Novel Toxic Gases as Detection Media in TPCs

Time Projection Chambers (TPCs) use various chemical species as detection media, depending on the specific application, the required sensitivities, and the types of particles being measured.​ Various studies investigate diverse gas species and mixture compositions to optimize the balance between detection efficiency, sensitivity, and energy resolution. Xenon is a critical component of detectors looking for neutrino-less double beta decay due to its desirable chemical properties, making it a high-quality detection medium with low background radiation. However, it is expensive, and the efforts to scale existing xenon detectors to higher masses to meet scientific goals are limited by xenon availability. Therefore, efforts are being made to look for alternative detector media that could offer the same benefits as xenon without the high outlay. We aim to design and build a cylindrical proportional counter that works as a test bed for sulfur and selenium-bearing compounds, like H₂S, C₄H₄Se, H₂Se, and C₄H₄Se that could be used as gain gases in detectors for future double beta decay searches. These gases have been selected as they have been shown to exhibit electropositive behavior in numerical calculations. The proposed setup is unique because it is designed to have highly toxic and corrosive gases mentioned above as its operating media, and it can also operate at elevated temperatures. Calibration would be achieved using an iron-55 X-ray source. Later upgrades to the setup will also enable the determination of drift velocities. These measurements will allow us to determine the mobility of the gas and assess its effectiveness as a drift gas in radiation detection. The detector, flushed with steam and, later, sulfur-based gases, will inform the changes necessary to upgrade the setup to operate on highly toxic selenium-based gases. The results from the runs will be discussed leading up to exploring the prospects of other suitable gas mixtures. The learnings from this project will be applied to further studies on other promising gain gas combinations for future dark matter detection and double beta decay experiments.