20-50 GeV Muon Storage Rings20-50 GeV Muon Storage Rings

C. Johnstone and G. ReesC. Johnstone and G. ReesMuTAC MeetingMuTAC Meeting

FermilabFermilabMarch 16, 2006March 16, 2006

Introduction: Muon Storage Rings for a Introduction: Muon Storage Rings for a Neutrino FactoryNeutrino Factory

Neutrino beam/ Storage Ring energiesNeutrino beam/ Storage Ring energies 20 and 50 (20 and 50 (maxmax) GeV) GeV Production StraightProduction Straight

Muon beam divergence*Muon beam divergence* 0.1/ 0.1/ 0.2/ 0.2/ Muon beam normalized emittance*Muon beam normalized emittance* 30,00030,000 mm- mm-

mrad (95%)mrad (95%) Momentum acceptanceMomentum acceptance 1%1%Note these two parameters dictate beam size in production straightNote these two parameters dictate beam size in production straight Peak magnetic field (assume NBTi SC)Peak magnetic field (assume NBTi SC) ~7T~7T Declination angle: 3 and 7x10Declination angle: 3 and 7x1033 km detector km detector ~10~10 and 36 and 36 Bunch train lengthBunch train length 400nsec (120 m)400nsec (120 m)

Overiding design Goal:Overiding design Goal: maximize muon decays in production straight or ratio of maximize muon decays in production straight or ratio of

production straight(s)/circumferenceproduction straight(s)/circumference

*small compared to neutrino beam divergence, rms ~1/*small compared to neutrino beam divergence, rms ~1/*assumes minimal, mainly transverse cooling*assumes minimal, mainly transverse cooling

Storage Ring DesignsStorage Ring Designs

RacetrackRacetrack 1 long production straight; 1 detector site1 long production straight; 1 detector site Supports both charge species of muon beams circulating in Supports both charge species of muon beams circulating in

opposite directions (if opposing straights are identical)opposite directions (if opposing straights are identical)

Isosceles Triangle RingIsosceles Triangle Ring 2 production straights per muon species; 2 detector sites2 production straights per muon species; 2 detector sites Supports only one charge speciesSupports only one charge species

Would require reversing polarity of ring, orWould require reversing polarity of ring, or Two rings (current proposal) one stacked above the otherTwo rings (current proposal) one stacked above the other

Feasibility I : U.S. Neutrino Factory Feasibility I : U.S. Neutrino Factory Storage ring designs - site specificStorage ring designs - site specific

50 GeV Fermilab Storage 50 GeV Fermilab Storage Ring: racetrackRing: racetrack 1313 declination angle declination angle circumference, C = 1753 mcircumference, C = 1753 m 39% ratio (1 prod str./C)39% ratio (1 prod str./C)

Design predicated on ~6T SC Design predicated on ~6T SC

arc dipolesarc dipoles

600 Feet Ring Vertical Drop

10 Feet Tunnel ceiling to floor

10 Feet Shielding above ring

50 Feet Undisturbed bottom layer of Galena Platteville

10 Feet For uncertainties in the above three numbers

680 Feet Total from Surface to Bottom of Galena Platteville

Feasibility II : U.S. Neutrino Factory Feasibility II : U.S. Neutrino Factory Storage ring designs - site specificStorage ring designs - site specific

20 GeV BNL Storage Ring: 20 GeV BNL Storage Ring: racetrackracetrack 1010 declination angle declination angle C = 358 mC = 358 m 35% ratio35% ratio

Design predicated on ~7T SC Design predicated on ~7T SC arc dipoles- (hence the short arc dipoles- (hence the short circumference achieved at 20 circumference achieved at 20 GeV)GeV)

Site concerns for 7 & 3 x10Site concerns for 7 & 3 x103 3 km km detectorsdetectors

Vertical depth (arcs << straights):Vertical depth (arcs << straights): Racetrack:Racetrack:

Isosceles triangle:Isosceles triangle:

Conclusion: relative depths of two similar circumference -Conclusion: relative depths of two similar circumference -triangular or racetrack - storage rings are very closetriangular or racetrack - storage rings are very close

CCCDepth 29.0)6.0(2)36sin(2

CCCCDepth 25.0)8.0(3)36sin(3)10sin(3

6000

km

7000 km 36

to 3 km site10surface

36

46

to 7 km site

20 and 50 GeV Current Design Overview20 and 50 GeV Current Design Overview

20 and 50 GeV lattice ring designs complete20 and 50 GeV lattice ring designs complete Arc: FODO cells with ~6T dipole fields: Arc: FODO cells with ~6T dipole fields:

