on the LEAP conference

Polarized Deuterium/Hydrogen Molecules Possible Fuel for Nuclear Fusion Reactors?

14.11.2013

by Ralf Engels JCHP / Institut für Kernphysik, FZ Jülich

Important Questions for Polarized Fusion

Can the total cross sections of the fusion reactions be increased by use of polarized particles? (See talks by Paetz gen. Schieck, Deltuva, Kravchenko, Kravtsov) Will polarization survive in a plasma? (See talks by Holler and Didelez) What will happen in the different types of fusion reactors?

(See talks by Temporal and Sandorfi) How to get and how to handle polarized fuel?

2

PIT@ANKE

p, p, d, d

with momenta up to 3.7 GeV/c •

internal experiments

– • with the circulating beam

external experiments

– with the extracted beam 3

PIT @ ANKE/COSY

Main parts of a PIT: • Atomic Beam Source • Target gas

hydrogen

or

deuterium

• H beam intensity (2 hyperfine states)

8.2 . 10 16 atoms / s

• Beam size at the interaction point

σ = 2.85

±

0.42 mm

• Polarization for hydrogen atom

P Z = 0.89

±

0.01 (HFS 1) P Z = -0.96

±

0.01 (HFS 3)

• Polarization for deuterium atoms atom

P Z = 0.88 / P ZZ = 0.88 (HFS 1/6) P Z = 0.005 / P ZZ = -1.71 (HFS 2/5)

• • Lamb-Shift Polarimeter Storage Cell M. Mikirtychyants et al.; NIM A

721

(0) 83 (2013) 4

ABS and Lamb-shift polarimeter 6-pole magnet 6-pole magnet

5

Polarized H 2 Molecules

Eley-Rideal Mechanism

P

m

= 0.5 • P

a Is there a way to increase P m P (surface material, T, B etc)?

6

Polarized H 2 Molecules

Measurements from NIKHEF, IUCF, HERMES show that recombined molecules retain a fraction of initial nuclear polarization of atoms!

The HERMES Collaboration; Eur. Phys. J. D

29

, 21 –26 (2004) DOI: 10.1140/epjd/e2004-00023-5 9

Theory A. Abragam: The Principles of Nuclear Magnetism

Hamiltonian to describe the nuclear spin relaxation of H 2 molecules H = ω I ( I 1 z + I 2 z ) + ω J J z + ω‘ (

I 1

+

I 2

)·

J

+ ω‘‘ {

I 1 · I 2

– 3(

I 1 · n

)(

I 2 · n

)}

I 1

and

I 2 I 1

+

I 2

=

I

are the spins of the two protons

J

is the rotational angular momentum of the molecule ω I = γ I H 0 is the proton Lamor frequency in the applied field H 0 ω J = γ J ω‘ = - γ I H 0 is the Lamor frequency of the rotational magnetic moment of the H H‘ is the strength of the coupling between the magnetic moment of the 2 protons and the magnetic field produced at their positions by the rotation of the molecule ( H‘ = 2.7 mT) ω‘‘ = 2 γ I H‘‘ = γ I 2 ħ/ b 3 is the strength of the dipolar coupling between the protons, b is their distance, and

n

is the unit vector

b

/b (H‘‘ = 3.4 mT).

B

c

(H

z

) ≠ B

c

(D

z

) ≠ B

c

(D

zz

)

10

Polarized H 2 Molecules

Polarization losses of the molecules

A. Abragam: The Principles of Nuclear Magnetism (1961) Spin Relaxation of H 2 /D 2 Molecules The polarization losses during a single wall collision depend on: - Nuclear Spin I - Polarization P m - Temperature - Magnetic field in the cell

P

(B,n)

= P

m

· e

n

( )

2 B

B

c

= 6.1 mT

n ≈ 1000 Nuclear Polarization of Hydrogen Molecules from Recombination of Polarized Atoms T.Wise et al., Phys. Rev. Lett. 87, 042701 (2001).

B

lim 

R

 0.5

11

The idea

 Recombination of polarized atoms into molecules  Conversion of polarized atoms and molecules into ions  Separation of protons and H 2 energy with the Wienfilter + by  Measurement of proton and H 2 polarization in LSP + polarized B ~ 1T cell wall 12

The Setup

ISTC Project # 1861 PNPI, FZJ, Uni. Cologne DFG Project: 436 RUS 113/977/0-1 13

The Ionization Processes

(E e = 150 eV: σ = 0.46 · 10 -16 cm 2 )

H

2

+ e → H

+ 2

+ 2e

(E e = 150 eV: σ = 0.88 · 10 -16 cm 2 )

H

2

+ e → H + 2e + …

(E e = 150 eV: σ = 0.082 · 10 -16 cm 2 ) (www.nist.gov) 14

Experimental results

Mass separation with the Wienfilter F

el

= F

B

E • q = - q • v • B

15

Recombination

16

Experimental results

Wienfilter function of the protons in the LSP

E kin (p) = 1 keV 17

Experimental results

+

Wienfilter function of the H

2

ions in the LSP

18

Experimental results

How are the polarized H

2S +

produced from H

2

?

