Workshop on Instrumentation for Muon

Cooling Studies

Illinois Institute of Technology, November 10-11, 2000

Kenneth Long

Imperial College London

Prospects for a

High Intensity MuonFacility

at RAL

IIT-10Nov00 Prospects for High Intensity Muon Facility at RAL 1/17

Contents

• Beam instrumentation

→ Very high flux beam

→ Very low mass detectors

• µµµµ-beams for ννννFct R&D at RAL

→ Phase I: Cooling Demonstration

in the HEP Test-Beam (an

upgrade of MuScat?)

→ Phase II: A high intensity

bunched muon beam at RAL

... a high intensity muon beam for R&Dinto the ννννFct front end

IIT-10Nov00 Prospects for High Intensity Muon Facility at RAL 2/17

Instrumentation and thecooling channel

Energy loss

(Straggling)

Multiple Coulomb Scattering

Initial muonbeam Liquid H 2 absorber

Solenoid

Liquid H 2 absorber

Acceleration

Solenoid

RF cavity

RF cavityFinal muon

beam

IIT-10Nov00 Prospects for High Intensity Muon Facility at RAL 3/17

Instrumentation and the cooling channel

• Ionisation cooling relies on energy loss toreduce beam momentum

• Multiple Coulomb scattering results inlarger angular divergence as beam leavesabsorber

• RF cavity restores longitudinal momentum

Cooling channel consists of repetition ofabsorber and RF cavity in confining

solenoidal field

Ideal absorber for cooling channel has

• Large X0 and large dE/dx

• ‘Ratio’ dE/dx to X0 must allow cooling to‘beat’ heating

Liquid hydrogen proposed as X0 vs dE/dx hasbeen shown, in simulations, to cool

- Ionisation cooling of transverse emittance:

IIT-10Nov00 Prospects for High Intensity Muon Facility at RAL 4/17

Instrumentation and the cooling channel

http://www. fnal.gov/projects/muon_collider/nu-factory/subsys/ss-cooling/nuss-cooling.html

IIT-10Nov00 Prospects for High Intensity Muon Facility at RAL 5/17

Instrumentation and the cooling channel

• In FNAL design absorber is ~13 cm liquidhydrogen contained by 300 µµµµm aluminiumwindows

� L-H 2 →→→→ 1.5% X0, windows 0.9% X0

• Instrumentation must exploit existingmaterial or be very low mass. Must operatein presence of intense (dirty) muon beamand intense X-ray background from RFcavities.

• Cherenkov light from foils: Image ofintense beam, excellent timing. Can it bedone?

• Transition radiation from thin foil: Imageof intense beam and good timing. Can lightbe collected?

• Development of feedback: e.g. must ensurethat the RF cavities regenerate exactly themomentum lost in the absorbers.

- Brief outline of the challenge:

IIT-10Nov00 Prospects for High Intensity Muon Facility at RAL 6/17

The ννννFct World Needs aHigh Intensity Muon Beam!

Two classes of issue:

Basic physics:

• Important details of multiple Coulombscattering, dE/dx of low energy muons inmatter and straggling need to be measured(MuScat + upgrade)

Cooling demonstration:

• Even when the ‘basic physics’ measurementshave been made and encorporated intosimulations of the cooling channel it will benecessary to demonstrate that each piece ofthe cooling channel and its diagnostics andfeedback systems work both individually andas a SYSTEM!

Need to develop a ‘phased’ muon R&D facility

• Phase I: Address basic physics issues

• Phase II: Develop elements of andinstrumentation for cooling demonstration

IIT-10Nov00 Prospects for High Intensity Muon Facility at RAL 7/17

Muon beams for ννννFct R&D atRAL

Phase I: Basic Physics of Ionisation Cooling

• MuScat: Determine shape of tails ofmultiple Coulomb scattering

→ Precise determination of heating term

• Required:

→ Demonstration of principle of cooling

→ Measurement effect of straggling

→ Upgrade of MuScat

Transverse emittance cooling:

�

�

���

�

++++====⊥⊥⊥⊥

⊥⊥⊥⊥

⊥⊥⊥⊥ 02

N,

2

2N,

N,

1111X

x

dzdE

Edz

d

εεεεηηηη

ββββεεεε

εεεε

Fight between dE/dx and multiple scattering

Longitudinal emittance growth

Straggling �� �� Muons fall out of RF bucket

IIT-10Nov00 Prospects for High Intensity Muon Facility at RAL 8/17

Phase I: Basic Physics of Ionisation Cooling

- Case study:

