•Set-up developed for galvanic corrosion model validation under very thin electrolyte.•Polarisation data under thin electrolytes acquired for AA2024 and CFRP.•Total current modelled and validated for ...variable film thickness and concentrations.•Current density and potential distribution on the electrodes were modelled.
An experimental setup was developed for the validation of a finite element model (FEM) for simulating galvanic corrosion occurring under very thin electrolyte for bi-material combination composed of aluminium AA2024 and carbon-fibre reinforced polymer (CFRP). The validation approach is explained and the results obtained are presented. The main outcomes of the model are electric current density and potential distribution on the electrode surface. Good agreement has been obtained between measured and modelled data. Further parameter studies are discussed to show the effect of different physical properties of the electrolyte on corrosion rates and total current changes in the materials involved.
Silicon photomultipliers (SiPMs) offer high gain and fast response to light, making them interesting for fast timing applications such as time-of-flight (TOF) PET. To fully exploit the potential of ...these photosensors, dedicated preamplifiers that do not deteriorate the rise time and signal-to-noise ratio are crucial. Challenges include the high sensor capacitance, typically >300pF for a 3mm×3mm SiPM sensor, as well as oscillation issues. Here we present a preamplifier concept based on low noise, high speed transistors, designed for optimum timing performance. The input stage consists of a transimpedance common-base amplifier with a very low input impedance even at high frequencies, which assures a good linearity and avoids that the high detector capacitance affects the amplifier bandwidth. The amplifier has a fast timing output as well as a ‘slow’ energy output optimized for determining the total charge content of the pulse. The rise time of the amplifier is about 300ps. The measured coincidence resolving time (CRT) for 511keV photon pairs using the amplifiers in combination with 3mm×3mm SiPMs (Hamamatsu MPPC-S10362-33-050C) coupled to 3mm×3mm×5mm LaBr3:Ce and LYSO:Ce crystals equals 95ps FWHM and 138ps FWHM, respectively.
In a silicon photomultiplier (SiPM), also referred to as multi-pixel photon counter (MPPC), many Geiger-mode avalanche photodiodes (GM-APDs) are connected in parallel so as to combine the photon ...counting capabilities of each of these so-called microcells into a proportional light sensor. The discharge of a single microcell is relatively well understood and electronic models exist to simulate this process. In this paper we introduce an extended model that is able to simulate the simultaneous discharge of multiple cells. This model is used to predict the SiPM signal in response to fast light pulses as a function of the number of fired cells, taking into account the influence of the input impedance of the SiPM preamplifier. The model predicts that the electronic signal is not proportional to the number of fired cells if the preamplifier input impedance is not zero. This effect becomes more important for SiPMs with lower parasitic capacitance (which otherwise is a favorable property). The model is validated by comparing its predictions to experimental data obtained with two different SiPMs (Hamamatsu S10362-11-25u and Hamamatsu S10362-33-25c) illuminated with ps laser pulses. The experimental results are in good agreement with the model predictions.
The Nπ^{0}π^{0} decays of positive-parity N^{*} and Δ^{*} resonances at about 2 GeV are studied at ELSA by photoproduction of two neutral pions off protons. The data reveal clear evidence for several ...intermediate resonances: Δ(1232), N(1520)3/2^{-}, and N(1680)5/2^{+}, with spin parities J^{P}=3/2^{+}, 3/2^{-}, and 5/2^{+}. The partial wave analysis (within the Bonn-Gatchina approach) identifies N(1440)1/2^{+} and the N(ππ)_{S wave} (abbreviated as Nσ here) as further isobars and assigns the final states to the formation of nucleon and Δ resonances and to nonresonant contributions. We observe the known Δ(1232)π decays of Δ(1910)1/2^{+}, Δ(1920)3/2^{+}, Δ(1905)5/2^{+}, Δ(1950)7/2^{+}, and of the corresponding spin-parity series in the nucleon sector, N(1880)1/2^{+}, N(1900)3/2^{+}, N(2000)5/2^{+}, and N(1990)7/2^{+}. For the nucleon resonances, these decay modes are reported here for the first time. Further new decay modes proceed via N(1440)1/2^{+}π, N(1520)3/2^{-}π, N(1680)5/2^{+}π, and Nσ. The latter decay modes are observed in the decay of N^{*} resonances and at most weakly in Δ^{*} decays. It is argued that these decay modes provide evidence for a 3-quark nature of N^{*} resonances rather than a quark-diquark structure.
