# The Narrow-beam Diffuser Subsystem of a Prototype Optical Calibration System for the Hyper-Kamiokande Detector

## TL;DR

This paper describes the development and testing of a narrow-beam diffuser subsystem for an optical calibration system in the Hyper-Kamiokande neutrino detector, aiming to improve in-situ sensor calibration.

## Contribution

It introduces a novel narrow-beam diffuser hardware and details its testing procedures within the Hyper-Kamiokande calibration system.

## Key findings

- Successful installation of the diffuser hardware in Super-Kamiokande
- Demonstrated effective light injection for sensor calibration
- Provided detailed testing procedures for the diffuser system

## Abstract

The Hyper-Kamiokande neutrino detector is set to begin construction in 2020, succeeding Super-Kamiokande as the world's largest water Cerenkov detector. Research and development are well underway for an integrated light injection system for Hyper-Kamiokande which will provide in-situ monitoring of photo-sensor responses and water transparency. In summer 2018, optical hardware forming an iteration of this system was installed in Super-Kamiokande. We present details of the narrow-beam diffuser hardware and testing procedures, in addition to a brief summary of the installed light injection system.