Cylindrical Counter Research Articles

Wear in cold rolling milling rolls: A methodological approach

As a major steel production technology, cold rolling processes have a strong influence on the final quality of rolled products. Traditionally, cold rolling mill rolls present a controlled surface topography that is imprinted onto the sheet during forming and are often coated, particularly using hard chrome deposition. However, wear of cold rolling rolls can affect tribological performance during rolling. Since the nature of tribological phenomena is highly systemic and evolve with sliding time, it is very challenging to reproduce wear in cold rolling rolls using laboratory tests. This work aimed to establish a methodology to reproduce wear mechanisms found in real cold rolling rolls. Due the high cost and dimensions of the rolls, the replication technique was used. Replicas were obtained from four major rolling mill Brazilian companies before and after a normal rolling campaign. The wear mechanisms in the replicas were evaluated using SEM and laser interferometry. To reproduce these mechanisms in laboratory, reciprocating sliding tests were used, which mimic well the change in the direction of friction force that occurs during rolling. The tests used spherical and cylindrical counter bodies under different normal loads and test times to verify which tribological conditions allowed to reproduce the wear mechanisms found in the replicas. These tests indicated the use of reciprocating sliding tests with cylindrical counter bodies in a line contact, where the evolution in wear can be assessed by tests with different test times. This methodology has a great potential to evaluate the tribological performance of different surface modifications used in cold rolling mill rolls.

Measurements and calculations of gas gain in Xe−5% TMA mixture-pressure scaling

In this work we present both experimental and theoretical investigation of gas gains measured in single anode wire cylindrical counters filled with Xe + 5% TMA (trimethylamine) for the mixture pressures between 250 hPa and 1800 hPa. We observed stable operation at all pressures up to the maximum gas gain values as high as 103 (104) at 250 (1800) hPa. The experimental gas gain data have been fitted with the output of Magboltz software to investigate additional ionizations, developing in avalanche formations, due to Penning energy transfers and secondary processes (feedback). Calculations manifest that the choice of TMA as a quench gas have a significant effect on the reachable gas gain. The obtained results are expected to be favourable for micromegas-TPC operating in Xe-TMA mixture.

A study of electric field distribution in Benjamin type proportional counter using finite element method

Tissue equivalent proportional counters (TEPCs) are commonly based on the Benjamin type of concept. Initially the electric field is optimized by pulse height measurement methods and only one optimum solution was established at that time. In this paper, the electric field distribution is analyzed and optimized using a three-dimensional finite element method. The calculations show that the characteristics of the radial electric field distribution of this type of counters can be equated to cylindrical counters using a pair of appropriate field shaping electrode. Furthermore, the paper analyzes the axial electric field distribution and the possibility of achieving a uniform electric field along its anode while reducing the size of Benjamin type proportional counter design down to 1/10 of currently feasible values with respect to the thinnest available anode wire diameters.

Laboratory evaluation of nanoparticle penetration efficiency in a cylindrical counter flow denuder for non-specific removal of trace gases

ABSTRACTThis article presents a cylindrical counter-current flow diffusion denuder with high efficiency penetration of nanoparticles, for non-specific removal of trace gases from an air flow. The denuder was designed to exchange gases in the sample flow by diffusion to the purge flow across a cylindrical microporous glass tube. Laboratory test results indicated that removal efficiencies of gases increased with a lower sample flow rate and a higher sample to purge flow rate ratio. Additionally, the pore size of the microporous glass did not affect gas removal efficiency and particle penetration following optimization of sample and purge flow rate conditions. Significantly high particle penetration was obtained for the counter flow denuder technique (94% penetration for 20 nm of polystyrene latex particle [PSL]) that agreed with theoretical estimation attributed to diffusion loss.Copyright © 2017 American Association for Aerosol Research

Survey and design of an irradiation setup for measuring the amount of heavy water in a sample

