Stephen BrooksJAI Advisory Board, February 2006

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Neutrino Factory Muon Beam Production Studies

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Confusing Acronyms• I am a DPhil student1 with Oxford Particle

Physics and part of the JAI• I actually work at RAL (a site of CCLRC) in the

ASTeC Intense Beams Group• Nationally, my research contributes to the UKNF

project2 (funded by PPARC)– Specifically, WP1: Conceptual Design3

• Internationally, this year it contributes to the NF Scoping Study (ISS)4

– Specifically, the accelerator study group5

[1] Supervisor: John Cobb, Oxford PP[2] Project leader: Ken Long, Imperial College[3] WP manager: Chris Prior, ASTeC IB Group, RAL[4] Project leader: Peter Dornan, Imperial College[5] Group coordinator: Mike Zisman, LBNL

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Thesis Title

• “Muon Capture and Cooling Schemes for the Neutrino Factory”

• So far I’ve concentrated on muon capture

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Problem

• The neutrino factory is (at least) a tertiary beam facility:

p+ » on target ± ± » ,e,

• Efficient capture of the pions as they decay to muons is a critical step

• Resultant beam must obey constraints longitudinally (E, bunch length) and transversely (emittance < acceptance)

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Research Activity (so far)

• Simulations of pion production in target– Optimal proton energy (or energies)– Target material choice

• Tracking of particles up to cooling– Finding the most efficient capture system

• Comparison, optimisation of schemes

– Also defining what we want from the target

• Cooling modelling preparation

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UKNF Muon “Front End”

Solenoidal decay channelRF phase rotation(reduces energy spread)

Target: difficult engineering challenge in itself, covered by UKNF WP2

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Target Simulations

• Particle production setup:

• Used MARS15 code• Scanned possible proton energies• Four materials studied so far

– Ta (solid), Hg (liquid jet), C (granular?), Cu

NF International Scoping Study (ISS); also GEANT4 benchmarking by K. Walaron

20cm for Ta … 66cm for C

1cmCylinder of material

Protons

Pions

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Target Results"PR2.2" Probability Grid Yield (MARS15)

0

0.005

0.01

0.015

0.02

0.025

0.1 1 10 100 1000

Proton Energy (GeV)

Par

ticl

es p

er p

.GeV

Tantalum piplus

Tantalum piminus

Mercury piplus

Mercury piminus

Carbon piplus

Carbon piminus

Copper piplus

Copper piminus

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Particle Tracking Features

• Starts with MARS15 output

• Cannot use paraxial approximation, so 3D– Nonlinear dynamics e.g. spherical aberration– (Somewhat) realistic geometry, obstructions

• Includes ± ± and muon, kaon decays

• Supports lattice optimisation ranges– Novel multi-parameter approach– Genetic algorithm

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Simulation

• Challenge: high emittance of target pions– Here they come from a 20cm tantalum rod

Evolution of pions from 2.2GeV proton beam on tantalum rod target

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Optimisation Network

• Internet-based computer grid being used– 20 million simulations run, 100s of users– Several lattice-ranges submitted

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Muon Cooling

G.H. Rees at RAL conceptually designed a “cooling dogbone” lattice– Future use for tracking/optimising code– Will compare with John Cobb using ICOOL

• Must include ‘energy absorbers’ (material)• At Oxford, the ELMS study has computed

the real muon cross-sections needed– I’ve studied how to integrate this with my code– Wade Allison, Simon Holmes’ speciality (next!)

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Alternative Design

Over 80% caught in linac bucket

Chicane phase rotation decreases the bunch length