[en] The aim of the work presented here was to measure X-ray spectra with a pixelated detector. Due to effects in the sensor the spectrum cannot be measured directly and has to be calculated by a deconvolution of the measured data. In the scope of this work the deconvolution of the measured spectra could be enhanced considerably by - amongst other things - the introduction of the Bayesian deconvolution method. Those improvements opened the possibilities for further measurements. For the measurements the detectors of the Medipix family have been used. They are nowadays used for a wide range of applications and scientific research. Their main advantage is the very high position resolution gained by a pixel pitch of 55 μm and a high number of 65536 pixels. The Timepix detector has, in particular, two special possibilities of measurement: the ToA mode and the ToT mode. In ToA mode the arrival time of an impinging photon is measured and in ToT mode the amount of deposited charge is measured. The most common method of operation is counting the number of impinging photons that release a charge higher than a preset threshold in each pixel. As this released charge is proportional to the energy deposition of the impinging photon, one can perform energy-sensitive measurements. To perform the deconvolution of the measured energy distribution there is a need of an energy response matrix describing the detector response on radiation. For some detectors it is possible to obtain an analytic model of the response functions. Due to the high discrepancy between the impinging spectrum and the measured spectrum in case of detectors of the Medipix family, there is so far no analytic model. Thus, the detector response has to be simulated. As I could improve the precision of the measurement quite extensively, I also intended to tune the simulation with more accurate and appropriate models to gain the same level of accuracy. The results of measurement and simulation have then been compared and show a good agreement. Up to now the measurements of impinging spectra with a Timepix detector have been performed in radiation fields with a relatively high fluence. To cope with the requirement of measuring in radiation fields with a low fluence, there had to be changes in the method of analysis compared to those performed formerly. An important improvement in this context was the employment of the Bayesian deconvolution method. The spectra reconstructed with this method were then compared to the results of two different and established detection systems. Firstly, the shape of the deconvolved spectrum was compared to the one measured with a hpGe detector. Secondly, the calculated value of the kerma rate was compared to the one measured with an ionization chamber. This gave an estimate on the correctness of the absolute number of photons. Both comparisons have shown a good agreement and thus I was able to validate that the method delivers precise results. Compared to the formerly used spectrum-stripping method the Bayesian deconvolution turned out to be very stable and reliable. This robustness of the deconvolution method and the development of a pixel-by-pixel energy calibration were the keys towards position-resolved spectrometry. With such a precise energy calibration the energy resolution was enhanced by up to 45%. This improved accuracy in the measurement has been very demanding on the improvements of the simulation of the response matrix needed for deconvolution. Both this enhanced simulation and a pixel-by-pixel calibrated detector opened the possibility of measuring the anode heel effect. Not only the relative angular dependency of the spectrum emitted but also the change in the absolute photon fluence were measured. Furthermore, it is possible to even use small ROIs down to 4x4 pixels to evaluate a spectrum. This was then applied for the spectrometry of small focal spots of a miniature X-ray source used in therapeutics. Furthermore, the robustness and the stability of the applied Bayesian deconvolution method enabled the possibility of performing time-resolved spectrometric measurements. By measuring in ToA mode and in parallel performing a THL scan, it is possible to gain information on both energy and time. This method was then tested for a conventional X-ray tube for measuring the time dependence of the spectrum emitted during the switching-on process of the radiation. As expected, the results showed a relatively long time-dependent change of the spectrum. This method was then applied for proving that a newly developed X-ray source shows a spectral change of the spectrum emitted on a very low time scale only. As this time dependence is much shorter compared to the total pulse duration of the radiation, it is negligible. This result guarantees that both pulse duration and energy can be adjusted independently. This enables further investigations with this new X-ray tube in the field of pulsed radiation and its use for e.g. type tests.

