Post on 14-Jul-2020
Introduction to Polarized Fusion
G.Ciullo
Physics department and Earth Science
University of Ferrara
and
INFN (National Institute of Nuclear Physis)
44122 – Ferrara – ITALY
G. Ciullo 1
In Polarized Fusion 2017 at BINP
Budker Institute of Nuclear Physics
Is bowling game easier than spin game? Is spin – game more attracting? Is not bowling with spinning Balls more exciting? In nuclear fusion: spin game will allow the bowling to work?
Spin against bowling game
2
Spin game
Bowling game
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From the point of view of the nuclear
physicists, the use of polarized fuel
seems the viable way in order to fulfill
nuclear fusion for energy production
thanks to:
enhancement on fusion cross
section,
control on angular distribution of
reaction products,
possible neutron lean reactors.
But the practical use of it is still far away,
mainly due to still questions and
requirements:
polarized fuel, high polarization and
high density (two or three order
magnitude higher than available as
nuclear polarized targets).
Preparation of fuel for magnetic
confinement or inertial confinement.
Survival of polarized fuel in the
fusion reactors (magnetic or inertial
confinement).
It’s a challenging deal providing useful polarized fuel for the purpose of testing the polarized FUSION in present (… future) constrains and contests
“Polarized Fusion”: Fusion with Nuclear Polarized Fuel
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“Quality of life”: requires electrical consumption
Developping world ( 5 billion people) is crawling up UN HDI (United Nation Human Development Index).
The main energy resource in the past few centuries fossil fuel. World Energy Scenario (1996), from World Energy Council (WEC), Internation Energy Agency (IEA) and other international organizations estimate Coal 230 year, natural gas 63, oil 44 years.
2013 new report and suggested scenario (Jazz or Symphony). Total resource based also in non conventional gas and oil extraction, estimation extended to … 100 years.
from “Fusion Physics” ed. IAEA Vienna 2012
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From WEC (Wolrd Energy Council) reports
Fossil fuel global warming
Depleting only coal largest emitter of CO2
Oil and gas reserves: tens/100s of years and political & military conflits
Development of fission nuclear reactors pubblic opposition, proliferation, radiative hazard waste, catastrofic Chernobyl, Fukushima Dai-ichi like disasters.
Alternative clean energy: solar, not suitable for large urban or industrial center, continuity,
accumulation … waste. Wind, not suitable for large urban or industrial center, continuity,
accumulation … biofuel (soil erosion, deforestation, desertification, food price …
Fission (important role , was prominent in France) but … already mentioned.
Fusion: a global approach to a global problem. The holy Graal for primary energy resources: it requires international collaboration, investments and efforts: ITER …
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No big changes in previsions of the WEC reports on 2016, mostly monitoring on energy trilemma (energy security, energy equity, and environmental sustainability) pushing towards
international collaborations and coordinations on the energy problems and solutions.
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Mostly the 2DS (2 degree scenario) is scaring the society
G. Ciullo in Nuclear physics with polarized Fuel (Springer International Publishing , Switzerland, 2016
______________________________ 1st gen
______________________________ 2nd gen
____________________
_______________________________3rd gen
D-D to start fusion, T produced by n on blanket
(containing Litium)
6Li + slow n -> T + 4He + 4.8 MeV (exoE) 7Li + fast n -> T + 4He – 2.5 MeV + n’ slow
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How the “polarized fusion” can helps?
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Polarized fusion: test bench 3He+d reaction
Can the total cross section of the fusion reactions be increased by using polarized particles ?
Reactions through the spin channel
Jp = 3/2 + / S-wave dominated (~96%)
H. Paetz gen. Schieck Nuclear physics with polarized particles (Springer
Verlag, Berlin, 2012); Eur. Phys. J. A 44, (2010) 321; Few-Body Syst. 54
(2013) 2159
Factor: ~1.5 at 107 keV
Factor: ~1.5 at 430 keV
[Ch. Leemann et al., Helv. Phys. Acta 44, 141 (1971)]
3He ®
+ d®
Þ 4 He + p
t®
+ d®
Þ 4 He + n
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Cross-section enhancement factor 1.5
Unpolarized cross section = weighted sum of all channel spin s
s unpol = (2s+1)
så s s
(2s+1)s
å
For both reactions channel spins can be 3/2 and 1/2.
s unpol = 2s1 2 + 4s 3 2
6 =
1
3s1 2 +
2
3s 3 2
From experiments: both reactions proceed via the
Jp = 3/2+ (5He* and 5Li*).
