Plasma Deposits Research Articles

Investigations on the oxidation behavior and removal mechanism of SiC/SiC composites by multi-pulse femtosecond laser ablation

SiC/SiC (SiC fiber-reinforced SiC matrix) composites have superior performance, making them promising candidates as one of the best materials for high-temperature components in aerospace applications. This investigation analyzed the morphology, structure, composition, and plasma state of multi-pulse femtosecond laser ablated SiC/SiC composites from multiple perspectives using various static and in situ characterization methods. Further, the oxidation behavior and removal mechanism of SiC/SiC composites were studied qualitatively and quantitatively. The results indicated that the ablation products of multi-pulse femtosecond laser ablation of SiC/SiC composites were mainly SiO2 and plasma deposits. The heat accumulation effect and oxidation degree at the ablation locations were enhanced accordingly as the effective ablation number or energy density increased, and the main shape of the products also changed regularly. At the same time, the material removal mechanism changed from non-thermal removal dominated to the equilibrium stage and then to thermal removal dominated. The detailed analysis of the oxidation behavior of each component in SiC/SiC composites enabled the controlled ablation of femtosecond lasers targeting the oxidation process of SiC/SiC composites. Besides, 1 MPa N2 could improve the processing efficiency of femtosecond laser for the depth and width of the groove by a maximum of about 90.40% and 104.02% in this study, respectively. Ultimately, the range of laser process parameters corresponding to multi-pulse femtosecond laser ablation of SiC/SiC composites without thermal removal as dominant was determined.

Guidelines for optimal design of radio-frequency in-vacuum coaxial transmission line for mirror cleaning service in ITER diagnostics

Several optical diagnostics in the ITER fusion reactor make use of big mirrors which are placed within the ITER vacuum vessel (VV), and therefore cannot have high accessibility. Plasma deposits developing on these mirrors may hinder the reflectivity of the mirror themselves, requiring a remote cleaning operation. The radio-frequency (RF) discharge mirror cleaning service operates a plasma discharge in the vicinity of the mirror, eroding the deposit layer and therefore cleaning the mirror remotely. In order to achieve this, RF power needs to be sent from outside the VV to the mirror, using a transmission line. Very stringent design requirements are applicable to the design of this RF line, such as vacuum compatibility, high power handling, low losses, overall matching, no cable over-heating, etc. This paper analytically addresses the design optimization of the RF mirror cleaning transmission line, taking into account ITER requirements, in order to give robust guidelines for the possible ad-hoc cable design adaptation that is to be undertaken case-by-case. The design guidelines are based on underlying transmission line theory, from which a set of design equations are drawn. The optimal design is achieved using design optimization considerations in the available design space. These guidelines are considered to be a useful design tool for optical diagnostics requiring mirror cleaning operation, and are aimed at harmonising the transmission line design procedures across the different cases.

First post-mortem analysis of deposits collected on ITER-like components in WEST after the C3 and C4 campaigns

In order to map the complex plasma footprint observed on the lower divertor of the WEST experiment after its first phase of operation, we analysed deposits collected on ITER-like Plasma Facing Units (PFUs) exposed in the C3 (deuterium plasma) and C4 (deuterium and helium plasma) campaigns. Our results show that these deposits have multilayer structures mainly composed of tungsten, oxygen, boron and carbon, whose texture and composition vary along the radial direction. These traits allowed us to identify three types of deposits: deposits rich in boron (conditioning) in the low plasma flux area further away from the strike point, deposits rich in tungsten with traces of metallic compounds (Cu, Fe, Cr, Ni, Ag) in the high plasma flux area and deposits rich in boron and tungsten in the private flux area. In addition, we found more nanoparticles, voids and tungsten oxide layers in the deposits formed during C4 in comparison to that of C3.

Study of the Interfacial Dynamic Behavior During Slat Formation Alumina on Steel Substrate by FSI/VOF

Thermal spraying involves surface treatment technologies in which a finely divided material is sprayed at high velocity and in a molten or semi-molten state onto the part to be covered. Their main application is the protection against wear, corrosion, and thermal effects. They also have functional properties (electrical, magnetic, etc.), which make them suitable for various industrial uses. The success and shelf life of plasma deposits depends to a large extent on the quality of the adhesion between the deposit and the substrate or between the lamella that constitute the deposit and which are generated by the impact of the powder particles crushing on the substrate. In this work, the spreading and solidification of an alumina particle on a substrate of the stainless-steel under the plasma projection conditions are investigated. The study is conducted by using the interaction fluid-structure (FSI) method in the ANSYS-code. This method is selected to determine the mechanical characteristics at the interface of the substrate particles during rolling. A focus is made on the increased role of the deformations developed during spreading at the surface interface of the substrate, the concentration of the stresses on the adhesion of the lamella, and consequently the coating quality.

