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Polarized Proton Solid Target at high-T and low-B

Polarized Proton Solid Target at high-T and low-B

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Polarized Proton Solid Target at high-T and low-B

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  1. Polarized Proton Solid Targetat high-T and low-B Tomohiro Uesaka Center for Nuclear Study, Tokyo

  2. Outline • Polarization study of nuclei spin-orbit coupling in nuclei early experiment by O. Chambalain motivation to RI beam studies • Polarized proton solid target at high-T and low-B use of photo-excited triplet state of aromatic molecule • Future plan RI Beam Facility at RIKEN • Summary

  3. Spin-orbit force in nuclei Mayer & Jensen claimed in 1948 strong spin-orbit force: necessary to account for the magic numbers one order stronger than the Thomas term O. Chamberlain et al. Phys. Rev. 102 (1956) 1659. measured Ay (Py) for p- He/Be/C/Al/Ca/Fe/Ta through double scatt.method → direct evidence of spin-orbit force E. Fermi , Nuovo Cimento 10 (1954) 407. VLS deduced from the scattering experiment is consistent with that required by the shell model Polarization scattering angle [deg]

  4. Initiation of polarization study from Jefferies's Textbook Polarized ion source (~1956) Claussnitzer, Fleishmann → spectroscopy of single particle states via (d,p)/(p,d) reactions. → clarify the role played by spin dependent interactions Polarized target (DNP) O. Chamberlain et al. Bull. Am. Phys. Soc. 8 ('63) 38. La2Mg3(NO3)12 24H2O B = 1.8 T T = 1.2 K P ~ 50%

  5. Spin dep. interaction Basic regularity in nuclei ← spin dependent interaction shell structure ← spin-orbit force magic numbers: 2, 8 , 20, 28, 50, 82, 126. . . . saturation ← tensor force same density (0.17 nucleon/fm3) everywhere pairing of like particles Polarization studies have made great contributions to clarify manifestations of spin dependent interactions in nuclei.

  6. Physics far from the stability line New data from experiments with RI beam → "basic" regularities are valid only locally in the vicinity of the stability line. J=0 pairing of unlike particles change of shell structure: disappearance of "old" magic numbers appearance of "new" magic numbers halo: low density neutron matter

  7. Polarized Proton Targets for RIB Requirements on the polarized proton target for RI beam exp. RI beam : Low intensity of < 106 Hz high-density solid targetgas target any p solid target: compound including hydrogen atoms detection of recoiled protons: essential for event ID 5 MeV proton: range < 0.2mm in Al Br = 0.33 Tm conventional p targets at low T(<1K) and at high B (>2.5T) places serious difficulty in proton detection. B=2.5 T → r ~ 13cm Solutions spin frozen target (Oak Ridge-PSI collaboration) new technique to polarize at low-B and high-T

  8. Electron polarization depends neither on B nor T Proton Pol. at low-B and high-T Idea: use of electron polarization (population difference) in photo-excited triplet state of aromatic molecule H.W. van Kesteren et al., Phys. Rev. Lett. 55 (1985) 1642. A. Henstra et al., Phys. Lett. A 134 (1988) 134. Energy diagram of pentacene molecule mixing due to spin-orbit int. in molecule

  9. Electron population difference y z B // x : Pmax = 73% B // y : Pmax = 48% B // z : Pmax = 70% Pentacene molecule x B // x B // y B // z 0.12 0.45 0.46 Population 0.76 0.16 0.08 0.12 0.46 0.39 Crystal alignment is essential for large polarization

  10. pentacene Host materials Naphthalene C10H8 p-terphenylC18H14 density 1.16 g/cm3 pentacene concent. 0.01 mol% melting point 80.2 deg. density 1.24 g/cm3 pentacene concent. 0.1 mol% melting point208 deg. naphthalene @0.09 T J. U. von Shuetz et al. Z. Nauturforsch. 22a, (1967) 643. p-terphenyl @0.46 T Relaxation rate [/min] K. Kouda et al. J. Phys. Soc. Jpn. 51, (1982) 3936. low T : naphthalene high T : p-terphenyl Temperature [K]

  11. Technical aspects Optical pumping pol. light is not necessary broad spectral width : less demands on laser Ar-ion laser, dye laser, YAG laser, etc. Polarization transfer to protons at low B cross polarization method (Hartmann & Hahn, PR 128 (1962) 2042.) high efficiency even at low B Cooling operation temperature ~ 100 K blow of cold nitrogen gas is sufficient → decrease materials around the target

