muon colliders

MCTF

Steve Geer SLAC/LBNL November, 2009 1

Muon Colliders

MCTF

Physics Landscape


MCTF

Decision Tree


Pierre Oddone

0.5 TeV e+e-

3 TeV e+e-

3-4 TeV +-

MCTF

Muon Collider Motivation

If we can build a multi-TeV muon collider it’s an attractive option because muons don’t radiate as readily as electrons (m / me ~ 207):

- COMPACTFits on laboratory site

- MULTI-PASS ACCELERATIONCost Effective (e.g. 10 passes → factor 10 less linac)

- MULTIPASS COLLISIONS IN A RING (~1000 turns)Relaxed emittance requirements & hence tolerances

- NARROW ENERGY SPREADPrecision scans

- TWO DETECTORS (2 IPs)-Tbunch ~ 10 s … (e.g. 4 TeV collider)

Lots of time for readoutBackgrounds don’t pile up

- (m/me)2 = ~40000Enhanced s-channel rates for Higgs-like particles


CO

ST

PH

YS

ICS

MCTF

Muon Colliders are Compact


4 TeV

0.5 TeV3 TeV

MCTF

Narrow Energy Spread

Beamstrahlung in

any e+e- collider

E/E 2


Shiltsev

MCTF

Challenges

● Muons are born within a large phase space ( → )

- To obtain luminosities O(1034) cm-2s-1, need to reduce initial phase space by O(106)

● Muons Decay (0 = 2s) - Everything must be done fast

→ need ionization cooling- Must deal with decay electrons- Above ~3 TeV, must be careful about

decay neutrinos !


MCTF

Muon Collider Schematic


Proton source: Upgraded PROJECT X (4 MW, 2±1 ns long bunches)

1021 muons per year that fit within the acceptance of an accelerator

√s = 3 TeV Circumference = 4.5kmL = 3×1034 cm-2s-1 /bunch = 2x1012

(p)/p = 0.1%* = 5mmRep Rate = 12Hz

MCTF

Target Facility Design


• A 4MW target station design study was part of “Neutrino Factory Study 1” in 2000 ORNL/TM2001/124

• Facility studied was 49m long = target hall & decay channel, shielding, solenoids, remote handling & target systems.

• Target: liquid Hg jet inside 20T solenoid, identified as one of the main Neutrino Factory challenges requiring proof-of-principle demonstration.

• Beam dump = liquid Hg pool. Some design studies started.

4MW Target Station Design

V. Graves, ORNL

T. Davonne, RAL

Proton Hg Beam Dump

MCTF

MERcury Intense Target Experiment (MERIT)


• Proof-of-principle demonstration of a liquid Hg jet target in high-field solenoid ran at CERN PS in Fall 2007.

• Successfully demonstrated a 20m/s liquid Hg jet injected into a 15T solenoid, & hit with a suitably intense beam (115 KJ / pulse !).

• Results suggest this technology OK for beam powers up to 8MW with rep. rate of 70Hz !

Hg jet in a 15T solenoidMeasured disruption length

= 28 cm

1 cm

MCTF

Front-End Specifications


Parameter Drift Buncher Rotator Cooler

Length (m) 56.4 31.5 36 75

Focusing (T)

2 2 2 2.5 (ASOL)

RF f (MHz) 360 240 240 202 201.25

RF G (MV/m)

0 15 15 16

Total RF (V) 126 360 800

± →

/p within reference acceptance = 0.085 at end of cooler→ 1.5 1021 μ/year

MCTF

Front-End Simulation Results


Neuffer

MCTF

Ionization Cooling


Must cool fast (before muons decay)

Muons lose energy by in material (dE/dx). Re-accelerate in longitudinal direction reduce transverse phase space (emittance). Coulomb scattering heats beam low Z absorber. Hydrogen is best, but LiH also OK for the early part of the cooling channel.

Cooling

XmEEds

dE

dsd NN

03

2

2 2

)GeV 014.0(1

Heating

MCTF

MuCool


Developing & bench testingcooling channel components

MuCool Test Area at end of FNAL linac is a unique facility:

-Liquid H2 handling-RF power at 805 MHz-RF power at 201 MHz-5T solenoid (805 MHz fits in bore)-Beam from linac (soon)

Liq. H2 absorber

MTA42cm Be RF window

New beamline

MCTF

RF in Magnetic Field: 805 MHz Results


Peak Magnetic Field in T at the Window

>2X Reduction @ required field

Data reproducible & seem to follow universal curve.

