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)
µCF with High Intensity Muon Beam
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
µCF with High Intensity Muon Beam
5) Applications of µCF Intense fusion neutron source
MUCATEX-ENEA design
d beam
productiontarget
D-T target
irradiated materials
µCF with High Intensity Muon Beam
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
RŮ0.7
RŮ1.0
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
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