CR-39 Sheets Research Articles

Spectrally resolved ion imaging from laser produced plasmas using CR-39 detectors

Intense laser-produced plasmas generate bright, ultrashort bursts of accelerated ions. Reducing the required laser intensity and increasing the repetition rate of the laser to generate high energy ions is important, and mesoscopic particle targets are an attractive option to address this issue. Newer experimental strategies to measure ion energies and their angular distribution are needed in studies of such systems. In this paper, we outline a method to simultaneously measure these quantities using a single CR39 film. Although CR-39 detectors are known for ion imaging or spectroscopy, combining these specially for lower ion energies and applications to low-intensity laser experiments is not common. The paradigm chosen in our study is to consider the spatial distribution of nuclear tracks on a CR-39 sheet, while simultaneously separating them by their track diameter. Our method achieves an energy resolution of about 100 keV and a spatial resolution of tens of micrometers. In addition, ion species other than protons, i.e., carbon and oxygen, can also be imaged in an energy-resolved manner.

Real-time single-ion hit position detecting system for cell irradiation

We have developed a real-time single-ion hit position detecting system to replace a CR-39 solid-state nuclear-track detector for cell irradiation experiments because the CR-39 takes several minutes for off-line etching. The new real-time system consists of a 500-μm-thick CaF2(Eu) scintillator, an optical microscope with a 10× objective lens, and a high-gain charge-coupled device camera. Each of the 260-MeV neon ions passing through a 100-μm-thick CR-39 sheet was detected using the real-time system in a performance test for the spatial resolution. The full width at half maxima (FWHMs) of the distances between positions detected by the real-time system and the centers of the etch pits on CR-39 were 6.5 and 6.9μm in the x and y directions, respectively. The result shows that the system is useful for typical cultured cells of a few tens of micrometers in size.

Characterization of non-tuberculosis mycobacteria by neutron radiography

The genus Mycobacterium shares many characteristics with Corynebacterium and Actinomyces genera, among which the genomic guanine plus cytosine content and the production of long branched-chain fatty acids, known as mycolic acids are enhanced. Growth rate and optimal temperature of mycobacteria are variable. The genus comprises more than 140 known species; however Mycobacterium fortuitum, a fast growing nontuberculous mycobacterium, is clinically significant, because it has been associated to several lesions following surgery procedures such as liposuction, silicone breast and pacemaker implants, exposure to prosthetic materials besides sporadic lesions in the skin, soft tissues and rarely lungs. The objective of the present study is to reduce the time necessary for M. fortuitum characterization based on its morphology and the use of the neutron radiography technique substituting the classical biochemical assays. We also aim to confirm the utility of dendrimers as boron carriers. The samples were sterilized through conventional protocols using 10% formaldehyde. In the incubation process, two solutions with different molar ratios (10:1 and 20:1) of sodium borate and PAMAM G4 dendrimer and also pure sodium borate were used. After doping and sterilization procedures, the samples were deposited on CR-39 sheets, irradiated with a 4.6×105n/cm2s thermal neutron flux for 30min, from the J-9 irradiation channel of the Argonauta IEN/CNEN reactor. The images registered in the CR-39 were visualized in a Nikon E400 optical transmission microscope and captured by a Nikon Coolpix 995 digital camera. Developing the nuclear tracks registered in the CR-39 allowed a 1000× enlargement of mycobacterium images, facilitating their characterization, the use of more sophisticated equipment not being necessary. The use of neutron radiography technique reduced the time necessary for characterization. Doping with PAMAM dendrimer improved the visualization of NTM in neutron radiography images.

Effect of X-Ray Radiation on Electro-Optical Characteristics of CR-39 Sheets by Using Microwave and FTIR Spectroscopy Techniques

Effect of X-Ray Radiation on Electro-Optical Characteristics of CR-39 Sheets by Using Microwave and FTIR Spectroscopy Techniques

An imaging technique for detection and absolute calibration of scintillation light

Triggered by the need of a detection system to be used in experiments of nuclear fusion in laser-generated plasmas, we developed an imaging technique for the measurement and calibration of the scintillation light yield of scintillating materials. As in such experiments, all the reaction products are generated in an ultrashort time frame, the event-by-event data acquisition scheme is not feasible. As an alternative to the emulsion technique (or the equivalent CR39 sheets) we propose a scintillating screen readout by means of a high performance charge coupled device camera. Even though it is not strictly required in the particular application, this technique allows the absolute calibration of the scintillation light yield.

