Characteristic K, L and M X-ray and background production trends from high energy heavy ion bombardment were investigated
on a series of target elements (14≤Z≤92) using 0.5 MeV/amu and 1 MeV/amu Nn+, On+, Cun+, Krn+ and Xen+ beams. X-ray production for K and L shell X-rays roughly followed the same trends, i.e. increased yield with projectile size
and energy and decreased yield with increasing X-ray energy. Broad simultaneous multielement coverage can be achieved using
K, L and M Lines. Experimental detection limits of 0.8 to 10 ppm were obtained for elements between Mn and Se with K X-ray
detection, between Sm and Pb using L X-ray detection, and for Th and U via M X-ray detection in biological samples with a
1MeV/amu Kr7+ beam of 70 nA for 1000 s. These detection limits are better for many elements than those obtained with a 1.65 MeV proton
18O induced radioactivation may be used for the trace detection of1H via1H (18O, n)18F. Matrices in which this reaction is interference-free include: Al, Si, S, K, Ti, V, Ni, Cu and Zn. However, due to numerous
radioisotopes created at the bombarding energies used (E≥51 MeV), a post-irradiation chemical separation of18F is required.18O activation also appears as a promising means for the trace determination of S[S(18O, x)47V], Si[Si(18O, x)43–44Sc] and B[B(18O, x)37Mg].
Excitation functions for proton energies up to 20 MeV have been measured for65Cu(p, n)65Zn; Sn (p, xn)115Sb,116mSb,117Sb,118mSb; Mo (p, xn)94Tc; Te (p, xn)121I,123I,128I,130I; Pd (p, xn)104Ag; Cd (p, xn)109In,110mIn,113mIn; Cs (p, xn)133mBa. The precision of the measurements (overall error estimated at ≤20%) and the conditions for interference-free detection
of these elements at trace levels are also discussed.
7Li induced radioactivation was used for the trace determination of hydrogen via the1H(7Li, n)7 Be reaction. At 21 MeV7Li, only boron and magnesium present small nuclear interferences. An activation curve has been established by bombarding a stack of thin mylar foils. The comparison of this curve with the excitation function for the forward reaction, namely7Li(p, n)7 Be, shows that the recoil range from the superficial hydrogen atoms is only 1.7 mg·cm–2, allowing post-irradiation etching. Hydrogen has been determined in titanium and lead bronze at the 100 ppm level with a relative precision of 6 to 10%. Studies of 32 potential interfering elements suggest the extension of Li activation to the trace determination of Na[23Na(7Li,6Li)24Na] and K[39K(7Li, d)44m,44Sc].
Fast neutron activation analysis (FNAA) was investigated as a possible on-site preliminary screening technique for metal contamination of soil. Two metals, Cu and Zn, were used in a laboratory setting to evaluate the possibility of detecting metal contamination of soil at or below the maximum permissible metal concentration in soil. Varying quantities of compounds of the selected metals were mixed into a prepared soil column for analysis of signal intensity as a function of concentration in the soil. Experiments were conducted with a sealed tube neutron generator and a germanium gamma-ray detector. Both metals produced signal levels distinguishable from background soil concentrations at the maximum permissible level.
Nuclear Analytical Chemistry at Texas A&M University is based in large part on the facilities of the Center for Chemical Characterization and Analysis and the Nuclear Science Center. This paper describes the capabilities of these two centers for instrumental and fast neutron activation analysis, neutron depth profiling, prompt gamma activation analysis, neutron radiography and the unique features of the large volume irradiation cell and reactor pulsing operation.
10B induced radioactivation was used for the trace determination of hydrogen via the1H(10B )7Be reaction. At 27 MeV10B++, only boron and magnesium present small nuclear interferences. An activation curve has been established by bombarding stacks of thin mylar foils. The comparison of this curve with the excitation function for the forward reaction, namely10B(p, )7Be, shows that the recoil range from superficial hydrogen atoms is small. Hydrogen has been determined in titanium and lead bronze at the 100 ppm level. Studies of 21 potential interfering elements suggest that10B activation might be suitable for the trace determination of lithium [6Li(10b,n)15O and7Li(10B, 2n)15O] and oxygen [18O(10B,)24Na].
Both7Li and10B induced radioactivation were applied to trace determination of hydrogen via the1H(7Li,n)7Be and1H(10B, )7Be reactions. In both cases, boron and magnesium present nuclear interferences, but their extent does not exceed 0.5%. At the bombarding energies used, 21 MeV7Li++ and 27 MeV10B++ the detection limits are respectively 2 and 0.5 ppm for an iron matrix irradiated for two hours. Due to the recoil of7Be, the samples were carefully prepared to avoid superficial hydrogen contamination. A series of samples which hydrogen content ranges from 15 to 120 ppm was examined, and the results obtained with the two beams were compared.
The use of 7 MeV6Li+ for heavy ion activation analysis was investigated. A survey of reactions, involving targets of lithium through oxygen inclusive,
were studied for production of β+ radioactivation products with half-lives of 101−105 seconds. Specific activities for all reactions under the experimental conditions are reported and their use for analysis
Nondestructive heavy ion activation analysis has been used to determine the carbon content in various NBS SRM steel samples
with a 7.0MeV6Li+ beam. The reaction12C(6Li, αn)13N allows for carbon analysis with the only possible interference being beryllium,9Be(6Li, 2n)13N. Under interference-free conditions, and employing a post-irradiation etch, the detection limit for carbon analysis in steel
was 5 ppm.