Table of contents

The precision measurement of the weak light pulse arrival time seems to be really important for various time-of-flight applications within the high energy physics and the medical imaging areas. Photon Detection Efficiency (PDE) and single photon Transit Time Spread (TTS) are considered to be the key characteristics for time resolution responsible photodetectors within such applications. The measurements of PDE and TTS are rather independent and require different techniques and setups. We consider the probability of single photon detection as a defective cumulative distribution function (CDF) of the single photon transit time, so a number of analytical expressions of how it can be reconstructed from the multi-photon TTS histogram affected by the dark counts have been found. It has allowed us to suggest a robust quantitative method of a single photon detection characterization provided with both single photon TTS and PDE. The method is considered to be especially relevant and useful for the Solid State Photomultipliers (SSPM) with high dark count rate.

The image forming process in a CdTe detector is both a function of the X-ray interaction in the material, including scattering and fluorescence, and the charge transport in the material [2–4]. The response to individual photons has been investigated using a CdTe detector with a pixel size of 110μm, bonded to a TIMEPIX [5] readout chip operating in time over threshold mode. The device has been illuminated with mono-energetic photons generated by fluorescence in different metals and by gamma emission from ²⁴¹Am and ¹³⁷Cs. Each interaction will result in charge distributed in a cluster of pixels where the total charge in the cluster should sum up to the initial photon energy. By looking at the individual clusters the response from shared photons as well as fluorescence photons can be identified and separated. By using energies below and above the K-edges of Cd and Te the contribution from fluorescence can be further isolated. The response is analyzed to investigate the effects of both charge diffusion and fluorescence on the spectral response in the detector.

The spectral and temporal light emission properties of liquid argon have been studied in the context of its use in large liquid rare-gas detectors for detecting Dark Matter particles in astronomy. A table-top setup has been developed. Continuous and pulsed low energy electron beam excitation is used to stimulate light emission. A spectral range from 110 to 1000 nm in wavelength is covered by the detection system with a time resolution on the order of 1 ns.

The ALICE experiment is shown to be well suited for studies of exclusive final states from central diffractive reactions. The gluon-rich environment of the central system allows detailed QCD studies and searches for exotic meson states, such as glueballs, hybrids and new charmonium-like states. It would also provide a good testing ground for detailed studies of heavy quarkonia. Due to its central barrel performance, ALICE can accurately measure the low-mass central systems with good purity. The efficiency of the Forward Multiplicity Detector (FMD) and the Forward Shower Counter (FSC) system for detecting rapidity gaps is shown to be adequate for the proposed studies. With this detector arrangement, valuable new data can be obtained by tagging central diffractive processes.

An instrument has been developed to measure X-ray bang-time for inertial confinement fusion capsules; the time interval between the start of the laser pulse and peak X-ray emission from the fuel core. The instrument comprises chemical vapor deposited polycrystalline diamond photoconductive X-ray detectors with highly ordered pyrolytic graphite X-ray monochromator crystals at the input. Capsule bang-time can be measured in the presence of relatively high thermal and hard X-ray background components due to the selective band pass of the crystals combined with direct and indirect X-ray shielding of the detector elements. A five channel system is being commissioned at the National Ignition Facility at Lawrence Livermore National Laboratory for implosion optimization measurements as part of the National Ignition Campaign. Characteristics of the instrument have been measured demonstrating that X-ray bang-time can be measured with ±30 ps precision, characterizing the soft X-ray drive to +/- 1 eV or 1.5%.

The development of a mm-spatial-resolution, resonant-response detector based on a micrometric glass capillary array filled with liquid scintillator is described. This detector was developed for Gamma Resonance Absorption (GRA) in ¹⁴N. GRA is an automatic-decision radiographic screening technique that combines high radiation penetration (the probe is a 9.17 MeV γ-ray) with very good sensitivity and specificity to nitrogenous explosives. Detailed simulation of the detector response to electrons and protons generated by the 9.17 MeV γ-rays was followed by a proof-of-principle experiment, using a mixed γ-ray and neutron source. Towards this, a prototype capillary detector was assembled, including the associated filling and readout systems. Simulations and experimental results indeed show that proton tracks are distinguishable from electron tracks at relevant energies, based on a criterion that combines track length and light intensity per unit length.

Large-mass bolometers are used in particle physics experiments to search for rare processes. The energy threshold of such detectors plays a critical role in their capability to search for dark matter interactions and rare nuclear decays. We have developed a trigger and a pulse shape algorithm based on the matched filter technique which, when applied to data from test bolometers of the Cuore experiment, lowered the energy threshold from tens of keV to the few keV region. The detection efficiency is in excess of 80%, and nearly all nonphysical pulses are rejected.

