Track Registration Sensitivity Research Articles

Application of polyimide films as a nuclear track detector (1): A systematic study of track registration sensitivity

This paper reports the variation of track registration sensitivity as a function of the stopping power of heavy ions in UPILEX-S® films, which is known as the most radiation tolerant polyimide (PI). The detection thresholds in the stopping power for etch pit formation are determined as 4,000, 4,100, 4,800, and 5600 keV/μm for 40Ar, 84Kr, 132Xe and 238U ions, respectively. Furthermore, we investigate the latent track structure in two kinds of PI films (UPILEX-S® and Kapton) by means of FT-IR spectroscopy. At the similar stopping power value, the radiation chemical yields (G value) for heavier ions are lower than those of lighter ions. This is due to the difference of the radial dose distribution for low and high velocity ions.

Application of Radial Electron Fluence around ion tracks for the description of track response data of polyethylene terephthalate as a polymeric nuclear track detector

We try to establish a universal description for the response curve (i.e., relation between the track registration sensitivity and a physical parameters) of polyethylene terephthalate (PET) as a polymeric nuclear track detector. To do so, we adopt a newly developed physical concept Radial Electron Fluence around Ion Tracks (REFIT) using a Monte Carlo simulation in Geant4-DNA, which has been defined as the number of secondary electrons passing through a cylindrical surface that is co-axial to the ion path. We find 11% disagreement for the description of the detection thresholds, from which etch pits start their evolutions when the value of REFIT at a radius of 4.0 nm is used. However, compared to other physical parameters, the REFIT offers improved parameters for the detection thresholds of PET, such as the stopping power, Zeff/β and RELω0=1000 eV. Finally, we discuss future issues affecting implementation of REFIT.

An update of radial dose distribution theory for the detection threshold of Kapton as a nuclear track detector irradiated with 345 MeV/u U and other heavy ions

We aim to determine the detection threshold of Kapton as an Etched Track Detector irradiated with 345 MeV/u U ion, as well as other several heavy ions of Al, Si, Ar, Kr and Xe. The heavier ions are found to have higher detection threshold in the stopping power. At the same stopping power, the track registration sensitivity decreases with increasing the nuclear charge of ions. U ion has the lowest sensitivity as S = 0.04 at the detection threshold of 3400 keV/μm. We have updated the conventional radial dose distribution theory using a relatively new experimentally supported formula for the effective charge up to U ion. The local doses at a track radius of 0.8 nm, which is half of the length of a repeat unit of Kapton, is useful to understand the relation between the sensitivity of heavy ions and the stopping power at each detection threshold.

Evolution of etched nuclear track profiles of alpha particles in CR-39 by atomic force microscopy

Abstract A series of atomic force microscopy (AFM) images of etched nuclear tracks has been obtained and used to calculate the nuclear track registration sensitivity parameter V(x) = Vt(x)/Vb. Due to the AFM limitations the samples were irradiated normally to the surface, and with energies attenuated in order to include the Bragg peak region in the AFM piezo-scanner z movement range. The simulation of the track profile evolution was then obtained. The different stages of etched nuclear track profiles were rendered.

Control of the detection threshold of CR-39 PNTD for measuring ultra heavy nuclei in galactic cosmic rays

It is necessary to develop a track detector with higher detection threshold and high charge resolution for ultra heavy cosmic ray observation. The track registration sensitivity in CR-39 track detector etched by PEW (Potassium–Ethanol–Water) solution was verified using heavy ion beams at the HIMAC accelerator. It was found that PEW solution makes effectively to desensitize the track registration sensitivity in CR-39 detector. Its detection threshold of Z ∗/β is successfully raised to be Z ∗/β = 39 by using PEW solution with the concentration of ethanol of 45 wt%. However this produces a “fuzzy track”. A two-step process of etching involving a post-etch with 7 mol/ l sodium hydroxide solution produced very clear track edges and remarkably improves the charge resolution for heavy ions.

Characteristics of the copolymerized CR-39/DAP track detector for the observation of ultra heavy nuclei in galactic cosmic rays

A new copolymer of CR-39 and DAP resin was developed for the selective detection of ultra heavy nuclei in galactic cosmic rays. The track registration sensitivity for heavy ions with various Z ∗/ β was verified for copolymers mixing CR-39 (BARYOTRAK) with various concentrations of DAP using heavy ion beams at the HIMAC accelerator. In order to realize sufficient polymerization of CR-39/DAP copolymer, the optimum fabricating method was also verified by modifying the concentration of the initiator and temperature–time curing cycle for the copolymerization. CR-39 (BARYOTRAK) used for the base material of copolymerization has many advantages: 1) high uniformity of detector response, 2) extremely clear surface condition after etching, and 3) excellent charge and mass resolutions for heavy ions. The surface condition of the copolymer after etching is remarkably improved by using the BARYOTRAK monomer and its track registration sensitivity is controllable by changing the DAP concentration. However the detection threshold of the CR-39 (BARYOTRAK)/DAP copolymer is not yet satisfactory.

