- Email: [email protected]
Calibration of the intercast CR39
&cl.
mcks
&diet. &OS.. Vol 22. Na l-4, pp. W-s%. 1993 EbsviaacisaceLtd PrlmednOn*brlPin. o!Bssmm RR.oo+.a0
CALIBRATION OF THE INTERCAST CR39
VNFN SCWO~C dl Bologna, v. Imglo 46, Bologna Italy, tCNR. lrhtuto TFSRE, v. de’ Cmtagnot 1, Bologna, hly; v. her10 46, Boiognh Italy; #Faculty of Scmce. Uluverp~tyMohammed 1. &Jda, Mm; ~alifomm Instme of Technology, Pasadena CA 91125, U.S.A.
$bpammento dr Fixa,
ABslTucr
We present new calibration results of the CR39 nuclear track detector made in collaboration with the Intemast Europe Co. of Patma Italy. Upper limit on the pmduction of nuclei with fractional charge has also been established. Results are also presented on the determination of the total and partial charge changing fragmentation cross sections of %i14+ ions of 14.5 GeV/nucleon and of 32Sta+ions of 200 GeV/nucleonin Copper targets. KEYWORDS CR39; calibration charge resolution;fractionalcharge; charge changing fragmentationcross section. lNTRODUCTION ‘Ibe main pmpose of this woticwas the calibrationof the CR39 polymer of so-called type ‘L6’,made in collaborarionwiththcIn~~tEuropeCo.ofPanna,ItalyanduscdasuadcetchdcrectorintheMACRO experiment at Gran Sasso. The MACRO track etch detector is of mom than loo0 m*, and the final sixe will be about 1300 m*, with 3 layers of CR39 and 3 layers of Lexan polym (MACRO Coll. 1991).The chemical composhio~ the curing cycle and a former calibrationcurve of the CR39of type L6 are reported in the previous reference. We present here new calibrationresults obtaii using telativistic silicon, sulphur and gold ion beams. Calibrationsof the CR39 with low velocity ions are in progress. Stacks of 13x7 cm* foils of CR39 of different batch production, were exposed to 14.5 GeV/nucleon 28Si14+ions at the AGS accelerator (BNL, June 1990). to 200 GeV/nucleon 3*Sla+ ions at the SPS (CERN, July 1990) and to 11.3 GeVlhucleon 197Au79+ions at the AGS (BNL, May 1992). The relativistic ion density was about 1500 ions/cm*. Each stack contained from 6 up to 12 foils of CR39 upstream and downstream of 14 mm thick Copper target; the CR39 foils were each 1.4 mm thick. We may thus identify the incoming and outgoing particleprojectilesand fragment particles. CALIBRATIONS After exposures the CR39 foils were etched in 6.0 N NaOH water solution at (70.0&0.1)°C(for 45h the ~exposcdtoSiandSbeamsand27hthesta~exposedtoAubeam).The~nrrfaceanasofthtctch pns were measured with a fully automated Elbek image analyzer system @Jell et ol., 1988).The calibrations am based on the measurements of the mean track amas produced by the ion beam particles and by the fragment panicles. Figure 1 shows a distribution of the track amas of sulpbur ions and their fragments using a single surface measurementafter backgroundreduction obmined with a cut on the track central brightmzssvalue and eccentricity.
l
Alao Faculty of Sciam
Univemy Mohammed I. Ou@a,Maroccr,
556
s. CECCHINIt?ral.
Fmm the meastuements of the track amas and of the bulk etching rate VB, the nduced etch rate p3DvT/vB was calculated using the usual formulae (Fleischer et al., 1976).The values of p obtained for each detected ion from silicon, sulphur and gold ion exposures are plotted in Fig. 2 vetsus the Restricted Energy Loss (REL) that was calculatedusing the expmssiongiven by the Panicle Data Gtoup. The new measurements with gold ions do not indicate any change either in sensitivity or threshold compamd to two year old measumments with silicon and sulphur ions.