• 50 cm liquid hydrogen absorber

µµµµInit

N,⊥⊥⊥⊥εεεε FinalN,⊥⊥⊥⊥εεεε

minN,

FinalN,

⊥⊥⊥⊥

⊥⊥⊥⊥====εεεεεεεε

R

• Assume ratio of initial emittance tominimum emittance is 4 and calculate R

1

1.5

2

2.5�

3�

3.5�

4

0

50�

100 150 200 250

pµ (MeV/c)

R

50 cm absorber

100 cm absorber

� Use muon beam of 75 - 100 MeV/cmomentum

IIT-10Nov00 Prospects for High Intensity Muon Facility at RAL 9/17

Phase I: Basic Physics of Ionisation Cooling

- Muons in HEP Test beam:80

0 M

eV/c

prot

ons

Low

ene

rgy

(~10

0 MeV

/c) m

uons

IIT-10Nov00 Prospects for High Intensity Muon Facility at RAL 10/17

Phase I: Basic Physics of Ionisation Cooling

10 m

Scintillating fibre tracker:

σσσσx ~ 0.2 mm

σσσσt ~ 150 ps

Possible layout for experiment to demonstrateprinciple of cooling and measure straggling

IIT-10Nov00 Prospects for High Intensity Muon Facility at RAL 11/17

Phase I: Basic Physics of Ionisation Cooling

- Position and momentum measurement:

2222N,

22xx xppxcm −−−−====⊥⊥⊥⊥εεεεµµµµ

Require to reconstruct

before and after the absorber

• Position and timing from scintillating fibretracking detectors

p = 150 MeV/c

1

10

10 2

0�

0.5�

1 1.5 2 2.5 3�

3.5�

4 4.5 5�

d (m)

σ(p)

/p (

%)

σ� t� = 0.1 ns

σ� t� = 0.2 ns

σ� t� = 0.5 ns

%1N,

N, <<<<⊥⊥⊥⊥

⊥⊥⊥⊥

εεεεσσσσ εεεε

Demonstration of principle of cooling looksfeasible with such a set-up

IIT-10Nov00 Prospects for High Intensity Muon Facility at RAL 12/17

Muon beams for ννννFct R&D atISIS

Phase II: A High Intensity Muon Beam

ISIS

800 MeV proton synchrotron

2.5 ×××× 1013 proton per pulse

100 ns pulses at 50 Hz

IIT-10Nov00 Prospects for High Intensity Muon Facility at RAL 13/17

Phase II: A High Intensity Muon Beam

IIT-10Nov00 Prospects for High Intensity Muon Facility at RAL 14/17

Phase II: A High Intensity Muon Beam

IIT-10Nov00 Prospects for High Intensity Muon Facility at RAL 15/17

P. Drumm

Pions at ISIS

• 800 MeV Protons from ISIS

• 2.5 ×××× 1013 protons per pulse at 1 Hz (i.e.one bunch in 50)

• 2 cm ∅∅∅∅ ×××× 5 cm long Graphite Target

• ~25 ππππ+/1000 protons �� �� 6 ×××× 1011 ππππ+ per pulse

• Capture ~20% �� �� 1 ×××× 1011 ππππ+ per pulse

• ~12% inside ±±±±25% momentum byte�� �� 1010 ππππ+ per pulse

Phase II: A High Intensity Muon Beam

IIT-10Nov00 Prospects for High Intensity Muon Facility at RAL 16/17

Phase II: A High Intensity Muon Beam

Muons at ISIS

• Decay/muon capture channel not yet studiedbut perhaps possible to keep between 10%and 50% of the muons:

� ~ 109 muons in 100 ns bunch

• Tight bunching possible by lowering RF fieldearly in acceleration cycle. Technique to besimulated in tracking calculations and testedin machine development period soon.

� Keep ~ 1% of muons if make a 10 ns bunch� ~ 107 muons in 10 ns bunch

• Design study: Of proton beam line, target,decay channel as well as mini-bunchingscheme now starting

Possible route to high intensity muon beam

- first ideas:

IIT-10Nov00 Prospects for High Intensity Muon Facility at RAL 17/17

Summary“Prospects for a High Intensity Muon Facility in

the UK”

Good!

Phase I: Basic Physics

• MuScat has made excellent start inmeasurement of ‘basic physics’ parametersof the ionisation cooling channel

• Need to develop MuScat to look at dE/dx,straggling and demonstration of theprinciple of cooling (perhaps in HEP TestBeam at RAL)

Phase II: High Intensity Muon Facility

• ISIS offers possibility to develop an intensebunched muon beam

• Need to develop ideas for provision of beamin parallel to ideas for targetry, capture andinstrumention

• Possibility to build towards an engineeringdemonstration of ionisation cooling