BPM technologies for quadrupolar moment measurements

Abstract

Quadrupolar pick-ups (PU) have attracted particlular interest as candidates for non-intercepting beam size and emittance measurements. However, their application has been proven to be limited. Two fundamental factors make beam size measurements with quadrupolar PUs exceptionally challenging: first, the low quadrupolar sensitivity of PUs and second, the parasitic position signal incorporated into the measured quadrupolar quantity. In this paper, the basic concepts of the quadrupolar measurements are reviewed with a special focus on the challenging nature of the measurements. Additionally, the potential use of existing beam position monitor (BPM) technology is studied. Recent tests performed with BPMs in the Large Hadron Collider (LHC) are discussed. Preliminary measurements demonstrate promising results.