future muon sources, university of huddersfield, 12/13 january 2015 iiaa welcome ! professor bob...

Future Muon Sources, University of Huddersfield, 12/13 January 2015

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Welcome !Professor Bob Cywinski

Dean of the Graduate SchoolandSpecial Adviser (Research) to the VC

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• £140m turnover• £300m benefit to the local

economy• Over 2,800 staff on payroll• 24,000 students studying

more than 400 degrees

• An international University– Students from over

130 countries– Delivering courses in

China, Hong Kong, India and Singapore

The University of Huddersfield


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• Top 10 for Teaching Excellence (The Sunday Times)• Top 10 for Student Satisfaction (NSS and ISB)• Top 10 for Employability (DELI)• Top 10 for Financial Sustainability• Top 10 of “Green” Universities• Top 10 for quality of buildings (category A)• Doubled research income and PG recruitment• Outstanding Employer status• Human Resources (HR) Excellence in Research Award, bestowed by the

European Commission• THES Entrepreneurial University of the Year (2012)• Two Queen’s awards (2013)• Guardian University Award Winner (2013)• THES University of the Year (2014)

The University of Huddersfield


IIAAThe University of Huddersfield


IIAAThe International Institute for Accelerator Applications


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Future Muon Sources

Professor Bob Cywinski

Dean of the Graduate SchoolSpecial Advisor (Research)

International Institute for Accelerator ApplicationsUniversity of Huddersfield


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Future (Surface) Muon Sources

Professor Bob Cywinski

Dean of the Graduate SchoolSpecial Advisor (Research)

International Institute for Accelerator ApplicationsUniversity of Huddersfield


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Physics

MagnetismSuperconductivitySurfacesFundamental physics

Materials

PolymersSemiconductorsHydrogen in metals

ChemistryMolecular dynamicsOxidesMuonium

BiologyBiologyProteins

Currently there are 300-400 muon beam users world-wide, with 255 signed-up members of the International Society for MuSR Spectroscopy (ISMS)

Surface muons for MuSR spectroscopy


IIAAMuon facilities world-wide

TRIUMFContinuous Beams

ISISPulsed (50Hz) Beams

PSIContinuous Beams

JPARCPulsed (25Hz) Beams


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Question: What do muon beam users want ?

Answer: Orders of magnitude more muon intensity and smaller muon beam dimensions

Why?

At current positron count-rates (up to 40kHz) a typical spectrum from a typical sample (of a few cm2) will take ~30min to collect with reasonable statistics

At all existing facilities, muon production is a sub-optimal compromise determined through consultation with other users of the proton drivers (symbiotic, parasitic, or complimentary?)

What do we need?

Parametric studies (as functions of temperature, magnetic field, pressure and/or sample concentration) can take days

Studies of small (mm2) samples (eg single crystals) can take even longer

Low energy muon studies of surface phenomena can take weeks


IIAADesigning the future

Cost Stand alone facilities or shared accelerator beams?

The Accelerator Linac, synchrotron, cyclotron, FFAG ? Energy, current, frequency ? Protons or other particles ?

Pion production target Material (graphite, beryllium, nickel, composite..) Geometry, volume, size

Beam conditioning Collection geometry, beam optics, cryogenic cooling, pulse shaping


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+

+

p pS S

S =0

High EnergyProton

Carbon orBerylliumNuclei

Pion

Muon

Neutrino

High EnergyProton

Carbon orBerylliumNuclei

Pion

Muon

Neutrino

4.1 MeV

= 26 ns

Pion production


IIAAPion production

Single pion production (threshold 280MeV)

Double pion production (threshold 600MeV)


IIAAProton Energy ?

Surprisingly our simulations show that higher energy protons do not necessarily produce more (surface) muons

A peak in muon production rate is observed just below 500 MeV

Increasing energy produces more pions in the forward direction and well outside the momentum range likely to be used by a decay beam


IIAAProton Energy ?

Surface muon production normalised to proton energy

Surface muon production normalised to number of interacting protons


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Tw(ns)

25

50

100

0 20 40 1008060

0.0

0.5

1.0

Rel

ativ

e µ

SR

asy

mm

etry

Transverse field, mT

Pulsed or CW operation?

The finite proton pulse width (eg 80ns at ISIS) limits the dynamic response of a µSR spectrometer at a pulsed source. There are no such limitations in CW

Synchrotron operation at 50Hz (eg ISIS) is inefficient for MuSR – it provides a measuring window of 20ms whilst only 20µs (ie 10τm) is needed (duty cycle =0.1%)

At a pulsed source the positron count rate (~40kHz at ISIS) is limited only by detector deadtime effects. Significant increases in countrate can therefore be achieved by increasing source intensity


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At a CW source only one muon can be allowed in the sample at a time. Long time beam-borne backgrounds are generally significantly higher than at a pulsed source (but can be reduced by the Muons on Request technique)

Muons on request (MORE) at PSI

Conventional muon spectrometers at PSI and TRIUMF already count at 25-40KHz. This is the maximum rate possible with CW operation and is governed by the muon lifetime.

However significant increases in muon beam intensity are important for small samples and LE muons

Pulsed or CW operation?


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Pion production targets should produce a high yield of pions and muons

Pion production rates are approximately independent of atomic number, although the production of other particles (neutrons, gammas) increases with Z. Low-Z materials minimize proton scattering

Particle/target interactions should generate little heat and targets should dissipate heat easily

Monolithic targets are not necessarily the best design – surface to volume ratio should be maximised, whilst the target size should be kept small

PHYSICAL REVIEW SPECIAL TOPICS - ACCELERATORS AND BEAMS 17, 034701 (2014 – Bungau et al)

Production targets


IIAAPossibilities

Gains in muon beam intensities can be made at existing facilities by improving target geometry and composition, and muon collection but:

(i) proton energies, repetition rate and current are fixed (ii) the fraction of protons taken by the pion production target, although negotiable, is also fixed (eg 4% at ISIS)

The greatest gains necessitate construction of a fully stand-alone facility:

(i) Proton energy ~400-500MeV, current 0.5-1mA (ii) Optimal target geometry, thickness and material

(Additionally an optimised pulsed muon source should have a repetition rate approaching 10kHz and a pulse width of ~30ns)

A dedicated proton driver unconstrained by parasitic uses of the proton beam will enable precise tailoring of beam/target assemblies, allowing smaller proton/muon beams, and more efficient pion/muon collection and will also facilitate the implementation of multiple muon production targets.

x10

x10


IIAAThe way forward? IIAA

ESS5MW

http:

//vi

meo

.com

/194

7580

1


IIAAThe way forward?

The foundation stone for the 1.7b€ European Spallation Source has just been laid after more than 25 years of design, redesign and political campaigning by 5000 European neutron beam users

There is much we can learn from the ESS (and SNS and J-Parc) campaigns

We need to build a strong science case, emphasising “impact” and the roles that muons can play in the “Grand Challenges”

We need to engage the wider muon community (fundamental physics, imaging, etc)

It may also be beneficial to engage with Fermilab and Brookhaven National Laboratory. Both have recently held workshops which have focussing upon muon production and MuSR facilities


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Session 1: Muon production and accelerator technologies

Session 2: Specialised beams

Session 4: Update and outlook from the Facilities

Session 3: Condensed matter µSR / New Techniques

Session 5: Novel applications of muons

Future Muon Sources 2015


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Thank You!

future muon sources, university of huddersfield, 12/13 january 2015 iiaa welcome ! professor bob...

Documents

muon production

muon intensity

vc iiaafuture muon sources

thes university

hz beams future muon

muon beam users worldwide

research award

international society