Improved direct detection of low-energy ions using a multipixel photon counter coupled with a novel scintillator

• A new silicon-based ion detector has been developed for time-of-flight mass spectrometry.
• The detector comprises a fast scintillator coupled to a single-photon avalanche diode array.
• Time resolution and sensitivity are improved by almost an order of magnitude compared with an earlier prototype.
• The detector does not require high vacuum or high voltages.
• The time resolution of the detector is 2 ns or better.

Recently, we described a direct low-energy ion detector for time-of-flight applications based on a single-photon avalanche diode (SPAD) array optically coupled to an LYSO (cerium-doped lutetium yttrium orthosilicate) scintillator. Here, we present a greatly improved version of the detector, developed through testing of a number of different scintillator and phosphor materials in combination with a commercially available SPAD array. The various scintillator materials have been characterized in terms of the achievable detection sensitivity and time response when used in conjunction with the SPAD array. Organic para-polyphenylene dyes, a relatively new class of scintillator for particle detection, were found to exhibit markedly improved performance relative to well-established scintillators such as LYSO crystal scintillators and P47 phosphors, both in terms of brightness and time response. The optimized detector has a time resolution of ∼2 ns, an improvement of more than an order of magnitude over the original version, at the same time as achieving a five- to ten-fold improvement in detection sensitivity. Our approach points the way towards the development of a generic silicon-based ion detector technology to complement or replace the microchannel-plate (MCP) ion detectors in widespread use at present. Such a detector would remove the need for high voltages and high vacuum, and at the same time greatly reduce detector cost relative to MCP-based detectors.

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