The molecular beam source to produce polarized H 2 /D 2 beams

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1 The molecular beam source to produce polarized H 2 /D 2 beams Dmitriy Toporkov Budker Institute of Nuclear Physics, Novosibirsk State University Novosibirsk, Russia. Meeting Polarized Fusion 2017 February1-2,2017 at BINP BINP NSU Polarized Fusion D.Toporkov 1

Fusion Energy (LIFE) Polarized fuel can to increase an efficiency of the power production.

2 Fusion is the most valuable source of energy for the future ITER, JULY 2016 International Thermonuclear Experimental Reactor the world's largest magnetic confinement plasma physics experiment Laser Inertial Fusion Energy (LIFE) Polarized fuel can to increase an efficiency of the power production. Polarized targets are also demanded for the investigation of the forces between the nuclei Polarized Fusion D.Toporkov 2

3 Sources of polarized atoms The sources of polarized atoms (ABS) has been developed from the early 50 th. Clausnitzer was the first who got a polarized proton beam using an ABS with quadrupole focusing magnets. The intensity of polarized atomic beam was approximately 10¹¹ at/sec. [G. Clausnitzer, R. Fleischman, H. Shopper, Zs. F. Physik 144 (1956) 336] Since there fast developing of this technique now reached a limit in the intensity of polarized atoms. The best sources deliver about 10¹⁷ at/sec Polarized Fusion D.Toporkov 3

4 Geometrical solid angle is important Polarized Fusion D.Toporkov 4

5 Parameters and intensity for different ABS ABS W geom. (sr) = pr 2 mag./l 2 n-mag. W mag. (sr) = pmb/kt nozzle W average = W g. W m. /( W g. + W m. ) Intensity H / D at/sec Wisconsin ABS NIMA336(1993)410 FILTEX ABS NIMA343(1994)334 HERMES ABS NIMA496(2003)277 ETH ABS (NIKHEF) electromagnets NIMA378(1996)40 ETH ABS (NIKHEF) perm. magnets NIMA455(2000)769 Cryogenic ABS NIMA495(2002)8 RHIC ABS NIMA536(2005)248 NIMA556(2006)1 ANKE ABS NIMA721(2013) * * * *10 16 total H 6.7*10 16 d10mm H 2.38* * * *10 16 d10mm H 1.73* * * *10 16 d10mm H 5.0*10 16 D 2.5* * * *10 16 d 12mm H 1.6*10 16 D 2.29* * * *10 16 max H 6.4*10 16 d 12mm H 4.5*10 16 D 4.3* * * *10 16 total H 8.2*10 16 D 2.36* * * *10 16 total H 3.14* * * *10 16 d 10mm H 3.9*10 16 D Polarized Fusion D.Toporkov 5

6 M. STANCARY Polarized Fusion D.Toporkov

7 At large distances or low temperature of the beam intrabeam scattering limits the intensity. FILTEX ABS, 1991 T.Wise et al. NIMA 336(1993) 410 Intensities of the free hydrogen molecular beams Polarized Fusion D.Toporkov 7

8 How to increase the intensity of polarized beams? To overcome intrabeam scattering: Low density in the beam, Free molecular flow, Large aperture of the source. All these features are not suitable for ABS. It could be possible for molecular beam with large aperture? Polarized Fusion D.Toporkov 8

9 Ortho and parahydrogen Polarized Fusion D.Toporkov 9

10 The hyperfine energy levels of hydrogen molecule as a function of the magnetic holding field (Breit-Rabi diagram). These substates can be focused in inhomogeneous magnetic field Magnetic moment of H 2 =2.78*10-23 erg/g = 2.5*10-3 m Б Magnetic moment of D 2 =6*10-24 erg/g = 6.5*10-4 m Б D 2 =3.85*10-24 erg/g = 4.15*10-4 m Б D 2 =1.88*10-24 erg/g = 2.0*10-4 m Б Polarized Fusion D.Toporkov 10

11 Geometry selection a F = mr = - W = m B/ r=c ṙ = υᵣ = C t/mυ t= L/υ υᵣ = C L/(m υ) a = υᵣ/υ = C L/(m υ ) C L/(k T) -3 For our case m = mb, T 8K, L=19.5 cm, B/ r = 32 kg/cm.. -3 a = rad Polarized Fusion D.Toporkov 11

