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| 2. |
- Iacobaeus, C., et al.
(författare)
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A high position resolution X-ray detector : An Edge on illuminated capillary plate combined with a gas amplification structure
- 2006
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Ingår i: IEEE Transactions on Nuclear Science. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9499 .- 1558-1578. ; 53:2, s. 554-561
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Tidskriftsartikel (refereegranskat)abstract
- We have developed and successfully tested a prototype of a new high position resolution hybrid X-ray detector. It contains a thin-wall lead glass capillary plate converter of X-rays combined with a microgap parallel-plate avalanche chamber operating in various gas mixtures at 1 atm. The operation of these converters was studied in a wide range of X-ray energies (from 6 to 60 keV) at incident angles varying from 0-90 degrees. The detection efficiency, depending on the geometry, photon's energy, incident angle and the mode of operation was between 5-30% in single step mode and up to 50% in a multi-layered combination. Depending on the capillary's geometry, the position resolution achieved was between 50-250 mu m in digital form and was practically independent of the photon's energy or gas mixture. The usual lead glass capillary plates operated without noticeable charging up effects at counting rates of 50 Hz/mm(2) and hydrogen treated capillaries-up to 10(5) Hz/mm(2). The developed detector has several important potential advantages over the exciting X-ray detectors and may open new possibilities for medical imaging, for example in mammography, portal imaging, radiography (including security devices), as well as many other applications.
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| 3. |
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| 4. |
- Iacobaeus, C., et al.
(författare)
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Advances in capillary-based gaseous UV imaging detectors
- 2004
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 525:02-jan, s. 42-48
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Tidskriftsartikel (refereegranskat)abstract
- We studied gain and position resolution of gaseous UV-photon detectors combining single- and cascaded-glass capillary-plate multipliers and CsI photocathodes. Two modes of operation were investigated: a conventional one, where the main amplification occurs within capillary holes and a parallel-plate amplification mode, where the main amplification occurs between the capillary plate and the readout anode. Results of these studies demonstrate that in the parallel-plate amplification mode one can reach both high gains (> 10(5)) and good position resolutions (similar to 100 mum) even with a single-element multiplier. This offers a compact amplification structure, which can be used in many applications.
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| 5. |
- Iacobaeus, C., et al.
(författare)
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An X-ray scanner based on an "edge on" illuminated capillary plate combined with a gas amplification structure
- 2004
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Ingår i: 2004 IEEE Nuclear Science Symposium Conference Record. ; , s. 489-492
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Konferensbidrag (refereegranskat)abstract
- We have developed and successfully tested a prototype of a new type of high position resolution X-ray scanner. It contains a thin wall lead glass capillary plate converter of X-rays combined with a microgap parallel-plate avalanche chamber operating in various gas mixtures at 1 atm. The operation of these converters was studied in a wide range of X-ray energies (from 6 to 60 keV) at incident angles varying from 0-90°. The detection efficiency, depending on the geometry, photon's energy, incident angle and the mode of operation, was between 5-30% in a single step mode and up to 50% in a multi-layered combination. Depending on the capillary's geometry, the position resolution achieved was between 50-250 μm in digital form and was practically independent of the photon's energy or gas mixture. The usual lead glass capillary plates operated without noticeable charging up effects at counting rates of 50 Hz/mm2, and hydrogen treated capillaries up to 10 5 Hz/mm2. Finally, a prototype of the X-ray scanner based on an "edge-on" illumination capillary plate was built and tested. The developed detector open new possibilities for medical imaging, for example in mammography, portal imaging, radiography (including security devices), crystallography and many other applications.
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| 6. |
- Iacobaeus, C., et al.
(författare)
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Sporadic electron jets from cathodes - The main breakdown-triggering mechanism in gaseous detectors
- 2002
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Ingår i: IEEE Transactions on Nuclear Science. - 0018-9499 .- 1558-1578. ; 49:4, s. 1622-1628
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Tidskriftsartikel (refereegranskat)abstract
- We have demonstrated experimentally that the main breakdown-triggering mechanism in most gaseous detectors, including micropattern gaseous detectors, is sporadic electron jets from the cathode surfaces. Depending on the counting rate and applied voltages, each jet contains randomly from a few primary electrons up to 10(5), emitted in a time interval ranging between 0.1 mus to milliseconds. After the emission, these primary electrons experience a full gas multiplication in the detector and create spurious pulses. The rate of these jets increases with applied voltage and very sharply at voltages close to the breakdown limit. In our measurements, we found that these jets are responsible for the breakdown-triggering at any counting rate between 10(-2) Hz/mm(2) and 10(8) Hz/mm(2). We demonstrated on a few detectors that an optimized cathode-geometry, a high electrode surface quality, and a proper choice of the gas mixture considerably improve the performance characteristics and provide the highest possible gains. Results from this work were helpful in the construction of high-performance gaseous detectors for medical imaging applications.
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| 7. |
- Ostling, J., et al.
(författare)
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Study of hole-type gas multiplication structures for portal imaging and other high count rate applications
- 2003
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Ingår i: IEEE Transactions on Nuclear Science. - 0018-9499 .- 1558-1578. ; 50:4, s. 809-819
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Tidskriftsartikel (refereegranskat)abstract
- We performed studies in the operation of various hole-type gaseous multiplication structures (GEM, capillary plates, and others) at very high fluxes of X-rays (<60 keV-bremsstrahlung) and pulsed gamma radiation (<50 MeV-bremsstrahlung). In the case of X-rays, the counting rate was 10(5)-10(6) Hz/mm(2); in the case of gammas it reached levels of up to 10(9) Hz/mm(2) during the pulses. In most measurements, the entire area of the detector was exposed to these extremely high fluxes. Results obtained so far indicate that the GEM and the hydrogen-treated capillary plates could be successfully used in medical imaging applications.
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