Design of the readout electronics for the DAMPE Silicon Tracker detector

The Silicon Tracker (STK) is one of the detectors of the DAMPE satellite used to measure the incidence direction of high energy cosmic rays. It consists of 6 X-Y double layers of silicon micro-strip detectors with 73728 readout channels. It is a great challenge to read out the channels and process the huge volume of data in the harsh environment of space. 1152 Application Specific Integrated Circuits (ASIC) and 384 ADCs are used to read out the detector channels. 192 Tracker Front-end Hybrid (TFH) modules and 8 identical Tracker Readout Board (TRB) modules are designed to control and digitalize the front signals. In this paper, the design of the readout electronics for the STK and its performance are presented in detail.     

Monolithic Uncooled 8 × 8 Bolometer Arrays Based on Poly-SiGe Thermistor

This paper presents a monolithic uncooled 8 × 8 bolometer array with polycrystalline silicon-germanium (poly-SiGe) thermistors as active elements. The poly-SiGe films are deposited by ultrahigh vacuum vapor deposition (UHV/CVD) system and the dependence of the temperature coefficient of resistance (TCR) on annealing temperature has been investigated. To decrease the thermal conductance of the bolometer, the poly-SiGe thermistor was formed on a four leg suspended microbridge. The improved porous silicon micromachining techniques described here enable the integration of the bolometer array with the MOS readout circuitry. The measurements and calculations show that the mean responsivity is 1.07 × 10⁴ V/W with an uncorrected uniformity of 10.5% and a thermal response time of 10.5 ms, and the detectivity of 3.75 × 10⁸ cm Hz^1/2/W is achieved at a chopping frequency of 30 Hz and a bias voltage of 5 V.     

DAMPE-PSD探测单元模块大动态范围读出方案的实验验证

暗物质粒子探测卫星（Dark Matter Particle Explorer,DAMPE）的塑闪阵列探测器（Plastic Scintillator Detector,PSD）需要实现高能e/γ粒子的鉴别功能以及对Z=1~20的宇宙线重离子的电荷测量功能。它使用光电倍增管作为读出器件,并从打拿极5和打拿极8同时引出信号来增大读出动态范围。基于该设计方案的探测单元模块在兰州重离子加速器冷却储存环（HIRFL-CSR）上的外靶终端（ETF）进行了束流测试实验。实验得到了PSD单元条在中能轻核区（Z≤8）的能量响应,并证明了单元条的衰减长度与入射粒子种类无关。通过将实验结果外推至高能重核区,同时结合衰减长度、入射角度和能量涨落等因素,可以估算出PSD探测单元模块输出信号幅度的动态范围。结果显示,该范围在PSD前端电子学模块的线性工作区间内,从而验证了PSD大动态范围读出方案设计的合理性。The Plastic Scintillator Detector (PSD) of DArk Matter Particle Explorer (DAMPE) aims for high energy e/γ identification and charge measurement for cosmic-ray ions from Z=1~20. It adopts photomultiplier tube as the readout device and extracts signals from both dynode5 and dynode8 to enlarge the readout dynamic range. A beam test on a PSD detector unit based this design has been carried out at the External Target Facility (ETF) terminal of the Cooling Storage Ring of Heavy Ion Research Facility in Lanzhou (HIRFL-CSR). The detector response to light nuclei (Z≤8) at the medium energy scale was extracted and the attenuation length was proved to be irrelevant with the impinging nuclei species. By extrapolating the result to heavy nuclei at the high energy scale and taking into account light attenuation, energy fluctuation and imping angle, the dynamic range of the output signal of PSD detector unit was estimated. The range is well within the linear range of the front-end electronics of PSD, thus verifies the large dynamic range readout design of PSD.     

Current-voltage characteristics of structures with a porous silicon layer at adsorption of carbon monoxide

The current-voltage characteristics of structures with a layer of porous silicon of 73% porosity were measured at adsorption of gas (carbon monoxide) at room temperature. Estimations are performed of the height of potential heterobarrier at the interface between porous silicon and p ⁺-type single-crystal silicon, of the perfectness factor and the resistance of a layer of porous silicon in air, in air with 0.4% CO, and in air with 2% CO. Physical causes explaining the experimental data are discussed.     