Temperature and pressure conditions for the appropriate performance of charge and mass resolutions in balloon-borne CR-39 track detector for the heavy cosmic rays

We experimentally determined the suitable conditions of temperature and air pressure for measuring charge and mass compositions of heavy cosmic rays using CR-39 track detectors during long-duration, high-altitude balloon flights. The experiments were carried out utilizing Fe ion beams from Heavy Ion Medical Accelerator (HIMAC). Changes in the track registration sensitivity with temperature were studied at temperatures between 213 and 293 K. The charge and mass shifts around Fe ions are possibly 0.11 cu (charge unit) and 0.47 amu (atomic mass unit) at the temperature deviation between 227 and 243 K at balloon altitude. Decrease in track registration sensitivity as air pressure decreases has been observed between 13 Pa and 27 kPa. The charge and mass shifts around Fe ions are inferred to be 0.02 cu and 0.09 amu, respectively, when pressure varies between 20 and 27 kPa. During balloon flight, air pressure drops below this; therefore, care must be taken to keep the temperature and air pressure of CR-39 detectors within acceptable limits.

Track detector of CR-39-DAP-copolymer with variable threshold to detect trans-iron nuclei in galactic cosmic rays

Observation of trans-iron nuclei in galactic cosmic rays ( Z ⩾ 30 ) requires a high performance cosmic ray detector telescope with a large exposure area because of their extremely low fluxes. A solid-state track detector such as CR-39 has the advantage of easy extension of exposure area, but it is necessary to raise the Z / β detection threshold in order to suppress background tracks produced by galactic cosmic rays with Z / β < 30 . The track registration sensitivity and detection threshold for heavy ions with various Z * / β were verified by using track detectors of copolymers of CR-39 and DAP (diallyl phthalate) with various DAP concentration. We found that it is possible to control the Z * / β detection threshold of copolymers by changing DAP concentration. In order to detect heavy ions with Z * / β ⩾ 30 , the optimum DAP concentration was found to be approximately 50%.

Verification of angular dependence for track sensitivity on several types of CR-39

We verified the angular dependence of track registration sensitivity for four types of CR-39 plastic nuclear track detectors using heavy ion beams. These detectors have been launched with several types of luminescence detectors on the Russian segment of the International Space Station (ISS) to intercompare passive radiation dosimeter components from several institutions. CR-39 detectors were irradiated by several kinds of heavy ions with several hundred MeV/n. All the etched tracks were analyzed using a high-speed microscope (HSP-1000) with ellipse fitting software (PitFit). Reduction of sensitivity was observed near the region of the critical angle. Corrections were made using an empirical method based on the known structure of the galactic cosmic ray spectrum.

Optical and electrical properties of gamma irradiated PADC detector

PADC (Polyallyldiglycol carbonate) detector subjected to gamma rays undergoes change in optical and electrical properties. The optical band-gap is determined using Tauc's plot. The band-gap is found to be unchanged up to the dose of 10 3 Gy , and then starts decreasing with increasing dose. The band-gap is lowered from 4.04 eV for the pristine material to 2.46 eV for the highest dose ( 10 6 Gy ). The dielectric constant of the detector is influenced due to the gamma exposure. At lower doses (up to 10 4 Gy ), the detector seems to be not polarised, so no change in dielectric constant is observed. But at the dose of 10 5 Gy , the value is increased slightly while at the highest dose ( 10 6 Gy ), the dielectric constant of the detector is found to be enhanced significantly. The results indicated a decrease in track registration sensitivity with increase in gamma dose.

Effect of proton irradiation through metal foils on PADC

It is a well-known fact that proton irradiation leads to an increase in track registration sensitivity of some polymers. In the present work, the effect of the proton beam irradiation through metal foils (gold and aluminium) on polyallyldiglycol carbonate (PADC) has been studied by track technique. An increase in sensitivity of PADC adjacent to the gold foils has been found which is attributed to the effect of ionisation by the secondary particles emitted from the metal targets due to proton bombardment.

Response of CR-39(DOP) as a relativistic 238U-ion detector

Pershore made CR-39(DOP) solid state nuclear track detector was irradiated at a zenith angle of 30° by 238U-ions of energy 0.927 GeV/n using LBL BEVALAC beam. The exposed plate has been etched in 6.25N NaOH solution at 70°C for one hour. About 1094 cone lengths of the incident U-beam in CR-39(DOP) have been optically measured. The track registration sensitivity ( V T V G ) has been estimated and was found to be (127.7±10.5). The dependence of charge response of CR-39(DOP) detector on restricted energy loss of ultra heavy projectile ions has been studied, to explore the strong departure from Z 2-dependence of the response function.

