Speaker
Description
The search for the hypothetical X17 boson has motivated the design of the MX17 experiment at the CERN n_TOF facility. To accurately reconstruct the coincident e+ e- pairs associated with this search, we have developed a large-area Micromegas detectors at CEA Saclay. These detectors feature a 40 x 40 cm² active area and are designed to provide good spatial resolution while operating under the constraints of a limited number of DREAM-based electronics channels.
To optimize the channel count without sacrificing performance, we implemented a high-granularity XY pixel-strip pattern. In this configuration, pixels are interconnected to internal strips, a technique evolved from the CAST experiment. Each pixel is surrounded by eight neighbors connected to different strips to enhance charge sharing. Achieving this design required the fabrication of a 300µm thick PCB containing 262,144 metallized holes, successfully produced by the CERN Workshop.
Key technical features of the detector include:
Charge Sharing & Spark Protection: A resistive layer was applied via screen printing at the Saclay MPGD workshop using Saral paste of 4 MΩ/sq. Two patterns were evaluated: a plain resistive center with high-resistance "buried" HV connections and a strip-only resistive pattern.
Detector Construction: The Bulk process utilized Dynamask layers and an ASADA 45/19 mesh. To ensure mechanical planarity, the readout PCB is reinforced with a 5 mm Rohacell backing. The Bulk is design to have a floating mesh that can be grounded or optional charge injected.
Modular Readout: Connectivity is handled via GZS connectors on the readout PCB, avoiding direct welding. This interface leads to exchangeable multiplexing cards (M1, M2, and M4 schemes) allowing for 2048, 1024, or 512 channels per detector to match the DREAM Front End Unit availability.
µTPC Capability: The detector features a 30 mm drift gap enclosed in an aluminum frame with a 30µm Mylar window. A field cage using high-value resistors ensures field uniformity, enabling operation in µTPC mode for 3D track reconstruction.
Of the six detectors to be manufactured at CEA Saclay, four are designated for the final MX17 experimental setup. This presentation will report on the performance of the first two production modules, including results from the Saclay cosmic test bench regarding spatial resolution, tracking efficiency, and gain stability.
| Name of the speaker | Stephan Aune |
|---|---|
| Eligible for the Georges Charpak Young Scientist Award. | no |