New Small Wheel Research Articles

ATLAS New Small Wheel Micromegas production and performance

The ATLAS collaboration at LHC has chosen the resistive Micromegas technology, along with the small-strip Thin Gap Chambers (sTGC), for the high luminosity upgrade of the first muon station in the high-rapidity region, the so called New Small Wheel (NSW) project. After the R&D, design and prototyping phase, the first series production Micromegas quadruplets have been constructed at all involved construction sites: in France, Germany, Italy, Russia and Greece. The achievement of the requirements for these detectors revealed to be even more challenging than expected when scaling from the small prototypes to the large dimensions. We describe the construction and relevant problems, to a large extent common to other micro-pattern gaseous detectors, and the adopted solutions. Final validation results on the achieved mechanical precision and on the stability during operation will be presented, along with the main results of the modules certification with cosmic rays. Additionally, one of the first series modules, equipped with a prototype of the final front-end electronics based on VMM chip, was tested in muon/pion beam at the H8 line of SPS at CERN during the summer of 2018. We present the test setup and performance results on efficiency and resolution for perpendicular and inclined tracks.

Note: Development of sTGC strip front-end readout prototype for ATLAS new small wheel upgrade.

This note presents the development of front-end electronics prototype for A Toroidal LHC ApparatuS (ATLAS) New Small Wheel (NSW) detector small-strip Thin Gap Chamber (sTGC) to be used for level-1 triggering and precision muon tracking at the Large Hadron Collider. The sTGC front-end electronics must deal with a large number of strip channels with very limited space constraint, large dynamic range of charge readout with low noise, simultaneous fast trigger, and precision readout data movement. The prototype uses custom radiation-tolerant application specific integrated circuits, optimized layout, power, and ESD protection networks to realize the above stringent requirements. The electronic test indicates that the front-end channel has a dynamic range of 900 pC and inherent noise of 0.19 fC. The sTGC cosmic ray test verified the precision charge measurement of the prototype, reconstructed the muon track, and measured the performance of sTGC. The NSW trigger chain test verified the trigger processing and 4.8 Gbps transmission of the prototype.

Mechanical modelling of the micromegas detectors for the atlas new small wheel

In order to benefit from the expected high luminosity performance provided by the Phase-I upgraded LHC at CERN, the New Small Wheel (NSW) will be installed in the ATLAS detector during the Long Shutdown 2. The ATLAS NSW will be equipped with a new technology for the detection of muons: the MicroMegas (MM) detectors. They consist of different panels made of composite materials and when charged particles traverse the drift space, the gas is ionized and electrons are liberated; the avalanche of electrons takes place in the amplification region after the mesh and they are detected by read-out strips to reconstruct the trajectory of muons produced after the collision. Very tight mechanical tolerances are given in the design phase and they must be preserved from the panel construction to the final operation in the ATLAS cavern.In this paper the construction procedure of these very precise particle detectors is described and the mechanical modelling to predict their mechanical behaviour is presented. Finally, the experimental tests done to validate the numerical models are discussed.

High voltage stability and cleaning of 2 m2 resistive strip micromegas detectors (SM2) for the upgrade of the forward muon spectrometer of the ATLAS experiment

Abstract For the upgrade of the innermost station of the forward muon spectrometer of the ATLAS experiment large Micromegas (MM) detectors of 2 and 3 m 2 with 4 active layers each are foreseen. Four types of MM chambers are produced among four sites. Each sites has to deliver 32 quadruplets or 128 active planes. The tiny 120 μ m distance between the 600 V resistive strip anodes and the ground micro-meshes for these large areas require adequate and well adapted cleaning procedures to guarantee high voltage stability. This is particularly critical for strip shaped surfaces made from resistive material where remnants from the lithographic production processes must be completely removed. The procedure foreseen a visual inspections to be carried on during cleaning and assembly procedures; a wet cleaning procedure to remove dust and possible ionic components of salts from the anode surfaces; a dry cleaning procedure to remove dust; HV tests to be done to validate the cleaning. The cleaning procedure will be illustrated for a New Small Wheel (NSW) Outer Small Module (SM2) of 2 m 2 .

