Computer Memory: New Material Could Dramatically Boost Data Storage, Save Energy

North Carolina State University engineers have created a new material that would allow a fingernail-size computer chip to store the equivalent of 20 high-definition DVDs or 250 million pages of text, far exceeding the storage capacities of today's computer memory systems.

Led by Dr. Jagdish "Jay" Narayan, John C.C. Fan Family Distinguished Professor of Materials Science and Engineering and director of the National Science Foundation Center for Advanced Materials and Smart Structures at NC State, the engineers made their breakthrough using the process of selective doping, in which an impurity is added to a material that changes its properties. The process also shows promise for boosting vehicles' fuel economy and reducing heat produced by semiconductors, a potentially important development for more efficient energy production.

Working at the nanometer level -- a pinhead has a diameter of 1 million nanometers -- the engineers added metal nickel to magnesium oxide, a ceramic. The resulting material contained clusters of nickel atoms no bigger than 10 square nanometers, a 90 percent size reduction compared to today's techniques and an advancement that could boost computer storage capacity.

"Instead of making a chip that stores 20 gigabytes, you have one that can handle one terabyte, or 50 times more data," Narayan says.

Information storage is not the only area where advances could be made. By introducing metallic properties into ceramics, Narayan says engineers could develop a new generation of ceramic engines able to withstand twice the temperatures of normal engines and achieve fuel economy of 80 miles per gallon. And since the thermal conductivity of the material would be improved, the technique could also have applications in harnessing alternative energy sources like solar energy.

The engineers' discovery also advances knowledge in the emerging field of "spintronics," which is dedicated to harnessing energy produced by the spinning of electrons. Most energy used today is harnessed through the movement of current and is limited by the amount of heat that it produces, but the energy created by the spinning of electrons produces no heat. The NC State engineers were able to manipulate the nanomaterial so the electrons' spin within the material could be controlled, which could prove valuable to harnessing the electrons' energy. The finding could be important for engineers working to produce more efficient semiconductors.

Working with Narayan on the study were Dr. Sudhakar Nori, a research associate at NC State, Shankar Ramachandran, a former NC State graduate student, and J.T. Prater, an adjunct professor of materials science and engineering. The research was sponsored by the National Science Foundation.

Into a New Country

Mac Kenzie’s team follows a well-established process when beginning work in a new country. The first step is coordinating with the U.S. Embassy to gain their approval and cooperation. “We sometimes meet with the ambassador of the country,” says Mac Kenzie, “and the economic officer may participate in our meetings with the country’s ministries.”

The Livermore team, plus GTRI’s Robinson or NNSA representative and Sandia employee Michael Itamura, meet with the staff and leadership of the relevant ministries. Together, this team gets “the lay of the land” during the weeklong initial visit to the country. The team works closely with the country’s regulators to locate and visit sites with large radiological sources, such as teletherapy machines used in cancer treatment, industrial irradiators, or instrumental calibrators.

Some radiological sources are well known to the team before they arrive in a country. Burkina Faso has an irradiator for sterilizing tsetse flies, which is helping to rid Sub-Saharan Africa of sleeping sickness in both people and livestock. (See the box below.) Mauritius currently has an inactive irradiator for Mediterranean fruit flies (medflies) but is obtaining a new one, for which it will need a radioactive source. Ghana has a food irradiator for promoting longer shelf life and is in the process of obtaining a new radioactive source for it. A hospital in Gabon has a machine for delivering radiation to treat cancer, but the machine’s radioactive source is depleted. The depleted source will be secured in place, and the country hopes to replace it in the future.

The team also visits locations with large accumulations of smaller sources, such as radioactive-waste storage facilities, mining sites, ports, and oil-drilling regions. Gauges and well-logging devices containing radioactive materials are more commonly present in these locations. In addition, if a country has a research reactor facility, the team may offer security upgrades for the facility.

The IAEA has established various threshold levels for different radionuclides. Consequently, not every radioactive source needs the same degree of attention. Radionuclides of particular interest are americium-241, which is widely used in industrial gauges; plutonium-238 and -239, which are well-known fissile materials; and californium-252, which is used in downhole well logging for oil exploration. Other common radionuclides include radium-226, which was used in medical applications in the past; cesium-137, which is found in moisture and density gauges, calibration devices, and industrial irradiators; and cobalt-60, which is used in radiation treatment for cancer. Also of interest are iridium-192, an industrial radioisotope used to locate areas of weakness in metal pipes, and strontium-90, which is used extensively as a radioactive source in radioisotope thermoelectric generators for powering lighthouses and in radiotherapy for some types of cancer.

Inventorying can be a challenge. “One country thought it had about 100 sources in their inventory, but they in fact had close to 400,” says Mac Kenzie. Often the problem is orphan sources. Some countries do not have regulators or regulations in place, or they have people who are still new to their jobs. “New regulators may understand the safety concerns of nuclear sources but are not fully aware of the threat of theft and the need for physical protection,” says Mac Kenzie.

Developing Indigenous Expertise
To assist countries with their own search efforts, GTRI offers a one-week “Search and Secure” workshop, which teaches local officials how to search for, locate, and identify orphan sources. Search equipment is provided based on a country’s needs. The workshop includes instruction on organizing and implementing a search for orphan sources, use of search equipment, and packaging and transportation of orphan sources to secure storage facilities. The workshop curriculum includes hands-on field training and exercises. GTRI may also offer workshop participants help in developing verified inventories by visiting suspected orphan-source locations in their country.

GTRI’s Search and Secure project was launched in 2004 and is closely coordinated with IAEA to avoid duplicating efforts and to maximize assistance in each country. A goal is to help countries develop their own indigenous capabilities for assessing orphaned and disused radiological sources. The project was first deployed in the republics of the former Soviet Union. Since 2004, equipment has been deployed in 30 countries, approximately 550 people have been trained, and thousands of orphan sources have been found.