Alpha spectrum

Figure 2. Alpha spectrum for a radium adsorbing manganese-oxide thin film exposed to a groundwater sample, after Surbeck (2000) and Eikenberg et al. (2001b). A 2x2 cm sheet is exposed to O.l-l.O L of sample for 2 days, capturing nearly all of the radium in the sample. These sample discs can be used directly for low-level alpha spectrometry without the need for further separation and preparation methods to produce planar sample sources. Energy resolution is nearly as good as for electroplated sources, and detection limits are typically 0.2 mBqA (6 fg Ra/L) for Ra and " Ra for a one-week counting period. These sensitivities are comparable to traditional methods of alpha spectrometry. [Used by permission of Elsevier Science, from Eikenberg et al. (2001), J Environ Radioact, Vol. 54, Fig. 4, p. 117]...

Figure 13.3 Alpha spectrum of oxidised and reduced plutonium species as separated by the neodymium fluoride technique (oxidised yield tracer 236Pu, reduced yield tracer 242Pu).

Figure 7. Alpha spectrum of Pu fraction from 100 gram soil.

The determination of Po is relatively straightforward, due to the ease of source preparation by spontaneous deposition onto metal surfaces and the uncomplicated alpha spectrum. Although several optimisation studies have been carried out, published source preparation methods remain remarkably diverse. For this review about 130 papers mainly focussed on analytical methodology of Po were collected and critically examined. The literature surveyed included analysis of air, fresh water, rainwater, seawater, soil, sediment, coal, tobacco, phosphogypsum, foodstuffs, marine organisms, vegetation, human bone, and biota (Table 3). 

Alpha particles emitted from nuclides which decay to a single level are observed as mono-energy particles. On transitions given the branching ratio in Table 5.6, multiple alpha energies are observed. Such a fine structure in the alpha spectrum comes about because an alpha emitter may decay to any one of several discrete energy levels of its daughter. Am is commonly used as a standard source. 

Figure 13.14 The Am alpha spectrum obtained with a silicon surface-barrier detector (from Canberra).

The aim of the source preparation is to obtain very thin, smooth, and uniform deposit to minimize the effects of self-absorption and retrodifiussion, which alter the resolution of the alpha spectrum. Some of the methods are listed below ... 

Alpha spectrum of a Pu/ °Pu mixture obtained with a PIPS detector of 9 keV resolution... 

Ali S, Terracol SF, Drury OB, Friedrich S (2006) Nucl Instrum Methods Phys Res A 559 542-544 Ali S, Hau ID, Niedermayr TR, Friedrich S (2008) J Radioanal Nucl Chem 276(3) 749-753 Amoudry F (1983) SMMA alpha spectrum deconvolution code, CEA-N-2366... 

FIGURE 1.28 (a) Schematic representation of alpha particle emission and (b) alpha spectrum of uranium (with a spike) after separation from other actinides in a soil sample (also... 

Figure 3 Alpha spectrum of Ds fraction (with Pt, Au, Po isotopes) of stratospheric dust, obtained during 134 days measurement. Upper part displays the high-energy part of spectrum with linear vertical scale, lower pari shows whole spectrum in logarithmic scale (discriminated at 20 counts level) expanded high energy part is marked with black arrows. Vain arrows indicate the positions of searched peaks.

The later chemical work of Silva et was done with the Berkeley 65 s, 261 isotope, and this longer half-life enabled a rapid cation-exchange operation to be undertaken. The material was loaded on to Dowex 50 resin and eluted with ammonium a-hydroxyisobutyrate. Despite complications caused by the daughter No having a very similar alpha spectrum to Rf, it was concluded that Rf eluted in much the same fraction as Hf and Zr tracers, in contrast to actinide tracers which were not eluted in these conditions. 

Methanol is used in the carbon source since the solubility of B2O3 in acetone is very low. B2O3 is added to reach a B/C atomic ratio of 0.01 and the mixture is then ultrasonicated for complete dissolution. The boron concentration in a film prepared under these conditions was ca. 1.5 x lO i cm as estimated by Notsu et al., based on nuclear reaction measurements [iiB(p,a) Be], carried out by means of I meV proton bombardment and subsequent comparison of the alpha spectrum in the 6-8 MeV region with a... 

Alpha spectrum of a volatilized source of obtained with... 

To determine the amount of Pu In the original saiig>le. It Is necessary to measure In a Frisch chamber the alpha spectrum of the plate prepared In Step 8. The ratio of Pu-239 and Pu-240 activity to Pu-236 activity Is calculated. If the ratio is multiplied by the original activity of Pu-236 added, the original activity of Pu-239 plus Pu-2 0 Cein be obtained. Prom the mass analysis a Fu-239 to Pu-240 atom ratio Is obtained. The specific activity of the mixture Is calculated from that of the Individual Isotopes. The Pu-239 plus Pu-240 activity can be converted to Pu-239 plus Pu-24 0 weight by dividing this activity by the specific activity of the mixture. 

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