Introduction to Polarized Fusion

Transcription

1 Introduction to Polarized Fusion G.Ciullo Physics department and Earth Science University of Ferrara and INFN (National Institute of Nuclear Physis) Ferrara ITALY 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? G. Ciullo 1

2 Spin against bowling game Spin game Bowling game 2

3 Polarized Fusion : Fusion with Nuclear Polarized Fuel 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 G. Ciullo 3

4 Quality of life : requires electrical consumption from Fusion Physics ed. IAEA Vienna 2012 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 new report and suggested scenario (Jazz or Symphony). Total resource based also in non conventional gas and oil extraction, estimation extended to 100 years. G. Ciullo 4

5 From WEC (Wolrd Energy Council) reports Fossil fuel global warming Depleting only coal largest emitter of CO 2 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 G. Ciullo 5

6 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 Polarized Fusion the 2017 energy - problems and solutions. G. Ciullo 6

7 Mostly the 2DS (2 degree scenario) is scaring the society G. Ciullo in Nuclear physics with polarized Fuel (Springer International Publishing, Switzerland, 2016 G. Ciullo 7

8 How the polarized fusion can helps? 1 st gen 2 nd gen 3 rd gen Polarized Fusion 2017 D-D to start fusion, T produced by n on blanket (containing Litium) 6 Li + slow n -> T + 4He MeV (exoe) 7 Li + fast n -> T + 4He 2.5 MeV + n slow (endoe) G. Ciullo 8

9 Polarized fusion: test bench 3 He+d reaction Can the total cross section of the fusion reactions be increased by using polarized particles? 3 He + d Þ 4 He + p Factor: ~1.5 at 430 kev [Ch. Leemann et al., Helv. Phys. Acta 44, 141 (1971)] t + d Þ 4 He + n Factor: ~1.5 at 107 kev Reactions through the spin channel J p = 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 G. Ciullo 9

10 Cross-section enhancement factor 1.5 Unpolarized cross section = weighted sum of all channel spin s s unpol = ås å s (2s+1) s s (2s+1) s unpol = 2s s = 1 3 s s 3 2 For both reactions channel spins can be 3/2 and 1/2. From experiments: both reactions proceed via the J p = 3/2 + ( 5 He* and 5 Li*). At low energy the incaming l =0, S-wave dominate: Only the 3/2 contributes to the s unpol, if the incoming particles are both polarized: gain = s pol s unpol = s / 3s 3 2 = 1.5 G. Ciullo 10

11 Enhancement: test bench 3 He + 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 nt E > sec cm -3 for ignition in fusion reactor t + d Þ 4 He + n From experiments: J p = 3/2 + / S-wave dominated (0.95 < f <1) J p = 1/2 + / S-wave dominated (1-f) s tot = w(j = 3/ 2)s 3/2 (J = 3/ 2)+ w(j =1/ 2)s 1/2 (J =1/ 2) å w(j) = J d J t m d m t JM m d,m t 2 N(md )N(m t ) / N(J) m d m t nuclear spin state (d and t) with respect to the magnetic field of the reactor (J d =1, J t =1/2) N fractional population of the respective spin state. More clear referencing the statistical weight to the polarization degree G. Ciullo 11

12 Statistical weight w as function of polarization degree P é æ s tot = ê f ç P z ë è In purely S-wave (f =1) and in case of completely vector polarized D (P zd = 1,) and T(P zt = 1) æ s tot = ç P z è D P z T D P z T ö + (1-f ) 1- P D T z P z ø ( ) ö s s unpol tot =1.5s unpol ø 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. G. Ciullo 12 ù ús unpol R.M. Kulsrud et al. Nucl. Phys. 26 (1986) H. Hasuyama et al. Helv. Phys. Acta 59 (1986) û

13 Angular distribution of reaction products In purely S-wave approx, f =1, B along z, (q) respect to B (z) ds ( q) dw ( ) = P D zz A zz P æ D z P T z C zz æ ds q dw unpol A zz tensor analysing power A zz = - [3 (cos 2 (q) -1]/2 C zz spin correlation coefficient C zz = - 3 [cos 2 (q) -2]/2 In the d t reaction with d and t polarized parallel to B s tot =1.5 s unpol ds ( q) dw = 9 4 sin2 q ds ( q ) dw unpol In the case of only d polarized perpendicular to B s tot =s unpol ( ) dw ds q = 1 2 (1+3cos3 q) ds q G. Ciullo 13 ( ) dw unpol

14 Calculation d t polarized B * Experiments * D and T spin to the confinement field: a and n emitted as sin 2 q respect to B d polarized B * * D spin to the confinement field and T unpolarized: no influence on cross section, but the reaction products follow (1+3cos 2 q) G. Ciullo Confirmed on mirror reaction 3 He(d,p) 4 He [Ch. Leeman et al Helv. Phys. Acta 44 (1971) 141] 14

15 On the table Polarized Fusion seems very promising 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 nt E and T i 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 = P fusion /P input =1.63: new design optimization. G. Ciullo 15

16 Still opend questions? Tritium is radioactive T 3 He + e + anti-n e, (t 1/2 =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 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 G. Ciullo 16

17 2 nd D+D T + p / 3 He + n Fusing D + D, then D + T can fuses (n) 3 He does not contribute at the ignition energy of D-D The total cross section D + D in respect to the incoming polarization of the fusing particles: Hjgher energy for fusion involev also P-, D- wave, togheter with S-wave and their interferences D + D spin dependent cross section (data set very poor), and stilll worse at lower energy (electron screening?) G. Ciullo 17

18 Neutron Lean fusion? QSF (Quintet Suppression Factor) Spin alignements allows to enhance or suppress reaction channels? D (d p) T and D (d n) 3 He suppressed by choosing deuteron spin parallel each others S S 2 Quintet State Suppressed D D 4 He* S S 0 Singlet state allowed G. Ciullo 18

19 3 rd Neutron lean reactors? D + 3 He 4 He + p? Can we have neutron free reactor? The spin configuration is 1 + ½, like the T + D, and was the confirmed measurements already in the 1971 If we suppress or reduce D-D fusion, we could have neutron free or lean reactors 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. G. Ciullo 19

20 D + D cross section: experimental test? A. Vasilyev Spins of both deuterons aligned: only p z (q z ) and p zz (q zz ) 0 Only beam is polarized: (p i,j 0, q i,j = 0) σ(θ,φ) = σ 0 (ϴ) {1 + 3/2 A y (ϴ) p y + 1/2 A xz (ϴ) p xz + 1/6 A xx-yy (ϴ) p xx-zz + 2/3 A zz (ϴ) p zz } H. Paetz gen. Schieck, Eur. Phys. J. A 44, (2010) 321 G. Ciullo 20

21 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. G. Ciullo 21

22 more will be discussed in this meeting, but Springer international Publishing G. Ciullo 22