变色薄膜的紫外线辐照响应研究

制备了含多芳氨基甲烷类化合物的高分子变色薄膜,经紫外线辐照后,这种薄膜随吸收剂量的不同由无色透明逐渐变为绿色,在可见光区主要吸收峰位于626 nm附近,光密度响应与辐照时间近似成线性关系。研究表明：该辐射变色薄膜变色响应随紫外线能量密度增加而增加;分次辐照能略微提高光密度响应;辐射变色薄膜响应受温度和湿度影响较大,在20～50 ℃温度范围、40%～60%相对湿度范围,响应基本稳定;卤代物添加剂可以大大提高辐射变色薄膜的响应灵敏度;受后辐照效应影响,辐照结束最初2 h内响应迅速增加,2 h后响应才基本稳定。     

辐射变色薄膜的质子辐照响应

用J-2.5质子静电加速器提供的质子束,对研制的一种高灵敏度新型辐射变色膜进行质子辐射响应研究。该变色膜以聚乙烯醇缩聚物为基质,以类丁二炔化合物为有机染色材料,质子能量为2.0 MeV,辐照注量为1.0×1010～1.0×1012 cm-2。用光谱响应测试薄膜的辐射效应显示：变色薄膜颜色由粉红渐变为蓝色, 并随着辐照剂量的增加而逐渐加深;用图像分析仪分析辐照后靶材的光密度发现,图像的光密度随聚焦斑距离的增大而减小;用分光光度计测试其吸收光谱发现,主吸收峰值出现在660 nm附近,且吸收峰处的响应吸光度与质子注量具有较好的线性关系;对新型变色薄膜辐照后持续效应的研究表明,变色膜辐照后续效应微弱,辐照后可以立即测量,且对测量环境变化不敏感。     

辐射变色薄膜的质子辐照响应

 用J-2.5质子静电加速器提供的质子束,对研制的一种高灵敏度新型辐射变色膜进行质子辐射响应研究。该变色膜以聚乙烯醇缩聚物为基质,以类丁二炔化合物为有机染色材料,质子能量为2.0 MeV,辐照注量为1.0×10¹⁰～1.0×10¹² cm^-2。用光谱响应测试薄膜的辐射效应显示：变色薄膜颜色由粉红渐变为蓝色, 并随着辐照剂量的增加而逐渐加深;用图像分析仪分析辐照后靶材的光密度发现,图像的光密度随聚焦斑距离的增大而减小;用分光光度计测试其吸收光谱发现,主吸收峰值出现在660 nm附近,且吸收峰处的响应吸光度与质子注量具有较好的线性关系;对新型变色薄膜辐照后持续效应的研究表明,变色膜辐照后续效应微弱,辐照后可以立即测量,且对测量环境变化不敏感。     

聚氨酯光变色薄膜研究

以聚氨酯为中心介质组成的光学变色薄膜,当有自然光进入光学变色薄膜时,随着入射光和视角的变化,在薄膜上可以看到明显的光变色效果。这种薄膜可以单独成为一种防伪材料或与油墨组合成为一种新颖防伪油墨。根据多层复合膜光干涉原理设计和计算了光变色薄膜,所确定的薄膜膜系结构为PET(聚酯薄膜)/Cr/介质/Al。介质是有机高聚物聚氨酯。通过调节多元醇、异氰酸酯和氨基甲酸酯以及催化剂的含量和反应方程式,使聚氨酯材料具有较高的折射率,以充分体现光变色的效果。介绍了光变色薄膜的制作方法,研究了薄膜的相关特性。     

WO3薄膜的电致变色特性研究

介绍了ＷＯ３电致变色薄膜的变色机理和制备工艺，对ＷＯ３薄膜的电阻率，结构，化学组玢，电化学特性和变性性能等特性进行了工艺，提出了ＷＯ３薄膜的一种新的锂化方法，这种方法对进一步研制全固态电致变色薄膜器件是十分关键的。     

新型辐射变色凝胶的紫外辐照研究

将类丁二炔化合物自组装成纳米囊泡后,均匀分散于凝胶载体中,研制出一种新型的辐射变色凝胶剂量计。用电镜观测了囊泡形貌,采用CL-1000型紫外交联仪对凝胶进行辐照,测试并研究了凝胶对紫外辐照的变色响应、辐射后效应、扩散效应等剂量学性能。结果表明：该辐射变色凝胶在5~150 mJ/cm2能量密度范围内对紫外线辐照具有良好的响应线性,同时克服了扩散效应、辐射后效应、成型能力差等现有凝胶剂量计的不足。该辐射变色凝胶剂量计适于光学扫描方式测量剂量分布。     

