PROMPT GAMMA ACTIVATION
ANALYSIS FACILITY



This facility serves for non-destructive analysis of elemental composition by observing neutron-capture prompt gamma rays. Hence the name prompt gamma activation analysis, PGAA in short. It has been described in detail in refs. 1,2.

The instrument is located at the end position of neutron guide NV1. The experimental area is a 35× m2 place, backed by the rear wall of the guide hall. The pneumatic beam shutter at the end of the guide lets the neutrons enter the 3 m long evacuated aluminium tube extending across the experimental area, down to the beam stop at the rear wall. The targets are positioned on a thin aluminium frame, placed in a small chamber, which can be evacuated.

The basic gamma-spectroscopic instrument consists of an n-type high-purity germanium (HPGe) main detector with closed-end coaxial geometry and a BGO scintillator guard detector annulus, surrounded by a 10 cm thick lead shielding. The whole system is positioned on a table, which can be moved in either direction. A second (15%) HPGe detector is also available for γ -γ coincidence measurements, facilitated by a multiparameter data acquisition system.

Main specifications

Neutron guide cross section: 2.5×10 cm2
Thermal-equivalent flux at target: 3×107 cm-2s-1
Vacuum in target chamber (optional): ≈ 1 mbar
Target chamber Al-window thickness 0.5 mm
Form of target at room temperature: Solid, powder, liquid, gas in pressure container
Target packing at atmospheric pressure: sealed FEP Teflon bag or vial
Largest target dimensions: 3× 3× 12 cm3
γ -ray detector n-type coax. HPGe, with BGO shield
Distance from target to detector window: 23.5 cm
HPGe window: Al, 0.5 mm
Relative efficiency: 25% at 1332 keV (60Co)
FWHM: 1.8 keV at 1332 keV (60Co)
Compton suppression enhancement: ≈ 5 (1332 keV) to ≈ 40 (7000 keV)

Responsible: T. Belgya, Institute of Isotopes, Budapest

References

  1. G. Molnár et al., A New Prompt Gamma-Activation Facility at Budapest, J. Radioanal. Nucl. Chem,
    215/1, pp 111-115 (1997)
  2. T. Belgya et al., in: "9th International Symp. On Capture Gamma-Ray Spectroscopy and Related Topics",
    Budapest 8-12 Oct. 1996, (Eds. G. Molnár, T. Belgya, Zs. Révay, Springer-Verlag Budapest, 1997) pp 826
  3. see Annexes

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