Silicon nitride/silicon oxide interlayers for solar cell passivating contacts based on PECVD amorphous silicon

This Letter demonstrates improved passivating contacts for silicon solar cells consisting of doped silicon films together with tunnelling dielectric layers. An improvement is demonstrated by replacing the commonly used silicon oxide interfacial layer with a silicon nitride/silicon oxide double interfacial layer. The paper describes the optimization of such contacts, including doping of a PECVD intrinsic a‐Si:H film by means of a thermal POCl₃ diffusion process and an exploration of the effect of the refractive index of the SiN_x. The n⁺ silicon passivating contact with SiN_x /SiO_x double layer achieves a better result than a single SiN_x or SiO_x layer, giving a recombination current parameter of ～7 fA/cm² and a contact resistivity of ～0.005 Ω cm², respectively. These self‐passivating electron‐selective contacts open the way to high efficiency silicon solar cells. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

IR study on the effect of chloride ion on porous silicon

Infrared (IR) studies have been carried out on porous silicon samples to infer on the changes in the surface bonding in the porous silicon (PS) layer due to chloride (Cl⁻) and subsequent fluoride (F⁻) ion exposures with respect to time. It is observed that silicon hydride linkages decreases and silicon oxide linkages increases with time of exposure to HCl, suggesting a possible oxidation of the porous layer. IR study revealed the formation of SiO (silanones) bonds. A possible mechanism for the formation of silanones from SiOH species has been proposed to explain the observation. We also observed a saturation of silicon oxide groups with complete disappearance of silicon hydride peaks indicating the complete conversion of silicon hydride to oxides. Furthermore on exposure to F⁻, the IR spectrum showed a rapid destruction of silicon oxygen linkages.     

Explanations of the DAMPE high energy electron/positron spectrum in the dark matter annihilation and pulsar scenarios

Many studies have shown that either the nearby astrophysical source or dark matter(DM)annihilation/decay can be used to explain the excess of high energy cosmic ray(CR)e~±,which is detected by many experiments,such as PAMELA and AMS-02.Recently,the dark matter particle explorer(DAMPE)collaboration has reported its first result of the total CR e~±spectrum from 25 Ge V to 4.6 Te V with high precision.In this work,we study the DM annihilation and pulsar interpretations of this result.We show that the leptonic DM annihilation channels toτ~+τ~-,4μ,4τ,and mixed charged lepton final states can well explain the DAMPE e~±spectrum.We also find that the mixed charged leptons channel would lead to a sharp drop structure at～Te V.However,the ordinary DM explanations have been almost excluded by the constraints from the observations of gamma-ray and CMB,unless some exotic DM models are introduced.In the pulsar scenario,we analyze 21 nearby known pulsars and assume that one of them dominantly contributes to the high energy CR e~±spectrum.Involving the constraint from the Fermi-LAT observation of the e~±anisotropy,we find that two pulsars could explain the DAMPE e~±spectrum.Our results show that it is difficult to discriminate between the DM annihilation and single pulsar explanations of high energy e~±with the current DAMPE result.     

A prototype silicon detector system for space cosmic-ray charge measurement

A readout electronics system used for space cosmic-ray charge measurement for multi-channel silicon detectors is introduced in this paper, including performance measurements. A 64-channel charge sensitive ASIC （VA140） from the IDEAS company is used. With its features of low power consumption, low noise, large dynamic range, and high integration, it can be used in future particle detecting experiments based on silicon detectors.     

a-Si(n)/c-Si(p)异质结太阳电池薄膜硅背场的模拟优化

采用AFORS-HET数值模拟软件,对不同带隙的薄膜硅材料在a-Si(n)/c-Si(p)异质结太阳电池上的背场效果进行了模拟,分析了影响背场效果的原因,得到了薄膜硅背场在a-Si(n)/c-Si(p)异质结太阳电池上的适用条件为薄膜硅材料是带隙16 eV,硼掺杂浓度在10¹⁸cm^-3以上的微晶硅材料,其最佳厚度在5nm左右. 这种背场从工艺上易于实现,并且,与常用的Al扩散背场相比,在相同的掺杂浓度下,电池效率可以大大提高. 关键词： 薄膜硅 背场 硅异质结太阳电池     

A prototype silicon detector system for space cosmic-ray charge measurement

A readout electronics system used for space cosmic-ray charge measurement for multi-channel silicon detectors is introduced in this paper, including performance measurements. A 64-channel charge sensitive ASIC (VA140) from the IDEAS company is used. With its features of low power consumption, low noise, large dynamic range, and high integration, it can be used in future particle detecting experiments based on silicon detectors.     

