Observation of diffusion through ion irradiated Makrofol KG

The features of the latent track in polycarbonate can be analysed by measuring the diffusion constant under ultra high vacuum conditions. Stacks of 30 μm Makrofol KG foils were irradiated with uranium ions of 11.4 MeV/u at the GSI Darmstadt, Germany. We used different fluences from 3·10¹⁰ to 5·10¹¹ ions/cm². The diffusion constant was determined by the time-lag-method [1]. A quadrupole mass filter was used to observe the diffusion of the gas. We measured the diffusion of argon through different foils of each stack at room temperature. In all cases also unirradiated foils were measured. The dependence of the permeability and the diffusion constant on the ion fluence and the energy loss of the ions will be given and indications on the size of latent ion tracks concerning gas diffusion will be discussed.     

Energy loss dependent transversal etching rates of heavy ion tracks in plastic

By the method of electrolytical etching track etching rates V_t and corresponding transversal track etching rates V_trans of single heavy ion tracks in thin Makrofol KG foils have been measured at ion energies from 10–480 MeV/u. Makrofol KG foils of 8 μm thickness were irradiated perpendicular to the surface with ⁷⁹Au and ⁵⁴Xe ions at specific energies with energy loss values of REL=(10–90) ^*10³ MeVcm²/g at GSI Darmstadt, Germany, and Lawrence Berkeley Lab., Cal., USA. Using the electrolytical etching method by measuring the resistance of the foil during the etching process (etching conditions: 6n NaOH, room temperature and controlled 50° C) the breakthrough time and track etching rates V_t, V_trans and V_m (bulk etching rate) were analysed. Response curves (V_t/V_m)-1 as a function of Restricted Energy Loss (REL), the maximum extension of the ion induced damage perpendicular to the ion path and the dimension of the ion track core depending on the deposited energy can be estimated.     

The statistical process of pore growth in multi pore foils

Using the electrolytical etching method the breakthrough-times (i.e. the time when the two etched cones from both sides of the detector contact) and the resulting track etching rates v_t of heavy ion tracks in 8 μm polycarbonate Makrofol KG have been measured. The samples were irradiated at the GSI, Darmstadt (Germany) with gold ions and different fluences at a specific energy of 11.6 MeV/u. All foils were etched in 6 n NaOH at room temperature. Fluctuations of breakthrough-times of single pore foils were analysed. Also the breakthrough-time of multi-pore-foils were measured. The dependence of the mean breakthrough-time on the ion fluence is dicussed. This dependence will be explained by the fluctuations of the breakthrough-time of the pores.     

Free radicals inhibitor effect on makrofol E nuclear tracks. Preliminary data

Thin foils of Makrofol E prepared with and without inclusion of a free radical scavenger (DPPH), were irradiated at the Tandar facilities. 374 keV and 50 keV ¹⁶O⁺⁺ ions from a Varian Ion Implanter and ⁷Li⁺ ions at different energies from a Tandem accelerator were used. Replicas of the etched foils were observed by transmission electron microscopy.

Track 3iameters exhibited a slight difference between the treated and untreated foils in the case of irradiation with ¹⁶O ions. A larger difference between the groups in the case of ⁷Li ions was found.     

Some relations of the diffusion constant of latent tracks in polymers and the ion energy loss

Measurements of the diffusion constant and the permeability of ion irradiated Makrofol KG (polycarbonate) sheets have been done with Argon and Nitrogen as diffusion gas. The polymers were irradiated at the “Gesellschaft für Schwerionenforschung” (GSI, Germany) with Uranium and Gold ions with energies of about 10 MeV/nuc. The fluence varies from 3·10⁹ to 4·10¹¹ ions/cm². For the irradiation the material was put together in stacks with layers of 8 μm thickness. This allows to relate a definite amount of energy loss to each layer and to examine the dependence of the diffusion constant and the permeability on it. For comparison electron irradiated and pristine material (i.e. the untreated material) were also measured.

The general tendency shows an increase of the diffusion constant and the permeability with growing energy loss up to a certain limit. In case of the highest energy loss the material changes its appearance and the diffusion constant and the permeability values are remarkable lower than those of the pristine material. A first trail of explanation might give the three-zone-model presented in this paper.     

