- Email: [email protected]
Annealing studies of charged particle tracks in olivine crystals
Nucl. Tracks Radiat. Meas., Vol. I1, Nos 1/2, pp. 55-57, 1986 Int. J. Radiat. AppL Instrum., Part D
0191-278X/86 $3.00+ .00 Pergamon Press Ltd.
Printed in Great Britain
A N N E A L I N G STUDIES OF CHARGED PARTICLE TRACKS IN OLIVINE CRYSTALS J. S. YADAV Tata Institute of Fundamental Research, Bombay 400 005, India V. P. PERELYGINand S. G. STETSENKO Joint Institute for Nuclear Research, Dubna 141980, U.S.S.R. (Received 5 January 1984; in revised form 3 April 1985)
Abstract--The annealing behaviour of 12.4 MeV/N krypton, 8.3 MeV/N xenon and 10 MeV/N uranium ion tracks in olivine crystals has been studied. The suitable conditions for partial annealing to use in our VVH cosmic ray studies have been inferred.
1. I N T R O D U C T I O N THE EXTRA-terrestrial crystals have registered the galactic cosmic ray record in the form of chemically etchable latent tracks (Fleischer et al., 1967). This wealth of irradiated materials may provide a good deal of information about chemical composition and energy spectrum of galactic cosmic rays. These crystals also offer the means for investigating the time dependence of cosmic ray composition. Many studies have so far been reported on galactic cosmic ray composition (Perelygin et al., 1977; Bull and Durrani, 1976; Lal, 1969). The total etchable track length has been used for the identification of charged particle tracks. The development of TINT and TINCLE methods for revealing the volume tracks has accelerated these studies on irradiated minerals (Lal, 1969). A number of attempts to measure the abundance of ultra heavy (UH) cosmic rays have been made by using these mineral crystals (Otgonsuren et al., 1976; Perelygin et al., 1977; Lal, 1969). However, there have been some limitations with this method like, nonavailability of sufficiently large crystals, high background due to VH tracks and also lack of calibration data. Furthermore, the space fading of fossil tracks which are supposed to be responsible for irregular shifting and broadening of discrete peaks in track length spectrum produces another difficulty in track identification (Kapuscik et al., 1966). The only possible way of eliminating this effect is the artificially controlled annealing of fossil tracks in the laboratory. This study of annealing behaviour of olivine crystals is a part of our investigations for abundance of ultra heavy cosmic ray nuclei and to search for tracks due to super heavy elements that have been undertaken at Dubna since 1973. Here, our aim has been to find out suitable annealing conditions to fade up VH tracks completely and to obtain length of W H nuclei tracks under these annealing conditions. This study is an improvement on our previous study of annealing behaviour of olivine crystals (Lhagvasuren, 1980). This time a small stainless steel vessel is used 55
inside the furnace to store the samples. The crystals have been stored in small metallic foil packets. The temperature is continuously measured inside this stainless steel vessel. The temperature is controlled within + I°C. The annealing behaviour of olivine crystals has been studied using various accelerated heavy ions at different temperature. The suitable partial annealing conditions have been inferred and total etchable length of VVH nuclei tracks has been obtained. Our previous results have also been summarized whenever necessary.
2. EXPERIMENTAL PROCEDURES
Large olivine crystals of size > 1 mm are selected from Marjalahti meteorite. These crystals are mounted in epoxy, are grounded and polished. These samples are exposed to 12.4MeV/N krypton and 10 MeV/N uranium ions at angle 30 ° from heavy ion accelerator at Darmstadt, West Germany. The irradiation to 8.3 MeV/N xenon ions is obtained from heavy ion accelerator at Dubna, U.S.S.R. As shown earlier (Lhagvasuren, 1980), that thermal annealing of particle tracks in olivine is irregular at temperature >480°C. Furthermore, the strong fading of tracks in olivine at temperature _>430°C leaves so small number of tracks that scanning of crystals becomes time-consuming and also that Fe tracks are completely annealed out at 350°C. Taking into account these facts we have studied the annealing behaviour of olivine crystals in the temperature range from 350 to 430°C. The irradiated crystals are annealed for different time at each temperature. Precautions have been taken to minimize the effect of crystallographic axes on track development during these annealing studies. For this, the single exposed crystal is broken to several pieces. These broken pieces are studied for different annealing time at single annealing temperature. This procedure is adopted at all annealing temperatures.
