The OBELIX chip for the Belle II VTX upgrade Babeluk, M.; Auguste, D.; Barbero, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
October 2024, Volume:
1067
Journal Article
Peer reviewed
The OBELIX depleted monolithic active CMOS pixel sensor (DMAPS) is currently developed for the upgrade of the vertex detector of the Belle II experiment located at Tsukuba/Japan. The pixel matrix of ...OBELIX is inherited from the TJ-Monopix2 chip, but the periphery includes additional features to improve performance and allow the integration into a larger detector system. The new features include a trigger unit to process trigger signals, a precision timing module and a possibility to transmit low granularity hit information with low latency to contribute to the Belle II trigger. Additionally, low dropout voltage regulators and an ADC to monitor power consumption and substrate temperature is developed. This paper will focus on the trigger contribution capabilities of the OBELIX chip.
The DMAPS upgrade of the Belle II vertex detector Babeluk, M.; Barbero, M.; Baudot, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2024, Volume:
1064
Journal Article
Peer reviewed
The Belle II experiment at KEK in Japan considers an upgrade for the vertex detector system in line with the accelerator upgrade for higher luminosity at long shutdown 2 planned for 2028.
One ...proposal for the upgrade of the vertex detector called VTX aims to improve background robustness and reduce occupancy using small and fast pixels. VTX accommodates the OBELIX depleted monolithic active CMOS pixel sensor (DMAPS) on all five proposed layers. OBELIX is specifically developed for the VTX application and based on the TJ-Monopix2 chip initially developed to meet the requirements of the outer layers of the ATLAS inner tracker (ITk).
This paper will review recent tests of the TJ-Monopix2 chip as well as various design aspects of the OBELIX-1 chip currently under development.
CMOS MAPS upgrade for the Belle II Vertex Detector Babeluk, M.; Barbero, M.; Baudot, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2023, Volume:
1048
Journal Article
Peer reviewed
Open access
The success of the Belle II experiment in Japan relies on the very high instantaneous luminosity, close to 6×1035 cm−2 s−1, expected from the SuperKEKB collider. The corresponding beam conditions at ...such luminosity levels generate large rates of background particles and creates stringent constraints on the vertex detector, adding to the physics requirements. Current prospects for the occupancy rates in the present vertex detector (VXD) at full luminosity fall close to the acceptable limits and bear large uncertainties. In this context, the Belle II collaboration is considering the possibility to install an upgraded VXD system around 2027 to provide a sufficient safety margin with respect to the expected background rate and possibly enhance tracking and vertexing performance.
The VTX collaboration has started the design of a fully pixelated VXD, called VTX, based on fast and highly granular Depleted Monolithic Active Pixel Sensors (DMAPS) integrated on light support structures.
The two main technical features of the VTX proposal are the usage of a single sensor type over all the layers of the system and the overall material budget below 2% of radiation length, compared to the current VXD which has two different sensor technologies and about 3% of radiation length. A dedicated sensor (OBELIX), taylored to the specific needs of Belle II, is under development, evolving from the existing TJ-Monopix2 sensor. The time-stamping precision below 100 ns will allow all VTX layers to take part in the track finding strategy contrary to the current situation. The first two detection layers are designed according to a self-supported all-silicon ladder concept, where 4 contiguous sensors are diced out of a wafer, thinned and interconnected with post-processed redistribution layers. The outermost detection layers follow a more conventional approach with a cold plate and carbon fibre support structure, and light flex cables interconnecting the sensors.
This document will review the context, technical details and development status of the proposed Belle II VTX.
A neural network for beam background decomposition in Belle II at SuperKEKB Schwenker, B.; Herzberg, L.; Buch, Y. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
April 2023, 2023-04-00, 2023-04-01, Volume:
1049, Issue:
C
Journal Article
Peer reviewed
Open access
We describe a neural network for predicting the background hit rate in the Belle II detector produced by the SuperKEKB electron–positron collider. The neural network, BGNet, learns to predict the ...individual contributions of different physical background sources, such as beam-gas scattering or continuous top-up injections into the collider, to Belle II sub-detector rates. The samples for learning are archived 1Hz time series of diagnostic variables from the SuperKEKB collider subsystems and measured hit rates of Belle II used as regression targets. We test the learned model by predicting detector hit rates on archived data from different run periods not used during training. We show that a feature attribution method can help interpret the source of changes in the background level over time.
Track finding at Belle II Bertacchi, Valerio; Bilka, Tadeas; Braun, Nils ...