Possible solutions:-special surfaces (e.g. beryllium)-Surface treatment (e.g. ALD)- Magnetic insulation

Effect is not seen in cavities filled with high pressure hydrogen gas (Johnson & Derbenev) – possible solution (but needs to be tested in a beam – coming soon)

When vac. copper cavities operate in multi Tesla co-axial mag. field, the maximum operating gradient is reduced.

MCTF

MICE


Ionization Cooling

Instrumentation

Instrumentation

GOALS: Build a section of cooling channel capable of giving the desired performance for a Neutrino Factory & test in a muon beam. Measure performance in various modes of operation.

Multi-stage expt.

First stage being installed at purpose-built muon beam at RAL (first beam to hall March 2008).

10% cooling measured to ±1%. Anticipate completed ~2011/12

Beam Line Complete First Beam 3/08 Running now

PID Installed CKOV TOF EM Cal

First Spectrometer Spring 2010

Spectrometer Solenoid being assembled

MCTF

6D Cooling


RF

liquid H

2solenoid

MC designs require the muon beam to be cooled by ~ O(106) in 6D

Ionization cooling reduces transverse (4D) phase space.

To also cool longitudinal phase space (6D) must mix degrees of freedom as the cooling proceeds

This can be accomplished with solenoid coils arranged in a helix, or with solenoid coils tilted.

Palmer

Alexhin & Fernow

MCTF

6D Cooling Channel Scheme


Palmer

MCTF

6D Cooling Channel Development


Detailed Simulations for candidate 6D cooling schemes

Magnet develop-ment for 6D cooling channels

HCC magnet4 coil test

REQUIRES BEYOND STATE OF ART TECHNOLOGY → Ongoing R&D

FOFO Snake - AlexhinHelical Cooling Channel- Muons Inc.

MCTF

Final Cooling


When the emittance is very small, to continue cooling we need very high field solenoids (to continue winning against scattering)

For fields up to ~50T, the final luminosity is ~ prop-ortional to the solenoid field at the end of the channel.

For higher fields we no longer expect to continue to win (limited by beam-beam tune shift).

MCTF

The Promise of HTS


10

100

1000

10000

0 5 10 15 20 25 30 35 40 45 Applied Field (T)

JE (

A/m

m²)

YBCO Insert Tape (B|| Tape Plane) YBCO Insert Tape (B Tape Plane) MgB2 19Fil 24% Fill (HyperTech) 2212 OI-ST 28% Ceramic Filaments NbTi LHC Production 38%SC (4.2 K) Nb3Sn RRP Internal Sn (OI-ST) Nb3Sn High Sn Bronze Cu:Non-Cu 0.3

YBCO B|| Tape Plane

YYBBCCOO BB TTaappee PPllaannee

2212

RRRRPP NNbb33SSnn

BBrroonnzzee NNbb33SSnn MgB2

NNbb--TTii SSuuppeerrPPoowweerr ttaappee uusseedd iinn rreeccoorrdd bbrreeaakkiinngg NNHHMMFFLL iinnsseerrtt ccooiill 22000077

1188++11 MMggBB22//NNbb//CCuu//MMoonneell CCoouurrtteessyy MM.. TToommssiicc,, 22000077

427 filament strand with Ag alloy outer sheath tested at NHMFL

Maximal JE for entire LHC Nb Ti strand production (CERN-T. Boutboul '07)

CCoommpplliieedd ffrroomm AASSCC''0022 aanndd IICCMMCC''0033 ppaappeerrss ((JJ.. PPaarrrreellll OOII--SSTT))

44554433 ffiillaammeenntt HHiigghh SSnn BBrroonnzzee--1166wwtt..%%SSnn--

00..33wwtt%%TTii ((MMiiyyaazzaakkii--MMTT1188--IIEEEEEE’’0044))

MCTF

HTS Solenoid R&D


NHMFL test coil LBL Test Coil

FNAL test cable. Test degradation of Jc in the cabling process

MCTF

Acceleration


0.1 1 2 5 10 20 50

AVERAGE GRADIENT (MV/m)

MU

ON

SU

RV

IVA

L F

RA

CT

ION

Bogacz

0.2

0.4

0.6

0.8

1.0

Accelerating muons from 3 GeV to 2 TeV

Example: TESLA cavities: Real estate gradient ~31 MV/m → 97% survival

● Early Acceleration(to 25 GeV ?) couldbe the same as NF.Needs study.