Design and Testing of the Address in Real-Time Data Driver Card for the Micromegas Detector of the ATLAS New Small Wheel Upgrade

The address in real-time data driver card (ADDC) is designed to transmit the trigger data in the micromesh gaseous structure (Micromegas, MM) detector of the ATLAS new small wheel (NSW) upgrade. The address in real-time (ART) signals are generated by the front-end application-specific integrated circuit (ASIC), named VMM chip, to indicate the address of the first above-threshold event. A custom ASIC (ART ASIC) is designed to receive the ART signals from the VMM chip and implement the hit selection. The processed data from the ART ASIC will be transmitted out of the NSW through the gigabit transceiver (GBTx) serializer, the unidirectional versatile twin transmitter (VTTx), and fiber-optic links. The ART signal is critical for the ATLAS experiment trigger selection; thus, the performance and stability of the ADDC is very important. To ensure extensive testing of the ADDC, a field-programmable gate array (FPGA) mezzanine card (FMC)-based testing platform and a specially designed firmware/software are developed. This test platform works with the commercial Xilinx VC707 FPGA development kit; independent of the other electronics in the NSW, it can test all the functions of the ADDC and it has long-term stability. This article will introduce the design, testing procedure, and results of the ADDC and the FMC testing platform.

Development of FEB Configuration Test Board for ATLAS NSW Upgrade

The FEB(front end board) configuration test board is developed aiming at meeting the requirement of testing the new generation ASIC(application-specific integrated circuit) chips and its configuration system for ATLAS NSW(New Small Wheel) upgrade, In this paper, some functions are developed in terms of the configurations of the key chips on the FEB, VMM3 and TDS2 using GBT-SCA. Additionally, a flexible communication protocol is designed, verifying the whole data link. It provides technical reference for prototype FEB key chip configuration and data readout, as well as the final system configuration.

Performance studies of resistive Micromegas chambers for the upgrade of the ATLAS Muon Spectrometer

The ATLAS collaboration at LHC has endorsed the resistive Micromegas technology (MM), along with the small-strip Thin Gap Chambers (sTGC), for the high luminosity upgrade of the first muon station in the high-rapidity region, the so called New Small Wheel (NSW) project. The NSW requires fully efficient MM chambers, up to a particle rate of ∼ 15 kHz/cm2, with spatial resolution better than 100 μm independent of the track incidence angle and the magnetic field (B ≤ 0.3 T). Along with the precise tracking the MM should be able to provide a trigger signal, complementary to the sTGC, thus a decent timing resolution is required. Several tests have been performed on small (10 × 10 cm2) MM chambers using medium (10 GeV/c) and high (150 GeV/c) momentum hadron beams at CERN. Results on the efficiency and position resolution measured during these tests are presented demonstrating the excellent characteristics of the MM that fulfil the NSW requirements. Exploiting the ability of the MM to work as a Time Projection Chamber a novel method, called the μTPC, has been developed for the case of inclined tracks, allowing for a precise segment reconstruction using a single detection plane. A detailed description of the method along with thorough studies towards refining the method’s performance are shown. Finally, during 2014 the first MM quadruplet (MMSW) following the NSW design scheme, comprising four detection planes in a stereo readout configuration, has been realised at CERN. Test-beam results of this prototype are discussed and compared to theoretical expectations.

Study of the performance of Micromegas detectors in magnetic field

Resistive Micromegas (MICRO MEsh GAseous Structure) detectors have been chosen by the ATLAS collaboration at LHC for the high luminosity upgrade, due to their capability to maintain full efficiency and high spatial resolution at high occupancy, for tracking muons in the forward region of the detector. The Inner Muon Station, in the high-rapidity region, the so called New Small Wheel (NSW), will be composed of micromegas detectors that will have to maintain good performance in the presence of magnetic field of up to about 0.3 T. The response of micromegas detectors is affected by the magnetic field, where the deflection of the drift electrons is described by the Lorentz angle, resulting in a bias in the reconstructed track position. Several test-beam campaigns have been performed to test the behaviour of small size resistive micromegas prototypes (10×10 cm2) in magnetic fields up to 1 T, using high momentum muon and hadron beams at CERN. These studies are performed in order to validate the capability of the chambers to provide unbiased tracks in the NSW conditions. Measurements of the Lorentz angle and drift velocity as a function of the magnetic field are presented and both are compared to expectations based on Garfield-Magboltz simulations. Several methods to correct the position bias are applied, based on the chamber configuration or on the knowledge of the local value of the magnetic field. The results of these studies are presented together with an overall discussion of the Micromegas tracking capability in magnetic field.

