The master craftsmen of the electronics world

At the forefront of the development of electronic modules, the DEM group provides continuous support for the engineers and technicians of the LHC experiments.

The DEM group produced 400 electronic circuit boards needed for checking the LHC accelerating cavities at Point 4.

Like all the accelerator components, the accelerating cavities that will give the protons the necessary "kick" as they hurtle their way around the ring are brimming with electronics, but their control electronics are highly specific. The challenge of producing the associated electronic boards, which were designed by the AB-RF group, was taken up by the TS Department’s Development of Electronic Modules (DEM) group. The project was completed at the end of December with the delivery of 400 of the boards.

The TS-DEM group is a closely knit community. From left to right: Betty Magnin (section leader of the design office and cabling workshop), Erik van der Bij (group leader), Rui de Oliveira, section leader of PMT (production of printed circuits).

The DEM group steadfastly meets all the specific orders for printed circuit boards and detector circuits emanating from the various experiments. "Electronics at CERN are in a way CERN’s nervous system. Electronic components form an integral part of the data transfer and detector control systems", says group leader Erik van der Bij. "Our objective is to be able to provide the expertise that is not available in industry."

With constant demands on its technical skills, flexibility and innovation, the DEM group has to be highly responsive. It has already designed, manufactured and assembled in situ thousands of tailor-made components, many of them unique. DEM has the necessary technical skills and expertise to design and produce prototypes on the spot.

Organised like a small 40-man company, the group is able to follow the production planning process from start to finish. Being in charge of all stages of the process from product design to completion allows greater flexibility and hones the group’s specialist capabilities.

DEM is able to respond to a wide variety of sometimes highly complex requirements, from the supply of thousands of thermometers for the LHC cryogenics system, for example, to the development of new patented procedures like the "chemical microvia" process used, among other things, for the chemical etching of kapton sheets for the ATLAS TRT. The scale of difficulty varies according to the size, the density of the connections and, occasionally, the exposure conditions.

The continual need for innovation

In response to an order from ALICE, the group recently completed a four-year project to deliver the components of a unique product: an ultra-light integrated circuit with specially designed aluminium connections. Copper, which is much heavier, would have interfered with the trajectory of the particles to be measured to an unacceptable degree. The DEM group will shortly start work on a new project to design 84 TPC Micromegas detectors for the T2K magnet, a neutrino experiment that will start up in Japan in 2009.

Each year around fifty different prototypes leave the clean room, a meticulously kept area where the technicians assemble and check electronic circuits under the microscope with a goldsmith’s patience. The components can be as small as 10 microns (six times finer than a human hair). "We produce some fine jewels", agrees Erik van der Bij, proudly displaying a read-out circuit with a fine gold deposit. The degree of precision is such that a single 10 cm square kapton sheet designed for a GEM detector can contain a million holes, the equivalent of ten scalps.

In 2007 the DEM group had over 300 users. It performed 425 studies on different circuits and carried out 700 projects.

Local and European industry, which closely follow its innovations, are the first to benefit from the group’s successes by concluding technology transfer agreements.

For more information about the DEM group see