1

A. Kitamura, H. Iwai, R. Nishio, R. Satoh,A. Taniike and Y. Furuyama

Department of Environmental Energy Science,Graduate School of Science and Technology, Kobe University

5-1-1 Fukaeminami-machi, Higashinada-ku, Kobe 658-0022, JapanE-mail : kitamura@maritime.kobe-u.ac.jp

In situ Accelerator-Based Characterization of CaO/Sr/Pd Samples

under Deuterium Permeation

2

In the present work;● The objective is

・ to investigate the dependence of the transformation rate on material, D flux, flow direction, temperature, etc.・ to find the optimum sample structure.・ from a point of view of enhancing the transformation yield.

● Diagnostic methods;in situ and simultaneous measurements of compositional change during D permeation by accelerator analyses;

PIXE (Particle induced X-ray emission analysis)RBS (Rutherford backscattering spectroscopy)NRA (Nuclear reaction analysis)ERDA (Elastic recoil detection analysis)

as well as conventional XPS and Desorption measurements.

・ Deuterium permeation through Pd/(CaO+Pd)/Pd sample induced nuclear transmutations; 133Cs→141Pr, 88Sr→96Mo, 138Ba→150Sm and 137Ba→149Sm.

1. Y. Iwamura, M. Sakano and T. Itoh; Jpn. J. Appl. Phys. 41 (2002) 4642-4650.2. Y. Iwamura, T. Itoh, M. Sakano, S. Kuribayashi, Y. Terada, T. Ishikawa and J. Kasagi; Proc. ICCF11, 2004, Marseilles, France.

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Experimental procedure; in the present work, X =Sr, Y=CaO

(1) Depositing X on Pd(A; the 1st stage); electroplating,

(B; the 2nd stage); ion-beam sputtering deposition

(2) Forming a layer of Y on X/Pd(RF sputtering deposition)

(3) Permeation of D through Y/X/Pdcausing nuclear transmutation XX’

(1D) XPS for areal density of X

(2D) XPS for areal densities of Y and X

(3D) In situ and simultaneous

PIXE, RBS and NRA for areal densities of X, X’, (Y) and D distribution

(done only for the sample B)

(4D) XPS for areal densities of Y, X and X’

(4) Desorption of D2

4

MCA

Pressure gauge

0.8-2.5 MeV 3He++ for NRA3 MeV p for PIXE

MCA

Amp.

Preamp.

MCA

Amp.

Preamp.

Amp.

1 atm D2 gas

Probe beam ions from PELLETRON 5SDH2

Recorder

A

D2

Preamp.

X-Ray Detector

RBS-SSD

SSD for NRA with4-m Mylar filter

CaO/Sr/Pd

5

D2 gasCaO/Sr/Pd vacuum

10nm / 0.1mm

Deuterium permeates through the CaO(10nm)/Sr/Pd samplefrom the rear surface out to vacuum.

CaO/Pd Layers

D2 gas

Bulk PdThin Pd Film

Vacuum

Nuclear transmutation

Flow direction

CaO/Pd Layers

D2 gas

Bulk PdThin Pd Film

Vacuum

Nuclear transmutation

Flow directionFlow direction

cf.; the sample used by Iwamura et al.

6

2 4 6 8 10

1

2

3

0Time [s]

Ion

flux

[10

14 c

m-2

s-1]

A

Recorder

Pt

Pd

Sr atoms are deposited on one side of a 0.1-mm-thick Pd foil as contamination with an areal density of the order of 1014 cm-2.

10 mM Sr(NO3)2/D2O

1 V

(1) Depositing Sr on Pd ; (A) electrochemical method

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Recorder

A

Ar+ ion beam

Sr 45°

Pd substrateSr target

(1) Depositing Sr on Pd ; (B) ion beam sputtering

Energy; 5 keVCurrent; ~2 A

Sr deposition rate; 1E13 atoms/cm2/s

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RF sputtering condition

• Cathode (sputter target); CaO

• Anode (sample); Sr/Pd

• Ar pressure; 0.1 Torr

• RF power; 100 W

• Plasma exposure time; 5 - 30 min.

