Speakers
Description
Thick Gas Electron Multiplier (THGEM) detectors are robust devices which can be manufactured using standard PCB drilling and etching technology, typically on double-clad, insulating materials. These detectors are ideal for cosmic muon tracking in large-area muon imaging/muography applications due to their low-cost, scalable production. Essential requirements for these tracking devices to be used in muography applications include high muon detection efficiency and good position resolution.
We fabricated 4 cm$\times$4 cm and 10 cm$\times$10 cm THGEM prototypes in collaboration with local Indian PCB manufacturers. Through surface polishing and conditioning, we achieved stable operation and high gain in both single and double-layer configurations. A maximum gain of approximately 7000 was achieved in single-layer and 30,000 in double-layer configuration using Ar-CO$_2$ (90:10) gas mixture. The maximum muon detection efficiency of these detectors was found to be 99% in single-layer and 99.5% in double-layer operation. The position resolution of single and double-layer configurations, equipped with a readout plane having strips of width 350 $\mu m$ and pitch 450 $\mu m$, was measured using an $^{55}$Fe source with 2 mm collimator. The source was swept across the detector plane in perpendicular direction of the readout strips using a 3D precision positioning system. A position resolution of 30 $\mu m$ was achieved in both single and double-layer configurations. Furthermore, the impact of operating voltage on position resolution of both the configurations was evaluated for Ar-CO$_2$ and Ar-isobutane gas mixtures.
To verify the accuracy of the position resolution measurement method, experimental data were compared to simulated results, generated in Garfield++ [1]. The simulation incorporated COMSOL Multiphysics [2] for electric field calculations, HEED [3] for primary ionization, and Magboltz [4] for electron transport properties. Numerical simulations and experimental data demonstrate that THGEMs developed in India possess the requisite efficiency and spatial resolution for successful application in muography.
References:
[1] Garfield++ homepage, https://garfieldpp.web.cern.ch/.
[2] COMSOL homepage, https://www.comsol.com/.
[3] I. B. Smirnov, "Modeling of ionization produced by fast charged particles in gases", Nuclear
Instruments and Methods in Physics Research Section A, Volume 554, Issue 3, pp. 474-493, 2005.
[4] S. F. Biagi, Magboltz 11, http://magboltz.web.cern.ch/magboltz.
| Name of the speaker | Saikat Ghosh |
|---|---|
| Eligible for the Georges Charpak Young Scientist Award. | yes |