GCA: What materials are used for Glass Capillary Array?

Based on the sources provided, Glass Capillary Arrays (GCAs) can be manufactured using several types of glass, primarily depending on the application and the manufacturing process.

The main materials mentioned for GCAs are:

• Borosilicate Glass This type of glass is frequently highlighted as the material used for "next generation" Microchannel Plates (MCPs) fabricated with the etchless "hollow-core" glass drawing process and Atomic Layer Deposition (ALD) functionalisation. Borosilicate glass is described as being considerably less expensive than traditional materials and is similar to Pyrex. Advantages of using borosilicate glass for GCAs in these applications include its increased physical durability and robustness, low alkali content (such as potassium and rubidium) which leads to reduced background noise, lower cross-section for gamma ray detection, and the fact that it does not require chemical etching or hydrogen firing, thus avoiding embrittlement found in traditional MCPs. Specific borosilicate types like borofloat glass are also mentioned as being used for GCA-based MCPs. An electrochemical device architecture is also described using a borosilicate GCA.
• Lead Glass This is the traditional material used for MCPs. Conventional MCP manufacturing involves thermal co-drawing of lead glass tubes and rods, stacking, fusing, and then chemically etching away the core glass, leaving the porous structure in lead glass. Traditional lead glass MCPs can be expensive, brittle, and the glass typically contains radioactive alkali metals like potassium, contributing to background noise.
• Other Glass Options The sources indicate that a wide variety of glass options are available for GCAs. Beyond general types like borosilicate, glasses can be chosen for specific properties needed for the application. This can include glass with an enhanced boron 10 component or gadolinium to improve sensitivity to thermal neutrons. One manufacturer lists specific glass types C5 and C14, providing their refractive index, density, and coefficient of thermal expansion.

In summary, while lead glass has been the historical standard, modern GCAs, particularly those used in conjunction with ALD for next-generation detectors, frequently utilise borosilicate glass and offer a variety of other custom glass compositions for specialised applications.