Tag: Radiation

Transistors and NASA’s radiation paradox

Transistors and NASA’s radiation paradox

The nature of Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) present a fascinating paradox in space exploration. Their strength in radiation detection becomes their weakness in space operations, exposing an Achilles’ heel for NASA. Yet, these same devices monitor radiation doses received by humans – on earth and in space. 
 

These tiny transistors have transformed everything from consumer electronics to advanced scientific applications. They are essential components in radios, MP3 players and iPods, powered satellite communications and now drive the artificial intelligence age. Their unique ability to measure radiation by capturing changes in electrical characteristics when exposed to ionising radiation is critical in both space exploration and cancer treatment.  
 

Australia leads the development of MOSFET-based radiation detectors for radiation monitoring. In a recently published work, ANSTO scientists and collaborators showed how four MOSFETs can be used to precisely measure radiation doses that patients receive during Boron Neutron Capture Therapy (BNCT).

Ironically, this property that we rely on for measuring radiation nearly doomed NASA’s Europa Clipper mission, due to the risk of radiation damage compromising the operation of its MOFET-based systems. Understanding this dual interaction with radiation highlights the importance of innovative solutions in both space missions and healthcare. It is also a great example of how mission-based research impacts everyday life. 

The Versatility of MOSFETs 

MOSFETs are a key component in modern electronics. Following Moore’s Law, the number of transistors in a circuit has increased exponentially over time enabling more powerful and energy-efficient technologies. Companies like NVIDIA use billions of MOSFETs in their GPUs, such as the A100, which is the backbone of  high-performance AI systems. These transistors allow the efficient power management and rapid switching that is necessary for handling the complex operations in machine learning and AI applications,

In jointly published research, ANSTO and University of Wollongong (UOW) researchers used a Quad-MOSFET array to precisely measure radiation quality in boron neutron capture therapy (BNCT). Each MOSFET was coupled to a different moderator (material that interacts with radiation) and measures different energy levels to allow accurate radiation monitoring during treatment.  

Another example is the MOSkin dosimeter, developed at the Centre for Medical Radiation Physics at the University of Wollongong. MOSkin is a skin-mounted MOSFET device that provides real-time radiation dose measurements during radiotherapy. This technology is already being used in clinical settings to improve safety and accuracy in radiation treatments. 

MOSFETs in Space Exploration 

MOSFETs are integral to managing systems and instruments in spacecraft due to their efficiency and low power consumption. However, space environments, especially around Jupiter, expose these devices to intense radiation—a challenge NASA faced with the Europa Clipper mission.

The radiation delivers a harsh cocktail of ionising particles. This radiation can cause single event effects (SEE), where high-energy particles flip a MOSFET’s state from “on” to “off,” causing them to malfunction. It can also cause total ionising dose (TID) effects, a situation in which radiation slowly degrades the MOSFET’s performance by trapping charges and creating defects in the semiconductor material. 

Read more at ANSTO website

Electron bubbles modelled from X-ray laser data

Electron bubbles modelled from X-ray laser data

An international team of scientists uncovers a groundbreaking model for the effects of radiation in water systems

What happens when radiation hits water? This is a question that has an impact every time you get an X-ray at the doctor’s office, given you are mostly made of water. A team of theoretical physicists at DESY has worked on data taken by colleagues from Argonne National Laboratory in the US at the LCLS X-ray laser in California to get a better answer to this question. What they found may settle a controversy in physics about the presence of free electrons in water and how they behave at very short time scales: the electrons, unbound to atoms, become sequestered in bubbles in cage-like structures between individual water molecules. These findings are reported in the Journal of the American Chemical Society.

Free electrons are electrons that are not bound to atoms. In water that comes into contact with radiation, free electrons emerge from the water molecules as they ionise due to the radiation. How the electrons flow between the water molecules in this situation has been a topic of discussion for a longer time.

In their work at LCLS at the SLAC National Accelerator Laboratory, the experimental team, led by Argonne scientist Linda Young, saw odd signatures associated with the water molecules excited by lasers and imaged by the X-ray laser. They found structures among the molecules using X-ray absorption spectroscopy. In order to gain a better understanding of what these results meant, the experiment team turned to theoretical physicists in Hamburg.

A team led by DESY scientist Ludger Inhester of the Center for Free-Electron Laser Science examined the data and began making models from the data in coordination with the experimental team. Together their findings show that the free electrons in the water form bubble structures that are then caged in by water molecules, similar to how chemicals are solvated in water at the molecular level. In particular, the DESY team managed to show the process behind this solvation of electrons in the water and its parameters.

Read more on DESY website

Image: Using the X-ray laser LCLS in California, the experiment team, led by Argonne scientist Linda Young, could image the structures of the water molecules surrounding the electron bubbles. The theory team in Hamburg, led by CFEL senior scientist Ludger Inhester was able to model how the bubble itself behaved using the experiment team’s data.

Credit: DESY/ Arturo Sopena Moros

X-ray laser reveals how radiation damage arises

X-ray laser reveals how radiation damage arises

DOUBLE BOMBARDMENT EXPOSES THE DETAILED DYNAMICS OF HOW WATER MOLECULES BREAK APART

An international research team has used the SQS instrument at the European XFEL to gain new insights into how radiation damage occurs in biological tissue. The study reveals in detail how water molecules are broken apart by high-energy radiation, creating potentially hazardous electrically charged ions, which can go on to trigger harmful reactions in the organism. The team led by Maria Novella Piancastelli and Renaud Guillemin from the Sorbonne in Paris, Ludger Inhester from DESY and Till Jahnke from European XFEL presents its observations and analyses in the scientific journal Physical Review X.

Since water is present in every known organism, the so-called photolysis of water is often the starting point for radiation damage. “However, the chain of reactions that can be triggered in the body by high-energy radiation is still not fully understood,” explains Inhester. “For example, even just observing the formation of individual ions and radicals in water when high-energy radiation is absorbed is already very difficult.”

Read more on the XFEL website

Image: After the absorption of an X-ray photon, the water molecule can bend up so far that after only about ten femtoseconds (quadrillionths of a second) both hydrogen atoms (grey) are facing each other, with the oxygen atom (red) in the middle. This motion can be studied by absorbing a second X-ray photon.

Credit: DESY, Ludger Inhester