IPN Orsay FEW-BODY 19th – Bonn Jean-Pierre DIDELEZ Persistence of the Polarization in a Fusion Process J. P. Didelez IPN and C. Deutsch LPGP Orsay DT polarization and Fusion Process Magnetic Confinement Inertial Confinement Persistence of the Polarization - Polarized D and 3 He in a Tokamak - Radiative Capture and DD Fusion induced by Laser on polarized HD The “Few-Body” Problems Conclusion

DT polarization and Fusion Process (Kulsrud, 1982) D + T → 4 He + n MeV S = ½ S = 1 S = 3/2 S = ½ 95% – 99% D + T → He 5 (3/2 + ) → He 4 + n 1% – 4% S = 3/2 3/2 1/2 -1/2 -3/2 S = 1/2 1/2 -1/2 4 states 2 states 2/3 of the interactions contribute to the reaction rate If D and T are polarized then - all interactions contribute - n have preferential directions Sin 2 (θ) 50 % Increase in released energy The question is to know if the polarization will persist in a fusion process ? ( J/g)

Plasma Density n = (cm -3 ) ; Confinement Time τ = 10 (sec) Lawson Criterion (n τ > (sec/cm 3 ) Fusion by Magnetic Confinement – (ITER) ITER Plasma Volume = 873 m3 τ = 300 (sec) Power = 500 MW (input 50 MW)

Fusion by Inertial Confinement – (MEGAJOULE) Plasma Density n = (cm -3 ) ; Confinement Time τ = (sec) Lawson Criterion (n τ > (sec/cm 3 ) ICF Target 3mm radius Carbone & 4 mg cryogenic DT 2000 times compressed 300 g/cm 3 5 keV 825 MJ within 100 ps

Fusion by Magnetic Confinement – (ITER) Persistence of the Polarization - Injection of Polarized D and 3 He in a Tokamak (A. Honig and A. Sandorfi) D + 3 He → 4 He + p MeV (DIII-D Tokamak of San Diego, USA) Expected: 15% increase in the fusion rate - Powerful Laser on a polarized HD target → P and D Plasma P + D → 3 He + γ MeV Expected: Angular distribution of the γ ray Change in the cross section D + D → 3 He + n MeV Expected: Drastic change in the cross section

Powerful Laser (Petawatt) creates a local plasma of p and d ions (5 KeV) 5.5 MeV γ ray from p + d → 3 He + γ 2.45 MeV n from d + d → 3 He + n Tentative Set-Up Polarized HD Target 25 cm 3 H (p) polarization > 60% D (d) vect. polar. > 14% 20 mJ, 160 fs, 4.5 µm FWHM, W/cm3

The “Few-Body” Problem d 1/2 1 p d 3 He γ dσ/dω γ = σ 0 [(1+ cos 2 θ) + b sin 2 θ] * S = 1/2 S = 3/2 σ 0 (10 keV) = 18 µbarn** 100 radiative captures/laser shot ? For polarized plasma, some angular dependence relative to the polarization axis. Questions for the Few-Body specialists: - is the dσ/dω relation correct ? - how large is the parameter « b »? σ n ++ / σ 0 = 0.08 ? Questions for the Few-Body specialists: - Is it really true ? (10 Yes: Part. W. A. & DWBA; 2 No: Reson. Group. Theor.) * Eduard KURAEV (BFKL, Dubna), ** G. J. Schmid PR C52, R1732 (1995) HD Plasma 5 keV 3 He d n

Conclusions Fusion is a MUST for future power plants. We have in Europe (and in France): ITER to study the magnetic confinement and MEGAJOULE for the inertial confinement. The full polarization of DT fuel could increase the reactivity by 50% and control the reaction products direction of emission. The cost of a polarization station (10 6 €) is negligible compared to the cost of a reactor ( € for ITER). A question remains: D and T relaxation time during fusion process ? Kulsrud argued that the depolarization mechanisms are weak in the plasma. We propose “simple” experiments (using existing equipments) to try to answer this fundamental question, at least for the inertial confinement, but reliable theoretical predictions at low energies are needed.

HD Target: NMR Measurements 0.85 T – 1.8 K Back conversion at room temp. for 5 hours is 30%

HD Target: Production Step I: HD purity monitoring – Quadrupole Mass Spectrometer HD quality on the market ? Step II: HD production – Distillation apparatus in Orsay Over 3 month of ageing necessary

Distillation apparatus in Orsay 3 extraction point 3 temperature probe To mass spectrometer Stainless Steel column filled with Stedman Packing: Heater 1 Heater 2

Mass Sectrometer Sample Tanks Distillator Extraction Valves