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Mass Fractionation behaviour of U isotopes during Thermal Ionization, the potential for mass fractionation correction using double spike
Introduction Until recently it was assumed that the terrestrial 235U/238U was 137.88. However high precision 235U/238U measurements using ICP multi collector mass spectrometers1 as well as double spiked TIMS have shown small variations in 235U/238U at the 1- 2 per mil level. In uranium ores these variations are possibly due to changes in environmental redux…
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High precision Os isotope ratio measurements using Phoenix X62 TIMS
Introduction The study of Osmium isotopes is an important tool in geochemistry and cosmochemistry (e.g. Shirey and Walker 1998, Brandon et al. 2006, Ravizza and Turekian 1992). Side box 1 provides background on the two Os isotope systems of interest. Whilst 187Os/188Os ratios can vary by several percent, the variation in 186Os/188Os is far smaller…
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Noble Gas Mass Spectrometer Electronics upgrade package
Noble gas mass spectrometers are built to last. There are no moving parts and the vacuum envelope will become cleaner with time as the instrument is periodically baked. However, the electronics and software on the instrument will become dated, unreliable and unsupported by instrument manufacturers. For the user the only option would be to buy…
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Multidynamic measurement of small Neodymium (Nd+) ion signals on Faradays using Xact amplifiers with 1e11 Ω and 1e12 Ω (1T) resistors
Introduction Thermal Ionization Mass Spectrometry is an extremely sensitive detection technique. For Neodymium, measured as Nd+ , ion yields of 1 ion per 50 atoms loaded are typical for triple filament geometries on a Phoenix TIMS. This efficiency is of huge importance for applications where there is very little sample material e.g. garnet growth rims…
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An assessment of the linearity of the ion-counting Daly detector and Hamamatsu photomultiplier using NBS U500
Zenon Palacz, IsotopX Ltd, Middlewich, Cheshire, UK The Daly detector was designed by N.R Daly in the 1960s. The design uses a conversion dynode to convert incident ions into electrons. It also separates the multiplication electronics away from the ion beam preventing secondary ion production on the multiplication dynodes. The conversion surface is a highly…
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Noise Characteristics of Phoenix TIMS Xact Faraday Detectors with 1 x 10e11 ohm resistors
Introduction High precision isotope ratios require an optimal signal to noise ratio. Here we assess the electronic noise of the new Xact Faraday detectors on Phoenix TIMS using a range of different integration times and compare the results to the theoretical noise calculated from the Johnson law. Experimental Phoenix has nine Faraday collectors each directly…
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Multidynamic measurement of small Neodymium (Nd+) ion signals on Faradays using Xact amplifiers with 1e11 Ω and 1e12 Ω (1T) resistors
Zenon Palacz, Davydd Wanless, Ian Turner & Tony Jones. Isotopx Ltd. UK Introduction Thermal Ionization Mass Spectrometry is an extremely sensitive detection technique. For Neodymium, measured as Nd+ , ion yields of 1 ion per 50 atoms loaded are typical for triple filament geometries on a Phoenix TIMS. This efficiency is of huge importance for…