Basu, Basudhara

Bhattacharyya, D P

Csige, I

Pa, Pratibha

Samaipati, K

IACS Institutional Repository

Indian J. Phys. 73B (2), 3 6 5 -368  (1999 )I J P  Ban international journalS tu d ie s  o n  0 .4 5  G e V /n  K r  c o llis io n s  u s in g  so lid  s ta te  n u c le a r  tr a c k  d e te c to r sD P Bhattacharyya*, Basudhara Basu, K SamajpatiD ep artm en t o f  T h eo re tica l P h y sics , Ind ian  A sso c ia tio n  for the C u ltiv a tio n  o f  S c ien ce , Jadavpur, C alcutta  700 032. IndiaPratibha PalD epartm ent o f  Physics, V ictoria C ollege, C a lcu tta-700  009, IndiaandICsige.**Institute o f N uclear R esearch o f the H ungarian A cadem y o f  Sciences,D ebrecen, H ungaryA b s t r a c t  A search has been made on the inelastic collision o f 0  45 G eV /n , Kr ionsin H ungarian  brand  C r39  (M A -N D ) track  d e tec to r  The charge response  o f  the po lym er detector has been studied to investigate the nuclear fragm entation phenom ena The exposed track detectors were etched for 20 hours in 6N NaOH solution at 70‘*C and the etch pits were m easured using a Leit/. optical m icroscope The present results have been com pared with the earlie r short hour etched results. The charge resolu tion  o f the detecto r has been calculated but no rem arkable change is observed from the results as expected from long hour etching o f the track detec to r The charge response o f  the detecto i show s an exponential fall w ith the increase o t e tch ing  tim eK e y w o rd s  0 45 G eV /n Kr, charge response, p ro jec tile  fragm entation  P A C S  N o. , 29 4 0  W k1. IntroductionDetection of cosmic nuclei in high altitude balloon flights and in satellite exposures are very much simplified with the plastic detectors. CR39 is such a solid state nuclear track detector (SSNTD) which is widely used in space exposures, specially because of its high detection sensitivity 11, 2] above Z/j3> 6, and light weight. Moreover, unlike emulsion, it can keep latent tracks for years without fading. For the calibration of these SSNTDs’, laboratory exposures have been done where relativistic ion beams from accelerators are made to fall at differen* E-mail : tpdpb@mahendra.iacs.res.in ** E-mail : csige@atomki.hu© 19991AC?366 D P Bhattacharyya et alincident angles on these detectors. Ahlen etal. [3] have studied response and charge resolution of 1.45 GeV/n ^  Kr using CR39 (DOP) which was manufactured by Pershore Mouldings, England. Later Salamon et al. |4] have also reported the charge resolution of CR39 detector exposed to 1.45A GeV ^  Kr ions and compared them with theoretical results. Earlier, we [5] have studied the projectile fragmentation of 0.45 GeV/n ^  Kr on Hungarian brand CR39 (MA-ND).The charge resolution of this CR39 (MA-ND) detector for charges ranging from Z = 25 to 36 has been compared [5] with the theoretical results after Salamon et al |4]. We have also studied a systematic variation of diameter, cone length and charge resolution with increasing etching time (4,6,8 and 12 hours) from the interaction of 0.45A GeV ^  Kr on CR39 (MA-ND) [6]. In the present paper we have added our observations for 20 hours etching which seems to yield more concluding nature of the etching time dependence of charge resolution and charge response CR39 (MA-ND).2. ExperimentA stack of CR39 (MA-ND) of dimension (5.5 x 2 x 5) cm3 has been exposed to 0.45 GeV /n ™ Kr beam at an angle of 30° from LBL BEVALAC. One of the detector sheets has been etched in 6N NaOH solution at 70°C for 20 hours to enlarge the etch pits for easy and accurate scanning. We have taken the ^  Kr and its projectile fragments only and thus obtained 636 events in the above mentioned area. The estimated bulk etch rate is 1.2 pm/hr. The pits obtained are of elliptical shaped and we have taken the two surface average of the four measurable parameters viz. major axis (a), minor axis (b), surface projection of the cone tip (s) and depth of the cone tipMinor axis in gin —K4F ig u re  1. The cich pit diam