Prompt Gamma Activation Analysis

The facility for the measurements of 10B concentrations in biological samples includes HPGe detector with 25% relative efficiency and associated Pb - 6Li2CO3 shielding. Described facility is installed at the distance of 1 m from the exit of the neutron guide. At the target position the neutron flux is approximately 3×106 n cm-2 s-1 at the reactor power of 8 MW. This facility makes it possible to determine 10B concentration of 1 ppm in 1 ml samples with statistical uncertainty of 5% within 15 min. This instrument is in a common property with Nuclear Research Institute, plc.

Applications:
The experimental set-up was mainly developed for the on-line determination of 10B concentrations of ppm-order in biological samples. This facility can also be used for determination of other isotopes with a sufficiently large (n,g) cross-section.

Instrument  Parameters

Neutron flux   3·106 n/cm-2 s-1
Beam cross section at target position
   25 x 5 mm2
Detector
   HPGe (25% relative efficiency)
Sample enclosure for liquid and powder sample  

Teflon cylinder vial :   Diameter - 10mm & Height - 10mm  

 

Expected interference-free detection limit for PGAA instrument at research reactor LVR-15 assuming 24h irradiation.

Element Det. limit  (µg) Eγ (keV) Element Det. limit  (µg) Eγ (keV
 Hydrogen     20  2223  Cobalt      20
  230, 556
 Boron       0.06  478  Nickel    200
  283, 465
 Nitrogen  4000  1885, 5298
  Copper      10
  159, 278
 Sodium     70  472, 869
  Zinc    700
  115, 1077
 Magnesium  2000  585,1809  Selenium      40
  239
 Aluminium   500  1779, 7724
  Molybdenum    150
  720, 778
 Phosphorus  2000  637, 1072  Silver
     30  192, 236
 Sulfur   300  840,  2379
  Cadmium        0.1
  559, 651
 Chlorine     10
  517, 786
  Samarium        0.03
  333, 439
 Potassium    100
  770, 7771
  Gadolinium        0.02
  182, 1186
 Calcium    600
  519, 1943
  Gold      30
  215
 Titanium     40
  342, 1381
  Mercury        1.5
  368
 Chromium   150
  749,834  Lead  40000 
 7368
 Manganese     30
  847, 1811
  Neodymium        10
  619, 697
 Iron   300
  352, 7631
  Indium          5
  162, 186

 

Application Example:

The deterimantion of boron concentration in graphene powder.

Electronic properties of graphene can be changed by doping with electron-donating (nitrogen, phosphorus) or electron-withdrawing (boron) groups. Level of doping (concentration of doped group) is crucial for for tuning the electrochemistry performance of graphene. Boron-doped were prepared by thermal exfoliation of graphite oxide in an atmosphere with boron trifuoride diethyl etherate at high temperatures. The effect of exfoliation temperature as well as of hydrogen content in atmosphere were investigated using PGAA at LVR-15 Řež.
Special software was developed for precise fitting of Doppler-broadened boron peak at 478 keV.
 
Fig. 1 Example of Doppler-broadened boron peak at 478 keV  in gamma spectrum of graphene powder.