Development of polarized polymer targets

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1 Sep 09, 2009 evelopment of polarized polymer targets Wang Li Physics epartment, onghua University (PRC), Shanghai, China W. Meyer, Ch.Heß, E.Radtke, G.Reicherz, Institut für Experimentalphysik I, Ruhr-Univerität Bochum,44780 Bochum,Germany T.Iwata, N.oshita, K.Kondo, Physics epartment, Faculty of Science, Yamagata University, Yamagata, Japan N.Horikawa College of Engineering Chubu University, Kasugai,Japan

2 Content s 1. Introduction to both materials Poly(Ethylene-4) Styrene-8, polymerized C2 C88 2. oping Method for NP Radiation - doping Chemical - doping 3. euteron Polymer sample Radiation-doped C2 TEMPO doped C2 TEMPO doped C88 Trityl radical doped C88

3 Introduction to both material Poly(Ethylene-4) dilution factor C2 Styrene-8, polymerized C88

4 Asymmetry Measurements with Polarized Beams & Pure Polarized Targets Pb : beam pol. Pt : target pol. But: All pol. targets have a fraction of unpol. material ef.: Quality factor f = # of polarizable nucleons # of all nucleons in the target solid targets f = He-Gastargets

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6 Frozen Spin Target Material

7 Merits of C2, C88 1. High purity of 0.98, with spin 1 and C with spin 0 3. Short polarization build-up time 1-3 hours 4. Solid State at room temperature 5. Easy formable to any thickness at room temperature low-energy polarized scattering experiments 6. Suitble for e.g nuclear fusion experiment with 20MeV deuteron beam

8 The Principle of ynamic Nuclear Polarization Basic principle: State of lowest energy is favoured 2.5T, 1K Brute Force : Maximize B(15T) and Minimize T(10mk) Trick: Transfer of polarization from particles with high µ 2.5T, 1K Electrons: P = 93% oping with paramagnetic centers: ~ 103 nuclei feeded by 1 unpaired electron from: Chemically stable radical Solids Radiation induced defects Solids

9 oping methods for NP Mechanism of ynamic Nuclear Polarization Paramagnetic centers are needed Chemical (Tempo, Trityl radical) doping Melting point 36ºC Boiling point 67º)C Tempo (stable free radical Irradiation with electron beam Paramagnetic center for NP

10 ESR linewidth and shape Zeeman Energy of a free electron r r EZ g e B S B Contributions to the Electron Zeeman linewidth r r r r Etot B ( S gˆ B ) ( S A I ) { E hom in hom Hom. Inhom. ipol-ipol interaction Hyperfine interaction indep. of B0 Inhom. g-factor anisotropy dep. of B0 Try to minimize the energy spread E tot between electrons magnetic nuclei crystal field Find a suitable doping method Try radiation doping if only low μ nuclei present

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12 EPR spectra of irradiated CH2 and C2 at 77K Alkylradical According to HFS, 6-line pattern conresponds to ,, L H, adjacent m= mT splitting of HFS interval belongs to Hα Splitting broadening 1.56mT mainly belongs to electron 0 dipolar-dipolar interaction

13 EPR spectra of Radiation-doped C2 According to HFS, 11-line pattern corresponds to 5 adjacent, 0

14 Polarization of radiation-doped C2 NMR Signal of euteron Bochum Group (2002

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16 Polarized target system Cooling system ~ 100mK Magnet system 2.50T C-yoke normal conduction magnet (JM-611made by JEOL) homogeneity: (ø70mm 25mm) Microwave system 70GHz Oscillator: 68.5GHz-71.5GHz 150mW (IMPATT H-1115 made by HUGHES) NMR measurement system Larmor frequency of : 16.35MHz igital Synthesizer: 1MHz-250MHz Accuracy: 0.1MHz (PTS250 made by PTS inc.) L=590nH

17 EPR spectra of TEMPO-doped C2 Introduce TEMPO Radicals in CC 2 2 foil into a vessel Tempo and without touching each other 80ºC diffusion from TEMPO vapour Structure of Polyethylene C2

18 Polarization of TEMPO-doped C2 NMR Signal of euteron Nagoya Group (1998)

19 EPR spectra of TEMPO-doped C88 X-band Bolometri c Introduce TEMPO Radicals in C88 1. dissolve C88 polymer in toluene 2. add free radical 3. let the toluene evaporate at RT Styrene-8, polymerized C88

20 Polarization of TEMPO-doped C88

21 Introduce Trityl radical Trityl radical as dopant for -Butanol Boiling point >200ºC Very stable radical Weak g-factor anisotropy in -Butanol g : g Bochum Group (2003)

22 EPR spectra of Finland 36-doped C88 X-band Introduce Finland 36 Radicals in C88 1. dissolve C88 polymer in toluene 2. dissolve Finland 36 in isobutanol 3. mix and evaporate solvents Bolometric

23 TE signal of Finland 36-doped C88

24 Polarization of Finland 36-doped C88

25 Polarization of Finland 36-doped C88 g : g

26 Summary 1. The maxium polarization of deuterated Polyethylene is 30% with electron irradiation of e-/cm2. ue to EPR spectra,unpaired electrons produced by irradiation have Hyperfine interaction with 5 adjacent H or nuclei. 3. euterated Polystyrene doped with trital radical (Finland 36) was successfully developed and the maximum polarization is 12.3% at 2.5T/1K and more than 20% at 5T/1k. 4. Relative small anisotropy g factor of Polystyrene with Finland 36 is about 3*10E(-4). 5. Concerning the almost similar frequency distance between positive and negative polarization and the enlarged bolometric line width at 2.5T and 5T, the relaxation times of the electronic system is no dependence of magnetic field at NP

27 euteron Polymer Polarization

28 outloo k Maximum Polarization measurement at dilution refrigerator (-Polystyrene+ Finland 36) 2. Optimal magnetic field for euteron (-Polystyrene+Finland 36) (6.5T) 3. Optimal density for euteron (-Polystyrene+Finland 36) (1.5%,1.8%,2.5% samples) 4. Try sample of euteron (-Polyethylene+Finland 36) using solvent of 1-Pentanol,n-heptane 5. Try 1cm thickness target for GH experiment in Spring-8 6. Try bolometric measurement at high polarization of euteron.

29 ACKNOWLEGEMENTS r.stefan Goertz Bonn University Florian Piegsa PSI Group

30 Thank your attention!

31 The Solid State Effect ipolar Coupling B = 2.5 T Positive Negative

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34 Material Radical g/g [10 3] FWHM [mt] at 2.5T P,max [%]

35 fusion experiment Result of unpolarized beam with polarized target Temperature of C2 : 800 mk Magnetic field :2.5T Current of magnet: 81.10A Microwave Frequency: 70.03GHz from Asymmetry of scattering angle