56
J . S . Y A D A V et al. 70T l
IN OLIVINE CRYSTALS
IN OLIVINE CRYSTALS
Estimated total etchoble track
70
~ so
length for Xe ion ~ 170 ~tm for no annealing.
60 50
>~52).1m)
~ 8"3 MeV/N Xe ions o 12./,MeV/N Kr ions
Ann. temp. 20
x~'"-------.o_
-o--- 3S0"C 30
<
~ 0 ~ 0
30
~00"C 6'0 90 ,20 150 ld0 ANNEALING TIME (hr$) =3>
380"C
~
Ann.temp. Xe
20 <~ (1:
(~i,30*C
Kr
(=) 3110"C
2;0
FiG. 1. Variation of total etchable track length with annealing time for annealing temperature 350, 380 and 400°C for 12.4 MeV/N krypton ion tracks in olivine crystal. The olivine crystals are etched in W O 4 solution, a modified form of W N solution of Krishnaswami et al. (1971) for about 24 h. The solution is modified simply by adding four times oxalic acid. This results in a decrease of cone angle. A laser beam is used to reveal the tracks inside the crystals. The laser beam produces etchable latent damages which can be used as artificial channels to reveal the tracks in volume (the tracks which are not etchable at crystal surface). The laser etched tracks are fine holes with diameter of ~ 50 g m and of depth up to 300 # m in crystals. The more important aspect of laser tracks is that each hole is accompanied by a number of fine cracks, and hence this method is more efficient than TINT or T I N C L E method for revealing tracks inside crystals (Yadav, 1982). All the exposed crystals are etched simultaneously.
3. RESULTS AND DISCUSSION The krypton ions of energy 12.4 MeV produce volume tracks in olivine crystals (these tracks are not ctchable from surface). Laser tracks and cracks are produced to reveal Kr ion tracks in volume of crystals. Annealing of 12.4MeV/N krypton ion tracks in olivine has been shown in Figl 1. The tracks are shortened down by a factor of 3 for annealing at temperature 350°C. The annealing at temperature 380°C produces shortening of the tracks by a factor of 4. However, the tracks are completely annealed out in a very short period at temperature 400°C. We have used the Xe beam of energy 8.3 MeV/N to study their track annealing behaviour. This energy of Xe ions is not sufficient to produce volume tracks. So the tracks are surface tracks. However, annealing of these tracks at 430°C for annealing time > 10 h reduces them to volume tracks. Therefore, we have obtained total etchable track length for annealing times more than 10 h at 430°C.
0
20 /,0 60 80 100 ANNEALING TIME (hrs) =:O.
t20
1/,0
FIG. 2. Variation of total etchable track length with annealing time for 8.3 MeV/N Xe ion tracks at temperature 430°C and for 12.4 MeV/N Kr ion tracks at temperature 380°C.
The annealing study of 8.3 MeV/N xenon tracks in olivine has shown that the tracks are annealed to 26 + 2.5 # m track length at temperature 430°C in 32 h (Fig. 2). The annealing behaviour of uranium ion tracks in olivine crystals has been studied at 380°C and 430°C. The 10 MeV/N uranium ions produce surface tracks and remain surface tracks for all annealing time at these temperatures. The annealing behaviour of uranium tracks has been shown in Fig. 3. The tracks are shortened down by only 1 0 # m and there is no marked difference in annealing behaviour at temperature 380°C and 430°C. This is because the low energy side of the t r a c k (which represents highly damaged region) is more stable against thermal annealing than high energy side of the tracks (which represents low damaged region). The low damaged region of tracks is absent in case of 10MeV/N uranium ions.
