Muon Catalyzed Fusion (µCF)

Muon Catalyzed Fusion (µCF)

K. Ishida (RIKEN)

Principle of µCFTopics

D2/T2 　 α-sticking, dtµ formationT2 tt-fusion, He accumulation

µCF with high intensity muon beams

in collaboration withK. Nagamine1,2*, T. Matsuzaki1, S. Nakamura1**, N. Kawamura1*,Y. Matsuda1, A. Toyoda3*, H. Imao3, M. Kato4, H. Sugai4, M. Tanase4, K. Kudo5, N. Takeda5, G.H. Eaton6 1RIKEN, 2KEK, 3U. Tokyo, 4JAERI, 5AIST, 6RALpresent address *KEK, **U. Tohoku

NuFact02　 4 July 2002　 Imperial College, London

Principle of Muon Catalyzed Fusion (µCF)

1.Muon injected in D2+T2 mixture

behaving like heavy electron

2.Coulomb barrier shrinks in small dtµ molecule(nuclear distance ~ 1/200 of DT molecule)

3.Muon released after d-t fusion and find another d-t pair to fuse→Muon working as catalyst of d-t fusion

d t

μ-tμ

dμ

μdt μ

nα

μ

freemuon

muontransfer(~5 10x -9 )s

muonicmoleculeformation (~5 10x -9 )s

nuclearfusion(~10 -12 )s

muonic atomformation(~10 -11 )s

α stickingωs

0~0.9%

reactivation( ~0.35)R

recycle(~99.5%)

αμ17.6 MeV x ?

energy output

cost for muon

production~5.3 GeV

injectedmuon d

ddμ

tt μ

Kα/K β-X ray

14MeVneutron

compositmolecule

μ

αμμ

3Heμ

3Heμ

µCF (Motivation)

Exotic atoms and moleculesatomic physics in small scalerich in few body problems

dt fusion and alpha-stickingdtµ levels and formationatomic collisions, muon transfer

cooperation between experiment and theory~40%:60% in µCF01 Conference

Prospect for applications (fusion neutron source, fusion energy)muon production cost (~5 GeV)

vsfusion output (17.6 MeV x 200?)

very close to breakeven

tμ

dμ

μdt μ

nα

μ

dtµformation

nuclearfusion

effectivestickingωs=(1- )R ωs

0

αμ17.6 MeV x Yn

energy output

injectedmuon

d

Kα/K β-X ray

14MeVneutron

3Heμ transfer

to He

Maximizing µCF CycleObservables

(1) Cycling rate c （↑） (vs 0: muon life)rate for completing one cycledtµ formation tµ + D2 →[(dtµ)dee]

(2) Muon loss W (↓ ）muon loss per cyclemuon sticking to α-particle is the main loss

Number of fusion per muon

Yn = φλc/λn = １／ [(λ0/φλc)+W] 　（↑）

tμ

dμ

μdt μ

nα

μ

dtµformation

nuclearfusion

effectivestickingωs=(1- )R ωs

0

αμ17.6 MeV x Yn

energy output

injectedmuon

d

Kα/K β-X ray

14MeVneutron

3Heμ transfer

to He

Present status of µCF understanding

dtµ molecule formationunexpectedly high dtµ formation rate (109 /s) was understood by Vesman mechanism of resonant molecular formationstill many surprises

density dependencelow temperature & solid state effect

ΔEν = ε11dtμ + ε0

tμ

tμ + (D2)νiKi Å® [(dtμ)11dee]*vfKf

tμ

d d dtμd

e-

e-

e-

e-

Å®Å{μ

μ

dtμU

R

D2

ΔEνε11dtμ

ε0tμ

ν = 0

ν = 1

ν = 2

J,ν = (0,0)

J,v=(1,1)ν = 0

[(dtμ)dee]

~0.3eV

Present status of µCF understanding

αμ Sticking probability

main source of muon loss from µCF cycle

discrepancy between theory and experiments

n

free muon(~10keV)

initial sticking:

thermalized effective sticking: s=(1-R) s

0

reactivation

3.5MeV

14.1MeV -

-

R~0.35

s0~0.9%

ωs0:Theory

ωs :Theory

Muon to alpha sticking and X-rays

Main loss process of muons 　 W = ωs + ...

