Penetration Depth Of Electrons Research Articles

The response of photographic emulsions to electrons in the energy range 7-60 kev.

The large-area responses of ten emulsions (five `conventional', three nuclear research and two Schumann-type) have been examined for electron energies between 7 and 60 kev. The responses are considered in terms of the initial slope of the optical density D-exposure E curve, the value of E for D = 1, the saturation density Ds and the number of grains rendered developable per incident electron. For high D/Ds values, the forms of the experimental (D, E) relationships are found to depart from those expected if the mechanism of rendering developable a photographic grain were a simple single hit process, in a way that depends on the electron energy. The effect on the single hit relationship of the dependence of the exposure on the depth of electron penetration is considered, allowing a more complete inter-pretation of the shape of the (D, E) curves in terms of simple descriptions of electron-grain interactions. The high sensitivities of the nuclear and Schumann emulsions make feasible the direct recording at useful magnifications of electron images formed by low energy electrons.

Messung der Eindringtiefe von Elektronen und Ionen in d�nnen Aufdampfschichten

The penetration depth of electrons, H+-, He+-, Ne+-, and Ar+-ions in thin evaporated layers of alkali fluorides and alkaline earth fluorides has been investigated by measuring the excitation and deterioration of the luminescence caused by the bombardement with electrons and ions. Particle energy ranged up to 10 keV for electrons and the lighter ions and up to 30keV for the heavier ions; film thicknesses were chosen between 5 and 100μg/cm2. The penetration depths defined by the two different techniques are called “maximum excitation depth” and “maximum deterioration depth”. By measuring the excitation depth a depth distribution may be obtained. Using the Bethe-equation a numerical penetration depth-energy-relation for electrons was derived which gives good agreement with the experimental values. The results of the deterioration depths of the ions are compared with the theoretical predictions ofLindhard andScharff.

Heating effect of an electron beam impinging on a solid surface, allowing for penetration

The heating effect of an electron beam, under the assumption that the entire beam energy is imparted to the target surface (disc heating model), can be calculated fairly readily. At the high voltages and small beam diameters employed in electron-beam machining, however, the problem is complicated by penetration of electrons into the target. This effect is allowed for by a simple model of electron penetration due to Archard,9 by which the spatial distribution of power dissipation in the target is computed. The steady-state heat-flow problem is solved by relaxation.Results obtained on a digital computer, for a range of target materials and beam voltages, are resolved into two curves, from which correction factors for the effects of backscatterand electron-penetration depth can be read and applied to the data given by the disc heating model. Graphs are presented showing the maximum temperatures obtainable, with spots of given sizes, for a range of materials and voltages. The computations are substantially verified by experiment.

Blasenkammerexperimente zur Abbremsung relativistischer Elektronen

The complete slowing down of electrons with initial energies up to 20 MeV in several materials was investigated with the aid of a bubble chamber. The real path lengths and penetration depths of electrons were evaluated; the distribution of these and some other derived quantities are given and discussed. The distributions of the path lengths—which are essentially influenced by energy loss due to bremsstrahlung — are in good agreement with a theory of BLUNCK.

Localization of β-Galactosidase in Cells of Escherichia coli by Low Voltage Electron Bombardment

By using low voltage electrons to bombard dried cells of Escherichia coli, the inactivation of the enzyme beta-galactosidase as a function of depth of electron penetration has been studied. There is little inactivation for a penetration of 100 A, but considerable for a penetration of 300 A. An analysis of the data for six initial electron energies shows that there exist outer and inner bounds of the enzyme region which are approximately 300 and 700 A below the cell surface, respectively.