Muon Catalyzed Fusion (μCF) - New progress and future planMuon Catalyzed Fusion (μCF) - New...
Transcript of Muon Catalyzed Fusion (μCF) - New progress and future planMuon Catalyzed Fusion (μCF) - New...
Muon Catalyzed Fusion (μCF) - New progress and future plan
K. Ishida (RIKEN)
IntroductionNew progress
Muonic molecule formation with ortho/para D2Prospect with intense muon beam
in collaboration withK. Nagamine1,2*, T. Matsuzaki1, S. Nakamura1**, N. Kawamura2,M. Iwasaki1, Y. Matsuda1, A. Toyoda3***, H. Imao3, M. Kato4, H. Sugai4, A. Uritani5, H. Harano5, G.H. Eaton6
1RIKEN, 2KEK, 3U. Tokyo, 4JAERI, 5AIST, 6RALpresent address * UC Riverside, **KEK, **U. Tohoku
NuFact-J 05研究会, 東工大 2005.06.09
What is muon catalyzed fusion (μCF)?After injection of muons into D/T mixture (or other hydrogen isotopes)
Formation of muonic atoms and muonic moleculesnucleus-nucleus separation ~1/200 of normal atom
In small dtµ molecule, Coulomb barrier shrinks and d-t fusionMuon released after d-t fusion
- muon works as catalyst - tµ
dµ
µdtµ
nα
µ
nuclearfusion
αμ
d14MeVneutron
3Heµ
Sticking
µCF (Motivation)Exotic atoms and molecules
atomic physics in small scalerich in few body physics problems
dt fusion and alpha-stickingdtµ energy levels and formationatomic collisions, muon transfer
Prospect for applications(fusion energy, fusion neutron source)
muon production cost (~5 GeV)vs
fusion output (17.6 MeV x 120)very close to breakeven
tµ
dµ
µdtµ
nα
µ
dtµformation
nuclearfusion
effective stickingωs=(1-R)ωs0
αμ 17.6MeV x Ynenergy output
injectedmuon
d
Kα/KβX-ray
14MeVneutron
3Heµtransfer toHe
Maximizing µCF efficiencyObservables
(1) Cycling rate λc ( ) (vs λ0: muon life)dtµ formation tµ + D2 [(dtµ)dee]
(2) Muon loss per cycle W ( )
muon sticking to α-particle is the main losstransfer to 3He is also important
Number of fusion per muon
Yn = φλc/λn = 1 / [(λ0/φλc)+W] ( )tµ
dµ
µdtµ
nα
µ
dtµformation
nuclearfusion
effective stickingωs=(1-R)ωs0
αμ 17.6MeV x Ynenergy output
injectedmuon
d
Kα/KβX-ray
14MeVneutron
3Heµtransfer toHe
Key process of µCF - dtµ formation
Auger formation : 106 /s (as slow as muon decay rate 0.45 x 106/s)tμ + D2 (dtμ) + D + e-
Resonant molecular formation : 106-109 /stμ + D2 ((dtμ) dee)
(dtµ binding energy ~ excitation of complex molecule)
(tµ energy to match the small energy difference)
Thus,large temperature dependencedependence on initial states(such as tμ spin state, D2 states)
We could change (enhance) μCF by controlling initial D2 states.
ΔE ν = ε11dtμ + ε0
tμ
tμ + (D2)νiKi → [(dtμ)11dee]*vfKf
tμ
d d dtμd
e-
e-
e-
e-
→+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 understanding of dtµ formationdtµ molecule formation
large formation rate (~109/s) by resonant formation mechanismis established (temperature dependence, etc)still many surprises
non-trivial density dependence even after normalizationthree-body effect : tµ + D2 + D2’ ((dtµ)dee) + D2’’
low temperature & solid state effectφ dependence applies even to solid
density φ
How about ddμ ?Same resonant formation process applies for ddμ formation in pure D2
Slower compared to dt-μCF, and with lower energy output per fusionStill, study should be done in parallel with study of dtμ
No need of tritiumSimpler cycling process (pure D2)
dμ + D2 [(ddμ)dee] In analogy to dtμ case,
temperature dependencedμ Hyperfine effect (F=1/2,3/2)D2 molecule effect
What has been known about ddμ formationResonant ddμ formation is nearly established in gas
fitting by theoretical curve givesprecision determination of shallow state binding energy in ddμ (-1.97 eV) which is comparable to the valueby precise three-body calculation
However, in liquid and solid, large deviation from theoretical curve
Ki=0
2
Ki=3 4
10 200
~5K
~20K~50K
F=3/2
F=1/2
共鳴位置とMaxwell分布
共鳴エネルギー[meV]
(ortho)
(ortho)(para)
Ortho- and para-D2 in μCFAll the measurements so far were with normal D2 (ortho:para = 2:1)Thus, the resonance condition for ortho- and para- are mixed.
Ortho-D2 (dd nuclear spin coupled with 0,2, ψ spin ψJ,v symmetry under ddexchangeonly J=even allowed)Para-D2 (simillary, for coupling with 1, J=odd allowed)
Resonance condition for each state should be separately measured.
