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Development of a Polarized 3 He Target at RCNP

Development of a Polarized 3 He Target at RCNP. Youhei Shimizu RCNP, Osaka University. Collaborators. RCNP, Osaka University : Y. Shimizu , K. Hatanaka, Y. Sakemi, A. Tamii, H.P. Yoshida, M. Uchida, Y. Shimbara, K. Fujita, Y. Tameshige, H. Matsubara CNS, University of Tokyo :

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Development of a Polarized 3 He Target at RCNP

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  1. Development of a Polarized 3He Target at RCNP Youhei Shimizu RCNP, Osaka University

  2. Collaborators RCNP, Osaka University : Y. Shimizu, K. Hatanaka, Y. Sakemi, A. Tamii, H.P. Yoshida, M. Uchida, Y. Shimbara, K. Fujita, Y. Tameshige, H. Matsubara CNS, University of Tokyo : T. Uesaka, T. Wakui, T. Kawabata, K. Suda, Y. Sasamoto Saitama University : K. Itoh Kyushu University: K. Sagara, T. Wakasa, T. Kudoh, M. Tomiyama, H. Ohira Osaka University: T. Adachi Tohoku University: H. Okamura RIKEN: H. Ueno Bogoloyubov Institute for Theoretical Physics : A.P. Kobushkin

  3. Contents • Introduction 1.1.3He Target 1.2. Elastic Backward Scattering • Polarized 3He Target at RCNP 2.1. Target apparatuses 2.2. Measurement of 3He density • Measurement of 3He Polarization 3.1. AFP-NMR Method 3.2.3He(p,p+)4He Reaction 3.3. Absolute 3He Polarization • Summary

  4. 3He Target • The relative strength of target-related spin dependent effects is larger than for any other dense nuclei. Elastic pion scattering p+ + 13C Tp=132MeV p+ + 15N Tp=164MeV p+ + 3He Tp=100MeV B. Larson et al., PRL 67, 3356 (1991). Yi-Fen Yen et al., PRL 66, 1959 (1991). R. Tacik et al., PRL 63, 1784 (1989). • The precise 3He ground state wave function is obtained by Faddeev calculation. • High density and the high degree of polarization.

  5. p+3He Elastic Scattering • The cross section at back angles show a rising pattern which is energy dependent. • In order to reproduce the ds/dW at backward angles, deuteron exchange effects were taken into account. • There are discrepancies between the experimental data and theoretical predictions including exchange effects at back angles. M.S. Abdelmonem and H.S. Sherif, PRC 36, 1900 (1987). Elastic Backward Scattering (EBS) • Structure of the light nuclei (d, 3He, a) at short distances between the constituent nucleons. • High momentum components of the target wave function. • Systematic study of the reaction mechanisms including exchange effects. • The spin observables can give an additional information. We developed a thick and highly polarized 3He target at RCNP.

  6. Polarized 3He Target • Meta-stability exchange method • Spin-exchange method • 23S1 meta-stable 3He atoms are directly polarized by an optical pumping method (l = 1.084 mm). • The polarization of the meta-stable state is transferred to the ground state via the meta-stability exchange reaction. • Rb vapor is polarized by optical pumping with a circularly polarized light (l = 794.7 nm). • The Rb electron polarization is transferred to the 3He nucleus via the spin-exchange collision. Easily application for high density target

  7. Spin-Exchange Method • Rb vapor is polarized by optical pumping with a circularly polarized light (l = 794.7 nm). • The Rb electron polarization is transferred to the 3He nucleus via the spin-exchange collision.

  8. The Schematic view of the Polarized 3He Target COHERENT FAP-79-30C-800LB Diode Laser Power : 60 W Wavelength : 795 nm

  9. Temperature Dependence of the Wavelength • The center of wavelength is dependent on temperature and current. • It was necessary to lock onto the Rb D1 resonance line. • In order to adjust the wavelength to the Rb D1 resonance line, the laser diode is cooled down to 22.3 oC by using PID (Proportional, Integral, and Differential) feedback control. PID Feedback Control System • Peltier elements • Temperature sensors (LM335) • CC power supplier for peltier elements We have succeeded to stabilize the temperature within 0.1 oC.

  10. Target Cell • The cell had a thin window of 100 mm to reduced background from glass. • A cell is double cell structure and consists of two parts, a target cell and a pumping cell, connected by a transfer tube. • Each cell volume was measured by Archimedes principle. • The borosilicate glass, Corning7056, was used. Type1 Type2 1/G : 15 hours VT : 224 cm3 VP : 286 cm3 1/G : 20 hours VT : 227 cm3 VP : 120 cm3

  11. The Measurement of 3He Density • In order to obtain the cross section and the absolute 3He polarization, it is necessary to know the density of the 3He in the cells and its error. • The 3He density of our cells was measured by using the broadening of the Rb resonance absorption lines by 3He density in same manner as Romalis et al., PRA 56, 4569 (1997). Setup of an optical measurement Results The absorption width and 3He densities at thermal equilibrium.

  12. Measurement of the 3He Polarization • AFP (Adiabatic Fast Passage) - NMR • 3He(p,p+)4He • 3He polarization was monitored by AFP-NMP method. • NMR signal is proportional to the degree of polarization. • The 3He polarization saturates after 1 day pumping • AFP-NMR method only gives relative values. • Absolute polarization must be calibrated. Typical NMR signal In the case 1/2+ + 1/2+ 0+ + 0-, one can show from the parity conservation that the spin correlation parameter Cyy takes the constant value of 1. Time development of NMR signal

  13. Experimental Setup • Measurement • 3He(p,p+)4He reaction at 0 degree • Observables • Differential Cross section ds/dW • 3He Polarization • Polarized proton beam • Energy: 400, 300 MeV • Polarization: 70 % • Intensity: 10 – 40 nA • Polarized 3He gas target • Spin exchange type • Polarization: 12 % in average • Both cells (Type1, Type2) Grand Raiden D1 Faraday Cup

  14. Differential Cross Section of 3He(p,p+)4He • 3He(p,p+)4He peak at 400 and 300 MeV. • The backgrounds were subtracted by fiiting. • Comparison with previous results. • Our results are consistent with them. K.M. Furutani et al., PRC 50, 1561(1994).

  15. Relation to AFP-NMR Amp. Absolute 3He Polarization Results • Ep = 400 MeV Cell : Type1 PHe = (6.33±0.19)×10-4×VNMR PHe = (2.51±0.09)×10-3×VNMR/[He] • Ep = 300 MeV Cell : Type2 PHe = (5.42±0.32)×10-4×VNMR PHe = (2.46±0.15)×10-3×VNMR/[He] Relation between Amp. and Pol.

  16. p+3He Elastic Backward Scattering (EBS) • We measured the differential cross section and spin correlation parameter Cyy of p+3He EBS at 400, 300, 200 MeV. • ds/dW are consistent with previous results. • Cyy are measured for the first time. Calculated by A.P. Kobushkin

  17. Summary • Polarized 3He Target at RCNP • We have succeeded to stabilize the temperature within 0.1 oC by using PID feedback system. • We measured the precise 3He density. • 3He polarization was calibrated by 3He(p,p+)4He reaction. Maximum : 19 % Average : 12 % 3He polarization was smaller than other institutions. • Problems • Rb polarization is small. (Laser power is not enough.) • Relaxation time is short because of magnetic field inhomogeneity at experimental hall (1/G : 15 hours  4 hours).

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