N2Sense for Interference-Free Ultra-Trace Measurement of Nitrogen in Argon and Helium The new reference for continuous nitrogen analysis Date: May 2023 Authors: Marc-Antoine Langevin, Ph.D. André Lamontagne, Ing. Yves Gamache, CEO, CTO

A B S T RACT Continuous measurement of ultra-trace level nitrogen in UHP argon and helium is a key application that requires highly sensitive and accurate instrumentation, especially in the semiconductor and air separation industries. 30 years ago, Yves Gamache, CEO of ASDevices, introduced the first plasma-based trace N2 in argon analyzer named K2001, which was considered as a standard in the industry. In 2017, ASDevices released new technologies, including the enhanced plasma discharge (Epd), an improved plasma-based detection technology that is now used in the N2Sense, leading to unprecedented...

plasma discharge technology. Plasma discharges are highly reactive and impurities can lead to unexpected chemical reactions that might have negative effects on the system performance. The Enhanced Plasma Discharge (Epd) technology, which is used in the N2Sense, is capable of ‘’spectral compensation’’, a unique feature that prevents such interference. More details about this feature will be presented below. Sources of moisture contamination When monitoring argon coming directly from an air separation process, the level of moisture is well below 1 ppm and will generally not interfere with the N2...

Moisture line cluster 0.1 ppm H2O added Figure 1 – Plasma baseline (Bremsstrahlung) offset due to various amounts of moisture [4] Figure 2 – Effect of moisture on N2 response [4] Technology Overview and Performance N2Sense Platform The N2Sense analyzer is presented in Figure 3. Thanks to the most recent developments in electronics miniaturization that were implemented, the N2Sense is the most compact continuous nitrogen analyzer currenwtly available on the market. Furthermore, the large display screen and latest software interface were optimized to improve conviviality for the user. When measuring...

are active components that are susceptible to leaks, which can affect the baseline noise and lead to false readings. With its purge design, ambient air can’t leak into the sample line through the EPC. Other N2 sensing technologies use unpurged EPC, which has a significant negative impact on their performance. As the world leader in continuous N2 measurement in argon and helium, we also patented a method to avoid interference from moisture. This method combines the use of a moisture trap, placed before the sample inlet of the analyzer, with a moisture permeation tube to dope the plasma with a...

Plasma discharge Data acquisition Plasma discharge Synchronous measurement with over sampling and phase shift processing algorithm Advanced signal processing unit with spectral compensation Plasma discharge Electrodes Plasma discharge Electrodes EPD Plasma source power supply Plasma source power supply Feedback algorithm Figure 8 – Traditional plasma emission detector Figure 9 – Enhanced Plasma Emission detector with feedback algorithm Despite these features, as discussed previously, the introduction of impurities in the plasma could still cause variations in the Bremsstrahlung and therefore...

This might seem in contradiction with the results presented in Figure 2 since moisture should lower the N2 signal. However, as presented in Figure 1, moisture also causes a Bremsstrahlung offset that can be wrongfully measured as N2 increases. Thanks to spectral compensation, this baseline variation on the N2 signal is canceled, leading to more accurate measurements. Other impurities such as oxygen, methane and hydrogen can cause similar positive or negative baseline offsets that can be canceled using spectral compensation. Another demonstration of the power of spectral compensation is presented...

Finally, the step-response of the N2Sense was evaluated. A sample containing initially 4 ppb N2 in helium was measured. Then, every 30 seconds, the N2 concentration was increased by 1 ppb. The results are presented in Figure 15. Figure 14 – N2Sense response time Figure 15 – N2Sense 1 ppb step response Conclusions In conclusion, the N2Sense benefits from over 30 years of development and expertise in the field of ultra-trace analysis. With the recent introduction of the Epd technology, unprecedented limits of detection of >1 ppb can now be reached for continuous N2 measurement in argon and helium....