Calibration of CR-39 with monoenergetic protons

Calibration of solid state nuclear track detector CR-39 was carried out with very low-energy monoenergetic protons of 20–100 keV from a Cockcroft Walton accelerator. To reduce the beam of the proton from the accelerator, a novel method was adopted by means of a high voltage pulse generator. The irradiation time of the proton beam on each CR-39 sheet was shortened to one pulse with duration of 100 ns, so that very separated proton tracks around 10 4 cm - 2 can be irradiated and observed and measured on the surface of the CR-39 detector after etching. The variations of track diameter with etching time as well as with proton energy response curve has been carefully calibrated for the first time in this very low energy region. The calibration shows that the optical limit for the observation of etched tracks of protons in CR-39 is about or a little lower that 20 keV, above which the proton tracks can be seen clearly and the response curve can be used to distinguish protons from the other ions and determine the energy of the protons. The extension of response curve of protons from traditionally 20 to 100 keV in CR-39 is significant in retrieving information of protons produced in the studies of nuclear physics, plasma physics, ultrahigh intensity laser physics and laser acceleration.

Reduction of background in CR-39 SSNTD using chemical pre-etching methods

Presently, CR-39 Solid State Nuclear Track Detectors (SSNTD) is being used for Fast Neutron Personnel Monitoring in India. Individual detectors are cut manually from CR-39 sheets. Laser-cutting of the sheets will ensure precision and also save on the laborious efforts involved in sheet cutting. It was observed that there is a slight increase in background tracks due to laser-cutting. Studies were carried out on the effect of chemical pre-etching at higher temperatures in properties of CR-39 such as the background, sensitivity and minimum measurable dose. For this purpose a pre-etch step was included in the normal processing of the CR-39 foils in an elevated temperature electrochemical cell (ETECE cell) and the duration for pre-etch step at elevated temperature was optimized.

Loss of carbonate ester bonds along Fe ion tracks in thin CR-39 films

In order to identify the chemical modification along nuclear tracks in CR-39 detectors, we have made a series of FT-IR measurements for thin CR-39 plastic films irradiated by Fe ions. The films were reduced in the thickness by long time chemical etchings down to 5 μ m from as-received CR-39 sheets of 100 μ m thick. It enabled us to obtain unsaturated IR spectra. The samples were exposed to 147 MeV Fe ions at HIMAC in air. Amount of loss of carbonated ester bonds due to the exposure was assessed from the changes in the absorbance of C O and C O C bonds with Fe fluence. The assessed G-value for destroying carbonate ester bonds was found to be about 10 (scission/100 eV).

Distance distribution of bystander effects in alpha-particle irradiated cell populations using a CR-39-based culture dish

Propagation of induced biological effects from irradiated to non-irradiated cells is known to occur in cell cultures exposed to low fluences of charged particles. These bystander effects are currently investigated using microbeam or non-microbeam (broad beams) irradiation techniques. Identification of the targeted and non-targeted bystander cells is critical to our understanding of mechanisms underlying such effects. We developed a novel cell culture dish where the base consists of a thin CR-39 sheet grafted on a thin polyethylene terephthalate (PET) foil. The validity of this device in identifying not only irradiated cells, but also the cellular compartment traversed by the particle track is described. We have optimized track etch parameters that do not interfere with measurement of induced biological endpoints under normal incident irradiation. Thus the culture dishes can be used to determine distance distributions for the propagation of induced biological effects from a hit cell to bystander cells. We describe the computer code developed to determine the distance distributions of propagated biological stress responses in normal human fibroblast cells exposed to very low fluences of alpha particles.

