  We have experimentally demonstrated the first non-intrusive 1-GeV proton beam
extraction for the generation of muons with a temporal structure optimized for
Muon Spin Relaxation/Rotation/Resonance (MuSR) applications. The proton pulses
are extracted based on the laser neutralization of 1 GeV hydrogen ion (H-) beam
in the high energy beam transport of the Spallation Neutron Source (SNS)
accelerator. The maximum flux of the extracted proton beam accounts for only
0.2% of the total proton beam used for neutron production, a marked difference
from the 20% reduction at other co-located muon and neutron facilities, and
thus the proposed method will result in negligible impact on the SNS operation.
This paper describes the development of a fiber/solid-state hybrid laser system
that has high flexibility of pulse structure and output power, initial
experiments on laser neutralization of H- beam and separation of H0 beam from
the existing SNS accelerator beam line, conversion of H0 to proton at the SNS
linac dump, and measurement results of 30 ns/50 kHz proton pulses. This system
conclusively demonstrates the feasibility of laser-based proton beam extraction
to power a world-leading MuSR facility at the SNS.