At low energy the incaming l =0 , S-wave dominate:
Only the 3/2 contributes to the sunpol,
if the incoming particles are both polarized:
gain= s pol
s unpol
=s 3 2
2 / 3s 3 2
= 1.5
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Enhancement: test bench 3He + d more details
d-t practical in tokamaks for its high cross section (5 b) at d lab
energy of 107 keV, more relaxed Lawson‘s criterion ntE > 1014
sec cm-3 for ignition in fusion reactor
Jp = 3/2 + / S-wave dominated (0.95 < f <1)
Jp = 1/2 + / S-wave dominated (1-f) s tot = w(J = 3/ 2)s3/2(J = 3/ 2)+w(J =1/ 2)s1/2(J =1/ 2)
w(J) = JdJtmdmt JMmd,mt
å2
N(md )N(mt ) / N(J)
md mt nuclear spin state (d and t) with respect to the magnetic field of the reactor (Jd =1 , Jt =1/2) N fractional population of the respective spin state.
More clear referencing the statistical weight to the polarization degree
t®
+ d®
Þ 4 He + nFrom experiments:
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In purely S-wave (f =1)
s tot = 1+1
2Pz
DPz
Tæ
èç
ö
ø÷s unpol
s tot =1.5sunpol
and in case of completely vector polarized D (PzD= 1,) and T(Pz
T= 1)
This is to clarify the importance of the polarization. when we talk of 1.5 enhancement in cross section, we‘re talking about pure S-wave interaction and both fusing particle populations fully polarized.
This pushes our efforts to as higher as possible polarization of the fuel.
Statistical weight w as function of polarization degree P
s tot = f 1+1
2Pz
DPz
Tæ
èç
ö
ø÷+ (1-f ) 1- Pz
DPz
T( )é
ëê
ù
ûús unpol
R.M. Kulsrud et al. Nucl. Phys. 26 (1986) 1443-1462 H. Hasuyama et al. Helv. Phys. Acta 59 (1986) 723-727
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Angular distribution of reaction products In purely S-wave approx, f =1, B along z, (q) respect to B (z)
In the d t reaction with d and t polarized parallel to B
ds q( )dW
=9
4sin2 q
ds q( )dW unpol
Azz tensor analysing power Azz= - [3 (cos2 (q) -1]/2
Czz spin correlation coefficient Czz= - 3 [cos2 (q) -2]/2
s tot =1.5 s unpol
ds q( )dW
= 1+1
2Pzz
DAzz +3
2Pz
DPz
TCzz
æ
ææ
æ
ææds q( )
dW unpol
In the case of only d polarized perpendicular to B
s tot =s unpol
ds q( )dW
=1
2(1+3cos3q )
ds q( )dW unpol
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0 50 100 150
d t polarized || B * D and T spin || to
the confinement field: a and n emitted as sin2 q respect to B
* D spin ┴ to the
confinement field and T unpolarized: no influence on cross section, but the reaction products follow (1+3cos2 q).
*
*
0 50 100 150
d polarized | B
Confirmed on mirror reaction 3He(d,p)4He [Ch. Leeman et al Helv. Phys. Acta 44 (1971) 141]
Calculation Experiments
G. Ciullo
R.M. Kulsrud et al. Phys. Rev. Lett. 49 (1982) 1248 polarized
fusion reactor plasmas.
E. Bittoni et al. Nucl. Fus. 23 (1983) 830, perpendicular
spin: reduction of factor two on alpha loading on the wall.
B. Coppi Phys. Scripta T2B (1982) 590 address to
neutronless fusion reacting plasmas, using also polarized
fuel.