IN OLIVINE CRYSTALS
7O 10 MeV/N Uranium ion $ur face tracks. Ann.temp. 3aO*C (e)
so
/* 30*C (b)
20
0
20
40 60 ~,0 100 120 ANNEALING TIME (hrs) ¢:~
1/.0
150
180
FIG. 3. Variation of total etchable track length with annealing time for annealing temperature 380°C and 430°C for I0 MeV/N uranium ion tracks in olivine crystals.
C H A R G E D PARTICLE TRACKS Annealing at 430°C for 32 h reduces Xe tracks to length (26 + 2.5) #m. Thus all the tracks due to nuclei of charge ~<50 (tentative value) are completely annealed out under these annealing conditions.* These annealing conditions leave very small number of tracks (sometime even not a single track in a crystal) and makes the scanning of crystals very tedious. The annealing at 380°C for 72 h reduces the Kr ion tracks to length (15 + 2.5)#m. Thus all the tracks due to nuclei of charge ~<34 (tentative value) are completely annealed out. These annealing conditions seem to be moderate and optimum for VVH track studies. We have chosen 72 h annealing time as annealing curve is flat for large annealing time. We cannot obtain total etchable track length of Xe ions for these annealing conditions as tracks of Xe ions of energy 8.3 MeV/N are still surface tracks. The track length of heavier nuclei in olivine are estimated on the basis of Katz and Kobetich model of track formation and, from available track length data (Katz and Kobstich, 1968; Yadav, 1982). The estimated track lengths of Xe and U tracks are found to be 170/tm and 500#m respectively. Our estimation shows that crystals of size /> 1 mm are well suitably for VVH track studies under above mentioned annealing conditions. Acknowledgements--Authors are grateful to academician
G. N. Flerov for his interest in this work. One of us (J. S. Yadav) thanks JINR authorities for their hospitality at this Institute during this work.
57 REFERENCES
Bull R. K. and Durrani S. A. (1976) Cosmic ray tracks in the Shalka Meteorite. Earth Planet. Sci. Left. 32, 36-39. Fleischer R. L., Price P. B., Walker R. M. and Maurette M. (1967) Origins of fossil charged particle tracks in meteorites. J. Geophys. Res. 72, 331-363. Kapuscik A., Perelygin V. P., Tretiskova S. P. and Shaduva N. H. (1966) Fading of the fossil tracks. Proc. 6th Int. Conf. on Corpuscular Phot. Florence CEP, Rome, 458. Katz R. and Kobetich E. J. (1968) Formation of etchable tracks in dielectrics. Phys. Rev. 170, 401-405. Krishnaswami S., Lal D., Prabhu N. and Tamhane A. S. (1971) Olivines: revelation of tracks of charged partides. Science 174, 287-291. Lal D. (1969) Recent advances in the study of fossil tracks in meteorites due to heavy nuclei of cosmic radiation. Space Sci. 9, 623-650. Lhagvasuren D., Otgonsuren O., Perelygin V. P., Stetsenko S. G., Jakupi B., Pellas P. and Ferron C. (1980) A technique for partial annealing of tracks in olivine to determine the relative abundances of galactic cosmic rays. Proc. 10th Int. Conf. on SSNTDs (Suppl. 2, NucL Tracks) pp. 997-1002. Otgonsuren O., Pellas P., Perelygin V. P., Stetsenko S. G., Goavrilova N. N. and Feini C. (1976) Abundances of Z > 52 nuclei in galactic cosmic rays: long term averages based on studies in pallasites. Astrophys. J. 210, 258-266. Perelygin V. P., Stetsenko S. G., Pellas P., Lhagvasuren D., Otgonsuren O. and Jakupi B. (1977) Long term averaged abundances of W H cosmic ray nuclei from studies of olivine from marjalahti meteorite. Nucl. Track Detection 1, 199-205. Yadav J. S. (1982) Studies of charged particle tracks in SSNTDs, Ph.D. thesis, Kurukshetra University, Kurukshetra, India.