2-step process (Stripping at the Cs + H 2S production) 1-step process: Direct production: H 2 + + Cs → H 2S + Cs + … Cross section: σ(p→H 2S ) ≈ 35·σ(H + 2 →H 2S ) 19

Theory

H 2 + P m = 0.5

B c = 6.1 mT 20

Theory

21

Theory

22

Experimental results

Protons:

See Talk by A. Nass on Friday 23

Experimental results

Polarization of the Protons (HFS 1, E p = 4 keV, Gold Surface, B=0.28 T) 0.6

0.5

0.4

0.3

0.2

0.1

0 24

Experimental results

Measurements on Fomblin (Perfluorpolyether PFPE) HFS 3 T Cell = 100 K Protons: P m = - 0.81 ± 0.02

n = 136 ± 15 c = 0.993 ± 0.005

H 2 + : P m = - 0.84 ± 0.02

n = 217 ± 24 28

Experimental results

J.S. Price and W. Haeberli, “Measurement of cell wall depolarization of polarized hydrogen gas targets in a weak magnetic field” Nuclear Instruments and Methods in Physics Research A

349

(1994) 321-333 29

Experimental results

Measurements on Fomblin Oil (Perfluorpolyether PFPE) HFS 3: Next day T Cell = 100 K Protons: P m = - 0.80 ± 0.02

n = 336 ± 104 c = 0.526 ± 0.015

P a = - 0.80 ± 0.02

H 2 + : P m = - 0.80 ± 0.02

n = 110 ± 47 30

Experimental results

Measurements on Fomblin (Perfluorpolyether PFPE) HFS 2+3: Next day T Cell = 100 K Protons: P m = - 0.68 ± 0.02

n = 409 ± 87 c = 0.88 ± 0.02

P a = -0.68 ± 0.02

+ H 2 : P m = - 0.68 ± 0.02

n = 184 ± 29 31

Experimental results

Measurements on Fomblin (Perfluorpolyether PFPE) B cell = 0.4 T , H 2 + only HFS 3 HFS 2+3 33

Experimental results

Very first results on water (Fomblin): (3. day)

p HFS3 H 2 +

Very Preliminary

34

Experimental results

Very first results on water (Gold): T

cell

= 100 K

P m = - 0.27 ±0.01

n = 605 ± 27 P m = 0.28 ±0.01

n = 317 ± 16 P m = - 0.25 ±0.01

n = 330 ± 26 -0,44 35

Experimental results

Measurements on Fused Quartz Glass after several days Deuterium: HFS 3+4 (Vector and Tensorpolarized) (P a,z = - 0.91 ± 0.01 / P a,zz = + 0.85 ± 0.02) T Cell = 100 K P m,zz = 0.24 ± 0.03

n = 1590 ± 590 c = 0.980 ± 0.006

P m,zz = 0.24 ± 0.03

n = 950 ± 246 P m,z = - 0.40 ±0.01

n = 701 ± 180 c = 0.984 ± 0.008

P m,z = - 0.40 ±0.01

n = 686 ± 75 36

Conclusion

We can measure: - the recombination of hydrogen/deuterium atoms on different surfaces and for different HFS. - the polarization of atoms and molecules in a storage cell.

- the number of wall collisions of the molecules in the cell.

At least, we can see the difference between „hard“ and „soft“ materials (elastic scattering or cos x -distribution).

- the B c for vector- and tensor-polarized Deuterium.

=> B

c

(D

z

) = 7 ±1 mT / B

c

(D

zz

) = 10 ±1 mT

- We can increase the target density with recombined molecules.

37

To-do List

Calculation of B c for vector- and tensor-polarized Deuterium - Additional cryo-catcher between ABS and ISTC-chamber - Measurements on different surfaces : - Aluminium - Teflon … - More measurements on a water surface (Maybe the surface below has some influence …) - Development of a new openable storage cell for ANKE Polarized Deuterium Fuel for polarized fusion reactors 38

Polarized H 2 Molecules

para-Deuterium orto-Deuterium 39