1XIXNPDC07092005G.Gorini ANCIENT CHARM A new project for neutron-based 3D imaging with applications to cultural heritage research G. Gorini on behalf

XIXNPDC07092005 G.Gorini 1

ANCIENT CHARMA new project for neutron-based 3D imaging

with applications to cultural heritage research

G. Gorinion behalf of the Ancient Charm collaboration


Outline

ANCIENT CHARM

State of the art

Project objectives and plans


ANCIENT CHARM


ANCIENT CHARM

Analysis by Neutron resonant Capture Imaging and other Emerging Neutron Techniques: new

Cultural Heritage and Archaeological Research Methods

EU funded ADVENTURE project under the New and Emerging Science and Technology (NEST) programme of FP6. Expected start date: 01/2006. Duration: 36 months


Aim of ANCIENT CHARM

“To provide a new, comprehensive neutron-based imaging approach,

which will be applied here for the 3D imaging

of elemental and phase composition

of objects selected as a result of a broad scope archaeological research.”


The ANCIENT CHARM Collaboration

A mix of expertise in neutron instrumentation and archaeology


Available neutron sources

NIPS, Budapest (reactor)PGAA in regular use @ 107 n/cm2sRecently awarded a national grant to renew instrumentation.Expected increase of the neutron flux: factor or 5.

FRM-II, Garching (reactor)NT+PGAA beamline available in 2007 @ 109 n/cm2

GELINA, Geel (150 MeV LINAC, pulsed)NRCA in regular use

ISIS, Chilton (800 MeV p beam, pulsed)ND systems in regular use. Provides highest flux of epithermal neutrons.


PGA beam line at the new research reactor FRM-II, Garching, Germany

Experimental hallNeutron guide hall

The new PGA and cold neutron tomography

station

Neutron flux ~ 1.5 – 6 109 cm-2 s-1

Initial beam size = 5 cm x 11.5 cm

Available in 2007

FRM-II

20 MW reactor

2.03.2004 First time critical


The ISIS Facility


Neutrons and Cultural Heritage Research

A large variety of chemical, physical and microstructural techniques

are employed to characterize objects of cultural significance.

Most of these methods are invasive.

Probes like X-rays and charged particles have limited penetration.

Neutrons penetrate thick layers depending on their energy. Use neutrons for quantitative, non-invasive analysis in bulk.

Neutron-based techniques: a recent development (exception: INAA).


(I)NAA

PGAA

NRCA

T1/2

E

Resonances

Neu

tron

Ene

rgy

Cross section

E

Neutron Capture

XA *1A X+ ++ X1An +


Neutrons-based techniques

Neutron Radiography/Tomography

(widespread)- similar to CT-3D images

Neutron Diffraction

(widespread)-mainly structural analysis-2D

Prompt Gamma Activation Analysis

(a few places)-elemental analysis-0D

Neutron Resonant Capture Analysis

(GELINA)-elemental analysis-0D


STATE OF THE ART


Cold Neutron Tomography


Cold Neutron TomographyCold Neutron Tomography

Radiationsource

Sample

Radiograph

Measurement Analysis : Back-projection


xyz translation rotation table

Detection system

Table

Sample

Beam

Pb + 6LiF

Lead glass

CCD

Mirror

420 m-thick ZnS(Ag) / 6LiF with Al backing

100 m-thick ZnS(Ag) / 6LiF

Conversion screen

Field of view : 2.7 mm x 3.4 mm

Image size : 640 x 512

Effective pixel size = 54 m

Typical exposure time ~ 2 s

Binning 2x2

12 bit CCD SensiCam camera

Pixel size : 6.7 6.7 m2

Number of pixels : 1280 1024

Readout Time : 8 fps


Quality-control of pyrotechnic cutters used in space programs (Ariane)

Application in Aerospace Industry

Computer assisted inspection


PSI:PSI:Kumakhov capillary-based neutron lens:Kumakhov capillary-based neutron lens:entrance height: 50mmentrance height: 50mmentrance width: 20mmentrance width: 20mmlength: 155mmlength: 155mmfocal distance: 150mmfocal distance: 150mmfocus at FWHM: 0.7mmfocus at FWHM: 0.7mmmax. gain on the spot: 16max. gain on the spot: 16

beam dimensionsbeam dimensions

FRM II:FRM II:Polycapillary bending Polycapillary bending and focusing lens:and focusing lens:entrance height: 45mmentrance height: 45mmentrance width: 50mmentrance width: 50mmlength: 190mmlength: 190mmfocal distance: ~95mmfocal distance: ~95mmfocus:focus: ~0.65mm ~0.65mmgain on the spot:~20gain on the spot:~20new spot: 20mm bellow the incoming beamnew spot: 20mm bellow the incoming beam

Neutron focusing lensNeutron focusing lens


Neutron Diffraction


GEM


ENGIN-X


The ENGIN-X transmission detector

100 element transmission detector for residual stress

measurements

Efficiency 85% at 1Å

Pixel array 10 x 10

Pixel size 2 mm x 2 mm on 2.5 mm pitch

Count rate 106 per PMT ie or 64 mm2

GS20 Glass scintillator pixels

Fibre light guides

Hamamatsu 16 channel position sensitive PMTs


Neutron transmission and Bragg edges

Pulsed neutronsource

5000 10000 15000 20000

0

10000

20000

30000

40000

Counts

TOF (sec)

