Particle spectrometry

Marechal CN, Telouk P, Alberede F (1999) Precise analysis of copper and zinc isotopic compositiorrs by plasma-source mass spectrometry. Chem Geol 156 251-273 Martin P, Hancock GJ, Paulka S, Akber RA (1995) Determination of Ac-227 by alpha-particle spectrometry. Appl Radiat Isot 46 1065-1070... 

The analytical separation of 239plutonium and 240plutonium in environmental samples is usually not possible using a-particle spectrometry because of the small difference in a energies, but this problem was solved in one study by additional measurement of the L X-rays emitted from the same sources [ 39 ]. 

A water sample that you submitted for analysis is found to have a 235U 238U atom/atom ratio of 1 146 by radiochemical analysis (alpha-particle spectrometry), but when measured by ICP-MS has a 235U 238U atom/atom ratio of 1 62. What do you suspect happened regarding these analyses Be specific. 

Surface-barrier detectors are prepared from n-type Si. On one side the surface is etched and exposed to air to produce an oxide layer, and a thin gold layer is deposited for electrical contact. By this procedure a p-layer is obtained with a thickness of < 1 pm. Another method of preparation of surface-barrier detectors is the vapour deposition of A1 on Si. The maximum thickness of the depicted layer is of the order of 1 mm. Surface-barrier detectors are mainly used for charged-particle spectrometry and for a and f spectrometry. Optimal energy resolution for and / radiation is obtained with thin detectors of small surface area. For instance, at surface areas of about 1 to 4cm, the energy resolution for a and f radiation is about 10 to 30keV. 

It has been shown (Holm et al., 1990) that ion implanted detectors can be used not only for alpha particle spectrometry but also for beta particle spectrometry. Their drawback, however, is the high background around 100 keV and noise below 1 keV. 

Another problem of importance to safeguards and reactor fuel technology is the measurement of the relative abundance of plutonium isotopes. In addition to y- and X-ray spectrometry (Gunnick, 1981), alpha particle spectrometry has also been used (Bland et al., 1992 Amoundry and Burger, 1984 Bortels and Collaers, 1987). This... 

Preparation of purified samples for alpha-particle spectrometry is usually by either electrodeposition or micro-coprecipitation. Either technique takes at least an hour. Many beta-particle emitters are precipitated with several milligrams of carrier and weighted for determining the chemical yield prior to counting, which also takes time. In contrast, a few millilitres of solution are satisfactory for ICP-MS. If the analyte concentration should exceed the linear part of the calibration curve, a simple dilution overcomes the problem. 

Helmbold, M., 1985. Multielement analysi.s by means of alpha particle spectrometry. In Sansoni, B. (Ed.), Instrumentelle Multielementanalyse. VCH Publishers, Weinheim, pp. 98-108. 

The word spectroscopy is widely used to mean the separation, detection, and recording of energy changes (resonance peaks) involving nuclei, atoms, or molecules. These changes are due to the emission, absorption, or scattering of electromagnetic radiation or particles. Spectrometry is that branch of physical science that treats the measurement of spectra. 

The amount of carrier added to the radionuclide solution conventionally is selected for ease of weighing with an accuracy of 1 % or better for yields of 50-100%. Low carrier amounts for processing thin sources for alpha-particle spectrometry (see Section 7.2.1) may require specially selected purification and yield determination techniques. 

Loss of a fraction of a radioactive daughter from a radioactive source can be expected due to the recoil discussed in Section 4.2. For example, the radioactive daughter Ra from a very thin source of Th can transfer to a facing surface by recoil. This process can be applied beneficially to prepare a pure source of the radioactive daughter or can be a problem in contaminating the detector during alpha-particle spectrometry. 

Cl284-94 listed in Appendix A-1. Other actinides that emit alpha particles are also prepared with this method. After pnrification, nranium isotopes usually are identified and measured by alpha-particle spectrometry with silicon diodes. Tracer can be added to the initial solution and counted with the uranium isotopes of interest. 

The critical requirement for alpha-particle spectrometry to achieve good characteristic peak resolution, shown in Fig. 9.1 and described in Section 8.3.3, is the preparation of a very thin and uniform source. Less rigorous criteria for resolution can be met if the several radioisotopes to be measured and the tracer have widely different alpha-particle energies, only a single radionuclide is known to be present either initially or after chemical separation, or the measurement is for screening purposes. A sample may be prepared for screening with limited prior separation or none, and without tracer addition, if previous tests have demonstrated that the process causes no losses for all radionuclides of interest. 

The preceding uncertainty equations presume that all pairs of input estimates are uncorrelated, which may or may not be true. One of the most common examples of correlated input estimates in radioanalytical chemistry occurs when the chemical yield Y is calculated from an equation involving the counting efficiency e. This happens in measurements by alpha-particle spectrometry with an isotopic tracer. In this case, the uncertainty equation can be simplified by treating the product e x T as a single variable. What happens in effect is that the efficiency cancels out of the activity equation and for this reason its uncertainty can be considered to be zero ... 

The problem of uncertainty evaluation for background corrections in alpha-particle spectrometry is that the background count rate may be extremely low. Counting for several days may yield only a few, or even zero, counts. At least two issues may arise. First, the Poisson uncertainty estimate is relatively imprecise when the mean count is so low. In the worst case, both the background count Cb and the gross count Cq are zero, so that the uncertainty equation will calculate zero uncertainty for the measured activity, which is inappropriate for a laboratory to report. In any situation where it is possible to observe zero counts (C = 0), the Poisson uncertainty estimator Vc should be replaced by VC -I- 1. Low-level alpha particle spectrometry is a situation where zero counts may indeed be observed. Second, it becomes important to consider possible variability in the background (e.g., from spurious counts), which may be relatively large in comparison to the Poisson uncertainty. 

S amples prepared for alpha-particle spectrometry are very thin and uniform. The purification procedure should have achieved high yield and low contamination by extraneous solids. Failure to prepare a thin sample is shown by poor peak spectral resolution with excessive low-energy tailing. Incomplete radiochemical purification in preceding steps is revealed by the appearance of peaks from radionuclides, which should have been removed. 

The counting room also houses alpha-particle spectrometry systems, which require a vacuum line or pumps. These detectors can be placed anywhere within the counting room and operated without interference from any elevated external radiation background. 

D19.04 D3084-96 Standard Practice for Alpha-Particle Spectrometry of Water... 

Amoudry F, Burger P (1984) Determination of 239Pu/ 240Pu isotopic ratio by high resolution alpha-particle spectrometry, alpha-particle spectrometry and low-level measurement, Harwell, 10-13 May 1983, CEA-CONF-6775 Nud Instrum Methods Phys Res 223 360... 

Booth L, Gillespie B, Seaman G (1997) In 5th nondestructive assay/nondestructive examination waste characterization conference, Salt Lake City Bortels G (1991) Status of high-resolution alpha-particle spectrometry using Si detectors, EUR-1368613. In Annual symposium on safeguards and nuclear material management, Avignon, France, 14-16 May, pp 159-163(745 pp)... 

Th and U isotopes activity concentrations were determined in the samples by alpha-particle spectrometiy. For the detennination of these isotopes by alpha-particle spectrometry in the samples, a sequential well-established radiochemical method to the samples was applied [19]. In this method, the isotopes are electrodeposited onto stainless steel discs after its isolation from the bulk matrixes. The planchets were measured using an EG G Ortec alpha spectiometiy system with ion-implanted silicon detectors. Counting times ranged from 2 days to 4 days, depending on the activity concentrations and the recovery obtained in the chemical separation. 

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