*As tracks of Xe nuclei (atomic number 54) have track length (26 _+2.5)/~m and the volume track length decreases with decreasing atomic number.
0191-278X/86 $3.00+ .00 Pergamon Press Ltd.
Printed in Great Britain
A N N E A L I N G STUDIES OF CHARGED PARTICLE TRACKS IN OLIVINE CRYSTALS J. S. YADAV Tata Institute of Fundamental Research, Bombay 400 005, India V. P. PERELYGINand S. G. STETSENKO Joint Institute for Nuclear Research, Dubna 141980, U.S.S.R. (Received 5 January 1984; in revised form 3 April 1985)
Abstract--The annealing behaviour of 12.4 MeV/N krypton, 8.3 MeV/N xenon and 10 MeV/N uranium ion tracks in olivine crystals has been studied. The suitable conditions for partial annealing to use in our VVH cosmic ray studies have been inferred.
1. I N T R O D U C T I O N THE EXTRA-terrestrial crystals have registered the galactic cosmic ray record in the form of chemically etchable latent tracks (Fleischer et al., 1967). This wealth of irradiated materials may provide a good deal of information about chemical composition and energy spectrum of galactic cosmic rays. These crystals also offer the means for investigating the time dependence of cosmic ray composition. Many studies have so far been reported on galactic cosmic ray composition (Perelygin et al., 1977; Bull and Durrani, 1976; Lal, 1969). The total etchable track length has been used for the identification of charged particle tracks. The development of TINT and TINCLE methods for revealing the volume tracks has accelerated these studies on irradiated minerals (Lal, 1969). A number of attempts to measure the abundance of ultra heavy (UH) cosmic rays have been made by using these mineral crystals (Otgonsuren et al., 1976; Perelygin et al., 1977; Lal, 1969). However, there have been some limitations with this method like, nonavailability of sufficiently large crystals, high background due to VH tracks and also lack of calibration data. Furthermore, the space fading of fossil tracks which are supposed to be responsible for irregular shifting and broadening of discrete peaks in track length spectrum produces another difficulty in track identification (Kapuscik et al., 1966). The only possible way of eliminating this effect is the artificially controlled annealing of fossil tracks in the laboratory. This study of annealing behaviour of olivine crystals is a part of our investigations for abundance of ultra heavy cosmic ray nuclei and to search for tracks due to super heavy elements that have been undertaken at Dubna since 1973. Here, our aim has been to find out suitable annealing conditions to fade up VH tracks completely and to obtain length of W H nuclei tracks under these annealing conditions. This study is an improvement on our previous study of annealing behaviour of olivine crystals (Lhagvasuren, 1980). This time a small stainless steel vessel is used 55
inside the furnace to store the samples. The crystals have been stored in small metallic foil packets. The temperature is continuously measured inside this stainless steel vessel. The temperature is controlled within + I°C. The annealing behaviour of olivine crystals has been studied using various accelerated heavy ions at different temperature. The suitable partial annealing conditions have been inferred and total etchable length of VVH nuclei tracks has been obtained. Our previous results have also been summarized whenever necessary.
2. EXPERIMENTAL PROCEDURES
Large olivine crystals of size > 1 mm are selected from Marjalahti meteorite. These crystals are mounted in epoxy, are grounded and polished. These samples are exposed to 12.4MeV/N krypton and 10 MeV/N uranium ions at angle 30 ° from heavy ion accelerator at Darmstadt, West Germany. The irradiation to 8.3 MeV/N xenon ions is obtained from heavy ion accelerator at Dubna, U.S.S.R. As shown earlier (Lhagvasuren, 1980), that thermal annealing of particle tracks in olivine is irregular at temperature >480°C. Furthermore, the strong fading of tracks in olivine at temperature _>430°C leaves so small number of tracks that scanning of crystals becomes time-consuming and also that Fe tracks are completely annealed out at 350°C. Taking into account these facts we have studied the annealing behaviour of olivine crystals in the temperature range from 350 to 430°C. The irradiated crystals are annealed for different time at each temperature. Precautions have been taken to minimize the effect of crystallographic axes on track development during these annealing studies. For this, the single exposed crystal is broken to several pieces. These broken pieces are studied for different annealing time at single annealing temperature. This procedure is adopted at all annealing temperatures.
