Gas desorption properties of carbon fiber composite/copper brazed material used for a divertor

Abstract

Gas desorption properties of carbon fiber composite (CFC)/oxygen free copper (OFHC) brazed material used for a divertor were investigated by a technique of thermal desorption spectroscopy (TDS). For the sake of TDS measurement, the brazed component of a flat plate type was cut into small pieces at different positions. Desorbed gas species were very similar for every piece or position. Major desorbed gas species were H 2O, CO, CO 2 and H 2. For the CFC sample, the total amount of desorbed gases in the temperature range from RT to 1073 K was (3–5) × 10 20 molecules/m 2, which was very close to that of purified isotropic graphite (IG-110U). For the OFHC sample, two large desorption peaks were observed in the TDS spectra of CO and CO 2 both at temperatures of about 600 K and 750 K. The total amount of gases desorbed from the OFHC was 2 or 3 times larger than that of the CFC. For the sample containing a brazed part, two characteristic properties were observed, e.g. (1) at low temperature region, both CO and CO 2 were largely desorbed, and (2) at high temperature region, the desorption rate of H 2 increased. The gas desorption quantity of the brazed layer was estimated to be 2 orders of magnitude larger than that of the CFC. Since the fraction of the brazed layer is very small, this contribution to the total desorption of the entire brazed material can be regarded as very small, only several percents.