Fieldable Muon Spectrometer Using Multi-Layer Pressurized Gas Cherenkov Radiators and Its Applications

Cosmic ray muons have been considered as a non-conventional radiation probe in various applications. To utilize cosmic ray muons in engineering applications, two important quantities, trajectory and momentum, must be known. The muon trajectories are easily reconstructed using two-fold detector arrays with a high spatial resolution. However, precise measurement of muon momentum is difficult to be achieved without deploying large and expensive spectrometers such as solenoid magnets. Here, we propose a new method to estimate muon momentum using multi-layer pressurized gas Cherenkov radiators. This is accurate, portable, compact (< 1m3), and easily coupled with existing muon detectors without the need of bulky magnetic or time-of-flight spectrometers. The results show that not only our new muon spectrometer can measure muon momentum with a resolution of ±0.5 GeV/c in a momentum range of 0.1 to 10.0 GeV/c, but also we can reconstruct cosmic muon spectrum with high accuracy (~90%).

The Micromegas Surface Commissioning For the ATLAS New Small Wheel

In order to cope with the required precision tracking and trigger capabilities from Run III onward in the ATLAS experiment, the innermost layer of the Muon Spectrometer end-cap (Small Wheels) will be upgraded. Each of the two New Small Wheels (NSW) will be equipped with eight layers of MicroMegas (MM) detectors and eight layers of small-strip Thin Gap Chambers (sTGC), both arranged in two quadruplets. MM detectors of large size (up to 3m2) will be employed for the first time in HEP experiments. Four different types of MM quadruplet modules (SM1, SM2, LM1, LM2), built by different Institutes, compose the NSW. The modules are then sent to CERN, integrated into double wedges (DW), tested and sent for commissioning on the wheel itself. At the commissioning stage the MM double wedges along with the sTGC wedges are assembled together into sectors which are then installed and tested on the wheel. Each wheel comprises 8 small (made of SM1 and SM2 modules) and 8 large (made of LM1 and LM2 modules) sectors, in order to provide full coverage of the end caps. The first of the two wheels (NSW-A) has been fully commissioned, installed in ATLAS and the first tests are currently ongoing. The second wheel (NSW-C) is currently under commissioning and is expected to be ready by October this year.

Implementation of the DCS System for the validation of MM HV Boards and the DCS System of the new BIS78 Chambers for the upgrade of muon system of the ATLAS Experiment

The ATLAS Muon Spectrometer is going through upgrades on the Phase I in order to achieve higher rates for the upcoming LHC runs. The two main projects of this Phase I upgrade are the New Small Wheels (NSW), which are expected to complement the ATLAS muon spectrometer in the end-cap regions and a smaller size project, known as BIS78 (Barrel Inner Small sectors). The NSW is expected to replace the Small Wheel (SW) and it will be installed in the ATLAS underground cavern during the summer by the end of the LHC Long Shutdown 2. This new system will be consisted by two prototype detectors, the sTGC (small Thin Gas Chambers) and the resistive Micromegas (MM). In order to cope with higher LHC luminosities, the installation of NSW will help the reduction of the trigger rate in the forward region. With half of the rate in the barrel-endcap transition region reduced by the existing TGCs, the other half of the fake trigger rate in transition region will be reduced by the new BIS78 stations. The BIS78 subproject foresees the replacement of the existing Monitored Drift Tubes (MDTs), used for the precise position measurement in this area, with muon stations formed by integrated smaller diameter tubes (sMDT) and a new generation of RPCs, capable of withstanding the higher rates and provide a robust standalone muon confirmation. The existing BIS7 and BIS8 MDT Chambers will be replaced by 16 new muon stations of one small (sMDT) chamber and two RPC triplets, and it will be the pilot project for the Phase II BI Upgrade. This work is divided into two parts. First will be presented the development and the implementation of a Detector Control System (DCS) for the HV system for the MM detectors of NSW and specifically the validation of a new type of HV Boards (A7038AP). Second, the development of the DCS for the monitoring and operation of the new sMDT chambers of the MDT Sub-System will be presented.

Construction and operation of large scale Micromegas detectors for the ATLAS Muon upgrade

After the forthcoming upgrade of the LHC accelerator at CERN, its luminosity will increase up to 7.5 × 1034 cm−2s−1. That will raise the readout rates and the background data to unmanageable levels for the existing ATLAS muon spectrometer. The ATLAS collaboration has proposed to replace the present small wheel muon detector with the New Small Wheel (NSW) to surpass those limitations. The new wheels consist of Micromegas (MM) and small-strip Thin Gap Chambers (sTGC). The first technology aims for precision tracking, and the last one for trigger purposes. Each wheel will be equipped with eight small and eight large sectors, while each sector will have a double MM wedge surrounded by sTGC wedges. The MM detectors for the NSW will be the largest developed Micro Pattern Gaseous Detector (MPGD) as they will cover an area up to 1280 m2. During detectors’ manufacture have been used various custom materials (PCBs, mesh) and innovative construction techniques. This paper describes the MM drift panels production at Aristotle University of Thessaloniki laboratory. Then will be presented resolution results of the MM detectors with cosmic-ray tests at CERN facilities.

Design of a Differential Safety Mechanism (DSM) Dedicated to the NSW Micromegas Wedges

The New Small Wheel Micromegas detector system for the Upgrade of ATLAS Muon Spectrometer is in the phase of integration and commissioning at the Laboratories BB5 and Building 191 at CERN respectively. In this framework, the produced modules are evaluated and tested at a Cosmic Ray Stand or at their final position on New Small Wheel. Providing gas mixture to the Micromegas Wedges, the static gauge pressure inside the detector’s layers must be kept below a nominal value around 3 mbar. Pressures above 10 mbar, due several reasons or gas line blocking, could cause serious damages in the detectors. In this work we describe the principle of operation and the design of a low cost intelligent unit, the “Differential Safety Mechanism”, dedicated to protect the Micromegas Wedges against unexpected slow or sudden increase of the static gauge pressure. The internal detailed structure, the simulation and the prototype tests of the DSM are presented analytically in this work.