Plasma diagnosis of tetrahedral amorphous carbon films by filtered cathodic vacuum arc deposition

Filtered cathodic vacuum arc(FCVA)deposition is regarded as an important technique for the synthesis of tetrahedral amorphous carbon(ta-C)films due to its high ionization rate,high deposition rate and effective filtration of macroparticles.Probing the plasma characteristics of arc discharge contributes to understanding the deposition mechanism of ta-C films on a microscopic level.This work focuses on the plasma diagnosis of an FCVA discharge using a Langmuir dualprobe system with a discrete Fourier transform smoothing method.During the ta-C film deposition,the arc current of graphite cathodes and deposition pressure vary from 30 to 90 A and from 0.3 to 0.9 Pa,respectively.The plasma density increases with arc current but decreases with pressure.The carbon plasma density generated by the arc discharge is around the order of10^(10)cm^(-3).The electron temperature varies in the range of 2-3.5 eV.As the number of cathodic arc sources and the current of the focused magnetic coil increase,the plasma density increases.The ratio of the intensity of the D-Raman peak and G-Raman peak(I_(D)/I_(G))of the ta-C films increases with increasing plasma density,resulting in a decrease in film hardness.It is indicated that the mechanical properties of ta-C films depend not only on the ion energy but also on the carbon plasma density.

Optical and electrical properties of BaSnO_(3) and In_2O_(3) mixed transparent conductive films deposited by filtered cathodic vacuum arc technique at room temperature

For the crystalline temperature of BaSnO_(3)(BTO)was above 650℃,the transparent conductive BTO-based films were always deposited above this temperature on epitaxy substrates by pulsed laser deposition or molecular beam epitaxy till now which limited there application in low temperature device process.In the article,the microstructure,optical and electrical of BTO and In_(2)O_(3) mixed transparent conductive BaInSnO_(x)(BITO)film deposited by filtered cathodic vacuum arc technique(FCVA)on glass substrate at room temperature were firstly reported.The BITO film with thickness of 300 nm had mainly In_(2)O_(3) polycrystalline phase,and minor polycrystalline BTO phase with(001),(011),(111),(002),(222)crystal faces which were first deposited at room temperature on amorphous glass.The transmittance was 70%–80%in the visible light region with linear refractive index of 1.94 and extinction coefficient of 0.004 at 550-nm wavelength.The basic optical properties included the real and imaginary parts,high frequency dielectric constants,the absorption coefficient,the Urbach energy,the indirect and direct band gaps,the oscillator and dispersion energies,the static refractive index and dielectric constant,the average oscillator wavelength,oscillator length strength,the linear and the third-order nonlinear optical susceptibilities,and the nonlinear refractive index were all calculated.The film was the n-type conductor with sheet resistance of 704.7Ω/□,resistivity of 0.02Ω⋅cm,mobility of 18.9 cm2/V⋅s,and carrier electron concentration of 1.6×10^(19) cm^(−3) at room temperature.The results suggested that the BITO film deposited by FCVA had potential application in transparent conductive films-based low temperature device process.

STUDY ON DIAMOND LIKE CARBON THIN FILM BY FILTERED VACUUM ARC DEPOSITION

Diamond like carbon thin film is successfully deposited on silicon, titanium and stainless steel substrate at low temperature in a filtered vacuum arc deposition system. Arc discharges are established on a graphite cathode in the system with a toroidal macroparticle filter. A cathode activating magnetic field and a filtered magnetic field to collimate the plasma beam are applied. Ion current convected by the plasma beam is measured with a negatively biased probe. It is shown that the magnetic field of the coils located on the plasma duct has a strong influence on cathode spot behavior. Orthogonally the designed experiments are carried out to optimize the deposition parameters of arc stability. Finally, the diamond like carbon thin films are studied by scanning electron microscope (SEM) and Raman spectrum.

Experimental Research of DLC Film Deposited by Filtered Vacuum Arc Evaporation

Diamond like carbon (DLC) films was grown successfully on silicon, titanium and high speed steel (HSS) substrate at low temperature in a filtered vacuum arc deposition system. Arc discharges were established on a graphite cathode in this home built system with a toridal macroparticles filter. Ion current convected by the plasma beam was measured with a negatively biased probe. It was shown that the magnetic field of the coils located on the plasma duct has a strong influence on ion current. Scanning electron microscope (SEM), atomic force microscope (AFM) and Raman spectrum are used to study the DLC films. Tribological behaviors of the deposited film are also studied.

