Researchers at the National Institute of Standards and Technology (NIST) have published results & # 39; tests suggest that a promising class of & # 39; sensors can & # 39; & # 39 used in environments of & # 39; high radiation and to advance important medical applications, industrial and & # 39; research.
The photonic sensors transmit information in light of current rather than & # 39; electricity in the wires. Can measure, transmit and manipulate streams & # 39; photon, typically through & # 39; optical fibers, and are used to measure pressure, temperature, distance, magnetic fields, environmental conditions and more.
They are attractive because of their small size, the low & # 39; energy consumption and tolerance of & # 39; Environmental variables such as mechanical vibration. But the general consensus was that high levels of & # 39; radiation modify their optical properties of silicon, leading to incorrect readings.
So NIST, which has been a world leader in & # 39; most of photonics research, has launched a program to answer those questions. The test results indicate that the sensors can be adapted for measuring radiation dose in both industrial applications and clinical radiotherapy. The results of & # 39; first lap & # 39; their testing are reported Nature Scientific Reports.
Specifically, the NIST results suggest that the sensors can be used to track the levels of & # 39; ionizing radiation (b & # 39; high enough energy to alter the structure of & # 39; atoms) used in the irradiation a & # 39; food to destroy germs and sterilizing & # 39; Estimated annual medical devices to market & # 39; $ 7 billion in the US alone. The sensors also have potential applications in medical imaging and therapy, which together are projected to account for about $ 50 billion in annual value worldwide by 2022.
"When we looked publications on the subject, different laboratories have dramatically different results", said project scientist left Zeeshan Ahmed, which is part of Project & # 39; dosimetry of Photonics & # 39; NIST and leader of the project thermometry of Photonics & # 39; the NIST. "This was our main motivation to do our experiment."
"Another motivation was the growing interest in the use of & # 39; photonic sensors that could function with & # 39; precisely in & # 39; very harsh environments, such as near nuclear reactors, where radiation damage is a concern key ", said Ahmed. "In addition, the space industry must know how these devices function f & # 39; & # 39 environments; high radiation", said the work of the project scientist Ronald Tosh. "They bring harmful or not? X & # 39; is this study shows that for a certain class of & # 39; and radiation devices, the damage is negligible."
"We found that the silicon photonic devices coated with oxide can withstand exposure to radiation up to 1 million gray," said project leader of Dosimetry photonics Ryan Fitzgerald, using the SI unit absorbed radiation. Grease one representing one & # 39; of & # 39 joules; energy absorbed by a kilogram of & # 39; mass, and one corresponding to 10,000 gray chest X-rays. This is roughly what the sensor receives f & # 39; nuclear power plant.
"It ceiling & # 39; what our customers care about calibration," said Fitzgerald. "So devices can be powered by & # 39; & # 39 reliable way in; levels & # 39; industrial or medical radiation which are hundreds or thousands of & # 39; lower times." The irradiation of & # 39; food, for example, ranges from a few hundred to a few thousand & # 39; gray, and typically is monitored by its effects on pellets & # 39; alanine, an amino acid change atomic properties when exposed to ionizing radiation.
To determine the effects of radiation, the NIST researchers exposed two types of & # 39; silicon photonic sensors for hours & # 39; gamma radiation from cobalt 60, a radioactive isotope. In both types & # 39; sensors, small variations in their physical properties change wavelength light that travels through them. By measuring those changes, the devices can be used as very sensitive thermometers or strain gauges. This remains & # 39; & # 39 by f; extreme environments such as space or nuclear reactors flight, only if they continue to function well under exposure to ionizing radiation.
"Our results show that these photonic devices are robust in & # 39; circles & # 39; even extreme radiation, suggesting that could also be used to measure radiation through its effects on the physical properties of & # 39; irradiated device ", said Fitzgerald. "This should come as good news for the manufacture of & # 39; the United States, which is ħerqanha to serve the huge market and growing for accurate delivery & # 39; radiation at & # 39; levels & # 39 very small duration. in sterilization of medical equipment and irradiation & # 39; food. "
They will also be a & # 39; great interest to clinical medicine, where doctors strive to treat other cancers and conditions with the lowest effective levels & # 39; Radiation focused on smaller dimensions to avoid affecting tissue b & # 39; his health, including electronic rays, protons and ions. Achieving & # 39; that objective requires sensors & # 39; Radiation b & # 39; extraordinarily high sensitivity and spatial resolution. "Eventually, we hope to develop on chip scale devices for industrial and medical applications can determine dose gradients absorbed at distances in the range of & # 39; micrometers and b & # 39; so provide unprecedented measurement detail", said work project scientist Nikolai Klimov. Micrometer is millions & # 39; m. Human hair is & # 39; about 100 micrometers wide & # 39 ;.
The team results can & # 39; have major implications for new medical therapies that employ extremely narrow beams & # 39; Protons or carbon ions and processes & # 39; medical sterilization using ray & # 39; electron b & # 39; low & # 39; energy. "Our sensors are naturally small and flat scale," said Fitzgerald. "The current dosimeters are on the order of & # 39 millimeters to centimeters, which can give an incorrect reading to areas vary on those dimensions."
In the next stage of the research, the team must check matrix & # 39; sensors simultaneously in & # 39; identical conditions to see if the dose variations over short distances can be solved.
Sensors & # 39; magnetic field & # 39; Hall effect for high temperatures and environments & # 39; radiation & # 39; damage
Zeeshan Ahmed et al, Evaluation of the hardness of the radiation Silicon photonic sensors, Scientific Reports (2018). DOI: 10.1038 / s41598-018-31286-9