PolFusion: Polarized Fuel for Fusion Reactors

Transcription

1 PolFusion: Polarized Fuel for Fusion Reactors From the point of view of the nuclear physics, 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 practical use is still far away, mainly due to still open 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 or in inertial confinement. It s a challenging deal providing useful polarized fuel for the purpose of tes4ng the polarized FUSION in present ( future) constrains and contests

2 Quality of life requires electrical consumption Developping world ( 5 billion people) is crawling up UN HDI (United Na4on Human Development Index). The main energy resource in the past few centuries fossil fuel. World Energy Scenario (1996), from World Energy Council (WEC), Interna4on Energy Agency (IEA) and other interna4onal organiza4ons es4mate Coal 230 year, natural gas 63, oil 44 years new report and suggested scenario (Jazz or Symphony). Total resource based also in non convendonal gas and oil extracdon, esdmadon extended to 100 years. Fusion Physics ed. IAEA Vienna 2012

3 From WEC (World Energy Council) reports Fossil fuel global warming Depleting only coal largest emitter of CO 2 Oil and gas reserves: tens of years and political & military conflits Development of fission nuclear reactors pubblic opposition, proliferation, radiative hazard waste, catastrofic Chernobyl like disasters and most recent Fukushima Dai-ichi Alterna4ve clean energy: solar, not suitable for large urban or industrial center, con4nuity, accumula4on waste. Wind, not suitable for large urban or industrial center, con4nuity, accumula4on biofuel (soil erosion, deforesta4on, deser4fica4on, food price Fission (important role, prominent in France) but already men4oned. Fusion: a global approach to a global problem. The holy Graal for primary energy resources: it requires internadonal collaboradon, investments and efforts: ITER

4 No big changes in previsions of the WEC reports on 2014, mostly monitoring on energy trilemma (energy security, energy equity, and environmental sustainability) pushing towards interna4onal collabora4ons and coordina4ons on the energy problems and solu4ons.

5 Fusion Cross-Section: sorted by kinetic ernergy 1 st gen 2 nd gen 3 rd gen 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)

6 Polarized Fusion why? The three reaction generations are sorted according to relative energy (temperature) required for fusion. Energy producdon: Total cross section 1. Genera4on: D + T 4 He + n Polarized fuel 1.a) Increase of total cross sec4on 1.b) differen4al cross sec4on: angular distrib. f(θ) therefore be[er control 2. Genera4on: D + D T + p or 3 He + n Fuel available (30 g m 3 in ocean water) 2.a) Increase? of total cross sec4on 2.b) Like previous one?, but s4ll missing data for a complete descrip4on. 2.c) Possibility to suppresse the reac4on (QSF quintet suppression factor) 3. Genera4on: 3 He + D 4 He + p 3.a) and 3.b) like 1.a) and 1.b) 3.c) Possibility of Neutron lean reactor if D+D 3 The D + D research tokamaks (ITER D + T!). He + n suppressed

7 Can the total cross section of the fusion reactions be increased by using polarized particles? 3 He Polarized Fusion: test bench 3 He + d + d 4 He + p Factor: ~1.5 at 430 kev [Ch. Leemann et al., Helv. Phys. Acta 44, 141 (1971)] t + d 4 He + n Factor: ~1.5 at 107 kev Reactions through the spin channel J π = 3/2 + / s-wave dominated (~96%) H. Paetz gen. Schieck Nuclear physics with polarized particles (Springer Verlag, Berlin, 2012) H. Paetz gen. Schieck, Eur. Phys. J. A 44, (2010) 321 Few-Body Syst. 54 (2013) 2159

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

9 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 From experiments: J π = 3/2 + / S-wave dominated (0.95 < f <1) J π = 1/2 + / S-wave dominated (1-f) σ tot = w(j = 3 / 2)σ 3/2 (J = 3 / 2)+ w(j =1/ 2)σ 1/2 (J =1/ 2) w(j) = J d J t m d m t JM m d,m t 4 He + n 2 N(md )N(m t ) / N(J) m d m t nuclear spin state (d and t) with respect to the magne4c field of the reactor (J d =1, J t =1/2) N frac4onal popula4on of the respec4ve spin state. More clear referencing the sta6s6cal weight to the polariza6on degree

10 Sta4s4cal weight w as func4on of polariza4on degree P (! σ tot = * f # P z ) " D P z T In purely s-wave (f =1) $ &+ (1-f ) 1 P D T z P z % ( ) and in case of completely vector polarized D (P zd = 1,) and T(P zt = 1) + -σ unpol,! σ tot = # P z " D P z T $ &σ unpol % σ tot =1.5σ unpol This is to clarify the importance of the polariza-on. when we talk of 1.5 enhancement in cross sec6on, we re talking about pure S wave interac-on and both fusing par6cle popula6ons fully polarized. This pushes our efforts to as higher as possible polariza-on of the fuel. R.M. Kulsrud et al. Nucl. Phys. 26 (1986) H. Hasuyama et al. Helv. Phys. Acta 59 (1986)

11 Angular distribution of reaction products In purely S-wave approx f =1, B along z, (θ) respect to B (z) dσ ( θ) dω ( ) = " P D zz A zz P % $ D z P T z C zz ' dσ θ # & dω unpol A zz tensor analysing power A zz = - [3 (cos 2 (θ) -1]/2 C zz spin correlation coefficient C zz = - 3 [cos 2 (θ) -2]/2 In the d t reaction with d and t polarized parallel to B σ tot =1.5σ unpol dσ ( θ) dω = 9 4 sin2 θ dσ ( θ ) dω unpol In the case of only d polarized perpendicular to B σ tot = σ unpol dσ ( θ) dω = 1 2 (1+ 3cos3 θ) dσ ( θ ) dω unpol

12 Calculation d t polarized B * Experiments * D and T spin to the confinement field: α and n emi[ed as sin 2 θ respect to B d polarized B * * D spin to the confinement field and T unpolarized: no influence on cross sec4on, but the reac4on products follow (1+3cos 2 θ) Confirmed on mirror reac4on 3 He(d,p) 4 He [Ch. Leeman et al Helv. Phys. Acta 44 (1971) 141]

13 On the table Pol Fusion is 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 nτ 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.