[en] As production target for Neutrino Factories, free mercury jets with high axial velocity of about 20 m/s are being studied. For the CERN-Neutrino-Factory proposal with a 4 MW beam power, but with a relatively large beam size at 2.2 GeV/c and pulsed at 50 Hz, maximum energy deposition densities of below 20 J/g and average power densities of about 1 kW/g are expected in the target. Therefore, a study has been made which discusses the feasibility and limits of a stationary target. It is proposed to use densely packed solid spheres of heavy material and with diameters in the millimeter range. These spheres are confined inside a Titanium container and cooled by an efficient water circuit or possibly by He-gas. Dynamic response, as pressure pulses and vibrations are greatly reduced in the small target granules due to relatively long beam bursts, each with a duration of 3.3 μs. The encouraging results achieved in this assessment justify to pursue further experimental tests, in particular of the cooling of the target, its lifetime under repetitive thermal cycles (4.3 Mio/day) and of radiation damage, to validate this proposal. It is expected that the lifetime of this target will be adequate for the operation of the CERN-Neutrino-Factory, at least over its initial phase below 4 MW beam power

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[en] A Talbot-Lau interferometer is a compact laboratory setup for phase-contrast imaging that can be used with a usual polychromatic X-ray source. Operating this setup with a broad spectrum is followed by a cutback in performance in comparison to monochromatic illumination. By evaluating the interferometer's complex energy-dependent response and using the information obtained by an energy-resolving detector, the performance might be increased again. Therefore, the energetic behaviour of the dark-field image was investigated. In simulations the energy dependence of the dark-field signal generated by small glass spheres was calculated and in order to verify these simulations, measurements using a Timepix detector were done. The results of the measurements show a good agreement with the simulations. In this contribution these results are presented, and the behaviour of the dark-field contrast is discussed.

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[en] As recently shown, it is possible to use pixelated semiconductor detectors such as Medipix2 for measuring the impinging spectra. If all interaction processes in the sensor like photoeffect, compton scattering and fluorescence excitation are implemented correctly in a Monte-Carlo-Simulation, the impinging spectrum can be computed by deconvolution of the measured energy deposition spectrum with monoenergetic response functions. In this work we present an improved reconstruction algorithm to extend the working conditions for low flux fields. For the measurements a Medipix2 was used. It consists of an ASIC which has 256 x 256 pixel cells with 55 μm pitch. As sensor we used a silicon layer with a thickness of 300 μm bumpbonded to the ASIC. In the analogue part of each pixel a discriminator with one energy threshold is present. This means only photons with an energy deposition in the sensor that is higher than the threshold are counted. By increasing this threshold gradually the whole deposited spectra can be scanned. In opposite to former studies such a ''threshold scan'' is now used directly for the deconvolution without the intermediate step of the derivation. This has the advantage of much lower relative errors and therefore has the potential to measure spectra with low statistics.

[en] Conducting pulsed target scheme has been studied as an alternative targetry solution used for a dedicated high-intense and bright muon source (PRISM). We made a conceptual design and have developed a pulse power supply and a mercury loop to be used for the proof-of-principle test

[en] A non-conventional positron source using the intense y radiation from an axially oriented monocrystal which materializes into e⁺e^- pairs in a granular amorphous converter is described. The enhancement of photon radiation by multi-GeV electrons crossing a tungsten crystal along its <111> axis is reported. The resulting enhancement of pair production in an amorphous converter placed 2 meters downstream, is also re- ported. Sweeping off the charged particles from the crystal by a bending magnet upstream of the converter allows a significant reduction of the deposited energy density. Substituting a granular target made of small spheres for the usual compact one, makes the energy dissipation easier. The deposited energy and correspond- ing heating are analyzed and solutions for cooling are proposed. The configurations studied here for this kind of positron. source allow its consideration for unpolarized positions for the ILC. (authors)

[en] A conceptual design of the targetry for the high intensity slow muon source is presented. Based on simulation studies, critical issues are discussed and a baseline design is determined. We have started R and D works on superconducting solenoids as well as conducting targets, which is an alternative option