THE EFFECTS OF NEGATIVE BIAS AND FLUX RATIO ON THE PROPERTIES OF TiN THIN FILMS FORMED BY FILTERED CATHODIC ARC PLASMA TECHNIQUE

The filtered cathodic vacuum-arc (FCVA) technique is a supplementary and alterna tive technique with respect to convendtional physical and chemical vapour deposi tion which can remove macro-particles effectively and make the deposition proces s at ambient temperature. In this work, high quality TiN thin films were deposi ted on silicon substrates at low temperature using the improved filtered cathodi c arc plasma (FCAP) technique. AFM, XRD, TEM were employed to characterize the T iN thin films. The effects of the negative substrate bias on the grain size, pre ferred crystalline orientation, surface roughness of TiN thin films were discuss ed.

Fabrication of Tungsten Carbide Films by Filtered Pulse Arc Deposition with Cemented Tungsten Carbide Cathodes

Tungsten carbide films (W-C films) were fabricated on silicon substrates by using the filtered pulse arc deposition (FPAD) method. Two types of cemented tungsten carbide (WC) were used as cathode, one containing Co and the other Ti, which were used as binders for forming the cathode shape. The films were fabricated by varying the pulse arc current and substrate bias voltage. The discharge, deposition and film properties were investigated under these deposition conditions. The cathode wear amount when using WC-Co (WC cathode containing Co) was found to be smaller than that measured when WC-Ti (WC cathode containing Ti) was used. The W-C film thickness was approximately 30 - 40 nm under all conditions, except when the pulse arc current was 50 A and the film thickness, was approximately 10 nm. Compared to the WC-Ti, the consumption of cathode material is suppressed in the WC-Co, indicating that the efficiency for film preparation of the latter is good. From the X-ray diffraction analysis, the crystalline phase of W-C films fabricated using WC-Co and WC-Ti were observed as W2C and WC1-x, respectively, indicating that different crystalline phases could be fabricated using different cathodes. From the X-ray photoelectron spectroscopy analysis, the oxidation layer formed by air exposure was observed to exclusively exist on the W-C film surface. Moreover, almost all oxygen in the oxidation layer bonded with tungsten.

The Properties of the Rectangular Arc Ion Plating with Magnetic Filtering Shutter

A major obstacle to the broad application of cathodic arc plasma deposition is the presence of macroparticles. In this paper, the properties of the large rectangular arc ion plating with a magnetic filtering shutter system to filter macroparticles are studied. It is proposed that the macroparticles in the plasma beam are effectively removed with the magnetic filtering shutter system, and the quality of the deposited films is improved.

Volumetric modulation arc radiotherapy with flattening filter-free beams compared with conventional beams for nasopharyngeal carcinoma:a feasibility study

There is increasing interest in the clinical use of flattening filter-free(FFF) beams.In this study,we aimed to investigate the dosimetric characteristics of volumetric modulated arc radiotherapy(VMAT) with FFF beams for nasopharyngeal carcinoma(NPC).Ten NPC patients were randomly selected to undergo a RapidArc plan with either FFF beams(RA-FFF) or conventional beams(RA-C).The doses to the planning target volumes(PTVs),organs at risk(OARs),and normal tissues were compared.The technical delivery parameters for RapidArc plans were also assessed to compare the characteristics of FFF and conventional beams.Both techniques delivered adequate doses to PTVs.For PTVs,RA-C delivered lower maximum and mean doses and improved conformity and homogeneity compared with RA-FFF.Both techniques provided similar maximum doses to the optic nerves and lenses.For the brain stem,spinal cord,larynx,parotid glands,oral cavity,and skin,RA-FFF showed significant dose increases compared to RA-C.The dose to normal tissue was lower in RA-FFF.The monitor units(MUs) were(536 ± 46) MU for RA-FFF and(501± 25) MU for RA-C.The treatment duration did not significantly differbetween plans.Although both treatment plans could meet clinical needs,RA-C is dosimetrically superior to RA-FFF for NPC radiotherapy.

