Muon Catalyzed Fusion CF Recent progress and future plan

1
Muon Catalyzed Fusion (µCF) - Recent progress
and future plan
NuFact06_at_UC Irvine 2006.08.28

• K. Ishida (RIKEN)
• Introduction
• ddm formation
• wider range of temperature, phase and ortho/para
  ratio of D2
• dtm formation
• first experiment with T2/ortho-D2 mixture
• mCF with intense muon beam
• in collaboration with
• K. Nagamine1,2,3, T. Matsuzaki1, N. Kawamura2,
  H. Imao1,
• M. Iwasaki1, Y. Matsuda1, S. Nakamura1, A.
  Toyoda2, M. Kato4, H. Sugai4,
• A. Uritani5, H. Harano5, G.H. Eaton6
• 1RIKEN, 2KEK, 3UC Riverside, 4JAEA, 5AIST, 6RAL
• present address U. Tohoku , RIKEN

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 (aµ) (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 lc (h) (vs l0 muon life)
• dtµ formation tµ D2 g(dtµ)dee
• (2) Muon loss per cycle W (i)
• muon sticking to a-particle, etc
• Fusion neutron disappearance rate ln l0 Wflc
  
• Number of fusion per muon
• Yn flc/ln 1 / (l0/flc)W (h)

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.

transfer
5
Key process of µCF - dtµ formation

• Auger formation 106 /s (as slow as muon decay
  rate 0.45 x 106/s)
• tµ D2 g (dtµ) D e-
• Resonant molecular formation 106-109 /s
• tµ D2 g ((dtµ) 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, D2 states
• We could change (enhance) µCF by controlling
• initial D2 states.

6
Present understanding of dtµ formation

• dtµ molecule formation
• large formation rate (109/s) by resonant
  formation mechanism
• is established (temperature dependence, etc)
• still many surprises
• non-trivial density dependence even after
  normalization
• three-body effect tµ D2 D2 g
  ((dtµ)dee) D2
• low temperature solid state effect

density f
7
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 fusion
• Still, study should be done in parallel with
  study of dtµ
• No need of tritium
• Simpler cycling process (pure D2)
• dµ D2 g (ddµ)dee
• In analogy to dtµ case,
• temperature dependence
• dµ Hyperfine effect (F1/2,3/2)
• D2 molecule effect

8
ddm formation understanding before 2000

• Resonant ddµ formation is nearly established in
  gas
• fitting by theoretical curve gives
• precision determination of shallow state
• binding energy in ddµ (-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 ddm formation rate
• dependence on D2 ortho-para state.

(ortho)
(para)
(ortho)
9
New parameter Ortho- and para-D2 in mCF

• D2 populates several rotational states
  (J0,1,2,3,4,)
• With normal D2, the resonance condition for all
  these are mixed.
• Ortho-D2 (dd nuclear spin coupled with 0,2,
• y spin yJ,v symmetry under dd exchange allows
  only Jeven)
• Para-D2 (similarly, for coupling with 1, Jodd
  allowed)
• Normal mixture is orthopara21
• (for H2, para H2 has Jeven)
• Resonance condition for each state should be
  separately measured.
• First measurement with normal- and ortho-D2 at
  3.5K
• Toyoda et al (2000) _at_ RAL, TRIUMF (fusion proton)

10
E968/E1061 Experiment _at_TRIUMF

• Measure dd mCF 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 m- beam from 500 MeV x 200 mA proton
• cw beam was necessary for ddm fusion
• 1) good time resolution (lt1 ns)
• 2) suppression of muon capture neutrons
  background
• by coincidence with delayed me-decay
• 10 ms beam gate limits the beam rate (50 k/s)
• 50 MeV/c muon beam (cryogenic Cu target cell,
  1.5 Mbar)

11
Experimental setup _at_TRIUMF (E968/E1061)

• D2 (ortho, normal or para) preparation
• ortho-para ratio analysis with Raman spectroscopy
• Target cell (30cc liquid/solid, or 200cc
  pressurized gas)
• muon beam counters B1B2
• µe-decay electron counters E1-E8 (gt50 solid
  angle)
• neutron detectors(NE213) N1-N4

2006 RUN
2004
target
0 10cm
12
gas preparation
muon beam
D2 target and detectors
13
Ortho/para-D2 preparation and analysis

• Ortho D2 (established)
• ortho-para conversion with Al2O3/Cr2O3
  catalysis
• Para D2 (some success in Jun06 RUN)
• preferential adsorption on Al2O3 at 20K
• 99 para D2 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 (op0.670.33)
(2g4)
(J0g2)
(1g3)
(3g5)
(4g6)
para-rich (op0.450.55)
ortho (op10)
14
Fusion neutron time spectra gas D2 (36K)

• Fusion from resonant ddm formation (f0.17, 36K)
  increased for ortho-rich D2
• However, some structure in very early timing.

