# CMB-S4 Technology Book, First Edition

## TL;DR

The CMB-S4 Technology Book outlines the current state and future R&D needs of instrumentation technology essential for the ambitious ground-based cosmic microwave background polarization experiment, aiming to achieve near cosmic variance limit measurements.

## Contribution

It provides a comprehensive overview of technological challenges and R&D directions necessary for advancing CMB instrumentation for the next-generation CMB-S4 experiment.

## Key findings

- Summarizes current instrumentation technology for CMB-S4
- Identifies key R&D areas in telescope design and sensors
- Highlights technical challenges in focal-plane optical coupling

## Abstract

CMB-S4 is a proposed experiment to map the polarization of the Cosmic Microwave Background (CMB) to nearly the cosmic variance limit for angular scales that are accessible from the ground. The science goals and capabilities of CMB-S4 in illuminating cosmic inflation, measuring the sum of neutrino masses, searching for relativistic relics in the early universe, characterizing dark energy and dark matter, and mapping the matter distribution in the universe have been described in the CMB-S4 Science Book. This Technology Book is a companion volume to the Science Book. The ambitious science goals of CMB-S4, a "Stage-4" experiment, require a step forward in experimental capability from the current Stage=II experiments. To guide this process, we summarize the current state of CMB instrumentation technology, and identify R&D efforts necessary to advance it for use in CMB-S4. The book focuses on technical challenges in four broad areas: Telescope Design; Receiver Optics; Focal-Plane Optical Coupling; and Focal-Plane Sensor and Readout.