ESS, Lund, Sweden
The European Spallation Source (ESS) will be a cutting-edge research facility that uses neutrons to study the properties of materials. This paper presents the timestamping strategy employed in the neutron instruments of the ESS, to enable efficient data correlation across subsystems and between different sources of experiment data. ESS uses absolute timestamps for all data and a global source clock to synchronize and timestamp data at the lowest appropriate level from each subsystem. This way we control the impact of jitter, delays and latencies when transferring experiment data to the data storage. ESS utilizes three time synchronisation technologies. The Network Time Protocol (NTP) providing an expected accuracy of approximately 10 milliseconds, the Precision Time Protocol (PTP) delivering roughly 10 microsecond accuracy, and hardware timing using Microreseach Finland (MRF) Event Receivers (EVR) which can reach 10 nanoseconds of accuracy. Both NTP and PTP rely on network communication using common internet protocols, while the EVRs use physical input and output signals combined with timestamp latching in hardware. The selection of the timestamping technology for each device and subsystem is based on their timestamp accuracy requirements, available interfaces, and cost requirements. This paper describes the choice of method used for different device types, like neutron choppers, detectors or sample environment equipment and covers some details of the implementation and characterisation.
HZB, Berlin, Germany
MLZ, Garching, Germany
ESS, Lund, Sweden
DESY, Hamburg, Germany
PSI, Villigen PSI, Switzerland
The integration of sample environment (SE) equipment in x-ray and neutron experiments is a complex challenge both in the physical world and in the digital world. Dif-ferent experiment control software offer different interfac-es for the connection of SE equipment. Therefore, it is time-consuming to integrate new SE or to share SE equipment between facilities. To tackle this problem, the International Society for Sample Environment (ISSE, [1]) developed the Sample Environment Communication Protocol (SECoP) to standardize the communication between instrument control software and SE equipment [2]. SECoP offers, on the one hand, a generalized way to control SE equipment. On the other hand, SECoP holds the possibility to transport SE metadata in a well-defined way. In addition, SECoP provides machine readable self-description of the SE equipment which enables a fully automated integration into the instrument control soft-ware and into the processes for data storage. Using SECoP as a common standard for controlling SE equipment and generating SE metadata will save resources and intrinsi-cally give the opportunity to supply standardized and FAIR data compliant SE metadata. It will also supply a well-defined interface for user-provided SE equipment, for equipment shared by different research facilities and for industry. In this article will show how SECoP can help to provide a meaningful and complete set of metadata for SE equipment and we will present SECoP and the SECoP@HMC project supported by the Helmholtz Metadata Collaboration.
*K. Kiefer, et al. (2020). An introduction to SECoP - the sample environment communication protocol. Journal of Neutron Research, 21(3-4), pp.181-195