The operational characteristics of a Micromegas operating in pure xenon at the pressure range of 1 to 10 bar are investigated. The maximum charge gain achieved in each pressure is approximately constant, around 4 × 10², for xenon pressures up to 5 bar and decreasing slowly above this pressure down to values somewhat above 10² at 10 bar. The MM presents the highest gains for xenon pressures above 4 bar, when compared to other micropattern gaseous multipliers. The lowest energy resolution obtained for X-rays of 22.1 keV exhibits a steady increase with pressure, from 13% at 1 bar to about 32% at 10 bar. The effective scintillation yield, defined as the number of photons exiting through the MM mesh holes per primary electron produced in the conversion region was calculated. This yield is about 2 × 10² photons per primary electron at 1 bar, increasing to about 6 × 10² at 5 bar and, then, decreasing again to 2 × 10² at 10 bar. The readout of this scintillation by a suitable photosensor will result in higher gains but with increased statistical fluctuations.

The combination of γ-ray spectroscopy and charged-particle spectroscopy is a powerful tool for the study of nuclear reactions with beams of nuclei far from stability. This paper presents a new silicon detector array, SHARC, the Silicon Highly-segmented Array for Reactions and Coulex. The array is used at the radioactive-ion-beam facility at TRIUMF (Canada), in conjunction with the TIGRESS γ-ray spectrometer, and is built from custom Si-strip detectors utilising a fully digital readout. SHARC has more than 50% efficiency, approximately 1000-strip segmentation, angular resolutions of Δθ ≈ 1.3 deg and Δϕ ≈ 3.5 deg, 25–30 keV energy resolution, and thresholds of 200 keV for up to 25 MeV particles. SHARC is now complete, and the experimental program in nuclear astrophysics and nuclear structure has commenced.

A three-element einzel lens is a standard ion optics used to focus a low energy ion beam. In certain applications like injection of a low energy ion beam into a strong magnetic field of a Penning trap, it is necessary to combine a lens with a small angle beam steerer. The middle electrode is often slit in parallel or diagonal in order to combine the steering field with the focusing field. Here we study and analyze the performances of these two designs of same dimension and show that the diagonal-slit configuration is the better choice to achieve comparatively larger steering and focusing within acceptable aberration.

In this work we present an elegant solution for a scintillation counter to be integrated into a cryogenic system. Its distinguishing feature is the absence of a continuous light guide coupling the scintillation and the photodetector parts, operating at cryogenic and room temperatures respectively. The prototype detector consists of a plastic scintillator with glued-in wavelength-shifting fiber located inside a cryostat, a Geiger-mode Avalanche Photodiode (G-APD) outside the cryostat, and a lens system guiding the scintillation light re-emitted by the fiber to the G-APD through optical windows in the cryostat shields. With a 0.8 mm diameter multiclad fiber and a 1 mm active area G-APD the coupling efficiency of the ``lens light guide" is about 50 %. A reliable performance of the detector down to 3 K is demonstrated.

The International Linear Collider (ILC) and other proposed high energy e⁺e⁻ machines aim to measure with unprecedented precision Standard Model quantities and new, not yet discovered phenomena. One of the main requirements for achieving this goal is a measurement of the incident beam energy with an uncertainty close to 10⁻⁴. This article presents the analysis of data from a prototype energy spectrometer commissioned in 2006-2007 in SLAC's End Station A beamline. The prototype was a 4-magnet chicane equipped with beam position monitors measuring small changes of the beam orbit through the chicane at different beam energies. A single bunch energy resolution close to 5·10⁻⁴ was measured, which is satisfactory for most scenarios. We also report on the operational experience with the chicane-based spectrometer and suggest ways of improving its performance.

A new design of highly granular hadronic calorimeter using Glass Resistive Plate Chambers (GRPCs) with embedded electronics has been proposed for the future International Linear Collider (ILC) experiments. It features a 2-bit threshold semi-digital read-out. Several GRPC prototypes with their electronics have been successfully built and tested in pion beams. The design of these detectors is presented along with the test results on efficiency, pad multiplicity, stability and reproducibility.

High Level Synthesis takes an abstract behavioural or algorithmic description of a digital system and creates a register transfer level structure that realises the described behaviour. Various methodologies have been developed to perform such synthesis tasks. This paper presents the different HLS concepts used in the current leading tools. It makes a comparison between the different approaches and highlights their advantages and limitations. We also present a high level synthesis example.

CMOS Monolithic Active Pixel Sensors (MAPS) demonstrate excellent performances in the field of charged particle tracking. A single point resolution of 1–2 μm and a detection efficiency close to 100% were routinely observed with various MAPS designs featuring up to 10⁶ pixels on active areas as large as 4 cm²[1]. Those features make MAPS an interesting technology for vertex detectors in particle and heavy ion physics. In order to adapt the sensors to the high particle fluxes expected in this application, we designed a sensor with fast column parallel readout and partially depleted active volume. The latter feature was expected to increase the tolerance of the sensors to non-ionizing radiation by one order of magnitude with respect to the standard technology. This paper discusses the novel sensor and presents the results on its radiation tolerance.

