arXiv subjects

D. Lambert

Publications and source records attributed to D. Lambert.

10 recordsLinked to original sources

arXiv2023

Laser calibration of the ATLAS Tile Calorimeter during LHC Run 2

This article reports the laser calibration of the hadronic Tile Calorimeter of the ATLAS experiment in the LHC Run 2 data campaign. The upgraded Laser II calibration system is described. The system was commissioned during the first LHC Long Shutdown, exhibiting a stability better than 0.8% for the laser light monitoring. The methods employed to derive the detector calibration factors with data from the laser calibration runs are also detailed. These allowed to correct for the response fluctuations of the 9852 photomultiplier tubes of the Tile Calorimeter with a total uncertainty of 0.5% plus a luminosity-dependent sub-dominant term. Finally, we report the regular monitoring and performance studies using laser events in both standalone runs and during proton collisions. These studies include channel timing and quality inspection, and photomultiplier linearity and response dependence on anode current.

physics.ins-det↗

arXiv2021

Measurement of Single Event Effect cross section induced by monoenergetic protons on a 130 nm ASIC

Designing integrated circuits in radiation environments such as the High Luminosity LHC (HL-LHC) is challenging. Integrated circuits will be exposed to radiation-induced Single Event Effects (SEE). In deep sub-micron technology devices, the impact of SEEs can be mitigated by triple modular redundancy. The triplication of the most sensitive data is used to recover most of the data corruption induced by interacting particles. One type of SEE, called single event upset (SEU), is studied in this paper. The SEU cross-section and the performance of the triplication are estimated using an ASIC prototype exposed to a beam of protons. The SEU cross-section is measured, and a systematic difference between $1\rightarrow{0}$ and $0\rightarrow{1}$ bit flip rates is observed. The efficiency of the mitigation method is investigated.

physics.ins-det↗

arXiv2021

LCLS-II-HE verification cryomodule high gradient performance and quench behavior

An 8-cavity, 1.3 GHz, LCLS-II-HE cryomodule was assembled and tested at Fermilab to verify performance before the start of production. Its cavities were processed with a novel nitrogen doping treatment to improve gradient performance. The cryomodule was tested with a modified protocol to process sporadic quenches, which were observed in LCLS-II production cryomodules and are attributed to multipacting. Dedicated vertical test experiments support the attribution to multipacting. The verification cryomodule achieved an acceleration voltage of 200 MV in continuous wave mode, corresponding to an average accelerating gradient of 24.1 MV/m, significantly exceeding the specification of 173 MV. The average Q0 (3.0x10^10) also exceeded its specification (2.7x10^10). After processing, no field emission was observed up to the maximum gradient of each cavity. This paper reviews the cryomodule performance and discusses operational issues and mitigations implemented during the several month program.

physics.acc-ph↗

arXiv2019

Test Results of PIP2IT MEBT Vacuum Protection System

The central part of PIP-II program of upgrades pro-posed for the Fermilab injection complex is an 800 MeV, 2 mA, CW-compatible SRF linac. Acceleration in super-conducting cavities begins from a low energy of 2.1 MeV, so that the first cryomodule, Half Wave Resonator (HWR) borders the warm Medium Beam Transport (MEBT) line. To minimize the amount of gas that may enter the SRF linac in a case if a vacuum failure occurs in the warm front end, a vacuum protection system is envisioned to be used in the PIP-II MEBT. It features a fast closing valve with two sensors and a differential pumping insert. The system prototype was installed in the PIP-II Injector Test (PIP2IT) accelerator and successfully tested in several modes modelling the vacuum failures. The report presents the design of the vacuum protection system and results of its tests.

physics.acc-ph↗

arXiv2018

The High Voltage distribution system of the ATLAS Tile Calorimeter and its performance during data taking

This article documents the characteristics of the high voltage (HV) system of the hadronic calorimeter TileCal of the ATLAS experiment. Such a system is suitable to supply reliable power distribution into particles physics detectors using a large number of PhotoMultiplier Tubes (PMTs). Measurements performed during the 2015 and 2016 data taking periods of the ATLAS detector show that its performance, in terms of stability and noise, fits the specifications. In particular, almost all the PMTs show a voltage instability smaller than 0.5 V corresponding to a gain stability better than 0.5%. A small amount of channels was found not working correctly. To diagnose the origin of such defects, the results of the HV measurements were compared to those obtained using a Laser system. The analysis shows that less than 0.2% of the about 10 thousand HV channels were malfunctioning.

physics.ins-det↗

arXiv2013

Performance of the LHCb RICH detector at the LHC

The LHCb experiment has been taking data at the Large Hadron Collider (LHC) at CERN since the end of 2009. One of its key detector components is the Ring-Imaging Cherenkov (RICH) system. This provides charged particle identification over a wide momentum range, from 2-100 GeV/c. The operation and control software, and online monitoring of the RICH system are described. The particle identification performance is presented, as measured using data from the LHC. Excellent separation of hadronic particle types (pion, kaon and proton) is achieved.

physics.ins-det↗

arXiv2012

Partial inner product spaces: Some categorical aspects

We make explicit in terms of categories a number of statements from the theory of partial inner product spaces (PIP spaces) and operators on them. In particular, we construct sheaves and cosheaves of operators on certain PIP spaces of practical interest.

math-ph↗

arXiv2001

The Lemaitre-Schwarzschild Problem Revisited

The Lemaitre and Schwarzschild analytical solutions for a relativistic spherical body of constant density are linked together through the use of the Weyl quadratic invariant. The critical radius for gravitational collapse of an incompressible fluid is shown to vary continuously from 9/8 of the Schwarzschild radius to the Schwarzschild radius itself while the internal pressures become locally anisotropic.

gr-qc↗

arXiv2001

Noncommutative Riemannian Geometry of the Alternating Group A_4

We study the noncommutative Riemannian geometry of the alternating group $A_4=(Z_2 \times Z_2)\cross Z_3$ using a recent formulation for finite groups. We find a unique `Levi-Civita' connection for the invariant metric, and find that it has Ricci-flat but nonzero Riemann curvature. We show that it is the unique Ricci-flat connection on $A_4$ with the standard framing (we solve the vacuum Einstein's equation). We also propose a natural Dirac operator for the associated spin connection and solve the Dirac equation. Some of our results hold for any finite group equipped with a cyclic conjugacy class of 4 elements. In this case the exterior algebra $Ω(A_4)$ has dimensions $1:4:8:11:12:12:11:8:4:1$ with top-form 9-dimensional. We also find the noncommutative cohomology $H^1(A_4)=C$.

math.QA↗

arXiv2000

Light Element Abundance Patterns in the Orion Association: I) HST Observations of Boron in G-dwarfs

The boron abundances for two young solar-type members of the Orion association, BD -6 1250 and HD 294297, are derived from HST STIS spectra of the B I transition at 2496.771 A. The best-fit boron abundances for the target stars are 0.13 and 0.44 dex lower than the solar meteoritic value of log e(B)=2.78. An anticorrelation of boron and oxygen is found for Orion when these results are added to previous abundances obtained for 4 B-type stars and the G-type star BD -5 1317. An analysis of the uncertainties in the abundance calculations indicates that the observed anticorrelation is probably real. The B versus O relation observed in the Orion association does not follow the positive correlation of boron versus oxygen which is observed for the field stars with roughly solar metallicity. The observed anticorrelation can be accounted for by a simple model in which two poorly mixed components of gas (supernova ejecta and boron-enriched ambient medium) contribute to the new stars that form within the lifetime of the association. This model predicts an anticorrelation for Be as well, at least as strong as for boron.

astro-ph↗