1. Muon Catalyzed Fusion (µCF) - Recent progress and future plan K. Ishida (RIKEN) Introduction dd  formation: wider range of temperature, phase and ortho/para ratio of D 2 dt  formation: first experiment with T 2 /ortho-D 2 mixture  CF with intense muon beam in collaboration with K. Nagamine 1,2,3, T. Matsuzaki 1, N. Kawamura 2, H. Imao 1, M. Iwasaki 1, Y. Matsuda 1, S. Nakamura 1**, A. Toyoda 2, M. Kato 4, H. Sugai 4, A. Uritani 5, H. Harano 5, G.H. Eaton 6 1 RIKEN, 2 KEK, 3 UC Riverside, 4 JAEA, 5 AIST, 6 RAL present address *U. Tohoku, **RIKEN NuFact06 ＠ UC Irvine 2006.08.28

2. muon catalyzed fusion (µCF) - principle and motivations After injection of muons into D/T mixture (or other hydrogen isotopes) Formation of muonic atoms and muonic molecules In small dtµ molecule, Coulomb barrier shrinks and d-t fusion follow Muon released after d-t fusion - muon works as catalyst - History 1947 Hypothesis of µCF (Frank) 1957 observation of pdµ fusion (Alvarez) 1966 observation of resonant ddµ formation 1967 hypothesis of resonant formation Vesman) 1979-82 observation of large dtµ formation rate 1987 observation of x-rays from (  µ) + (PSI,KEK) 1993 large ddµ formation rate in solid 1995 study with eV beam of (tµ) 1996 systematic study starts at RIKEN-RAL

3. Maximizing µCF efficiency. Motivations Atomic physics in small scale rich in few body physics problems Prospect for applications (fusion energy, neutron source) muon production cost (~5 GeV) vs fusion output (17.6 MeV x 120) Observables (1) Cycling rate c (  ) (vs 0 : muon life) dtµ formation tµ + D2  [(dtµ)dee] (2) Muon loss per cycle W (  ) muon sticking to  -particle, etc Fusion neutron disappearance rate : n = 0 +W  c Number of fusion per muon: Yn =  c / n = 1 / [( 0 /  c )+W] (  )

4. Outstanding problems in  CF Main  CF processes are understood, however still discrepancies … 1. Muonic atom acceleration during cascade, hyperfine transition, transfer 2.Molecular formation rates temperature dependence non-linear density (3-body?) effect ortho/para 3. Muon to alpha sticking initial sticking  atomic process, muon reactivation 4. Helium effect muon transfer process helium in solid D/T Progresses are being made in each of the problems. Focus is given to molecular formation rate in this talk. dt  formation transfer

5. Key process of µCF - dtµ formation Auger formation : 10 6 /s (as slow as muon decay rate 0.45 x 10 6 /s) t µ + D 2  (dt µ ) + D + e - Resonant molecular formation : 10 6 -10 9 /s t µ + D 2  ((dt µ ) dee) (dtµ binding energy ~ excitation of complex molecule) (tµ energy to match the small energy difference) Thus, dependence on temperature dependence on initial states such as tµ spin state, D 2 states We could change (enhance) µCF by controlling initial D 2 states.

6. Present understanding of dtµ formation dtµ molecule formation large formation rate (~10 9 /s) by resonant formation mechanism is established (temperature dependence, etc) still many surprises non-trivial density dependence even after normalization three-body effect : t µ + D 2 + D 2 ’  ((dtµ)dee) + D 2 ’’ low temperature & solid state effect density 

7. How about ddµ ? Same resonant formation process applies for ddµ formation in pure D 2 Slower compared to dt-µCF, and with lower energy output per fusion Still, study should be done in parallel with study of dtµ No need of tritium Simpler cycling process (pure D 2 ) d µ + D 2  [(dd µ )dee] In analogy to dtµ case, temperature dependence dµ Hyperfine effect (F=1/2,3/2) D 2 molecule effect

8. dd  formation: understanding before 2000 Resonant dd µ formation is nearly established in gas fitting by theoretical curve gives precision determination of shallow state binding energy in dd µ (-1.97 eV) [Petitjean et al] which is comparable to the value by precise three-body calculation However, in liquid and solid, large deviation from the theoretical curve was observed [Knowles et al, Demin et al] Theoretical prediction of dd  formation rate dependence on D2 ortho-para state. (ortho) (para)