The Clinical Impact of Proteomics in Amyloid Typing

The Clinical Impact of Proteomics in Amyloid Typing

Pathological Cardiopulmonary Evaluation of Rats Chronically Exposed to Traffic-Related Air Pollution.

Background:Traffic-related air pollution (TRAP) is made up of complex mixtures of particulate matter, gases and volatile compounds. However, the effects of TRAP on the cardiopulmonary system in most animal studies have been tested using acute exposure to singular pollutants. The cardiopulmonary effects and molecular mechanisms in animals that are chronically exposed to unmodified air pollution as a whole have yet to be studied. Additionally, sex-dependent toxicity of TRAP exposure has rarely been evaluated.Objectives:This study sought to assess the cardiopulmonary effect of chronic exposure to unmodified, real-world TRAP in both female and male rats.Methods:Four-week-old male and female rats were exposed to TRAP or filtered air for 14 months in a novel facility drawing air from a major freeway tunnel system in Northern California. Inflammation and oxidative stress markers were examined in the lung, heart, spleen, and plasma, and TRAP deposits were quantified in the lungs of both male and female rats.Results:Elemental analysis showed higher levels of eight elements in the female lungs and one element in the male lungs. Expression of genes related to fibrosis, aging, oxidative stress, and inflammation were higher in the rat hearts exposed to TRAP, with female rats being more susceptible than males. Enhanced collagen accumulation was found only in the TRAP-exposed female hearts. Plasma cytokine secretion was higher in both female and male rats, but inflammatory macrophages were higher only in TRAP-exposed male spleens.Discussion:Our results in rats suggest pathological consequences from chronic TRAP exposure, including sex differences indicating females may be more susceptible to TRAP-induced cardiac fibrosis. https://doi.org/10.1289/EHP7045

The role of methane in the formation of fullerene-like nanostructure in amorphous carbon film deposited by reactive magnetron sputtering

The formation of fullerene-like nanostructure in amorphous carbon film is an efficient way to improve the toughness without reducing the hardness of hydrogenated amorphous carbon film. In this paper, a convenient approach to regulating the growth of fullerene-like nanostructure by reactive magnetron sputtering process utilizing graphite target in mixed methane and argon plasma was reported and the role of methane in the formation of fullerene-like nanostructure in amorphous carbon film was discussed. By adjusting the degree of graphite target poisoning, fullerene-like nanostructure was successfully produced in the carbon film. In order to reveal the growth mechanism of this special structure, the structural evolution of the film and graphite target surface were studied. The results suggest that the structure of the target surface and the film are both amorphous carbon when target poisoning severely, and the fullerene-like nanostructure appears in carbon film when target poisoning slightly. However, when methane was not admitted into the chamber, the target was not poisoned, non‑hydrogenated carbon film was prepared. The structure of non‑hydrogenated carbon film is graphite-like. Therefore, that shows the important effect of target poisoning on the structure of film and methane plays an important role in the formation of fullerene-like nanostructure in amorphous carbon film. The formation of the fullerene-like nanostructure is attributed to the deposition of ionized methane on the target surface, which is introduced sp3-hybridized carbon atoms into the graphite structure, resulting in the curvature of the graphite 2D-plane. Nonetheless, when a large amount of methane plasma deposits on the target surface will cause target poisoning severely, the structure of the target surface and the film are both amorphous carbon.

Morphological alterations in endometrium after use of levonorgestrel-releasing intrauterine system: a case report

Case Report: A 44-year-old patient attended the gynecology service for routine consultation. The patient reported implantation of a levonorgestrel-releasing intrauterine system (LNG-IUS), five years ago. No macroscopic changes were seen in the uterus or in the endometrium cavity during the procedure, but an endometrial biopsy was performed. Histopathological analysis revealed an endometrium with an expanded stroma by pseudo-decidualization and mucoid (mucinous) alterations, forming small puddles of mucin, also presenting with polypoid indentations, ectatic vessels, lymphoid cell foci, including plasma cells and deposits of calcium salts. Conclusion: As the use of this type of contraceptive method becomes more usual, knowledge of LNG-IUS-induced changes becomes increasingly relevant for the assessment of its long-term efficacy and safety.