7272 arc cells, combined-function magnets (triangle, for now) arc cells, combined-function magnets (triangle, for now) 9090 arc cells, separated-function, tunable magnets (racetrack arc cells, separated-function, tunable magnets (racetrack

design, for now)design, for now) Combined dispersion suppressor and matching sectionsCombined dispersion suppressor and matching sections Designed for MW intensities - warm bores of SCDesigned for MW intensities - warm bores of SC

Clad with Pb (absorbs 80% of eClad with Pb (absorbs 80% of e beam power) beam power) 1 cm of W @50 GeV will also sufficiently protect SC coils1 cm of W @50 GeV will also sufficiently protect SC coils

Production straight design: Production straight design: SC solenoids - minimize beam sizeSC solenoids - minimize beam size NC, 30 cm -bore quadrupoles - confines cryogenics to arcsNC, 30 cm -bore quadrupoles - confines cryogenics to arcs Permanent magnet ~30 cm bore quads appear feasiblePermanent magnet ~30 cm bore quads appear feasible Background sweep dipoles at ends of production straightsBackground sweep dipoles at ends of production straights

20 20 50 GeV upgrade; present status 50 GeV upgrade; present status

Isosceles: Isosceles: modify lattice + some magnet changes required; modify lattice + some magnet changes required; realignmentrealignment Muon/neutrino beam divergence fixed to 1/ Muon/neutrino beam divergence fixed to 1/ at both at both

energiesenergies

Racetrack: Racetrack: no changes: 50 GeV ring installed and can be operated @20 no changes: 50 GeV ring installed and can be operated @20

GeV; GeV; bores accommodate 20 GeV beam and increased internal bores accommodate 20 GeV beam and increased internal

shielding @50 GeVshielding @50 GeV Muon beam rms divergence increases from 0.1/Muon beam rms divergence increases from 0.1/ @20 GeV @20 GeV

to 0.2/to 0.2/ @50 GeV @50 GeV

These approaches are not specific to storage ring shapeThese approaches are not specific to storage ring shape

Triangular Muon Storage RingTriangular Muon Storage Ring

NeutrinosNeutrinos

± injections

Collimation, rf and tune change

End bend

≥ 22.43°Designs for 20 and 50 GeV to fit in same tunnel

C.Prior UKNF talk

now 50° to 60°

Racetrack Storage Ring Racetrack Storage Ring

Ring operates at 20 and 50 GeV – Arc dipoles powered at 2.5 and 6.3 T

Neutrinos

Neutrinos

± injections

Background sweep dipoles at end of each straight

Muon Decay and Muon Decay and Storage RingStorage Ring

Near DetectorR109

To F

ar

Det

ecto

r 2

To Far Detector 1

Muon Decay Ring(muons decay to neutrinos)

Far Detector 1Far

Detector 2

Neutrino Factory

Leaning towards a Leaning towards a triangular shape with triangular shape with two baseline two baseline experimentsexperiments

Racetrack shape also Racetrack shape also being pursuedbeing pursued

Potential dual far/near detector locationsPotential dual far/near detector locations

C. Prior, 1/25/06 ISS scoping study

# de

tect

or lo

cati

ons

Apex angle of storage ring triangle

12

Global Storage Ring ParametersGlobal Storage Ring Parameters

PARAMETERPARAMETER TRIANGLE TRIANGLE RACETRACKRACETRACK

20 : 50 GEV20 : 50 GEV 20 : 50 GEV 20 : 50 GEV

Circumference Circumference 1273 m 1273 m 1371 m 1371 m

Production straightProduction straight 2x~265 m (2x~21%) 2x~265 m (2x~21%) 496 m (36%)496 m (36%)

acceptance, acceptance, normalized, 95%normalized, 95% 4.8 4.8 mm-mrad (30 mm-mrad (30)) same same(beam emittance)(beam emittance)

rms prod divergence rms prod divergence 0.10/ 0.10/ : 0.12/ : 0.12/ 0.12/ 0.12/ : 0.19/ : 0.19/

Global Tune, Global Tune, x x / / yy 10.79 / 11.15 : 10.44 / 10.64 10.23 / 9.24 10.79 / 11.15 : 10.44 / 10.64 10.23 / 9.24

xmax/xmax/ymaxymax 117 m : 184 m 155 m / 167 m 117 m : 184 m 155 m / 167 m

Peak Field arcs Peak Field arcs 6.4T 6.4T 6.3T 6.3T

Peak Field prod straightPeak Field prod straight 4.3T : 6.4T* 4.3T : 6.4T* 0.2T** 0.2T**

* solenoids ** quadrupoles* solenoids ** quadrupoles

Magnetic components:Magnetic components: Racetrack:Racetrack:

Magnets, in particular SC arc magnets, will resemble design in Magnets, in particular SC arc magnets, will resemble design in feasibility I study – see figures belowfeasibility I study – see figures below

