A newly designed and constructed experimental apparatus for vaporization and condensation of minerals in the solar nebula.

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Condensation of mineral grains from gas at high temperatures took place in the primodial solar nebula, and solid planets, such as the earth, and meteorites were formed by accretion of these grains. It is considered that solid-liquid reactions, such as vaporization and condensation, played an important role in chemical and mineralogical fractionation in the nebula. Irrespective of the significance of the reactions, however, little experimental work has been done especially on condendsation.In the present research project, an experimental system was successively established to study vaporization and condensation of minerals near the primodial solar conditions. In the first year, a vacuum furnace for vaporization and condensation (AYUMI EC300) was made and calibrated. At the beginning, accidents happened usually in a heater part, Hich was specially designed for heating a large sample chamber. In the second year, the heater part was improved and fixed, and several results were obtained from experiments by using this furnace.The experiments were carried out in the system Mg_2 SiO_4 -H_2 , Hich mimics the solar composition. Conditions for the condensation were determined, and it was concluded that the condensation is controlled mainly by temperature and forsterite whiskers can grow by the VLS mechanism. Large amounts of samples can be treated in tghis furnace, and this makes it very easy to charzacterize the samples by SEM, TEM, and XRD. Moreover, the compositions of trace elements and isotopes will be easily determined from large amounts of samples. Further studies using this experimental system will contribute to further understanding of the primodial solar system.