Ultra thin polymer foil cryogenic window for antiproton deceleration and storage

TL;DR

This paper introduces a cryogenic ultra-thin polymer foil window designed for antiproton deceleration and storage, demonstrating its durability, particle transparency, and effectiveness in decelerating antiprotons for experimental use.

Contribution

The study presents a novel cryogenic window made from aluminised PET foil, optimized for antiproton transfer, with detailed characterization and testing for durability and particle transmission.

Findings

The foil withstands pressure differences over 1 bar at very low leak rates.

A 1760 nm thick foil decelerates 100 keV antiprotons to about 5 keV.

The window transmits up to 2.5% of injected 100 keV antiprotons.

Abstract

We present the design and characterisation of a cryogenic window based on an ultra-thin aluminised PET foil at T < 10K, which can withstand a pressure difference larger than 1bar at a leak rate < $1\times 10^{-9}$ mbar$\cdot$ l/s. Its thickness of approximately 1.7 $\mu$m makes it transparent to various types of particles over a broad energy range. To optimise the transfer of 100keV antiprotons through the window, we tested the degrading properties of different aluminium coated PET foils of thicknesses between 900nm and 2160nm, concluding that 1760nm foil decelerates antiprotons to an average energy of 5 keV. We have also explicitly studied the permeation as a function of coating thickness and temperature, and have performed extensive thermal and mechanical endurance and stress tests. Our final design integrated into the experiment has an effective open surface consisting of 7 holes with 1 mm diameter and will transmit up to 2.5% of the injected 100keV antiproton beam delivered by the AD/ELENA-facility of CERN.