Development of FEB Test Platform for ATLAS New Small Wheel Upgrade

This concept of test platform is based on the test requirements of the front-end board (FEB) which is developed for the phase I upgrade of the small Thin Gap Chamber(sTGC) detector on New Small Wheel(NSW) of ATLAS. The front-end electronics system of sTGC consists of 1,536 FEBs with about 322,000 readout of strips, wires and pads in total. A test platform for FEB with up to 256 channels has been designed to keep the testing efficiency at a controllable level. We present the circuit model architecture of the platform, and its functions and implementation as well. The firmware based on Field Programmable Gate Array (FPGA) and the software based on PC have been developed, and basic test methods have been established. FEB readout measurements have been performed in analog injection from the test platform, which will provide a fast and efficient test method for the production of FEB.

Visualization tool for X-ray scanner for sTGC detector production quality control

The ATLAS experiment at the Large Hadron Collider has an ambitious program of the detector upgrade to meet an expected rise of accelerator luminosity. The first large system which supposed to be installed in 2019 is the New Small Wheel (NSW) for ATLAS muon spectrometer. In order to ensure high quality and reliability of NSW chambers an X-ray scanning technique is being developed. One of the main components of the X-ray scanner is a special software visualization tool which would allow a fast and clear representation of scanning results and an identification of possible chamber defects.

Small-strip Thin Gap Chambers for the muon spectrometer upgrade of the ATLAS experiment

The ATLAS muon system upgrade to be installed during the LHC long shutdown in 2018/19, the so-called New Small Wheel (NSW), is designed to cope with the increased instantaneous luminosity in LHC Run 3. The small-strip Thin Gap Chambers (sTGC) will provide the NSW with a fast trigger and high precision tracking. The construction protocol has been validated by test beam experiments on a full-size prototype sTGC detector, showing the performance requirements are met. The intrinsic spatial resolution for a single layer has been found to be about 45μm for a perpendicular incident angle, and the transition region between pads has been measured to be about 4mm.

Micromegas detectors for the muon spectrometer upgrade of the ATLAS experiment

Large area Micromegas (MM) detectors will be employed for the Muon Spectrometer upgrade of the ATLAS experiment at the LHC. A total surface of about 150m2of the forward regions of the Muon Spectrometer will be equipped with 8 layers of MM modules. Each module covers a surface area of approximately 2–3m2 for a total active area of 1200m2. Together with the small-strips 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 planned 2018/2019 shutdown. This upgrade will maintain a low pT threshold for single muons and provide excellent tracking capabilities for the HL-LHC phase. The New Small Wheel (NSW) project requires fully efficient MM chambers with spatial resolution down to 100μm, at rate capability up to about 15kHz/cm2 and operation in a moderate (highly inhomogeneous) magnetic field up to B=0.3T. The required tracking capability is provided by the intrinsic spatial resolution combined with a challenging mechanical precision. The design, recent progress in the construction and results from the substantial R& D phase (with a focus on novel technical solutions) is presented. In the R& D phase, small and medium size single layer prototypes have been built, along with, more recently, the first two MM quadruplets in a configuration very close to the final one chosen for the NSW. Several tests have been performed on these prototypes at a high-energy test-beam at CERN, to demonstrate that the achieved performances fulfil the requirements. Recent tests applying various configuration and operating conditions are presented.

Radiation-hard power electronics for the ATLAS New Small Wheel

The New Small Wheel (NSW) is an upgrade for the ATLAS detector to provide enhanced triggering and reconstruction of muons in the forward region. The large LV power demands of the NSW necessitate a point-of-load architecture with on-detector power conversion. The radiation load and magnetic field of this environment, while significant, are nevertheless still in the range where commercial-off-the-shelf power devices may suffice.We present studies on the radiation-hardness and magnetic-fieldtolerance of several candidate buck converters and linearregulators. Device survival and performance are characterized whenexposed to gamma radiation, neutrons, protons and magnetic fields.