Multi-PMT optical module for the KM3NeT neutrino telescope Kavatsyuk, O.; Dorosti-Hasankiadeh, Q.; Löhner, H.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2012, Volume:
695
Journal Article
Peer reviewed
The future cubic kilometre scale neutrino telescope KM3NeT will employ a novel type of a Digital Optical Module (DOM), developed during the recent FP6 Design Study. A pressure-resistant glass sphere ...hosts 31 photomultiplier tubes (PMTs) of 3-in. diameter, together with all the electronics for high-voltage generation and signal readout. The optical module forms a complete stand-alone detector that is connected to the outside world via a single optical fibre and two copper conductors providing electrical power. The advantages of using multiple small PMTs in the same DOM are the higher quantum efficiency (>30% expected), smaller transit time spread, better two-photon separation capability and directional sensitivity. Moreover, a longer operating lifetime is expected than for large PMTs due to the accumulation of less charge on the anode. In addition, small PMTs are insensitive to the Earth's magnetic field and do not require μ-metal shielding. In order to maximise the detector sensitivity, each PMT will be surrounded by an expansion cone collecting photons that would normally miss the photocathode. Such an expansion cone consists of an aluminium ring filled with silicone gel. An increase in the overall sensitivity, integrated over all angles of incidence, was estimated to be about 27%. Monte-Carlo simulations have shown that a detector configuration with multi-PMT DOMs requires three times less OMs to achieve the same performance as conventional OMs hosting 10-in. PMTs. Prototype DOMs are currently being built by the KM3NeT consortium.
Neutrino-induced showers in the ANTARES deep-sea telescope Dorosti Hasankiadeh, Q.; Löhner, H.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2013, Volume:
725
Journal Article
Peer reviewed
Reconstruction of neutrino-induced showers, initiated by neutral-current interactions, can extend the sensitivity of the ANTARES detector to all neutrino flavors. A major challenge in reconstructing ...showers is their selection from an overwhelming background of down-going atmospheric muons. We have developed a shower selection strategy in order to select up-going showers with high efficiency and purity. We have tuned the selection strategy on Monte-Carlo simulations containing the proper amount of background and atmospheric neutrino-induced showers. The obtained results indicate an efficiency of 21% with a purity better than 90% for the shower selection. We applied the selection strategy to ANTARES experimental data and observed a satisfactory performance of the discriminating variables.
We have investigated the timing performance of Hamamatsu Multi-Pixel Photon Counter (MPPC) photosensors in light of their use in time-of-flight (TOF) positron emission tomography detectors. ...Measurements using picosecond laser pulses show a single photo-electron root-mean-square (RMS) timing resolution down to about 100
ps. In coincidences of 511
keV photons detected with an LYSO crystal coupled to a MPPC and a BaF
2 detector, an optimum FWHM timing resolution of 600
ps was obtained with leading edge time pickoff at the 1–1.5 photo-electron level. By optimizing the LYSO/MPPC coupling, this can be improved by a factor of 2. We further conclude that the use of stored digitized pulses allows great flexibility and efficiency in developing data analysis algorithms.
Current technology and understanding of neutrino properties allow the study of the Universe in the “light” of neutrinos. The goal is to unravel the acceleration mechanism of energetic cosmic ...particles and to search for neutrino point sources and dark matter. An efficient detection of high-energy (1–1000
TeV) neutrinos originating from galactic and extragalactic sources requires a deep-sea telescope of
km
3
size exploiting the measurement of Cherenkov light for accurate determination of light arrival times and amplitudes, to allow the reconstruction of neutrino direction and energy. Based on experience with pilot projects in the Mediterranean Sea, the detector concept has been developed. Different geometries, optical sensors, readout electronics, options for long distance data transfer, and deployment issues have been evaluated.
The multi-PMT optical module for KM3NeT Löhner, H.; Dorosti-Hasankiadeh, Q.; Heine, E. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2013, Volume:
718
Journal Article
Peer reviewed
In the future neutrino telescope KM3NeT a novel type of optical module (OM) will be employed to optimize the sensitivity to Cherenkov photons and maximize the environmental background suppression. ...The multi-PMT OM, a pressure-resistant glass sphere containing 31 photomultiplier tubes (PMTs) of 3-in. diameter, has been developed and prototyped including electronics for high-voltage generation, signal digitization and optical signal transmission. Monte-Carlo simulations show that a multi-PMT OM configuration requires three times less OMs to achieve the same performance as conventional OMs hosting 10-in. PMTs.
A simple, efficient, and robust feature-extraction algorithm, developed for the digital front-end electronics of the electromagnetic calorimeter of the PANDA spectrometer at FAIR, Darmstadt, is ...implemented in VHDL for a commercial 16 bit 100
MHz sampling ADC. The source-code is available as an open-source project and is adaptable for other projects and sampling ADCs. Best performance with different types of signal sources can be achieved through flexible parameter selection. The on-line data-processing in FPGA enables to construct an almost dead-time free data acquisition system which is successfully evaluated as a first step towards building a complete trigger-less readout chain. Prototype setups are studied to determine the dead-time of the implemented algorithm, the rate of false triggering, timing performance, and event correlations.
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