12 L d d/l= 1/365= a = Polarized Fusion D.Toporkov 12

13 Novosibirsk Cryostat Cryogenic Liquid Atomic nitrogen Beam Source Turbo pump Tensor polarization Vector polarization Polarized Fusion D.Toporkov 13

14 Superconducting sextupole magnets with constant aperture 42 mm inner diam. used in ABS Polarized Fusion D.Toporkov 14

15 Polarized molecules source based on existing cryogenic ABS Polarized Fusion D.Toporkov 15

16 Experimental setup to obtain polarized molecules Polarized Fusion D.Toporkov 16

17 The source of polarized hydrogen molecules at the test bench Polarized Fusion D.Toporkov 17

18 Source of cold hydrogen molecules ring slit 0.1 mm width diameter 41 mm Copper block Polarized Fusion D.Toporkov 18

19 The source with sensor and heater teflon insulater heater thermo sensor Polarized Fusion D.Toporkov 19

20 The source with gas inlet connected Gas inlet Polarized Fusion D.Toporkov 20

21 Source installed inside the ABS Tube with liquid helium Polarized Fusion D.Toporkov 21

22 The entrance slit to a focusing magnet Cold surface up to 2.5 K 1 mm width ring slit outer diameter 42 mm inner diameter 40 mm Polarized Fusion D.Toporkov 22

23 Distribution of the beam intensity at compression tube location (simulation) 0,06 0,05 0,04 0,03 0,02 Ряд1 0, Position of the compression tube (cm) -0,01 No beam intensity measured by compression tube at the beam axis in the assumption that molecules touched the cold surface are pumped Polarized Fusion D.Toporkov 23

24 3,5 3 Intensity distribution for H2 2,5 2 1,5 Ряд1 1 0, Position of the compression tube (mm) Polarized Fusion D.Toporkov 24

25 Additional diaphragm 35 mm in diameter Polarized Fusion D.Toporkov 25

26 CO beam profile measured with additional diaphragms diam.diaph. 30 mm diam.diaph. 35 mm 0 Horizontal position of the compression tube (mm) Polarized Fusion D.Toporkov 26

27 CO beam profile measured with additional diaphragm 2 7 Vacuum in comp. tube vs. position 6 V a c u u m 1 0 * * _ 8 T o r r Q=10**18 mol/sec Q=10**19 mol/sec position (mm) Polarized Fusion D.Toporkov 27

Comparison of the focusing efficiency for hydrogen and deuterium molecules -26-26 m p = 1.4*10 J/T m d = 0.

28 Comparison of the focusing efficiency for hydrogen and deuterium molecules m p = 1.4*10 J/T m d = 0.43*10 J/T H D 2 2 Magnetic moment of H 2 = 2.5*10-3 m Б Magnetic moment of D 2 = 6.5*10-4 m Б Polarized Fusion D.Toporkov 28

29 Correlation between the magnetic field and the intensity of the focused beam Polarized Fusion D.Toporkov 29

30 Intensity of the H2 beam while ramping the magnet for different nozzle temperature (computer screen) 7.5K 6.5K 11K 30K 6?? Polarized Fusion D.Toporkov 30

31 Intensity (arb. unit) Intensity of the focused beam vs the magnetic field (calculation) 6K 7K 8K 30K 30K 8K 7K 6K Magnetic field (kg) Polarized Fusion D.Toporkov 31

32 Polarized Fusion D.Toporkov 32

33 Pressure ( 10**-9 Torr) 1,6 Background pressure in compression tube and pressure change due to magnetic field vs the flux through the nozzle Tnozzle=7.3 K 1,4 1,2 1 Background pressure 1 0,8 0,6 2 Pressure change due to magnetic focusing 0,4 0, ,01 0,02 0,03 0,04 0,05 0,06 H2 flux through the nozzle (Torr*l/s) Polarized Fusion D.Toporkov 33