56
J . S . Y A D A V et al. 70T l
IN OLIVINE CRYSTALS
IN OLIVINE CRYSTALS
Estimated total etchoble track
70
~ so
length for Xe ion ~ 170 ~tm for no annealing.
60 50
>~52).1m)
~ 8"3 MeV/N Xe ions o 12./,MeV/N Kr ions
Ann. temp. 20
x~'"-------.o_
-o--- 3S0"C 30
<
~ 0 ~ 0
30
~00"C 6'0 90 ,20 150 ld0 ANNEALING TIME (hr$) =3>
380"C
~
Ann.temp. Xe
20 <~ (1:
(~i,30*C
Kr
(=) 3110"C
2;0
FiG. 1. Variation of total etchable track length with annealing time for annealing temperature 350, 380 and 400°C for 12.4 MeV/N krypton ion tracks in olivine crystal. The olivine crystals are etched in W O 4 solution, a modified form of W N solution of Krishnaswami et al. (1971) for about 24 h. The solution is modified simply by adding four times oxalic acid. This results in a decrease of cone angle. A laser beam is used to reveal the tracks inside the crystals. The laser beam produces etchable latent damages which can be used as artificial channels to reveal the tracks in volume (the tracks which are not etchable at crystal surface). The laser etched tracks are fine holes with diameter of ~ 50 g m and of depth up to 300 # m in crystals. The more important aspect of laser tracks is that each hole is accompanied by a number of fine cracks, and hence this method is more efficient than TINT or T I N C L E method for revealing tracks inside crystals (Yadav, 1982). All the exposed crystals are etched simultaneously.
3. RESULTS AND DISCUSSION The krypton ions of energy 12.4 MeV produce volume tracks in olivine crystals (these tracks are not ctchable from surface). Laser tracks and cracks are produced to reveal Kr ion tracks in volume of crystals. Annealing of 12.4MeV/N krypton ion tracks in olivine has been shown in Figl 1. The tracks are shortened down by a factor of 3 for annealing at temperature 350°C. The annealing at temperature 380°C produces shortening of the tracks by a factor of 4. However, the tracks are completely annealed out in a very short period at temperature 400°C. We have used the Xe beam of energy 8.3 MeV/N to study their track annealing behaviour. This energy of Xe ions is not sufficient to produce volume tracks. So the tracks are surface tracks. However, annealing of these tracks at 430°C for annealing time > 10 h reduces them to volume tracks. Therefore, we have obtained total etchable track length for annealing times more than 10 h at 430°C.
0
20 /,0 60 80 100 ANNEALING TIME (hrs) =:O.
t20
1/,0
FIG. 2. Variation of total etchable track length with annealing time for 8.3 MeV/N Xe ion tracks at temperature 430°C and for 12.4 MeV/N Kr ion tracks at temperature 380°C.
The annealing study of 8.3 MeV/N xenon tracks in olivine has shown that the tracks are annealed to 26 + 2.5 # m track length at temperature 430°C in 32 h (Fig. 2). The annealing behaviour of uranium ion tracks in olivine crystals has been studied at 380°C and 430°C. The 10 MeV/N uranium ions produce surface tracks and remain surface tracks for all annealing time at these temperatures. The annealing behaviour of uranium tracks has been shown in Fig. 3. The tracks are shortened down by only 1 0 # m and there is no marked difference in annealing behaviour at temperature 380°C and 430°C. This is because the low energy side of the t r a c k (which represents highly damaged region) is more stable against thermal annealing than high energy side of the tracks (which represents low damaged region). The low damaged region of tracks is absent in case of 10MeV/N uranium ions.
