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Mit
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on the LEAP conferencePolarized Deuterium/Hydrogen Molecules
Possible Fuel for Nuclear Fusion Reactors?
by Ralf Engels
JCHP / Institut für Kernphysik, FZ Jülich
14.11.2013
2
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?
3
PIT@ANKE
• internal experiments – with the circulating beam • external experiments – with the extracted beam
p, p, d, dwith momenta up to 3.7 GeV/c
4
PIT @ ANKE/COSY
Main parts of a PIT:• Atomic Beam Source
• Target gas
hydrogen or deuterium• H beam intensity (2 hyperfine states) 8.2 . 1016 atoms / s• Beam size at the interaction point σ = 2.85 ± 0.42 mm• Polarization for hydrogen atomPZ = 0.89 ± 0.01 (HFS 1)
PZ = -0.96 ± 0.01 (HFS 3)
• Polarization for deuterium atoms atomPZ = 0.88 / PZZ = 0.88 (HFS 1/6)
PZ = 0.005 / PZZ = -1.71 (HFS 2/5)
• Lamb-Shift Polarimeter• Storage Cell
M. Mikirtychyants et al.; NIM A 721 (0) 83 (2013)
5
ABS and Lamb-shift polarimeter
6-polemagnet
6-polemagnet
rf-transition
6
Polarized H2 Molecules
Is there a way to increase Pm P
(surface material, T, B etc)?
Pm = 0.5 • Pa
Eley-Rideal Mechanism
9
Measurements from NIKHEF, IUCF, HERMES show that recombined molecules retain a fraction of initial nuclear
polarization of atoms!
Polarized H2 Molecules
The HERMES Collaboration; Eur. Phys. J. D 29, 21–26 (2004)DOI: 10.1140/epjd/e2004-00023-5
10
Theory
A.Abragam: The Principles of Nuclear Magnetism
Hamiltonian to describe the nuclear spin relaxation of H2 molecules
H = ωI ( I1z + I2
z) + ωJ Jz + ω‘ (I1 + I2)·J + ω‘‘ { I1· I2 – 3(I1· n)(I2 · n)}
I1 and I2 are the spins of the two protons I1 + I2 = I J is the rotational angular momentum of the molecule
ωI = - γI H0 is the proton Lamor frequency in the applied field H0
ωJ = - γJ H0 is the Lamor frequency of the rotational magnetic moment of the H2
ω‘ = - γI H‘ is the strength of the coupling between the magnetic moment of the
protons and the magnetic field produced at their positions by the rotation of the molecule ( H‘ = 2.7 mT)
ω‘‘ = 2 γI H‘‘ = γI2 ħ/ b3 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).
Bc (Hz) ≠ Bc (Dz) ≠ Bc (Dzz)
11
lim 0.5B
R
Nuclear Polarization of Hydrogen Molecules from Recombination of Polarized AtomsT.Wise et al., Phys. Rev. Lett. 87, 042701 (2001).
