Prompt Gamma Activation Analysis and Related … Gamma Activation Analysis and Related Topics Detre...

Prompt Gamma Activation

Analysis and Related Topics

Detre Teschner Department of Inorganic Chemistry,

Fritz-Haber-Institut der Max-Planck-Gesellschaft

1

Modern Methods in Heterogeneous Catalysis Research

PGAA: the basics

2 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner


PGAA: the basics


• Sample is irradiated by neutrons.

• We detect g-photos emitted by the nucleus after neutron capture.

• Energy: qualitative information,

Intensity: quantitative information.

• The signal is independent of the physical and chemical nature of the sample, and only depends on the structure of the nucleus.

PGAA: the basics

Question


Name methods giving you the same type of

information as you can obtain by PGAA?

• ICP-MS, ICP-OES

• XRF

• EDX

• Gravimetry (dissolution and precipitation)

• CHN analysis by combustion

Outline


0) PGAA basics

1) Main properties, neutron capture

2) Setup

3) Related techniques

4) Application examples

5) Catalytic examples

PGAA detection limits


1 18

1

H 2 13 14 15 16 17 2

He

3

Li 4

Be 5

B 6

C 7

N 8

O 9

F 10

Ne

11

Na 12

Mg 3 4 5 6 7 8 9 10 11 12 13

Al 14

Si 15

P 16

S 17

Cl 18

Ar

19

K 20

Ca 21

Sc 22

Ti 23

V 24

Cr 25

Mn 26

Fe 27

Co 28

Ni 29

Cu 30

Zn 31

Ga 32

Ge 33

As 34

Se 35

Br 36

Kr

37

Rb 38

Sr 39

Y 40

Zr 41

Nb 42

Mo 43

Tc 44

Ru 45

Rh 46

Pd 47

Ag 48

Cd 49

In 50

Sn 51

Sb 52

Te 53

I 54

Xe

55

Cs 56

Ba 57

Laa 72

Hf 73

Ta 74

W 75

Re 76

Os 77

Ir 78

Pt 79

Au 80

Hg 81

Tl 82

Pb 83

Bi 84

Po 85

At 86

Rn

87

Fr 88

Ra 89

Acb 104

Rf 105

Db 106

Sg 107

Bk 108

Hs 109

Mt 110

Ds 111

Rg 112

Cn 113

Uut 114

Uuq 115

Uup 116

Uuh

a Lanthanoids 58

Ce 59

Pr 60

Nd 61

Pm 62

Sm 63

Eu 64

Gd 65

Tb 66

Dy 67

Ho 68

Er 69

Tm 70

Yb 71

Lu

b Actinoids 90

Th 91

Pa 92

U 93

Np 94

Pu 95

Am 96

Cm 97

Bk 98

Cf 99

Es 100

Fm 101

Md 102

No 103

Lr

>1 mg/g

100 – 1000 mg/g

10 – 100 mg/g

1 – 10 mg/g

< 1 mg/g

No data

courtesy of L. Szentmiklósi

Properties of PGAA

• nondestructive

• no sample preparation, sample in any form

• independent from chemical environment

• all elements, isotopes: panorama analysis

- light elements (H, B, N, Na, Cl, …)

• extremely different sensitivities

• complicated gamma spectrum


9

Properties of neutron capture

Strasbourg – 05.07.2011.

10-5 1 105 Energy (eV)

103

1

10-3

C.S

. (b

arn

s)

35Cl

Ec = ET - ER

v c = i v Pc

Pc,j i

i

/ = 1

ER =2mAc2

Ec2 E: gamma, transition and recoil

mA: mass of radiating atom

v c: partial gamma production C.S.

i : isotope abundance

Pc: emission probabil ity

v : capture C.S.

Energy

ZAX

ZA+ 1X*

Z+ 1A+ 1X

n

c 1

c 2

c 3

c 4

c 5

c 6

9 Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner

Properties of neutron capture

10

Quantification

Strasbourg – 05.07.2011.

R= nv U

t c = f (Ec)nv c U

t c =M

n (r)

0

3

#V

# NA v c (En)U' (EN,r) f ' (Ec,r)dENdr

Reaction rate: n: number of atoms

U: neutron fluxCount rate of a gamma peak:

f (Ec): counting efficiency

A: net peak area

n2

n1 =A2 / (f 2 v c,2)A1/ (f 1v c,1)

n (r): mass density of the examined element

Quantification


Setup: Budapest Neutron Centre


Question


How can we produce neutrons?

