Speaker
Dr
Benedikt Zihlmann
(Jefferson LAB)
Description
While gluonic degrees of freedom in nucleons are well established
its counter part in mesons has not been confirmed. The properties
of the of mesons are attributed to quark degrees of freedom only.
The GlueX detector facility in Hall-D at Jefferson lab in Newport News is
part of the 12GeV upgrade and dedicated to the search for gluonic degrees
of freedom in mesons by scattering high energy linearly polarized real
photons of up to 9GeV from nucleon targets.
To provide the necessary good detection coverage over 4pi, part of the detector
resides within a large solenoid magnet surrounding the target. In the bore of the
magnet a straw tube cylindrical drift chamber around the target and a series
of cathode-strip wire chambers downstream of the target are used for
particle tracking. Two electromagnetic calorimeters, one cylindrical shaped
inside the magnet (BCAL) and one downstream (FCAL) of the magnet provide the
necessary detection capabilities of photons from neutral meson decays.
The former is based on a lead scintillation fiber matrix the latter on
lead glass. The optical readout of the BCAL is based on silicon photo
multipliers that are insensitive to the high magnetic field of the solenoid.
A cylindrical plastic scintillator hodoscope around the target and two
hodoscope planes downstream of the solenoid in front of the FCAL electromagnetic
calorimeter complement the detector by providing timing information.
To handle the large data rate, custom electronics for digitization, trigger
and readout has been developed and built at Jefferson Lab. The flash analog to
digital converters run at 250MHz sampling the analog signal every 4ns and forming
energy sums at the same rate. This information is shipped via optical link at the
same 250MHz rate to a trigger decision logic. Data readout rates of up to 300MB/s
are expected to be written to disk at high luminosity running. The level 1
trigger electronics uses VXS, a VME based system with a high-speed switch-fabric
on the back plane.
Detector construction is starting now and the facility is expected to start operation
in April 2014.
Primary author
Dr
Benedikt Zihlmann
(Jefferson LAB)