Proton radiographic characteristics of thin CR-39 detector

Abstract Two parameters, track registration sensitivity and densitometric response in radiography with a low energy ( ∼ 4.5 MeV) proton beam and a stack of thin (100 μm) CR-39 detector foils were investigated. The optimum image quality was obtained at a layer removal thickness of about 1 μm. The image obtained under these conditions is characterized by a high track registration sensitivity (∼60%), high image contrast (the maximum value of the net optical density is ∼ 0.7) and high spatial resolution ( ∼1 μm). The application of the technique in biomedicine is illustrated by proton radiographs of botanical samples.

An investigation to assess which component in the air is concerned with the vacuum effect on plastic track detector sensitivity

Abstract It has recently been found that the storage of plastic track detectors in vacuum prior to irradiation decreases the track registration sensitivity. We tested the main gases composing the air: nitrogen, oxygen and water vapour, to assess whether they could recover the sensitivity of the detector once decreased after it had been stored in a vacuum, adopting as intermediate criterion of detector sensitivity the diameters of etch pits left by normally-incident α-particles. The present results demonstrate that oxygen itself is concerned with the vacuum effect on plastic track detectors.

The effects of irradiation temperature on the registration and annealing properties of nuclear tracks in crystals

Abstract It is now well-established that some plastic nuclear track detectors exhibit a dependence of registration sensitivity on their temperature during charged-particle irradiation. Meteoritic crystals possess a track record of the time-integrated flux of cosmic rays prevailing over the last 10 7 to 10 8 years. Any temperature dependence of the track registration sensitivity in crystals, analogous to that observed in plastic detectors, would clearly be important for the correct interpretation, in terms of charge and energy spectra, of cosmic-ray tracks in meteorites, most of which spend the majority of their cosmic-ray exposure ages at temperatures of ∼100–150 K. We have therefore irradiated several crystals, held at one of a number of different temperatures, with ∼2 MeV/amu 81 Br ions, and then etched them. In general, the minerals tend to have a reduced sensitivity (i.e. lower track-etch velocity) for registration temperatures below room temperature, i.e. the reverse of the trend observed in plastics. The strongest effect of registration temperature is observed in apatite crystals. The initial stages of track etching appear to be particularly sensitive to changes in registration temperature. The track-annealing sensitivity of apatite also appears to be affected by the registration temperature. These temperature dependences have important implications not only for cosmic-ray particle identification but also for fission-track dating and closure temperature studies of meteoritic crystals, which spent early parts of their histories (> 4 Ga ago) at elevated temperatures.

Factors affecting etching properties of CR-39 detector for alpha-particles.

Several factors affecting the track registration performance of CR-39 detectors were studied, adopting as intermediate criterion of detector performance the diameters of etch pits left by normally-incident α-particles. Measures that have been proposed for enhancing detector performance, such as stirring and by ultrasonic vibration applied during etching have proved not to be effective: While these measures increased the etch pit diameters to some extent, the same measures were found to accelerate in keeping also the bulk etching rate, so that the increase observed in the etch pit diameters could not be attributed to enhancement of track registration sensitivity, which is the ultimate criterion of detector performance. Contamination of detector surface with finger grease transferred upon manipulation with bare hand proved not to influence even the intermediate criterion of etch pit diameter. Nor was this criterion influenced by the presence in etchant solution of etched products up to a concentration of 5 g/l. On the other hand, the etch pit diameters were found to be influenced beyond negligible extent by environmental factors such as humidity and temperature even within the range of normal variations occurring in the natural environment, and these factors thus require taking into account in order to ensure consistent measurements with CR-39 detector.

Study of 1020Ne ion tracks in a cellulose nitrate plastic track detector

Cellulose nitrate (Japan) plastic detectors have been irradiated with 10 20Ne ions of energy 8.5 MeV/N and the tracks produced have been observed using the chemical etching technique. The bulk etch rate and track etch rate are determined for different temperatures ranging from 30 to 70°C and hence the activation energies are determined. Experimental resultss show that the track registration sensitivity of CN(J) detector decreases towards higher etching temperatures. The maximum etched track length of 10 20Ne ion in CN(J) is compared with the theoretically computed range.

Calibration of Makrofol Polycarbonate plastic track detector using heavy ions

Abstract In this paper the measurements of the dependence of track etch rate on the specific energy loss, (dE/dx) of different charged particles are presented. In the method, 6C12, 8O16, 10Ne22-ions of energy 5.5 MeV/N and 18Ar40-ions of energy 7.5 MeV/N are used as energetic heavy ions for track formation in Makrofol Polycarbonate track detector. The maximum etched track lengths of these ions are compared with the theoretically computed ranges. The bulk etch rate and track etch rate are determined for different temperatures ranging from 50°C to 90°C. The experimental results show that the track registration sensitivity of Makrofol plastic detector exposed to heavy ions remains constant between 50° and 90°C. The normalized track etch rate, V=Vt/Vb depends only on dE/dx and not on the etching temperature. The variation of normalized track etch rate along the particle trajectory is also shown for different temperatures. Moreover, the experimental data are presented for the influence of different annealing c...