• Sample temperature; 450 K

• CaO deposition rate; 0.1 - 0.5 nm/min

(2) Forming a layer of CaO on Sr/Pd ; RF sputtering deposition

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300 320 340 360 380 4000

0.2

0.4

0.6

0.8

1

Binding energy [eV]

Inte

nsit

y [1

05 cps

] 20 s 120 s 260 s

Ca-2p Etching timePd-3d

Change in the sample structure is reflected in XPS spectra after repetitive etching of the CaO/Sr/Pd surface.

(2D) XPS characterization after forming the layer of CaO on Sr/Pd

10

x

tt

ΔΩdΩ

dnSY

0 Ca-CaO

CaCap

23Ca_2p

dexp

0 Pd-PdPd-CaO

PdPdp

253d-Pd

dexpexp ttx

ΔΩdΩ

dnSY

.exp1exp

253d-PdCa-CaOCaCa

232p-CaPd-PdPdPd

Ca-CaOPdCaO Yn

Ynxx

- The CaO layer thickness x is calculated from the intensity ratio of these peaks, YCa-2p/YPd-3d;

where

,

.

11

50 100 150 200 250 300

2

4

6

8

0

Thi

ckne

ss o

f C

aO la

yer

[nm

]

Etching time [s]

Sample#1Sample#2Sample#3Sample#4

The thickness of the CaO layer has been calculated from the XPS yield of the Pd-3d peak relative to that of Ca-2p

to be about 10 nm for the sample #4.

(2D) XPS characterization after forming the layer of CaO on Sr/Pd

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D flux (flow rate) 2.71015 cm-2s-1

(=0.02 sccm)

PdD0.65

D permeation toward a vacuum side

0 100 200 300 400 500 6000

5

10

Time [h]Num

ber

of D

ato

ms

abso

rbed

[1021

]

0 100 200 300 400 500 6000

5

10

Time [h]Num

ber

of D

ato

ms

abso

rbed

[1021

]

(3) Permeation of D through CaO/Sr/Pd (the sample B)

During D permeation, pressure in the reservoir has been monitored to calculate the number of absorbed/transmitted D atoms.

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(3D) NRA during permeation of D through CaO/Sr/Pd (the sample B)

The NRA revealed the almost uniform composition of PdD0.65 over the depth region of 0-1.8 m.

0 0.5 1 1.50

2

4

6

8

10

Depth [m]D

ensi

ty [

1022

cm

-3]

PdD0.86

PdD0.65

0 1 2 3 4 5100

101

102

103

104

105

Energy [MeV]

Yie

ld [

coun

ts/8

keV

] Pd

D(3He, 4He)p

Pd(3He,3He)

NRA using the D(3He, 4He)p reaction

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(3D) PIXE analysis during permeation of D through CaO/Sr/Pd (the sample B)

The PIXE spectra revealed existence of a variety of impurities.The Mo-K/ seems to be interfered by unidentified broad peaks.

Fe-K

Pt-L

Sr-K

Mo-K

Pd-K

0 5 10 15 20 25 30 35 40100

101

102

103

104

105

106

107

Energy [keV]

Yie

ld [

coun

ts/4

3 eV

] before 345 h after 586 h after

initiation of D permeation?

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(3D) PIXE analysis during permeation of D through CaO/Sr/Pd (the sample B)

Variation of the areal density of Sr during permeation of D for 590 hours. Results of ex-situ XPS are also plotted for comparison.

0 100 200 300 400 500 6000

10

20

30

40

Time [h]

Are

al d

ensi

ty o

f Sr

[10

14 c

m-2

]

PIXE XPS

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0 50 100 150 2001015

1016

1017

1018

1019

1020

1021

Time [h]

No.

of

D a

tom

s re

leas

ed

(4) Desorption of D2

Outgassing of the sample after finishing D permeation was necessary for introduction into the XPS chamber. Total amount of d

esorbed D atoms measured with QMS indicates D/Pd0.3.