Experimental setup @TRIUMFortho-D2 and normal-D2 preparationortho-para ratio analysis with Raman spectroscopyTarget cell (30cc liquid/solid, or 200cc pressurized gas)muon beam counters B1+B2me-decay electron counters E1-E8 (>50% solid angle)neutron detectors(NE213) N1-N4
0 10cm
target
muonbeam
gas preparation D2 target and detectors
Typical fusion neutron time spectra
fusion from resonantly formed ddμ (bfastcomponent) was reduced in ortho-D2
Result on ortho-para D2 μCFNormal D2 and Ortho-D2
Large effects (ddμ formation rate) were observed![A. Toyoda(2000) in Phys.Rev.Lett.24, 243401(2003) fusion protonsH. Imao(2004) in EXA-05, MSI-05 fusion neutrons]
Theoretical calculations agreed only with the gas result (15% increase in ortho-D2)The effect was opposite to theory in liquid and solid D2.
To understand the resultFor gas, the result was consistent with calculations based on idealistic non-interacting D2
Inversion in liquid/solid is key to understanding effect of condensed matter in μCFTheories are under development.
energy shift, broadening(still it is difficult to change the order of resonance in ortho/para)
phonon effect (solid only)New experimental run with ortho- and para-D2 for more temperature points(near liquid/gas boundary) is planned
Ki=0
2
Ki=3 4 2
10 20 300
~5K
~20K~50K
F=3/2
F=1/2
共鳴位置とMaxwell分布
共鳴エネルギー[meV]
(ortho)
(ortho)(para)
What about dtμ: theoretical calculations1. Idealistic gas modeltμ + D2 [(dtμ)dee]low temp. resonance only for para-D2
2. with Condensed matter effectunder development [Adamczak]
Even larger effect of ortho-para D2
expected!
[Faifman]
23K liquid
Planned experiment and expected effect
Prepare ortho-D2 and para-D2 and mix with T2
Enhancement or reduction of μCF in pure mixture followed by1. molecular equilibration process
D2 + T2 2DT (~68 hour in D/T(50%))tµ + D2 [(dtµ)dee]tµ + DT [(dtµ)tee] (λdtµ
0,D2>>λdtµ0,DT)
2. ortho-para equilibration by radiation effecto-p conversion by paramagnetic T atom~16 hours in D/T(50%) at 14K
Cycling Rateλc = 1/(τd+τt)=1/[ q1sCd/(λdtCt) + (3/4)/(λtμ
1,0Ct)+ 1/(λ0dtμ-D2(o,p)CD2(o,p) + λdtμ
0,DT CDT)]
full eq.
av. time waiting dμ->tμ transfer
av. time in tμ(F=1) stateav. time before dtμ formation
λc
Time [hr]
Towards highest fusion yieldT2 mixture with ortho-D2 at liquid/solid condition best candidate for maximum fusion yield in μCF1) Faster cycling rate
high density φ (liquid, solid)faster dtμ formation rate
D2 para-rich (or ortho-rich)2) Smaller W
high density (liquid/solid) high reactivation after μα stickingW ~ 0.6%
Typical neutron yield in liquid D/T ~110/muonif λc=260Yn = λc/λn = 1/(λ0/φλc + W) = 1/(0.45/1.25*260+0.006)=140
Preparation of ortho/para D2 gasOrtho D2 (established)
by ortho-para conversion with Al2O3/Cr2O3 catalysis
AnalysisRaman scattering spectroscopy
Para D2 (under study)selective absorption on Al2O3 at ~20K 99% para D2 is possible
D.A. Depatue and R.L. Mills, Rev. Sci. Instruments 39 (1968) 105
Para-to-Ortho Conversion
0
100
200
300
400
500
600
700
800
900
475 476 477 478 479 480 481 482 483 484 485
wavelength (nm)
coun
ts/4
0sec
normal
3hr
6hr
9hr
20hr
Our Target
ortho D2
normal D2
µCF at RIKEN-RAL Muon Facility
RIKEN-RAL Muon at ISIS (1994~)Intense pulsed muon beam(70ns width, 50 Hz)800MeV x 200µA proton20~150MeV/c µ+/µ- muon5x104 µ-/s (55MeV/c)
µCF experiment
Proton beam line
µSR
Slow µ (Matsuda)
µA* (Strasser)
µCF target and detectors
Cryogenic target : 1 c.c. liquid or solid D-TDetectors with calibration
fusion neutrons, X-rays, µe decay120 muon stops per pulse106 fusions/s
0 100mm
Muon
90 400
Neutron detectors
µe counters
D-T Target
Si(Li) X-ray detector
Be Windows
840
Superconducting magnet
~ ~
~ ~
~ ~ n
X-ray
μe
muonµCF setup
(RIKEN-RAL Port1)
Other ongoing studies of μCFUnderstanding mechanism and parameters of key processes1. Muon-to-alpha sticking loss
muon-to-alpha sticking x-rays2. Muon loss to accumulated 3He from tritium decay
tHeμ molecule formation and decay3. dtμ formaiton in wider and exotic target conditions
low temperature solid D/T, high density D/T, ortho-para D2
4. fusion in ttμparticle correlations in 4He-n-n exit channel
Intense muon beams will definitely contribute to these study of μCF1) efficient search of more and more target conditions2) short-lived extreme conditions (laser, plasma etc)3) better S/N4) exotic beams from μCF5) intense neutron source
SummaryA clear effect of ortho-para ratio was observed for ddμ formation in D2, which is the most important rate limiting process in μCF.
Even larger effect (and enhancement) is predicted for dtμ formation
This opens up possibility for enhancement of μCFby controlling initial molecular states.