Track Recorders Research Articles

Non-linear, adaptive array processing for acoustic interference suppression

A method is introduced where blind source separation of acoustical sources is combined with spatial processing to remove non-Gaussian, broadband interferers from space-time displays such as bearing track recorder displays. This differs from most standard techniques such as generalized sidelobe cancellers in that the separation of signals is not done spatially. The algorithm performance is compared to adaptive beamforming techniques such as minimum variance distortionless response beamforming. Simulations and experiments using two acoustic sources were used to verify the performance of the algorithm. Simulations were also used to determine the effectiveness of the algorithm under various signal to interference, signal to noise, and array geometry conditions. A voice activity detection algorithm was used to benchmark the performance of the source isolation.

A Reliable Simple Automatic Micrometric Scanner for Counting the Fission Fragment Tracks

The design, construction and application of a counting system using simple automatic micrometric scanner (AMS) device for fission fragment tracks (FFT) are described in detail. The system is used to detect the etched fission fragment tracks in thin plastic solid state track recorders (SSTRs) (12 m thickness). The track-detection mechanism is based on scanning concentric circles of specimen rather than the usual XY scanning methods. The circumference of the circle can be traversed to within plusmn2 mum and the reproducibility of the rotation is within 0.001deg. The difference in the radii of the concentric circles is preset in the range of 1 to 99999 mum. The system is capable of obtaining reliable results for the track densities up to 2 times 104 tracks/cm2 and normal-incidence irradiations. The counting efficiency of the system is about 97% compared to visual methods employing a microscope equipped with CCD device, gas permeation technique and spark gas chambers for track densities up to the just-mentioned figure.

Removal of non-Gaussian, broadband interferers using blind source separation and spatial processing

A method is introduced where blind source separation of acoustical sources is combined with spatial processing to remove non-Gaussian, broadband interferers from space-time displays such as bearing track recorder (BTR displays). This is quite different from the standard technique of placing nulls in the direction of interferers. The algorithm is implemented and tested against standard adaptive beamforming techniques, such as minimum variance distortionless response beamforming. In order to illustrate the utility of the approach, experiments were carried out in an anechoic chamber using two acoustic sources. The interferer source remained stationary at boresight, while the signal source moved, in steps of two deg, from negative to positive 20 deg. At each step, one second of data was recorded using a 64-element microphone array that had been calibrated at each subband frequency. All 64 channels of the array were sampled simultaneously at a rate of 22,050 Hz. Spatial processing is implemented using a broadband beamformer. The broadband beamforming algorithm first divides the signals into subbands, basebands, resamples, and finally low-passes the subbands, so that they can be processed using standard frequency domain narrowband beamformers.

The process analysis and improvement of the slender and flat shaft of track recorder

A slender and flat shaft is a key part of the track recorder in marine vessels. However, the axial straightness of the shaft often exceeds standard measurements after it is machined. It has also been found that its precision does not last a long time. After thorough analysis of these problems the main reasons that affect machining quality are identified-and a process modification plan is put forward that meets design requirements of the shaft. The production and practice indicate that the precision of the shaft is stable for a long period and the quality of products improved substantially after new measures were employed, securing the e accuracy of the track recording of the marine vessel.

Gamma-induced changes in the activation energy of bulk and track etching in Makrofol-KG plastics track recorder

Etching studies in gamma-irradiated Makrofol-KG polycarbonate track recorder are reported. Gamma doses ranging between 0 and 500 kGy from a Co60 source have been employed for irradiation. The bulk etch rate, V B, the track etch rate, V T, and the sensitivity, S, are determined in the temperature range of 323–353 K using 6.25 N NaOH as an etchant for each gamma dose. Using these etching parameters, the activation energies for bulk and track etching corresponding to each gamma dose are also calculated and are found to decrease with gamma dose.

The optical, chemical and spectral response of gamma-irradiated Lexan polymeric track recorder

As is the case with any class of materials that enjoys widespread use in varied applications, the properties of polymeric materials have been the subject of numerous studies. This is especially true of their response to low-LET radiations. In this work, modifications induced by 60Co γ -rays in the Lexan polycarbonate plastic track detector have been studied by using FTIR and UV–visible spectroscopic techniques; however, the track registration properties have been investigated by using etching techniques. The results are analyzed on the basis of scission and cross-linking.