34 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 Flux of focused molecules into the compression tube and the ratio of fluxes vs the flux through the nozzle. T nozzle = 7.3 K helix are installed Flux of polarized molecules into compression tube due to magnetic fucusing ( 10**-7 Torr*l/s) Ratio of flux into compression tube to the flux through the nozzle (10**-5) 0, ,01 0,02 0,03 0,04 0,05 0,06 H2 flux through the nozzle (Torr*l/s) Polarized Fusion D.Toporkov 34

35 Monte Carlo simulation Maxwell Boltzmann velocity distribution at 8 K for hydrogen Cos(q) intensity distribution from the source Flux of focused molecules into the compression tube Q comp. tube -6 = 2.1*10 Q nozzle Experiment (comp. tube in a center position) Q comp. tube -6 = (3-1) *10 Q nozzle Polarized Fusion D.Toporkov 35

36 delta P gauge (10**-9 Torr) 0,9 0,8 0,7 Intensity of the focused beam vs Tnozzle for different fluxes ,6 0,5 0,4 0, ,0097 0,027 0,04 0,051 0,2 0, Flux (Torr*l/s) 0 0 0,02 0,04 0,06 0,08 0,1 0,12 0,14 0,16 0,18 1/Tnozzle (1/K) Polarized Fusion D.Toporkov 36

37 delta P gauge (10**-9 Torr) 0,8 0,7 Intensity of the focused beam vs flux for different T nozzle 6.5 K 7.5 K 0,6 0,5 0,4 0,3 0,2 11 K 30 K T nozzle 30K 11K 7.5K 6.5K 0, ,01 0,02 0,03 0,04 0,05 0,06 flux (Torr*l/s) Polarized Fusion D.Toporkov 37

38 Why the intensity of the focused beam is going down with the increasing of the flux through the nozzle while the background signal is increasing? Attenuation of the beam by the residual gas this effect could be investigated by injected additional gas into the chamber Directivity of the flow from the nozzle is falling down with increasing the flux Probably at higher pressure in the nozzle clusters of molecules are producing which not focused by the magnetic field Polarized Fusion D.Toporkov 38

39 Luca Barion Istituto Nazionale di Fisica Nucleare Polarized Fusion D.Toporkov 39

40 ATTENUATION OF THE BEAM BY RESIDUAL GAS The pumping speed of cryopanels in the region between the nozzle and the magnet is about 200(cm 2 ) x 20 l/s ~ 4000 l/s. Flux of molecules Torr l/s. So the pressure P= Torr, which correspond the density mol/cm 3 (T~ 100K). The distance L between nozzle and magnet is 35 cm. Thickness of the residual gas is n L = mol/cm 2. The cross section of H 2 -H 2 scattering is σ = cm 2 for 80 K molecular beam. In our case beam temperature is 8 K and the cross section is even bigger. I=I 0 exp-n L σ= I 0 exp-0.525= I Polarized Fusion D.Toporkov 40

41 What to do in the nearest future To avoid the difficulty with alignment Test the molecular source with higher directivity capillaries or multi slit nozzle Different dimensions of the entrance slit in the sextupole magnet Design and manufacture of the ionizer Widening of the experimental area Polarized Fusion D.Toporkov 41

42 New system for the nozzle and diaphragm installation nozzle diaphragm Polarized Fusion D.Toporkov 42

43 Future prospect Understanding the process of molecules reflection from the cold surface Measurement of the polarization of molecules using Lamb-shift polarimeter Directivity of the molecular beam Design a prototype of a new source Polarized Fusion D.Toporkov 43

44 Possible setup of future polarized hydrogen molecules source area ~ 6000mm 2 D 40 cm Polarized Fusion D.Toporkov 44

45 Conclusion The measured flux of focusing molecules is close to the expected one More investigation should be done to get optimal molecular flux from the CABS This and further investigation will be done under the joint RSF-DFG grants and BU 2227/ Polarized Fusion D.Toporkov 45

46 A team working on polarized molecular source Polarized Fusion D.Toporkov 46

D- Charge Exchange Ionizer for the JINR Polarized Ion Source POLARIS

D- Charge Exchange Ionizer for the JINR Polarized Ion Source POLARIS V.P. Ershov, V.V.Fimushkin, G.I.Gai, L.V.Kutuzova, Yu.K.Pilipenko, V.P.Vadeev, A.I.Valevich Λ and A.S. Belov Λ Joint Institute for Nuclear