515664 research outputs found
Sort by
14th White Rabbit Workshop
No full textREFIMEVE is a French national research infrastructure, officially recognized in 2021, based
on a fiber-optic network that disseminates ultra-stable time and frequency signals over long
distances. Reference signals originate at LTE (former SYRTE) at Paris Observatory and are
primarily transported over the optical fibre network backbone of RENATER [1]. It currently
connects more than 20 research laboratories across metropolitan France, with a goal to reach over 40 in the next five years. The network also extends internationally through four cross-border links.
Within the T-REFIMEVE project, we aim to establish a national-scale White Rabbit (WR)
timing network, targeting time accuracy better than 10 nanoseconds across more than 80 nodes interconnected by over 5,000 km of optical fiber. Unlike the bidirectional optical carrier used in the REFIMEVE infrastructure, this deployment leverages the unidirectional optical
amplifiers of the RENATER backbone. WR signals are transmitted as alien wavelengths using standard xWDM technology, which introduces the challenge of mitigating optical path
asymmetries inherent in unidirectional links.
A critical first step toward achieving this level of timing precision is the precise calibration of
instrumental delays in the White Rabbit Switches (WRS). This work reports on the calibration of instrumental delays of dozens of WRS units.
We performed the calibration according to the CERN procedure [2] and the EMPIR/VSL good practice guide [3], for unidirectional links, using SFP transceivers operating at a wavelength of 1560.61 nm. We defined port 1 of one of our WRS to be our golden calibrator, while choosing to leave its ingress and egress delays at their default firmware values, and then used it to calibrate port 1 of another WRS, thus constituting the usual pair of reference ports in a slightly unusual way. We then used these two ports to calibrate all other WRS ports. As expected the synchronisation was already good using the default delays, with offsets of up to approximately 300 ps, and improved to within ±20 ps after calibration. (All of the presented measurements used the same slave port, which had been previously calibrated to the golden calibrator.)
We review the sources of uncertainty in our calibration process and present a preliminary
uncertainty budget.
Finally, we briefly report on the in-field implementation of White Rabbit within REFIMEVE
and discuss the estimation of asymmetric delays introduced by various components of the
active network-such as amplifiers, attenuators, multiplexers, and fiber length differences along the transmission and reception paths of the WR link.
References:
[1] O. Lopez et al., « Frequency and time transfer for metrology and beyond using
telecommunication network fibres », Comptes Rendus Physique, vol. 16, no 5, p. 531-539, juin
2015, doi: 10.1016/j.crhy.2015.04.005.
[2] G. Daniluk, “White Rabbit calibration procedure,” 2015 https://white-
rabbit.web.cern.ch/documents/WR_Calibration-v1.1-20151109.pdf
[3] Dierickx, Erik and X. Yan, “WR Good practice guide,” May 2019
https://gitlab.com/ohwr/project/white-
rabbit/wikis/uploads/7df19b6a4d0e90bf6d7b8ae32b3b32c4/WR_Good_Practice_Guide.pd
Assembly process and quality control of the magnet cryostats for the HL-LHC project at CERN
No full textAs part of the High Luminosity Large Hadron Collider Upgrade (HL-LHC) at CERN, new focusing quadrupoles, separation and recombination dipoles, and corrector magnets will be installed on either side of the ATLAS and CMS experiments. Specific cryostat designs were developed to allow for the operation of these magnets at 1.9 K. A base design concept is progressed into 19 cryostat types to comply with requirements that depend on tunnel integration, cryogenics, instrumentation, and cold mass dimensions. The assembly process for the cryostats is split into two main phases: Phase 1 involves inserting the cold mass and thermal shield assembly into the vacuum vessel, while in Phase 2 a so-called service module is added to provide specific features and interfaces for installation in the LHC tunnel. In 2022, the production of the first cryostat began following the completion of the design, the procurement of components, the definition of the assembly process, and the availability of a magnet cold mass. This paper presents an overview of the assembly process and the quality controls utilised to ensure consistent, high-quality execution during the assembly of each cryostat. It examines several aspects, such as the specialised tooling utilised during the assembly, how strict leak testing requirements are met, as well as detailing some of the issues encountered and lessons learned
Cryostats for the HL-LHC magnets: Pre-series production, assembly infrastructure and project plans
