Nanodiamond Photodes Achieve 4% Efficiency, Demonstrating 10x Robustness over CsI in MPGD Detectors

Single-photon detection is crucial for a range of applications, from medical imaging to fundamental physics research, and currently relies heavily on fragile and short-lived materials like caesium iodide. Now, a team led by F. M. Brunbauer, C. Chatterjee, and G. Cicala, working at INFN Trieste in Italy, demonstrates the potential of nanodiamond as a robust alternative photocathode material. Their research characterises nanodiamond coatings on detector components, revealing a quantum efficiency that, while lower than the best fresh caesium iodide, exhibits significantly improved resilience to ion bombardment, lasting approximately ten times longer. This achievement suggests nanodiamond offers a pathway to more durable and reliable single-photon detectors, promising enhanced performance and longevity in demanding experimental environments.

Nanodiamond Photocathodes for Gaseous Detectors

This research investigates the potential of nanodiamond and hydrogenated nanodiamond (HND) as alternatives to Cesium Iodide (CsI) in photon detectors used in gaseous detectors, particularly those requiring precise timing resolution. Scientists successfully created and tested HND photocathodes, demonstrating significant quantum efficiency and full compatibility with THGEM (Triple-GEM) detectors. This work is crucial for advancing detector technologies used in future experiments, including those at Electron-Ion Colliders. A key finding is the exceptional resistance of HND photocathodes to ion bombardment, approximately ten times greater than that of CsI, promising longer detector lifetimes and reduced maintenance.

Furthermore, the team produced semi-transparent HND photocathodes, showing promising initial results for detectors requiring light transmission. The research confirms that nanodiamond and HND coatings do not negatively impact THGEM detector performance, maintaining stable gains. Importantly, HND photocathodes exhibit better aging characteristics than CsI, retaining usable performance even after being stored in water for two years. While the achieved quantum efficiency is not yet comparable to freshly prepared CsI, the team is focused on optimizing the HND coating process to further enhance performance. Ongoing and future work focuses on optimizing coating techniques and utilizing freshly hydrogenated nanodiamond powder to maximize quantum efficiency.

Hydrogenated NanoDiamond Robust Photon Detection Demonstrated

This research demonstrates the viability of Hydrogenated NanoDiamond (HND) as a robust alternative to Cesium Iodide (CsI) in photon detectors used in gaseous detectors. Scientists achieved a quantum efficiency of approximately 4% at 122nm with HND photocathodes, a value within a factor of ten of the best freshly hydrogenated samples. The team developed a novel method for HND hydrogenation and coating, utilizing a pulsed spray technique to deposit HND grains onto substrates and THGEMs. This process involved dispersing HND in water, sonicating the solution, and applying it to heated surfaces to facilitate solvent evaporation.

Crucially, tests reveal that HND photocathodes exhibit significantly improved robustness against ion bombardment compared to CsI, maintaining approximately ten times greater resistance to degradation under the same conditions. Aging studies demonstrate the superior stability of HND photocathodes during prolonged exposure to ion bombardment in an Ar/CO2 gas mixture. Characterization of THGEMs coated with HND layers reveals minimal alteration in detector response, suggesting seamless integration with existing detector technologies. The team meticulously controlled the coating process, optimizing surface coverage and minimizing splash effects. These findings establish HND as a promising material for enhancing the performance and reliability of single-photon detection systems, particularly in applications demanding robust and long-lasting detectors.

HND Photocathodes Enhance Detector Robustness and Performance

Scientists successfully prepared and tested HND photocathodes, achieving quantum efficiency values within a factor of ten of those reported for freshly hydrogenated samples. The team found that the HND coatings did not negatively impact the performance of THGEM detectors, maintaining stable operational gains. Further investigation revealed a significant advantage in robustness; HND photocathodes exhibited approximately ten times greater resistance to ion bombardment compared to CsI, suggesting improved longevity and reliability. The researchers also produced semi-transparent HND samples, yielding promising initial results for picosecond time-resolution configurations. While the HND material was stored in water for over two years, the results confirm significant quantum efficiency and full compatibility with THGEM operation. The team also plans to investigate the behavior of HND photocathodes in different gas mixtures and develop a prototype picosecond detector based on this technology.