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Register a new userElectron beam studies of light collection in a scintillating counter with embedded fibers
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The light collection of several fiber configurations embedded in a box-shaped plastic scintillating counter was studied by scanning with minimum ionizing electrons. The light was read out by silicon photomultipliers at both ends. The light yield produced by the 855-MeV beam of the Mainz Microtron showed a strong dependence on the transverse distance from the beam position to the fibers. The observations were modeled by attributing the collection of indirect light inside of the counter and of direct light reaching a fiber to the total light yield. The light collection with fibers was compared to that of a scintillating counter without fibers. These studies were carried out within the development of plastic scintillating detectors as an active veto system for the DarkMESA electron beam-dump experiment that will search for light dark matter particles in the MeV mass range.
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Lithium magnesium molybdate (Li$_2$Mg$_2$(MoO$_4$)$_3$) crystals were grown by the low-thermal-gradient Czochralski method. Luminescence properties of the material (emission spectra, thermally stimulated luminescence, dependence of intensity on temperature, phosphorescence) have been studied under X-Ray excitation in the temperature interval from 8 K to 400 K, while at the same being operated as a scintillating bolometer at 20 mK for the first time. We demonstrated that Li$_2$Mg$_2$(MoO$_4)_3$ crystals are a potentially promising detector material to search for neutrinoless double beta decay of $^{100}$Mo.
The angular coverage extension of the KLOE-2 electromagnetic calorimeter, from a polar angle of 20$^{circ}$ down to $8^{circ}$, will increase the multiphoton detection capability of the experiment enhancing the search reach for rare kaon, $eta$ and $eta$ prompt decay channels. The basic layout of the calorimeter extension consists of two small barrels of LYSO crystals readout with APD photosensors aiming to achieve a timing resolution between 300 and 500 ps for 20 MeV photons. The first test of a (5.5$times6times$13) cm$^3$ prototype for such a detector was carried out in april 2009 at the Beam Test Facility of Laboratori Nazionali di Frascati of INFN with an electron beam from 100 to 500 MeV. In the selected energy range, we measured a light yield of 500$div$800 p.e./Mev, an energy resolution which can be parametrized as $0.05 oplus 0.01/({rm E/GeV}) oplus 0.015/sqrt{rm{E/GeV}}$, a position resolution of 2.8 mm and a timing resolution of 200$div$300 ps.
We have performed a novel comparison between electron-beam polarimeters based on M{o}ller and Compton scattering. A sequence of electron-beam polarization measurements were performed at low beam currents ($<$ 5 $mu$A) during the $Q_{rm weak}$ experiment in Hall C at Jefferson Lab. These low current measurements were bracketed by the regular high current (180 $mu$A) operation of the Compton polarimeter. All measurements were found to be consistent within experimental uncertainties of 1% or less, demonstrating that electron polarization does not depend significantly on the beam current. This result lends confidence to the common practice of applying M{o}ller measurements made at low beam currents to physics experiments performed at higher beam currents. The agreement between two polarimetry techniques based on independent physical processes sets an important benchmark for future precision asymmetry measurements that require sub-1% precision in polarimetry.
A windowless hydrogen gas target of nominal thickness $10^{19}$ cm$^{-2}$ is an essential component of the DarkLight experiment, which is designed to utilize the megawatt electron beam at an Energy Recovery Linac (ERL). The design of such a target is challenging because the pressure drops by many orders of magnitude between the central, high-density section of the target and the surrounding beamline, resulting in laminar, transitional, and finally molecular flow regimes. The target system was assembled and operated at Jefferson Labs Low Energy Recirculator Facility (LERF) in 2016, and subsequently underwent several revisions and calibration tests at MIT Bates in 2017. The system at dynamic equilibrium was simulated in COMSOL to provide a better understanding of its optimal operation at other working points. We have determined that a windowless gas target with sufficiently high density for DarkLights experimental needs is feasible in an ERL environment.
In this paper we propose to perform the scintigraphy of small organ using a rotating-slit collimator and a bundle of scintillating glass fibers, put in parallel with the slit and rotating with it. An intensified CCD, coupled to the end of the fibers, acquires an integrated image of the events per each rotation angle. The final image is computed by a back-projection procedure. The advantages of this method, with respect to conventional scintigraphy, are the improvement of the detection efficiency of one-two order of magnitude without counting rate limitations, the improvement of the spatial resolution, the elimination of the parallax error and the rejection of the spurious events, without energy analysis. Simulations and first experimental results are showed.
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