No full textThe superconducting system of the High Luminosity LHC project (HL LHC) at CERN comprises a total of 38 new cold masses, prototypes and spares included, all requiring cryostats for magnet operation at 1.9 K. These cryostats shall ensure optimal thermal performance, as well as magnet alignment stability over the machine lifetime. Specific cold mass dimensions and a multitude of interfaces related to cryogenics, power supply and instrumentation resulted in 19 cryostat assembly types. Having so many design variants relative to the number of units to be built is a challenge in terms of cost, resources, and schedule management. Our answer was the development of a modular concept maximising component sharing between cryostat types, which also allows for a common assembly infrastructure. To date, manufacturing of cryostat components is nearly finished, and a pre-series comprising the first cryostat assemblies for each cold mass type has been built up to the stage of readiness for cold testing. This paper presents our experience and lessons learnt from component manufacturing and first assemblies, how we set up an assembly hall with purpose-built tooling, and insights on logistics and resources. We also explain our plans to ensure timely delivery of the cryostat assemblies, without compromises to the high reliability level expected for equipment that will become part of the 27 km long particle collider
Visit of Baroness Maggie Jones of Whitchurch Parliamentary Under-Secretary of State Department for Science, Innovation and Technology and the Department for Business and Trade
No full textBaroness Maggie Jones of Whitchurch Parliamentary Under-Secretary of State Department for Science, Innovation and Technology and the Department for Business and Trade United Kingdom of Great Britain and Northern Irelan
Searches for heavy resonances (including new scalars & BSM Higgs decays)
No full textThough the Standard Model (SM) of particle physics has been a very successful theory in explaining a wide range of measurements, there are still many questions left unanswered such as incorporation of gravity into SM, neutrino masses, matter-antimatter asymmetry, supersymmetry, or existence of dark matter candidates. One of the possible solutions to address these challenges is the extension of the SM with the presence of additional, heavy BSM particles; including scalar (H/S), pseudoscalar (A), or charged (H+-/H++--) BSM Higgs bosons. This is accounted for in multiple possible new physics models predicting the existence of these new, heavy particles. This talk summarises recent ATLAS searches for Beyond-the-Standard-Model heavy resonances, using the full Run 2 dataset
Rare few-body decays of the Standard Model Higgs boson
No full textWe present a survey of rare and exclusive few-body decays of the standard model (SM) Higgs boson, defined as those into two to four final particles with branching fractions . Studies of such decays can be exploited to constrain Yukawa couplings of quarks and leptons, probe flavour-changing Higgs decays, estimate backgrounds for exotic Higgs decays into beyond-SM particles, and/or confirm quantum chromodynamics factorization with small nonperturbative corrections. We collect the theoretical values for about 70 unobserved Higgs rare decay channels, indicating their current experimental limits, and estimating their expected bounds in p-p collisions at the HL-LHC. Among those, we include 20 new decay channels computed for the first time for ultrarare Higgs boson decays into photons and/or neutrinos, radiative quark-flavour-changing exclusive decays, and radiative decays into leptonium states. This survey can help guide and prioritize upcoming experimental and theoretical studies of unobserved Higgs boson decaysWe present a survey of rare and exclusive few-body decays of the standard model (SM) Higgs boson, defined as those into two to four final particles with branching fractions . Studies of such decays can be exploited to constrain Yukawa couplings of quarks and leptons, probe flavour-changing Higgs decays, estimate backgrounds for exotic Higgs decays into beyond-SM particles, and/or confirm quantum chromodynamics factorization with small nonperturbative corrections. We collect the theoretical values for about 70 unobserved Higgs rare decay channels, indicating their current experimental limits, and estimating their expected bounds in p-p collisions at the HL-LHC. Among those, we include 20 new decay channels computed for the first time for ultrarare Higgs boson decays into photons and/or neutrinos, radiative quark-flavour-changing exclusive decays, and radiative decays into leptonium states. This survey can help guide and prioritize upcoming experimental and theoretical studies of unobserved Higgs boson decays