Unintentional consequences of dual mode plasma reactors: Implications for upscaling lab-record silicon surface passivation by silicon nitride

Silicon nitride (SiNx) synthesised by low-temperature plasma enhanced chemical vapour deposition (PECVD) is the most extensively used antireflection coating for crystalline silicon solar cells because of its tunable refractive index in combination with excellent levels of surface and bulk passivation. This has attracted a significant amount of research on developing SiNx films towards an optimal electrical and optical performance. Typically, recipes are first optimised in lab-scale reactors and subsequently, the best settings are transferred to high-throughput reactors. In this paper, we show that for one particular, but widely used, PECVD reactor configuration this upscaling is severely hampered by an important experimental artefact. Specifically, we report on the unintentional deposition of a dual layer structure in a dual mode AK 400 plasma reactor from Roth & Rau which has a significant impact on its surface passivation performance. It is found that the radio frequency (RF) substrate bias ignites an unintentional depositing plasma before the ignition of the main microwave (MW) plasma. This RF plasma deposits a Si-rich intervening SiNx layer (refractive index = 2.4) while using a recipe for stoichiometric SiNx. This layer was found to be 18 nm thick in our case and had an extraordinary impact on the Si surface passivation, witnessed by a reduction in effective surface recombination velocity from 22.5 to 6.2 cm/s. This experimental result may explain some “out of the ordinary” excellent surface passivation results reported recently for nearly stoichiometric SiNx films and has significant consequences when transferring these results to high-throughput deposition systems.

Urinary Exosomes Detect Amyloidogenic Light Chain in Patients Who Have Renal Progression Despite a Hematologic Complete Response

Background: Immunoglobulin light chain (AL) amyloidosis is a fatal complication of B-cell clonal proliferation. Currently, the best biomarker for treatment monitoring is serum free light chain (FLC) assay. Despite its higher sensitivity, it cannot distinguish clonality thus ultralow levels of monoclonal gammopathy can be missed. Urinary exosomes (UExs) are the smallest members of the extracellular vesicle family that are excreted in the urine. They exhibit different characteristics in patients with AL amyloidosis vs multiple myeloma. This study was undertaken to determine if urinary exosomes have different characteristics in patients AL amyloidosis who progress despite being in complete response (CR) vs those who have a renal response.Methods: UEx were extracted from 4 patients at different stages of AL (Table 1). Immunoglobin light chains (LC) were identified in the UEx using western blotting. Intact immunoglobulin light chains were identified in plasma, UEx, and kidney biopsy amyloid deposits using mass spectrometry (MS). cDNAs from bone marrow plasma cells (BMPC) collected at the time of diagnosis from patient 4 were sequened.Results: Oligomeric LC (250 kd) were identified in the UEx of patient 1 (newly diagnosed, Fig 1a) and 4 (renal progression in CR, Fig 1d) but only monomeric LC (25 kd) were detected in patient 2 (Fig 1b) and 3 (CR and renal response, Fig 1c). MS of the UEx and plasma of patient 4 detected 2 monoclonal λ LC. The mass of one of the LC was consistent with a lambda 6a LC which is also the most common cDNA (IGLV-6-57) found in the BMPC. Amino acid sequences derived from the tryptic digestion of the amyloid deposits matched the predicted sequence of the cDNA. The calculated weight of the peptide produced by the cDNA (23,304 Da ) was within margin of error of the mass of the lambda 6a LC (23,306 Da). The mass of the second LC (23,092 Da) was consistent with a λ4/λ5 LCs. A search of the amino acid and cDNA sequences failed to identify any similarity. The density ratio of the oligomeric LC to monomeric LC in the UEx was 0.47 which was similar to the intensity ratio by MS of the lambda 6a LC (23,306 Da) to the 23,092 Da LC in the blood (0.43).Discussion: Urinary EXs identified oligomeric LC in a patient with progressive renal disease despite achieving a CR. The mass one of the λ LC matched the predicted peptide product of the cDNA obtained from BMPC. The amino acid sequence predicted by the cDNA matched the trypsin digested sequences from the amyloid deposits. This strongly suggests the oligomeric LC represents the amyloidogenic λ6a LC detected in the blood which was being produced by the BMPC clone which is being deposited as amyloid in the kidney. The origin of the second λ LC is unknown but is likely a new monoclonal gammopathy of undetermined significance that developed after the initial bone marrow biopsy. The blood and urine samples were obtained 3 years after the BMPC. The development of a new monoclonal gammopathy in patients with plasma cell dyscrasia is not uncommon. Unfortunately, bone marrow biopsy collected at the time of the urine and blood sample had insufficient number of plasma cells (CR) for analysis.Conclusion: UEx can identify amyloidogenic LC even when current standard methods could not. The persistent presence of the amyloidogenic LC helps explain why patients can progress despite being in CR. The presence of a second λ LC which was not part of the amyloid deposit also has clinical implication. It may explain why some patients do well despite having a persistent monoclonal protein. If these results are confirmed, UEx may have a powerful role in the determination of organ and hematologic response in patients with AL amyloidosis. [Display omitted] [Display omitted] DisclosuresDispenzieri:Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Prothena: Membership on an entity's Board of Directors or advisory committees; Alnylam: Research Funding; GSK: Membership on an entity's Board of Directors or advisory committees; pfizer: Research Funding; Jannsen: Research Funding; Celgene: Research Funding.

