Ultra Low Noise Multiple Isotopx Ion Counting (IIC) and Faraday Detectors on Phoenix TIMS

When measuring very small ion signals (<10,000cps), in sub picogram samples of actinides, ion counting detectors are necessary due to their low noise compared to that of a Faraday detector. Ion counters however, still have a non-zero noise associated with them, known as the dark noise, which is typically several counts per minute (CPM). Additionally, there are sources of measurement error present that are not of concern with Faraday detectors, such as deadtime/linearity, peak flatness, and gain stability.

The challenge in determining the relative gain of an ion counter, presents a significant challenge in acquiring high quality data at low count rates.

In this application brief, the performance characteristics of an Isotopx Phoenix equipped with 10 channels of upgraded Isotopx Ion Counting (IIC) power supply and counting electronics is evaluated. The ion counters are conversion dynode multipliers, whereby the ion beam strikes a conversion dynode, and the released electrons are detected using a Sjuts multiplier aligned at 90o relative to the ion beam.

This design allows the simultaneous measurement of actinides at unit mass spacing with no intermediate attached Faraday collectors. In addition the multipliers are independently movable relative to each other, so the same collector array can measure for example U and Pu isotopes as well as Nd, Pb or Os isotopes by adjusting the separation of the ion counters relative to each other.

This instrument is also equipped with a Zeptona Faraday detector which is an enhanced (lower noise) version of the ultra low noise ATONA® amplifier. The Zeptona allows calibration of multiplier gain relative to a Faraday collector at count rates of <~10,000cps which is an ion signal too low for most resistor-based Faraday collectors.

Technical Note 2021

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Category: Uncategorized, Geology, Product News, Applications, Publications
Published: Friday, July 23rd, 2021 at 10:52 am

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