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0

2

220a 2

)12(exp

)12(

81)(

s

Dta

s

saSntN

s 1061967.0 1

2

21 D

at

- The process of deuterium charging is described by a 1-dimensional solution of the diffusion equation for the sample with a thickness and area of a and S, respectively. - One side of the sample is assumed to be opaque for deuterium, while the other facing to hydrogen gas to give a boundary condition for the deuterium density; n(a) = n0. - The number of deuterium atoms absorbed in the sample, Na(t), is given as a function of time by

- A characteristic time t1/2 for the number of deuterium atoms absorbed to reach a half of the saturation value, i.e., Na(t1/2)/aS = Na()/2aS = 2.91022 cm-3, is therefore given by

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120 140 160 180 200 220 2403

4

5

6

7

5

6

7

8

Binding energy [eV]

Inte

nsit

y [1

03 cps

] Intensity [10 3 cps]

Sr-3d Mo-3dS-2p S-2s

XPS spectra before and after D permeation. Increase in Mo-3d peaks in exchange for decrease in Sr-3d peaks is observed.

(4D) XPS characterization of the sample A after D2 Desorption

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XPS analysis implies nuclear transmutation near the CaO/Pd boundary: Sr atoms with areal density of 1.31014 cm-2 appear to

be transformed to Mo atoms of 6.61013 cm-2 by D permeation.

-4 -3 -2 -1 0 1 20

0.5

1

1.5

Distance from the CaO/Pd interface [nm]

Den

sity

[1014

cm

-2n

m-1

] Sr Mo Sr Mo

before Dpermeation

after Dpermeation

Pd layerCaO layer

-4 -3 -2 -1 0 1 20

0.5

1

1.5

Distance from the CaO/Pd interface [nm]

Den

sity

[1014

cm

-2n

m-1

] Sr Mo Sr Mo

before Dpermeation

after Dpermeation

Pd layerCaO layer

(4D) XPS characterization of the sample A after D2 Desorption

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Sr-3d3/2Sr-3d5/2

226 228 230 232 2345

5.2

5.4

5.6

Binding energy [eV]In

tens

ity

[103 c

ps]

Mo-3d3/2Mo-3d5/2

130 132 134 136 138 1400

5

10

15

20

25

Binding energy [eV]

Inte

nsit

y [1

03 cps

] Before D permeation

After D permeation

(4D) XPS characterization of the sample B after D2 Desorption

An order of magnitude increase in areal density of Sr (2 monolayers) was realized by RF sputtering method. However, nuclear transmu

tation was not recognized for this sample.

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Sample A: Transmutation efficiency was 50%.Sample B: Decrease in areal density of Sr was not followed by

consistent increase in other elements observable.

Summary of changes in areal densities

PIXE XPS

Sr Mo Others Sr Mo

A (electroplating) ----- ----- ----- 1.3 +0.66

B (I. B. sputtering) 2.5 <<+1.9 <<+1 15 <<+0.11

areal densities in 1E14 cm-2

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(1) Implication of nuclear transmutation Sr Mo has been obtained in a system [vacuum/CaO/Sr/PdDx/D2], which is a little simpler than that used by Iwamura et al.

Summary

(3) Extended analytical methods have been prepared; in situ and simultaneous PIXE, RBS and NRA/ERDA for areal densities of transmutation elements and deuterium distribution.

(4) Increase in the areal density of Sr to 3.31015 cm-2 by using ion beam sputtering method resulted in negligible transmutation yield.

(2) The diagnostic method used to identify the elements was conventional XPS, giving the areal densities of 1.3 1014 cm-2 (Sr) and 6.61013 cm-2 (Mo).

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Summary

-Dependence on the density of the atoms to be transmuted,

(5) Further experimental work is necessary to confirm the phenomena;

the areal density of the atoms,the flux (flow rate) of D,the sample structure, .

-Effect of surface contamination.