41 research outputs found
A New High Energy Photon Tagger for the H1 - Detector at HERA
The H1 detector at HERA has been upgraded by the addition of a new
electromagnetic calorimeter. This is installed in the HERA tunnel close to the
electron beam line at a position 8m from the interaction point in the electron
beam direction. The new calorimeter extends the acceptance for tagged
photoproduction events to the high y range, 0.85 < y < 0.95, and thus
significantly improves the capability of H1 to study high energy gamma-p
processes. The calorimeter design, performance and first results obtained
during the 1996-1999 HERA running are described.Comment: 17 pages, 16 figure
Tagging High Energy Photons in the H1 Detector at HERA
Measures taken to extend the acceptance of the H1 detector at HERA for
photoproduction events are described. These will enable the measurement of
electrons scattered in events in the high y range 0.85 < y < 0.95 in the 1998
and 1999 HERA run period. The improvement is achieved by the installation of an
electromagnetic calorimeter, the ET8, in the HERA tunnel close to the electron
beam line 8 m downstream of the H1 interaction point in the electron direction.
The ET8 will allow the study of tagged gamma p interactions at centre-of-mass
energies significantly higher than those previously attainable. The calorimeter
design and expected performance are discussed, as are results obtained using a
prototype placed as close as possible to the position of the ET8 during the
1996 and 1997 HERA running.Comment: 13 pages, 13 figure
O ensino da tabuada no contexto das ações de estudo propostas por Davýdov e colaboradores
Particles as probes for complex plasmas in front of biased surfaces
An interesting aspect in the research of complex (dusty) plasmas is the
experimental study of the interaction of micro-particles with the surrounding
plasma for diagnostic purposes. Local electric fields can be determined from
the behaviour of particles in the plasma, e.g. particles may serve as
electrostatic probes. Since in many cases of applications in plasma technology
it is of great interest to describe the electric field conditions in front of
floating or biased surfaces, the confinement and behaviour of test particles is
studied in front of floating walls inserted into a plasma as well as in front
of additionally biased surfaces. For the latter case, the behaviour of
particles in front of an adaptive electrode, which allows for an efficient
confinement and manipulation of the grains, has been experimentally studied in
dependence on the discharge parameters and on different bias conditions of the
electrode. The effect of the partially biased surface (dc, rf) on the charged
micro-particles has been investigated by particle falling experiments. In
addition to the experiments we also investigate the particle behaviour
numerically by molecular dynamics, in combination with a fluid and
particle-in-cell description of the plasma.Comment: 39 pages, 16 figures, submitted to New J. Phy