Mechanical Properties of Composite SiNx/DLC Films Prepared by Filtered Cathodic Arc of Graphite Incorporated with RF Sputtering of Silicon Nitride

Composite SiNx/DLC films were deposited on Si substrate by RF magnetron sputtering of silicon nitride (Si3N4) target simultaneously with filtered cathode arc (FCA) of graphite. The RF power was fixed at 100 W whereas the arc currents of FCA were 20, 40, 60 and 80 A. The effects of arc current on the structure, surface roughness, density and mechanical properties of SiNx/DLC films were investigated. The results show that the arc current in the studied range has effect on the structure, surface roughness, density and mechanical properties of composite SiNx/DLC films. The composite SiNx/DLC films show the sp3 content between 53.5% and 66.7%, density between 2.54 and2.98 g/cm3, stress between 1.7 and 2.2 GPa, and hardness between 35 and 51 GPa. Furthermore, it was found that the density, stress and hardness correlate linearly with the sp3 content for composite SiNx/DLC films.

Case Report: Anaplastic Astrocytoma Treated with Postoperative Radiotherapy Using Flattening Filter-Free Volumetric Arc Therapy (FFF-VMAT) during Pregnancy—Acceptable Fetal Dosimetry

Background: Postoperative irradiation for brain tumor in pregnant women is a matter of concern. Aim: We aimed to assess the safety of radiotherapy for brain tumors in pregnancy. We here report a successful treatment for anaplastic astrocytoma during pregnancy: surgery + postoperative irradiation. We wish to emphasize how we devised irradiation procedure to achieve both therapeutic effectiveness and safety to the fetus/infant. Case Presentation: A 34-year-old pregnant woman suffered with brain anaplastic astrocytoma. Tumor resection under craniotomy was performed with success. We decided to conduct postoperative radiotherapy at 25 weeks of gestation to reduce the risk of recurrence. We used a flattening filter-free volumetric arc therapy (FFF-VMAT) technique, which can achieve lower out-of-field dose than VMAT with a flattening filter or helical tomotherapy. We prescribed 60 Gy over 30 fractions. During actual beam delivery, surface and rectal dose to the patient (mother) were measured. The total fetal dose was estimated at 0.006 - 0.018 Gy, which is under the threshold set by the ICRP. A male healthy infant was born vaginally at the 37th week of pregnancy. The patient (mother) and the infant are healthy at the time of writing. Conclusion: FFF-VMAT is a good choice for brain tumors during pregnancy.

基于电源端电压的电动汽车电弧故障检测

当电动汽车主电路的电气接触点接触不良时,极易产生电弧故障,直接威胁车内人员的生命安全。论文提出了一种基于自定义差分阈值滤波-分段最大值标准化-统计数值规律的电弧故障检测方法。首先围绕真实电动汽车吉利帝豪EV450搭建了电动汽车电弧故障实验平台,开展了电动汽车在不同工作模式下的电弧故障实验。然后以电源端电压为对象,对信号进行小波分解,对小波分解得到的低频系数进行自定义差分阈值滤波和分段最大值标准化。最后统计标准化后数据相同值个数,并通过阈值法检测串联型电弧故障。论文对模型样本长度、差分阈值比例、最大值标准化分段数、预处理方法选择等进行了深入分析,并对参数进行了优化设置,进一步提升模型性能。结果表明,所建模型对电动汽车电弧故障检测准确率为98.35%,且实时性较好。通过对模型进行泛化性分析、算法时间复杂度分析及与其他电弧故障检测模型对比分析,证明论文所建模型对电动汽车电弧故障检测具有较好的适用性。

基于机器视觉滑轨截面圆弧尺寸的测量方法

为解决汽车座椅滑轨截面圆弧尺寸人工检测效率低、一致性差的问题,文章提出了一种基于卡尺边缘检测与Tukey算法相结合的测量方法,实现滑轨截面圆弧尺寸高效率、高精度的检测。首先对采集到的图像做双边滤波处理,去除图像中的噪声,再通过HALCON算法库中的Emphasize算子对图像做处理,突出图像边缘信息;然后通过卡尺边缘检测算法提取圆弧边缘点;最后结合加权Tukey的最小二乘法分离出异常点并完成圆的拟合。实验结果表明,该方法可实现滑轨截面圆弧尺寸的快速检测,测量系统稳定性好、可靠性高,测量误差均在0.08 mm之内,重复测量精度可达0.02 mm。

基于焊枪摆动和电弧旋转的对接焊缝偏差识别

针对坡口宽度不一的对接焊缝难以实现焊缝偏差识别及自动焊接的难题,提出焊枪摆动和旋转电弧复合的焊缝偏差识别方法。研究对接焊缝在不同焊枪偏差情况下的焊接电流信号,采集电流信号并进行时频分析以选择合适的滤波方法,进行软阈值小波为核心的组合滤波,对滤波去噪后的电流信号作短时能量处理和偏差算法计算。实现焊枪的到边检测与焊缝偏差识别,且偏差结果与设定的焊枪偏差值基本相同,验证整个焊缝偏差识别方法的准确性。