硅片及其太阳电池的光衰规律研究

采用氙灯模拟太阳光源,将光强调至1000 W/m2,研究常规太阳能级单晶硅片、多晶硅片和物理提纯硅片的原片、去损减薄片、热氧化钝化片、双面镀氮化硅(SiN x:H)膜钝化片、碘酒钝化片以及太阳电池的光衰规律.利用WT-2000少子寿命测试仪以及太阳电池I-V特性测试仪分别对硅片的少子寿命和太阳电池的I-V特性参数随光照时间的变化进行了测试.结果表明:所有硅片以及太阳电池在光照的最初60 min内衰减很快随后衰减变慢,180 min之后光衰速率变得很小,几乎趋于零.     

控制氧化层对双势垒纳米硅浮栅存储结构性能的影响

在等离子体增强化学气相沉积(PECVD)系统中,利用逐层淀积非晶硅(a-Si)和等离子体氧化相结合的方法制备二氧化硅(SiO₂)介质层.电容电压(C-V)和电导电压(G-V)测量结果表明：利用该方法在低温(250 ℃)条件下制备的SiO₂介质层均匀致密,其固定氧化物电荷和界面态密度分别为9×10¹¹cm^-2和2×10¹¹cm^-2·eV^-1,击穿场强达4.6 MV/cm,与热氧化形成的SiO₂介质层的性质相当.将该SiO₂介质层作为控制氧化层应用在双势垒纳米硅(nc-Si)浮栅存储结构中,通过调节控制氧化层的厚度,有效阻止栅电极与nc-Si之间的电荷交换,延长存储时间,使存储性能得到明显改善. 关键词： 等离子体氧化 二氧化硅 纳米硅 控制氧化层     

Dark Matter Particle Explorer observations of high-energy cosmic ray electrons plus positrons and their physical implications

The DArk Matter Particle Explorer(DAMPE) is a satellite-borne, high-energy particle and γ-ray detector, which is dedicated to indirectly detecting particle dark matter and studying high-energy astrophysics. The first results about precise measurement of the cosmic ray electron plus positron spectrum between 25 Ge V and 4.6 Te V were published recently. The DAMPE spectrum reveals an interesting spectral softening arount 0.9 Te V and a tentative peak around 1.4 Te V. These results have inspired extensive discussion. The detector of DAMPE, the data analysis, and the first results are introduced. In particular, the physical interpretations of the DAMPE data are reviewed.     

Interpretation of the DAMPE 1.4 TeV peak according to the decaying dark matter model

Highly accurate measurements of cosmic ray electron flux by the dark matter particle explorer(DAMPE) ranging between 25 Ge V and 4.6 Te V have recently been published. A sharp peak structure was found at ～ 1.4 Te V. This unexpected peak structure can be reproduced by the annihilation/decay of a nearby dark matter(DM) halo. In this study, we adopt the decaying-DM model to interpret the ～ 1.4 Te V peak. We found that the decay products of the local DM subhalo could contribute to the DMAPE peak with mDM= 3 Te V and τ～ 10~(28) s. We also obtain constraints on DM lifetime and the distance of the local DM subhalo by comparison with DAMPE data.     