• spallation neutron source (accelerated protons hit Ta, W, Hg target)

• nuclear reactor (induced fission; highly enriched 235U)

• spontaneous fission (252Cf)

• neutron generator (fusion)

• isotopic neutron source (Pu-Be)

Setup: Cold neutron source


FRM II

Spallation: >10 MeV

Fission: 1-10 MeV

Thermalized: ~0.025 eV

Cold: 10-5 – 0.025 eV

Elastic scattering for

thermalizing/cooling n0

Setup: Budapest Neutron Centre

10 MW research reactor with a L-H2 cold neutron source

Curved neutron guides

PGAA facility: Flux (@sample):107-108 cm-2s-1 Compton-suppressed HPGe


Setup: Compton-suppressed HPGe detector

160

30

19

BUDAPEST COMPTON-SUPPRESSED / PAIR-MODE GAMMA SPECTROMETER

8 x BGO

PM

PM

PM

PM

HPGe200

366

BGOcatcher

180

65,5

PM

BGO

HPGe


Setup: Compton suppression


2000 4000 6000 8000 10000 12000 14000 160001

10

100

1k

10k

100k

1M

Co

un

ts/C

ha

nn

el

Channel number

2000 4000 6000 8000 10000

1

10

100

1k

10k

100k

1M

E (keV)

Unsuppressed

Compton-suppressed

Spectrum


Spectrum, library


Z El A MW # E dE s ds% RI Area cps/g

1 H 1 1.01 1 2223.259 0.019 0.3326 0.2 100.00 100.00 64.183

1 H 2 1.01 2 6250.204 0.098 0.000492 5.0 0.15 5.00 0.0286

3 Li 6 6.94 5 477.586 0.050 0.001399 5.9 3.52 10.14 0.1218

3 Li 7 6.94 2 980.559 0.046 0.004365 5.1 10.97 18.74 0.2251

3 Li 7 6.94 3 1051.817 0.048 0.004364 5.1 10.97 17.83 0.2141

3 Li 7 6.94 1 2032.310 0.070 0.0398 5.0 100.00 100.00 1.2007

3 Li 6 6.94 6 6769.633 0.263 0.001354 6.5 3.40 0.84 0.0101

3 Li 6 6.94 4 7246.800 0.275 0.002106 8.4 5.29 1.17 0.014

4 Be 9 9.01 4 853.631 0.011 0.00165 8.9 26.69 100.00 0.0723

4 Be 9 9.01 3 2590.014 0.025 0.00188 8.9 30.41 49.08 0.0355

4 Be 9 9.01 2 3367.484 0.035 0.002924 8.9 47.30 58.96 0.0427

4 Be 9 9.01 5 3443.421 0.036 0.000993 8.9 16.06 19.54 0.0141

4 Be 9 9.01 6 5956.602 0.092 0.000146 9.1 2.36 1.41 0.001

4 Be 9 9.01 1 6809.579 0.099 0.006181 9.0 100.00 48.52 0.0351

5 B 10 10.81 1 477.600 5.000 712.5 0.3 100.00 100.00 39806

6 C 12 12.01 2 1261.708 0.057 0.00123 2.7 45.58 100.00 0.0306

6 C 12 12.01 3 3684.016 0.069 0.001175 3.5 43.53 38.02 0.0116

6 C 12 12.01 1 4945.302 0.066 0.002699 2.9 100.00 60.55 0.0186

7 N 14 14.01 22 583.567 0.031 0.000429 3.3 1.81 6.93 0.0159

7 N 14 14.01 12 1678.244 0.029 0.006254 1.5 26.34 47.15 0.1085

7 N 14 14.01 18 1681.174 0.043 0.001296 2.7 5.46 9.76 0.0225

7 N 14 14.01 21 1853.944 0.052 0.000474 4.5 2.00 3.31 0.0076

7 N 14 14.01 5 1884.853 0.031 0.0145 1.3 61.07 100.00 0.2301

7 N 14 14.01 24 1988.532 0.077 0.000294 5.8 1.24 1.94 0.0045

7 N 14 14.01 15 1999.693 0.032 0.003208 1.7 13.51 21.12 0.0486

7 N 14 14.01 13 2520.446 0.039 0.004246 1.8 17.88 22.98 0.0529

courtesy of L. Szentmiklósi

Question


Count rate of a peak =

(n,g) reaction rates emission probability

detection efficiency

How would you measure the counting efficiency of

the gamma detector?

• Use radioactive materials emitting in a broad enough energy range.

Question



the gamma detector?

PGAA: the basics

Modern Methods in Heterogeneous Catalysis Research; Prompt Gamma Activation Analysis and Related Topics; 09/11/2012; D. Teschner 22

Question


Assume you have a PGAA setup. What

modification you would do to be able to distinguish

between prompt and decay gamma radiation?

• Use chopper of neutron beam.

• Filter detected gammas during chopped beam (open/closed).

Question


What modification you would do to be able to

distinguish between prompt and decay gamma

radiation?