Nuclear Track Detectors for Particle Searches

In this paper we report a search for intermediate mass magnetic monopoles and nuclearites using CR39 and Makrofol Nuclear Track Detectors (NTDs) of the SLIM large area experiment, 440 m 2 exposed at the high altitude laboratory of Chacaltaya (Bolivia) and about 100 m 2 at Koksil, Himalaya (Pakistan). We discuss the new chemical etching and improved analysis of the SLIM CR39 sheets. Preliminary limits are based on 316 m 2 of CR39 NTDs exposed for 3.9 y.

Study of projectile fragmentation in the reaction (158 A GeV) Pb + Pb using CR-39

The fragmentation of Pb ions at 158 A GeV energy produced in the interaction with Pb target has been studied using a CR-39 track detector. A stack comprising of 64 detectors was prepared such that a target of 1 cm thickness was sandwiched between the sheets of CR-39. The purpose of this exposure geometry was to calibrate CR-39 with respect to relativistic heavy ions as well as to study the fragmentation of Pb ions at 158 A GeV energy. The exposure was carried out at the SPS beam facility of CERN at normal incidence with a fluence of ∼ 1500 ion / cm 2 . Two detectors from the exposed stack have been selected for this study: one before and the other after the target material. After etching, the detectors were scanned using an optical microscope and the etched track lengths and the diameters of the track openings were measured manually. Considering that the lengths of tracks provide the best charge resolution for Z > 65 , we have measured track lengths for a sufficiently large number of fragments to identify individual charge states for 65 < Z < 83 . The total charge-changing cross section has also been determined.

On indoor radon daughters’ plate-out on material surfaces

In this work, the plate-out of radon daughters on surfaces of different sizes has been studied. Several pieces of CR-39, cut circularly with different diameters, were exposed for approximately 3 months in an indoor environment containing a high concentration of uranium in Pocos de Caldas, Brazil. During the exposition the CR-39 sheets remained fixed in a wire far from any object. After the exposition, the etched alpha tracks were counted and mapped in order to obtain the spatial distribution of tracks on the detector surface. The accomplished experimental results are in agreement with the theoretical and computational conclusions obtained in previous works.

Alpha-particle calibration of CR-39 using a beehive collimator

A device to determine the detection efficiency of CR-39 for alpha particles is presented. A beehive collimator restricted the angle of incidence of alpha particles on a CR-39 sheet, such that the total number of alpha emitters could be determined. This makes it possible to obtain the critical angle of incidence, Θ C , and the maximum angle of incidence resulting in round (diameter ratio < 1.100 ) etch pits, Θ max . In this work, these angles were determined for incidence energies around 7.5 MeV (more specifically 6.1 and 8.8 MeV).

Variation of the track length along the particle trajectory through CR-39 stack sheets

An alpha track was selected through a number of successive CR-39 sheets in a high energy nuclear reaction experiment. The experiment was aimed at identifying particles emitted at an angle of 25° to the beam direction when bombarding a copper disk with relativistic fluorine ions. Most of these particles were identified as protons and alpha particles. The experiment showed that the inlet energy of an alpha particle to be detectable in CR-39 plastic is 53.4 MeV per nucleon. The CR-39 range of such particles is ∼2 cm long. The corresponding range for a proton is ∼1 mm long. The track diameter at positions on the track length can display the damage as a function of the depth in the CR-39 material. In addition, the track length is measured along the particle trajectories in CR-39 sheets for a single track as a function of residual range in the CR-39 material. The restricted energy loss (REL) for alpha tracks in CR-39 is calculated using the Henke–Benton computer program. Comparison between the REL and the damage was available along this track, especially owing to the ability of CR-39 to prevail etched tracks.

