VME Readout at and Below the Conversion Time Limit

TL;DR

This paper introduces an asynchronous VME readout scheme that enhances data acquisition livetime in nuclear physics experiments, outperforming traditional synchronous methods and optimizing network interactions for better performance.

Contribution

The paper presents a novel asynchronous readout scheme for VME systems, significantly reducing deadtime and increasing event recording efficiency compared to existing synchronous approaches.

Findings

30% deadtime reduction at 20 kHz trigger frequency

10% more events recorded in the same time

Network readout optimization mitigates livetime loss

Abstract

The achievable acquisition rates of modern triggered nuclear physics experiments are heavily dependent on the readout software, in addition to the limits given by the utilized hardware. This paper presents an asynchronous readout scheme that significantly improves the livetime of an otherwise synchronous triggered VME-based data acquisition system. A detailed performance analysis of this and other readout schemes, in terms of the basic data transfer operations, is described. The performance of the newly developed scheme as well as synchronous schemes on two systems has been measured. The measurements show excellent agreement with the detailed description. For the second system, which previously used a synchronous readout, the deadtime ratio is at a 20 kHz trigger request frequency reduced by 30 % compared to the nearest contender, allowing 10 % more events to be recorded in the same time. The interaction between the network and readout tasks for single-core processors is also investigated. A livetime ratio loss of a few percent can be observed, depending on the size of the data chunks given to the operating system kernel for network transfer. With appropriately chosen chunk size, the effect can be mitigated.