　 Ultimate obstacle for µCF （ Yn < 1/ωs)

Previous experiments: determine W from

fusion neutron and subtract possible other losses

Excita-tion

Deexcita-tion

Ionization

1S

n=3

n>3

Thermalization

Transfer

dμ, tμ

InitialSticking αμ

γKα

ωs0

0.68%

0.10%

0.03% 2p2s

0.09%

: ReactivationR

γKβ

Effective Sticking

ωs = (1-R) ωs0

~ 0.35

Final Sticking （← neutron yield ） ωs = (1-R) ωs

0

Initial sticking ωs0 ← dt-fusion in dtμ

Reactivation R ← αμ (3.5MeV) atomic process

X-ray measurementY(Kα) = γKaωs

0, Y(Kβ) = γKβωs0

Direct measurement of initial sticking ωs0

αμ excited states and its time evolvement （ Kβ/Kαratio, Doppler width)

µCF at RIKEN-RAL Muon Facility

RIKEN-RAL Muon at ISIS (1994~) Intense pulsed muon beam (70ns width, 50 Hz)

800MeV x 200µA proton 20~150MeV/c µ+/µ- muon

105 µ-/s (55MeV/c)

µCF experiment

Proton beam line

µSR

Slow µ

µA* etc

µCF Experiment at RIKEN-RAL

Use of strong pulsed muon beam Tritium handling facility Detectors with calibration (fusion neutrons, X-rays) Stopping muon number(µe decay and µBe X-ray) Determine basic parameters and find the condition for improving efficiency

　 λc, Ｗ , X-ray emission　→　 α sticking probability and other loss processes　　　 reaction rates (dtµ formation rate, muon transfer etc)

0 100mm

Muon

90 400

Neutron detectors

µecounters

D-TTarget

Si(Li) X-raydetector

BeWindows

840

Superconductingmagnet

~~

~~

~~

Muon to alpha stickingObservation of x-rays from μα sticking under huge bremsstrahlung b.g.with intense pulsed muon beam at RIKEN-RAL Y(Kα),Y(Kβ): αβ x-ray per fusion

Brems b.g.

time

d.c. muon beam

gate time20µs 20ms

pulsed muon beam

Kα,Kβ-X rays

14MeVneutron

dtμ

nα

μ

μ

dμ

tμ

αinitial sticking

thermalized αμ

effective sticking:ωs=(1-R)ωs

0

reactivation3.5MeV

μ-

R~0.35

αμ

W = (1-λ0/λn)/Yn

λn, Yn

ωs = W - Wdd - Wtt ..

γ n

free μ−

initial sticking

effective sticking

TheoryExperiment

Present Status of Neutron and X-ray Measurements

Measure neutron (effective sticking)and αμX-ray (initial sticking)in the same experiment

Result of X-ray and neutron measurement

M. Kamimura(EXAT98)ωs

0Increased Ionization

PSI-87PSI-84LAMPF-92

PSI(Ct=0.04%)

RIKEN-RALTheories~’88

Effective sticking ωs (0.52%) < theoretical calculations (0.60%)

X-ray yield Yx(Ka) (0.27%) ~ calc.

α-stikingUnderstanding the result

(1) ionization from n≧3 are much faster than radiative transition 　 or

(2) initial sticking to n≧3 only is anomalously smaller (???)next step

improving sticking x-ray data from ddμ [PSI], ttμ[RIKEN] to compare reactivation effect

Excita-tion

Deexcita-tion

Ionization

1S

n=3

n>3

InitialSticking αμ

γK

ωs0

0.68%

0.10%

0.03% 2p2s

0.09%

γKβ

Effective Sticking

effective sticking ωs =0.52 ％ < calc 　 0.6 ％

μα α X-ray Yx(Ka) 0.27 ％~ calc

Y(Kβ)/ Y(Kα) =7+-1% <<calc(12%)

Muon transfer to helium-3　 (Another important loss process)

(x3Heµ)* (X=p,d,t) molecule formation (xµ) + He -> (xHeµ)theoretically predicted [Popov, Kravtsov]

first observed in D2+4He [KEK 1987]

then also in D2+3He [KEK 1989] and T2+3He [RIKEN 1996]

formation ratesradiative & non-rad decay

[Kamimura, KEK/RIKEN]

fusion in d3Heμ (Dubnaa, PSI)

α tµ

µCF in pure T2

1) tt-fusion at very low energyt + t →α+n+n(Q=14MeV)

one neutron carries more energy than statistical dist. strong αμ correlation (5He resonance state) 2) t3Heµ decay mode etc radiative decay branch (competition with particle decay)

~20% d3Heµ~50% d4Heµ>90% t3Heµ

3) sticking from ttµ fusion

t3Heµ αμ α

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dtµ, ddµ formation (Nonequilibrium and ortho/paraeffect)

Effect of D2, DT, T2 molecular composition

in dtµ-formationtµ + D2 -> [(dtµ)dee]

tµ + DT -> [(dtµ)tee]D2 + T2 2DT ⇄ proceeds gradually (~56 hours at 20K) after D+T mixture

gradual decrease of fusion neutron yield　　 λdtµ

0,D2 ／ 2 = 208 µs-1 (200 @ psi)

　　 λdtµ0,DT = 94 µs-1 (~10 @ psi) (preliminary!)