9. New parameter: Ortho- and para-D 2 in  CF D2 populates several rotational states (J=0,1,2,3,4,…) With normal D 2, the resonance condition for all these are mixed. Ortho-D 2 (dd nuclear spin coupled with 0,2,  spin  J,v symmetry under dd exchange allows only J=even) Para-D 2 (similarly, for coupling with 1, J=odd allowed) Normal mixture is ortho:para=2:1 (for H 2, para H 2 has J=even) Resonance condition for each state should be separately measured. First measurement with normal- and ortho-D 2 at 3.5K Toyoda et al (2000) @ RAL, TRIUMF (fusion proton)

10. E968/E1061 Experiment @TRIUMF Measure dd  CF in D2 target (Since 2003) ortho/para controlled low temperature target (5K - 36 K) gas/liquid/solid phase several densities (0.03 to 1.2 of LHD) detectiong fusion neutrons TRIUMF M9B muon channel decay  - beam from 500 MeV x 200  A proton cw beam was necessary for dd  fusion 1) good time resolution (<1 ns) 2) suppression of muon capture neutrons background by coincidence with delayed me-decay 10  s beam gate limits the beam rate (50 k/s) 50 MeV/c muon beam (cryogenic Cu target cell, 1.5 Mbar)

11. Experimental setup @TRIUMF (E968/E1061) D 2 (ortho, normal or para) preparation ortho-para ratio analysis with Raman spectroscopy Target cell (30cc liquid/solid, or 200cc pressurized gas) muon beam counters B1+B2 µe-decay electron counters E1-E8 (>50% solid angle) neutron detectors(NE213) N1-N4 0 10cm target 2006 RUN 2004

12. muon beam gas preparation D 2 target and detectors

13. Ortho/para-D2 preparation and analysis Ortho D 2 (established) ortho-para conversion with Al 2 O 3 /Cr 2 O 3 catalysis Para D 2 (some success in Jun06 RUN) preferential adsorption on Al 2 O 3 at ~20K 99% para D 2 had been reported [D.A. Depatue and R.L. Mills, 1968] our case 55% para large gas quantity (30 liter), temperature control etc Analysis by laser Raman spectroscopy normal (o:p=0.67:0.33) para-rich (o:p=0.45:0.55) ortho (o:p=1:0) (J=0  2) (2  4) (4  6) (1  3) (3  5)

14. Fusion neutron time spectra: gas D 2 (36K) Fusion from resonant dd  formation (  =0.17, 36K) increased for ortho-rich D 2 However, some structure in very early timing.

15. Understanding non-exponential time structure Resonance calculation [by Adamczak] with time evolution of d  energy 1 10 100 600ns Imao’s thesis deceleration passing through dip in resonance spectrum

16. RUN in Jun 2006 Gas data at  =0.03 (28K and 36K), 0.07(36K), 0.17(36K) were recently obtained for normal-, ortho-, and para-rich(55%) D 2 to see temperature effect, density effect, non-exponential e\ffect (para) analysis is still in progress (signal selection, b.g. subtraction etc)  =0.07  =0.03

17. Typical fusion neutron time spectra: liquid D 2 fusion from resonantly formed ddµ (fast component) decreased in ortho-D 2 for all the temperature data (5K-36K) for solid and liquid D2 non-resonant resonant SUM of 19K-23K

18. Jun06 New data (Liquid) Gas

19. dd  summary Data for gas D 2 (  =0.17, 35K) was consistent with calculations based on idealistic gas model Non-exponential structure of fusion neutron time spectra is qualitatively understood by slow thermalization In liquid and solid phases, the observed ortho-para dependence of dd  formation rate was opposite to the prediction based on a simple gas model in all the temperature range measured (3K - 36K) Target D 2 density (rather than temperature) is responsible for the reversal Theory is being developed to include density and phase effect resonance energy shift, broadening

20. dt  case: theoretical calculations 1. Idealistic gas model tµ + D 2  [(dtµ)dee] low temp. resonance only for para-D 2 2. with Condensed matter effect under development [Adamczak] Even larger effect of ortho-para D 2 expected! [Faifman] 23K liquid [Adamczak]

