Abstract
During long shutdown 2 (2019-2020) the transverse observation system (ADTObsBox) in the LHC will undergo a substantial upgrade. The purpose of this upgrade is to allow for true low latency, online processing of the 16 data-streams of transverse bunch-by-bunch, turn-by-turn positional data provided by the transverse feedback system in the LHC (ADT). This system makes both offline and online analysis of the data possible, where the emphasis will lie on online analysis, something that the older generation was not designed to provide. The result of the analysis is made available for accelerator physicists, machine operators, and engineers working with LHC. The new system allows users to capture buffers of various lengths for later analysis just like the older generation and it provides a platform for real-time analysis applications to directly capture the data with minimal latency while also providing a heterogeneous computing platform where the applications can utilize CPUs, GPUs and dedicated FPGAs. The analysis applications include bunch-by-bunch instability analysis and passive bunch-by-bunch tune extraction to name a few. The ADTObsBox system uses commodity server technology in combination with FPGA-based PCIe I/O cards. This paper will cover the design and status of the I/O cards, server, firmware, driver, analysis applications and results of early performance testing.
Highlights
In 2015, a system called ObsBox (Observation Box) [1] was introduced by the RadioFrequency group at CERN which allowed for buffering of multiple high-bandwidth datastreams from the Low-Level RF systems
The ADTObsBoxes receive the data from the 16 ADT Beam Position Monitor (BPM) VME modules, each with a link speed of 1 Gbit/s and a data transfer rate of 0.8 Gbit/s
The latency was tested by having the driver toggle a register in the I/O card every time a new transfer was completed and using the Xilinx integrated logic analyzer (ILA) to measure the time between receiving the start of a frame and the time until the register was toggled
Summary
In 2015, a system called ObsBox (Observation Box) [1] was introduced by the RadioFrequency group at CERN which allowed for buffering of multiple high-bandwidth datastreams from the Low-Level RF systems. The system was designed to be general purpose with the first application in the LHC for both the transverse [1, 2] and longitudinal plane [3]. The ADTObsBoxes receive the data from the 16 ADT Beam Position Monitor (BPM) VME modules, each with a link speed of 1 Gbit/s and a data transfer rate of 0.8 Gbit/s. After decoding, this results in a combined rate of 1.28 GB/s. In 2016, an online transverse instability detection system [6] was introduced that analyzed the beam positional data for exponential oscillation amplitude growths to detect an onset of transverse instability (all analysis performed bunch-by-bunch). That is proposed for the LHC restart in 2021 is a passive bunch-by-bunch tune extraction application which will combine data from multiple pickups and perform spectrum analysis on each bunch
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