Ionizing particles may create shockwaves

To find a model that describes the gas diffusion on irradiated polymers (Makrofol KG polycarbonate) the diffusion constants have been measured with argon as diffusion gas. The polymers were irradiated with uranium, gold and lead ions of about 10 MeV/u and ion fluences between 1×10¹⁰ and 4×10¹¹ ions/cm². The ion irradiated probes show two quite different dependencies of the diffusion constant on the ion energy loss. These effects are strongly related to the fluence of the irradiation. In case of low ion fluences, the diffusion constant is up to 8 times higher than that of pristine material. In the probes with high ion fluences we observe a decrease of diffusion constant to half the value of the pristine material. To understand the dependence of the diffusion constant on ion fluences we apply a model of compacting. This model describes the compacting ability of shockwaves arising from latent tracks. A track formation model is suggested. When an ion penetrates the foil it creates shockwaves around its path. These shockwaves put compacting forces on earlier created latent tracks in the same foil.     

Enhancement of the superconducting critical temperature Tc of niobium by radiation damage

5 μm niobium foils were irradiated with 25 MeV oxygen ions at 20 K, 33 K and 145 K up to fluences of 1.3 × 10¹⁶cm^-2 corresponding to a damage rate decrease of 99%. T_c versusresistivity shows a minimum depending on the irradiation temperature. At high fluences and subsequent annealing T_c is enhanced compared to the unirradiated value and the transition is broadened by a factor of about 30.     

Optical transparency of makrofol nuclear track filters

Makrofol polycarbonate—one of the widely used materials for making nuclear track filters, has been studied for its transparency to light (Λ = 350 nm to 950 nm). Also the optical transmission and IR-spectroscopy results on the Makrofol foils, forming nuclear track filters by irradiating with 14 MeV/n ²³⁸U ions, with and without post-irradiation UV and γ-exposures, are presented. Studies have been extended to these filters to investigate the variation of percentage transmission with etch-time, pore diameter, at different values of Λ.     

Opto-chemical response of Makrofol-KG to swift heavy ion irradiation

In the present study, the effects of swift heavy ion beam irradiation on the structural, chemical and optical properties of Makrofol solid-state nuclear track detector (SSNTD) were investigated. Makrofol-KG films of 40 μm thickness were irradiated with oxygen beam (O^8 +) with fluences ranging between 10¹⁰ ion/cm² and 10¹² ion/cm². Structural, chemical and optical properties were investigated using X-ray diffraction, FTIR spectroscopy and UV–visible spectroscopy methods. It is observed that the direct and indirect band gaps of Makrofol-KG decrease after the irradiation. The XRD study shows that the crystalline size in the films decreases at higher fluences. The intensity plots of FTIR measurements indicate the degradation of Makrofol at higher fluences. Roughness of the surface increases at higher fluence.     

Influence of light-ion irradiation on the heavy-ion track etching of polycarbonate

We report on the effect of light-ion irradiation on the size distribution of etched tracks produced by medium energy heavy-ions in polycarbonate. Makrofol KG polycarbonate foils were treated with 2 MeV H⁺ ions at different fluences φ either before or after a short irradiation with 18 MeV Au⁷⁺. The heavy ion irradiation was used to produce the latent tracks in the foils and the proton beam acted as a perturbation to the matrix. The proton irradiation causes initially a decrease in the mean etched pore size, as compared to samples only bombarded by Au ions, reaching a minimum at H⁺ fluences around 2–5×10¹³ cm⁻², while at higher φ the pore size starts to grow again. This effect is attributed to the action of two competitive processes that dominate in different fluence regimes. The decrease in the pore radii at low fluences is attributed to an increase in crystallinity induced by the proton beam. As the total dose builds up, this effect is surpassed by chain scission and amorphization that grow at a lower rate and cause the pore radii to increase again.     

Structural and optical studies of electron beam-irradiated Makrofol nuclear track detector

The effect of electron beam irradiation on the structural and optical properties of Makrofol solid state nuclear track detector (SSNTD) was investigated. Samples from Makrofol detector were irradiated with electron beam with doses at levels between 10 and 400 kGy. Structural and optical property studies using X-ray diffraction, FTIR spectroscopy, color difference measurements and electron paramagnetic resonance were performed on non-irradiated and irradiated Makrofol samples. The transmission of these samples in the wavelength range 200–2500 nm, as well as any color changes, was studied. A characteristic absorption bands with different intensities was observed. Using the transmission data, both the tristimulus and the Commission Internationale de l’Eclairage (CIE) LAB coordinate values were calculated. In addition, the color differences between the non-irradiated sample and those irradiated with different doses were calculated. The results indicate that the Makrofol detector is a material that does not have a high resistance to degradation, and its tendency to crosslinking is much lower than that of several other SSNTDs.     

