The ATLAS beam pick-up based timing system

TL;DR

The paper describes the ATLAS BPTX beam pick-up system used for timing, trigger, and beam monitoring, highlighting its performance during initial LHC beam operations and its role in ensuring precise timing and beam structure measurements.

Contribution

This work presents the design, implementation, and performance evaluation of the ATLAS BPTX system for beam timing and monitoring at the LHC.

Findings

BPTX system achieved phase measurement precision better than 100 ps.

Successfully used during initial LHC beam runs for timing and beam structure analysis.

Demonstrated reliable performance in a high-energy physics environment.

Abstract

The ATLAS BPTX stations are comprised of electrostatic button pick-up detectors, located 175 m away along the beam pipe on both sides of ATLAS. The pick-ups are installed as a part of the LHC beam instrumentation and used by ATLAS for timing purposes. The usage of the BPTX signals in ATLAS is twofold: they are used both in the trigger system and for LHC beam monitoring. The BPTX signals are discriminated with a constant-fraction discriminator to provide a Level-1 trigger when a bunch passes through ATLAS. Furthermore, the BPTX detectors are used by a stand-alone monitoring system for the LHC bunches and timing signals. The BPTX monitoring system measures the phase between collisions and clock with a precision better than 100 ps in order to guarantee a stable phase relationship for optimal signal sampling in the subdetector front-end electronics. In addition to monitoring this phase, the properties of the individual bunches are measured and the structure of the beams is determined. On September 10, 2008, the first LHC beams reached the ATLAS experiment. During this period with beam, the ATLAS BPTX system was used extensively to time in the read-out of the sub-detectors. In this paper, we present the performance of the BPTX system and its measurements of the first LHC beams.