The alpha coefficient measurement of synthetic quartz

FTIR measurements using data obtained for different samples, or by using dispersive, or FTIR spectrometers, have been compared. Experimental conditions, such as surrounding humidity, relative positions of samples in the sample compartment, use of limited apertures, and multiple parameters of the FTIR spectrometers, such as resolution, number of scans and the effect of the beamsplitter have been studied. These parameters have then been modified until the conditions of measurement give a good agreement between the alpha values computed from the FTIR spectra and those computed from dispersive spectrometers. A simple translation device is necessary to reduce the time of measurements. It allows the determination of the homogeneity of the Y-cut along the Z-axis as well as along the Y-axis of a bar with steady experimental conditions. After this measurement, alpha-Z values can be calculated. An application of the alpha-Z measurements is given: the comparison of the alpha-Z values between an as-grown bar and an air-swept bar. This measurement is a good way for indicating the modification of the homogeneity induced by the sweeping. These results are compared with laser absorption measurements of crystal defects