Supporting detector development for the upcoming Electron-Ion Collider

The Science and Technology Facilities Council ( STFC )'s Technology Department is working with colleagues from STFC Particle Physics Department to develop key detector technology for the upcoming Electron-Ion Collider.

The Electron-Ion Collider (EIC) is a new particle accelerator developed by scientists at Brookhaven National Laboratory, located in New York.

The circular collider will be the first to feature two ring-shaped accelerators with polarised beams: one producing a beam of polarised electrons and the other a high-energy beam of polarised protons or ions.

When these electron and ion beams smash together at a high energy and high frequency, they will produce scattered particles (known as quarks and gluons) which will be collected as data by at least one large-acceptance detector.

The detection of these particles will enable scientists to observe how quarks and gluons, which are found inside hadrons, are distributed and how they move and interact with one another.

The facility is also expected to revolutionise our understanding of the strong interaction, which governs the behaviour of atomic nuclei and accounts for more than 99% of the visible mass of the universe.

The STFC Technology Department is working on two of the UK EIC R&D detector project’s three work packages: developing MAPS technology for a central tracking array and silicon pixel-based detector arrays to tag electrons scattered after collision.

The department’s work is supported in part by the £2.9M funding UKRI-STFC has provided to ensure that the UK leads the development of the cutting-edge detector technology the collider requires.

From mobile phones to ground-breaking physics

MAPS, or Monolithic Active Pixel Sensors, are image sensors, not dissimilar to those commonly found in mobile phones, that convert visible light into an electronic image.

Invented in the early 90s, they have several advantages over existing devices; they are inexpensive to build, have a low mass, and can operate at high speeds with relatively low power consumption.

They also represent a promising avenue for the EIC’s detector technology, after being identified by a UK-led option analysis as the best technology capable of satisfying the collider’s particle tracking requirements.

The application of MAPS to the EIC will also benefit from the ongoing development of ITS-3: an upgraded vertex detector developed for ALICE (A Large Ion Collider Experiment) at CERN - also based on MAPS technology.

At Rutherford Appleton Laboratory (RAL), the Technology Department’s CMOS Sensor Design Group is designing the different IPs needed for the high-speed communication channels between the MAPS and the external world.

In addition to the design effort, STFC is providing technical support to Brookhaven’s design teams, while working closely on the development of the ITS3 sensor.

At Daresbury Laboratory (DL), Technology’s Nuclear Physics team are working with the Detector Systems Group to characterise the detector’s sensor modules before and after X-ray radiation.

This will inform scientists of the minimum energy threshold that the particles need to lose in the detector to have a chance to observe them.

The group is also responsible, along with the DL Projects and Mechanical Engineering Group, for producing the conceptual design of the central inner tracker array.

The EIC’s MAPS work package is led by the University of Birmingham, in collaboration with teams based at STFC’s Rutherford Appleton and Daresbury Laboratories, and the universities of Brunel, Lancaster, and Liverpool.

Nicola Carlo Guerrini , Technology's CMOS Sensor Design Group Leader, said:

“We are extremely excited to work on an innovative project like the EIC. MAPS technology is more and more in demand for high-end scientific applications and the group’s skills and experience are a very good match for the project requirements. The EIC is also an excellent opportunity to strengthen our links with the international particle physics community.”

The timeline of Timepix

Medipix chips are a family of pixel detector readout chips developed by CERN, representing one of the organisation’s most successful technology transfer cases.

The first Medipix chip was produced in the 1990s by the Medipix1 Collaboration, based on technology developed to address the particle tracking needs of the Large Hadron Collider.

The organisation’s next three collaborations, aptly named Medipix2, Medipix3, and Medipix4, have produced technologies with applications across medical imaging, space dosimetry, material analysis and education.

One of the technologies produced by the collaborations, specifically Medipix2, is known as Timepix.

Timepix represents an evolution of the original Medipix technology, with three modes of operation and applications in astrophysics, radiation monitoring, electron microscopy, and more.

This technology, which provides position, time, and energy loss measurements, will be applied to the EIC’s electron tagger. It will provide a precise measurement of the electron scattering angle after collision with the ion beam, which will reveal detailed structural properties of the ion.

Supporting the application of this technology, the Technology Department’s Nuclear Physics team are responsible for designing and building a bespoke data readout electronics and data acquisition prototype using the third generation of Timepix chips.

The prototype will be used to demonstrate the suitability of Timepix-based detectors as electron taggers before deploying this solution at the EIC. It is anticipated that the fourth generation of Timepix chips will be then available and used for the construction of the final device.

This work package is being led by the University of Glasgow, working closely with Technology’s Nuclear Physics Group and members of the CERN Timepix4 collaboration.

Marc L. , Technology’s Nuclear Physics Group Leader, said

“It’s a very exciting time. By colliding polarised electron and ion beams, the EIC will be a new unique research facility, which will shed light on the forces binding protons and neutrons together to form nuclei. We are delighted to participate in the development of the instrumentation that will enable new scientific discoveries at this facility.”

Providing answers to the mysteries of the Universe

According to the International Atomic Energy Agency, there are more than 30,000 accelerators in use around the world. So, why build another?

The answer to this question relates to one of the fundamental goals of nuclear physics – understanding how tiny particles known as quarks and gluons relate to one another.

If you could take an object and break it down into its constituent parts, from molecules to atoms and so on, you would eventually get down to quarks.

Quarks are elementary particles (they can’t be broken down further) that, when bound together by gluons, form a complex structure within protons and neutrons.

Even though the complex interplay between quarks and gluons accounts for more than 90% of the mass of visible matter in the universe, scientists still have a lot of unanswered questions about the tiny particles.

Scientists at Brookhaven hope that the EIC will act as a “novel tool for exploring this inner microcosm”, delving deeper into the 3D structure of protons and nuclei, gluon saturation and the colour glass condensate, the mystery of proton spin, and quark and gluon confinement.

In addition to providing the opportunity to answer field-defining physics questions, the EIC will also utilise the skills of field experts to drive forward advances in accelerator, particle detector, and computational technologies.

Just as the technology in development for ALICE’s ITS3 is being applied to the EIC’s detector development, the innovations derived from working on the collider will be harnessed in other fields of study.

The Electron-Ion Collider is set to begin construction in 2024, with a goal of collider operation in the 2030s. To learn more about the science behind the Electron-Ion Collider, please visit Brookhaven’s website.