Related techniques


• NAA/NIPS

• PGAI

• Radiography/Tomography-driven PGAI

Most real objects are made of some distinct, by themself homogeneous parts

Visualize and locate the interesting regions first, prompt gamma measurement only where it

is needed for the conclusive result

NAA vs. PGAA


sample

preparation

irradiation

detection

time requirement

detection limit

element detectable

remaining activity

1 g

no, teflon bag

at endstations

on-line

100-5000 peaks, 12 MeV

minutes, hours

>ppm

all except He

max. 1-2 days

10 mg

drying, ampule

at the n0 source

separated in time and space

10-100 peaks, 3 MeV

weeks and more

ppm-ppb

>Na

for months

Multi-element method

No matrix effect

reproducibility

reliable error estimate

nondestructive

Detection after irradiation

PGAA station

NIPS station

Sample

NAA/NIPS


NAA/NIPS: detection


Short sample-detector distance

Increase of efficiency (50-180x)

Detection limit can be better

for certain elements, and

element combinations

For large samples requires

correction for g-self-absorption

Imaging: Why to use neutrons for safeguards?

150 keV X-rays

1.25 MeV gamma-rays

slow neutrons

NO USEFUL INFO

NOT SHARP ENOUGH, BAD CONTRAST

ALL OBJECTS CAN BE RECOGNISED

IRON PIPE


Well-collimated (parallel) neutron beam

Measuring neutron transmission image

Neutron radiography (1 picture)

Neutron tomography (rotation,

many pictures 3D)

Neutron radiography/tomography (NR/NT)


NR/NT with Prompt Gamma Activation Imaging


PGAI-NR/NT

courtesy of Z. Kis and L. Szentmiklósi

n0 direction

A: sample chamber

B: sample stage

C: imaging system

D: gamma detection

Uranium oxide

(U3O8)

Iron

skrew

Aluminum

cylinder

Cu

spheres

…in a Lead

container

Components of the benchmark sample:

PGAI-NR of items in a sealed Pb container


Image correction and object localization


BB-Rot.exe

BB-Rot.exe

BB-Rot.exe

BB-Rot.exe

Prompt-gamma spectra of items


Question


Free your mind Neo!

What would be your envisaged PGAA application?

PGAA applications


PGAA

PGAA applications: industry

Radioisotopic sources + scintillator

• on-line feed analyzers at conveyor belts (Continuous Neutron Analyzer):

cement, coal, mineral analysis

• bore hole logging: oil and mineral extraction industry

Continuous Neutron Analyzer


PGAA in space

Gamma Ray Spectrometer (GRS) aboard the 2001 Mars Odyssey

To learn about the composition of the Martian surface


PGAA in space

Gamma Ray Spectrometer Thermal Emission Imaging System

http://mars.jpl.nasa.gov/odyssey/multimedia/images/

J.L. Bandfield, Nature, 447, 2007, 64


PGAA example: ANCIENT CHARM


http://ancient-charm.neutron-eu.net/ach

non-destructive analysis of cultural heritage samples

PGAA-NR: ANCIENT CHARM


Disc fibula (Hungarian National Museum), 6th century.

NT

PGAI

vid2.avi

PGAA-NR: ANCIENT CHARM


Fe S Au

Cu Al H

Ralf Schulze, Ph.D. thesis, Univ. Köln, 2010

Au

Cu

Au, not Ag

In-situ PGAA

• Adapt PGAA to catalytic research: to provide

fundamental insights of reaction mechanism

• Challenges: • Special geometry, sample environment, shielding

• Decrease background signal

• Reproducibility

• Time dependence?

• Limited beamtime to follow many reaction conditions

• Detection of catalytic performance

• Nuclear data

• Everything should fit


In-situ PGAA

• Remember: PGAA measures elements, never

compounds

• Signal = Gas phase + Surface + Bulk

• Gas phase: constant or negligible

• Bulk: sometimes the main signal, but sometimes no

bulk contribution

• If no bulk: signal → surface coverage

• Often we measure element ratios

• Sometimes information: only small signal changes

• Online reactivity measurement is required.


Example 1: Hydrogenation

Zs. Révay et al., Anal. Chem. 2008, 80, 6066.




1. Experiment in N2 (typically @120°C): to measure

hydrogen content not related to the sample

2. Experiment in H2 (typically near RT)

3. Experiments in hydrogenation (e.g. CxH2x-2+H2;

CxH2x-2+CxH2x+H2)

4. If needed check [H] in N2

+ Correction for gas phase H background

In situ PGAA methodology

1-pentyne conversion and corresponding bulk H/Pd values

Sample: 7 mg Pd black

(200 nm mean p.s.; in SiC)

Temperature: RT

H2: 4 cm3min-1

1-pentyne: 1.6 cm3min-1 in N2

• Always selective hydrogenation

to 1-pentene

• wide variation in H/Pd

No correlation!

