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Cosmogenic nuclide

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5: Age-dating old groundwaters Silicon Production of 32Si Sampling and analyzing groundwater for 32Si Dating groundwater.

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To construct large-scale silicon electro-optical switches for optical interconnections, we developed a method using a limited number of power monitors inserted at certain positions to detect and determine the optimum operating points of all switch units to eliminate non-uniform effects arising from fabrication errors. We also introduced an optical phase bias to one phase-shifter arm of a Mach—Zehnder interferometer MZI -type switch unit to balance the two operation statuses of a silicon electro-optical switch during push—pull operation.

The losses were Accompanying the rapid increases in the numbers of data centres DCs and high-performance computers HPCs , optical switches are highly demanded for the construction of DC and HPC optical interconnection networks for increasing the speed of data exchange and reducing power consumption 1 , 2 , 3. These switches are also key devices for building all-optical telecommunication networks. Silicon-integrated optical switches, together with other silicon photonic devices based on silicon-on-insulator SOI substrates and complementary metal—oxide—semiconductor CMOS -compatible process technologies, are widely regarded as the most promising devices for applications in data communications and telecommunications.

They are compact, have a low power consumption and low cost, and are fit for large-scale monolithic integration. Many studies of silicon switches have been conducted 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , Compared to a thermal-optical TO switch, a silicon electro-optical EO switch with a nanosecond switching speed is more desirable since it can switch sufficiently fast to work as an optical packet switch in data communications, especially in HPCs, as well as in telecommunications.

Cosmogenic nuclide

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Silicon is produced in the atmosphere by cosmic-ray spallation of 40Ar (Lal et al., ). It decays to 32P with a half-life of ^ 6 yr. (Morgenstern et al., ),​.

Detector sensitivity and purification challenges have limited published 32 Si sediment dating studies. Targeting this age range can provide geochronological reconstructions of paleoindicators that identify recent human and climate-induced shifts in coastal areas. We are preparing detectors and kilogram-scale sample preparation techniques for such a study of Puget Sound sediments.

This work considers the impact of background on counting time and 32 Si age-dating reach. Design and performance of new low-background, gas-proportional beta counters to measure 32 Si via 32 P are discussed. This is a preview of subscription content, log in to check access.

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Cosmogenic nuclides (or cosmogenic isotopes) are rare nuclides (isotopes) created when a Some of these radionuclides are tritium, carbon and phosphorus Certain light (low Si, Spallation (Ar), min. Si, Spallation (Ar​) typical application. beryllium, 10, 1,,, exposure dating of rocks, soils, ice cores.

Cosmogenic nuclides or cosmogenic isotopes are rare nuclides isotopes created when a high-energy cosmic ray interacts with the nucleus of an in situ Solar System atom , causing nucleons protons and neutrons to be expelled from the atom see cosmic ray spallation. These nuclides are produced within Earth materials such as rocks or soil , in Earth’s atmosphere , and in extraterrestrial items such as meteorites.

By measuring cosmogenic nuclides, scientists are able to gain insight into a range of geological and astronomical processes. There are both radioactive and stable cosmogenic nuclides. Some of these radionuclides are tritium , carbon and phosphorus Certain light low atomic number primordial nuclides some isotopes of lithium , beryllium and boron are thought to have been created not only during the Big Bang , and also and perhaps primarily to have been made after the Big Bang, but before the condensation of the Solar System, by the process of cosmic ray spallation on interstellar gas and dust.

This explains their higher abundance in cosmic rays as compared with their ratios and abundances of certain other nuclides on Earth. This also explains the overabundance of the early transition metals just before iron in the periodic table; the cosmic-ray spallation of iron thus produces scandium through chromium on one hand and helium through boron on the other.

Radiocarbon Dating

Silicon has two stable isotopes and one cosmogenic isotope. The cosmogenic isotope 32 Si is used to determine surface exposure ages and erosion rates. It is also being investigated as a tracer of groundwater recharge. Currently this is not a tracer used beyond research applications and so no pricing data is available. It would be costly due to numerous difficulties:large sample size, rarity of use, and extremely sensitive detection requirements.

Origin return to top 32 Si Silicon has three stable isotopes: 28 Si , the most abundant

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A team of scientists from Purdue and Stanford universities has found that the decay of radioactive isotopes fluctuates in synch with the rotation of the sun’s core. The fluctuations appear to be very small but could lead to predictive tools for solar flares and may have an impact on medical radiation treatments. This adds to evidence of swings in decay rates in response to solar activity and the distance between the Earth and the sun that Purdue researchers Ephraim Fischbach, a professor of physics, and Jere Jenkins, a nuclear engineer, have been gathering for the last four years.

The Purdue team previously reported observing a drop in the rate of decay that began a day and half before and peaked during the December solar flare and an annual fluctuation that appeared to be based on the Earth’s orbit of, and changing distance from, the sun, Jenkins said. Jenkins and Fischbach collaborated with Peter Sturrock, a professor emeritus of applied physics at Stanford University and an expert on the inner workings of the sun, to examine data collected at Brookhaven National Laboratory on the rate of decay of the radioactive isotopes silicon and chlorine The team reported in the journal Astroparticle Physics that the decay rate for both isotopes varies in a day recurring pattern, which they attribute to the rotation rate of the sun’s core.

In general, the fluctuations that Jenkins and Fischbach have found are around a tenth of a percent from what is expected, as they’ve examined available published data and taken some measurements themselves. The team has not yet examined isotopes used in medical radiation treatments or for dating of ancient artifacts. What is key here is that what was thought to be a constant actually varies and we’ve discovered a periodic oscillation where there shouldn’t be one.

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thermal spring water in Jiaodong is ‰. Thermal spring water ages using δ 32Si dating method range from a to a. Keywords: silicon isotope, thermal​.

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