15
Understanding non-exponential time structure

• Resonance calculation by Adamczak

with time evolution of dm energy
100
10
1
600ns
Imaos thesis

deceleration passing through dip in resonance
spectrum
16
RUN in Jun 2006

• Gas data at f0.03 (28K and 36K), 0.07(36K),
  0.17(36K)
• were recently obtained for normal-, ortho-, and
  para-rich(55) D2
• to see temperature effect, density effect,
  non-exponential e\ffect (para)
• analysis is still in progress (signal
  selection, b.g. subtraction etc)

f0.07
f0.03
17
Typical fusion neutron time spectra liquid D2
SUM of 19K-23K
resonant
fusion from resonantly formed ddµ (fast
component) decreased in ortho-D2 for all the
temperature data (5K-36K) for solid and liquid D2
non-resonant
18
Gas
Jun06 New data (Liquid)
19
ddm summary

• Data for gas D2 (f0.17, 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 ddm formation rate was
  opposite to the prediction based on a simple gas
  model in all the temperature range measured (3K -
  36K)
• Target D2 density (rather than temperature) is
  responsible for the reversal
• Theory is being developed to include density and
  phase effect
• resonance energy shift, broadening

20
dtm case theoretical calculations

• 1. Idealistic gas model
• tµ D2 g (dtµ)dee
• low temp. resonance only for para-D2
• 2. with Condensed matter effect
• under development Adamczak
• Even larger effect of
• ortho-para D2 expected!

Faifman
23K liquid
Adamczak
21
Expected effect in D/T(50) mixture

• Prepare ortho-D2 or para-D2 and mix with T2
• Very high cycling rate could be expected
• (gt2 of normal rate)
• followed by decay due to
• 1. molecular equilibration process
• D2 T2 D 2DT (68 hour in D/T(50))
• tµ D2 g (dtµ)dee
• tµ DT g (dtµ)tee (ldtµ0,D2gtgtldtµ0,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
• lc 1/(tdtt)
• 1/ q1sCd/(ldtCt) (3/4)/(ltm1,0Ct)
• 1/(l0dtm-D2(o,p)CD2(o,p) ldtm0,DT CDT)
•  

lc
full eq.
Time hr
av. time in tm(F1) state
av. time before dtm formation
av. time waiting dm-gttm transfer
22
µCF at RIKEN-RAL Muon Facility
Proton beam line

• RIKEN-RAL Muon at ISIS Intense pulsed muon beam
• (70ns width, 50 Hz)
• 800MeV x 200µA proton
• 20150MeV/c µ/µ- muon
• 5x104 µ-/s (55MeV/c)
• and tritium handling facility

Slow µ (Matsuda)
µA
µSR
µCF experiment
23
µCF 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
• 106 fusions/s

X-ray
µCF setup (RIKEN-RAL Port1)
muon
n
me
24
Preparation of ortho-D2T2 target

• 1) Production of ortho D2, 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 mCF
  measurement
• 6) after several days,
• turn to gas to force equilibration,
• restart mCF with equilibrated gas

25
Preliminary result of the first RUN Cycling
rate lc
(Sep 2005)
(Aug 2001)
D2T2
forced equilibration at gas state
D2T2DT(eq)
the difference between normal D2 and orthoD2 was
small (5)
26
Result Muon loss probability W
Inpurities removes muon even at ppm level The
impurity disappeared in liq D/T in a few hours,
by self condensation(?)
impurity effect
D2T2DT(eq)
largest contribution is from m-to-a sticking,
but as dtm formation slows down loss through side
path ddm, ttm formation increases
D2T2
27
Why the ortho-D2 effect was not clearly seen?

• Possible reasons
• 1) fast ortho-para conversion (?)
• in the D2 inlet path, in D2/T2 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 ddm 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
• Muon-to-alpha sticking loss my talk in NuFact04
• muon-to-alpha sticking x-rays
• 2. Muon loss to accumulated 3He from tritium
  decay my talk in NuFact04
• tHem molecule formation and decay
• 3. dtm formaiton in wider and exotic target
  conditions
• low temperature solid D/T, high density D/T,
  ortho-para D2
• 4. fusion in ttm
• particle correlations in 4He-n-n exit channel

29
Use of intense muon beam in mCF

• Intense muon beams will definitely contribute to
  the study of µCF
• 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 µCF
• 5) intense neutron source

30
Summary

• A clear effect of ortho-para ratio was observed
  for ddµ formation in D2
• 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 mCF.
• Intense muon beam is indispensable for the study
  of mCF.