● Main Acceleration –

Attractive Candidates- RLAs (extension of NF accel. scheme ?) - Rapid cycling synchrotron – needs magnet R&D- Fast ramping RLA

● Options needstudy → particletracking, collectiveeffects, cavityloading, ...

MCTF

Collider Ring

• Muons circulate for ~1000 turns in the ring

• Need high field dipoles operating in decay back-grounds → R&D

• First lattice designs exist

New ideas → conceptual designs for various options

Comparison of different schemes, choice of the baseline

Detailed lattice design with tuning and correction “knobs”

Dynamic aperture studies with magnet nonlinearities, misalignments and their correction

Transient beam-beam effect compensation

Coherent instabilities analysis

WE ARE HERE

DE

SIG

N P

RO

CE

SS


MCTF

Neutrino Radiation


With L ~ E2 →

OK at √s = 1 TeV OK at √s = 3 TeV if D = 200m Above 3 TeV need to pay attention (wobble

beam, lower *, higher Bring , … )

MCTF

Background from Muon Decay


As the decay electrons respond to the fields of the final focus system they lose 20% of their energy by radiating on average 500 synchrotron photons with a mean energy of ~500 MeV … & are then swept out of the beampipe.

2 x 1012 muons/bunch 2 x 105 decays/m Electron decay angles O(10) rad Mean electron energy = 700 GeV

Mean energy= 700 GeV

2 2 TeV Collider

Electron Energy (GeV)

0 500 1000 1500 2000

Num

ber

of D

ecay

s

- → e- e

MCTF

Detector Backgrounds


Muon Collider detector backgrounds were studied actively ~10 years ago (1996-1997). The most detailed work was done for a 22 TeV Collider → s=4 TeV.

Since muons decay (2TeV=42ms), there is a large background from the decay electrons which must be shielded.

The electron decay angles are O(10) microradians – they typically stay inside the beampipe for about 6m. Hence decay electrons born within a few meters of the IP are benign.

Shielding strategy: sweep the electrons born further than ~6m from the IP into ~6m of shielding.

MCTF

Background Simulations


• Shielding design group & final focus design group worked closely together & iterated

• Used two simulation codes (MARS & GEANT), which gave consistent results

• Shielding design & simulation work done by two experts (Mokhov & Stumer) in great detail, & involved several person-years of effort.

MCTF

Final Focus Setup


Fate of electrons born in the 130m long straight section: 62% interactupstream of shielding, 30% interact in early part of shielding, 2% interact in last part, 10% pass through IP without interacting.

MCTF

IP Region


MCTF

More Shielding Details


r=4cm

Z=4m

Designed so that, viewed from the IP, the inner shielding surfaces are not directly visible.

MCTF

4 TeV Collider Backgrounds


Background calculations & shielding optimization was performed using(independently) MARS & GEANT codes … the two calculations were inbroad agreement with each other (although the designs were different in detail).

Results from Summer 1996

GEANT MARSI. Stumer N. Mokhov

MCTF

4 TeV Collider Backgrounds


r (cm) n p e 5 2700 120 0.05 0.9 2.3 1.7

10 750 110 0.20 0.4 0.7

15 350 100 0.13 0.4 0.4

20 210 100 0.13 0.3 0.1

50 70 120 0.08 0.05 0.02

100 31 50 0.04 0.003 0.008

calo 0.003

muon 0.0003

GEANT (I. Stumer) Results from LBL Workshop, Spring 1997

Particles/cm2 from one bunch with 2 1012 muons (2 TeV)

MCTF

Occupancies in 300x300 m2 Pixels


TOTAL CHARGED

MCTF

Vertex Detector Hit Density


Consider a layer of Silicon at a radius of 10 cm: GEANT Results (I. Stumer) for radial particle fuxes per crossing:

750 photons/cm2 2.3 hits/cm2

110 neutrons/cm2 0.1 hits/cm2

1.3 charged tracks/cm2 1.3 hits/cm2

TOTAL 3.7 hits/cm2

0.4% occupancy in 300x300 m2 pixels

MARS predictions for radiation dose at 10 cm for a 2x2 TeV Collider comparable to at LHC with L=1034 cm-2s-1

At 5cm radius: 13.2 hits/cm2 1.3% occupancy

For comparison with CLIC (later) … at r = 3cm hit density about ×2 higher than at 5cm → ~20 hits/cm2 → 0.2 hits/mm2

MCTF

Pixel Micro-Telescope Idea


S. Geer, J. Chapman: FERMILAB-Conf-96-375

Photon & neutron fluxes in inner tracker large but

mean energies O(MeV) & radial fluxes ~ longitudinal fluxes ( isotropic)

Clock 2 layers out at variable clock speed (tomaintain pointing) &take coincidence.