Stopping power of 1.0–2.6 MEV protons in Mylar, Makrofol and cellulose nitrate foils

Stopping powers of 1.0 – 2.6 MeV protons in Mylar, Makrofol and Cellulose nitrate were measured. The results have been compared with scanty experimetnal data in the literature and with calculated values obtained by using the TRIM 92 computer code. These values agree well with each other within uncertainties. In the case of Mylar and LR 115, maximum deviations of 9.5% and 4.5% from the semi-emperical curves were observed. In the case of Makrofol foils, a maximum deviation of 3% was found. Considering the accuracy of theories this discrepancy is not that significant.     

The radial etching velocity for tracks in polymer film

Here we have made an attempt to describe etching along and perpendicular to the ion track axis with the many-hit response model. From experiments where sheets of Makrofol KG film were exposed to Au and Xe ions it was found that V_t/V_b depends on restricted energy loss (REL). Then, for the many-hit model the registration parameters of the detectors were found and were used for the calculation of the radial distributions of the transversal etching rate and were compared with experimental data.     

A passive radon dosimeter based on the combination of a track etch detector and activated charcoal

The aim of this work is to test a combination of a Makrofol track detector with a new type of charcoal (Carboxen-564) to design a personal radon dosimeter. The intention is to use this dosimeter as a personal radon dosimeter to measure the monthly radon exposure in workplaces, especially when the occupancy is not ecactly known. The proposed combination was exposed to low and high concentrations of radon in a large range of relative humidity (RH). For the optimal layer thickness, a charcoal bed of 2.2 mm, a specific track density of 5.1 tracks cm⁻²/kBq h m⁻³ was obtained. For a monthly working exposure (170 h) at an average radon concentration of 100 Bq/m³, this means 87 tracks/cm² or 10 times the background of the Makrofol detector, with a statistical uncertainty of 15%.     

热峰模型在聚碳酸酯非晶化潜径迹中的应用

为了描述快重离子在聚合物中的潜径迹行为，用不同能量的快重离子 (1158GeVFe5656,1755GeVXe136¹³⁶及2636GeVU238²³⁸) 辐照 叠层半结晶聚碳酸酯膜 (Makrofol KG型)，结合x射线衍射测量技术，在较宽的电子能损 (1 9—171keV/nm)和离子注量（5×1010¹⁰—3×1012¹² cm-2^-2）范围研究了离子在半 关键词： 离子辐照 聚碳酸酯 非晶化 潜径迹     

分子动力学模拟钠硼硅酸盐玻璃电子辐照诱导的结构演化效应

钠硼硅酸盐玻璃作为高放射废物玻璃固化体的候选材料之一,已有大量实验对该类玻璃开展了电子或重离子的辐照效应研究.然而,在理论计算与模拟方面的工作却很少,目前主要集中于重离子的辐照效应,对电子的辐照效应的模拟尚未见报道.本文利用分子动力学工具提出一种新的方法,以实现对电子辐照诱导的玻璃结构演化进行模拟.该方法基于实验中玻璃的结构变化特点,即实验中的拉曼结果已经证实:在大剂量的电子辐照后的玻璃中存在分子氧的事实,由于这些分子氧不会与其他粒子发生相互作用,因而可以通过从体系中逐步地移除一定数量氧原子的方式,以达到模拟大剂量电子辐照的情形,进而得到电子辐照后的玻璃的结构信息.模拟结果显示:随着移除氧原子的数量增加,玻璃中的Si—O—Si平均键角逐渐减小;而且玻璃中的小环数量会因氧的逐渐减少而逐渐增加;玻璃中部分[BO4]结构会转变为[BO3]结构,最终这种转变会达到饱和;大量移除氧之后,玻璃中的钠元素也出现明显的相分离.这些模拟辐照的玻璃结构特性能较好地与实验中的硼硅酸盐玻璃电子辐照诱导的结构变化符合.因此,本文提出的方法有望为通过分子动力学模拟硼硅酸盐玻璃的电子辐照效应提供新思路.     