M.R. More Phys. Rev. Lett. 51 (1983) 396 study for ICF.
B.J. Micklich et al. Nucl. Techn./Fus 5 (1984) 162: relaxed
fusion condition ntE and Ti for ignition and breakeven, more
20% ~ 30% of neutron flux localized in the inboard firt wall
(D pol perp to B)
D.A. Noever Fus. Tech. 27 (1995) 86: simple mirror fusion
reactors with polarize fuel, Q = Pfusion /Pinput =1.63: new
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On the table Polarized Fusion seems very promising
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Still … opend questions?
Tritium is radioactive T → 3He + e− + anti-ne , (t1/2=12.3 y) volatile,
diffuse in metal, bond in water: not confortable for research
investigation.
We can provide high polarization (0.90) in atomic beam 1016 pol
atom/sec, confined in special surface for use in continuous refilling
(open tube). But is it possible to produce (orto-) and store (frozen)
them polarized? R. Engels
Is it possible to produce orto-molecule from Stern-Gerlach quantum
selection? D. Toporkov
How polarization behave in magnetic fields ?
How polarization match with existing (and future) project?
Polarization can survive in plasma?
Production of polarized ion by laser acceleration, the polarization
will survive? M. Büscher
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D+D → T + p / 3He + n
The total cross section D + D in respect to the incoming
polarization of the fusing particles:
D ↑ + D ↑ spin dependent cross section (data set very poor),
and stilll worse at lower energy (electron screening ?)
2nd
Hjgher energy for fusion involev also P-, D-wave, togheter with S-wave and their
interferences
Fusing D + D, then D + T can fuses (n) 3He does not contribute at the ignition energy of D-D
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Neutron Lean fusion? QSF (Quintet Suppression Factor)
Spin alignements allows to enhance or suppress reaction
channels?
D↑ (d ↑ p) T and D↑ (d ↑ n) 3He suppressed by choosing deuteron spin parallel each others
S 1 1 0 5S2 Quintet State Suppressed
S 1 -1 0 1S0 Singlet state allowed
D↑ D↑ 4He*
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Neutron lean reactors?
D + 3He → 4He + p ?
Can we have neutron free reactor?
3rd
If we suppress or reduce D-D fusion, we could have neutron free or lean reactors
The spin configuration is 1 + ½, like the T + D, and was
the confirmed measurements already in the 1971
We said “lean”, because we’ll still have n from D + T, T produced in D + D reaction.
To answer to the D D polarized fusion we need to know the cross section of the whole set of orientation of the spin T produced in D + D
reaction.
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D + D cross section: … experimental test? A. Vasilyev
Only beam is polarized: (pi,j ≠ 0, qi,j = 0)
Spins of both deuterons
aligned: only pz(qz) and
pzz(qzz) ≠ 0
σ(ϴ,Φ) = σ0(ϴ) · {1 + 3/2 Ay(ϴ) py + 1/2 Axz(ϴ) pxz + 1/6 Axx-yy(ϴ) pxx-zz + 2/3 Azz(ϴ) pzz }
H. Paetz gen. Schieck, Eur. Phys. J. A 44, (2010) 321
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PolFusion: D D spin dependent cross sections
Analysing powers: angular distribution of reaction, in which only one participant
to the reaction is polarized, therefore we distinguish between A(b) and A(t).
Spin correlation coefficients: p (beam) and q (target) required in order to have a real map of how is evolving the spin-spin fusion reaction, and in order to provide data for prevision.
This is the another challenge of our collaboration. A. Vasilyev, P. Kravtov, They will give a talk on the status of the apparatus and project. This involves also theoretical studies to address the most usefull and “easily„ observable.
D D polarized measurements was and still is claimed from many scientists to be a complete experiment to fullfill the reaction for thermonuclear
applications, understanding nuclear forces, four nucleon system, and more basic physical principles, from far away to present.
These measurements allow to extrapolate S, P, D-wave, and disentangle the electron screening enhancement of the cross-section.
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… more will be discussed in this meeting, but ...
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2016 Springer international Publishing