磁过滤电弧离子镀TiN与N离子注入性能研究

目的研究磁过滤电弧离子镀TiN与N离子注入对金属基体的保护效果。方法采用磁过滤电弧离子镀和离子注入在不锈钢表面分别制备了TiN薄膜与N注入改性层,以及二者的复合膜层。对薄膜的相结构、微观形貌进行了表征,对薄膜进行了极化曲线测试,同时在半球样品表面制备涂层并进行盐雾测试。结果所制备的TiN涂层为(111)晶面择优取向,离子注N预处理后沉积的TiN薄膜,仍保持(111)面的择优取向;电化学测试结果显示,TiN和N离子注入能够使不锈钢基体自腐蚀电位分别提高0.64、0.25 V,TiN薄膜具有最低的维钝电流密度4.9×10^(-6) A/cm^(2),N离子注入+TiN复合薄膜的维钝电流密度与N离子注入样品接近;盐雾试验结果表明,TiN以及N离子注入+TiN复合薄膜样品能够保证铜半球在12h的中性盐雾试验中无明显腐蚀痕迹。结论N离子注入预处理对MFAIPTiN涂层耐蚀性能的提升效果有限,单一的MFAIP TiN涂层便可应用于复杂形状的工程材料表面镀膜,可以增强其抗腐蚀能力,延长使用寿命。

非均整模式与均整模式下儿童肾母细胞瘤容积调强放疗的剂量学研究

目的:对比在均整(flattening filter,FF)模式与非均整(flattening filter free,FFF)模式下儿童肾母细胞瘤容积调强放疗(volumetric modulated arc therapy,VMAT)的剂量学差异。方法:回顾性选取2022年8月至2023年10月于某院接受放疗的10例肾母细胞瘤患儿,均设计FF模式和FFF模式下的VMAT计划,比较2种计划的计划靶区(planning target volume,PTV)剂量学参数、危及器官(organ at risk,OAR)受照剂量、机器跳数、γ通过率及治疗时间。结果:FFF计划的D_(2)、D_(98)及均匀性指数均优于FF计划,差异有统计学意义(P<0.05);而2种计划的D50和适形性指数比较,差异无统计学意义(P>0.05)。FFF计划在对侧肾脏D_(mean)、V_(5)、V_(10),肝脏D_(mean)、V_(5)、V_(10)以及脊髓D_(max)方面均优于FF计划,差异有统计学意义(P<0.05)。FF计划在γ通过率、机器跳数方面均优于FFF计划,而FFF计划的治疗时间明显短于FF计划,差异有统计学意义(P<0.05)。2种计划的γ通过率均>95%。结论:FF模式和FFF模式下的VMAT计划均能满足临床治疗要求,FFF模式较FF模式在PTV剂量分布、OAR受照剂量和治疗时间方面更有优势,对提升患儿治疗效果和配合度有积极影响。

基于Flatten-Filter Free模式治疗原发性肝癌的剂量学研究

目的:比较原发性肝癌的Flatten-Filter Free(FFF)模式和Flatten Filter(FF)模式的单弧、双弧以及七野固定野治疗的剂量学差异。方法:选取13例原发性肝癌患者,在增强CT图像上勾画靶区及危及器官和正常组织,并在同一套CT图片上设计单个全弧、双全弧和七野固定野的FFF模式和FF模式的调强计划,病人总的治疗剂量200 c Gy×30次。通过剂量体积直方图统计PTV相关的剂量学参数、适形度指数(CI)、均匀性指数(HI),肝脏的剂量体积学参数、机器跳数、治疗时间和计划时间等利用SPSS20.0进行配对非参数Wilcoxson符号秩检验的统计学处理。结果:3种放疗计划FF和FFF模式靶区的HI和CI均没有统计学差异(P>0.05),靶区的V95%、最大剂量、最小剂量和平均剂量有统计学差异(P<0.05),在单弧、双弧和七野固定野调强计划的FF和FFF模式中,靶区的V95%FFF比FF分别低34.3%、13%、1.2%,靶区最大剂量FFF模式比FF分别低1.54%、1.39%、2.2%,靶区的最小剂量分别降低17.9%、6.6%、9.23%,平均剂量分别降低9.23%、2.0%、2.3%。结论:FFF模式可以有效降低正常肝脏组织受量,减少病人治疗时间,可以在图像引导基础上进一步提高放疗的安全性。