eter distribution of 0 .45A GeV projectile Kr fragm ents produced in CR39 (MA-ND) target obtained from the scanned track detector etched for different etching times (a) for 4 h, (b) for 6 h, (c) for 8 h, (d) for 12 h and (e) for 20 h. respectively.Studies on 0.45 GeV/n Kr collisions etc 367(z). The measurements are done under a x 40 objective and a x 15 filar micrometer eyepiece of a Leitz Ortholux Microscope. The least count of this objective-eyepiece combination was0.2pm.3. Result and discussionThe diameter distribution of the optically measured elliptic etch pits those which are obtained after 20 hours of etching are displayed in Figure 1 along with the diameter distribution obtained for previous short hour etching times (t) of 4,6,8 and 12 hours, respectively. It is found from the plot that as etching time increases, the pits of lower Z fragments appear. For t = 20 hours 11 projectile fragments of ^  Kr were found the lowest of which is Mn (Z = 25).The measured minor axis mean diameters of the projectile along with their fragments are plotted as a linear function of Z for etching times t = 4,6, 8, 12 and 20 hrs have been displayed in Figure 2. The quantity “ SD / 5Z’\  is estimated for different etching times and are displayed in the figure. It is found that the abovesaid quantity increases systematically with etching time except for t = 4 hrs. It indicates the fact that the charge resolution decreases with etching time."24 2 5  2 6 2 7 28 2 9 3 0 31 32 33 3 4 3 5 3 6 3 7 3 8 39F ig u re  2. M ean diam eters o f  the K r fragm ents plotted as functions o f  nuclei charges.Table l summarizes the parameters for estimation of charge resolution cr, along with the charge resolution itself. aD is the standard deviation of the gaussian curve fitted to the peak corresponding to the projectile. From Table l , it is seen that no remarkable change in the charge resolution of the detector has been found for this long hour (20 hrs) etched data in comparison to our earlier observations on short hour etched cases. But, this long hour etching added a number of more projectile fragments which were not revealed previously by short hour etching.343 23 0 7 :20 Hr*Etc hint£ £ • 2  437jim /«368 D P Bhattacharyya et alTabic 1. The parametric values of o;,(pm), 8D I8Z  (pm/e) and a / e )  as functions of etching time t (hrs).I 4 6 8 12 20 (h)% 0.34 0.25 0.25 0.34 0.63 (pm)S D7 z1.54 1.32 1 64 1.74 2 44 (pm/e)a z 0.22 0.19 0.15 0.20 0.26 eThe estimated charge response VT/  VQ for different etching time t (hrs) is shown in Figure 3. The charge response is found to fall exponentially with etching time as followsVT/VG =33.8136 exp (-0.0200177t) (I)Figure 3. The estim ated ratio of the track etch rate to bulk etch rate (V t /  V( ) d isplayed as a function o f etching time t (hrs) Full line is the fit to data after relation (1) as described in the  tex t.AcknowledgmentsDr. Basudhara Basu is thankful to the Council of Scientific and Industrial Research, Government of India for financial support.R e f e r e n c e s[1] B G Cartwright. E K Shirk and P B Price N ucl lustrum . M eth. 153 457 (1978)[2] T Hayashi and T Doke N u cl Instrum  M eth. 174 349 (1980)[3] S P Ahlen, T E Coan, J Drach, Shi-lun Guo, P B Price, M H Salatnon, G Tarle and M L Tincknell N ucl T racks a n d  R a d ia tio n  M easu rem en ts  8 571 (1984)[4] M H Salamon, P B Price, M Tincknell and Shi-lun Guo Nucl. lustrum  M eth. B 6 504 (1985)[5] DP Bhattacharyya, B Basu, P Pal, R Rakshit, S Chakrabarty and I Hunyadi Nucl. Instrum  M eth. B61 197 (1991)[6] D P Bhattacharyya, B Basu, P Pal, S C Mukherjee, A K Ganguly and 1 Hunyadi Nucl. Instrum . M eth. B 47  466 (1990)

Studies on 0.45 GeV/n Kr Collisions Using Solid Stalte Nuclear Track Detectors

http://arxiv.iacs.res.in:8080/jspui/bitstream/10821/5570/1/Studies%20on%200.45%20GeV%20n%20Kr%20Collisions_By%20D%20P%20Bhattacharyya.pdf

Studies on 0.45 GeV/n Kr Collisions Using Solid Stalte Nuclear Track Detectors

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