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Design and expected performance of the MICE Demonstration of Ionization Cooling

Abstract

Muon beams of low emittance provide the basis for the intense, well-characterised neutrino beams necessary to elucidate the physics of flavour at a neutrino factory and to provide lepton-antilepton collisions at energies of up to several TeV at a muon collider. The international Muon Ionization Cooling Experiment (MICE) aims to demonstrate ionization cooling, the technique by which it is proposed to reduce the phase-space volume occupied by the muon beam at such facilities. In an ionization-cooling channel, the muon beam passes through a material in which it loses energy. The energy lost is then replaced using RF cavities. The combined effect of energy loss and re-acceleration is to reduce the transverse emittance of the beam (transverse cooling). A major revision of the scope of the project was carried out over the summer of 2014. The revised experiment can deliver a demonstration of ionization cooling. The design of the cooling demonstration experiment will be described together with its predicted cooling performance.

Paper

Published in: forthcoming
arXiv: 1701.06403
RAL Preprint: RAL-P-2017-002
DOI: forthcoming

BibTex: forthcoming
References: forthcoming
Source

Figures

Figure 1

Layout of the lattice configuration for the cooling demonstration. The red rectangles represent the solenoids. The individual coils in the spectrometer solenoids are labelled E1, C, E2, M1 and M2. The ovals represent the RF cavities and the blue rectangles the absorbers. The various detectors (time-of-flight hodoscopes, Cerenkov counters, scintillating-fibre trackers, KLOE Light (KL) calorimeter, electron muon ranger used to characterise the beam are also represented. The green-shaded box indicates the cooling cell.

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Figure 2

Design of the movable frame for the secondary absorber (front) and the lead radiation shutter (back). The half discs of the lead shutter (grey) can be seen together with the rails (white) inside the vacuum chamber (yellow).

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Figure 3

Transverse 4D beta-function versus longitudinal coordinate z in the cooling-demonstration lattice for 200 MeV/c settings with a phase advance of 2 pi x 1.75 (dashed blue line), 2 pi x 1.81 (solid red line) and 2 pi x 1.86 (dot-dashed green line). The vertical dashed lines with labels show the positions of the tracker reference planes and the centres of the absorbers, RF cavities and focus coil modules.

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Figure 4

4D emittance evolution in the cooling-demonstration lattice for 200 MeV/c settings with a phase advance of 2 pi x 1.75 (dashed blue line), 2 pi x 1.81 (solid red line) and 2 pi x 1.86 (dot-dashed green line). The vertical dashed lines with labels show the positions of the tracker reference planes and the centres of the absorbers, RF cavities and focus coil modules.

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Figure 5

Magnetic field Bz on-axis versus the longitudinal coordinate z for the cooling-demonstration lattice design for 200 MeV/c (solid black line), 140 MeV/c (dashed purple line) and 240 MeV/c (dot-dashed blue line) settings. The vertical dashed lines with labels show the positions of the tracker reference planes and the centres of the absorbers, RF cavities and focus coil modules.

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Figure 6

beta_perp versus the longitudinal coordinate z for 200 MeV/c (solid black line), 140 MeV/c (dashed purple line) and 240 MeV/c (dot-dashed blue line) in the cooling-demonstration lattice. The vertical dashed lines with labels show the positions of the tracker reference planes and the centres of the absorbers, RF cavities and focus coil modules.

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Figure 7

Mean energy of the beam versus longitudinal coordinate (z) in the cooling-demonstration lattice. Top: the 140 MeV/c configuration for initial emittance 4.2 mm. Middle: the 200 MeV/c configuration for initial emittance 6 mm. Bottom: the 240 MeV/c configuration for initial emittance 7.2 mm. The vertical dashed lines with labels show the positions of the tracker reference planes, and the centres of the absorbers, RF cavities and focus-coil modules.

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Figure 8

Emittance variation versus the longitudinal coordinate (z) for the cooling-demonstration lattice design. Top: 140 MeV/c beam with initial emittance 4.2 mm with an rms momentum spread of 6.7 MeV/c (rms spread 4.8, solid line) and 2.5 MeV/c (rms spread 1.8 %, dashed line). Middle: 200 MeV/c beam with initial emittance 6 mm (rms spread 4.0 %). Bottom: 240 MeV/c beam with initial emittance 7.2 mm (rms spread 3.6 %). The vertical dashed lines with labels show the positions of the tracker reference planes, and the centres of the absorbers, RF cavities and focus coil modules.

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Figure 9

Transmission (defined as the ratio of good muons observed downstream of the cooling cell to those observed upstream as a percentage) versus initial emittance for the cooling-demonstration lattice. The transmission of the 140 MeV/c, 200 MeV/c and 240 MeV/c lattices are shown as the purple-dashed, solid black, and dot-dashed blue lines respectively.

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Figure 10

Fractional change in emittance versus initial emittance for the cooling-demonstration lattice design measured at the tracker reference planes. The fractional change in emittance of the 140 MeV/c, 200 MeV/c and 240 MeV/c lattices are shown as the purple-dashed, solid black, and dot-dashed blue lines respectively.

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Tables

Table 1

General parameters of the initial beam conditions used in the simulations.

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Table 2

Parameters of the cooling-demonstration lattice. L_{SS->FC} is the distance between the centre of the spectrometer solenoid and the centre of the neighbouring FC, L_{FC->FC} the distance between the centres of the FCs, and L_{RF->FC} the distance between the RF module and the neighbouring FC.

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Table 3

Coil currents used for 140 MeV/c, 200 MeV/c and 240 MeV/c lattice settings.

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Table 4

Beta-function values at relevant positions for an initial beam at 140 MeV/c, 200 MeV/c and 240 MeV/c in the cooling-demonstration lattice design.

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Table 5

Acceptance criteria for analysis.

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shutter.pdf (19.1 MB) Rogers, Chris, 25 January 2017 15:53

shutter.ps (38.2 MB) Rogers, Chris, 25 January 2017 15:53

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beta_phase_adv_final_thumb.png (15 KB) Rogers, Chris, 25 January 2017 15:53

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table_5.tex (99 Bytes) Rogers, Chris, 26 January 2017 09:32

1701.06403v1.tar (1.51 MB) Rogers, Chris, 26 January 2017 10:58