14 Polarized Fusion: a must for ICF J.-P. Didelez et al EPJ Web conf. 59 (2013) & refs DT polarization for ICF at Polfusion meeting 2013 Trento Test on HD (H pol 60 % and D pol 14 %)... can mimic DT σ DT pol = δ σ DT unpol M. Temporal et al.; Igni6on condi6ons for iner6al confinement fusion targets with polarized DT fuel Nucl. Fusion 52 (2012) And 2013 at the Polfusion Mee4ng in trento Megajoule Project Gain (G max ) incr. 45 %, incident laser power (P * ) decr. by 20 % and absorbed energy (E abs )decr. by 15 %.

15 Still open question on 1 st generation 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), it s possible to produce (orto-) and store (frozen) them polarized? R. Engels How polarization behave in magnetic fields? S. Bartalucci How polarization match with existing (and future) project? F. Bombarda Polarization can survive in plasma? R. Gatto Production of polarized ion by laser acceleration? M. Buscher For investigations we follow confortable gas H, D, 3 He, or solid target too (HD), and compare similar spin configuration (DT).

16 PolFusion project: goals for 1 st generation Aim to combine in molecule polarized atoms, preserving nuclear polarization. Tritium not now included: but we can mimic in ½ spin particles. Follow laser acceleration for ion polarized fuel production. This is our challenges already for 1 st generation fusion reaction, but working with D it comes out also possible investigation on 2 nd and 3 rd generation fusion reaction (D + D) D + D is more diffused fuel (30 g m in sea water), and we can test the first three generations. We have the chance to address a neutron free or lean reactor

17 Goals of PolFusion: for 1 st and... following gen.) R. Engels talk M. Bücher talk Finalize the set up of polarized molecules for deuterium produc4on. Measurements of polarized beam from laser accelera4on We ll combine them freezing polarized molecules and by laser accelera4on producing polarized ion.

18 Working with D give us the chance to investigate more for 2 nd and 3 rd generation reactions

19 2 nd D + D T + p 50% (no n) 3 He + n 50%(*) 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: σ = 1 tot 9 (2! σ 1, 1 + 4! σ 1, 0 +! σ 0, 0 + 2! σ 1, -1 ) Quintet Triplet Singlet Singlet 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?)

20 Neutron lean fusion: QSF (Quintet Suppression Factor) Spin alignements allows to enhance or suppress reac4on channels? Ad yasevich 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* σ pol σ unpol = σ singlet 3 / 9σ sin glet = 3 Ad yasevich S S 0 Singlet state allowed

21 QSF: exp. challenge for previsions Deltuva in Nuclear fusion with polarized nucleons Trento Nov 2013

22 3 rd Neutron lean fusion 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 s4ll have n from D + T, T produced in D + D reac4on. To answer to the D D polarized fusion we need to know the cross sec4on of the whole set of orienta4on of the spin T produced in D + D reac4on.

23 D + D cross section: analysing powers A and spin correlation coeff. C 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

24 PolFusion: D D spin dependent cross section Analysing powers: angular distribu6on of reac6on in which only one par6cipant to the reac6on is polarized, therefore we dis6nguish between beam A (b) and target A (t). Spin correla-on coefficients: p (beam) and q (target) required in order to have a real map of how is evolving the spin spin fusion reac6on, and in order to provide data for prevision. This is the another challenge of our project. A. Vasilyev will give a talk on the status of the apparatus and project. This involve also theore-cal studies to address the most usefull and easily observable (P.Krachencko in Polfusion mee6ng in Trento) D D polarized measurements was and s4ll is claimed from many scien4sts to be a complete experiment to fullfill the reac4on for thermonuclear applica4ons, 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 sec4on.

25 The D D setup: A. Vassilyev ABS from Ferrara: ~ a/s ~ a/cm 2 Detector Setup: 4π covered by - large pos. sens. Detectors - (~ 500 single PIN diodes?) POLIS (KVI, Groningen) Ion beam: I 20 µa dd-fusion polarimeter d/s ( E beam 32 kev ) LSP from POLIS Luminosity: /cm 2 s count rate: ~ 60 /h LSP from the SAPIS project 1 month of beam time Till now partial measurements, not in the whole interesting energy range and with lower luminosity available (Deltuva, Schieck, Zhang,Tagishi...

26 Con... clusions Con... vivium ( ) Dante The term convivium" is derived from the La4n convivia and can be translated as feast, symposium. The work is thus a table (banquet), which offers to the par4cipants (those who have a desire to know and understand) a difficult dish (food), accompanied by bread in order to facilitate their assimiladon. The food will match the songs (for us the presentadons), while the bread various explanatory comments. Convivium real) For more confort and -me to discuss togheter, we ll have a buffet lunch here. Accompaining persons are invitated, please fill the list of people during the coffee break.