Prompt Gamma Activation Analysis in High-Flux Cold

Neutron BeamsZsolt Révay, Petra Kudejova, Lea Canella, Stefan Söllradl

TUM Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II)

(Heinz Maier-Leibniz Zentrum)

FRM IIMaier-Leibnitz Zentrum

Heinz Maier-Leibnitz

• Neutron beam techniques– SANS– PGAA

• H.M-L. J. Nucl. Energy, 17 (1963) 217• Henkelmann-Born: first PGAA at FRM (1969)

• ”The reduction in background by use of high-quality beam is more important for analytical purposes than is an increase in the capture rate”

• in Neutron Capture Gamma-Ray Spectroscopy (Ed. N. Ryde), IAEA, Vienna, 1969, p.105

What does PGAA measure?• Average composition of irradiated volume

– Matrix composition– Light elements in general

• H analysis in broad dynamic range– Water solution– H as trace element

– Certain trace elements: • B, Cd, Hf, Gd, Eu, Sm

– High-cross-sec elements in low-cross-sec matrix

• H in D, Cl in F, Ag in Cu, Cd in Zn, Hf in Zr, Gd/Sm in Y/La/Ce, etc.

H He

Li Be B C N O F Ne

Na Mg Al Si P S Cl Ar

K Ca Ga Ge As Se Br KrMn Fe Co Ni Cu ZnSc Ti V Cr

Rb Sr In Sn Sb Te I XeTc Ru Rh Pd Ag CdY Zr Nb Mo

Cs Ba Tl Pb Bi Po At RnRe Os Ir Pt Au Hg57-71 Hf Ta W

Ho Er Tm Yb LuPm Sm Eu Gd Tb DyCe Pr Nd

Es Fm Md No LrNp Pu Am Cm Bk CfTh Pa U

Fr Ra Ac

Lanthanides La

Actinides

H He

Li Be B C N O F Ne

Na Mg Al Si P S Cl Ar

K Ca Ga Ge As Se Br KrMn Fe Co Ni Cu ZnSc Ti V Cr

Rb Sr In Sn Sb Te I XeTc Ru Rh Pd Ag CdY Zr Nb Mo

Cs Ba Tl Pb Bi Po At RnRe Os Ir Pt Au Hg57-71 Hf Ta W

Ho Er Tm Yb LuPm Sm Eu Gd Tb DyCe Pr Nd

Es Fm Md No LrNp Pu Am Cm Bk CfTh Pa U

Fr Ra Ac

Lanthanides La

Actinides

0.001 – 0.1 μg

10 – 1000 μg> 1000 μg

1 – 100 μg0.1 – 10 μg

0.01 – 1 μg

no data

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PGAA Elements

H He

Li Be B C N O F Ne

Na Mg Al Si P S Cl Ar

K Ca Ga Ge As Se Br KrMn Fe Co Ni Cu ZnSc Ti V Cr

Rb Sr In Sn Sb Te I XeTc Ru Rh Pd Ag CdY Zr Nb Mo

Cs Ba Tl Pb Bi Po At RnRe Os Ir Pt Au Hg57-71 Hf Ta W

Ho Er Tm Yb LuPm Sm Eu Gd Tb DyCe Pr Nd

Es Fm Md No LrNp Pu Am Cm Bk CfTh Pa U

Fr Ra Ac

Lanthanides La

Actinides

H He

Li Be B C N O F Ne

Na Mg Al Si P S Cl Ar

K Ca Ga Ge As Se Br KrMn Fe Co Ni Cu ZnSc Ti V Cr

Rb Sr In Sn Sb Te I XeTc Ru Rh Pd Ag CdY Zr Nb Mo

Cs Ba Tl Pb Bi Po At RnRe Os Ir Pt Au Hg57-71 Hf Ta W

Ho Er Tm Yb LuPm Sm Eu Gd Tb DyCe Pr Nd

Es Fm Md No LrNp Pu Am Cm Bk CfTh Pa U

Fr Ra Ac

Lanthanides La

Actinides

Is High Flux Necessary?

A/t = n Φ σγ εCount rate= No. atoms × flux × cross-sec. × eff.1 cps = 1021 × ×1b (10-24cm2) × 10-4

107 cm-2 s-1

For standard PGAA it is not needed

It opens a new directionLowering sample mass, cross-sec, or eff.