Fiber Optic Excitation of Silicon Microspheres in Amorphous and Crystalline Fluids

ABSTRACT

This study investigates the optical resonance spectra of free-standing monolithic single crystal silicon microspheres immersed in various amorphous fluids, such as air, water, ethylene glycol, and 4-Cyano-4’-pentylbiphenyl nematic liquid crystal. For the various amorphous fluids, morphology-dependent resonances with quality factors on the order of 10⁵ are observed at 1428 nm. The mode spacing is always on the order of 0.23 nm. The immersion in various amorphous fluids affects the spectral response of the silicon microsphere and heralds this technique for use in novel optofluidics applications. Even though the nematic liquid crystal is a highly birefringent, scattering, and high-index optical medium, morphology-dependent resonances with quality factors on the order of 10⁵ are observed at 1300 nm in the elastic scattering spectra of the silicon microsphere, realizing a liquid-crystal-on-silicon geometry. The relative refractive index and the size parameter of the silicon microsphere are the parameters that affect the resonance structure. The more 4-Cyano-4’-pentylbiphenyl interacting with the silicon microsphere, the lower the quality factor of the resonances is. The more 4-Cyano-4’-pentylbiphenyl is interacting with the silicon microsphere, the lower the mode spacing Δλ of the resonances is. The silicon microspheres wetted with nematic liquid crystal can be used for optically addressed liquid-crystal-on-silicon displays, light valve applications, or reconfigurable optical networks.     

488 nm连续激光晶化本征非晶硅薄膜的喇曼光谱研究

利用等离子增强化学气相沉积系统制备了本征非晶硅薄膜,并选用488 nm波长的连续激光进行晶化.采用喇曼测试技术对本征非晶硅薄膜在不同激光功率密度和扫描时间下的晶化状态进行了表征,并用514 nm波长与488 nm波长对样品的晶化效果进行了比较.测试结果显示:激光照射时间60 s, 激光功率密度在1.57×10⁵ W/cm²时,能实现非晶硅向多晶硅的转变,在功率密度达到2.7 56×10⁵ W/cm²时,有非晶开始向单晶转变,随着激光功率密度的继续增加,晶化结果仍为单晶;在功率密度为2.362×10⁵ W/cm²下,60 s照射时间晶化效果较好;在功率密度为2.756×10⁵ W/cm²和照射时间为60 s的条件下,用488 nm波长比514 nm波长的激光晶化本征非晶硅薄膜效果较好,并均为单晶态.     

Performance of a silicon monochromator under high heat load

The performance of a cryogenically cooled double‐crystal silicon monochromator was studied under high‐heat‐load conditions with total absorbed powers and power densities ranging from 8 to 780 W and from 8 to 240 W mm^?2, respectively. When the temperature of the first crystal is maintained close to the temperature of zero thermal expansion of silicon, the monochromator shows nearly ideal performance with a thermal slope error of 0.6 µrad. By tuning the size of the first slit, the regime of the ideal performance can be maintained over a wide range of heat loads, i.e. from power densities of 110 W mm^?2 (at total absorbed power of 510 W) to 240 W mm^?2 (at total absorbed power of 240 W).     

磁控溅射淀积掺Er富Si氧化硅膜中Er3+ 1.54μm光致发光

用磁控溅射淀积不同富Si程度的掺Er富Si氧化硅薄膜.室温下测量其光致发光谱,观察到各谱中都含有1.54和1.38μm两个发光峰,其中1.54和1.38μm的光致发光峰分别来自Er³⁺和氧化硅中某种缺陷.系统研究了Er³⁺1.54μm光致发光峰强度对富Si程度及退火温度的依赖关系.还发现1.54μm发光峰强度与1.38μm发光峰强度相互关联,对此进行了讨论 关键词： Er 富Si氧化硅 光致发光 纳米硅     

Sunlight loss for femtosecond microstructured silicon with two impurity bands

Black silicon,produced by irradiating the surface of a silicon wafer with femtosecond laser pulses in the presence of a sulfur-bearing gas,is widely believed to be a potential material for efficient multi-intermediate-band silicon solar cells.Taking chalcogen as an example,we analyse the loss of sunlight for silicon with two impurity bands and we find that loss of the sunlight can be minimized to 0.332 when Te 0 (0.307 eV) and Te + (0.411 eV) are doped into microstructured silicon.Finally,problems needed to be resolved in analysing the relationship between conversion efficiency of the ideal four-band silicon solar cell and the position of the introduced two intermediated bands in silicon according to detailed balance theory are pointed out with great emphasis.