An irradiation system, which works based on photodisintegration reaction of deuterium, has been evaluated for determination of heavy water in water samples. This irradiation system was designed by simulation with MCNPX code, considering some gamma point-like sources placed in the center of sample, and then counting the created neutrons by the long cylindrical BF3 counter. For increasing the neutron counting efficiency, an optimization was performed for thickness of various moderators considered between the sample and thermal detector. To investigate the practical effectiveness of the designed system, a model apparatus was built for routine use in measurement of a wide range of heavy water concentrations. It was successfully applied for weight percentages larger than 0.5 % to observe the acceptable detection sensitivity of D2O with an error less than 0.24 %.

Development of a Bonner sphere spectrometer with emphasis on decreasing the contribution of scattering by using a new designed shadow cone

In this study, the Bonner sphere spectrometer (BSS) used for measurement of neutron spectra based a BF3 long counter. The most important problem for this system was a high count of scattered neutrons. This spectrometer was established by designed a new shadow cone with a smaller length and improved attenuation coefficient. Because of shortening the length of the shadow cone, distance of source and center of the sphere was decreased. Furthermore, external part of the thermal detector was covered with a suitable layer to reduce the contribution count of scattering neutrons. Experimental results show that BSS system with BF3 long cylindrical counter, applying the proper developments, can be used in neutron fluence spectrometry.

Measurement of the neutron spectrum by the multi-sphere method using a BF3 counter

The multi-sphere method, a neutron detection technique, has been improved with a BF3 long cylindrical counter as a thermal detector located in the center of seven spheres with a diameter range of 3.5 to 12 inches. Energy response functions of the system have been determined by applying the MCNP4C Monte Carlo code of 10-8 MeV to 18 MeV. A new shadow cone has been designed to account for scattered neutrons. Although the newly designed shadow cone is smaller in length, its attenuation coefficient has been improved. To evaluate the system, the neutron spectrum of a 241AM-Be source has been measured.

Performance of gaseous detectors filled with heavy freon C3F8

The performance of gaseous detectors filled with heavy freon (C3F8) with a uniform or sharply nonuniform internal electric field is described. It is shown that, though the gas is electronegative, the detectors are capable of operating both in the ionization and avalanche modes and, in addition, all ionization electrons may be collected in the ionization mode. The detection efficiency of the cylindrical counters used in the avalanche mode is ∼10%. In the investigations, it has also been shown that the relative amplitude distribution of the cylindrical counter depends on whether the ionization is point or extended.

Study of a solid state microdosemeter based on a monolithic silicon telescope: irradiations with low-energy neutrons and direct comparison with a cylindrical TEPC

A silicon device based on the monolithic silicon telescope technology coupled to a tissue-equivalent converter was proposed and investigated for solid state microdosimetry. The detector is constituted by a ΔE stage about 2 µm in thickness geometrically segmented in a matrix of micrometric diodes and a residual-energy measurement stage E about 500 µm in thickness. Each thin diode has a cylindrical sensitive volume 9 µm in nominal diameter, similar to that of a cylindrical tissue-equivalent proportional counter (TEPC). The silicon device and a cylindrical TEPC were irradiated in the same experimental conditions with quasi-monoenergetic neutrons of energy between 0.64 and 2.3 MeV at the INFN-Legnaro National Laboratories (LNL-INFN, Legnaro, Italy). The aim was to study the capability of the silicon-based system of reproducing microdosimetric spectra similar to those measured by a reference microdosemeter. The TEPC was set in order to simulate a tissue site about 2 μm in diameter. The spectra of the energy imparted to the ▵E stage of the silicon telescope were corrected for tissue-equivalence through an optimized procedure that exploits the information from the residual energy measurement stage E. A geometrical correction based on parametric criteria for shape-equivalence was also applied. The agreement between the dose distributions of lineal energy and the corresponding mean values is satisfactory at each neutron energy considered.