Characterisation of Diamond-Like Carbon (DLC) laser targets by Raman spectroscopy

The search for target materials suitable for High Power Laser Experiments at ultralow thicknesses (below ten nanometres) is ongoing. Diamond-Like Carbon is investigated as an answer for a low-Z material that can survive target chamber pump-down and laser prepulse. DLC was produced using Plasma-Enhanced Chemical Vapour Deposition, using with varying gas flow mixtures of argon and methane. The methane plasma deposits amorphous carbon onto the substrate and the argon plasma re-sputters the weakly bonded carbon leaving a high proportion of diamond-like bonding. Bonding natures were probed using Raman spectroscopy; analysis of the resulting spectrum showed that flow rates of 40sccm/60sccm methane to argon produced DLC films with a diamond-like (sp3) content of ∼20%. Increasing the methane gas flow decreased this value to less than 5%. DLC foils were processed into laser targets by method of float off; using a sodium chloride release layer and lowering into water, this was then lifted onto an array of apertures allowing for laser irradiation of the material with no backing. DLC with 20% sp3 content showed superior yield when compared to other materials such as metals and some plastics of the same thickness, with ∼70% of the target positions surviving the float off procedure at <10nm. As a result of this work DLC targets have been available for a number of experiments at the Central Laser Facility.

Comparison of blood microsampling with DBS and conventional blood collection techniques used in a midazolam biostudy.

Quantitative DBS LC-MS/MS assay for midazolam was used to compare two sample collection techniques (venipuncture and finger prick) and the midazolam concentrations measured in plasma samples, DBS and dried plasma spots. Midazolam was extracted from DBS cards and compared with whole blood collected from usual venipuncture. Dried plasma spots were also compared with plasma. The blood volume used as well as the temperature impact during the blood and plasma deposits was evaluated. Midazolam was administrated to six healthy subjects during a clinical trial to obtained blood and plasma samples for the statistical comparison. The method for midazolam using DBS was validated and showed an excellent performance. Excellent correlations were observed when the same collection procedures were used.

Dielectric properties of CaTiO3 coatings prepared by plasma spraying

This paper presents a study of dielectric properties, namely the relative permittivity and loss factor dependence on the frequency of a weak electric field. Perovskite CaTiO3 was studied in the form of coatings and self-supporting plates made by plasma spraying. A conventional gas stabilised plasma gun (GSP) as well as a water stabilised plasma gun (WSP) were employed. It was observed that plasma sprayed titanates exhibit a strong relaxation of permittivity and loss factor decrease with a frequency rise. These properties are influenced by spray technique and spraying parameters, but the relaxation character in general is preserved in all cases. The volume resistivity of the samples was studied as well. Several aspects of the structural features of plasma deposits, especially the phase composition, porosity character, and their influence on dielectric properties are discussed.