Fig. 1 : Track surface area distributionof 200 GeV/nucleon S16+ nuclei and their fragmentsmeasuredon a single surface of a CR39 foil located downstmam of the copper target.
7 P5 5 4 3 2 1 lo* lo3 t?EL(MoV*cd/g)
Fig.2 : Experimentalcalibrationdata points of the reduced etch rate p versus REL from Si14+, S1& and Au’~+exposures. The line is the best fit to the experimentaldata. CHARGERESOLUTIONAND SEARCHFOR FRACI’lONALLYCHARGED NUCLEI It hasbeen suggested (De Rujula et al., 1978)thatfragments with fractional charge might be formed in high energy nucleus-nucleus collisions. Upper limits on the production probability of fragments with
557
CALIBRATION OF THE INTERCAST CR39
mctiaul~inthecollisionsof145GeVmucleacSi~JCjinco~andin~9wenestimrrted. FortMspuporrethetFajectoryo~eachsingleEnrgmentnu~~wris t@&t&edbytmckingtheetch arner~vclyfromsurhcetosurfacethroughoutsixfoilsofQ239afferthecopper~QIogt ~nuclerrfnsmeMatiorrsandetcctedasachangeintheareaofthectchpl~Weimroduceda conccrbnanrrrmrllvoristionofthcanrfrwnoncsurfaatotheothcr.ForePch~rmwru#lwas calculated as the average of 7 to 12 individual measurements. AM calibration we obtained tbe charge distrllnttion tiwn in Fig.3. The standard deviation is ag=O.O5efor -7 and 0g=O.O7efor Z=13. The slieht~ofthcchersertsolutionwithincreasingZisduetothtnonlinear~oftheetch_pit amaswlthkmashlgcharge. In Fig. 3 tkn is no indication of nuclei with fractional charge produced in tbe copper target. We measured . 920 fragment tracks with charge 7 ?; Z 5 13. From the number of detected fragments we dctummd the upper limit for the production in Cu of projectile fragments with charges 20/3 up to 4QI3 (iiger f 1/3e),using the relation: F=WCI/(&NF)
(1)
whereNC is the number of fragments with charge differing by more than 0.22e from an integer charge in the above intervals, Np is the number of measured ordinary fragments in the same charge intervals, e is the product of detection and selectionefficienciesof fractionallycharged nudei mlative to ordinarym&i and is estimated to be 98% ; K= 2.3 when NC=0 for 90% C.L.
Them are no candidate events which differ by more than 0.22e from integer charge. The upper limit on the production of fragments in Cu with fractionalcharge at 90% confidence level is F s 2.6~1~. This limit is valid for projectile fragmentspenetratingat least 7 mm of CR39 and 14 mm of Cu. 600 sf, 14.5 GeV/nucleon
6
7
6
9
10 11 CHARGEZ
12
13
14
15
Fig.3:Chargedistributionof
14.5GeV/nucleon Si14+ions and their fragments based on ten surface ama measutwnents for each detected particle. The points in the horixontal axis show the expected positions of the fractional charges. There is no indicationof nuclei with fractionalcharge.
CHARGECHANGINGFRAGMENTATIONCROSS SECTlONS OF %i14+ AND 32Ste+ IN Cu TARGET To dcteminc
the KW and partial charge changing fragmentation cross sections in Cu of 14.5 GcWhdam silicon nudei and of 200 GeV/nudeon sulphur nuclei, we tbetn#uoriesof rhe beam and fragment nuclei through four foil surfaces u tmam and downstmam of the target. We coneued our mcIIunmeNs for the fragmentationin the CRY9 foils. A pmpaga&n fonnula (Bmchtmann er al., 1988a)for the mlation between the distributions of the incoming and outgoing partides on the target a&ces was used. A correction was made for the electnnnagnetic dissociationeffect ( Brechtmann et ul.. 1988b).For the total charge changing fragmentationcross sections we okained :
558
s. CEccHINI et al.
