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- Zhang, S. N., et al.
(author)
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The high energy cosmic-radiation detection (HERD) facility onboard China's Space Station
- 2014
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In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 9780819496126
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Conference paper (peer-reviewed)abstract
- The High Energy cosmic-Radiation Detection (HERD) facility is one of several space astronomy payloads of the cosmic lighthouse program onboard China's Space Station, which is planned for operation starting around 2020 for about 10 years. The main scientific objectives of HERD are indirect dark matter search, precise cosmic ray spectrum and composition measurements up to the knee energy, and high energy gamma-ray monitoring and survey. HERD is composed of a 3-D cubic calorimeter (CALO) surrounded by microstrip silicon trackers (STKs) from five sides except the bottom. CALO is made of about 104 cubes of LYSO crystals, corresponding to about 55 radiation lengths and 3 nuclear interaction lengths, respectively. The top STK microstrips of seven X-Y layers are sandwiched with tungsten converters to make precise directional measurements of incoming electrons and gamma-rays. In the baseline design, each of the four side SKTs is made of only three layers microstrips. All STKs will also be used for measuring the charge and incoming directions of cosmic rays, as well as identifying back scattered tracks. With this design, HERD can achieve the following performance: energy resolution of 1% for electrons and gamma-rays beyond 100 GeV, 20% for protons from 100 GeV to 1 PeV; electron/proton separation power better than 10-5; effective geometrical factors of >3 m2sr for electron and diffuse gamma-rays, >2 m2sr for cosmic ray nuclei. R and D is under way for reading out the LYSO signals with optical fiber coupled to image intensified CCD and the prototype of one layer of CALO.
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| 2. |
- Zhang, S. -N, et al.
(author)
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Introduction to the high energy cosmic-radiation detection (HERD) facility onboard China's future space station
- 2017
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In: Proceedings of Science. - : Sissa Medialab Srl.
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Conference paper (peer-reviewed)abstract
- The High Energy cosmic-Radiation Detection (HERD) facility is one of several space astronomy payloads onboard China's Space Station, which is planned for operation starting around 2025 for about 10 years. The main scientific objectives of HERD are searching for signals of dark matter annihilation products, precise cosmic electron (plus positron) spectrum and anisotropy measurements up to 10 TeV, precise cosmic ray spectrum and composition measurements up to the knee energy, and high energy gamma-ray monitoring and survey. HERD is composed of a 3-D cubic calorimeter (CALO) surrounded by microstrip silicon trackers (STKs) from five sides except the bottom. CALO is made of about 7,500 cubes of LYSO crystals, corresponding to about 55 radiation lengths and 3 nuclear interaction lengths, respectively. The top STK microstrips of six X-Y layers are sandwiched with tungsten converters to make precise directional measurements of incoming electrons and gamma-rays. In the baseline design, each of the four side STKs is made of only three layers microstrips. All STKs will also be used for measuring the charge and incoming directions of cosmic rays, as well as identifying back scattered tracks. With this design, HERD can achieve the following performance: energy resolution of 1% for electrons and gamma-rays beyond 100 GeV and 20% for protons from 100 GeV to 1 PeV; electron/proton separation power better than 10-5; effective geometrical factors of >3 m2sr for electron and diffuse gamma-rays, >2 m2sr for cosmic ray nuclei. R&D is under way for reading out the LYSO signals with optical fiber coupled to image intensified IsCMOS and CALO prototype of 250 LYSO crystals.
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| 3. |
- Wang, G., et al.
(author)
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Integration of selective epitaxial growth of SiGe/Ge layers in 14nm node FinFETs
- 2016
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In: ECS Transactions. - : Electrochemical Society Inc.. - 1938-5862 .- 1938-6737. - 9781607685395 ; , s. 273-279
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Conference paper (peer-reviewed)abstract
- In this study, the process integration of SiGe selective epitaxy on source/drain and SiGe/Ge bilayers selectively epitaxy on replacement Si channel regions for 14 nm node FinFETs has been presented. The epi-quality, layer profile and strain amount of the selectively grown SiGe and Ge layers were also investigated by means of various characterization tools. A series of prebaking experiments were performed for different temperatures in order to in-situ clean the Si fins prior to the SiGe S/D epitaxy. It was also found that a SiGe layer with graded Ge content was deposited as the strain relaxed buffer (SRB) layer in the channel trench prior to the Ge layer filling in the small trenches to make the void defect free.
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| 8. |
- Cui, Daqing, et al.
(author)
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Immobilization of radionuclides on iron canister material at simulated near-field conditions
- 2009
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In: Scientific Basis for Nuclear Waste Management XXXII. - Warrendale, Pa : Materials Research Society. - 9781605110967 ; 1124
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Conference paper (peer-reviewed)abstract
- This work is a continuation of a long-term spent fuel leaching and radionuclides immobilization (by iron canister) experiment under simulated near-field conditions, in deoxygenated 2 mM NaHCO3 solution with 1 Gy/h γ irradiation. The corrosion of iron canister material was investigated by electrochemical and microanalytical methods. Significant amounts of radionuclides (U, Np, Tc, Sr) were found to be immobilized on the corrosion layer of iron canister material by using SEM-WDS and SIMS methods. The observation is useful for bettering our understanding of near-field chemical processes at earlier canister failure conditions.
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| 9. |
- Cui, D., et al.
(author)
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On the behaviour of spent fuel under simulated early canister-failure conditions
- 2006
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In: Proceedings of the 11th International High Level Radioactive Waste Management Conference, IHLRWM. - 0894486918 - 9780894486913 ; , s. 925-932
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Conference paper (peer-reviewed)abstract
- This paper reports on the results of a long term experiment on spent fuel leaching, canister corrosion and radionuclide immobilization under repository conditions corresponding to early canister failure. A γ-dose of 850 mGy per hour, and Ar-flushed synthetic groundwater were used. During the first 287 days, the fractions of inventory in aqueous phase per day (f/d) increased nearly constantly for each radionuclide (except for 100Mo), with higher fractions for fission products than for actinides. After this initial stage, iron, cast iron and copper coupons (of̃30 mm2 size) were inserted into the leaching vessel: the concentrations of 238U, 237Np and 99Tc decreased by 80%, 97% and 88% to relatively stable levels (500ppb, 0.2ppb and 0.6ppb respectively). 239Pu concentrations slightly increased to the level of PuO2 solubility (0.5ppb). The leaching process for Cs, Mo and 90Sr was not influenced by the added metals. The pH and Eh values and corrosion potential were measured. The polarization resistance (Rp) was obtained from fitting of electrochemical impedance spectra, and then corrected by the surface area of the sample. The corrosion current density Icorr was calculated according to the Stern-Gary relationship, and using the same Tafel constants (26 mV)for all samples, i.e., Icorr = 0.026/Rp. The momentary corrosion rates of iron, cast iron and copper (Cu/Cu+) calculated based on the Faraday's law are in reasonable agreement with the values estimated from observation of thickness of corrosion layers using SEM microscope. The copper coupon appeared much more stable against corrosion than the other coupons. The corrosion layer and radionuclides deposited on corrosion products on iron coupons were analyzed by SEM-EDS and SIMS. Si was found to be coordinated with all iron corrosion products; however, redox sensitive elements U and Pu were mainly coordinated with the inner layer of iron corrosion products even though some 1-2 μm sized uranium-silica rich particles were found on the outer side of the iron corrosion layer. The findings of this work contribute to an improved understanding of the behaviour of spent fuel under near field repository conditions.
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