Immobilization of Heparan Sulfate on Electrospun Meshes to Support Embryonic Stem Cell Culture and Differentiation *

As our understanding of what guides the behavior of multi- and pluripotent stem cells deepens, so too does our ability to utilize certain cues to manipulate their behavior and maximize their therapeutic potential. Engineered, biologically functionalized materials have the capacity to influence stem cell behavior through a powerful combination of biological, mechanical, and topographical cues. Here, we present the development of a novel electrospun scaffold, functionalized with glycosaminoglycans (GAGs) ionically immobilized onto the fiber surface. Bound GAGs retained the ability to interact with GAG-binding molecules and, crucially, presented GAG sulfation motifs fundamental to mediating stem cell behavior. Bound GAG proved to be biologically active, rescuing the neural differentiation capacity of heparan sulfate-deficient mouse embryonic stem cells and functioning in concert with FGF4 to facilitate the formation of extensive neural processes across the scaffold surface. The combination of GAGs with electrospun scaffolds creates a biomaterial with potent applicability for the propagation and effective differentiation of pluripotent stem cells.

Goodpasture Antigen-binding Protein/Ceramide Transporter Binds to Human Serum Amyloid P-Component and Is Present in Brain Amyloid Plaques

Serum amyloid P component (SAP) is a non-fibrillar glycoprotein belonging to the pentraxin family of the innate immune system. SAP is present in plasma, basement membranes, and amyloid deposits. This study demonstrates, for the first time, that the Goodpasture antigen-binding protein (GPBP) binds to human SAP. GPBP is a nonconventional Ser/Thr kinase for basement membrane type IV collagen. Also GPBP is found in plasma and in the extracellular matrix. In the present study, we demonstrate that GPBP specifically binds SAP in its physiological conformations, pentamers and decamers. The START domain in GPBP is important for this interaction. SAP and GPBP form complexes in blood and partly colocalize in amyloid plaques from Alzheimer disease patients. These data suggest the existence of complexes of SAP and GPBP under physiological and pathological conditions. These complexes are important for understanding basement membrane, blood physiology, and plaque formation in Alzheimer disease.

Role of Positive Ions in Determining the Deposition Rate and Film Chemistry of Continuous Wave Hexamethyl Disiloxane Plasmas

New data shed light on the mechanisms of film growth from low power, low pressure plasmas of organic compounds. These data rebalance the widely held view that plasma polymer formation is due to radical/neutral reactions only and that ions play no direct role in contributing mass at the surface. Ion reactions are shown to play an important role in both the plasma phase and at the surface. The mass deposition rate and ion flux in continuous wave hexamethyl disiloxane (HMDSO) plasmas have been studied as a function of pressure and applied RF power. Both the deposition rate and ion flux were shown to increase with applied power; however, the deposition rate increased with pressure while the ion flux decreased. Positive ion mass spectrometry of the plasma phase demonstrates that the dominant ionic species is the (HMDSO-CH(3))(+) ion at m/z 147, but significant fragmentation and subsequent oligomerization was also observed. Chemical analysis of the deposits by X-ray photoelectron spectroscopy and secondary ion mass spectrometry show that the deposits were consistent with deposits reported by previous workers grown from plasma and hyperthermal (HMDSO-CH(3))(+) ions. Increasing coordination of silicon with oxygen in the plasma deposits reveals the role of ions in the growth of plasma polymers. Comparing the calculated film thicknesses after a fixed total fluence of 1.5 × 10(19) ions/m(2) to results for hyperthermal ions shows that ions can contribute significantly to the total absorbed mass in the deposits.

Plasma Polymerization of Zinc Acetyl Acetonate for the Development of a Polymer‐based Zinc Release System

AbstractGrowing interest in novel materials for biomedical applications has promoted the investigation of composite materials that involve metal ions or metallic nanoparticles embedded in an organic polymeric matrix. The aim of the current work was the development of metal containing thin organic films, the material characterization and a study of the metal release properties when immersed in aqueous solution. Using a multitude of standard surface analytical tools and sophisticated optical techniques it could be shown that the plasma deposits of zinc acetylacetonate consist of nanometre‐sized ZnO particle inclusions in a highly oxygenated organic matrix. Infrared reflection absorption spectroscopy suggests some retention of the complex structure of the monomer. This is lost upon immersion in water as the zinc is released into the surrounding solution. The amount of zinc in the film and its release was shown to be dependent on the plasma conditions used and the thickness of the film. The ultimate goal of this study is the development of a zinc metal release system showing antimicrobial properties. magnified image

Sliding wear characterization of microwave-glazed plasma-sprayed ceramic composites