PGAA facility at Garching

NSE

KWS 2

SPHERES

KWS 1

RefSANSSANS-1

Neutron guide hall

KWS 3 DNS

MARIA

MIRA

PGAA

RESEDA

MEPHISTO

NREX+

TOF-TOF

BioDiff

WP

PGAA facility at Garching

From L. Canella et al. NIM 636 (2010) 108

Focusing neutron guide

• 5.8 m elliptical guide• 1.1 m elliptical extension (removeable)

Flux in focal point: 6.1x1010 cm-2 s-1

(highest reported)

Collimator and elliptical guide intechangeable

By Harald Türck

Collimator and elliptical guide intechangeable

Elliptical guide in B shielding

Shielding arrangementsBest arrangement: separate chambers

Collimator / guide Sample

DetectorB

Li

Pb

Beam stop

Active shielding: BGO

Latest reconstruction 2012 09

Shielded PGAA instrument

Detector system (old and new BGO)

Characteristics

• Highest flux: 4x1010 cm-2 s-1

– New background 400 cps• Working flux:2x109 cm-2 s-1

– New background: 20 cps

– Signal/background ratio: best in the world

20

200

500

50,000

What do we irradiate?

• PGAA in typical beams– Sample: 100mg—1g– Teflon bag: 50—200mg

• In high-flux– Sample: ~1mg– Packing???

Background in high flux

• No sample holder: 400 cps• + Teflon sample holder: +150 cps• + Teflon packing: +150 cps• Air: +300 cps

• Bg peaks from stuctural components (like Al, Fe, Pb) depend on the scattering of the sample

Traditional packing

• C: 3.8 mbarn, F: 9.6 mbarn– Teflon, FEP, PTFE

• Teflon bag: 0.025mm, heat sealed• Teflon string:0.3mm diam

• Both approx. 50mg/cm2

0.5μm Mylar film in Teflon frame

Electronics

• New digital electronics– Present resolution =

nominal resolution (1.9 keV at 1,33MeV)

– Higher countrate• Max earlier: 5000cps• Max now: >50,000cps

– Nonlinearity <1keV

Applications

Low massLow cross-section

NAARadioactive nuclides

1) Micro-meteorites

• Mass ~0.3—2mg• In 0.5μm Mylar (PET) foil• No Teflon string

R.B. Firestone

Z El M mmeas

unc%

mBkg

unc%

mnet

ox.st.

mox

unc%

1 H 1.008 5.47E-6 0.8 1.36E-6 1.5 4.11E-6 1 3.67E-5 1.25 B 10.81 6.74E-7 0.3 1.15E-8 1.0 6.63E-7 3 2.13E-6 0.3

13 Al 26.98 4.51E-5 2.2 1.96E-5 2.5 2.55E-5 3 4.82E-5 4.14 Si 28.09 9.22E-5 2.8 1.96E-5 3.7 7.26E-5 4 1.55E-4 3.716 S 32.07 4.67E-6 14. 0.0 4.67E-6 6 1.17E-5 14.17 Cl 35.45 1.09E-6 18. 1.15E-7 22. 9.71E-7 -1 9.71E-7 20.20 Ca 40.08 2.10E-5 19. 0.0 2.10E-5 2 2.94E-5 19.22 Ti 47.87 2.45E-4 2.6 1.40E-7 22. 2.45E-4 4 4.09E-4 2.624 Cr 52 4.03E-6 14. 0.0 4.03E-6 3 5.89E-6 14.25 Mn 54.94 8.75E-6 2.0 0.0 8.75E-6 3 1.26E-5 2.026 Fe 55.85 2.31E-4 2.4 1.16E-6 10. 2.30E-4 3 3.28E-4 2.427 Co 58.93 3.06E-6 3.1 0.0 3.06E-6 2 3.89E-6 3.160 Nd 144.2 8.89E-7 13. 0.0 8.89E-7 3 1.04E-6 13.62 Sm 150.4 5.32E-8 6. 0.0 5.32E-8 3 6.16E-8 6.64 Gd 157.3 9.89E-8 7. 0.0 9.89E-8 3 1.14E-7 7.