Neutron sensitivity and detection efficiency of 3He and 10BF3 counters

An analytic relationship between the efficiency, sensitivity, and the coefficient of working-isotope utilization is established for gas-filled cylindrical thermal-neutron counters. This dependence is expressed in terms of the ratio of the characteristic length of a counter to its diameter. The characteristic size is introduced as the ratio of the total absorption cross section to the length of the counter. The parameters of basic 3He and 10BF3 counters used in NM-64 neutron monitors are calculated.

An investigation of wideband circular cylindrical sector dielectric resonator antenna with microstripline feed

AbstractThe article proposes a compact microstrip line fed dielectric resonator antenna with half split circular, cylindrical profile which is experimentally investigated. It shows that at optimum parameters, this low profile, small size antenna gives a wideband response similar to that of its full cylindrical counter part with moderate gain but at different frequency. The return loss and radiation pattern of the proposed antenna is measured and studied. The simulated and measured results verify that the proposed antenna offers an impedance bandwidth of 36.7% (from 3.24 to 4.70 GHz) and shows a radiation pattern which is relatively conical in shape with linear polarization. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2861–2865, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24762

A postproportional gas-amplification mode in cylindrical counters

A high-current gas-amplification mode in cylindrical detectors is considered as a time sequence of three amplification modes: a proportional mode, a mode of limited proportionality, and a self-quenched streamer (SQS) mode. The probability of a change from the limited proportionality to the SQS mode depends on the degree of ionization of the primary particle, the used gaseous mixture, and the anode diameter. The proposed gas-amplification mechanism complies with the main experimental results. Examples of promising applications of detectors in SQS modes are considered.

A tissue equivalent proportional counter filled with a mixture of tissue equivalent gas and 3He for neutron monitoring

Tissue equivalent proportional counters (TEPC) allow the measurement of the ambient dose equivalent H(*)(10) in mixed fields. IRSN has been studying the design and the response of a TEPC in terms of neutron H(*)(10). First, a cylindrical counter was filled with propane gas at a low pressure. H(*)(10) measured in monoenergetic neutron fields underestimated the reference (>50%) at low energies (< 500 keV). A small amount of (3)He was then added to the gas in order to increase the response. The underestimation observed decreased but the results (> 40%) were not totally complying with the objectives (< 20%). Finally the choice was made to improve the analysis of the microdosimetric spectra y.d(y) in order to identify the energy of the incident neutrons. The analysis allows a better estimate of H(*)(10). The aim of this article is to describe the TEPC and the effect of these methods of optimisation.

Performance of [formula omitted] filled proportional counters under high gas gain at high working gas pressure

Limited streamer mode has been studied in a single wire cylindrical counters with cathodes diameter 8, 10, 14 mm and anodes diameter 20 and 30 μ m , filled with Ar + 20 % CO 2 mixture. For working gas pressure of 0.3, 0.5 and 0.65 MPa the 90 % transitions from proportional to SLS mode were manifested, while this effect was not observed for lower pressure.

A Monte Carlo design of a neutron dose-equivalent survey meter based on a set of 3He proportional counters

In order to improve the energy dependence of the Rem-meter's response characteristics, a device was studied which uses a spherical moderator and two types of proportional counters, a spherical counter located at the centre of the moderator and six cylindrical counters located close to the moderator surface. The energy and angular dependence of the neutron-energy response of the device in the neutron-energy range of 2.5 × 10 - 8 – 20 MeV was calculated using Monte Carlo simulations. An evaluation method of ambient dose equivalent was investigated.

Active Neutron Dosemeters based on Microdosimetric Principles: Research Studies

Over the past few years, the Institute for Radiation Protection and Nuclear Safety (IRSN) has been studying a personal electronic neutron dosemeter and an ambient electronic neutron dosemeter based on experimental microdosimetric principles using low pressure proportional counters. The results obtained in 2000 and in 2001 with the cylindrical tissue-equivalent proportional counter developed for use in radiation protection and filled with a low pressure tissue-equivalent gas (propane based) are presented here.

