Technical Design Report Super Fragment Separator

DRAFT
synchronization to the BuTiS clock with a defined phase. Different types of FEE will also provide
their local clocks. One may consider the following scenarios:
a) Self-made timestamps, where a specification of the latency of the front-end trigger with
respect to the timestamps is needed in order to be able to synchronize the particular data to
the overall system. The latency can be automatically determined e.g. by using generated
synchronization events from the host DAQ system to the particular timestamp generating
system. Another question is how to couple local systems to BuTiS. One BuTiS receiver per
local timestamping system might be too expensive it is a subject to further R&D whether an
additional (experiment-wide) time distribution layer is desirable.
b) For the standardized NUSTAR DAQ one should consider to build a novel “Titris II”
module in different form factors, to be used in VME crates or attached to the FEE, which
can be coupled to the BuTiS system.
We can mainly base our studies on the already existing techniques, use of time-stamping followed
by software filters and triggers which were developed for GREAT. Within GREAT these items are
handled by the Metronome and its interface to the ADC cards. Within the next years we need to
specify latencies for trigger decisions depending on the physics of the trigger, taking into account
the limited pre-processing buffer depths, and their associated acceptance window. Here dedicated
input from the different experiments is needed to come up with a generalized and flexible scheme.
2.4.A1.2 Data collection and storage
Maximum data rates of 10-100 Mbytes/sec are estimated for the EXL and R³B setups. Thus the
total data produced per day is in the order of 1-10 TBytes. This means, for the NUSTAR experiments
we expect not more than 500TB/year of data. The requested band-width for data transfer is
in accordance with the expected rates that can be transferred using standard network components.
The demand to run independent NUSTAR DAQ modules that can be combined in a flexible
manner poses certain requirements to the transport layer in between the experiments and to the
mass storage:
1. Standardized sub-event format; this is favourable in order to facilitate to event
building from different data sources.
2. Flexible event builder combinations; one may consider to use different parts of the
data stream at different locations to perform different tasks: mass storage; online
analysis; slow control feedback.
3. Standardized event format; to be used for a common unpacking scheme for data
analysis.
The NUSTAR DAQ system will provide the necessary data collection procedures for standard
electronics module (e.g. VME) and collection from FE-boards that follow the conventions for the
standardized digital interfaces (e.g. GTB). The necessary R&D work will be done in parallel to the
various electronic developments in the NUSTAR community in close collaboration with the respective
groups, co-ordinated by the DAQ responsible for the particular experiments.
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