Supporting Image
Nov 5, 2020 0    
Detecting neutron radiation
The Adventures of Solar Neutrons

Neutron radiation from the sun can damage satellites and harm astronauts in space. Nuclear devices on Earth also emit neutron radiation. This makes neutron radiation detection an important issue for the space program, satellite communications, and national defense. But unlike electrons and protons, neutrons don’t have any electric charge. Neutrons can pass through many kinds of solid objects without being scattered or absorbed. This makes it difficult to build devices to detect them, so we need special materials that absorb neutrons and leave a measurable signature when they do.

In the past, most neutron detectors used helium-3. There is now a worldwide helium shortage, so we need to research different materials to detect neutron radiation. But neutrons from space collide with particles in Earth’s atmosphere, making it difficult to measure neutron radiation signals. To get around this difficulty, researchers at the University of Nebraska-Lincoln are studying the effects of solar neutron radiation on two types of materials on the International Space Station (ISS), using detectors made of very stable compounds that contain boron-10 and lithium-6.

Boron-10 and lithium-6 are two special isotopes of the elements boron and lithium that readily absorb neutrons far better than most other elements. When they do, they fragment into highly energetic ions that leave behind a track of damage and can create a charge pulse in a semiconductor device (Fig. 1). The UNL Detector for the Analysis of Solar Neutrons (DANSON) experiment consists of 17 lithium tetraborate (Li6B4O7) crystals and five boron carbide (B2C10HX) semiconducting diodes. The boron carbide diodes measure the charge pulses created when the materials absorb neutrons, and the lithium tetraborate crystals will have damage tracks in their crystal structures that we can “see” using fluorescence, x-ray diffraction, and electron spin resonance (a technique similar to magnetic resonance imaging, or MRI).

The DANSON experiment’s lithium tetraborate crystals and boron carbide diodes were encased in a neutron-moderating polycarbonate, which is a type of plastic (Fig. 2). Since neutrons from the sun are too energetic to be “caught” by the detectors, we had to reduce their energy first. The neutron moderator “steals” energy from neutrons as they pass through the material, a little bit at a time, until they have low enough energy to be stopped by one of the detectors. Placing the detectors at different depths allows us to determine the energy of the neutron radiation we capture—we can infer that neutrons captured deeper in the moderator must have had higher starting energy, since they were able to penetrate further into the material.

Now that the DANSON experiment has returned from the ISS, we are looking for radiation damage to the structure of the crystals (Fig. 3) and comparing the electronic characteristics of the diodes from before and after their journey. We hope that what we learn with this experiment will help to advance the development of small, effective neutron detectors for use on Earth and in space. By examining the distribution of neutron captures in our moderator, we also hope to catch a glimpse into the nuclear fusion processes that fuel our sun!

Fig. 1 (Click to enlarge). In capturing neutrons, a boron carbide semiconductor creates reaction products that produce measurable charge pulses.
Fig. 1 (Click to enlarge). In capturing neutrons, a boron carbide semiconductor creates reaction products that produce measurable charge pulses.
Fig. 2 (Click to enlarge). The DANSON moderator cube diagram and photo. By encasing the detector elements in a neutron-moderating plastic, we can
Fig. 2 (Click to enlarge). The DANSON moderator cube diagram and photo. By encasing the detector elements in a neutron-moderating plastic, we can "slow down" the neutrons enough for the detectors to capture them.
Fig. 3 (Click to enlarge). X-ray crystallography allows us to study the structure of various kinds of crystals by looking at the patterns light makes when we shine it through the crystal. This example shows one type of pattern that can be produced by shining an x-ray beam through a crystal onto a special screen.
Fig. 3 (Click to enlarge). X-ray crystallography allows us to study the structure of various kinds of crystals by looking at the patterns light makes when we shine it through the crystal. This example shows one type of pattern that can be produced by shining an x-ray beam through a crystal onto a special screen.
TAGS: #crystals    #neutrons    #radiation    #semiconductors    #spin    
 
SHARE THIS POST:

Related Posts

05/19
Supporting Image
Supporting Image
Electric Crystals, Part 3

Students make paper models of crystal unit cells and build a large crystal structure together while reflecting on the role of symmetry in crystal formation. This lesson is part 3 of a 4-part student-driven, lecture-free series, in which students will do card sorts, build hands-on models, solve engineering design puzzles, and more!

