Ultra High Molecular Weight Polyethylene: optical features at millimeter wavelengths

TL;DR

This paper investigates the optical properties of Ultra High Molecular Weight Polyethylene (UHMW PE) at millimeter wavelengths to assess its suitability for use in CMB experiment components like cryostat windows and lenses.

Contribution

It provides the first detailed measurements of UHMW PE's emissivity, transmission, and refraction index at millimeter wavelengths, demonstrating its potential for use in CMB instrumentation.

Findings

UHMW PE has low emissivity suitable for optical components.

The material exhibits high transmissivity at millimeter wavelengths.

UHMW PE's optical properties support its application in large-diameter CMB experiment parts.

Abstract

The next generation of experiments for the measurement of the Cosmic Microwave Background (CMB) requires more and more the use of advanced materials, with specific physical and structural properties. An example is the material used for receiver's cryostat windows and internal lenses. The large throughput of current CMB experiments requires a large diameter (of the order of 0.5m) of these parts, resulting in heavy structural and optical requirements on the material to be used. Ultra High Molecular Weight (UHMW) polyethylene (PE) features high resistance to traction and good transmissivity in the frequency range of interest. In this paper, we discuss the possibility of using UHMW PE for windows and lenses in experiments working at millimeter wavelengths, by measuring its optical properties: emissivity, transmission and refraction index. Our measurements show that the material is well suited to this purpose.