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ISSN 1748-0221 23:58 - Friday, 19 June 2026 |
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JINST Instrumentation Theses Archive
2026 JINST TH 003
Ph.d. degree
Novosibirsk State University, Russia
Vijayanand Kuttikattu Vadakeppattu
Supervisor: Prof. Andrey Sokolov
Keywords:
- Gaseous detectors
- Micropattern gaseous detectors
- Time projection Chambers (TPC)
Abstract:
The Budker Institute of Nuclear Physics is developing a Super Charm-Tau Factory (SCTF) project which consists of a collider with energy 2-5 GeV and luminosity 1035 cm−2s−1. The project aims to study the effect of CP-violation in the decay of charmed particles, test the standard model in the decay of tau lepton, and search and study entirely new forms of matter: glueballs, hybrids, etc. The main features of the Super Charm-Tau Factory are a wide range of energies, high luminosity, and the possibility of conducting experiments with longitudinally polarized electron beams. The physics program of SCTF requires a universal magnetic detector with a field of about 1.5T. The Super Charm-Tau Detector (SCTD) system is a combination of several detectors. The inner tracker is placed immediately after the vacuum pipe to measure the secondary vertices of the decay of short-lived particles. The inner tracker is followed by the drift chamber, which is the main tracking and momentum-measuring detector. The particle identification system will be placed after the drift chamber and a high-resolution electromagnetic calorimeter is placed to detect the neutral particles. A nine-layered muon detector is placed after the calorimeter to separate muons from hadrons. The main goal of our work are:- Develop a simulation package in the aurora framework for the Time Projection Chamber (TPC) as the inner tracker.
- Optimize the thickness of TPC to make it possible for soft pions to cross the TPC wall.
- Select a suitable gas mixture for TPC as a drift medium to achieve transverse resolution less than 200 m. The drift velocity of electrons in the medium should be not less than 5 cm/𝜇s. To minimize the complexity of the field cage, the applied electric field is limited to a range of 100 and 1000 V/cm.
- Conduct a simulation study to minimize the Ion Backflow (IBF), which can distort the applied electric field. The proposed electric field for this simulation is 50 kV/cm.
- Build a simulation package to understand the real-time detector response.
The above-mentioned goals have a significant impact on the performance of the TPC thus on the inner tracker. The main new results obtained during our study are following:
Study of transport properties of electrons in various gas mixtures: Choosing a gas mixture for TPC was one of our main objectives. We did a simulation study with both argon and neon-based gas mixtures to choose a suitable gas mixture as the drift medium of TPC. The study is important as the performance of the TPC depends on the drift. Our study found that argon as a primary gas in the gas mixture as electrons can achieve high drift velocity with reasonable diffusion in the electric field range of 100 to 1000 V/cm.
Study of spatial resolution to finalize gas mixture: Our detailed simulation study using the charge centroid method to find the transverse resolution and total resolution in 200 and 500 V/cm with more than 20 argon based gas mixtures shows that many gas mixtures, especially with CH4 and CF4, can provide resolution below 200 𝜇m. However, the size of the readout pad should be less than 1 mm which may increase the budget. Our study found that two gas mixtures, namely argon with 50% CF4 and argon with 40%CF4 and 15% CH4 meet all the requirements of the inner tracker.
Study of ion backflow (IBF): We did a study to calculate the ratio of ions moving back to the drift volume. The study was done with the applied electric field range in the GEM holes of 10kV/cm to 100 kV/cm and we used two types of Gas Electron Multiplier (GEM) stacks. The first one is the standard GEM and the second GEM is a special GEM with a pitch two times larger than that of the standard GEM. In the first simulation, we used a triple GEM made of standard GEMs. In the second case, we replaced the middle GEM with the special GEM and compared the result with that of the first study. The comparison proved that using a triple GEM with two standard GEM stacks and a special GEM stack in the middle will reduce the IBF. Our study found that the triple GEM as a combination of standard and special GEM will help to reduce the IBF hence proposed the same as the readout system.
The results of this work provide a robust foundation for the design and construction< of the SCTF TPC. The optimized gas mixture and GEM configuration are expected to deliver exceptional performance in terms of spatial resolution, ion backflow, and overall tracking efficiency. These findings constitute a significant step towards realizing the scientific goals of the SCTF experiment.