Sources: Benjamin Montag, 785-532-6480, bmontag@k-state.edu;
Kyle Nelson, 785-532-2707, knelson1@k-state.edu;
Steven Bellinger, slb3888@k-state.edu;
and Michael Reichenberger, mar89@k-state.edu
Hometown interest for:
Manhattan and Mount Hope, Kan.; and Kearney and Lincoln, Neb.
News release prepared by:
Tyler Sharp, 785-532-2535, tmsharp@k-state.edu;
and Jennifer Tidball, 785-532-0847, jtorline@k-state.edu

Thursday, Sept. 22, 2011

SMART SCIENCE: STUDENT RESEARCH HELPS DEVELOP NEW RADIATION DETECTORS

MANHATTAN -- To many people, neutrons are merely known as particles without an electric charge. For student researchers in Kansas State University's Semiconductor Materials and Radiological Technologies Laboratory, or SMART Lab, neutrons are crucial for breaking new ground in radiation detection.

Kyle Nelson, doctoral student in nuclear engineering, Lincoln, Neb., splits his time between two types of detectors. His research with electro-optic radiation detectors remains relatively new. The device's limitations are unknown because of this fact. The detector does have a big advantage compared to its counterparts: better preservation of electronics.

Radiation detectors typically give off a pulse of electricity that is subsequently analyzed to determine the amount of radiation. Throughout this process, a varied amount of electronics are attached to the radiation sensor. High radiation levels can damage the electronics. But in an electro-optic detector electronics aren't attached to the crystal. Rather, the crystal is present in the radiation field and all electronics are separate.

Nelson's multi-wire gas tube detectors present other advantages. Helium-3, a nonradioactive isotope, readily absorbs neutrons. But the amount of the isotope is limited. The multi-wire gas tube detectors create an alternative.

These detectors include thin cuts of saturated foam -- memory foam saturated by lithium fluoride. Lithium-6 functions as the substitute for Helium-3 for absorption of neutrons. The cuts of foam are placed between multiple anode wires. Each anode wire is about a quarter of the thickness of a human hair. The anode wires are coupled with a large voltage of between 500 volts to 1,500 volts. When the lithium absorbs the neutron it splits into two particles. The particles deposit energy in the gas and the voltage across the wire collects that energy and deposits it in the gas in the form of a small pulse.

Aerogel, a low-density manufactured material, is also included in the detectors. Nelson would like to combine the aerogel with boron-10 to create an elemental boron aerogel. Aerogel can be comprised to include boron-10 or lithium-6 as both have the ability to absorb high amounts of neutrons. Using a lithium-6 foil and placing each at the same spacing as the foam and the aerogel could make a high-efficiency neutron detector, Nelson said.

The detectors would be primarily used for national security purposes.

Nelson's work on the foam and aerogel project is for his dissertation. He was recently awarded $1.2 million from the Defense Threat Reduction Agency for over three years. The research will begin soon.

Steven Bellinger, doctoral student in nuclear engineering, Manhattan, has been involved with neutron detector research in the SMART Laboratory since 2005. His doctoral research has focused on improving solid-state microstructured semiconductor neutron detectors and building them into larger arrays. He also has been building neutron sensors into more specialized pieces of equipment, including a neutron spectrometer.

Neutron spectroscopy, or the art of measuring the energy of a particle, is difficult because it's not easy to measure the energy of a neutron, which is a directly nonionizing form of radiation. But the spectrometer that Bellinger has designed may help with the challenge of measuring and analyzing the energy of a neutron from its source.

The spectrometer works by setting neutron detector arrays in a stack. High-density polyethylene is placed between each sensor in the stack and moderates the neutrons depending on the amount of kinetic energy of the neutron. If the neutron has more energy, sensors deep in the stack will register more counts while neutrons of less energy will register shallower in the stack. By doing this, the device is able to measure the energy of the neutron from an unknown source, which can help to identify the source.

In May, Bellinger received the K-State Alumni Association's Anderson Graduate Award for Service and Leadership for his research and scholarly achievements.

Benjamin Montag, doctoral student in nuclear engineering, Kearney, Neb., has been working on solid-state neutron detection devices as well. Montag's efforts have recently been concentrated on finding lithium ternary compounds for neutron detection with Michael Reichenberger, senior in nuclear engineering, Mount Hope, Kan. Incorporating lithium into a crystalline structure allows for the production of a small semiconducting device that has a high efficiency for thermal neutrons.

The device has its own advantages and disadvantages. While demand has remained constant for the devices, there are limitations to their development. Many of the ternary compounds Montag is working on are high temperature materials and have high melting points. This creates challenges for growing single crystals. Instead of growing them through conventional methods, many people choose alternatives, such as solution growth. As a result, dirty and noisy devices are produced. Montag has been collaborating with Douglas McGregor, professor of nuclear engineering and SMART Lab director, on this research since September 2008. The duo was awarded a grant from the National Nuclear Security Administration for $698,040 for three years of research. Montag anticipates receiving a renewal for a fourth year of research.

Upon completion, the students' various detectors will aide several different industries. Radiation detectors are used for medical imaging, national security and oil well logging as well as the automotive industry.

"Radiation detection is used if you want to see something that cannot be seen with the naked eye," Nelson said. "With oil well logging you can't tell the density of the rock by using a camera, but you can using radiation detection. Any type of measurement you want to know you can typically do with radiation and radiation detectors."