Ortho-para effect （ at RAL & TRIUMF ）[Toyoda, Ishida, Nagamine]

Ortho D2(J=0,2,..)& normal D2(ortho:para=2:1)

dµ + D2 -> [(ddµ)dee] fusion protonOrtho vs normal: 15~30% reduction in ddµ formationfirst indication of ortho-para effect

Opposite to a simple theory based on gas model

λc

D2+T2D2+T2+DT

p

d

µ

E1(ΔE)E

2(E

-ΔE

)

µCF by other groups

PSIstrongest muon beamfusion neutron, ion chamber, X, γ, ...

TRIUMFthin solid layer target, energetic dµ, tµ

Dubnafusion neutron, high temperature, high pressure, H/D/T mixture

LAMPFfusion neutron, high temperature, high pressure

µCF and exotic atoms Conferences

International Conference on μCF22-26 April, 2001 (Shimoda, Japan) was hosted by RIKEN

~100 participantsfollowing Tokyo (1986), Leningrad(1987), Florida(1988), Oxford(1989), Wien(1990), Uppsala (1993), Dubna (1995), Ascona (1998)

there will be EXA02 in Wien in Nov

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µCF with High Intensity Muon Beam

１） Measurement and control of µCF with expanded target condition（ dtµ formation, α sticking)

high temperature, high density D/T targetnaturally more µCF expected

plasma (reducing dE/dx)

atomic and molecular states (vibrational & rotational levels by laser, ortho-para)


２） Precise measurement of X-rayswith improvement of beam, detectors, and target system

1) X-ray intensity ratio （α β γ L)　　　 transition between levels

2) Doppler shift　　 αμ velocity （ dE/dx ） 3) 2keV dµ, tµ Kα X-rays q1s problem, radiationless transition

Detectors ：pileup 　→ segmentaiton (Ge ball, Strip Si) 、 flash ADCenergy resolution 　→ diffraction spectrometer, calorimeterlow energy （ 2keV ）　→ thin window （ or solid layer ）

Intense muon beamsharp and monochromatic beam -> good S/N ratio

μα α

β

MuCF with High Intensity Muon Beam

3) exotic (αμ)+ beam extraction and interactionFor systematic study of atomic process and stopping power (dE/d

x)to solve αμ sticking mystery

Atomic collision of (αμ)+ was estimatedonly by scaling from normal atomic collisionor purely by theoretical calculation

we can measurereactivation 、 excitations (X-rays)Estimation of (αμ)+ beam yield at RIKEN-RAL

1000 μ stop in (5cm x 5cm x 4 mg/cm2) X 20 fusion/μ (?)X 0.01 (sticking) X 0.01 (spectrometer)= 2 /sec (αμ)+ of 3.5MeV energy

muon D/T

(αμ)+

reaction and detection

α++

Exotic beams with µCF

4) applications of µCFkeV µ- beam

extract 10keV µ- released after dt-fusion[K. Nagamine, P. Strasser]

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keV µ- collector

incomingmuons

solidD/T


5) Applications of µCF Intense fusion neutron source

MUCATEX-ENEA design

d beam

productiontarget

D-T target

irradiated materials


6) µCF for power generation

0 ——

100 —— 1.8GeV

200 ——

300 —— 5.3 upper limit by sticking

400 ——

500 —— 8.8

600 ——

700 ——

800 ——

900 —— 15.8 economic break even

muon production cost(scientific break even)

fusion neutrons observationin µCF

effect of 3He, 4He producteffect of walleffect of D-D, D-T

µCF in new region of (φ,T,CT)complet eregeneration

RÅ®0.7

RÅ®1.0

φÅ®2.0RÅ®1.0

φ=1.2 ~1.4R=0.25

[K. Nagamine]

Summary

with High Intensity Muon Sourcefurther understanding of basic processes

precise X-ray measurement

towards break-even with extreme target conditions

more exotic beams (αµ beam, slow µ- etc)

generation of fusion neutrons & power

Muon Catalyzed Fusion (µCF)

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