The goal of the LHCb readout upgrade is to accelerate the DAQ to 40 MHz. Such a DAQ system will certainly employ 10 Gigabit or similar technologies and might also need new networking protocols such as a customized, light-weight TCP or more specialized protocols. A test module is being implemented to be integrated in the existing LHCb infrastructure. It is a multiple 10-Gigabit traffic generator, driven by a Stratix IV FPGA, and flexible enough to generate LHCb's raw data packets. Traffic data are either internally generated or read from external storage via the network. We have implemented a light-weight industry standard protocol ATA over Ethernet (AoE) and we present an outlook of using a file-system on these network-exported disk-drivers.

In the present work a new system for Quantum Computed Tomography was developed and tested, envisaging its application to small animals and mammography imaging. It consists of a Micro-Patterned Gas Detector based on the Micro-Hole and Strip Plate, operating in single-photon counting mode. The Micro-Hole and Strip Plate allows the storage of the position of interaction and the energy information of each single X-ray photon. With this information it is possible to select the energy range to reconstruct the images of cross sections, enabling the enhancement of different structures according to their attenuation coeficients. It is also possible to use the energy information to weight each photon in the sinogram construction. In the present work we consider three types of weighting factors giving rise to three different types of images, namely Integrating, Counting and Energy Weighting Technique (EWT). For each CT acquisition the system allows us to construct any of these types of images without the need for extra measurements. Some features of the CT image improve with the application of the Energy Weighting Technique, namely the Signal-to-Noise Ratio (SNR), the image Contrast, and the Contrast-to-Noise Ratio (CNR). The maximum contrast enhancement was about 23%, the maximum SNR improvement was about 22% and the maximum CNR improvement was about 31% between integrating and EWT images.

X-ray imaging systems such as photon counting pixel detectors have a limited spatial resolution of the pixels, based on the complexity and processing technology of the readout electronics. For X-ray imaging situations where the features of interest are smaller than the imaging system pixel size, and the pixel size cannot be made smaller in the hardware, alternative means of resolution enhancement require to be considered. Oversampling with the usage of multiple displaced images, where the pixels of all images are mapped to a final resolution enhanced image, has proven a viable method of reaching a sub-pixel resolution exceeding the original resolution. The effectiveness of the oversampling method declines with the number of images taken, the sub-pixel resolution increases, but relative to a real reduction of imaging pixel sizes yielding a full resolution image, the perceived resolution from the sub-pixel oversampled image is lower. This is because the oversampling method introduces blurring noise into the mapped final images, and the blurring relative to full resolution images increases with the oversampling factor. One way of increasing the performance of the oversampling method is by sharpening the images in post processing. This paper focus on characterizing the performance increase of the oversampling method after the use of some suitable post processing filters, for digital X-ray images specifically. The results show that spatial domain filters and frequency domain filters of the same type yield indistinguishable results, which is to be expected. The results also show that the effectiveness of applying sharpening filters to oversampled multiple images increase with the number of images used (oversampling factor), leaving 60–80% of the original blurring noise after filtering a 6 × 6 mapped image (36 images taken), where the percentage is depending on the type of filter. This means that the effectiveness of the oversampling itself increase by using sharpening filters, and more images taken can be considered worth the effort.

An experimental set-up for studying microwave non-thermal effects has been reported by Huang et al. in 2009. This paper proposes a modified experimental set-up and reports the results of multi-physics calculations comparing the proposed experimental set-up with one similar to the original one. The calculated results show that the electric field intensity in sodium chloride aqueous solution for the proposed set-up is more uniform and at least one order of magnitude higher than one similar to the original one. The electric field intensity around the electrodes for the proposed set-up is smaller than the one similar to the original one, which indicates that the electrodes in the proposed set-up cause less unnecessary microwave energy coupling. Further more, the influence of the inlet speed on the rise in temperature of the solution for the two set-ups is also studied, suggesting that high rise in temperature can be reduced by increasing the inlet speed.

In recent times, digital X-ray detectors have been actively applied to the medical field; for example, digital radiography offers the potential of improved image quality and provides opportunities for advances in medical image management, computer-aided diagnosis and teleradiology. In this study, two candidate materials (HgI₂ and PbI₂) have been employed to study the influence of the dielectric structure on the performance of fabricated X-ray photoconducting films. Parylene C with high permittivity was deposited as a dielectric layer using a parylene deposition system (PDS 2060). The structural and morphological properties of the samples were evaluated field emission scanning electron microscopy and X-ray diffraction. Further, to investigate improvements in the electrical characteristics, a dark current in the dark room and sensitivity to X-ray exposure in the energy range of general radiography diagnosis were measured across the range of the operating voltage. The electric signals varied with the dielectric layer structure of the X-ray films. The PbI₂ film with a bottom dielectric layer showed optimized electric properties. On the other hand, in the case of HgI₂, the film with a top dielectric layer showed superior electric characteristics. Further, although the sensitivity of the film decreased, the total electrical efficiency of the film improved as a result of the decrease in dark current. When a dielectric layer is deposited on a photoconductor, the properties of the photoconductor, such as hole-electron mobility, should be considered to improve the image quality in digital medical imaging application. In this study, we have thus demonstrated that the use of dielectric layer structures improves the performance of photoconductors