D. Teschner et al., Science 2008, 320, 86.



Alkene Alkane:

Alkyne Alkane:

H

C

D. Teschner et al., Science 2008, 320, 86.

D. Teschner et al., Angewandte Chemie 2008, 120, 9414.

Hydrogen content always

high: 0.8-1 H/Pd



Model: alkyne hydrogenation on Pd

(h.p. XPS)




DFT

P. Sautet

D. Teschner et al., J. Phys. Chem. C 2010, 114, 2293.


J. Osswald et al., J. Catal., 2008, 258, 210.

K. Kovnir et al., Surf. Sci., 2009, 603, 1784.

PdGa

Isolated Pd site

• Covalent bonding

• Modified electronic structure

No H dissolution (PGAA)

Excellent selectivity in acetylene

semi-hydrogenation



Example 2: Cl2 production, Deacon

Cl2

NaCl electrolysis

HCl electrolysis

Cl2

H2 +

2 NaCl + 2H2O 2 NaOH + + H2

2 HCl

E

Cat.

E

Cat.

Deacon reaction

2 Cl2 4 HCl + O2 2 H2O + T

Cat.

• In both system RuO2/TiO2 is used as (electro)catalyst.

• RuO2/SnO2/Al2O3: Bayer Deacon patent

• New cheaper Deacon system under development: CeO2


Example 2: Deacon over RuO2

ICIQ: N. Lopez

O2 + 2* ↔ O2**

O2** ↔ 2O*

HCl + O* + * ↔ OH* + Cl*

2Cl* ↔ Cl2 + 2*

2OH* ↔ H2O* +O*

H2O* ↔ H2O + *


D. Teschner et al., J. Catal., 2012, 285, 273.


Neutron collimator

Detector

Sample in oven

Activity determined by titration Correlation between surface adsorbed species and activity

Gas in Gas out



HCl : O2

1:0.25

1:0.5

1:1

1:2

1:4

v(HCl) = 33.3 ml/min v(total) = 167 ml/min

Balance gas: N2

2. Different HCl: O2 ratios at different T’s

1. Pretreatment with HCl at reaction T


3. Additional reference experiments


Experiments Titrated

surface sites Cl/Ru ratio

Cl2@RT

16.6 cm3 min-1 Cl2 +

150.1 cm3 min-1 N2

Cus 0.00898

HCl@543 K

33.3 cm3 min-1 HCl +

133.4 cm3 min-1 N2

Cus + Bridge 0.01797

O2@573 K

33.3 cm3 min-1 O2 +

133.4 cm3 min-1 N2

after HCl@543 K

Bridge 0.00876


D. Teschner et al., Nature Chem., 2012, 4, 739.


• High Cl coverage inhibiting reaction, oxygen activation is rate limiting;

• The higher non-Cl „cus“ coverage, the higher the reaction rate:

1st order rate dependence;

• Effect of T to liberate sites from Cl;

• All supported and unsupported Ru-based samples behave the same way.


D. Teschner et al., Nature Chem., 2012, 4, 739.

Example 2: Deacon

The new catalytic system: CeO2


Example 2: Deacon over CeO2

Both started after an O2-treatment at 450 °C

• T and p(O2) shows very similar dependence

Both, increasing T and p(O2) decreases surface [Cl] and enhances reactivity.

HCl:O2 ratio

surface subsurface/bulk chlorination


R. Farra et al., J. Catal., in press.

http://dx.doi.org/10.1016/j.jcat.2012.09.024


Started after a O2-treatment at 450 °C,

from low to high HCl feed content

*O2 flow: 132.8 ml/min





Started after a O2-treatment at 450 °C,

from low to high Cl2 feed content

• Essentially no effect of Cl2 on the Cl uptake and thus on [Cl].

• BUT, Cl2 inhibition.

*HCl:O2 = 1:9; T = 430 °C

Only minority sites contribute to the reactivity!




Example 2: Deacon over CeO2/ZrO2

• T and p(O2) shows very similar dependence

Both, increasing T and p(O2) decreases surface [Cl] and enhances reactivity.

• No obvious bulk/subsurface chlorination, as found with unsupported CeO2.


M. Moser et al., Appl. Cat. B., submitted

Future in situ applications

• Any heterogeneous catalytic reaction with stoichiometry change

• Hydrogen storage

• Study of Li ion transfer in batteries

• Diffusion and transport processes, proton transfer, temperature induced

segregation

• Time-resolved experiments

• Combination with neutron tomography


Pros & Cons; Possibilities

Bulk characterization (even for H)

Easy adaptation to “in situ”

H/D exchange

Effective detection: H, B, S, Cl, Co

Can give in situ surface coverage information

Time resolution: (min-h) strongly depending on the element

sensitivity

Little sensitivity: C, O, Al, Si, Sn

Little available: only at cold neutron sources


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