Introduction to Polarized Fusion

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

Polarized Fusion 2017 -

Novosibisk G. Ciullo 3

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



“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



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 …



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.



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

(endoE) Polarized Fusion 2017 –


How the “polarized fusion” can helps?



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



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



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:



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



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


Novosibisk 14

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

design optimization. Polarized Fusion 2017 -


On the table Polarized Fusion seems very promising



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



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



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*



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.



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



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.



… more will be discussed in this meeting, but ...

G. Ciullo 22

2016 Springer international Publishing

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Introduction to Polarized Fusion