1 mg

2) Air filters

• ~1mg PC filters, <1mg dust • In 0.5μm Mylar (PET) foil

• Detection limit for certain trace elements (B, Gd, Sm) <1ng !!

Nuno Canha, Marina Almeida

Air filter typical compositionZ El M m

measunc%

mBkg

unc%

mnet

ox.st.

mox

unc%

5 B 10.81 8.16E-8 0.5 5.13E-8 0.7 3.03E-8 3 9.75E-8 1.811 Na 22.99 3.65E-5 3.8 4.80E-6 11. 3.17E-5 1 4.27E-5 5.13 Al 26.98 4.33E-5 3.3 1.67E-5 6. 2.66E-5 3 5.03E-5 7.14 Si 28.09 8.56E-5 3.2 2.34E-5 5. 6.22E-5 4 1.33E-4 5.16 S 32.07 1.11E-5 8. 0.0 1.11E-5 6 2.77E-5 8.17 Cl 35.45 3.55E-5 1.4 3.00E-7 16. 3.52E-5 -1 3.52E-5 1.419 K 39.1 6.95E-6 7. 0.0 6.95E-6 1 8.37E-6 7.20 Ca 40.08 2.34E-5 6. 3.26E-6 9. 2.02E-5 2 2.82E-5 7.22 Ti 47.87 1.89E-6 5. 0.0 1.89E-6 4 3.15E-6 5.26 Fe 55.85 1.73E-5 4. 1.30E-6 11. 1.60E-5 3 2.29E-5 4.27 Co 58.93 1.15E-6 9. 4.27E-7 26. 7.27E-7 2 9.24E-7 21.29 Cu 63.55 2.93E-6 14. 0.0 2.93E-6 2 3.67E-6 14.62 Sm 150.4 2.91E-9 9. 0.0 2.91E-9 3 3.37E-9 9.64 Gd 157.3 2.38E-9 13. 0.0 2.38E-9 3 2.75E-9 13.82 Pb 207.2 2.10E-4 9. 1.26E-4 8. 8.45E-5 2 9.10E-5 25.

Mass = 0.45 mg

3) Cross-sections of light nuclides

Nuclide Abu. % Xsec (mb)1H 99.985 332.6±0.2%2D 0.015 0.52 ±1.3%

3He 1.4ppm 0.03±30%3He(n,p) 5333 barn

4He 99.9999 06Li 7.5 39 ± 8%

6Li(n,α) 940 barn7Li 92.5 45 ± 7%

9Be 100 8.8 ± 11%10B 19.9 500±40%

10B(n,α) 3837 barn 11B 80.1 5.5±60%

Nuclide Abu. % Xsec (mb)12C 98.89 3.53±2%13C 1.11 1.37±3%14N 99.634 79.8±2%

14N(n,p) 1830 barn15N 0.366 24±33%16O 99.762 0.19±10%17O 0.038 0.54±17%

17O(n,α) 235 barn18O 0.2 0.16±7%19F 100 9.6±5%

R.B. Firestone

4) NAA in high-flux beam

• Almost the flux of a small reactor – Parallel, not isotropic

• No epithermal or fast neutrons• Transfer system needed• Relatively large samples (for NAA)• NAA and PGAA can easily be combined• Cyclic activation option is simple (chopper)

NAA in high flux beam

• NIST SRM• Trace Al (20 ppb?)

– Few minutes irradiation– Few minutes counting

• Other components: – Na, Cl, Mn, Cu, K.– They agree with the certified values

Rolf Zeisler

5) Irradiation radioactive nuclides

Induced activity > natural radioactivity– MBq activities– Half-life >100a– Mass > 0.1mg– Cross-sec. >100b

• Radioactive samples irradiated at FRM2:– 30μg (!!) 243Am– ~100 μg 237Np, 242Pu

TANDEM project

• Trans-Uranium Actinides’ Nuclear Data –Evaluation and Measurement

• Collaboration of– Jülich (FZJ)– Garching (FRM II, TUM)– Budapest (CER, HAS)– Berkeley (LBNL)

• To improve (n,γ) data for trans-U actinides

Future

• Sample holder• Low-background counting facility• Transfer system

• A similar facility is under construction at NIST (Gaitherburgh near Washington)

Thank you