With a newly established multi-anvil press in the Tokyo Institute of Technology, we have carried out a series of melting experiments on peridotite KLB-1 up to 6.5 GPa. Melt fractions of the peridotite were determined in a wide
P-T
range using extensive X -ray mapping analysis of run products by EPMA and a digitalized back-scattered electron image technique. Compositions of partial melts and solid residues were determined in the whole melting range up to 6.5 GPa. Given quantitative information on mantle melting, we discuss conditions of melting of various basalt magmas and the nature of their source materials. Our conclusions are consistent with the hypothesis that typical mid oceanic ridge basalts represent low pressure (
ca
. 1 GPa), low temperature (
T
p
≈ 1300 °C) partial melting products of mantle peridotite. Island arc picritic tholeiites may also be regarded as partial melts of a peridotitic source, at 1-2 GPa pressures and
T
p
ranging from 1400 to 1500 °C. However, proposed primary magmas for Hawaiian tholeiite are difficult to produce by partial melting of typical mantle peridotite at any depth under anhydrous conditions. Source materials for magmas in large hotspots (e.g. Hawaii, Iceland and some continental flood basalts (CFBS)) may be anomalously enriched in FeO and TiO
2
relative to typical upper mantle peridotites such as KLB-1.
Ultra-high short-term frequency stability has been realized in microwave oscillators based on liquid helium cooled sapphire resonators which operate on the same Whispering Gallery mode. Two cryogenic sapphire oscillators were built to evaluate their stability at short averaging times. These oscillators exhibited a fractional frequency stability of 1.1×10-15 at an averaging time of 1 s, which is more than 100 times better than that of a hydrogen maser. For averaging times between 2 and 640 s the measured oscillator fractional frequency instability was below 10-15 with a minimum of 5.5×10-16 at an averaging time of 20 s. The noise floors of the control servos which contribute to the short-term frequency stability are also discussed.
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