  12. Application to Part. & Nucl. Physics Masaike, Iinuma et al. (Kyoto) M. Iinuma et al., Phys. Lett. A 208 (1995) 251. M. Iinuma et al., Phys. Rev. Lett. 84 (2000) 171. K. Takeda et al., Chem. Phys. Lett. 345 (2001) 166. applied this novel technique to neutron beam experiments naphthalene+pentacene T=77K B=0.3T Laser: dye laser, 350 mW

  13. Optical pumping by Ar-ion Laser System for basic study with Ar-ion laser T. Wakui et al., NIM A 526 (2004) 182 & NIM A 550 (2005) 521. Polarization in p-terphenyl at 0.3T, room temperature Polarization in naphthalene at 0.3 T, 100K Polarization [%] Polarization [%] crystal size 4×4×3mm3 Time [min] Time [hours] 4.8±1.2% enhancement factor > 5×104

  14. Development for RI beam exp. • production of large single crystal and shaping it to thin disk with large diameter. 14mmφ, 1mm-thickness • thin microwave resonator (f = 2-3GHz) copper film loop gap resonator • improvement of NMR sensitivity • reduction of material around the target target cooling with blowing cold N2 gas • evaluation of radiation damage due to HI irradiation • polarization measurement with p-4He scattering thermal polarization measurement: impossible

  15. Target system & Polarization Polarization at 0.08T and 100K small effects of radiation damage RI beam laser light

  16. First experiments effects of excess neutrons on spin-orbit potential? proton elastic scatterings on helium isotopes 4He 6He 8He N/Z=1 N/Z=2 N/Z=3 rm =1.49 fm rm=2.30 fm rm=2.45 fm S2n=28.3 MeV S2n=1.86 MeV S2n=2.58 MeV halo (or skin?) skin

  17. p-6He Elastic scattering at 71 MeV/u Theoretical predictions before the measurement Preliminary results at RIPS, RIKEN There exists something beyond our current understandings. The effect appears only in spin polarization data. Measurement for 8He is planned in 2007. S. P. Weppner et al. Phys. Rev. C 61 (2000) 044601. Sakaguchi et al.

  18. RI Beam Factory at RIKEN high resolution SHARAQ Spectrometer Use of the polarized target enhances scientific opportunities with RI beam at RIBF. proton elastic scatterings (p,pN) reactions for spectroscopy of single hole states (p,p') and (p,n) reactions to deduce spin responses

  19. Summary A new technique to polarize protons at low-B and high-T is developed. by use of photo-excited triplet state of aromatic molecule. The proton polarization has been applied to a radioactive nuclear beam experiment at RIPS, RIKEN. p-6He elastic scattering at 71 MeV/u The result is beyond our current understandings. Scientific opportunities with radioactive isotope beams are expanding. It should be exciting to shed a light of POLARIZATION to the field. Polarization of radioactive nuclei: P. Mantica, H. Ueno etc. Scattering of polarized protons: this talk, Oak Ridge-PSI A role played by spin physics community is very important. spin physics community ⇔ heavy ion physics community

  20. Collaborators CNS, Tokyo T. Wakui (→CYRIC), S. Sakaguchi, T. Kawabata, K. Suda, Y. Maeda, Y. Sasamoto, T. Uesaka Dep. of Physics, Tokyo M. Hatano (→Hitachi), H. Sakai, K. Yako, H. Kuboki, M. Sasano, H. Iwasaki, Y. Ichikawa, D. Suzuki, T. Nakao Toho University T. Kawahara Saitama University K. Itoh RCNP, Osaka University A. Tamii CYRIC, Tohoku University H. Okamura, M. Itoh, R. Matsuo, M. Ichikawa Tokyo Institute of Technology Y. Satou, Y. Hashimoto, M. Shinohara RIKEN N. Aoi, K. Sekiguchi, M. Yamaguchi

  21. BACKUP

  22. Research plans at RIBF RIBF energy: 150-350 MeV/u nuclei are most transparent. Proton elastic scattering Spectroscopic studies with (p,pN) reactions →unambiguous determination of the spin-orbit splitting Spin responses of unstable nuclei via (p,p') and (p,n) reactions

