The FRATERNISE project (Facility ad elevata accuRAtezza Temporale pEr espeRimeNti di fISicafondamEntale) [1], [2] was born as a result of the previous experiences of INRIM in the metrological characterization and calibration of timing devices used to verify the superluminal properties of neutrinos by the Borexino collaboration (CNGS project, CERN neutrino to Gran Sasso) [3], [4], [5] and in the detection of extended and ultra-high-energy cosmic showers within the EEE project (Extreme Energy Events) [6]. 


The objective of the FRATERNISE project is to establish a permanent facility installed at INRIM dedicated to the metrological characterization and calibration of timing devices for Fundamental Physics experiments and GNSS receivers used in the remote comparison of atomic clocks or time scales. 


In Fundamental Physics experiments (space physics, accelerator physics), time plays a crucial role, allowing the evaluation of the events time-stamping (timing) and their simultaneity, thus enabling deductions about the characteristics of the observed phenomena. Furthermore, it is increasingly necessary to correlate events from experiments that occur over large distances or events measured by different experiments located in distant places investigating similar phenomena. 


The FRATERNISE project contributes to optimizing timing systems for these types of experiments, assessing the possibility of synchronizing them with the Italian atomic reference time scale, UTC(IT). In addition to the permanent facility, implementing "traveling" units with "customized" functional and metrological characteristics is planned to calibrate timing devices that cannot be physically transported to INRIM. One of these units will also be optimized to be used as a traveling calibration station for GNSS systems used in Time Laboratories of National Metrology Institutes (NMI) for the remote comparison of atomic clocks and time scales within the framework of international calibration campaigns organized by BIPM/EURAMET.


The facility will remain operational beyond the project's end to consolidate its purposes and become a practical and functional system for the metrological characterization of timing devices used in Fundamental Physics experiments. To achieve this goal, a survey of the timing needs of the Particle Physics and Astrophysics community has been conducted, through contact with various research groups to identify the main requirements and drivers of the experiments they are engaged in.


Within the FRATERNISE project, three significant case studies have been identified that are fully compatible and functional with the objectives and prospects of the project itself. 



The most significant example of a case study entirely consistent with the FRATERNISE project develops in the frame of a collaboration with MUOGRAPHIX, the University of Tokyo, and the International organization Virtual Muography Institute (VMI), as well as with colleagues affiliated with CERN, INFN (Italian National Institute for Nuclear Physics) and CREF (Enrico Fermi Research Center). In this context, participation occurred in the first experiment of clock synchronization triggered using relativistic muons from cosmic rays induced Extensive Air Showers (EAS) through an experimental measurement system developed at the University of Tokyo [7], [8]. Although still at a preliminary stage, the results show great promise for current and future technological needs and challenges [9], [10], [12].


Further information can be found here: CTS INRIM  | CTS UTokyo 



Following the experience gained over the years in the field of time metrology applied to Fundamental Physics experiments, a second case study began in the frame of the FRATERNISE project. This one aims to study the possibility of realizing a prototype of a next-generation muon detector that is technologically innovative and state-of-the-art in terms of metrological characteristics. The technological innovation primarily focuses on the detection methodology, which utilizes plastic scintillators and new materials, a new generation of Silicon Photomultipliers (SiPMs), and updated and cost-effective electronics management. This approach would help reduce the costs associated with the purchase and maintenance of the detector while improving its robustness, operational reliability, and safety compared to traditional models based on gas mixture flows. Regarding metrological characteristics, the focus will mainly be on an innovative and state-of-the-art timing system, precise orientation relative to the Geographical North, and high-accuracy and precision stabilization of temperature/humidity/pressure within the detector. This case study aims to evaluate the performance of a technologically advanced prototype of muon detectors optimized from a metrological perspective. These detectors can potentially be used in cosmographic, meteorological, and medical physics applications and for monitoring cultural assets or industrial systems. This activity is carried out in collaboration with colleagues affiliated with CERN, INFN, and CREF.