Polarized H2 Molecules
Spin Relaxation of H2/D2 Molecules
A. Abragam: The Principles of Nuclear Magnetism (1961)
The polarization losses duringa single wall collision depend on:-Nuclear Spin I-Polarization Pm
-Temperature-Magnetic field in the cell
P(B,n) = Pm · e- n ( )2Bc
B
n ≈ 1000
Polarization losses of the molecules
Bc = 6.1 mT
12
Recombination of polarized atoms into molecules
Conversion of polarized atoms and molecules into ions
Separation of protons and H2 by energy with the Wienfilter
Measurement of proton and H2 polarization in LSP polarize
d
cell wall
B ~ 1T
The idea
+
+
13
The SetupISTC Project # 1861 PNPI, FZJ, Uni. CologneDFG Project: 436 RUS 113/977/0-1
14
+H2 + e → H + 2e + …
H2 + e → H2 + 2e
The Ionization Processes
+
(Ee = 150 eV: σ = 0.46 · 10-16 cm2)
(Ee = 150 eV: σ = 0.88 · 10-16 cm2)
(Ee = 150 eV: σ = 0.082 · 10-16 cm2)
(www.nist.gov)
H + e → H + 2e+
15
Experimental results
Mass separation with the Wienfilter
Fel = FB
E • q = - q • v • B
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Recombination
17
Experimental results
Wienfilter function of the protons in the LSP
Ekin(p) = 1 keV
18
Experimental results
Wienfilter function of the H2 ions in the LSP+
19
Experimental results
How are the polarized H2S produced from H2?+
2-step process (Stripping at the Cs + H2S production)
1-step process: Direct production: H2 + Cs → H2S + Cs+…+
Cross section:σ(p→H2S) ≈ 35·σ(H2→H2S)
+
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Theory
Pm = 0.5
Bc = 6.1 mT
H2
+
21
Theory
22
Theory
23
See Talk by A. Nass on Friday
Experimental results
Protons:
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0.6
0.5
0.4
0.3
0.2
0.1
0
Experimental results
Polarization of the Protons
(HFS 1, Ep = 4 keV, Gold Surface, B=0.28 T)
28
Experimental results
Measurements on Fomblin (Perfluorpolyether PFPE)
HFS 3
TCell = 100 K
H2 :
Pm = - 0.84 ± 0.02
n = 217 ± 24
Protons:
Pm = - 0.81 ± 0.02
n = 136 ± 15 c = 0.993 ± 0.005 +
29
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
30
Experimental results
Measurements on Fomblin Oil (Perfluorpolyether PFPE)
HFS 3: Next day
TCell = 100 K
H2 :
Pm = - 0.80 ± 0.02
n = 110 ± 47
Protons:
Pm = - 0.80 ± 0.02
n = 336 ± 104 c = 0.526 ± 0.015
Pa = - 0.80 ± 0.02
+
31
Experimental results
Measurements on Fomblin (Perfluorpolyether PFPE)
HFS 2+3: Next day
TCell = 100 K
H2 :
Pm = - 0.68 ± 0.02
n = 184 ± 29
Protons:
Pm = - 0.68 ± 0.02
n = 409 ± 87 c = 0.88 ± 0.02
Pa = -0.68 ± 0.02
+
33
Experimental results
Measurements on Fomblin (Perfluorpolyether PFPE)
HFS 3
HFS 2+3
Bcell = 0.4 T , H2 only +
34
Experimental results
Very first results on water (Fomblin): (3. day)
p
H2
+Very Preliminary
HFS3
35
Experimental results
Very first results on water (Gold): Tcell = 100 K
-0,44
Pm = 0.28 ±0.01
n = 317 ± 16
Pm = - 0.25 ±0.01
n = 330 ± 26Pm = - 0.27 ±0.01
n = 605 ± 27
36
Experimental results
Measurements on Fused Quartz Glass after several days
Deuterium: HFS 3+4 (Vector and Tensorpolarized)
Pm,z = - 0.40 ±0.01
n = 686 ± 75
Pm,zz = 0.24 ± 0.03
n = 950 ± 246
(Pa,z = - 0.91 ± 0.01 / Pa,zz = + 0.85 ± 0.02)
Pm,zz = 0.24 ± 0.03
n = 1590 ± 590 c = 0.980 ± 0.006
Pm,z = - 0.40 ±0.01
n = 701 ± 180 c = 0.984 ± 0.008
TCell = 100 K
37
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 cosx-distribution).
-the Bc for vector- and tensor-polarized Deuterium.
-We can increase the target density with recombined molecules.
=> Bc (Dz) = 7 ±1 mT / Bc (Dzz) = 10 ±1 mT
38
To-do List
- Calculation of Bc 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
39
Polarized H2 Molecules
-
para-Deuterium
orto-Deuterium
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