Mass Resolution for Iron Isotopes in CR-39 Track Detector

We have verified the capability of a CR-39 track detector for isotope identification using iron beam from the heavy-ion accelerator of HIMAC at NIRS. The same CR-39 stack was independently exposed to 56Fe and 55Fe ions with an energy of 460 MeV/nucleon. Mass resolutions for 56Fe and 55Fe ions were determined to be 0.28±0.12 amu and 0.28±0.11 amu in rms, respectively. A detailed analysis of the sources of the mass dispersion in the present mass identification experiment showed that significant errors were caused in the measurements of the surface position and the thickness of CR-39 sheets. By eliminating these errors as much as possible, the mass resolution is expected to be improved to ∼0.20 amu.

Local administration of anaesthetics with subpectoral epidural catheters in patients who undergo immediate breast reconstruction with implants

To investigate the cause of white defects in a CCD camera on board the MIR Space Station we exposed test samples of CCD to several kinds of ion beams from the SF cyclotron at the INS. We also designed test stacks of CCDs sandwiched between sheets of CR-39 and exposed them to the radiation in the MIR space station.

Tissue inhibitor of metalloproteinases-1 (TIMP-1) and prognosis in primary breast cancer: an EORTC—RBG collaborative validation study including 2984 patients

To investigate the cause of white defects in a CCD camera on board the MIR Space Station we exposed test samples of CCD to several kinds of ion beams from the SF cyclotron at the INS. We also designed test stacks of CCDs sandwiched between sheets of CR-39 and exposed them to the radiation in the MIR space station.

Development of an ion microbeam system for irradiating single plant cell[s

An ion microbeam system for irradiating single plant cells was developed to analyze exact biological effects of ion beams. Tobacco BY-2 protoplasts were used as a model of single plant cells. Protoplasts were cultured in thin agarose medium on a specially designed irradiation-vessel, which has a CR-39 nuclear track detector (a 100-micrometer thick sheet). The colony formation rate of unirradiated protoplasts was 22.7 +/- 6.7% (mean +/- SE of 3 different experiments) after a month of culture. Protoplasts were irradiated with programmed numbers of 18.3 MeV/u carbon ions that had been collimated by a 20-micrometer phi micro-aperture. After the irradiation, the positions within the protoplasts that were hit with ions were accurately determined by etching the CR-39 sheet in 13.4M KOH solution at 27 degrees centigrade for 9 h. The hit rate of the carbon ion microbeam, i.e., the percent of the ion particles that hit the protoplast that they were aimed at, was 56.9 +/- 2.4% (mean +/- SE of 7 different replications).

CR-39 acceptance test and optimisation for fast neutron dosimetry applications.

The ENEA fast neutron dosemeter is based on a planar PADC (poly allyl diglycol carbonate) placed in a polyethylene holder. The CR-39 (registered trademark of PPG Industries Inc.) material, produced by Intercast Europe S.p.A., has been used in the routine of the Individual Monitoring Service (IMS) since 1998. Since then, acceptance tests on average sheet background track density and sheet neutron sensitivity have been made on new batches as a quality control within a quality assurance programme of the IMS of ENEA-Institute for Radiation Protection (IRP). Dosemeters were irradiated with a 241Am-Be source at ENEA-IRP and processed through a chemical etching procedure (pre-etching with 40% KOH water solution 6.25 N and 60% ethyl alcohol at 70 degrees C followed by 12 h of etching in 6.25 N KOH water solution). In this paper we present the analysis of acceptance testing data for more than 30 sheets of CR-39 plastic produced in 1998, 1999 and 2000. Moreover, we compare the performance of sheets of CR-39 of standard composition with that of sheets of CR-39 with the addition of DOP (dioctylphthalate), in different concentrations, on the hasis of average background density, neutron sensitivity and background fluctuation that limit the lower detectable dose. This study demonstrates the need for acceptance tests to assure the quality of the dosimetric performance of these dosemeters, which is considerably dependent on the quality of the CR-39 plastic.

Role of thermophoresis in the deposition of fume particles resulting from the combustion of high inorganic containing fuels with reference to kraft black liquor

To investigate the cause of white defects in a CCD camera on board the MIR Space Station we exposed test samples of CCD to several kinds of ion beams from the SF cyclotron at the INS. We also designed test stacks of CCDs sandwiched between sheets of CR-39 and exposed them to the radiation in the MIR space station.