1. Design and Construction of Large Size Micromegas Chambers for the ATLAS Upgrade of the Muon Spectrometer
- Author
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Fabien Jeanneau, Département de Physique Nucléaire (ex SPhN) (DPHN), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay
- Subjects
Physics::Instrumentation and Detectors ,HE Physics ,Tracking (particle physics) ,01 natural sciences ,law.invention ,high-energy physics experiment ,law ,Wheels ,Strips ,ATLAS upgrade ,momentum resolution ,optical alignment ,mechanical precision ,particle tracks ,micromegas chamber construction ,Physics ,Large Hadron Collider ,Mesons ,Detector ,MicroMegas detector ,Detectors ,NSW ,tracking software ,spectrometer: upgrade ,micromegas chamber design ,medicine.anatomical_structure ,mechanical engineering ,8-layer micromegas module ,mesh tension ,strip thin gap chamber ,Atlas ,LHC ,Micromegas ,Particle Physics - Experiment ,muon tracking ,Coordinate measuring machines ,Nuclear and High Energy Physics ,STRIPS ,fabrication ,innermost station ,pseudorapidity coverage ,particle spectrometers ,Nuclear physics ,thermal gradient function ,Optics ,Atlas (anatomy) ,position resolution ,Muon spectrometer ,0103 physical sciences ,medicine ,[PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det] ,Electrical and Electronic Engineering ,010306 general physics ,numerical calculations ,Spatial resolution ,Muon ,010308 nuclear & particles physics ,business.industry ,deformation ,Order (ring theory) ,position sensitive particle detectors ,muon detection ,micromegas detector ,Nuclear Energy and Engineering ,MPGD (Micropattern Gaseous detector) ,business ,muon: spectrometer - Abstract
Large area Micromegas detectors will be employed for the first time in high-energy physics experiments. A total surface of about 150 m2 of the forward regions of the Muon Spectrometer of the ATLAS detector at LHC will be equipped with 8-layer Micromegas modules. Each module extends over a surface from 2 to 3 m2 for a total active area of 1200 m2. Together with the small strip Thin Gap Chambers they will compose the two New Small Wheels, which will replace the innermost stations of the ATLAS endcap muon tracking system in the 2018/19 shutdown. In order to achieve a 15% transverse momentum resolution for 1 TeV muons, in addition to an excellent intrinsic resolution, the mechanical precision of each plane of the assembled module must be as good as 30 μm along the precision coordinate and 80 μm perpendicular to the chamber. In the prototyping towards the final configuration two similar quadruplets with dimensions 1.2×0.5 m2 have been built with the same structure as foreseen for the NSW upgrade. It represents the first example of a Micromegas quadruplet ever built, realized using the resistive-strip technology and decoupling the amplification mesh from the readout structure. All readout planes are segmented into strips with a pitch of 400 μm for a total of 4096 strips. In two of the four planes the strips are inclined by 1.5o and provide a measurement of the second coordinate. The design and construction procedure of the Micromegas modules will be presented, as well as the design for the assembly of modules onto the New Small Wheel. Emphasis will be given on the methods developed to achieve the challenging mechanical precision. Measurements of deformation on chamber prototypes as a function of thermal gradients, gas over-pressure and internal stress (mesh tension and module fixation on supports) will be also shown in comparison to simulation. These tests were essential in the development of the final design in order to minimize the effects of deformations. During installation and operation all deformations and relative misalignments will be monitored through an optical alignment system and compensated in the tracking software. The optical alignment concept will also be outlined.
- Published
- 2015