The etching and structural studies of gamma irradiated induced effects in CR-39 plastic track recorder

In the application of some polymers as track detectors, the attention should be paid to the fact that the track recording properties of these polymers are changed under the influence of certain parameters, such as the electromagnetic radiations and environmental conditions. In this work the etching effects of 60Co gamma irradiated CR-39 polycarbonate have been studied. For deeper study of the structural changes in CR-39, the FTIR and UV–visible spectra have been analyzed. The FTIR spectra shows considerable changes due to the gamma exposure. The contribution of degradation mechanism is discussed.

The effect of infrared radiation on etching characteristics of CR-39 plastic track recorder

The effect of infrared radiation on the etching characteristics of CR-39 plastic track recorder has been studied. CR-39, which is commonly employed in cosmic rays studies is found to be affected by IR radiations. The changes in the bulk etch rate, in the track etch rate and in etching efficiency due to infrared radiation exposure of CR-39 are discussed on the basis of scission and cross linking during infrared exposure.

Validation of a rigorous track classification technique: identifying individual mountain lions

Despite track survey efforts, the inability to identify individuals from survey data impedes accurate density estimates and density indices for large carnivore species. We present a track classification method for mountain lions Puma concolor using discriminant function analysis that improves and validates the method presented in Smallwood and Fitzhugh (1993) (Smallwood, K.S., Fitzhugh, E.L., 1993. A rigorous technique for identifying individual mountain lions Felis concolor by their tracks. Biological Conservation 65, 51–59) and further discussed in Grigione, Burman, Bleich and Pierce, 1999 (Grigione, M.M., Burman, P., Bleich, V.C., Pierce, B.M., 1999. Identifying individual mountain lions Felis concolor by their tracks: refinement of an innovative technique. Biolkogical Conservation 88, 25–32) . Artificial tracks, made from molded casts of the feet of 13 lions, were used to simulate variability from field conditions in a controlled laboratory setting. We tested the effects of multiple track recorders and two soil depths on linear and angular measurements of the entire paw and shape measurements of the heel-pad. We identified six track measurements that correctly matched 96% of track tracings to known individual mountain lions, even with variability from multiple track recorders and soil depths. Model validation, performed on lab and novel field data in which the number of individual mountain lions was unknown, illustrates the efficacy of the method. Following the field-based study by Smallwood and Fitzhugh (1993), this study provides support for the utility of the discriminant analysis method for track data and outlines future application of this method to field data.

The light transmission method of automated track scanning

An empirical method of automated track scanning is described. This new method is based on the measurement of light transmission (LT) through solid state track recorders (SSTR). Fission fragment tracks in mica SSTR are used to demonstrate the utility of this method. Data analysis reveals that the LT method is equivalent to a point sampling method at the approximately 2% (1 σ) uncertainty level of the calibration data. The total (1 σ) uncertainty of the LT method decreases with increasing fission density from approximately 5% at a fission density of 4.0E + 06 fissions/cm 2 down to approximately 2.5% at a fission density of 1.2E + 07 fissions/cm 2. The current stage of development permits only a qualitative comparison of the LT and point sampling methods. Recommendations to refine the LT method are advanced with emphasis on processing procedures for mica SSTR.

98/03334 Analysis and elimination of trace organic compounds in smoke from burning coal: Wang, X.-H. et al. Gaodeng Xueriao Huaxue Xuebao, 1997, 18, (1), 24–28. (In Chinese)

Solid-state track recorder (SSTR) neutron dosimetry has been conducted in the Three-Mile Island Unit 2 (TMI - 2) reactor cavity (i.e., the annular gap between the pressure vessel and the biological shield) for nondestructive assessment of the fuel distribution. Two axial stringers were deployed in the annular gap with 17 SSTR dosimeters located on each stringer. SSTR experimental results reveal that neutron streaming, upward from the bottom of the reactor cavity region, dominates the observed neutron intensity. These absolute thermal neutron flux observations are consistent with the presence of a significant amount of fuel debris lying at the bottom of the reactor vessel. A conservative lower bound estimated from these SSTR data implies that at least 2 tonnes of fuel, which is roughly 4 fuel assemblies, is lying at the bottom of the vessel. The existence of significant neutron streaming also explains the high count rate observed with the source range monitors (SRMs) that are located in the TMI-2 reactor cavity.