The Global Navigation Satellite Systems (GNSS) are currently the most widely used systems for remotely comparing atomic clocks and time scales. Geodetic receivers and algorithms can achieve synchronization performance with uncertainties on the order of nanoseconds. These state-of-the-art performance levels are fully compatible with the needs of specific Fundamental Physics experiments that require synchronizing their detection devices, mainly when located over extensive areas. However, the high cost of geodetic receivers typically used for timing applications - like the remote comparison of atomic clocks and time scales at NMIs - often makes these technological solutions not appealing and feasible in the context of Fundamental Physics experiments, especially when a large number of such receivers is required.


In this regard, within the FRATERNISE project, research activity has just started in collaboration with other colleagues from INRIM Time Laboratory. The aim is to identify mass-market SWaP (Low-Size, Weight, and Power) GNSS solutions with performance comparable to the above-mentioned top-level receivers or at least suitable for the needs of the Fundamental Physics experiments targeted by the FRATERNISE project [6], [11].


INRIM STAFF


Giancarlo Cerretto, Marco Sellone, Elena Cantoni   |    E-mail: n.surname(at)inrim.it


FUNDINGS 


FRATERNISE project has been funded by Fondazione CRT and Banca d'Italia.


REFERENCES


[1] Il progetto “FRATERNISE”: Facility ad elevata accuRAtezza Temporale pEr espeRimeNti di fISica fondamEntale. In Atti del 108◦ Congresso Nazionale della Società Italiana di Fisica (SIF). Cantoni, E.; Cerretto, G.; Gnesi, I.; Sellone, M.


[2] G. Cerretto, M. Sellone, S. Cavallero. Measuring time to understand the universe. IL NUOVO SAGGIATORE. - ISSN 0393-4578. - 38:2(2022), pp. 53-59.


[3] B. Caccianiga, P. Cavalcante, G. Cerretto, H. Esteban, G. Korga, M. Misiaszek, M. Orsini, M. Pallavicini, V. Pettiti, C. Plantard and A. Razeto. GPS-based CERN-LNGS time link for Borexino. 2012 JINST 7 P08028 (Journal of Instrumentation, I.F. 1.869). August 2012.


[4] P. A. Sanchez et al: Measurement of CNGS muon neutrino speed with Borexino. Preprint submitted to Physics Letter. B (I.F. 3.955), August 2012.


[5] M. Antonello et al: Precision measurement of the neutrino velocity with the ICARUS detector in the CNGS beam. Preprint submitted to JHEP (Journal of High Energy Physics, I.F. 5.375), September 2012.


[6] G. Cerretto, D. Calonico, E. Cantoni, F. Levi, A. Mura, M. Sellone. Extensive cosmic showers detection: the importance of timing and the role of GPS in the EEE experiment. GPS Solutions, Published online: 10 July 2021. 


[7] H.K.M. Tanaka. Cosmic time synchronizer (CTS) for wireless and precise time synchronization using extended air showers. Nature Scientific Reports. 


[8] H.K.M. Tanaka. Cosmic time calibrator for wireless sensor network. Sci Rep 13, 5951 (2023). 


[9] H.K.M. Tanaka, G. Cerretto, I. Gnesi. First experimental results of the cosmic time synchronizer for a wireless, precise, and perpetual time synchronization system, iScience, VOLUME 26, ISSUE 5, 106595, MAY 19, 2023.


[10] G. Cerretto, M. Sellone, E. Cantoni, I. Gnesi. CTS for time metrology: an overview of the current time and frequency metrology best practices and possible perspectives for timing with muons. Presented at Muographers 2022 General Assembly, 2022 December 13-15.


[11] T.T Thai, E. Cantoni, G. Cerretto, F. Fiasca, A. Perucca, M. Sellone, I. Sesia, G.D. Rovera. Characterization of GNSS receivers for timing applications with inaccurate external reference clock or with internal reference. Presented at IEEE IFCS-EFTF 2023,  May 15th-19th, Toyama, Japan.


[12] Tanaka, H.K.M., Bozza, C., Bross, A. et al. Muography. Nat Rev Methods Primers 3, 88 (2023). https://doi.org/10.1038/s43586-023-00270-7.