St. Paul's Cathedral Mission College, popularly known as St. Paul's College, is an undergraduate liberal arts and sciences college in Kolkata, India. Recently, post-graduate in English literature has been introduced. It is affiliated with the University of Calcutta. It not only boasts of its academic excellence and cordial teacher-student relationship, but also has an eco-friendly campus and quiet surroundings. The college today offers a proper ambience to the students of all religions and creed for full-fledged development of their potentialities. The college is recognized by the University Grants Commission (UGC). Recently, it has been re-accredited and awarded 'B' grade by the National Assessment and Accreditation Council (NAAC).
Radial asymmetry in a quadrupole mass filter (QMF), introduced by symmetric displacement of a diagonally opposite rod pair, modifies the confinement potential and alters the ion stability characteristics. In this work, the influence of such radial asymmetry on QMF operation in the second stability zone is investigated through simulations. Using an existing potential formulation for a radially asymmetric QMF, the stability diagram in the second stability zone is extracted for the first time, revealing a systematic shift of the stability apex with the asymmetry parameter. Radial asymmetry introduces additional multipole components, notably an octupole term whose magnitude scales with the asymmetry parameter and whose sign depends on the DC polarity applied to the displaced rods. Transmission simulations show that the transmission peak shifts in accordance with the displaced stability apex, while the resolution exhibits a strong dependence on both the asymmetry parameter and the DC polarity, enabling resolution enhancement under optimized conditions. Comparable resolution enhancement is obtained for inward and outward displacements under suitable polarity configurations, with outward displacement providing higher transmission efficiency due to an increased effective aperture. The role of DC polarity in a given radially asymmetric design is analyzed through SIMION-based stability diagram simulations. Collectively, the results demonstrate that radial asymmetry can be leveraged to systematically influence resolution and transmission behavior in QMFs operating in the second stability zone.
Geometrical imperfections in quadrupole mass filters introduce higher-order field components that can significantly influence device performance, particularly under non-sinusoidal excitation. In this work, a comprehensive simulation study is carried out to investigate the effect of geometrical imperfections on the performance of a rectangular wave driven quadrupole mass filter operating in the first stability zone. Radial field distortions arising from controlled variations in rod geometry and position, including single rod radius variation, single rod displacement, diagonal rod radius variation, and diagonal rod displacement, are examined. These imperfections introduce octupole field components that distort the ideal quadrupolar field distribution. The influence of such distortions on key performance parameters, namely mass resolution and ion transmission efficiency, is systematically evaluated. The results show that the presence of radial asymmetry leads to a degradation of both resolution and transmission efficiency in all cases considered. Furthermore, the study reveals a strong dependence of mass filter performance on the initial state of the applied pulsed waveform, specifically whether the asymmetric rod pair is subjected to the high or low level of the RF pulse. These findings provide important insights into the tolerance limits of geometrical imperfections and their impact on the performance of pulsed wave driven quadrupole mass filters, which are relevant for the design and optimization of high-resolution digital mass filtering systems.
The phenomenon of vanishingly small scattering cross-section of low-energy electron beam in noble gases like argon and xenon, commonly known as the Ramsauer-Townsend effect, can be explained by the method of partial cross-sections. In this article, the Coulomb potential inside noble gas atoms is modeled as a rectangular well potential, and the resonant transmission of a low-energy electron beam through the well is studied quantitatively and systematically. The approach provides a satisfactory explanation of the Ramsauer-Townsend effect and is within the reach of an undergraduate audience.
The performance of a quadrupole mass filter (QMF) is highly sensitive to deviations from ideal electrode geometry. In this work, we investigate the effect of small inward and outward tilting of cylindrical rods on the resolving power and transmission characteristics of a QMF. Such geometric perturbations introduce an axial variation in the radial confinement potential, resulting in Mathieu parameters that vary along the ion trajectory. To examine this effect, the ion stability diagram is computed using a Runge-Kutta (RK45) method with axially-varying Mathieu parameters. The modified stability region exhibits shift and contraction depending on the magnitude and nature of rod inclination. The evolution of higher-order field components, particularly the dodecapole term, is analyzed along the axial direction. Ion trajectory simulations are performed using SIMION to evaluate the corresponding changes in QMF transmission characteristics in the first stability zone of operation. While simulations at fixed operating conditions indicate a transmission-resolution trade-off at small tilting angles leading to an apparent enhancement in resolving power, analysis at constant peak transmission reveals that even slight deviations from the parallel configuration degrade the overall resolving power. These results highlight the critical role of minute geometric imperfections in QMF operation and provide insights into tolerance limits and design optimization for improved mass filter performance.
NiO included ZnO nanocomposite gas sensors were studied in this work. The devices were characterized to detect hazardous gases like SO_2 and NH_3 at room temperature. Two devices were prepared using ZnO nanocomposites modified by 5 wt NiO ( Zn1 ) and 15wt NiO nano inclusions ( Zn2 ). Both devices show strong responses towards NH_3 and almost no response towards SO_2 gas. The sensitivity is found to be ∼55 % and ∼ 80 % for Zn1 and Zn2 device respectively for NH_3 . Materials are characterized and response curves were analyzed to identify the response parameters by fitting an appropriate mathematical function. The parameter τ indicate that Zn2 ( τ∼ 4 s ) responses faster than Zn2 ( τ∼ 9.5 s ) towards NH_3 gas.The cross-correlation factors between different responses of the devices toward target gases at different concentrations are calculated. These mathematical methods are used as calibrating tools for the devices to improve detection process for target gases with particular concentrations.
