Upgrade of the Belle II Vertex Detector with Depleted Monolithic Active Pixel Sensors

The Belle II experiment at the SuperKEKB e + e − collider is preparing for an upgrade of its vertex detector to cope with an increased luminosity of up to 6 × 10 35 cm −2 s −1 . The new vertex detector (VTX) will consist of six layers of depleted monolithic active pixel sensors (DMAPS), with a total material budget of about 3% of X 0 . The OBELIX chip, developed for this upgrade, is derived from the TJ-Monopix2 sensor and manufactured using the Tower Semiconductor 180 nm CMOS technology. It features a 33 µ m pixel pitch, time-stamping capability with 50 ns resolution, and a dedicated digital periphery compatible with the Belle II trigger system, supporting rates up to 30 kHz. The sensor is designed to operate under the expected background hit rate at the target luminosity, with high radiation tolerance, up to 5 × 10 14 n eq /cm 2 and 1 MGy, while maintaining a power density in the range of 200-300 mW/cm 2 , corresponding to hit rates from a few MHz/cm 2 up to 120 MHz/cm 2 . This paper presents results from laboratory measurements and beam tests performed on TJ-Monopix2 chips, including both not-irradiated and irradiated devices. Particular focus is given to the performance of irradiated sensors as a function of temperature, a key aspect for defining the maximum allowable operating temperature for OBELIX. These studies provide essential input for the thermal design of the VTX cooling system, especially for the innermost layers where power density and hit rates are highest.

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Journal
EPJ Web of Conferences
Published
2025-01-01
DOI
https://doi.org/10.1051/epjconf/202533801003
Primary Topic
Particle Detector Development and Performance
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article
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article

Upgrade of the Belle II Vertex Detector with Depleted Monolithic Active Pixel Sensors

B. Schwenker, S. Giroletti, Y. Onuki, G. Dujany et al.
EPJ Web of Conferences
Particle Detector Development and Performance
article

Upgrade of the Belle II Vertex Detector with Depleted Monolithic Active Pixel Sensors

B. Schwenker, S. Giroletti, Y. Onuki, G. Dujany, L. Federici, Y. Buch, Ajit Kumar, C. Schwanda, H. Krüger, K. R. Nakamura, T. Higuchi, W. M. Song, C. Lacasta, P. Pangaud, S. Mondal, C. Bespin, J. Gong, L. Massaccesi, Danlin Xu, A. Frey, A. B. Kaliyar, J. Baudot, Y. Peinaud, D. Fougeron, L. Schall, C. Finck, M. Barbero, Franck Morel, M. Bóna, M. Schwickardi, B. Pilsl, G. Rizzo, J. Mazorra de Cos, G. Bertolone, A. Gallas Torreira, T. Kishishita, G. Casarosa, P. Stavroulakis, S. Bettarini, R. Sefri, C. Hu-Guo, P. Breugnon, M. Babeluk, C. Mariñas, T. Hara, M. Minuti, L. Corona, A. Gabrielli, E. Riceputi, C. Irmler, J. Serrano, V. Vobbilisetti, M. Massa, R. Boudagga, D. Howgill, A. J. Bevan, X. Y. Gao, L. Molina Bueno, D. Jeans, H. Pham, L. Gaioni, F. Forti, F. Bosi, A. Fernandez Prieto, F. Bernlochner, I. Ripp-Baudot, Y. Okazaki, G. Traversi, D. Auguste, A. Himmi, M. Karagounis, A. Moggi, J. Bonis, A. Dorokhov, V. Re, Marcus Winter, L. Ratti, M. Vogt, J. Dingfelder, I. Valin, T. Bergauer, Stéphanie Barrillon, M. Maushart, S. Wang
article en

Abstract

The Belle II experiment at the SuperKEKB e + e − collider is preparing for an upgrade of its vertex detector to cope with an increased luminosity of up to 6 × 10 35 cm −2 s −1 . The new vertex detector (VTX) will consist of six layers of depleted monolithic active pixel sensors (DMAPS), with a total material budget of about 3% of X 0 . The OBELIX chip, developed for this upgrade, is derived from the TJ-Monopix2 sensor and manufactured using the Tower Semiconductor 180 nm CMOS technology. It features a 33 µ m pixel pitch, time-stamping capability with 50 ns resolution, and a dedicated digital periphery compatible with the Belle II trigger system, supporting rates up to 30 kHz. The sensor is designed to operate under the expected background hit rate at the target luminosity, with high radiation tolerance, up to 5 × 10 14 n eq /cm 2 and 1 MGy, while maintaining a power density in the range of 200-300 mW/cm 2 , corresponding to hit rates from a few MHz/cm 2 up to 120 MHz/cm 2 . This paper presents results from laboratory measurements and beam tests performed on TJ-Monopix2 chips, including both not-irradiated and irradiated devices. Particular focus is given to the performance of irradiated sensors as a function of temperature, a key aspect for defining the maximum allowable operating temperature for OBELIX. These studies provide essential input for the thermal design of the VTX cooling system, especially for the innermost layers where power density and hit rates are highest.

EPJ Web of ConferencesVol. 338
University of Pisa (IT), University of Bergamo (IT), Centre National de la Recherche Scientifique (FR), University of Bonn (DE), Austrian Academy of Sciences (AT), High Energy Accelerator Research Organization (JP), Dortmund University of Applied Sciences and Arts (DE), Queen Mary University of London (GB), Kavli Institute for the Physics and Mathematics of the Universe (JP), Jilin University (CN), Universidade de Santiago de Compostela (ES), The Graduate University for Advanced Studies, SOKENDAI (JP), Aix-Marseille Université (FR), University of Pavia (IT), Université Paris-Saclay (FR), Institut Pluridisciplinaire Hubert Curien (FR), Centre de physique des particules de Marseille (FR), Instituto de Física Corpuscular (ES), Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (FR), Jilin Medical University (CN), Istituto Nazionale di Fisica Nucleare, Sezione di Pisa (IT), Université de Strasbourg (FR), University of Göttingen (DE), The University of Tokyo (JP)
Ministerio de Ciencia, Innovación y Universidades, European Commission, Generalitat Valenciana, Deutsches Elektronen-Synchrotron
Openalex Percentile: Top 85%
Particle Detector Development and Performance
DOIOpen Access PDFOpenAlex
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