dnp for polarizing liquid 3 he dnp for polarizing liquid 3 he hideaki uematsu department of...

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

TRANSCRIPT

DNP for polarizing liquid 3He

Hideaki Uematsu

Department of Physics

For Yamagata University

PT group

Yamagata PT group(2006)

Background of the study

Polarized 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 targets

Advantages 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 form

Brute 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 solid

Dynamic 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 3He

Used powdered sucrose charcoalPolarization transfer process:

electron 1H 3He

Obtained positive enhancements1.18 times of TE signal amplitude at T=1.8K,B=182GMeasured relaxation time T1 was 1.02secL.W.Engel et al 1985

DNP

French group applied DNP for polarizing liquid 3He

Used fluorocarbon beads containing electronic paramagnetic centersPolarization transfer process: electron 19F3HeObtained enhancements

Positive: twice of TE signal at T=250mK, B=300G

Negative: not mentioned

A.Schuhl et al 1985

DNP

3He

19F

H

TE

3He

Our New DNP method for polarizing liquid 3He

Direct coupling of a unpaired electron and 3He

>using spin-spin interaction of electron and nucleus

Using 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 TEMPO

Porous material Zeolite

Zeolite and TEMPO

NaY type zeolite (n=51)

Super Cage

Max dia.: 13

Window dia.: 7.4

4.7x1019 super cages/g

3He(dia.:3) 80 3He can get in one super cage

TEMPO(2,2,6,6-tetramenthyl-piperidinyl-1-oxyle)

Melting point: 36 C

Boiling point: 67 C

Molecule size: ~7

sodalite cage

double T6-ring

Zeolite(NanAlnSi(192-n)O384240H2O(n=48~76)

TEMPO

ESR signal of TEMPO in zeolite

super cage

H

H

CH3

CH3

H3C

H3C

H

H

H

H

N

O

7

7.4

Embedding TEMPO to Zeolite

Preparation : Desiccate zeolite at 500 C for 8 hours

Dissolve TEMPO in n-pentane

Add zeolite to n-pentane solution

Stir n-pentane solution for 8 hours in a sealed vessel

Evaporate n-pentane in a vacuum container

500 C

Zeolite

Embedding TEMPO to Zeolite

Preparation : Desiccate zeolite at 500 C for 8 hours

Dissolve TEMPO in n-pentane

Add zeolite to n-pentane solution

Stir n-pentane solution for 8 hours in a sealed vessel

Evaporate n-pentane in a vacuum container

TEMPO

zeolite

n-pentane

Embedding TEMPO to Zeolite

Preparation : Desiccate zeolite at 500 C for 8 hours

Dissolve TEMPO in n-pentane

Add zeolite to n-pentane solution

Stir n-pentane solution for 8 hours in a sealed vessel

Evaporate n-pentane in a vacuum container

Embedding TEMPO to Zeolite

Preparation : Desiccate zeolite at 500 C for 8 hours

Dissolve TEMPO in n-pentane

Add zeolite to n-pentane solution

Stir n-pentane solution for 8 hours in a sealed vessel

Evaporate n-pentane in a vacuum container

R

Experimental setup

Experimental cell made of a PET tube and a VCR gas connector

Volume : 2.5cc

Experimental cell filled with zeolite tightly and quickly

Experimental cell

Image of experimental chamber

Thermal equilibrium signal of 3He

TE signal of liquid 3He

T=1.42K ,B2.5T

e- spin density :1.31019spins/cc

T=1.47K, B2.5T

Low concentration of TEMPO

e- spin density :4.51018spins/cc

T=1.54K, B2.5T

High concentration of TEMPO

Bulk 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 3He

T=1.42K ,B2.5T

spin density :1.31019spins/cc

T=1.47K, B2.5T

spin density :4.51018spins/cc

T=1.54K, B2.5T

Low concentration

High concentration

Extent: 44.4ppm

Bulk 3He(without zeolite)

Red line shows the Lorentzian

Center frequency of 3He: 81.09MHz (in 2.5T)

Extent: 202ppm

Extent: 202ppm

Relaxation time of liquid 3He

time development of NMR signal of liquid 3He inside zeolite

T=1.44K, B=2.5T, spin density: 1.31019 spin/cc

Spin relaxation time:T1=330sec

3He in zeolite

with TEMPO

Fitting function

S: area of the NMR signal

Positive enhancement by DNP

TE signal

T=1.48K, B2.5T

observed positive enhancement

S/STE =2.34

spin density=4.51018 (low concentration)

max polarized signal

B2.5T

Negative enhancement by DNP

TE signal

T=1.53K, B2.5T

observed negative enhancement

S/STE =-1.59

spin density=4.51018

max polarized signal

B2.5T

Micro wave frequency dependence

fc: ESR center frequency

of TEMPO(=70.22GHz)

spin density:1.31019, B2.5T

at 2.5T expected ESR line

width for TEMPO is 340MHz

Observed line width was

narrower than expected

Summary

We 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 character

Mineral 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 Zeolite

Spin density :7.51018spin/cc

Room temperature

Density of liquid 3He

in 1g zeolite

23.1mg

n-pentane

C5H12 melting point: -131C boiling point: 36.07C

0.13%

1

23

3

1

27

10

38

.

1

13

.

2

10

05

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5

-

-

-

-

=

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=

=

K

J

k

T

J

kT

B

P

B

N

He

TE

N

m

m

m

m

cc

spin

/

10

5

.

4

18

(

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d

T

b

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a

t

S

+

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=

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exp

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