First simultaneous detection of electron and positron bunches at the positron capture section of the SuperKEKB factory

Tsuyoshi Suwada,Muhammad Abdul Rehman,Fusashi Miyahara

doi:10.1038/s41598-021-91707-0

Abstract

The direct simultaneous detection of electron and positron bunch signals was successfully performed for the first time with wideband pickups and a detection system at the positron capture section of the SuperKEKB factory. The time interval between the electron and positron bunches, their bunch lengths, and bunch intensities depending on the phase of accelerating structures were measured to investigate their capture process and to maximally optimize the positron intensity. The results show that the time intervals were measured in the range of 135–265 ps, and the line-order switch of the electron and positron bunches in the axial direction was clearly observed as a function of the phase. The positron (electron) intensity was maximized at the optimal phase (180^{circ } shifted from the optimum). These series of measurements have never been experimentally conducted so far. It is demonstrated that the positron intensity can be systematically optimized with this system as functions of beam parameters in multidimensional spaces for any positron capture section.

Highlights

The direct simultaneous detection of electron and positron bunch signals was successfully performed for the first time with wideband pickups and a detection system at the positron capture section of the SuperKEKB factory
They have never been measured because the time interval is too short to detect them independently, while they are generally simulated on the basis of beam dynamics in
The frequency characteristics of the pickup signals detected by the new beam monitor were measured to investigate the transient responses of the pickups along with signal transmission cables for the injection e− and e+ modes as a function of the cutoff frequency of a wideband oscilloscope

Summary

Introduction

The direct simultaneous detection of electron and positron bunch signals was successfully performed for the first time with wideband pickups and a detection system at the positron capture section of the SuperKEKB factory. The positrons are to be efficiently captured using a new flux concentrator and large-aperture S-band accelerating s tructures[10] in the e+ capture section, and they are to be damped to the level required for the low-emittance beam through a new damping ring (DR)[11]. Since both the electrons and positrons with approximately equivalent amounts of bunch charges are generated at the target, the positrons and the electrons are simultaneously captured and accelerated (or decelerated) in the capture section. They have never been measured because the time interval is too short to detect them independently, while they are generally simulated on the basis of beam dynamics in Scientific Reports | (2021) 11:12751

Methods

Results

Conclusion