Critical requirements for a posteriori track recorder neutron dosimetry at Hiroshima and Nagasaki

International programs have been carried out over the last four decades to quantify the exposure of atom bomb survivors from Hiroshima and Nagasaki. Unfortunately, the quest for accurate gamma-ray and neutron exposure doses of atom bomb survivors has proven illusive. In the most recent of these programs, designated as Dosimetry System 1986 (DS86), a serious and persistent discrepancy has arisen between neutron transport calculations and radiometric (RM) neutron dosimetry for the Hiroshima site, which has been called the DS86 neutron dosimetry enigma. A recently completed in-depth analysis demonstrates that a simple single factor panacea does not exist to explain the DS86 neutron dosimetry enigma. Careful treatment of a number of specific experimental and calculational effects is required before any progress can be achieved. Within this perspective, the applicability of solid state track recorder (SSTR) neutron dosimetry for the Hiroshima and Nagasaki sites is examined as an independent alternative to radiometric (RM) neutron dosimetry. The utility of the SSTR method for the Hiroshima and Nagasaki sites is analyzed in light of: (i) the current status of the DS86 neutron dosimetry enigma; and (ii) SSTR characteristics that are specifically germane to the Hiroshima and Nagasaki sites. On this basis, critical SSTR requirements are identified, recommended ways of meeting these critical requirements are advanced and the domain of applicability of SSTR neutron dosimetry at the Hiroshima site is estimated.

Earthquake prediction studies in Kangra valley using plastic track recorders

Earthquake prediction is based on the precursory phenomena and radon has emerged as a useful precursor in recent years. Radon emanation in soil gas was continuously monitored at sensitive observation sites from August 1989 to December 1991 in Kangra valley of Himachal Pradesh using LR-115 type II plastic track recorder. Eleven earthquake related radon anomalies are recorded simultaneously at both the stations.

Relaxational behavior of CR‐39 polycarbonate used as nuclear track detector

AbstractThe relaxational behavior of CR‐39 (poly allyl diglycol carbonate) nuclear track detectors was determined over a large temperature range (−100 to 125°C) including the glassy, glass transition, and ionic conduction regions by means of dynamic mechanical and dielectrical measurements, differential scanning colorimetry, linear coefficient of expansion, and especially thermally stimulated current methods owing to their high sensitivity and resolving power. This investigation was carried out as a first step aimed, on the one hand, at finding possible correlations between dosimetric performances, polymer morphology, and intrinsic or extrinsic relaxations and, on the other hand, at determining the origin of the inconsistent background and response properties, which are still a serious obstacle to the use of this material as a personnel dosimeter in spite of its high sensitivity and wide response range. Six distinct relaxation regions have been evidenced, most of which being to some extent dependent on the sample investigated and its thermal history. From higher to lower temperatures, these various relaxations have been ascribed to charge carrier migration over macroscopic distances (ρ), glass transition (α), nonequilibrium precursor motions of the glass transition (ά), and local mode motions of the diethylene‐glycol dicarbonate links (β), diethylene glycol segments (γ), and carbonate groups (δ). In addition to these intrinsic relaxations, the as‐received samples are also characterized by small‐scale residual stresses that relax out irreversibly at temperatures lower than the glass transition temperature Tg. The systematic study of the influence exercized by the position of a specimen in a given sheet, and, for a given sample, by annealing, thermal cycling, and physical aging on relaxation properties shows that, besides spatially inhomogeneous internal stresses, cross‐linking density, and cluster morphology, marked structural modifications and nonequilibrium processes can occur by heating the polymer above Tg. These phenomena deserve a great deal of consideration because they could be key points for identifying the sources of the troublesome fluctuations of dosimetric response. Relaxation studies thus appear as useful and sensitive tools for a deeper understanding of the performance of CR‐39 polymer as a track recorder.

Status and perspectives of track research at Guru Nanak Dev University, Amritsar

Looking back on a decade of track research in Amritsar we report on (i) inter calibration of track recorders, (ii) annealing studies in SSNTDs, (iii) single activation energy model, and (iv) Radon field studies in the context of (a) uranium exploration, (b) assessment of its associated pollution, and (c) earthquake prediction. The developed techniques are inexpensive, provide a good basis for promotion of science teaching and research in developing countries, and — with a little foresight and proper planning — enable the generation of reliable scientific data.

