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Polarized Fusion

by Giuseppe Ciullo INFN and University of Ferrara

for Ralf Engels JCHP / Institut für Kernphysik, FZ Jülich

21.10.2014

Nuclear Fusion with Polarized Particles

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The first three reactor generations, organized according to relative energy (temperature) requirement for fusion.

Polarized Fusion

Total cross section Energy production: 1. Generation: D + T 4He + nHighest cross section at lowest temperature

2. Generation: D + D t + p or 3He + nFuel everywhere available

3. Generation 3He + D 4He + pNeutron lean reactor if D+D suppressed

(More fusion reactions are possible !)

Up to now: The D + D reactions are used in scientific tokomaks (ITER is optimized for DT!)

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Can the total cross section of the fusion reactionsbe increased by using polarized particles ?

3He + d 4He + p

t + d 4He + n

J = 3/2 + / s-wave dominated (~96%)

H. Paetz gen. Schieck, Eur. Phys. J. A 44, 321-354 (2010)

Polarized Fusion

More details in A. Sandorfi’s talk and

Factor: ~1.5 at 107 keV

Factor: ~1.5 at 430 keV

[Ch. Leemann et al., Helv. Phys. Acta 44, 141 (1971)]

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What is the advantage for fusion reactors ?

Polarized Fusion

Laser Pellet target (DT pellets)

(Berkeley, Orsay, Darmstadt, …)

1.) Inertial Fusion (Laser induced fusion)

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What is the advantage for fusion reactors ?

Calculation by M. Temporal et al. for the „Megajoule“ Project

Polarized Fusion

M. Temporal et al.; “Ignition conditions for inertial confinement fusion targets with polarized DT fuel” Nucl. Fusion 52 (2012) 103011

s DT pol = d s DT unpol

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Can the trajectories of the ejectiles be controlled by using polarized particles ?

Polarized Fusion

Total cross sectionUnpolarized differential cross section

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1st generation reactor:polarized fuel helps to optimize fusion reactors

D + T (3He + D) polarized fuel1st

*

*

* 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).

Confirmed on mirror reaction 3He(d,p)4He [Ch. Leeman et al Helv. Phys. Acta 44 (1971) 141]

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D + D reactors

D + D → T + p 50% (no n)→ 3He + n 50%(*)

D + T can fuses (n)3He does not contribute at the ignition energy of D-D

D ↑ + D ↑ spin dependent cross section (data set very poor), at low energy (electron screening ?).

2nd

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?

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Spin allows to enhance or suppress reaction channels

Neutron lean fusion reactor D -3He

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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Polarized Fusion

Deltuva in Nuclear fusion with polarized nucleonsTrento 14-15 Nov 2013

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Which questions must be solved ?

1.) Dependence of the total cross section from the polarization for all fusion reactions.

Polarized Fusion

d + dt + p

3He + n

Can cross sections be increased ?

Can neutrons be suppressed ?Can the trajectories of the neutronsbe controlled?

Reaction is not s-wave dominated !

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Spins of both deuteronsare aligned:

Only pz(qz) and pzz(qzz) ≠ 0

Only beam is polarized:

(pi,j ≠ 0, qi,j = 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 }

Polarized Fusion

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The Experimental Setup at PNPI

ABS from the SAPIS project:(after upgrade)~ 4 ∙ 1016 a/s→ ~ 2 ∙ 1011 a/cm2

POLIS (KVI, Groningen)

Ion beam: I ≤ 20 μA

→ 1.5 ∙ 1014 d/s( Ebeam ≤ 32 keV )

dd-fusion polarimeter

LSP from POLIS

LSP from the SAPIS project

Luminosity: 3 ∙ 1025 /cm2 s

→ count rate: ~ 40 /h

→ 2 month of beam time

Detector Setup:4π covered by - large pos. sens. Detectors- (~ 500 single PIN diodes ?)