新型辐射变色凝胶的紫外辐照研究

将类丁二炔化合物自组装成纳米囊泡后,均匀分散于凝胶载体中,研制出一种新型的辐射变色凝胶剂量计。用电镜观测了囊泡形貌,采用CL-1000型紫外交联仪对凝胶进行辐照,测试并研究了凝胶对紫外辐照的变色响应、辐射后效应、扩散效应等剂量学性能。结果表明:该辐射变色凝胶在5~150mJ/cm2能量密度范围内对紫外线辐照具有良好的响应线性,同时克服了扩散效应、辐射后效应、成型能力差等现有凝胶剂量计的不足。该辐射变色凝胶剂量计适于光学扫描方式测量剂量分布。     

辐射变色膜片对质子剂量响应的实验标定

 利用串列静电加速器产生的5~9 MeV的质子束对HD-810型辐射变色膜片（RCF）进行了标定。用分光光度计和普通的商用平板扫描仪对辐照后的RCF透过率进行了测量,得到了光学密度变化随RCF灵敏层吸收剂量的变化曲线。标定实验结果表明:在一定的吸收剂量范围内,RCF的光学密度变化与RCF灵敏层中吸收剂量成线性关系,并且与质子能量无关。测量光学密度所用光源的波长对线性范围的大小有较大影响,绿光(532 nm)比红光(670 nm)有更大的剂量探测范围。     

电致变色薄膜锂化技术的研究

提出了一种新的电致变色薄膜的锂化方法，通过电子枪蒸镀锂单质，提高了锂的离化率，从而提高了锂化效果，采用此技术研制的全固态电致变色薄膜器件获得了较好的变色特性，透射式和反射式全固态电致变色薄膜器件的变色性能分别为５０％￣５％和７０％￣２０％。     

高感度辐射变色薄膜电子剂量计

 以聚乙烯醇缩聚物为基质,以类丁二炔化合物为有机染色材料,研制了一种高灵敏度新型辐射变色膜。采用JJ-2型范格拉夫静电加速器对变色薄膜进行剂量范围为15～90 Gy的电子束辐照,结果显示:变色薄膜颜色由粉红渐变为蓝色,并随着辐照剂量的增加而逐渐加深;分光光度计测试其吸收光谱,发现主吸收峰值出现在675 nm附近,且吸收峰处的响应吸光度与电子注量具有较好的线性关系;对变色层厚度为20～80 μm的变色膜,吸收峰处的响应吸光度与其变色层厚度也成线性关系;添加不同比例的协同剂,能提高变色薄膜的响应灵敏度;变色膜辐照后续效应微弱,辐照后可以立即测量,且对测量环境变化不敏感。     

Spectral analysis of the EBT3 radiochromic film irradiated with 6 MV X-ray radiation

The EBT3 radiochromic film was introduced as the next generation of EBT and EBT2 films, maintaining the composition of the active layer. X-ray radiation produces a change in its visible light absorption spectrum and optical properties being granted make the films suitable for dosimetric applications. The goal of this study is to present results of absorption spectra measurements for the EBT3 radiochromic film exposed to 6 MV X-ray radiation in the dose range from 0 to 50 Gy. Results showed that the spectrum of the EBT3 radiochromic has an intense band centered at around 636 nm and a less intense centered at around 585 nm. Spectral analysis show that in addition to the two main absorption bands, the absorption spectrum in the spectral range from 400 to 700 nm contains nine more absorption bands. Because to the symmetrical structure of the EBT3 radiochromic film, we assume that the additional absorption bands in the spectral range 400–540 nm are due to an interference pattern that is characteristic of a Fabry-Perot cavity.     

A radiochromic film based on leucomalachite green for high-dose dosimetry applications

A colorless polyvinyl butyral film (PVB) based on radiation-sensitive dye of leucomalachite green (LMG) was investigated as a high-dose dosimeter for gamma radiation processing applications in the dose range of 3–150 kGy. The useful applications for such dose range are food irradiation treatment, medical devices sterilization and polymer modification. Gamma irradiation of the film induces a significant intensity of green color, which can be characterized by a main absorption band at 627 nm and a small band at 425 nm. The variation in response of irradiated film stored in the dark and under laboratory light illumination was less than 3% during the first 6 days of storage. The response of film during irradiation was slightly influenced by relative humidity in the range of 12–76%; however, it was significantly affected by temperature in the range of 5–40 °C. The radiation chemical yield was reported to be 6.76 × 10⁻⁶ mol/J at the absorbed dose of 30 kGy for the film containing 6.5% of LMG dye. The overall uncertainty associated with routine dose monitoring would be less than 6% at a 95% confidence level if the dosimeter was being corrected for irradiation conditions and being calibrated with reference standard dosimeter in the production facility.     

