Undulator-based production of polarized positrons Alexander, G.; Barley, J.; Batygin, Y. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2009, Letnik:
610, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Full exploitation of the physics potential of a future International Linear Collider will require the use of polarized electron and positron beams. Experiment E166 at the Stanford Linear Accelerator ...Center (SLAC) has demonstrated a scheme in which an electron beam passes through a helical undulator to generate photons (whose first-harmonic spectrum extended to 7.9
MeV) with circular polarization, which are then converted in a thin target to generate longitudinally polarized positrons and electrons. The experiment was carried out with a 1-m-long, 400-period, pulsed helical undulator in the Final Focus Test Beam (FFTB) operated at 46.6
GeV. Measurements of the positron polarization have been performed at five positron energies from 4.5 to 7.5
MeV. In addition, the electron polarization has been determined at 6.7
MeV, and the effect of operating the undulator with a ferrofluid was also investigated. To compare the measurements with expectations, detailed simulations were made with an upgraded version of G
eant4
that includes the dominant polarization-dependent interactions of electrons, positrons, and photons with matter. The measurements agree with calculations, corresponding to 80% polarization for positrons near 6
MeV and 90% for electrons near 7
MeV.
Application of artificial neural networks in particle physics Kolanoski, Hermann
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/1995, Letnik:
367, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The application of artificial neural networks in particle physics is reviewed. The use of feed-forward nets is most common for event classification and function approximation. This network type is ...best suited for a hardware implementation and special VLSI chips are available which are used in fast trigger processors. Also discussed are fully connected networks of the Hopfield type for pattern recognition in tracking detectors.
We report spectral and imaging performance of a pixelated CdZnTe detector custom designed for the \emph{MeVCube} project: a small Compton telescope on a CubeSat platform. \emph{MeVCube} is expected ...to cover the energy range between \(200\;\mathrm{keV}\) and \(4\;\mathrm{MeV}\), with performance comparable to the last generation of larger satellites. In order to achieve this goal, an energy resolution of few percent in full width at half maximum (FWHM) and a \(3\)-D spatial resolution of few millimeters for the individual detectors are needed. The severe power constraints present in small satellites require very low power read-out electronics for the detector. Our read-out is based on the VATA450.3 ASIC developed by \emph{Ideas}, with a power consumption of only \(0.25\;\mathrm{mW/channel}\), which exhibits good performance in terms of dynamic range, noise and linearity. A \(2.0\;\mathrm{cm} \times 2.0\;\mathrm{cm} \times 1.5\;\mathrm{cm}\) CdZnTe detector, with a custom \(8 \times 8\) pixel anode structure read-out by a VATA450.3 ASIC, has been tested. A preliminary read-out system for the cathode, based on a discrete \emph{Amptek} A250F charge sensitive pre-amplifier and a DRS4 ASIC, has been implemented. An energy resolution around \(3\%\) FWHM has been measured at a gamma energy of \(662\;\mathrm{keV}\); at \(200\;\mathrm{keV}\) the average energy resolution is \(6.5\%\), decreasing to \(\lesssim 2\%\) at energies above \(1\;\mathrm{MeV}\). A \(3\)-D spatial resolution of \(\approx 2\,\mathrm{mm}\) is achieved.
Parton densities in the photon Kolanoski, Hermann
Nuclear physics. Section B, Proceedings supplement,
03/1995, Letnik:
39, Številka:
2
Journal Article
Recenzirano
The parton densities in the photon have been derived from measurements of the photon structure function and of jet production in two-photon and photoproduction processes. Recent analyses by the H1 ...and ZEUS collaborations show that hard photoproduction processes at HERA allow to determine the gluon density down to
x values of 10
−2. For a discrimination of different models the systematic uncertainties in these analyses have still to be reduced.
The IceCube Neutrino Observatory with its 1-km^3 in-ice detector and the 1-km^2 surface detector (IceTop) constitutes a three-dimensional cosmic ray detector well suited for general cosmic ray ...physics. Various measurements of cosmic ray properties, such as energy spectra, mass composition and anisotropies, have been obtained from analyses of air showers at the surface and/or atmospheric muons in the ice.
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