Hydrogen analysis for geological samples by using high energy proton beam

岩浆样品的氢分析对研究岩浆的发育和动力学具有重要意义。在岩浆样品中发现的熔融包裹体被认为是被晶体捕获的熔融岩浆的标本。为了分析典型的百微米大小的熔体夹杂物，我们研制了20 MeV质子束微束辐照系统。为了分析地质样品中的氢，利用两个带电粒子探测器在相对于束轴45度的位置上，建立了质子-质子弹性反冲符合谱法（ERCS）。符合测量是检测样品中氢和推断氢深度剖面的有效方法。通过使用Ti(H)（NIST）、Mylar、Kapton、聚乙烯薄膜对氢浓度的校准，估计氢测量的系统误差小于5%。氢的测定下限为1ppm， 20ng/cm2。对恩达、初崎、细寿、大井、高鲁库、石久保、荒游、小关、坂坂、小大阪、Inariyama和Muroo等地的熔体包裹体进行了辐照分析。分析了来自Chichi岛的安山岩和夏威夷岛的橄榄石。对Hyatogawa， Kamisano和Mitsugozawa的透辉石铬进行了分析。Wadatoge黑曜石的测量结果为1.0 wt. % (H2O)，与卡尔-费雪测量结果一致。

Hydrogen analysis for magmatic samples is quite important to investigate development and dynamics of magma. Melt inclusions found in the magmatic samples are considered to be specimen of melting magma trapped by the crystal. In order to analyze the melt inclusions which are typically hundred micro meters, we have developed micro beam irradiation system with 20 MeV proton beam.For the hydrogen analysis in the geological samples, proton-proton elastic recoil coincidence spectrometry (ERCS) has been developed by using two charged particle detectors located at 45 degree with respect to the beam axis. The coincidence measurement is effective to detect hydrogen in the samples and to deduce hydrogen depth profile.From calibration of the hydrogen concentration using Ti(H)(NIST), Mylar, Kapton, Polyethylene films, systematic error of the hydrogen measurement has been estimated to be less than 5 percent. Lower limit of the hydrogen determination is 1ppm and 20ng/cm2.Melt inclusions gathered from Enda, Hatsuzaki, Hosoo, Tatekui, Gouroku, Kashiwakubo, Arayu, Koseki, Sakkabira, Konosaka, Inariyama and Muroo have been irradiated and analyzed. Andesite from Chichi Isle and olivine from Hawaii Isle have been analyzed. Chromium diopside from Hyatogawa, Kamisano and Mitsugozawa have been analyzed. A measured result of obsidian from Wadatoge is 1.0 wt. % (H2O) which agrees with a Karl-Fisher measurement.