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Muon Catalyzed Fusion (µCF)

NuFact02 4 July 2002 Imperial College, London. Muon Catalyzed Fusion (µCF). K. Ishida (RIKEN) Principle of µCF Topics D2/T2 α-sticking, dtµ formation T2 tt-fusion, He accumulation µCF with high intensity muon beams in collaboration with

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Muon Catalyzed Fusion (µCF)

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  1. NuFact024 July 2002Imperial College, London Muon Catalyzed Fusion (µCF) • K. Ishida (RIKEN) • Principle of µCF • Topics • D2/T2α-sticking, dtµ formation • T2 tt-fusion, He accumulation • µCF with high intensity muon beams • in collaboration with • K. 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, 6RAL • present address *KEK, **U. Tohoku

  2. 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

  3. µCF (Motivation) • Exotic atoms and molecules • atomic physics in small scale • rich in few body problems • dt fusion and alpha-sticking • dtµ levels and formation • atomic 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) • vs • fusion output (17.6 MeV x 200?) • very close to breakeven

  4. Maximizing µCF Cycle • Observables • (1) Cycling rate lc（↑）(vs l0: muon life) • rate for completing one cycle • dtµ formation tµ + D2 →[(dtµ)dee] • (2) Muon loss W(↓） • muon loss per cycle • muon sticking to a-particle is the main loss • Number of fusion per muon • Yn = φλc/λn = １／[(λ0/φλc)+W]（↑）

  5. Present status of µCF understanding • dtµ molecule formation • unexpectedly high dtµ formation rate (109 /s) was understood • by Vesman mechanism of resonant molecular formation • still many surprises • density dependence • low temperature & solid state effect

  6. n free muon (~10keV) ws0:Theory - m 14.1MeV ws :Theory 0 ~0.9% w s initial sticking: 3.5MeV a thermalized am a R~0.35 effective sticking: 0 =(1-R) w w s s - m reactivation Present status of µCF understanding • am Sticking probability • main source of muon loss from µCF cycle • discrepancy between theory and experiments

  7. Muon to alpha sticking and X-rays • Main loss process of muonsW = ωs + ... • Ultimate obstacle for µCF（Yn < 1/ωs) • Previous experiments: determine W from • fusion neutron and subtract possible other losses • Final Sticking（← neutron yield） • ws = (1-R) ws0 • Initial sticking ws0 ← dt-fusion in dtm • Reactivation R ← am (3.5MeV) atomic process • X-ray measurement • Y(Ka) = gKaws0, Y(Kb) = gKbws0 • Direct measurement of initial sticking ws0 • am excited states and its time evolvement （Kb/Karatio, Doppler width)

  8. µCF at RIKEN-RAL Muon Facility Proton beam line • 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) Slow µ µA* etc µSR µCF experiment

  9. 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)

  10. Muon to alpha sticking • Observation of x-rays from ma sticking under huge bremsstrahlung b.g. • with intense pulsed muon beam at RIKEN-RAL • Y(Ka),Y(Kb): Ka,Kb x-ray per fusion

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

  12. Theories ~’88 RIKEN-RAL M. Kamimura (EXAT98) ws0 Increased Ionization PSI (Ct=0.04%) PSI-87 PSI-84 LAMPF-92 Result of X-ray and neutron measurement • Effective sticking ws (0.52%) < theoretical calculations (0.60%) • X-ray yield Yx(Ka) (0.27%) ~ calc.

