The Accelerator Diagnostics and Instrumentation (ADI) group is responsible for the implementation and maintenance of diagnostic systems on ASTeC's test facilities, such as CLARA, and is heavily involved in electronics upgrades to existing systems installed on VELA and the CLARA front-end. Among the systems supported on these machines are charge measurements devices, such as Faraday cups and wall current monitors, strip-line and button beam position monitors, as well as screens and associated camera systems.

The group also has a team of highly skilled electronic technicians and apprentices, who support other groups with expertise in fabrication and assembly of electronic systems. These technicians also operate the group's facilities for rapid prototyping new designs through on-site circuit board and additive manufacturing. In addition to supporting ASTeC's own test facilities, they have contributed to projects at other laboratories, such as RAL, CERN and ESS. The group has close ties with Technology @ Daresbury, in particular groups such as the Controls Systems and Safety Interlocks Group, Detector Systems Group and Nuclear Physics Group.

In addition to its day-to-day operations, the group carries out cutting-edge research into novel accelerator diagnostics, such as dielectric wakefield acceleration and novel longitudinal diagnostics. Examples of systems developed include the CLARA Bunch Compression Monitor, which provides qualitative measurements of the electron bunch length produced by the CLARA front-end.

The ADI group also supports the STFC's strategic goal of developing world-class skills by participating in its apprenticeship programme. The group has four apprentices and one technician all undertaking degree apprenticeships in electronics engineering.