0 0    
05/18
Supporting Image
Supporting Image
Electric Crystals, Part 1

Crystals aren't magic, but they are amazing! In this engaging, comic-driven lesson, students do individual and group-based activities to understand the characteristics of crystals (like quartz) versus amorphous solids (like glass). This lesson is part 1 of a 4-part student-driven, lecture-free series in which students will do card sorts, build hands-on models, solve engineering design puzzles, and more!

0 0    

More Funsize Research

11/21
Supporting Image
Supporting Image
Nanoscale fluid mechanics

We think we're pretty familiar with how ordinary liquids behave, but it turns out that some of the basic things we know are no longer true when we look at these liquids on short enough length scales and fast enough time scales. The liquids start to behave more like solids, pushing back when you push on them, and slipping across solid surfaces instead of being dragged along. Click to ride the tiny-but-mighty new wave of nanofluidics!

0 0    
07/25
Supporting Image
Supporting Image
Ferroelectric hafnia

Ferroelectric materials generate electric fields that move charges around, just as a bar magnet produces a magnetic field that moves magnets around. Ferroelectric materials can be used for data storage to make electronics more energy efficient, but they don’t always play well with the silicon technology used in devices like phones and computers. HAFNIA TO THE RESCUE! Click to learn more.

0 0    
04/20
Supporting Image
Supporting Image
Fluids and filling

You take a pristine-looking Oreo from a package of seemingly identical sandwich cookies, and you decide to open it up to eat the creme filling first. You gently twist the cookie apart without breaking the chocolate wafers, but the creme sticks to one side only. Why? Happily, the physics of fluids helped two MIT students solve this delicious mystery. Read on to find out what they learned, and how you can test their results at home.

0 0    
05/12
Supporting Image
Supporting Image
Laser memory

Instead of pencil, paper, and eraser, we can use combinations of lasers and magnetic materials to write, read, and and erase information by varying the temperature and magnetic field. Here we apply our laser "pencil" to magnetic "paper" to write the letter “N” (Go Huskers!!). This technique allows us write, erase, and rewrite tiny magnetic memories like those found in your computer hard drive and other devices. Click to learn how it works!

0 0    
04/20
Supporting Image
Supporting Image
Thermalizing nanowires

It’s a hot summer day. You desperately want something cold to drink, but unfortunately, your bottle of root beer has been sitting in a hot car all day. You put it into a bucket full of ice to cool it down. But it’s taking forever! How, you wonder, could you speed the process up? The same question is important for understanding how electronic devices work, and how we can make them work better by controlling the temperature of the electrons that power them. Read on to find out what a bottle of root beer in a cooler full of ice and a nanowire in a vat of liquid helium have in common!

0 0    
02/23
Supporting Image
Supporting Image
World's smallest diode

Diodes, also known as rectifiers, are a basic component of modern electronics. As we work to create smaller, more powerful and more energy-efficient electronic devices, reducing the size of diodes is a major objective. Recently, a research team from the University of Georgia developed the world's smallest diode using a single DNA molecule. This diode is so small that it cannot be seen by conventional microscopes.

0 0    
02/01
Supporting Image
Supporting Image
Liquid magnetism
by Robert Streubel, Scott Schrage

You may have heard that there are three main phases of matter: solids, liquids, and gases (plus plasma if you want to get fancy). Liquids can take virtually any shape and deform instantly. Solid materials possess interesting electronic and magnetic properties essential to our daily life. But how about designing rigid liquids with magnetic properties? Impossible? Not anymore. Click to learn more!

0 0    
11/05
Supporting Image
Supporting Image
Building a better computer
by Peter Dowben, Jocelyn Bosley

Scientists are working to develop electronic devices that store and process information by manipulating a property of electrons called spin—a research area aptly known as spintronics. The semiconductors we are developing will not only be faster and cheaper than those used in conventional devices, but will also have more functionality.

