXI technique have been demonstrated to measure paperboard quality.The thicknesses of the core and the coating layers on a paperboardwith the coating layer on only one side can be measured usingspectroscopic X-ray imaging technique. However, the limitedspectral and spatial resolution offered by the measurement systembeing used led to the measured thicknesses of the layers being lowerthan their actual thicknesses in the paperboard sample. Suggestionshave been made in relation to overcoming these limitations and toenhance the performance of the method. The dark-field signals from paperboard samples with different qualityindices are analysed. The isotropic and the anisotropic scatteringcoefficients for all of the samples have been calculated. Basedon the correlation between the isotropic coefficients and the qualityindices of the paperboards, suggestions have been made for paperboardquality measurements.
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