Monte Carlo calculations and experimental results of Bonner spheres systems with a new cylindrical Helium-3 proportional counter

The experimental results on neutron energy spectra, integral fluences and equivalent dose measurements performed by means of a Bonner sphere system placed inside the containment building of the Vandellòs II Nuclear Power Plant (Tarragona, Spain) are presented. The equivalent dose results obtained with this system are compared to those measured with different neutron area detectors (Berthold, Dineutron, Harwell). A realistic geometry model of the Bonner sphere system with a new cylindrical counter type “F” (0,5NH1/1KI—Eurisys Mesures) and with a set of eight polyethylene moderating spheres is described in detail. The response function in fluence of this new device, to mono-energetic neutrons from thermal energy to 20 MeV, is calculated by the MCNP-4B code for each moderator sphere. The system has been calibrated at IPSN Cadarache facility for ISO Am–Be calibrated source and thermal neutron field, then the response functions were confirmed by measurements at PTB (Germany) for ISO recommended energies of mono-energetic neutrons and with the CANEL IPSN facility which simulates realistic fields.

A position-sensitive ionization chamber for thermal neutrons

A position-sensitive neutron detector based on /sup 3/He is being developed for a national crystal backscattering spectrometer (CBS) at a pulsed neutron source. It comprises a single gas volume, of constant depth, in the form of an annulus that is also part of a truncated cone. Charge from each event is collected on one or two anode strips, out of a total 336 around the annulus, yielding an angular resolution of about 1/spl deg/. Low-noise signal processing, in the form of a monolithic preamplifier/shaping amplifier connected to each anode strip, provides electronic noise that is small enough to permit detector operation in an ionization mode. In addition, the segmented anodes ensure near complete induced charge collection. This new detector therefore has significant advantages over previous detectors used in CBS instruments, which primarily consisted of arrays of individual /sup 3/He filled cylindrical counters with dead regions and nonuniform detection efficiency. The optimization of gas mixture/pressure, drift field, and shaping time is significant in achieving successful performance in the new detector.

Rate effects in radiation detectors with resistive electrodes

Detectors with highly resistive electrodes, particularly RPCs, have been studied extensively in recent years. Several authors considered the effect of rate on the detector response (efficiency) and a few also associated with the rate, in a rather qualitative manner, the charge per event, i.e., the current. Here, without loss of generality of the results obtained, rate effects are studied with a classical cylindrical counter geometry and different gas mixtures. To a high accuracy, the observed behavior, both for the proportional mode and for the transition to streamers, is quantitatively and accurately interpreted as loss of voltage on the dielectric due to the current generated in the detector, with direct consequences for the local electric field in the avalanche region. Results obtained in the self quenching streamer (SQS) mode fail the previous interpretation and clearly need further research.

Computations to facilitate TEPC calibration with 37Ar

Monte Carlo computations are performed to facilitate the calibration of tissue equivalent proportional counters with 37Ar. As shown earlier, this calibration method is essential for small counters and for multi-element detectors; besides providing the calibration factor it provides also a quantitative assessment of the resolution of the counter. To extend the use of this method to small simulated sites, geometrical effects are studied for spherical and cylindrical counters. As the simulated diameter decreases, the K-capture peak broadens and shifts towards lower energies. Frequency distributions of ionizations produced by 37Ar decay particles are computed, and the most probable numbers of ion pairs due to K-capture events are given for different counter types and for simulated diameters from 10 μm down to 200 nm. The smallest simulated diameter at which counters can be calibrated in terms of the L-capture peak is found to be about 50 nm. By multiplication with the W-value (the average energy required to produce an ion pair), the results are related to the distributions of energy imparted due to 37Ar decays. The results can serve as reference values in the calibration of tissue equivalent proportional counters with 37Ar.