Effect of gamma irradiation on the structural,thermal and optical properties of Makrofol BL 2–4

Makrofol BL 2–4 is an extrusion film based on Makrolon polycarbonate. It comprises excellent die-cutting performance combined with high light transmission and moderate light scattering properties. It is a class of polymeric solid state nuclear track detectors which has many applications in various radiation detection fields. In the present work, Makrofol samples were irradiated using different gamma doses ranging from 10 to 350 kGy. The structural modifications in the gamma-irradiated Makrofol samples have been studied as a function of dose using different characterization techniques such as X-ray diffraction, intrinsic viscosity, Fourier transform infrared spectroscopy, thermogravimetric analysis, refractive index and color difference studies. The gamma irradiation in the dose range 20–200 kGy led to a more compact structure of Makrofol polymer, which resulted in an improvement in its thermal stability with an enhancement in its structural and optical properties.     

Gamma induced changes in the structural and optical properties of Makrofol LS 1–1 polycarbonate

ABSTRACT

Samples from sheets of the polymeric material Makrofol LS 1–1 have been exposed to gamma radiation in the dose range 10–250?kGy. The modifications induced in Makrofol samples due to gamma irradiation have been studied through different characterization techniques such as intrinsic viscosity as a measure of the average molecular mass, Fourier Transform Infrared spectroscopy FTIR, refractive index and color difference studies. The results indicate that the crosslinking dominates at the dose range 50–250?kGy. The crosslinking reported by viscosity measurements is supported by the trend of the function groups present in the sample with the gamma dose. Also, the increase in intrinsic viscosity indicating an increase in the average molecular mass was associated with an increase in the refractive index. Additionally, the non-irradiated Makrofol samples showed significant color sensitivity towards gamma irradiation. The color intensity ΔE, which is the color difference between the non-irradiated sample and those irradiated with different gamma doses, increased (0–5.56) with increasing the dose up to 250?kGy, convoyed by an increase in the red and yellow color components.     

Surface and Bulk Structure Characterization of Proton (3 MeV) Irradiated Polycarbonate

Polycarbonate (Makrofol‐N) thin films were irradiated with protons (3 MeV) under vacuum at room temperature with the fluence ranging from 1×10¹⁴ to 1×10¹⁵ protons cm^?2. The change in surface morphology, optical properties, degradation of the functional groups, and crystallinity of the proton‐irradiated polymers were investigated with atomic force microscopy (AFM), UV‐VIS, and Fourier‐transform infrared (FTIR) spectroscopy, and X‐ray diffraction (XRD) techniques, respectively. AFM shows that the root mean square (RMS) roughness of the irradiated polycarbonate surface increases with the increment of ion fluence. The UV‐VIS analysis revealed that in Makrofol‐N the optical band gap decreased by 30% at highest fluence of 1×10¹⁵ protons cm^?2. The band gap can be correlated to the number of carbon atoms, M, in a cluster with a modified Robertson's equation. The cluster size in the proton‐irradiated Makrofol‐N increased from 112 to 129 atoms with the increase of fluence from 1×10¹⁴ to 1×10¹⁵ protons cm^?2. FTIR spectra of proton (3 MeV) irradiated Makrofol‐N showed a strong decrease of almost all absorption bands at about 1× 10¹⁴ protons cm^?2. However, beyond a higher critical dose an increase in intensity of almost all characteristic bands was noticed. The appearance of a new peak at 3,500 cm^?1 (‐OH groups) was observed at the higher fluences in the FTIR spectra of proton‐irradiated polycarbonate. XRD measurements showed an increase of full width at half maximum (FWHM) and the average intermolecular spacing of the main peak, which may be due to the increase of chain scission and the introduction of ‐OH groups in the proton irradiated polycarbonate.     

Study of latent and etched tracks by a charged particle transmission technique

A recently suggested technique for non-destructive investigation of inhomogeneities in thin objects, which is based on the measurement of the energy spectra of charged particles transmitted through the object, is used for the study of thermal annealing of 10–20 μm thick polyethylene terephtalate, polypropylene and polycarbonate foils irradiated with 1–10 MeV/amu heavy ions. At elevated temperature a foil linear contraction is observed on pristine and irradiated material. Also the foil roughness increases with increasing temperature. On the same foils with etched pores 0.5–1.0 μm in diameter, the thermal annealing results in gradual closing of the pores up to about 30% of their initial diameter at the temperatures of 150–175°C. At higher temperatures the pore diameter increases and achieves its initial value.