TriangleTriangle Vertical mounting of SC elements in vertical return arc looks difficultVertical mounting of SC elements in vertical return arc looks difficult

Should look at this aspect asapShould look at this aspect asap

Dipole (left) and cryostat design (right) for racetrack, Feasibility I Study

20 GeV Lattice Functions for Triangular 20 GeV Lattice Functions for Triangular Ring (Excluding Production Straights)Ring (Excluding Production Straights)

20/50 GeV Lattice for Racetrack Ring20/50 GeV Lattice for Racetrack Ring

Production Straight

Discussion IssuesDiscussion Issues

Number of bunch trains from n=1 @15 Hz to n=5 @50 Number of bunch trains from n=1 @15 Hz to n=5 @50 Hz (80 bunches, 5 ns intervals with trains separated by Hz (80 bunches, 5 ns intervals with trains separated by 100 ns)100 ns) Reduces beam loading power levels by a factor of 50/3 to Reduces beam loading power levels by a factor of 50/3 to

levels experienced in SNSlevels experienced in SNS Vertical depth Vertical depth circumference circumference # bunch trains# bunch trains

operationoperation Separate rings for Separate rings for stacked one above the other stacked one above the other

Interleave bunch trains – doubles the circumference of each ringInterleave bunch trains – doubles the circumference of each ring Reverse polarity of triangular ring or racetrackReverse polarity of triangular ring or racetrack Use opposite straight in racetrack Use opposite straight in racetrack Simultaneous Simultaneous beams are under discussion in racetrack beams are under discussion in racetrack

Again doubles circumference or halves number of bunch Again doubles circumference or halves number of bunch trains/speciestrains/species

Proton and Muon Bunch Trains proposed for the ISS Neutrino Factory Study

O O Proton driver booster ring (h=5) O O O Proton driver main ring (n=5) O O ΔT = 1-3 ns rms ΔT O O O Proton bunch train at target O O O O O T Muon bunch train after target O O O O O T Muon trains of 80 bunches T t

Bunch Trains continued 20 GeV muon accelerator T t T= mTrev ~ 25 to 50 μs , t = 400 ns m = number of turns of acceleration t 20/50 GeV μ+ decay ring circumf. 600 400 600 400 600 400 600 400 600 400 C = 1500 m (nanosec) 400 600 400 600 400 600 400 600 400 600 20/50 GeV μ- decay ring circumf.

General concernsGeneral concerns Emittance measurements:Emittance measurements:

Cannot be made accurately with a parallel beam – parameters Cannot be made accurately with a parallel beam – parameters multiply each other are ~ unchanging in prod. regionmultiply each other are ~ unchanging in prod. region

Cerenkov gas + windows may be disruptive in a ring; large Cerenkov gas + windows may be disruptive in a ring; large effect @20 GeV on a parallel beameffect @20 GeV on a parallel beam

Special straight needs to be designed for emittance Special straight needs to be designed for emittance measurements : expect 5% measurement of divergence which measurements : expect 5% measurement of divergence which is a combination of resolution and profile recognitionis a combination of resolution and profile recognition

Injection is difficult in a production-optics straightInjection is difficult in a production-optics straight injected simultaneously injected simultaneously consider reversing polarity of ring?consider reversing polarity of ring?

Vertical orientation and mounting of SC magnets in Vertical orientation and mounting of SC magnets in triangular ring mechanically challenging?triangular ring mechanically challenging?

Fringe fieldsFringe fields TrackingTracking Specialty insertion for aberrations from sextupoles+fringe Specialty insertion for aberrations from sextupoles+fringe

fieldsfields Can use return straight in racetrack; harder in triangle latticeCan use return straight in racetrack; harder in triangle lattice

Recommendations for Future WorkRecommendations for Future Work

Survey of potential detector sites with angular ranges Survey of potential detector sites with angular ranges covered by triangular and racetrack storage rings, covered by triangular and racetrack storage rings, respectively – preliminary survey donerespectively – preliminary survey done

Kicker and Abort system and beam gaps, interleaving – Kicker and Abort system and beam gaps, interleaving – under discussionunder discussion

Chromatic correction (sextupoles) in triangular ringChromatic correction (sextupoles) in triangular ring Momentum acceptance and matching to FFAG acceleratorsMomentum acceptance and matching to FFAG accelerators

Mechanical design for vertical mounting of SC magnetsMechanical design for vertical mounting of SC magnets Design and comparison of injectionDesign and comparison of injection

In production straightIn production straight Optimized “opposing” straight in racetrackOptimized “opposing” straight in racetrack

Emittance measurement design and accuracyEmittance measurement design and accuracy Tracking with fringe fieldsTracking with fringe fields