1 1    
11/05
Supporting Image
Supporting Image
Good vibrations

Materials that are absolutely perfect—in other words, materials that contain no defect of any kind—are usually not very interesting. Imagine being married to a saint: you would quickly be bored out of your mind! Defects and impurities can considerably change many properties of materials in ways that allow a wide range of applications.

0 0    
11/05
Supporting Image
Supporting Image
Secrets of semiconductors

Semiconductors are materials with properties intermediate between metals and non-conducting insulators, defined by the amount of energy needed to make an electron conductive in the material. The non-conducting electrons occupy a continuum of energy states, but two of these states (the “heavy hole” and “light hole”) are nearly identical in energy. The heavy hole is easy to observe and study, but the light hole eludes most observers.

0 0    
11/05
Supporting Image
Supporting Image
Locking up electrons

Solids are generally divided into metals, which conduct electricity, and insulators, which do not. Some oxides straddle this boundary, however: a material's structure and properties suggest it should be a metal, but it sometimes behaves as an insulator. Researchers at the University of California, Santa Barbara are digging into the mechanisms of this transformation and are aiming to harness it for use in novel electronic devices.

0 0    
11/05
Supporting Image
Supporting Image
Nanomagnetism

You may know that the media used in magnetic recording technologies, such as computer hard drives, are made of millions of tiny nanomagnets. Each nanomagnet can be switched up or down to record bits of information as ones and zeros. These media are constantly subjected to magnetic fields in order to write, read, and erase information. If you have ever placed a magnet too close to your laptop or cell phone, you know that exposure to an external magnetic field can disrupt information stored this way. Did you know that it is possible for the nanomagnets to "remember" their previous state, if carefully manipulated under specific magnetic field and temperature conditions? Using a kind of memory called topological magnetic memory, scientists have found out how to imprint memory into magnetic thin films by cooling the material under the right conditions.

0 0    
11/05
Supporting Image
Supporting Image
Slow reflection

Inside solids, the properties of photons can be altered in ways that create a kind of "artificial gravity" that affects light. Researchers at the University of Pittsburgh tracked photons with a streak camera and found that whey they enter a solid-state structure, they act just like a ball being thrown in the air: they slow down as they move up, come to a momentary stop, and fall back the other way. Studying this "slow reflection" will allow us to manipulate light's behavior, including its speed and direction, with potential applications in telecommunications and quantum computing technologies.

0 0    
11/05
Supporting Image
Supporting Image
Superfluid helium droplets

In a unique state of matter called a superfluid, tiny "tornadoes" form that may play an important role in nanotechnology, superconductivity, and other applications. Just as tornadoes are invisible air currents that become visible when they suck debris into their cores, the quantum vortices in superfluids attract atoms that make the vortices visible. Quantum vortices are so small they can only be imaged using very short-wavelength x-rays, however.

0 0    
11/05
Supporting Image
Supporting Image
Magnetic anisotropy

Would you rather have data storage that is compact or reliable? Both, of course! Digital electronic devices like hard drives rely on magnetic memory to store data, encoding information as “0”s and “1”s that correspond to the direction of the magnetic moment, or spin, of atoms in individual bits of material. For magnetic memory to work, the magnetization should not change until the data is erased or rewritten. Unfortunately, some magnetic materials that are promising for high density storage have low data stability, which can be improved by squeezing or stretching the crystal structures of magnetic memory materials, enhancing a material property called magnetic anisotropy.

0 0    
11/05
Supporting Image
Supporting Image
Detecting neutron radiation

Neutron radiation detection is an important issue for the space program, satellite communications, and national defense. But since neutrons have no electric charge, they can pass through many kinds of solid objects without stopping. This makes it difficult to build devices to detect them, so we need special materials that can absorb neutrons and leave a measurable signature when they do. Researchers at the University of Nebraska-Lincoln are studying the effects of solar neutron radiation on two types of materials on the International Space Station (ISS), using detectors made of very stable compounds that contain boron-10 and lithium-6.

0 0    

WRITE COMMENT

Go to Top