Radiometric characterization of radiochromic gel material applied for UVA radiation dosimetry

Diverse kinds of chemical products are useful for UVA dosimetry due to chemical incitation properties of ultraviolet radiation. It was recognized and approved that radiochromic gel materials have a specific behavior under UVA radiation exposure. The relationship between the UVA dose and the variation of visible light absorbance was found to follow a second-order function with good accuracy. Specific metrological properties of the gel material for radiometric UVA dosimetry application were studied at irradiation levels simulate deferent natural solar UVA radiation levels. The behavior of the gel absorbance properties, detector linearity, induced reaction and temporal and radiometric stability at various dose rate levels were investigated. The relationship between UVA dose and changes in optical absorbance is found independent of the UVA exposure rate including the solar UVA maximum level which could be detected at sea level. The studied gel material absorbs more than 90% of UVA radiation in 1 cm of the gel thickness. Gel detector linearity was investigated over a UVA range (20-84 W/m²) which exceeds the natural solar UVA radiation level and the linearity factor was found to be close to 1 with statistical differences ≤ 2%. The UVA induced dark reaction in the gel material continues for almost 4 min after stopping irradiation; which must be considered during measurements. The detector has good temporal stability even under high UVA exposure; hence the gel absorption in the UVA spectrum region is stable. Measured deviation was less than 1%, and relative variation of gel optical absorbance in UVA spectrum is about 35 times lower than that occur in visible region.     

Characterization and optimization of EBT2 radiochromic films dosimetry system for precise measurements of output factors in small fields used in radiotherapy

The accurate determination of absorbed dose in small photon beams, especially for stereotactic radiation therapy, is a difficult task with commercially available detectors. As these small fields are characterized by high dose gradients, a lack of lateral particle equilibrium and a variation of energy spectra with beam sizes, a dosimeter with high resolution, tissue-equivalence and high precision is required. The new radiochromic film EBT2, which meets these criteria, was fully characterized in Institut de Radioprotection et Sûreté Nucléaire (IRSN) for this application. This type of film was tested with the reading system EPSON Dual Lens Perfection V700 flatbed scanner in transmission mode. Warm-up effects of the scanner were studied as well as the influence of the scanner light. Uniformity of unirradiated and irradiated EBT2 films in terms of pixel value was found to be respectively 0.3% (1 SD) and 0.5% (1 SD). An original, accurate and efficient radiochromic film dosimetry protocol was established. The overall uncertainty for dose measurement with EBT2 films using this protocol was estimated at less than 2% (1 SD). Encouraging measurements of output factors were performed on a Novalis system.     

Patterning of nanoparticulate transparent conductive ITO films using UV light irradiation and UV laser beam writing

Indium tin oxide (ITO) thin film is one of the most widely used as transparent conductive electrodes in all forms of flat panel display (FPD) and microelectronic devices. Suspension of already crystalline conductive ITO nanoparticles fully dispersed in alcohol was spun, after modifying with coupling agent, on glass substrates. The low cost, simple and versatile traditional photolithography process without complication of the photoresist layer was used for patterning ITO films. Using of UV light irradiation through mask and direct UV laser beam writing resulted in an accurate linear, sharp edge and very smooth patterns. Irradiated ITO film showed a high transparency (∼85%) in the visible region. The electrical sheet resistance decrease with increasing time of exposure to UV light and UV laser. Only 5 min UV light irradiation is enough to decrease the electrical sheet resistance down to 5 kΩ□.     

Development of a protocol for small beam bi-dimensional dose distribution measurements with radiochromic films

Gafchromic™ films have become popular due to their ease of use and their near water equivalence. This last property is crucial for stereotactic small beam dosimetry as demonstrated in recent papers. An accurate bi-dimensional dose measurement with Gafchromic™ films is very challenging mainly because of the non-uniformity response of flatbed scanners (used for films digitalization) and their own non-uniformity. The first proposal of this work is to develop bi-dimensional protocol for small beams and evaluate the associated uncertainty. The second proposal is to validate this protocol for the bi-dimensional measurements of treatment plans performed with the CyberKnife^® system.First, the uniformity of an Epson V700 flatbed scanner and a batch of EBT3 Gafchromic™ films has been investigated. A “four films” dosimeter was designed to reduce the errors (statistic and systematic) due to their non-uniformity. Then, the “four films” dosimeter protocol in both a homogeneous (RW3 material) and heterogeneous (RW3, lung-like and bone-like materials) phantoms has been used to measure the bi-dimensional dose distributions of three simple CyberKnife^® treatment plans. Two tumor locations (middle of the lung and near lung/bone interface) were considered for the heterogeneous phantom. These plans were achieved with the 10 mm fixed collimator and modeled with the PENELOPE Monte Carlo code in order to calculate accurate dose distributions. Finally, the “four films” bi-dimensional dose distributions were compared to the PENELOPE Monte Carlo simulations.Regarding the uncertainty associated to the bi-dimensional dose measurement protocol, the relative standard deviation σ_D on the dose was 1.2% in the range from 0.5 to 4.0 Gy. Regarding the protocol validation on CyberKnife^® treatment plans, a very good agreement was found with all measurement points passing the {3% - 3 mm} Gamma Index criteria.