Theoretical Wood Densitometry: II. Optimal X-ray Energy For Wood Density Measurement
Keywords:Optimal X-ray energy, wood densitometry, differential transmission probability, maximum radiation resolution, wood density
AbstractUsing a comparable approach, we extended the theoretical X-ray wood densitometric models to a case encountered in practice. Optimal X-ray energy was treated as the photon energy of the X-radiation which produced the maximum radiation resolution, as measured by differential transmission probabilities detected in a densitometric experiment. Parametric representation of radiation resolutions revealed that the maximum resolution of a specific densitometric procedure is governed by the range of densities in a given wood. The maximum radiation resolution obtainable in a particular wood densitometric experiment can be calculated readily from two equations derived in this study. Examples show that under "good architecture" conditions (1) transmission probabilities for a given wood densitometric experiment increase their magnitudes as the X-ray becomes more energetic, yet the maximum radiation resolution remains constant for a given set of parametric values; (2) optimal X-ray energies, for nine types of coniferous wood, are in the range of 5.13-5.69 keV for 1.0-mm-thick samples; (3) wood with a broader density range results in higher maximum resolution when irradiated by the theoretically optimal X-ray energy; and (4) accurate wood density measurements could be achieved only if the radiation energy used was near the optimal level. Regarding the architecture of a radiation detection system, the advantage of using a monochromator to reduce the X-ray energy continuum so as to increase the accuracy of wood density measurements was examined.
Cown, D. J., and M. L. Parker. 1978. Comparison of annual ring density profiles in hardwoods and softwoods by X-ray densitometry. Can. J. For. Res. 8(4):442-449.nEchols, R. M. 1970. Moving-slit radiography of wood samples for incremental measurements. Pages 34-36 in J. H. G. Smith and J. Worrall, eds. Tree-ring analysis with special reference to Northwest America. Univ. Brit. Col. Fac. Bull. No. 7, Vancouver, BC.nEchols, R. M. 1972. Product suitability of wood … determined by density gradients across growth rings. USDA For. Serv. Res. Note PSW-273, 6 pp.nFengel, D., and G. Wegener. 1984. Wood: Chemistry, ultrastructure, reactions. Walter de Gruyter & Co., Berlin. 613 pp.nHagglund, E. 1951. Chemistry of wood. Academic Press, NY. 631 pp.nHubbell, J. H. 1982. Photon mass attenuation and energy-absorption coefficients from 1 keV to 20 MeV. Int. J. Appl. Radiat. Isot. 33:1269-1290.nJacoby, G. C., and R. S. Perry. 1981. Lead-screw device for in-motion X-rays of tree cores. Wood Sci. 13(4):199-201.nLiu, C. J., J. R. Olson, Y. Tian, and Q. Shen. 1987. Theoretical wood densitometry: (I) Mass attenuation equations and wood density models. Wood Fiber Sci. 20(1):22-34.nMcNeely, R., J. Neale, M. Benkel, J. Rustenburg, and J. Terasmae. 1973. Application of X-ray densitometry in dendrochronology. Brock Univ., Dept. Geol. Sci., St. Catharines, Ont. Res. Rep. Ser. 16.nMilson, S. J. 1979. Within- and between-tree variation in certain properties of annual rings of Sessile oak Quercus petraea (Mattuschda) Liebl. as a source of dendrochronological information. Unpubl. Ph.D. Thesis, Liverpool Polytec., Dept. Biol., Liverpool, UK.nParker, M. L., and L. A. Jozsa. 1973. X-ray scanning machine for tree-ring width and density analyses. Wood Fiber 5(3): 192-197.nVeigele, W. J. 1973. Photon cross sections from 0.1 keV to 1 MeV for elements Z = 1 to Z = 94. Atomic Data Tables 5(1):51-111.n
The copyright of an article published in Wood and Fiber Science is transferred to the Society of Wood Science and Technology (for U. S. Government employees: to the extent transferable), effective if and when the article is accepted for publication. This transfer grants the Society of Wood Science and Technology permission to republish all or any part of the article in any form, e.g., reprints for sale, microfiche, proceedings, etc. However, the authors reserve the following as set forth in the Copyright Law:
1. All proprietary rights other than copyright, such as patent rights.
2. The right to grant or refuse permission to third parties to republish all or part of the article or translations thereof. In the case of whole articles, such third parties must obtain Society of Wood Science and Technology written permission as well. However, the Society may grant rights with respect to Journal issues as a whole.
3. The right to use all or part of this article in future works of their own, such as lectures, press releases, reviews, text books, or reprint books.