Rol - July 21, 2009Rol - July 21, 2009 NuFact09NuFact09 11

Muon Cooling for a Neutrino Factory 

Rolland P. JohnsonMuons, Inc. (http://www.muonsinc.com/)

 More muon cooling in NF designs would improve synergy between NF and MC R&D.

Present designs of MC front-ends would fill NF storage rings very well.

6D muon cooling progress has been encouraging. It may well be ready for prime time when a NF is to be built.

Muons, Inc.

Rol - July 21, 2009Rol - July 21, 2009 NuFact09NuFact09 22

Muons, Inc. Scenario for:Muons, Inc. Scenario for:High-Energy High-Luminosity High-Energy High-Luminosity

Muon CollidersMuon Colliders precision lepton machines at the energy frontierprecision lepton machines at the energy frontier achieved in physics-motivated stages that require achieved in physics-motivated stages that require

developing inventions and technology, e.g.developing inventions and technology, e.g.• intense proton driver (CW Linac, H- Source, Laser Stripping) intense proton driver (CW Linac, H- Source, Laser Stripping) • stopping muon beams (HCC, EEX w Homogeneous absorber)stopping muon beams (HCC, EEX w Homogeneous absorber)• neutrino factory (HCC with HPRF, RLA in CW Proj-X)neutrino factory (HCC with HPRF, RLA in CW Proj-X)• Z’ factory (low Luminosity collider, HE RLA)Z’ factory (low Luminosity collider, HE RLA)• Higgs factory (extreme cooling, low beta, super-detectors)Higgs factory (extreme cooling, low beta, super-detectors)• Energy-frontier muon collider (more cooling, lower beta)Energy-frontier muon collider (more cooling, lower beta)

Muons, Inc.

LEMC ScenarioLEMC Scenario

Rol - July 21, 2009Rol - July 21, 2009 NuFact09NuFact09 33

Muons, Inc.

Bogacz DogbonesScheme

NF from MC front endNF from MC front endWhile many aspects of MC and NF R&D are shared, muon beam cooling is While many aspects of MC and NF R&D are shared, muon beam cooling is

an exception. an exception.

In the present ISS NF scheme, relatively little transverse and no In the present ISS NF scheme, relatively little transverse and no longitudinal muon cooling is required, while longitudinal muon cooling is required, while

MC plans require at least 6 orders of magnitude 6-D cooling. MC plans require at least 6 orders of magnitude 6-D cooling.

MC front-ends (p-driver, target, collection, cooling, acceleration to 30 MC front-ends (p-driver, target, collection, cooling, acceleration to 30 GeV) are well-suited to fill a NF storage ring, with good duty factor and GeV) are well-suited to fill a NF storage ring, with good duty factor and high intensity. high intensity.

The smaller emittance due to muon cooling can reduce the cost and The smaller emittance due to muon cooling can reduce the cost and difficulty of the RF and magnet systems of the NF. difficulty of the RF and magnet systems of the NF.

The incorporation of more cooling into NF designs can lead to better The incorporation of more cooling into NF designs can lead to better cooperation and faster progress for both machines. cooperation and faster progress for both machines.

A CW 8-GeV proton driver could provide sufficient beam power to do both A CW 8-GeV proton driver could provide sufficient beam power to do both simultaneously. simultaneously.

Recent muon cooling progress is very encouraging. Yonehara slides from Recent muon cooling progress is very encouraging. Yonehara slides from LEMC09 follow:LEMC09 follow:

Rol - July 21, 2009Rol - July 21, 2009 NuFact09NuFact09 44

Muons, Inc.

Progress of Helical Cooling Channel Design

K. YoneharaAPC, Fermilab

Muons, Inc.

LEMC’09 @ Fermilab, K. Yonehara 1

Work on HCC project• Test high pressure RF cavity• Study RF incorporating into helical magnet• Improve cooling performance

– Cooling factor & Transmission efficiency

• Phase space matching• Design 6D cooling demo experiment

A. Tollestrup, M. Chung

M. Lopez,M. Popovic

R. Abram,S. Kahn

Speakers in this workshop

Muons, Inc.

LEMC’09 @ Fermilab, K. Yonehara 2

Optimization of HCC

• In past, mainly optimized helical magnet– Adjust dispersion function

• Cooling decrements• Momentum slip factor

• In present, take into account RF parameters– Increase longitudinal acceptance

Muons, Inc.

LEMC’09 @ Fermilab, K. Yonehara 3

Clue: How to tune RF parameter• HCC has sufficient size of transverse phase space acceptance• HCC acceptance is limited by longitudinal phase space

Increase longitudinal acceptance by increasing RF bucket

Muons, Inc.