Advances in high fluence solid state track recorder neutron dosimetry

Neutron dosimeters based on measurements of neutron-induced fission rates with solid state track recorders (SSTRs) provide a versatile and accurate method for reactor dosimetry applications. The high fluence upper limit of the range of the SSTR neutron dosimetry method is determined by track counting limitations at very high track densities. The recent development of techniques for the preparation and calibration of ultra low-mass fissionable deposits has extended the high-fluence limit to about 5×10 18 neutrons/cm 2 . To date, more than 900 SSTR neutron dosimeters have been exposed in high neutron fluence applications at commercial nuclear power reactors. At the same time, parallel efforts have been carried out to further extend the range of the SSTR neutron dosimetry technique, to improve the precision of the present methods, and to verify the high accuracy of the method through controlled exposures in standard neutron fields. The present status of high fluence SSTR neutron dosimetry techniques as well as recent improvements in the method will be discussed.

The effect of gamma irradiations on etching characteristics of some solid state track recorders

Abstract Solid state nuclear track recorders viz. CR-39 plastic, glass and phlogopite mica pre-exposed to 252Cf fission fragments are irradiated with gamma doses varying from 50 K rad to 50 M rad in order to study the effect of gamma irradiation on etching characteristics of these detectors. It is found that all these detectors are dose rate dependent. CR-39 is found to be more sensitive to gamma rays then any other solid state track recorder.

Reaction rate measurements for nuclear reactor analyses and critically data

Neutron reaction rate measurements with solid state track recorders (SSTR) and radiometric (RM) neutron dosimeters have been conducted at the Pacific Northwest Laboratory (PNL) Critical Mass Laboratory (CML) as part of the U.S. Department of Energy (DOE) and the Power Reactor and Nuclear Fuel Development Corporation of Japan (PNC) Critically Data Development Program. These reaction rate measurements represent benchmark data that can rigorously test the adequacy of neutron transport calculations performed for nuclear reactor analyses as well as for critically safety assessments. In the 220 series of experiments, fast test reactor (FTR) plutonium fuel pins were assembled in a 0.761 cm square lattice array, which was immersed in an organic moderator. In-fuel and in-moderator dosimetry measurements were conducted near axial midplane. To obtain results at a single axial location, corrections were applied for the spatial variation (axial buckling) of the reaction rates. For the in-fuel measurements, dosimeters were placed between fuel pellets thereby creating gaps in the fuel pin column. Consequently, for these in-fuel measurements, the gap-perturbation effect was measured so that reaction rate data could be corrected to zero fuel gap, i.e. the reaction rates in the unperturbed fuel. Experimental uncertainties range from a low of 2–3 percent for U-238 and Th-232 fission rates to a high of 15–16 percent for U-238 capture rates. The uncertainty in the U-238 (n, Σ) moderator results is dominated by the uncertainty in the neutron self-shielding correction factor, which has been estimated to be approximately 15 percent. Uncertainties in U-235, Np-237 and Pu-239 fission rates range from approximately 4 to 7 percent. These latter uncertainties are larger than uncertainties normally achievable in SSTR neutron dosimetry and reflect the fact that the quality of the SSTR electrodeposits prepared for these isotopes was not completely satisfactory. Least-squares spectral analyses of these data were performed with the FERRET-SAND II computer code. These analyses confirm the general consistency of the experimental data and furnish absolute neutron fluxes with assigned uncertainties.

Etching studies of CR-39 plastic track recorder

Abstract The etching studies are carried out in CR-39 plastic track recorder. The bulk etch rate V B , the track etch rate V T , and etching efficiency η, are determined at the temperatures of 65, 70, 75 and 80°C using 6.25N NaOH as the track etchant. The activation energies for bulk and track etching are determined. The new track etchant Ba (OH) 2 . 8H 2 O, proposed earlier in this laboratory for Lexan 1 , is tested for CR-39. The etching parameters measured using this new etchant are compared with NaOH and LiOH.H 2 O etchants. It is found that etching rates are higher with Ba(OH) 2 . 8H 2 O as compared with these etchants.

Pressure vessel surveillance at commercial light water reactors using solid state track recorder neutron dosimetry

Abstract The accumulation of neutron dose by the pressure vessel of a light water reactor results in radiation damage in the form of steel embrittlement. In order to ascertain the safe operating lifetime of the reactor pressure vessel, the neutron dose must be monitored. Solid state track recorder neutron dosimeters have been developed for pressure vessel surveillance dosimetry at commercial power reactors. To date a total of more than 200 neutron dosimeters from seven different power reactor dosimetry exposures have been analyzed, and more than 150 additional dosimeters are currently deployed. The techniques for carrying out these measurements and thier results will be discussed.