STORI2024: Tests of Amorphous Carbon-coated Storage Cells for a Polarized Gas Target at LHCb and Further Results

TL;DR

This paper investigates amorphous carbon-coated storage cells for polarized gas targets at LHCb, demonstrating high polarization preservation, efficient molecule production, and new polarized ion generation, enabling advanced spin physics experiments at CERN.

Contribution

It introduces the use of amorphous carbon coatings for storage cells in polarized gas targets, showing improved polarization retention and new polarized molecule and ion production capabilities.

Findings

High recombination rate (93-100%) with polarization >74%

Successful production of polarized H$_2$ molecules with P~0.59

First production of polarized H$_3^+$ ions and observation of axis shift in HD molecules

Abstract

As the LHC beams cannot be polarized, introducing a dense polarized gas target at the LHCb experiment at CERN, to be operated concurrently with beam-beam collisions, will facilitate fixed-target interactions to explore a new energy regime of spin physics measurements. Unfortunately, typical surface coatings, such as water, Teflon, or aluminum, commonly used to avoid polarization losses, are prohibited due to restrictions imposed by vacuum and beam policies. Using the former atomic beam source for the polarized target at ANKE/COSY (Forschungszentrum J\"ulich), an accompanying Lamb-shift polarimeter and a storage cell chamber inside a superconducting magnet, provide a perfect test stand to investigate the properties of a storage cell coated with amorphous carbon. A significant recombination rate, ranging from $93\%$ to $100\%$, as well as preservation of polarization during recombination surpassing $74\%$, were observed. We successfully produced H$_2$ molecules with a nuclear polarization of P$\sim 0.59$. In addition, we could produce polarized H$_3^+$ ions for the first time and observed the shift of the axis of rotation within HD molecules.