LEMC’09 @ Fermilab, K. Yonehara 4

RF bucket dependence

E = 31.4343 MV/m, ψ=160˚, Lrf = 100 mmE = 16.0 MV/m, ψ=140˚, Lrf = 50 mm

v = 400 MHz, κ=1.0, λ=1.0 mGH2 pressure = 200 atm (at room temp)

Transmission efficiency is improved by more than factor two

Old design New design

Muons, Inc.

LEMC’09 @ Fermilab, K. Yonehara 5

ΔE

[G

eV]

ΔE

[G

eV]

Transverse motionE = 31.4343 MV/m, ψ=160˚, Lrf = 100 mmE = 16.0 MV/m, ψ=140˚, Lrf = 50 mm

Particle loss

Muons, Inc.

LEMC’09 @ Fermilab, K. Yonehara 6

Six-Dimensional emittance evolution in new HCC

Old result

v = 400 MHz, κ=1.0, λ=1.0 mGH2 pressure = 200 atm (at room temp)

Cooling factor > 500 ~ 29 @ z = 100 m

Muons, Inc.

LEMC’09 @ Fermilab, K. Yonehara 7

Transverse vs Longitudinal phase space

• A 400 MHz HCC may be sufficient to accept the beam phase space after conventional frontend channel• If Luminosity estimation is correct we can reach 1034 even only HCC section (but reverse emittance exchange is still needed)

400 MHz200 MHz

800 MHz1600 MHz

400 MHz

800 MHz

1600 MHz

1032103310341035

(E)PIC

REMEX

Hi Emit

Lo Emit

Muons, Inc.

8

equi. emit

Parameter list

λ (m) κ b (T) b’ (T/m) bz (T) Erf (MV/m) φrf Lrf (mm)

400 MHz HCC 1.0 1.0 1.60 -0.55 -5.30 31.46 160 100

800 MHz HCC 0.6 1.0 2.67 -1.53 -8.84 32.58 160 60

1600 MHz HCC 0.3 1.0 5.33 -6.10 -17.7 32.53 160 30

Field parameter

Average momentum = 0.25 GeV/cGH2 pressure = 200 atm @ room tempDispersion factor = = 1.83Length of each channel = 100 m

RF cellRF length will be double to save RF powerFor instance, 400 MHz HCC, Lrf = 200 mm, Erf = 40 MV/m

HCC field can be produced withcorrection magnets (although itis not a final design)

LEMC’09 @ Fermilab, K. Yonehara 9

Muons, Inc.

High Pressure RF for HCC

HPRF can be operated in strong magnetic fieldsWe do not know how HPRF works under high rad conditionDopant gas will reduce electron density in the cavity

Muons, Inc.

LEMC’09 @ Fermilab, K. Yonehara 10

HPRF simulation

LEMC’09 @ Fermilab, K. Yonehara 11

Muons, Inc.

RF system in HCC

Traveling wave RF systemLrf = 50 mm, 400 MHz helical RFRequired RF power is ~2.5 GW/m!!The reason is that it has a couplinghole only at the center of cell window

By putting a magnetic coupling holes on side of cell, required power is SIGNIFICANTLY reduced down to ~40 MW/mField quality is also good (but it has a thinmetallic window)

First design Second design

Muons, Inc.

LEMC’09 @ Fermilab, K. Yonehara 12

Wedge shape RF system

L. Thorndahl tried further challenge!He designs a wedge shape RF systemAdvantage: Reduce peak E field Probably, reduce number of cellsChallenge: Asymmetric field distribution

Muons, Inc.

LEMC’09 @ Fermilab, K. Yonehara 13

Dielectric loaded RFCu/Steel

ceramics

Vaccum/H/He

Muons, Inc.

LEMC’09 @ Fermilab, K. Yonehara 14

Possible way to put RF power

RF powercoupling port

Muons, Inc.

LEMC’09 @ Fermilab, K. Yonehara 15

Next-to-do

• More tuning up• Design matching section• Study RF power issue• Push high pressurizing RF cavity test harder• Propose dielectric loaded RF test• Mechanical design of HCC

Muons, Inc.

LEMC’09 @ Fermilab, K. Yonehara 16

Conclusion• A 400 MHz HCC can be a first cooling• Achieve luminosity 1034 even without extra

cooling channel – but emittance exchange is still needed

• High pressure RF with dopant gas seems ok• HPRF with beam is crucial• Need to study RF power issue• Dielectric loaded RF test

Muons, Inc.

LEMC’09 @ Fermilab, K. Yonehara 17