Normalised transverse emittance reduction via ionisation cooling in MICE ‘Flip Mode’
File(s)
Author(s)
Jurj, Paul Bogdan
Type
Thesis
Abstract
Low-emittance muon beams are central to the development of a Muon Collider and
can significantly enhance the performance of a Neutrino Factory. The main challenge
for muon acceleration stems from the large emittance with which the muon beam is
produced. Maximising the muon yield while maintaining a suitably small aperture in
the accelerator system requires that the muon beam emittance be reduced (cooled).
The international Muon Ionisation Cooling Experiment (MICE) was designed to
demonstrate the feasibility of the ionisation cooling technique, and provide the
first measurement of normalised transverse emittance reduction in a muon beam.
This work focuses on the emittance reduction analysis of 140 MeV/c MICE muon
beams that passed through a liquid hydrogen or a lithium hydride absorber. During
the acquisition of the studied data sets, the magnetic channel produced a field that
flipped polarity at the absorber, to prevent a canonical angular momentum increase.
A novel beam sampling procedure was developed to account for imperfections in
beam matching at the entrance into the cooling channel, which improved the cooling
signal measurement. A reduction in the muon beam normalised transverse emittance
that grows linearly with input emittance was observed, which is a clear signal of
ionisation cooling. The measurement is consistent with the simulation and the
theoretical model.
Furthermore, both the liquid hydrogen and the lithium hydride absorbers were
found to induce a reduction in the mean canonical angular momentum of the beam.
This effect can be attributed to energy loss at the absorber situated at the field
polarity flip, combined with an increasing beam size across the absorber region.
This result confirms that the field polarity flip at the absorber would maintain a
low-magnitude canonical angular momentum within the cooling stage of a future
muon facility.
can significantly enhance the performance of a Neutrino Factory. The main challenge
for muon acceleration stems from the large emittance with which the muon beam is
produced. Maximising the muon yield while maintaining a suitably small aperture in
the accelerator system requires that the muon beam emittance be reduced (cooled).
The international Muon Ionisation Cooling Experiment (MICE) was designed to
demonstrate the feasibility of the ionisation cooling technique, and provide the
first measurement of normalised transverse emittance reduction in a muon beam.
This work focuses on the emittance reduction analysis of 140 MeV/c MICE muon
beams that passed through a liquid hydrogen or a lithium hydride absorber. During
the acquisition of the studied data sets, the magnetic channel produced a field that
flipped polarity at the absorber, to prevent a canonical angular momentum increase.
A novel beam sampling procedure was developed to account for imperfections in
beam matching at the entrance into the cooling channel, which improved the cooling
signal measurement. A reduction in the muon beam normalised transverse emittance
that grows linearly with input emittance was observed, which is a clear signal of
ionisation cooling. The measurement is consistent with the simulation and the
theoretical model.
Furthermore, both the liquid hydrogen and the lithium hydride absorbers were
found to induce a reduction in the mean canonical angular momentum of the beam.
This effect can be attributed to energy loss at the absorber situated at the field
polarity flip, combined with an increasing beam size across the absorber region.
This result confirms that the field polarity flip at the absorber would maintain a
low-magnitude canonical angular momentum within the cooling stage of a future
muon facility.
Version
Open Access
Date Issued
2022-05
Date Awarded
2022-11
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Pasternak, Jaroslaw
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)