Blind to soft photon hits& tracks that don’t come

from IP

MCTF

Pixel Micro-Telescope Simulation - 1


MCTF

Pixel Micro-Telescope Simulation - 2


MCTF

TPC


Exploit 10s between crossings

Large neutron flux – gas must not contain hydrogen: 90% Ne + 10% CF4

Vdrift = 9.4 cm/s with E = 1500 V/cm. Ion buildup E/E = 0.7%

Cut on pulse height removes photon & neutron induced recoils

V. Tchernatine

MCTF

Calorimeter Backgrounds


Electromagnetic: Consider calorimeter at r=120 cm, 25 r.l. deep, 4m long,22 cm2 cells:

GEANT 400 photons/crossing with <E> ~1 MeV <ETower>~400 MeV

E ~ (2<n>) <E> = 30 MeV

For a shower occupying 4 towers: <E> = 1.6 GeV and E = 60 MeV

Hadronic: Consider calorimeter at r=150 cm, 2.5m deep (~10), covering30-150 degrees, 55 cm2 cells:

<ETower> ~ 400 MeV

E ~ (2<n>) <E> = O(100 MeV)

These estimates were made summer 1996, before further improvements tofinal focus + shielding reduced backgrounds by an order of magnitude … so guess background fluctuations reduced by 3 compared with above.

MCTF

Bethe-Heitler Muons (Z Z+-)

Special concern: hard interactions (catastrophic brem.) of energetic muons travelling ~parallel to the beam, produced by BH pair production.

Believe that this back-ground can be mitigated using arrival-times, pushing calorimeter to larger radius, & spike removal by pattern recognition … but this needs to be simulated


MCTF

Comparison with CLIC


• We are not yet in a position to make an apples-to-apples comparison with CLIC, but …..

hits/mm2/bunch train

30mm O(1) hit/mm2/bunch train

FROM CLIC Machine-Detector interface studies:

CLICNOT AN APPLES-to-APPLES COMPARISON … BUT … Background hit densities appear to be similar to MC … so there may be many detector design issues in common between the 2 machines

Note: CLIC shielding cone= 7o c.f. 20o for MC (but we hope to improve on this)

MCTF

MC R&D – The Next Step

• In the last few years MC-specific R&D has been pursued in the U.S. by Neutrino Factory & Muon Collider Collaboration (NFMCC) & Muon Collider Task Force (MCTF)

• Last December the NFMCC+MCTF community submitted to DOE a proposal for the next 5 years of R&D, requesting a greatly enhanced activity, aimed at proving MC feasibility on a timescale relevant for future decisions about multi-TeV lepton colliders.


MCTF

NFMCC/MCTF Joint 5-Year Plan

● Deliverables in ~5 years:-Muon Collider Design Feasibility Report- Hardware R&D results → technology choice- Cost estimate- Also contributions to the IDS-NF RDR

● Will address key R&D issues, including- Maximum RF gradients in magnetic field- Magnet designs for cooling, acceltn, collider- 6D cooling section prototype & bench test- Full start-to-end simulations based on technologies in hand, or achievable with a specified R&D program

● Funding increase needed to ~20M$/yr(about 3x present level); total cost 90M$


MCTF

R&D – Ongoing

NFMCC/MCTF HISTORY & FUTURE

PROPOSAL


MCTF

Anticipated Progress

Key component m

odels

NOW5 YEARS


MCTF

Aspirational Bigger Picture


MCTF

Muon Collider R&D: A National Program


MCTF

Final Remarks

• Steady progress on the Front-End develop-ment for Muon Colliders

- Cooling channel design concepts- NF R&D (IDS-NF, MERIT, MICE, … )

• The time has come to ramp up the Muon Collider specific R&D → a National Program

• There are many challenges to be overcome

- RF in magnetic fields & 6D Cooling Channel

- Cost effective acceleration scheme- Collider Ring- Detector/Backgrounds optimization

• The incentive to meet these challenges is great → “5 Year Plan” → Design Feasibility Study


MCTF

3

4

4 GeVNF

25 GeVNF

Illustrative Staging Scenario

4MW multi-GeVProton Source

Accumulation &Rebunching

Steve Geer CERN Neutrino Workshop October 1-3, 2009 50

MCTF

Muon Collider Parameters


muon colliders

Documents

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liquid hg jet target