ABS from Ferrara:

~ 6 ∙ 1016 a/s

→ ~ 3 ∙ 1011 a/cm2

Luminosity: 4.5 ∙ 1025 /cm2 s

→ count rate: ~ 60 /h

→ 1 month of beam timeP. Kravtsov in Nuclear fusion with polarized nucleonsTrento 14-15 Nov 2013

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POLIS and Ferrara ABS @ PNPI

← POLIS →

← ABS from Fe

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Which questions must be solved ?

1.) Dependence of the total cross section from the polarization for all fusion reactions. (d+d is underway) 2.) Polarization conservation in the different plasmas ? a.) Magnetic confinement:

Details in the next talk by Andrew Sandorfi(US-Patent by H. Greenside, R. Budny and D. Post on a special surface

for polarization conservation on the wall !)

b.) Inertial Fusion (Laser induced): - J.P. Didelez and C. Deutsch; 2011 Laser and Particle

Beams 29 169. - M. Büscher (FZJ / Uni. Düsseldorf)

„Laser Acceleration“

Polarized Fusion

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Laser Acceleration

~ 100 GV/m ~ 100 GV/m

Proton rich dot20x20x0.5 μm

108 protons at 1.5 MeV 1011 protons up to 10 MeV

Laser Acceleration of pol. 3He2+ ions from pol. 3He gas jets

A. Holler in Nuclear fusion with polarized nucleons Trento 14-15 Nov 2013

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Which questions must be solved ?

1.) Dependence of the total cross section from the polarization for all fusion reactions. 2.) Polarization conservation in the different plasmas ?

3.) How to produce polarized fuel ?- HD targets are available (10 mK, ~15 T -> see next

talk )

-> frozen spin DT targets possible ??

Gaseous fuel a.) pol. 3He is available („Laser-pumping“) b.) pol. T will be possible with a similar method c.) pol. D ???

Polarized Fusion

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PIT @ ANKE/COSY

Main parts of a PIT:• Atomic Beam Source

• Target gas

hydrogen or deuterium• H/D beam intensity (2 hyperfine states)

8.2 . 1016 / 6 . 1016 atoms/s• Beam size at the interaction point

σ = 2.85 ± 0.42 mm• Polarization for hydrogen/deuterium

PZ = 0.89 ± 0.01

PZ = -0.96 ± 0.01

Pz = + 0.88 ± 0.01 / - 0.91 ± 0.01

Pzz = - 1.71 ± 0.03 / + 0.90 ± 0.01

• Lamb-Shift Polarimeter• Storage Cell

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Polarized H2/D2 Molecules

lim 0.5B

R

Nuclear Polarization of Hydrogen Molecules from

Recombination of Polarized Atoms

T.Wise et al., Phys. Rev. Lett. 87, 042701 (2001).

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0 exp cBR R n

B

Measurements from NIKHEF, IUCF, HERMES show that recombined molecules retain fraction of initial nuclear

polarization of atoms!

polarized

unpolarized

Pm = 0.5

Naïve model

Is there a way to increase

Pm (surface material, T, B etc)?

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The SetupISTC Project # 1861 PNPI, FZJ, Uni. Cologne

DFG Project: 436 RUS 113/977/0-1

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Polarized H2 Molecules

Pm = - 0.84 ± 0.02 n = 277 ± 31

Protons: Pm = - 0.81 ± 0.02 n = 174 ± 19 c = 0.993 ± 0.005

Measurements on Fomblin Oil (Perfluorpolyether PFPE)

HFS 3 (Pa = - 0.93)

H2 - Ions: +

TCell = 100 K

Expected max. molecular polarizaton Pm= - 0.87)

R. Engels et al. RSI 85 (2014) 103505

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Which questions must be solved ?

1.) Dependence of the total cross section from the polarization for all fusion reactions. 2.) Polarization conservation in the different plasmas ?

3.) How to produce polarized fuel ?- HD targets are available (10 mK, ~15 T -> see next talk )

-> frozen spin DT targets possible ??

Gaseous fuel

a.) pol. 3He is available („Laser-pumping“) b.) pol. T will be possible with a similar method c.) pol. D ??? => new ideas are welcome !!!!

Polarized Fusion