Manufacturing and Cleanliness of Beampipe for Einstein Telescope in High-vacuum

Problem Statement

The Einstein Telescope's vacuum tubes total 120 kilometers in length and must ensure that air and dust do not interfere with the sensitive measurements. The metal of the vacuum tubes themselves can also introduce contaminants into the vacuum, such as dust particles or water vapor. All process steps to produce the tubes can introduce contamination; from rolling, bending, sealing and conveying, to underground welding. The challenge is to develop procedures for all these steps that guarantee the plant will be clean at the high cleanroom level ISO-6 and ultra-high vacuum of 5-10-11 mbar. If existing technologies are applied, this will result in an expensive vacuum arm system. The production and underground installation and necessary cleaning also pose a challenge in terms of logistics and planning. Alternative cost-effective concepts for ET's vacuum tube system should lead to a feasible system in terms of technical specifications, finances and planning.

Objective

• A design of a vacuum tube tube made of ribbed steel. The ribbed tube has the following advantages: less material use and weight, while maintaining the same strength
• Development and qualification of procedures to produce tube elements cleanly and on a large scale
• Apply plasma technology to burn out the tubes; a more energy efficient alternative to existing procedures.

Description of Innovation.

The R&D consortium MACBETH (MAnufacturing and Cleanliness of Beampipe for Einstein Telescope in High-vacuum) is developing and qualifying procedures to produce tube elements cleanly and on a large scale. Within the consortium are several work packages for the different process steps. One of the work packages focuses on the challenges surrounding the use of a tube design made of ribbed steel, which has a thinner wall and therefore less weight and material cost than a smooth wall but is still just as sturdy. The more complex shape requires extra attention during manufacturing to ensure that the tube elements remain as clean as possible. Also being tested is a plasma technique that removes unwanted water vapor by treating the inside of the vacuum tube with hot, charged gas. With great energy savings compared to traditional firing out, where the entire tube is heated for days to force impurities out of the metal surface.