  23. Method of Effective Polarization KEYS: ・ Large spin correlation in N-N scattering, Cy,y~0.8, at E/A~200 MeV s↑↑ ≫ s↑↓ →incident proton interacts mostly with nucleon with the same spin ・ Distortion to recoiled (low energy) nucleon if recoiled nucleon goes into the target nucleus →absorbed pN < 0 if pN < 0 Ay < 0 for j> Ay > 0 for j< L proton with spin↑ j> R L j<

  24. p1/2 p3/2 Method of Effective Polarization 16O(p,pp) @ 215 MeV G. Jacob et al., Phys. Lett. B 45 (1973) 181. P. Kinching et al., Nucl. Phys. A 340 (1980) 423. d3s/dW1dW2dE Ay 16O(p,pp) @ 200MeV pN

  25. (p,pN) at RIBF E/A = 200-250MeV: best energy for the study 1) weak distortion for incoming and scattered proton Ep=150-250MeV 2) modest absorption for recoiled nucleon EN=50-100MeV 3) large spin-correlation parameter in N-N scattering Cy,y ~ 0.8 4) reaction theory established relativistic DWIA G.C. Hillhouse et al. Cy,y for p-p scattering Ep [MeV] q [deg]

  26. Spectroscopy of particle/hole state Shell regularity in the region far from the stability line how p (n) spin-orbit splitting depends on n (p) number? Experimental approach: nucleon transfer reactions →low energies nucleon knockout reactions →intermediate energies: RIBF Ej<-Ej'> Is the Nuclear Spin-Orbit Interaction Changing with Neutron Excess? J. P. Schiffer et al., PRL 92 (2004) 162501. N-A

  27. Experiments at RIBF (p,pp) Ni , Sn, Ca isotopes (p,pn) N=50, 28 isotones proton detectors SHARAQ from BigRIPS neutron detectors

  28. p-8HeElastic Scattering R. Crespo et al., PRC 51 (1995) 3283. p+8He full core

  29. Polarized proton targets by DNP Transfer thermal polarization of electrons to protons by microwave irradiation large magnetic moment of electron → large Pe at low-T (<1K) and high-B (>2.5T) hyperfine interaction between electron and proton rapid spin relaxation of electrons slow spin relaxation of protons Solid effect (or Overhauser effect) A.W. Overhauser Physical Review 92 (1953) 411. [1] C.D. Jefferies, Dynamic Nuclear Orientation (1963) [2] A. Abragam, The Principles of Nuclear Magnetism (1961) [3] A. Abragam and M. Goldman, Nuclear Magnetism: Order and Disorder (1982)

  30. Magic numbers 2, 8, 20, 28, 50, 82, 126 . . . . believed to be universal throughout the nuclear chart. BUT, this has proven not to be true. ←new data from radioactive nuclear beam experiments

  31. Reactions with spin-polarized probes Invention of polarized ion source (1956) by Claussnitzer, Fleishmann →drastic progresses in polarization study firm basis of LS potential local and global optical potentials VLS ~ 5 MeV weak dependence on E, A A.J. Koning & J.P. Delaroche Nuclear Physics A 713 (2003) 231. n-56Fe

  32. 新光源: 高輝度発光ダイオード Luxeon社 ~100 mW @300mA 波長: 590nA 時間構造: 電流で制御 安価 (2000円/個)

  33. Polarized proton solid target Many deep inelastic scattering experiments EMC(→SMC)→COMPASS @CERN SLAC Production of spin-polarized neutron (ex. KEK) large difference between s↑↑and s↑↓ Nuclear physics experiments CNS group →unstable nuclear physics experiment

  34. Gyromagnetic Ratio ratio of magnetic moment to angular momentum for electron and proton

  35. 結晶近傍

  36. 装置の全貌

  37. Detailed Study of Radiation Damage Polarization is determined by competition of A and G The damage can be cured at temperature higher than 200K. Radiation damage due to HI irradiation before irradiation0.1 h-1 after irradiation0.3 h-1 (2×1010)

  38. Early work at Leyden Schmidt group at Leyden H.W. van Kesteren et al., Chem. Phys. Lett. 89 (1982) 67. Chem. Phys. Lett. 121 (1985) 440. Phys. Rev. Lett. 55 (1985) 1642. Fluorene + Phenanthrene 固体効果 (低磁場では効率悪い) Pp ~ 2% @ 0.3T, 1.2K →42% @ 2.7T, 1.4K P~2%

