Speaker
Description
Summary
The Level-0 LKr electromagnetic calorimeter trigger (LKrL0),
identifies electromagnetic clusters in the calorimeter and prepares a
time-ordered list of reconstructed clusters together with the arrival
time, position, and energy measurements of each cluster. The trigger
is a three-layer parallel system, composed of 28 front-end and 8
concentrator boards based on the 9U TEL62 boards and equipped with
custom dedicated mezzanines called TELDES, LKrL0 TX and LKrL0 RX. The
trigger algorithm is based on energy deposits in 864 digital sums
(TSL) of 16 calorimeter cells each, which are digitized and
transmitted by the Calorimeter REAdout Modules (CREAMs). The
electromagnetic cluster search is executed in two steps with a two-dimensional algorithms (1D + 1D algorithm). In the first step,
each front-end board receives data from a vertical slice of the
calorimeter (that contains up to 32 TSL) and looks for peaks in the
energy deposit in the vertical slice. In the second step, the
concentrator boards receive trigger data from up to eight front-end
boards and combine the peaks detected by different front-end boards
into a single cluster.
The TELDES mezzanine receives and deserializes digitized data (16 bit
@ 40 MHz over 15 m long ethernet cables) from the CREAMs. The LKrL0 TX
and LKrL0 RX mezzanines transmit reconstructed clusters (48 bit @ 80
MHz over 2 m long individually shielded twisted pair cables) from the
front-end to the concentrator cards and between the two layers of
concentrator cards. Two 48 bit words (including the payload and error
correction code) are needed to transmit energy, position and time of a
single cluster allowing the transmission of up to 40 MHz of clusters
reconstructed by each front-end board from a single 32 tiles
calorimeter slice.
The system was partially installed (15%) and tested during a
commissioning run in 2014. The first physics run of NA62 is scheduled to start at the beginning
of July 2015 and the full trigger system will be used for the first
time. In this contribution we will present performances and
results obtained in the first months of data taking.