The main objective of the present study is to present the wear characteristics of post-processed plasma deposits of alumina-titania (AT-13) ceramic composites under high-speed sliding. Spray deposits were post-processed (microwave glazed) by way of exposing them to microwave radiation at a frequency of 2.45 GHz in a multi-mode cavity by using the microwave hybrid heating principle. During ‘microwave glazing’, densification of the coating's structure takes place as a consequence of microwave-heating-induced phase transformation, leading to significant enhancement in hardness and reduction in porosity. Responses of the as-sprayed and microwave-glazed composites were monitored while they were subjected to sliding type of tribocontact at a speed of 5 m/s. Subsequent analyses are presented in terms of wear rate, pressure-velocity-time ( p- v- t) characteristics, fractography, elemental count, and acoustic emission (AE) emanated during the trials. The results show a steady sliding wear response after an initial higher rate. The p- v- t factor analysis confirms a better operating condition with glazed composites. Glazed composites exhibit higher stability towards elemental transfer between the wear surface and the counter surface. AEs emanating during trials indicate deformation and brittle fracture as the dominating wear mechanisms of the as-sprayed and microwave-glazed ceramic composites.

Macroscopic control of plasma polymerization processes

Abstract Plasma polymerization covers a broad range of plasma deposits from soft to hard coatings. Nanoscale coatings are formed within a dry and eco-friendly process on different substrate materials and structures. To gain a deeper insight into plasma polymerization, a macroscopic approach using the concept of chemical quasi-equilibria might be useful. Following this macroscopic approach, the reaction parameter power input per gas flow W/F, which represents the specific energy invested per particle within the active plasma zone, solely determines the mass deposition rate. Hence, plasma polymerization can be described by measuring the deposited mass and examining the power input and gas flow which contributes to it. Thus, the control, investigation, and up-scaling of plasma polymerization processes are enabled. Different examples are given to make use of the macroscopic approach.

Pulsed and Continuous Wave Acrylic Acid Radio Frequency Plasma Deposits: Plasma and Surface Chemistry

Plasma polymers have been formed from acrylic acid using a pulsed power source. An on-pulse duration of 100 micros was used with a range of discharge off-times between 0 (continuous wave) and 20,000 micros. X-ray photoelectron spectroscopy (XPS) has been used in combination with trifluoroethanol (TFE) derivatization to quantify the surface concentration of the carboxylic acid functionality in the deposit. Retention of this functionality from the monomer varied from 2% to 65%. When input power was expressed as the time-averaged energy per monomer molecule, E(mean), the deposit chemistry achieved could be described using a single relationship for all deposition conditions. Deposition rates were monitored using a quartz crystal microbalance, which revealed a range from 20 to 200 microg m(-2) s(-1), and these fell as COOH functional retention increased. The flow rate was found to be the major determinant of the deposition rate, rather than being uniquely defined by E(mean), connected to the rate at which fresh monomer enters the system in the monomer deficient regime. The neutral species were collected in a time-averaged manner. As the energy delivered per molecule in the system (E(mean)) decreased, the amount of intact monomer increased, with the average neutral mass approaching 72 amu as E(mean) tends to zero. No neutral oligomeric species were detected. Langmuir probes have been used to determine the temporal evolution of the density and temperature of the electrons in the plasma and the plasma potential adjacent to the depositing film. It has been found that even 500 micros into the afterglow period that ionic densities are still significant, 5-10% of the on-time density, and that ion accelerating sheath potentials fall from 40 V in the on-time to a few volts in the off-time. We have made the first detailed, time- and energy-resolved mass spectrometry measurements in depositing acrylic acid plasma. These have allowed us to identify and quantify the positive ion species in the acrylic acid plasma during both the on- and the off- periods. The relative intensities of oligomeric species of the type [nM + H]+ as large as n = 3 were observed to increase in the off-time suggesting vapor phase polymerization after power input to the plasma was ceased. The energy distribution functions of these ions demonstrated that they were produced in the plasma in both the on- and the off-times. This remarkable observation contradicts the assumptions usually made when speculating on pulsed plasma that ions have very short lifetimes, although it is anticipated that radicals still have significantly longer lifetimes, estimated from calculation to be in excess of 1 ms. The increase in average positive ion mass during the off-period can be related to the lower mobility of the heavier components, reducing their relative loss to surfaces, and the polymer chain growth in the gas phase due to the ion-neutral collisions. The implications of these observations are discussed in light of polymerization mechanisms proposed from continuous acrylic acid and millisecond pulsing plasmas.