In preterm infants, there is a risk of long-term cognitive, motor and behavioral impairments due to hemorrhagic and/or ischemic lesions. If detected early, lesions can be prevented. A bedside imaging ...modality, capable of early detection of both disorders, is necessary. We present the state of development of a tomographic imager (named Pioneer), that will be capable of determining the oxygenation of the preterm-infant brain with high spatial resolution. Pioneer is a time-resolved near-infrared optical tomography (TR NIROT) instrument. It employs multiple wavelength laser light in short pulses on 11 distinct locations and measures the re-emerging light in a contactless fashion by means of a time-correlated single-photon counting (TCSPC) camera (named Piccolo) covering ~4.9 cm
with 300 detectors. Timing response of the entire system is 116 ps. An in-house designed biocompatible source ring ensures fixed relative positions of sources and detectors and provides a secure interface between the patient and the probe. At the present state, the NIROT Pioneer system successfully detected a 6x6x50 mm
inclusion 3 cm deep inside a phantom. These results confirm that the Pioneer imager is working as expected and is on a solid path towards full 3D tissue oxygenation imaging.
Radiative corrections to elastic scattering represent an important part of the interpretation of electron-induced nuclear reactions at small energy transfers, where they represent a dominant part of ...the background. Here we present and validate a new event generator for simulating QED radiative processes in electron-carbon scattering that exactly calculates the coherent sum of the Bethe-Heitler amplitudes for the leading diagrams. We demonstrate that the generator describes the shape of the radiative tail of an elastic peak with a precision better than
10
%
over the whole energy range of the scattered electrons and can thus be reliably employed in the analyses of electron scattering experiments for more precise extraction of inelastic cross-sections.
Measured response functions and low photon yield spectra of silicon photomultipliers (SiPM) were compared to multi-photoelectron pulse-height distributions generated by a Monte Carlo model. ...Characteristic parameters for SiPM were derived. The devices were irradiated with 14
MeV electrons at the Mainz microtron MAMI. It is shown that the first noticeable damage consists of an increase in the rate of dark pulses and the loss of uniformity in the pixel gains. Higher radiation doses also reduced the photon detection efficiency. The results are especially relevant for applications of SiPM in fibre detectors at high luminosity experiments.
A tracking detector based on 1.5
m long scintillating fibers is being developed for the electron arm of the KAOS spectrometer at the Mainz Microtron MAMI. Measurements on light attenuation, particle ...detection efficiencies and accidental coincidence rates with a prototype set-up using
2
×
2
mm
2
fibers read out by silicon photomultipliers (SiPM) are presented. The highest efficiency at the lowest accidental coincidence rate was reached for high trigger thresholds at the largest SiPM bias voltages. The influence of signal attenuation and dispersion on detection efficiencies is discussed. The results are in good agreement with a Monte Carlo model that was used to predict detector characteristics for different fiber geometries.
Present and future research into the electroproduction of strangeness plays an important role at Mainz Microtron MAMI. With the Kaos spectrometer for kaon detection operated in the multi-spectrometer ...facility first cross section measurements of the exclusive p(e,e′K+)Λ,Σ0 reactions at low-momentum transfers have been performed. These measurements have clearly discriminated between effective Lagrangian models for photo- and electroproduction of strangeness. Recently, the Kaos spectrometer was upgraded to a double-arm spectrometer for the measurement of elementary cross sections at very forward scattering angles and for the missing mass spectroscopy of hypernuclear states. In parallel, pioneering experiments on decay-pion spectroscopy of electroproduced hypernuclei were carried out at MAMI. Future experiments will on the one side address the cross section of the elementary process with polarized beam and on the other side continue the hypernuclear spectroscopy with different light nuclear targets.
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