Computer physics communications,
02/2021, Volume:
259
Journal Article
Peer reviewed
Open access
This paper describes the track-finding algorithm that is used for event reconstruction in the Belle II experiment operating at the SuperKEKB B-factory in Tsukuba, Japan. The algorithm is designed to ...balance the requirements of a high efficiency to find charged particles with a good track parameter resolution, a low rate of spurious tracks, and a reasonable demand on CPU resources. The software is implemented in a flexible, modular manner and employs a diverse selection of global and local track-finding algorithms to achieve an optimal performance.
The Belle II experiment searches for beyond-the-standard-model physics using the Belle II detector and SuperKEKB collider. The silicon vertex detector (SVD) is crucial for particle tracking. After ...the 1.5-year shutdown from June 2022, Run 2 began in January 2024; Run 2 operation shows stable noise levels, high signal-to-noise ratios, and hit efficiency over 99%. To manage higher beam background from increased luminosity, new techniques such as hit-time selection and cluster grouping are being developed. These methods increase the acceptable level of occupancy by distinguishing hits from triggered collisions and other sources.
The Belle II Core Software Kuhr, T.; Pulvermacher, C.; Ritter, M. ...
Computing and software for big science,
12/2019, Volume:
3, Issue:
1
Journal Article
Open access
Modern high-energy physics (HEP) enterprises, such as the Belle II experiment (Abe et al, Belle II Technical Design Report. KEK Report 2010-1,
2010
; Kou et al, The Belle II Physics book. KEK ...Preprint 2018-27,
2018
) at the KEK laboratory in Japan, create huge amounts of data. Sophisticated algorithms for simulation, reconstruction, visualization, and analysis are required to fully exploit the potential of these data. We describe the core components of the Belle II software that provide the foundation for the development of complex algorithms and their efficient application on large data sets.
For the Belle II experiment at KEK (Tsukuba, Japan) the KEKB accelerator was upgraded to deliver a 40 times larger instantaneous luminosity than before, which requires an increased radiation hardness ...of the detector components. As the innermost part of the Belle II detector, the pixel detector (PXD), based on DEPFET (DEpleted P-channel Field Effect Transistor) technology, is most exposed to radiation from the accelerator. An irradiation campaign was performed to verify that the PXD can cope with the expected amount of radiation. We present the results of this measurement campaign in which an X-ray machine was used to irradiate a single PXD half-ladder to a total dose of 266kGy. The half-ladder is from the same batch as the half-ladders used for Belle II. According to simulations, the total accumulated dose corresponds to 7–10 years of Belle II operation. While individual components have been irradiated before, this campaign is the first full system irradiation. We discuss the effects on the DEPFET sensors, as well as the performance of the front-end electronics. In addition, we present efficiency studies of the half-ladder from beam tests performed before and after the irradiation.
Belle II detector upgrade is being discussed aiming to collect five times larger integrated luminosity of 250 ab−1. The beam background level is expected five times higher than current design, thus a ...new pixel vertex detector with faster readout should be developed. We have invented a new pixel detector concept DuTiP for the Belle II upgrade which can be also used for the International Linear Collider (ILC) with small modifications. To realize the DuTiP concept, an SOI technology is chosen as a baseline with a pixel size of 35μm×35μm. The DuTiP concept and its application to a monolithic pixel detector in an SOI technology are explained.
Run and slow control system of the Belle II silicon vertex detector Irmler, C.; Aihara, H.; Aziz, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Volume:
958
Journal Article
Peer reviewed
Open access
The Belle II Silicon Vertex Detector (SVD) was installed recently and has been prepared for physics run at SuperKEKB factory, Tsukuba, Japan. For a reliable operation and data taking of the SVD, a ...sophisticated and robust run and slow control system has been implemented, which utilizes the Experimental Physics and Industrial Control System (EPICS) framework. EPICS uses client/server and publish/subscribe techniques to communicate between the various sub-systems and computers. The information exchange between the different pieces of software and computers is done by process variables (PVs). These PVs are provided by input/output controllers (IOCs), which communicate and interface with the hardware components. The Belle II SVD slow and run control comprises five groups of subsystems, which are SVD DAQ controller, Flash ADC controller, environmental monitors and interlocks, power supplies and EPICS infrastructure services. In this paper we describe the tasks and the implementation of the individual sub-systems, the interaction between them and the global Belle II run and slow control as well as the first experience from commissioning and initial operation of the SuperKEKB accelerator.
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