First charge collection and position-precision data on the medium-resistivity silicon strip detectors before and after neutron irradiation up to 2x10(14) n/cm(2)

Test strip detectors of 125 mu m, 500 mu m, and 1 mm pitches with about 1 cm(2) areas have been made on medium-resistivity silicon wafers (1.3 and 2.7 k Ohm cm). Detectors of 500 mu m pitch have been tested for charge collection and position precision before and after neutron irradiation (up to 2 x 10(14) n/cm(2)) using 820 and 1030 nm laser lights with different beam-spot sizes. It has been found that for a bias of 250 V a strip detector made of 1.3 k Ohm cm (300 mu m thick) can be fully depleted before and after an irradiation of 2 x 10(14) n/cm(2). For a 500 mu m pitch strip detector made of 2.7 k Ohm cm tested with an 1030 nm laser light with 200 mu m spot size, the position reconstruction error is about 14 mu m before irradiation, and 17 mu m after about 1.7 x 10(13) n/cm(2) irradiation. We demonstrated in this work that medium resistivity silicon strip detectors can work just as well as the traditional high-resistivity ones, but with higher radiation tolerance. We also tested charge sharing and position reconstruction using a 1030 nm wavelength (300 mu m absorption length in Si at RT) laser, which provides a simulation of MIP particles in high-physics experiments in terms of charge collection and position reconstruction, (C) 1999 Elsevier Science B.V. All rights reserved.

Two-color quantum well infrared photodetector simultaneously working at 10-14 mu m

We have demonstrated a two-color quantum well infrared photodetector (QWIP) exhibiting simultaneous photoresponse with cutoff wavelengths at 11.8 and 14.5 mu m, respectively. Strong photocurrent signals are observed at temperature of 77 K. The simultaneous two-color photoresponse is achieved by utilizing a simple design by broadening the width of the quantum well and selecting an appropriate doping density. The two peaks are attributed to the intersubband transitions from the ground state to the first excited state (bound state) and to the fifth excited state (continuum state), respectively.

金属溶剂萃取的热力学研究 1.Er(NO_3)_3-TB -C_6H_(14) 体系2.CuSo_4-氨化P_(50)-16H_(14)体系

本文在溶液理论的基础上，用纯热力学方法研究了中性磷萃取剂-金属体系（TBP-Er(no_3)_3）和氨化P_(50)-金属体系（P_(50)-cus04）的平衡计算模型。对于TBP体系有下列萃取平衡Er(NO_3)_3 (a) + 3TBP_((0)) <-> Er(NO_3)_3. 3TBP_((0))对于氨化P50体系，在萃取剂大量过量下有下的平衡Er(NO_3)_3 (a) + 3TBP_((0)) <-> Er(NO_3)_3. 3TBP(0)对氧化P50体系，在萃取剂大量过量下有下的平衡Cu_((a))~(2+) + partial deriv H_2R_2_((0)) <-> Cu(HR_2)_2 + 2H~+。用Scatchard-hildebrand模型预测了C_6H_(24)-TBP二元体系的担力学性质，以近似地用于H_2O - 16H_4 - TBP三之体系，减少了实验工作量。用气相色谱法求得了三之体系H_2O - (6H_(14) - P_(50))的热力学平衡数据，由于改进了进样系统，使实验误差<2%。对二体系的水相，均采用Pitzer理论求算γ_(Er(WO_3)_3)，和γ_(Cn~(2+))。对有机相，用热力学关系求出了水，正已烷，萃取剂，的活度系数。实验结果用Scatchard-Hildebrand模型进行关联。使计算机上进行回归处理，求得萃取反应的热力学平衡常数Ka和萃合物的活度系数。计算中，将有效平衡常数进一步分解，以提出显函数项，并在图解数分中改进了计算方法，使得每条萃取等温成都解得到合理的积分值。Schatchard-Hildebrand模型能在较宽的有机相浓度区域应用。所得到的端值常数，可定性地分析各组分的相互作用。

First charge collection and position-precision data on the medium-resistivity silicon strip detectors before and after neutron irradiation up to 2x10(14) n/cm(2)

Test strip detectors of 125 mu m, 500 mu m, and 1 mm pitches with about 1 cm(2) areas have been made on medium-resistivity silicon wafers (1.3 and 2.7 k Ohm cm). Detectors of 500 mu m pitch have been tested for charge collection and position precision before and after neutron irradiation (up to 2 x 10(14) n/cm(2)) using 820 and 1030 nm laser lights with different beam-spot sizes. It has been found that for a bias of 250 V a strip detector made of 1.3 k Ohm cm (300 mu m thick) can be fully depleted before and after an irradiation of 2 x 10(14) n/cm(2). For a 500 mu m pitch strip detector made of 2.7 k Ohm cm tested with an 1030 nm laser light with 200 mu m spot size, the position reconstruction error is about 14 mu m before irradiation, and 17 mu m after about 1.7 x 10(13) n/cm(2) irradiation. We demonstrated in this work that medium resistivity silicon strip detectors can work just as well as the traditional high-resistivity ones, but with higher radiation tolerance. We also tested charge sharing and position reconstruction using a 1030 nm wavelength (300 mu m absorption length in Si at RT) laser, which provides a simulation of MIP particles in high-physics experiments in terms of charge collection and position reconstruction, (C) 1999 Elsevier Science B.V. All rights reserved.

不同土壤磷流失过程模拟研究

本研究通过室内培养、淋溶模拟和径流模拟试验，分别对酸性土壤（红壤）和不同质地碱性土壤（潮褐土和黑钙土）磷流失过程进行模拟研究。结果表明，不同土壤相同水分条件下，土壤磷流失潜能不同：潮褐土磷流失潜能最强，黑钙土次之，红壤最低。不同水分条件下，相同土壤磷流失潜能也不同：淹水条件土壤磷流失潜能最高，其次为先干后湿条件和先湿后干条件，好气条件和淋溶最低。各种条件下土壤磷流失潜能均随施磷量的增加而增大。施肥初期或土壤环境变化初期，土壤磷通过地表径流和优先流流失的风险较高；通过基质流流失的磷在土壤中逐渐向下迁移，故磷流失风险发生在施肥后期。 分段模型（Split Line）方法适合于预测土壤磷通过径流向地表水或通过优先流向地下水体的流失，但不适合预测土壤磷通过基质流的流失。应针对土壤不同水分条件分别使用分段模型方法。若不考虑土壤不同水分条件，则用淹水条件下的临界值较为安全。在预测通过基质流淋失的磷时，使用深层土壤CaCl2-P磷含量较使用表层土壤磷含量更为合理。对于红壤，由于在各种培养条件下土壤Bray-P的变化趋势与CaCl2-P较为一致，且土壤Bray-P的分辨度较高，用土壤Bray-P表征磷流失潜能优于Olsen-P。 综合各种水分条件，红壤土壤磷流失安全值为Bray-P含量低于130 mg kg-1，黑钙土为Olsen-P含量低于138.2mg kg-1，潮褐土为Olsen-P含量低于88.9mg kg-1。