Incidentspectrum

Sample (, A)

5000 10000 15000 20000

0

10000

20000

30000

40000

50000

Counts

TOF (sec)

Transmittedspectrum

( ) ( )⎟⎠

⎞⎜⎝

⎛−= λσλλ xA

II exp)( 0

x

( )( ) ( )λσλλ

nxI

I=⎟⎟

⎠

⎞⎜⎜⎝

⎛−

0

ln

Pixelated detector ( )

( )λλ

0I

ITr =


Strain around a cold expanded hole

Neutrons

Straindirection

x

y

z

Strain values

350-400 ε300-350 ε

400-450 ε450-500 ε

Above 500 ε

250-300 ε200-250 ε150-200 ε100-150 ε100-150 ε50-100 ε

0-50 ε-50 -0 ε

-100 -50 εBelow -100 ε

y (mm)

x (mm)5 10 15

-20

-15

-10

-5

0

0

5

10

15

20


Prompt Gamma Activation Analysis


The NIPS experimental stationThe NIPS experimental station


1E-2

1E-1

1E+0

1E+1

1E+2

1E+3

1E+4

1E+5

H Li B C N F Na Mg A l Si P S Cl K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Rb Sr Y Zr Nb

Sensitivity (cps/g)

Sensitivities at the PGAA-NIPS facility


Pilot experiment for imaging

Neutron beam 1 mm

0.10

1.00

10.00

100.00

0 100 200 300 400

deg

cps

184

278

343

HPGedetector

SiO2

Cu


Neutron ResonantCapture Analysis


NRCA on a prehistoric bronze axe

0

5000

1 104

1.5 104

2 104

2.5 104

1 10 100 1000

AXE5/mar/R1/adc1&2&tot;080403(N/eV)/flux

E(eV)

AXE 5A.U.


Comparison: NRCA vs. PGAA

• PGAA

σc thermal capture cross section

branching

ε detection efficiency a atomic abundance

• NRCA

A,r resonance area

1/Er flux shape

rr,r E

1AaS =

co ak σε=

)eVb(E

g10097.4A

r

n6r, Γ

ΓΓ=


PGAA <----> NRCAPGAA (at Budapest) and NRCA (GELINA)Accuracy for Cu in a bronze artefact about 1%

ko and Sr relative to Cu

-4 -2 0 2 4

-4

-2

0

2

4

Z ≤ 20 21 ≤ Z ≤ 69 70 ≤ Z ≤ 83

( ln S

r( ) / i S

r( ) )Cu

ln( k0(i) / k0(Cu) )

PGAA best for light elements– H, S, P, and K

NRCA best for heavy elements– As, Ag, Sb, Sn, Au

and Pb


0

1 105

2 105

Ag

0

200

400

600

100 200 300 400 500Time of flight ( )s

Au

Pilot NRCA tests on ISIS

Small YAP detectorThreshold: ≈0.6 MeV


PROJECT OBJECTIVESAND PLANS


Work packages

Cultural heritage foundations of neutron-based imaging

From PGAA to PGAI/NT

From NRCA to NRCI/NRT

High neutron flux NRCI/NRT

Model simulations of new hardware

Analysis and simulation tools for NRCI/NRT

Integration of imaging methods

Neutron imaging of cultural heritage samples


From NRCA to NRCI/NRT

Spatially resolved information: combination of

-tight neutron beam collimation,

-multiple positioning of the sample,

-simultaneous measurement of neutron resonances with different strengths.

=> “Neutron Resonant Capture Imaging” combined with

“Neutron Resonance Transmission” (NRCI/NRT):

•Transmission and measurements simultaneously.

•Use YAP crystals for detection.

•Produce images using a few resonances.


400 mm

400 mm

Boron collimator

YAP Crystal detectors

Transmission detectorXYZ- stage

Li (or B) cladding


Transmission vs. measurements

Transmission

• Requires good angular collimation and a large beam.

• Produce 2D images directly (like neutron tomography)

• Need to scan in 1 dimension ()

• Contrast is produced using the depth of the resonant absorption.

• Neutron and background not an issue.

• Has problems with very diluted and very concentrated systems.

measurements

• Requires a small beam.

• Produces cord-integrated 0-D points.

• Need to scan in 3 D (YZ)

• Contrast is produced by the intensity of the peak.

• background is an issue.

• Has problems at low concentrations if background is high.


A 2D NRT detector

• Experience on existing detectors at ISIS

1. Engin-X 2D transmission monitor: 100 pixels, 2x2x2 mm3 for thermal -cold neutrons

2. PEARL NRC detector, single pixel , 7X7X25 mm3

• Issues Pixels must be deep for efficiency. Alignment?

Require large beam with low angular divergence and short S-D distance (similar to radiography). Currently about 10 mrad.

A 2D NRT detector with 1-2mm pixel resolution should be feasible


Conclusions:

in 3 years.

Meanwhile...


Documents

1XIXNPDC07092005G.Gorini ANCIENT CHARM A new project for neutron-based 3D imaging with applications to cultural heritage research G. Gorini on behalf