  13. a-stiking • Understanding the result • (1) ionization from n≧3 are much faster than radiative transitionor • (2) initial sticking to n≧3 only is anomalously smaller (???) • next step • improving sticking x-ray data from ddm[PSI], ttm[RIKEN] to compare reactivation effect Ionization n>3 effective sticking ws =0.52％ < calc 0.6％ ma Ka X-ray Yx(Ka) 0.27％ ~ calc Y(Kb)/Y(Ka) =7+-1% <<calc(12%) 0.09% n=3 g K b 2p 0.03% 2s g K a 0.10% 1S 0.68% Excita- Deexcita- tion tion Initial am Effective Sticking Sticking w 0 s

  14. µ Muon transfer to helium-3 a t • (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 rates • radiative & non-rad decay • [Kamimura, KEK/RIKEN] • fusion in d3Hem(Dubnaa, PSI)

  15. µCF in pure T2 • 1) tt-fusion at very low energy • t + t →α+n+n(Q=14MeV) • one neutron carries more energy • than statistical dist. • strong am 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 am Ka

  16. dtµ, ddµ formation (Nonequilibrium and ortho/paraeffect) • Effect of D2, DT, T2 molecular composition • in dtµ-formation • tµ + 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 • λdtµ0,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 proton • Ortho vs normal: 15~30% reduction in ddµ formation • first indication of ortho-para effect • Opposite to a simple theory based on gas model D2+T2 D2+T2+DT λc E2(E-ΔE) d p µ E1(ΔE)

  17. µCF by other groups • PSI • strongest muon beam • fusion neutron, ion chamber, X, g, ... • TRIUMF • thin solid layer target, energetic dµ, tµ • Dubna • fusion neutron, high temperature, high pressure, H/D/T mixture • LAMPF • fusion neutron, high temperature, high pressure

  18. µCF and exotic atoms Conferences • International Conference on mCF • 22-26 April, 2001 (Shimoda, Japan) was hosted by RIKEN • ~100 participants • following Tokyo (1986), Leningrad(1987), • Florida(1988), Oxford(1989), Wien(1990), • Uppsala (1993), Dubna (1995), Ascona (1998) • there will be EXA02 in Wien in Nov

  19. µCF with High Intensity Muon Beam • １）Measurement and control of µCF with expanded target condition • （dtµ formation, a sticking) • high temperature, high density D/T target • naturally more µCF expected • plasma (reducing dE/dx) • atomic and molecular states • (vibrational & rotational levels by laser, ortho-para)

  20. ma Ka Kb µCF with High Intensity Muon Beam • ２）Precise measurement of X-rays • with improvement of beam, detectors, and target system • 1) X-ray intensity ratio（Ka, Kb, Kg, L) • transition between levels • 2) Doppler shift • αμ velocity（dE/dx） • 3) 2keV dµ, tµ Ka X-rays • q1s problem, radiationless transition • Detectors： • pileup　→ segmentaiton (Ge ball, Strip Si)、flash ADC • energy resolution　→diffraction spectrometer, calorimeter • low energy（2keV）　→thin window（or solid layer） • Intense muon beam • sharp and monochromatic beam -> good S/N ratio

  21. MuCF with High Intensity Muon Beam • 3) exotic (am)+ beam extraction and interaction • For systematic study of atomic process and stopping power (dE/dx) • to solve am sticking mystery • Atomic collision of (am)+ was estimated • only by scaling from normal atomic collision • or purely by theoretical calculation • we can measure • reactivation、excitations (X-rays) • Estimation of (am)+ beam yield at RIKEN-RAL • 1000 m stop in (5cm x 5cm x 4 mg/cm2) • X 20 fusion/m (?) • X 0.01 (sticking) X 0.01 (spectrometer) • = 2 /sec (am)+ of 3.5MeV energy

  22. Exotic beams with µCF • 4) applications of µCF • keV µ- beam • extract 10keV µ- released after dt-fusion • [K. Nagamine, P. Strasser] solid D/T keV µ- collector incoming muons

  23. µCF with High Intensity Muon Beam • 5) Applications of µCF • Intense fusion neutron source MUCATEX-ENEA design d beam D-T target production target irradiated materials

  24. µCF with High Intensity Muon Beam • 6) µCF for power generation [K. Nagamine]

  25. Summary • with High Intensity Muon Source • further understanding of basic processes • precise X-ray measurement • towards break-even with extreme target conditions • more exotic beams (aµ beam, slow µ- etc) • generation of fusion neutrons & power

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