Vision sensing of P-GMAW weld pool using narrow band filters with different center wavelengths

The selection of narrow band filter＇s center wavelength has an important influence on the quality of the weld pool image captured in passive vision mettmd for controlling arc welding process. In this paper, 29 narrow band filters with different center wavelengths ranging from ultraviolet to near infrared wavelength were used to capture images of weld pool during both the peak current period and the base current period of P-GMA W （ pulsed gas metal arc welding）. The experimental results showed that the filters with near infrared center wavelength could weaken the arc most during the peak current period, while during the base current period the entire weld pool could be seen with the filters with wavelength above 600 nm. The camera spectral response and the radio of arc to weld pool emission were considered to analyze the phenomenon of experimental results.

一种大功率等离子体火炬电源系统及控制策略

在大功率等离子体电弧系统中,采用PWM整流加BUCK斩波电路作为电源系统主电路,通过设计主电路参数与控制环,使电源在稳态运行时具有较强的抵抗负载扰动的能力。对系统进行的仿真模拟结果和实验结果均验证了所提方案的有效性。

呼吸触发前瞻门控在早期非小细胞肺癌立体定向放射治疗中剂量学优势

目的探讨呼吸触发前瞻门控在早期非小细胞肺癌(NSCLC)立体定向放射治疗(SBRT)中剂量学优势。方法选取21例经病理证实的早期NSCLC患者,分别行自由呼吸下3D-CT、4D-CT电影模式和呼气末前瞻性呼吸触发轴向-R模式扫描,同等条件下分别设计前瞻门控(Plan_(pro))、30%~70%时相回顾门控(Plan_(30-70))、运动包络法(Plan_(all))及传统基于人群边际的3D-CT(Plan_(3D))4组无均整器模式容积旋转调强SBRT计划。统计分析计划靶体积(PTV)、患侧肺和全肺的V_(5)、V_(20)、V_(14.4)、平均肺剂量(MLD)、全肺正常组织并发症概率(NTCP)、心脏D_(max)、食管D_(max)、食管NTCP、脊髓D_(max)和近端支气管树D_(max)等指标。结果Plan_(all)与Plan_(3D)相比,除脊髓D_(max)的所有剂量学参数均下降差异有统计学意义(P<0.05)。与Plan_(all)相比,Plan_(pro)的PTV、患侧肺V_(5)、V_(20)、V_(14.4)、MLD、全肺V_(5)、V_(20)、V_(14.4)、MLD、NTCP、心脏D_(max)和食管NTCP较Plan_(30-70)分别进一步减少了8.42 cc、2.06%、1.02%、26.67 cc、0.58 Gy、2.35%、0.63%、32.89 cc、0.43 Gy、0.1%、1.72 Gy及0.09%,差异有统计学意义(P值分别为0.004、<0.010、0.006、0.010、0.006、0.004、<0.001、0.010、<0.001、0.005、<0.001、0.026)。结论早期NSCLC SBRT中,传统基于人群边际的3D-CT计划高估PTV并增加危及器官受量;采用呼吸运动管理技术,尤其是前瞻门控更好保护胸部正常组织器官,减少患者放疗不良反应。

计及等效负载变化的消弧逆变器性能分析与设计

分析了消弧逆变器等效负载的性质,结果表明:等效负载是有源负载,等效源具有较大的幅值和较宽的变化范围;随过渡电阻和故障距离的变化,等效负载阻抗可呈现阻性、阻感性和阻容性。这一结果表明逆变器需要在负载性质改变和等效电源扰动的情况下,仍能稳定跟踪包含多频次的给定电流。对抗扰性和跟踪性要求的提高,增加了设计难度。鉴于此,提出了消弧逆变器输出滤波器和控制器的设计方法。输出滤波器采用滤波电容分流法进行设计,保证了逆变器能输出包含多频次的电流。采用电容串联电阻来抑制阻感负载情况下带来的谐振失稳问题,并给出了串联电阻的计算方法。控制器采用了定带宽设计法,带宽选定在幅频特性重合段。控制器参数设计准则为:保证阻容负载情况下传函幅频特性低频段具有较高增益。采用PSCAD/EMTDC仿真验证了结论的正确性和所提设计方法的可行性。