THE DATA ACQUISITION SYSTEM

(Napoli contribution)

The Napoli group has given major contributions to:

Readout System

Overview

The requirements of KLOE represent a challenge fot the Data Acquisition System, since we have to
deal with data rates, (~ 10**11 events/year), considerably higher than those of typical collider experiments,
albeit a factor ten smaller than those foreseen at the LHC.

In contrast to hadron collider experiment, the large amount of data collected with KLOE are all of
physics interest, or necessary for detector calibration.

Moreover, since the major aim of KLOE is to perform CP violation studies at sensitivities of ~ 10**-4,
very stringent requirements are imposed on the DAQ system, to insure that no biases are introduced at
such levels.

The dead time is kept at low level and sis independent from event configuration: actually it is fixed to
2 x 10**-6 s (corresponding to 2% at the peak luminosity 10**33 cm-2 s-1).

Error rates, especially dependent on event configurations, which would be quite acceptable in other
situations, are minimized and procedures for insuring data integrity are incorporated in the system
design ab initio.

With bunch crossing every 2.7 ns, the DAQ system has been designed to be asynchronous with respect
to collisions' times.

Some DAQ features:

it handles ~ 23000 FEE (Front End Electronics) channels:

5000 ADC+ 5000 TDC (ecal) + 13000 TDC (Drift Ch.)

at peak luminosity 5 kHz Phi and 5 kHz background (rescaled Bhabha, machine background and cosmics):

Bandwidth to be sustained: ~ 50 Mbytes/s corresponding to ~ 5 Kbytes/event
~ 500 Tbytes/year to be stored on tapes, corresponding to 12500 DLT (40 GB/DLT)

9.5 Mbytes/s per chain has been measured. So, for a total of 10 chains, 90 Mbytes/s can be sustained.

DAQ architecture

See images: DAQ Overview Level-2 and Farm Run control system