MALTA3 the little detector chip built to handle big data
Next-gen particle accelerators will smash more particles together faster and generate more data than ever before. MALTA3 is the next-gen detector chip built to take the job on.
The Large Hadron Collider’s next big upgrade will see a huge increase in the number of particle collisions it produces, and new technology will need to be developed to make this possible. A key part of one of these new developments is currently being designed by the Science and Technology Facilities Council’s (STFC) Technology Department.
The High-Luminosity upgrade of the Large Hadron Collider (HL-LHC, or Hi-Lumi) is scheduled to begin colliding protons in 2026. When it does go online, HL-LHC will massively ramp up the collision rate of particles and, as such, CERN will require considerably upgraded detector systems to cope with its demands.
To meet these demands, CERN is collaborating with STFC to create a testbed sensor chip called MALTA3, which they hope will form the prototype for future high-luminosity particle colliders.
The high-particle rate problem
HL-LHC will generate four times the number of particle collisions than the current LHC. This increase in particles causes two problems for detector systems.
Firstly, detectors have to be able to accurately track particles in both space and time — both ‘where’ it is and ‘when’ it is in that position — and more particles generated means more particles that the detector has to be able to detect and track. This increase in particles also means that detectors will be subjected to a huge increase in radiation levels. In short, a detector has to be both sensitive to record all of this activity and tough enough to withstand the levels of radiation generated.
Secondly, if you massively increase the number of particles you are tracking and you increase the accuracy of that tracking, you also massively increase the amount of data you are generating. If more data is being generated at a greater rate than ever before, you need a detector capable of transmitting it.
The high-data rate solution
For the first problem of increased tracking and sensitivity, CERN had already developed the technology needed to cope with it. For the second, they turned to STFC’s Technology Department.
STFC’s Technology Department is a principal provider of technology and instrumentation for our programmes and facilities in the UK and overseas and specialises in developing solutions where no suitable technology precedent exists.
With the help of funding from STFC’s Centre for Instrumentation (CfI), a fund set up to finance the development of technology for future colliders, the Technology Department had already designed a testbed chip that CERN believed would fit the bill.
The STFC-developed chip provides the high-speed readout circuit needed to handle the very high particle hit rate and the ability to transmit the data from the chip without needing many hundreds of data links.
Existing data links utilised by CERN transmit data at the rate of about 40 megabits per second on a par with the average UK broadband speed. By contrast, STFC’s data link on MALTA3 can transmit data in the range of 4.3 gigabits per second (one gigabit is one thousand megabits) 100 hundred times faster.
Ease of integration
Imagine you had a sensor chip that was able to read and log millions of particle collision events, but you were unable to export the data fast enough through your existing transmitter. It would be like trying to empty a stadium full of people through a single turnstile — to empty the stadium quickly, you need to have tens or hundreds of turnstiles.
Likewise, to get the data off the chip you’d have to use multiple data lines. Unfortunately, to make a detector, you need thousands of chips and, if each of those chips had tens of data lines, you’d soon find yourself in quite the tangle if you tried to integrate it into your fancy new accelerator.
The fastest way to empty the stadium would be to develop a stadium that could swing open on one side and allow people to flood out. For the stadium, this would be an engineering impossibility, but this is effectively what the STFC chip allows the data to do — exit quickly through a single, or far fewer, outlets.
What is MALTA3?
Particle detectors work a little like the chips in a digital camera but, instead of detecting photons that interact with it, they detect the particle debris from particle collisions. In a digital camera, the photons are detected by pixels on the chip — the more pixels it has, the more photons it can read and the higher resolution image it can create.
Existing detector chips have to deal with relatively few particle interactions but upgrades like Hi-Lumi will generate so many particle interactions — many occurring simultaneously — that they would overwhelm an existing chip’s ability to track them.
On a detector chip like MALTA3 the ‘pixels’ are made up of silicon atoms arranged in a lattice. Each silicon ‘pixel’ creates an electrical charge when a particle interacts with them. There are multiple layers of silicone lattice meaning that, as it passes through and interacts with multiple ‘pixels’ in multiple layers, the particle’s path can be tracked.
MALTA3 is basically a detector chip that has more ‘pixels’, and more pixels means more particle interactions can be measured more accurately.
Testing the chip
The STFC Technology Department have worked with CERN over the last year to integrate the transmitter in MALTA3 and now the fully-featured chip is currently being fabricated and testing is expected to begin at CERN in early 2024.
The new technology could see applications far beyond that of particle physics because, as all types of sensors become more sensitive, the requirement to be able to export greater amounts of data faster and more efficiently can only increase. Thus, the STFC developed chip could find a use in applications as diverse as medical imaging and next-generation telescopes.
Story by: Ben Gilliland
Interested in particle physics? Want to know what next-gen particle accelerators might be looking for? Check out our feature exploring the search for physics beyond the standard model!
