dnp for polarizing liquid 3 he

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DNP for polarizing liquid 3 He. Hideaki Uematsu Department of Physics For Yamagata University PT group. Yamagata PT group(2006). Background of the study. Polarized 3 He targets have been used in various scattering experiments > in 3 He only neutron is polarized - PowerPoint PPT Presentation

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  • DNP for polarizing liquid 3He Hideaki UematsuDepartment of PhysicsFor Yamagata UniversityPT group

  • Yamagata PT group(2006)

  • Background of the studyPolarized 3He targets have been used in various scattering experiments > in 3He only neutron is polarized > a good target for the study of neutron characteristics > studied only in gas targetsAdvantages of polarizing liquid 3He >Density gas:liquid=1:662 >Its fluidity may allow to make a polarized target with circulating polarized liquid 3He >Could be applied in many other fields(e.g. medical use, material science, chemistry, etc.)

  • How to polarize 3He in liquid formBrute force method >Polarized liquid is obtained by quickly melting polarized solid >55% polarization obtained in solid at 6.6T, 6mK, and 30bar, G.Bonfait et al. Phys.Rev.Lett. 53(1984)1092 >However, its difficult to make 3He solidDynamic Nuclear Polarization (DNP) >spin-spin coupling between electron and nucleus >Transferring polarization of electrons to neighboring nuclei >able to obtain both positive and negative polarization

  • US group applied DNP for polarizing liquid 3HeUsed powdered sucrose charcoalPolarization transfer process:electron 1H 3HeObtained positive enhancements1.18 times of TE signal amplitude at T=1.8K,B=182GMeasured relaxation time T1 was 1.02secL.W.Engel et al 1985DNP

  • French group applied DNP for polarizing liquid 3HeUsed fluorocarbon beads containing electronic paramagnetic centersPolarization transfer process: electron 19F3HeObtained enhancements

    Positive: twice of TE signal at T=250mK, B=300GNegative: not mentionedA.Schuhl et al 1985DNP3He19FHTE3He

  • Our New DNP method for polarizing liquid 3HeDirect coupling of a unpaired electron and 3He>using spin-spin interaction of electron and nucleusUsing unpaired electrons in a free radical Embedding the free radical into a porous material Filling the porous material with liquid 3HeIrradiating a microwave Free radical TEMPOPorous material Zeolite

  • Zeolite and TEMPONaY type zeolite (n=51)Super Cage Max dia.: 13Window dia.: 7.44.7x1019 super cages/g3He(dia.:3) 80 3He can get in one super cage TEMPO(2,2,6,6-tetramenthyl-piperidinyl-1-oxyle)Melting point: 36 CBoiling point: 67 CMolecule size: ~7sodalite cagedouble T6-ringZeolite(NanAlnSi(192-n)O384240H2O(n=48~76) TEMPOESR signal of TEMPO in zeolitesuper cage

  • Embedding TEMPO to ZeolitePreparation : Desiccate zeolite at 500 C for 8 hoursDissolve TEMPO in n-pentane Add zeolite to n-pentane solution Stir n-pentane solution for 8 hours in a sealed vesselEvaporate n-pentane in a vacuum container

  • Embedding TEMPO to ZeolitePreparation : Desiccate zeolite at 500 C for 8 hoursDissolve TEMPO in n-pentane Add zeolite to n-pentane solution Stir n-pentane solution for 8 hours in a sealed vesselEvaporate n-pentane in a vacuum containerTEMPOzeolite

  • Embedding TEMPO to ZeolitePreparation : Desiccate zeolite at 500 C for 8 hoursDissolve TEMPO in n-pentane Add zeolite to n-pentane solution Stir n-pentane solution for 8 hours in a sealed vesselEvaporate n-pentane in a vacuum container

  • Embedding TEMPO to ZeolitePreparation : Desiccate zeolite at 500 C for 8 hoursDissolve TEMPO in n-pentane Add zeolite to n-pentane solution Stir n-pentane solution for 8 hours in a sealed vesselEvaporate n-pentane in a vacuum container

  • Experimental setupExperimental cell made of a PET tube and a VCR gas connector Volume : 2.5ccExperimental cell filled with zeolite tightly and quickly

  • Thermal equilibrium signal of 3HeTE signal of liquid 3HeT=1.42K ,B2.5T e- spin density :1.31019spins/cc T=1.47K, B2.5TLow concentration of TEMPO e- spin density :4.51018spins/cc T=1.54K, B2.5THigh concentration of TEMPOBulk 3He (without zeolite)Symmetric signal when in zeoite Narrower width for low spin density Bulk 3He signal shows asymmetric shape

  • TE signals fitted with Lorentzian TE signal of liquid 3HeT=1.42K ,B2.5T spin density :1.31019spins/cc T=1.47K, B2.5T spin density :4.51018spins/cc T=1.54K, B2.5TLow concentrationHigh concentrationExtent: 44.4ppmBulk 3He(without zeolite) Red line shows the LorentzianCenter frequency of 3He: 81.09MHz (in 2.5T)Extent: 202ppmExtent: 202ppm

  • Relaxation time of liquid 3Hetime development of NMR signal of liquid 3He inside zeoliteT=1.44K, B=2.5T, spin density: 1.31019 spin/cc

    Spin relaxation time:T1=330sec3He in zeolite with TEMPO

  • Positive enhancement by DNPTE signal T=1.48K, B2.5T observed positive enhancement S/STE =2.34spin density=4.51018 (low concentration)

  • Negative enhancement by DNPTE signal T=1.53K, B2.5Tobserved negative enhancementS/STE =-1.59spin density=4.51018

  • Micro wave frequency dependence fc: ESR center frequency of TEMPO(=70.22GHz)spin density:1.31019, B2.5Tat 2.5T expected ESR line width for TEMPO is 340MHzObserved line width wasnarrower than expected

  • SummaryWe obtained the thermal equilibrium signal of liquid 3He in zeolite. A narrow signal was observed with low concentration of TEMPO.We measured relaxation time of 3He in zeolite (It is a few minutes at 2.5T)We obtained polarization enhancements for liquid 3He in zeolite by DNP.The enhancements were larger than ever before (obtained by DNP).They may be improved by tuning the conditions.

  • Thank you for listening

  • Zeolite and its characterMineral which has a micro-porous structure, high hydrophobicity, thermostability and mostly used as a catalyst, ion exchanger, absorber (NanAlnSi(192-n)O384240H2O(n=48~76)Used (HSZ-300serise)TOSOH corporationCation type: NaSiO2/Al2O3(mol/mol): 5.5Na2O(wt%): 12.5U.C.C. by ASTM :24.63NH3-TPD(mmol/g): -Surface Area(BET, m2/g): 700Crystal Size(m): 0.3Mean Particle Size(m): 6

  • Decrease of TEMPO in ZeoliteSpin density :7.51018spin/ccRoom temperature

  • Density of liquid 3He in 1g zeolite

    23.1mg