Alpha particle energies

Determine counting efficiency of the proportional detector in Step 5 for three 3,000-s periods to measure alpha particles and beta particles. Record in Data Table 7.2. Also perform overnight count (50,000 s) for alpha-particle spectral analysis of the planchet to identify the uranium isotopes and any other radionuclides and to determine their relative amounts from their alpha-particle energy spectra and record results in Data Table 7.2. Count alpha- and beta-particle background in proportional counter and alpha-particle spectral background in spectrometer for at least the same periods. 

R, = gross c/s that appear in the Pu alpha-particle energy region B bkg = background c/s in the same alpha-particle energy region as for the Pu... 

Rlr = gross c/s that appear in the, rPu alpha-particle energy region,... 

Btrbkg = background c/s in the same alpha-particle energy as for the "Pu,... 

Frolov, E.A., A precision facility for measuring alpha-particle energies and flux density. Appl. Radiat. Isot., 43 (1992) 211-222. 

The Working Level (WL) is equal to any combination of the short-lived decay products of Rn in I L of air resulting in the ultimate emission by them of 1.3 x 10 MeV of alpha-particle energy (obtained from 9800 Rn atoms or about 0.5 pCi/L). Equivalent uranium (eU) is U concentration estimated from the Bi concentration (usually determined by gamma-ray spectrometry) assuming secular equilibrium. 

Figure 13.4 Alpha-particle energy straggling for (a) thin, and (b) thick foils of silver, [(a) Data ( )...

Measuring alpha particles with an LS counter is an attractive option because the counting efficiency is near 100% and no self-absorption problem exists. After the usual sequence of separations for radionuclides such as thorium, uranium, and transuranium isotopes, the radionuclide is prepared in the final solution for counting and yield determination. A tracer that emits alpha particles at a sufficiently distinct energy is added initially to measure yield. The factor that controls detection sensitivity is the background, typically of 1-2 c/m in the alpha-particle energy region of the LS counter. 

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. 

For some radionuclide mixtures, a group separation, e.g., for actinides, is satisfactory for measuring its component radionuclides by alpha-particle spectral analysis. As discussed in Section 6.4.1, further chemical separation is needed for radionuclides that emit alpha particles of almost the same energies, or even a mass spectrometer for radioisotopes of the same element with almost identical alpha-particle energies such as Pu and Pu. 

At the same time, other aliquots are counted with gas proportional and LS counters to determine the presence of alpha and beta particles. The detectors are operated in a mode that distinguishes between alpha and beta particles. The LS counter can suggest maximum beta-particle energies and show alpha-particle energies from... 

Therefore, from a fusion reactor point of view, the utilization of the energy of alpha particles is different from that of the neutrons. The alpha particles energy can and must be used for plasma heating (alpha heating), whereas the neutrons energy must be absorbed... 

In the most recent reactor studies a way out of this dilemma was sought by applying the cold plasma mantle method of impurity control. Unfortunately, the experimental basis is not yet adequate for technological problem identification. But there is one thing that can already be stated, i,e. that removal of the plasma and alpha particle energies in the case of the cold plasma mantle has to be performed very probably via the first wall, this having the previously mentioned negative effects on its neutronic load capacity and lifetime. 

Resume TECHNICALLY CREDIBLE IDEAS FOR IMPURITY CONTROL, WALL PROTECTION, ALPHA PARTICLE ENERGY REMOVAL AND EXHAUST IN COMMERCIAL TOKAMAK REACTORS ARE NOT AVAILABLE. 

Alpha-particle energy deposition Particle confinement... 

The radioactive isotope Pu, used in pacemakers, decays by emitting an alpha particle with a half-life of 86 yr. (a) Write an equation for the decay process, (b) The energy of the emitted alpha particle is 9.0 X 10 J, which is the energy per decay. Assume that all the alpha particle energy is used to run the pacemaker, calculate the power output at / = 0 and... 

As with Md and No, the physical separation of the Lr atoms from the target material and subsequent rapid collection is best accomplished using a recoil-atom gas-jet system of some type. Because of the short half-life of Lr, further chemical purification is not feasible before study. It is distinguished from other possible alpha-emitting nuclides in the sample by its unique alpha-particle energy of 8.24 MeV. 

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