The Data Acquisition System of the KASCADE Air Shower Experiment

Paper: 213
Session: B (poster)
Presenter: Schieler, Harald, Forschungszentrum Karlsruhe
Keywords: application programming, data acquisition systems, event building, monitoring systems, trigger algorithms

The Data Acquisition System of the KASCADE
Air Shower Experiment

presented by H. Schieler

Institutuional affiliation should be put here, together with address
Forschungszentrum Karlsruhe, P.O.B. 3640, D-76021 Karlsruhe, Germany

for the KASCADE-Collaboration

(300-500 words summary which highlights
the scope and significance of the paper
including a statement of the current status of the work)

KASCADE (KArlsruhe Shower Core and Array DEtector) is a new
extensive air shower experiment installed at the laboratory site of the
Forschungszentrum Karlsruhe, Germany.
Its objective is to study
extensive air showers induced by high energy cosmic ray particles
above 10^14 eV. The main goal is to obtain information on the chemical
composition of the primary cosmic rays.
The experimental setup consists of three main components:
a detector array for the measurement of electrons/gammas and muons
outside the shower core region,
a central detector system for the detection of high energy
hadrons and muons especially in the core
and a muon tunnel for muon tracking outside the core.
The detector array with its 252 detector stations
(1120 m^2 scintillation detectors, 1392 PM's)
is spread on a square of 200*200 m^2 and is grouped
in 16 clusters. A cluster is the basic subunit of the array and acts as
a small independent air shower array.
The central detector system consists of a segmented, 16*20 m^2
iron-TMS calorimeter with
10000 liquid ionization chambers (40000 electronic channels)
in 8 horizontal gaps,
of two shielded layers of multiwire proportional chambers
(32 MWPCs, 244 m^2) below the calorimeter,
of a trigger layer of 456 scintillation detectors in one of the gaps
and - above the calorimeter - of a top cluster of 50 scintillation detectors
for small central showers.
In the 5.4*48 m^2 muon tunnel 600 m^2 of limited
streamer tubes will be used in three layers.
Data taking with a large part of the experiment, except the muon tunnel
and parts of the calorimeter, has started at the end of 1995.

In principle KASCADE consists of 21 independent experiments,
which can be run alone or together from a central UNIX-workstation.
Signals (5 MHz, 1 Hz) from a central stabilized clock are distributed
via fiberoptic cables to all parts of the experiment to correlate the data.
In all parts of the experiment, the data acquisition and control system
is based on transputers as local intelligence. More than 170 transputers
form the data network of KASCADE, using the fast serial transputer links,
partly via fiberoptic cables.
They connect the various local, VME-based frontend electronics systems
via Ethernet gateways (B300) with the central workstation.
Different communication layers are used, based on TCP/IP sockets,
Inmos Configurer and user-specific protocols.

The local transputer memories are used for temporary storage of uncorrelated
Triggers are defined locally and distributed via fiberoptic cables
to all parts of the experiment.
Then the local memories are searched for data with corresponding timelabels.
Correlated data are transferred to the central workstation
by the transputer network.
On the workstation, eventbuilder software correlates the data from
the different experiment parts by using the time informations
before writing them to a mass storage device.
A large number of other online tasks like detector control and calibration,
track reconstruction etc. can also be performed on the transputer net.
The event display again is handled on the central workstation.
In the period from May to November 1996, more than 20 million correlated
events have been measured with a typical trigger rate of about 2 Hz.