Wide spin resonance with an rf-bunched proton beam

TL;DR

This study investigates the width of rf spin resonances in polarized proton beams, revealing that bunching significantly broadens the resonance, contrasting with previous observations in deuteron beams.

Contribution

It provides the first detailed comparison of resonance widths between bunched and unbunched proton beams using rf solenoid techniques.

Findings

Bunched proton beams exhibit wider resonance regions than unbunched beams.

Frequency sweeps enhance depolarization dips in unbunched beams.

Resonance broadening due to bunching is opposite to deuteron behavior.

Abstract

We recently used an rf solenoid to study the widths of rf spin resonances with both unbunched and bunched beams of 2.1 GeV_c polarized protons stored in the COSY synchrotron. A map, with unbunched beam at different fixed rf-solenoid frequencies, showed a very shallow possible depolarization dip at the resonance. Next we made frequency sweeps of 400Hz, centered at similar frequencies, which greatly enhanced the dip. But, with a bunched proton beam, both the fixed-frequency and frequency-sweep techniques produced similar maps, and both bunched maps showed full beam depolarization over a wide region. Moreover, both were more than twice as wide as the unbunched dip. This widening of the proton resonance due to bunching is exactly opposite to the recently observed narrowing of deuteron resonances due to bunching.