A time resolved study of injection backgrounds during the first commissioning phase of SuperKEKB

TL;DR

This study uses a high-resolution detector system to analyze injection and regular beam backgrounds at SuperKEKB during initial commissioning, revealing detailed time structures and decay behaviors of background particles.

Contribution

It introduces a novel time-resolved measurement technique for beam backgrounds using a scintillator and silicon photomultiplier system, enabling detailed analysis of injection backgrounds.

Findings

Background rates last several milliseconds after injection

Most background particles are observed within 500 microseconds

Injection backgrounds show patterns linked to accelerator oscillations

Abstract

We report on measurements of beam backgrounds during the first commissioning phase of the SuperKEKB collider in 2016, performed with the plastic scintillator and silicon photomultiplier-based CLAWS detector system. The sub-nanosecond time resolution and single particle detection capability of the sensors allow bunch-by-bunch measurements, enable CLAWS to perform a novel time resolved analysis of beam backgrounds, and make the system uniquely suited for the study of injection backgrounds. We present measurements of various aspects of regular beam background and injection backgrounds which include time structure and decay behavior of injection backgrounds, hit-energy spectra and overall background rates. These measurements show that the elevated background rates following an injection generally last for several milliseconds, with the majority of the background particles typically observed within the first 500 us. The injection backgrounds exhibit pronounced patterns in time, connected to betatron and synchrotron oscillations in the accelerator rings. The frequencies of these patterns are determined from detector data.