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The use of the 19F(γ, n)18F, 27Al(γ, x)24Na, 197Au(γ, n)196Au, and 12C(γ, x)7Be reactions as absolute monitors for high-energy, high-intensity bremsstrahlung beams is discussed. The cross sections per equivalent quantum and the absolute cross sections, in the energy range 300–1000 MeV, are reported for these reactions. 19F(γ, n)18F, 27Al(γ, x)24Na, and 12C(γ, x)7Be reactions are proposed as very simple and suitable systems for monitoring purposes.

The (γ, n) cross sections per equivalent quantum of 12C, 103Rh, 127I, 197Au and 238U have been measured with a bremsstrahlung beam of maximum energies in the range 1–5.5 GeV. Within the experimental errors of the activation method, no contribution of photons above 1 GeV was found. This result disagrees with some previous measurements at energies below 1 GeV but agrees with the predicted values obtained from simple theoretical estimates.

GaAs1−xPx was grown by pulling from Ga-rich solutions using the liquid encapsulation method. X-ray analysis and optical measurements performed on the first grown portion of the crystal give a value x=0.3. Electrical measurements showed that the crystal is n-type with carrier concentration N = ∼ 1017 cm−3 and Hall mobilities μH = ∼ 500 cm2 V−1 sec−1 at room temperature.