New frontier technologies for the next generation of High Purity Germanium detectors
08 May 2024






The team from DL working on the project
​Applied physicists and engineers in the Technology Department of the Science and Technology Facilities Council (STFC) are developing a new detector technology which aims to revolutionise the use of High Purity Germanium (HPGe) sensors in hybrid pixel detectors. If proven, this disruptive technology will enable scientists to access innovative instrumentation with enhanced performance leading to superior-quality scientific results. This would also have long-term benefits in areas such as healthcare diagnostics.​

The distinctive properties of High Purity Germanium sensors

The team from RAL working on the project

High purity germanium is a semiconductor material with a very regular and uniform atomic mesh, also called lattice. This material has very attractive properties for the detection of X-rays. For instance, it is very efficient in absorbing X-rays and generates a fast and accurate signal when hit by these particles.

The distinctive properties of HPGe sensors mean they are able to observe materials with incredibly high accuracy.

However, HPGe sensors are limited in their applications because they require cryogenic cooling at temperatures as close as possible to the boiling point of liquid nitrogen (-196°C). This is where hybrid pixel detectors step in…

What are hybrid pixel detectors?

An illustration of the hybrid pixel detector
Hybrid pixel detectors are radiation detectors often used in particle physics, photon science, astronomy and medical applications. They cover the detection of a wide range of radiation types and intensities. They offer a unique combination of time, spatial and energy resolution, and are made of a sensor layer interconnected on top of a readout chip.

Hybrid pixel detectors use a variety of room temperature sensors like silicon sensors. It is currently a challenge to operate hybrid pixel detectors with HPGe sensors because of their cryogenic requirements.

Taking on the challenge of operating HPGe sensors in hybrid pixel detectors 

The conventional approach to think about hybrid pixel detectors operating with HPGe sensors is to design a cryogenic readout chip. The development of a cryogenic readout chip is a costly and risky endeavour, and to date this is a niche area still in development.

Common hybrid pixel detectors are designed to operate at room temperature. This is a mature and widespread technology.​

Therefore, the team at STFC started to think outside the box, and it came up with a concept called micro thermal-divider.

Creating a thermal divide in the smallest of spaces 

The groundbreaking work being done at STFC aims to enable the use of hybrid pixel detectors made of HPGe sensors and conventional readout chips designed for room temperature operations. The concept of a micro thermal-divider aims to overcome the need of dedicated and costly cryogenic readout chips for the operation HPGe sensors in hybrid pixel detectors. The successful development of a micro thermal-divider carries the potential to popularise the use of HPGe sensors, an attractive material offering a leading performance for X-ray detection.

Deploying a micro-thermal divider in hybrid pixel detectors aims to insulate the sensor from the heat generated by the read-out chip and provide direct cooling to the sensor.

The proposal involves a micro-thermal divider that needs to control a change in temperature of around 130°C over a distance less than half millimetre. This is extremely challenging!

Designing a micro thermal-divider

Multiple constraints are influencing the design of the thermal divider. The physical properties of materials and manufacturing processes must be considered as this will impact the thermal and electrical conduction between the sensor and the readout chip. Furthermore, the way the materials react to temperature variations needs to be considered. Materials will expand and contract to different extents based on their properties, so the correct materials need to be selected in order to match their thermal expansion or contraction and avoid mechanical issues. 

Successful first attempts

An early prototype of the micro thermal-divider has been created by the STFC team. The prototype uses a series of mock-up components and preliminary assembly processes.

The results are very encouraging! It was proven that the early prototype was able operate within the temperature requirements set by the cryogenic HPGe sensor and the room-temperature readout chip.

Further prototypes will be built in the coming months with the final parts. The team is overcoming the technical challenges related to the creation of a new technology, and learning day-after-day how to build a functional prototype.

Protecting intellectual property (IP) of innovative ideas

New frontier technologies are at the heart of the 4th industrial revolution. It is important in a knowledge-based economy to protect the intellectual capital of an organisation and of new discoveries.

Elizabeth Bain, STFC’s Head of IP and Licensing, is excited about the work being done to develop a micro thermal divider.

She says: “This micro thermal divider could have far-reaching impacts by enabling the use of HPGe in a range of important applications such as scientific instrumentation and medical diagnostics.

STFC works to ensure that valuable IP assets like this are protected and exploited to provide a positive economic impact and for the benefit of society. STFC has successfully licensed its patented technologies into a range of high-impact products and services, and we are very excited to see what developments this EPSRC-funded project brings to the STFC IP portfolio.”

This project is funded thanks to the UKRI-EPSRC grant “High-risk speculative engineering and ICT research: New Horizons" (EP/X017494/1).

This article was originally shared by STFC on LinkedIn.​