Online program Overview Session: NSS-24

Abstract

The High-Luminosity upgrade of the Large Hadron Collider (HL-LHC) will subject the Compact Muon Solenoid (CMS) experiment to unprecedented particle rates and radiation levels. To maintain high-efficiency muon triggering and reconstruction in this challenging environment, CMS is upgrading its forward muon system, including Gas Electron Multiplier (GEM) technology. This program introduces two key stations: GE1/1 and ME0.

The GE1/1 station, composed of triple-GEM detectors, was installed during Long Shutdown 2 to complement the existing Cathode Strip Chamber stations in the 1.6 < |η| < 2.15 region. Operational since the start of Run 3, GE1/1 has significantly enhanced redundancy and Level-1 trigger performance. This presentation reviews the operational experience gained during Run 3, focusing on detector performance, electronics optimizations, and the continuous improvements implemented to ensure seamless system integration.

Looking further ahead, the ME0 station is designed for installation during Long Shutdown 3 to extend the muon system's coverage up to |η| = 2.8. To withstand the high-rate environment of the HL-LHC, ME0 incorporates advanced design optimizations and robust background rejection capabilities. We present the current status of the ME0 project, including results from the latest prototype studies, time resolution performance, and the progress of the ongoing mass production.

Together, these GEM upgrades are pivotal for extending the physics reach of CMS, ensuring high-quality muon identification and tracking in the most demanding regions of the detector.

Abstract

A novel Micro-Pattern Gaseous Detector (MPGD) technology based on μ-RWELL is under development as a potential replacement for the most irradiated regions of the LHCb muon
system at CERN, in view of the Upgrade II program. The μRWELL is a resistive MPGD featuring a compact single-stage amplification structure with typical gains up to 10⁴, making
it well suited for operation in harsh radiation environments. An improved detector layout, the G-RWELL, is currently under study. This configuration enhances the standard μ-RWELL
design by introducing a single GEM pre-amplification stage, allowing gains up to 10⁵ under stable operating conditions. These features make the technology suitable for the extreme rate
capability required at the future LHC high-luminosity conditions, where peak luminosity of L = 1.5×10³⁴ cm⁻²sec⁻¹ is planned. The presentation will focus on the ongoing research activities
on these detector technologies in the context of the LHCb muon Upgrade II. Particular emphasis will be given to recent testbeam campaigns at the CERN PS beam line, involving the use of
the FATIC front-end electronics, currently under development, and a dedicated data analysis framework optimized for this readout.

Abstract

The Future Circular electron-positron Collider, proposed as future flagship at CERN, offers a unique opportunity for precision measurements of the Higgs boson and electroweak properties. To meet the stringent requirements of a future Inner Tracker in terms of momentum resolution, particle identification, and minimal material budget, a scalable, ultra-light gaseous detector concept based on straw tubes is under development. 
This contribution presents the design and construction of a 1.5 m-long straw tube chamber prototype. 
As part of the mechanical feasibility study, the importance of the tube wall pre-tensioning during assembly was identified to prevent a drift radius asymmetry.
Via a CERN test beam validation a comprehensive study of the prototype has been performed. The applied grounding scheme was successful, since the noise rates are below 100 Hz.
Through a muon detection efficiency of 100% except for a narrow region close to the tube wall and a spatial resolution of 118 μm, the suitability of the straw tube tracker for an inner detector of a future e⁺e^- collider experiment is demonstrated. 
Combining the test beam data with Garfield++ simulations allows for a prediction of the expected the particle identification capabilities, yielding a π/K separation mostly better than 3σ up to momenta of 10 GeV. 
Owing to their reduced material budget, straw tubes exhibit a low gamma conversion probability, although the resulting Compton electrons are not stopped within the thin tube wall.
Subsequently, crucial input for the optimization of future prototypes is provided, which is directly addressed in the next generation 4 m-long straw tube chamber prototype.
This contribution will additionally present the latest performance results from the up-scaled 4m prototype, obtained during the upcoming CERN test beam campaign in July.

Abstract

This work presents performance measurements of the first neutron detector module developed for the Cold Neutron Spectrometer (CSPEC) hosted at the European Spallation Source (ESS). Designed and built at the Laue-Langevin Institute (ILL), the detector employs a two-dimensional Multitube architecture to meet the CSPEC requirements in terms of spatial resolution count rate capability and amplification gain stability and uniformity. Experimental tests completed at the CT2 detector test beamline of ILL, confirm compliance to these detection features while validating the production process for the next modules.

Abstract

We report characterization of a high-efficiency multi-element neutron dosemeter built by the Thick Gas Electron Multiplier (THGEM) technology. The multi-element configuration is an excellent way to increase neutron detection efficiency and is well suited for the development of tissue-equivalent proportional counters (TEPCs) for microdosimetric measurements in low-intensity neutron fields. Compared to conventional TEPCs, the THGEM-based design eliminates the need for anode wire structures, thereby simplifying fabrication and assembly processes. Moreover, the capability of cascading multiple THGEM layers to achieve higher gain, combined with its low cost, mechanical robustness, and large-area scalability, are advantageous features of the THGEM for building multi-element detectors. Following the successful development of an initial prototype consisting of twenty-one gaseous sensitive volumes, an upgraded detector with ninety-five sensitive volumes has been developed to increase neutron efficiency even higher. Experimental characterization of the new detector is currently underway using ²³⁸PuBe and ⁷Li(p,n) neutron sources at the McMaster Accelerator Laboratory. The signal performance and dosimetric response of the detector will be presented and compared with Monte Carlo simulation results.

Abstract

Conventional gaseous detectors rely on electron drift, but this transport is intrinsically limited by diffusion, particularly in noble-gas mixtures and over long drift distances. Electronegative additives offer an attractive alternative because they rapidly capture electrons and form negative ions, which drift with much smaller diffusion, enabling improved spatial resolution. In this work, Xe-SF₆ mixtures were investigated using a dedicated experimental setup to study electron attachment, ion mobility, electron detachment, charge multiplication, and electroluminescence. Near-total electron attachment was observed in all cases, confirming the efficient formation of negative ions in Xe-SF₆ mixtures. In the low-field regime, two negative-ion species, SF₆^- and clustered SF₆^-(SF₆), were identified, with reduced mobilities remaining independent of the electric field. High electric fields inside GEM holes enabled electron detachment and subsequent amplification, with EL and multiplication thresholds shifting to lower fields and gas gains increasing as the SF₆ concentration decreased. Xenon electroluminescence was also observed in these mixtures, both inside the GEM and after, although strongly quenched by the electronegative additive. The increase in the thresholds for both scintillation and charge multiplication with increasing SF₆ fraction, highlight the central role of the detachment processes in the amplification mechanisms. These results demonstrate that even a very small addition of SF₆ can substantially modify xenon transport properties. However, the usual amplification stages are not immune to these changes.