IN OLIVINE CRYSTALS
7O 10 MeV/N Uranium ion $ur face tracks. Ann.temp. 3aO*C (e)
so
/* 30*C (b)
20
0
20
40 60 ~,0 100 120 ANNEALING TIME (hrs) ¢:~
1/.0
150
180
FIG. 3. Variation of total etchable track length with annealing time for annealing temperature 380°C and 430°C for I0 MeV/N uranium ion tracks in olivine crystals.
C H A R G E D PARTICLE TRACKS Annealing at 430°C for 32 h reduces Xe tracks to length (26 + 2.5) #m. Thus all the tracks due to nuclei of charge ~<50 (tentative value) are completely annealed out under these annealing conditions.* These annealing conditions leave very small number of tracks (sometime even not a single track in a crystal) and makes the scanning of crystals very tedious. The annealing at 380°C for 72 h reduces the Kr ion tracks to length (15 + 2.5)#m. Thus all the tracks due to nuclei of charge ~<34 (tentative value) are completely annealed out. These annealing conditions seem to be moderate and optimum for VVH track studies. We have chosen 72 h annealing time as annealing curve is flat for large annealing time. We cannot obtain total etchable track length of Xe ions for these annealing conditions as tracks of Xe ions of energy 8.3 MeV/N are still surface tracks. The track length of heavier nuclei in olivine are estimated on the basis of Katz and Kobetich model of track formation and, from available track length data (Katz and Kobstich, 1968; Yadav, 1982). The estimated track lengths of Xe and U tracks are found to be 170/tm and 500#m respectively. Our estimation shows that crystals of size /> 1 mm are well suitably for VVH track studies under above mentioned annealing conditions. Acknowledgements--Authors are grateful to academician
G. N. Flerov for his interest in this work. One of us (J. S. Yadav) thanks JINR authorities for their hospitality at this Institute during this work.
57 REFERENCES
Bull R. K. and Durrani S. A. (1976) Cosmic ray tracks in the Shalka Meteorite. Earth Planet. Sci. Left. 32, 36-39. Fleischer R. L., Price P. B., Walker R. M. and Maurette M. (1967) Origins of fossil charged particle tracks in meteorites. J. Geophys. Res. 72, 331-363. Kapuscik A., Perelygin V. P., Tretiskova S. P. and Shaduva N. H. (1966) Fading of the fossil tracks. Proc. 6th Int. Conf. on Corpuscular Phot. Florence CEP, Rome, 458. Katz R. and Kobetich E. J. (1968) Formation of etchable tracks in dielectrics. Phys. Rev. 170, 401-405. Krishnaswami S., Lal D., Prabhu N. and Tamhane A. S. (1971) Olivines: revelation of tracks of charged partides. Science 174, 287-291. Lal D. (1969) Recent advances in the study of fossil tracks in meteorites due to heavy nuclei of cosmic radiation. Space Sci. 9, 623-650. Lhagvasuren D., Otgonsuren O., Perelygin V. P., Stetsenko S. G., Jakupi B., Pellas P. and Ferron C. (1980) A technique for partial annealing of tracks in olivine to determine the relative abundances of galactic cosmic rays. Proc. 10th Int. Conf. on SSNTDs (Suppl. 2, NucL Tracks) pp. 997-1002. Otgonsuren O., Pellas P., Perelygin V. P., Stetsenko S. G., Goavrilova N. N. and Feini C. (1976) Abundances of Z > 52 nuclei in galactic cosmic rays: long term averages based on studies in pallasites. Astrophys. J. 210, 258-266. Perelygin V. P., Stetsenko S. G., Pellas P., Lhagvasuren D., Otgonsuren O. and Jakupi B. (1977) Long term averaged abundances of W H cosmic ray nuclei from studies of olivine from marjalahti meteorite. Nucl. Track Detection 1, 199-205. Yadav J. S. (1982) Studies of charged particle tracks in SSNTDs, Ph.D. thesis, Kurukshetra University, Kurukshetra, India.
*As tracks of Xe nuclei (atomic number 54) have track length (26 _+2.5)/~m and the volume track length decreases with decreasing atomic number.