21. Expected effect in D/T(50%) mixture Prepare ortho-D 2 or para-D 2 and mix with T 2 Very high cycling rate could be expected (>2 of normal rate) followed by decay due to 1. molecular equilibration process D 2 + T 2  2DT (~68 hour in D/T(50%)) tµ + D 2  [(dtµ)dee] tµ + DT  [(dtµ)tee]  dtµ 0,D2 >> dtµ 0,DT ) 2. ortho-para equilibration by radiation effect o-p conversion by paramagnetic T atom ~16 hours in D/T(50%) at 14K Cycling Rate c = 1/(  d +  t ) = 1/[ q 1s C d /( dt C t ) + ( 3/4 )/( t  1,0 C t ) + 1/(  dt  -D2(o,p) C D2(o,p) + dt  0,DT C DT )] full eq. av. time waiting d  ->t  transfer av. time in t  (F=1) state av. time before dt  formation c Time [hr ]

22. µCF at RIKEN-RAL Muon Facility RIKEN-RAL Muon at ISIS Intense pulsed muon beam (70ns width, 50 Hz) 800MeV x 200µA proton 20~150MeV/c µ + /µ - muon 5x10 4 µ - /s (55MeV/c) and tritium handling facility µCF experiment Proton beam line µSR Slow µ (Matsuda) µA*

23. µ CF target and detectors Cryogenic target : 1 c.c. liquid or solid D-T Detectors with calibration fusion neutrons, X-rays, µe decay 120 muon stops per pulse 10 6 fusions/s n X-ray ee muon µCF setup (RIKEN-RAL Port1)

24. Preparation of ortho-D 2 +T 2 target 1) Production of ortho D 2, analysis of ortho/para ratio 2) Evacuation of TGHS 3) Charge ortho D2 into target through TGHS and solidify 4) Extraction of T2 from getter and solidify into target 5) mix D2 and T2 by melting, start  CF measurement 6) after several days, turn to gas to force equilibration, restart  CF with equilibrated gas

25. Preliminary result of the first RUN: Cycling rate ： c D2+T2 D2+T2+DT(eq) the difference between normal D 2 and orthoD 2 was small (~5%) forced equilibration at gas state （ Sep 2005) (Aug 2001)

26. Result: Muon loss probability W D2+T2+DT(eq) D2+T2 Inpurities removes muon even at ppm level The impurity disappeared in liq D/T in a few hours, by self condensation(?) impurity effect largest contribution is from  -to-  sticking, but as dt  formation slows down loss through side path dd , tt  formation increases

27. Why the ortho-D 2 effect was not clearly seen? Possible reasons 1) fast ortho-para conversion (?) in the D 2 inlet path, in D 2 /T 2 liquid masked by impurity effect (first few hours) 2) ortho-para effect is small (?) non-thermalization change of resonance condition in condensed matter, similarly to dd  case Near future plans measurement with reduced impurity and para D2 study of ortho-para conversion rate at tritium lab. in JAEA in situ Raman analysis with new D/T target with optical window

28. Other ongoing studies of µCF Understanding mechanism and parameters of key processes 1.Muon-to-alpha sticking loss [my talk in NuFact04] muon-to-alpha sticking x-rays 2. Muon loss to accumulated 3 He from tritium decay [my talk in NuFact04] tHe  molecule formation and decay 3. dt  formaiton in wider and exotic target conditions low temperature solid D/T, high density D/T, ortho-para D 2 4. fusion in tt  particle correlations in 4 He-n-n exit channel

29. Use of intense muon beam in  CF Intense muon beams will definitely contribute to the study of µ CF 1) efficient search of more and more target conditions 2) short-lived extreme conditions (laser, plasma etc) 3) better S/N 4) exotic beams from µ CF 5) intense neutron source

30. Summary A clear effect of ortho-para ratio was observed for ddµ formation in D 2 In gas case, effect was consistent with theoretical prediction. (need to include thermalization process) In the liquid/solid case, the effect was opposite, possible modification of resonance condition by density effect Even larger effect was predicted for dtµ formation This opens up possibility for enhancement of µCF The first measurement failed to give conclusive result. Further study is planned. There are also other ongoing studies on  CF. Intense muon beam is indispensable for the study of  CF.