  39. Polarization at Lower Field A. Henstra et al., Leyden group A. Henstra et al., Phys. Lett. A 134 (1988) 134. A. Henstra et al., Chem. Phys. Lett. 165 (1990) 6. Naphthalene + Pentacene Cross polarization method efficient even at low magnetic field 29Si:B T=1.2K B=0.264T

  40. ナフタレンの純化 ゾーン・メルティング法 融点以上のゾーンを通過させる 不純物が偏析する 10mm/h ヒーター(molten zone) 不純物 液化領域 (90 C) 固体領域 (25 C) 純化されたナフタレン 不純物 (Benzo thiophene)

  41. 単結晶の製作 ブリッヂマン法 1 mm/h シリコン オイル (90 ℃) ヒーター グリセリン (25 ℃) ナフタレンの融点:80度 キャピラリーで生じた結晶が種となり 大きな単結晶に成長

  42. Cross Polarization equalize Zeeman splittings of different species S.R. Hartmann and E.L. Hahn, Phys. Rev. 128 (1962) 2042. 歳差運動と近い周波数を持つ回転磁場中 にスピンを置いた時、スピンが感じる有効 磁場は w/g だけ減ぜられる。 回転磁場の周波数が歳差周波数と離れていれば影響ほぼ無し    磁場の強さ 

  43. Hartmann-Hahn条件 ESR 電子の有効ラーマー周波数が陽子の周波数と一致する時間: 接触時間(contact time) 接触時間が長い方が偏極移行率が 大きくなる。 極小値の値はマイクロ波の強度で決まる。 結晶の内部磁場による広がり: 数 mT    外磁場を掃引ことにより、    全てのsiteで遷移を起こす。 数mT   外磁場の強さ    "スピン移行率" H-H条件 マイクロ波強度[W] ⇔ H1

  44. 偏極度測定:パルス核磁気共鳴法 突然横磁場(RF)をかける   → スピンが倒れ、z軸の周り に回転する。   → xz平面に置かれたコイル に誘導起電力発生 gp: 2.68×108/T/s 角度:RF場の強さ、パルス幅で決まる 横磁場を切った後は、非一様磁場や スピンスピン相互作用のためスピン 軸の回転位相がばらばらになり、 信号強度が減衰する。 Free Induction Decay (FID) FID信号の例

  45. パルスNMR 回転角を使い分ける 信号強度~ sin(q) 減偏極 ~ 1-cos(q) 弱パルス(~5度): 偏極度モニター 90度パルス: 熱偏極信号 パラメータ調整時 180度パルス: 偏極反転 河原 et al.

  46. 光ポンピング用レーザー 吸収スペクトル ペンタセンのエネルギー準位 レーザーの候補 フラッシュランプ励起色素レーザー Pulse width : 800 ns Repetition rate : 50 Hz Average power : 350 mW アルゴン-イオンレーザー (CW) Average power : 500 mW (25 W, 1 kHz, 20 ms) YAG レーザー Pulse width : 10 ns Repetition rate : 30 Hz Average power : 3 W Kyoto group 32% [M. Iinuma et al. Phys. Rev. Lett. 84, (2000) 171.] 色素の寿命 < 100 時間

  47. Analysis procedure 1. Differential cross section → Central term → Volume abs. term 2. Analyzing power data → Spin-orbit term 1.Central and volume absorption term Initial pot.: 6Li potential Fitted data: d.c.s. Phenomenological Optical Model Analysis Preliminary

  48. THIN microwave resonator Copper film loop gap resonator B. T. Ghim et al., Jour. Mag. Reson. A 120 (1996) 72. thin Teflon tube coated with copper film on both sides d = 16 mm z = 20 mm w = 272 mm t = 25 mm n = 15 L=9.7 nH , C = 0.29 pF f = 3.0 GHz

  49. LS potential in neutron-rich nuclei LS potential localized on the nuclear surface 1) should be modified in neutron-rich nuclei where neutron and proton have different surfaces. 2) extended distribution of neutrons may affect the shape of LS potential. direct evidence from p-RI scattering needed ->the polarized proton target + RI beam p+6He Experiment at RIPS, 71 MeV/A

  50. Microscopic Theory K.Amos et al., Adv. Nucl. Phys. 25 Ay ds/dW Target Mass Scattering Angle