Speaker
Description
The MUSHROOM instrument is a novel low energy indirect geometry neutron spectrometer being developed at the ISIS Neutron and Muon Source within the Endeavour Programme. It aims to deliver a significant gain in neutron flux and detection efficiency for studies of low energy excitations, placing stringent requirements on detector technology in terms of efficiency, spatial resolution, rate capability, and scalability. This contribution presents the proposed integration of µRWELL detectors as the baseline detection solution for MUSHROOM and discusses the corresponding mechanical, electrical, and material challenges.
The detector system is based on a modular geometry comprising 28 detector modules arranged around the sample position, divided equally into upper and lower circular arrays. Each module contains eight trapezoidal detector units, each with 48 one dimensional pixels at 3mm pitch. Such a detector will have a total area of 2.3 m2 and almost 11,000 readout channels. This configuration provides the required angular coverage while maintaining compactness within the detector vessel.
To meet the efficiency target of approximately 80% at a neutron wavelength of 4.3 Å, the detector has an active volume 20mm thick, pressurised to 2.5 bar with ³He. The 3 mm position resolution will be achieved by adding up to 1bar of CF4 to the gas mixture. The anticipated rate capability is demanding, with localised rates reaching 1–2 MHz per pixel during intense peaks that transiently propagate across the detector’s area, while most pixels operate at a few kHz.
The integration of µRWELL foils inside a pressurised vessel introduces several technical challenges. These include the mechanical attachment of the foils to neutron-absorbing backing materials such as boron nitride or sintered boron carbide, the routing of signal traces beneath readout pads while controlling crosstalk, and the optimisation of resistive-layer properties, targeting surface resistivities of around 20 MΩ/□.
The total ³He inventory required for the full detector system is estimated at approximately 220 L, which will be almost entirely recovered from old neutron detectors. The planned development path foresees several prototype iterations, with manufacturing readiness targeted for the first half of 2028. The successful deployment of µRWELL technology for MUSHROOM would represent a major step forward in high-rate, high-efficiency neutron detection for next-generation spectrometers at spallation sources.
| Name of the speaker | davide raspino |
|---|---|
| Eligible for the Georges Charpak Young Scientist Award. | no |