Hallo,

Fuer unseren Uebersichtsvortrag in Trieste habe ich als Konzept
die Langversion unten geschrieben, moechte das aber erstmal intern
herumschicken, bevor ich ein Abstract Version zwei an
Silvia Dalla Torre <Silvia.DallaTorre@ts.infn.it> schicke.

Persoenlich kann ich mir auch eine Kurzversion vorstellen,
im wesentlichen an den Enden der Absaetze 2,4,5 gekuerzt,
jene Infos koennten ja dann in den Poster-abstracts auftauchen.
Meinungen?

Gruss

Klaus

> "The DIRC projects of the PANDA experiment at FAIR"

For the charged particle identification of the PANDA experiment at FAIR,
one foresees three imaging Cherenkov detectors:
two DIRC detectors in the target spectrometer part
and one RICH detector in the forward spectrometer part.
This talk will give an overview of the DIRC designs.

The Barrel region requirements of a thin detector
operating in a strong magnetic field can be met
by a Cherenkov detector using a DIRC of two-dimensional design
where the light is transported inside bars of rectangular cross section.
Combining the photon time of arrival with their spatial image
determines not only the particles velocity,
but also the photon wavelengths, allowing some dispersion 
correction at the lower and upper detection threshold.

In the Endcap region a one-dimensional DIRC transports photons
to the edge of a circular discs. For the readout we investigate
two different options.

In the focussing lightguide dispersion-correcting technique
the photons enter into one of about hundred optical elements
on the rim where the two-fold angle ambiguity is lifted,
the chromatic dispersion corrected
and the photon focussed onto a readout plane.
While the optical element entered determines the $\phi$ coordinate,
the focussing lightguide part provides a one-dimensional
spatial coordinate yielding the $\theta$ coordinate.

A time-of-propagation (TOP) technique including a chromatic correction
is based on dichroic mirrors which split the spectral range of the
Cherenkov photons. This combination of technologies allows both
to avoid the decrease of resolution usually connected with dispersion
and to provide different light path lengths inside the radiator,
thus leading to larger time differences in the TOP measurement
which makes it less challenging to discriminate different
particle species at higher momenta. MCP PMTs will be used
to construct a very compact photon readout system which
is operational within the field of the magnet yoke region.

The expected radiation field and cumulative doses severely limiting
the choice of optical materials, the wavelength dependence of
the Cherenkov angle to be taken into account, space restrictions
calling for compact design and photon detector placement in a
significant magnetic field; such often contradictory requirements
make ongoing R\&D, optimisations and some compromises necessary.