0
0
0
r
0
I
0
0
0
0
Fig.4 : Partial fragmentationcross sections in Cu for silicon ions of 14.5 GeV/nucleon and sulphur ions of 200 GeV/nucleon into various nuclear fragments for AZ ranging from 1 to 9. CONCLUSIONS We have perfoned a new calibration of the INTERCAST CR39 of type L6; there is no indication of aging in the reduced etch rate p for two yeas old CR39. We have placed an upper limit at 9098confrdencc level for the production of nuclei with fractionalcharge at the level of less than 2.6x10-4of the analysed fragments. We have measured the total and partial charge changing fragmentation cross sections of silicon and sulphur in Cu targets. ACKNOWLEDGEMENTS We would like to thank Drs. P.Baiocchi, G.G.Gianiand G.Iori of the lntetcast Company for their active cooperation. We thank Dr. D.Beavisand the staff of the Brookhaven AGS acceleratorfor the silicon and gold exposures, the CERN SPS staff for the sulphur exposure. We thank our technical staff for the help in the analysis of the stacks. REFERENCES
Bmchunann, C., and W.Heinrich (1988a).Measurementsof elemental fragmentationcross section for relativisticheavy ions using CR39 plastic nuclear track detectors. Nucl. Instr. Merh..B2p. 675. Bnchtmann, C.. and W. Heinrich (1988b).Fragmentation cmss section of 3% at 0.7, 1.2 and 200 GeV/nucleon. ZPhys. U ,463. Btechtmann, C., W. Heinrich, and E.V.Benton (1989). Fragmentation cross section of %i at 14.5 GeV/nucleon. Phys. Rev. C 2.2222. De Rujula, A., R.C.Giles and R.L.Jaffe (1978). Unconfined quarks and gluons. Phys. Rev. DJl ,285. Fleischer, R., P.B.Price, and R.M.Walker(1976). Nuclear Trucks in Soli&, California Press, pg.18 MACROCollaboration(1991).lmptovements of the CR39 polymer for the MACROexperiment at the Gran Sasso Laboratory. Nucl.Tracks Rat&at. Meas.,&I, 641. No& A.. 0. Rusch, H. Rocher. J. Dmute and W. Heinrich (1988) . ‘IBe Siegen automatic measurmg system for nuclear track detectors: new development&Nucl. Tracks Radiat. Meas., 15,265. Rice, P.B.. R.Guoxiao. and T.WilJiams(1988). Electromagneticspallation of 6.4-TeV % nuclei. Phys.Rev. Lat. 41 , 2193.
mcks
&diet. &OS.. Vol 22. Na l-4, pp. W-s%. 1993 EbsviaacisaceLtd PrlmednOn*brlPin. o!Bssmm RR.oo+.a0
CALIBRATION OF THE INTERCAST CR39
VNFN SCWO~C dl Bologna, v. Imglo 46, Bologna Italy, tCNR. lrhtuto TFSRE, v. de’ Cmtagnot 1, Bologna, hly; v. her10 46, Boiognh Italy; #Faculty of Scmce. Uluverp~tyMohammed 1. &Jda, Mm; ~alifomm Instme of Technology, Pasadena CA 91125, U.S.A.
$bpammento dr Fixa,
ABslTucr
We present new calibration results of the CR39 nuclear track detector made in collaboration with the Intemast Europe Co. of Patma Italy. Upper limit on the pmduction of nuclei with fractional charge has also been established. Results are also presented on the determination of the total and partial charge changing fragmentation cross sections of %i14+ ions of 14.5 GeV/nucleon and of 32Sta+ions of 200 GeV/nucleonin Copper targets. KEYWORDS CR39; calibration charge resolution;fractionalcharge; charge changing fragmentationcross section. lNTRODUCTION ‘Ibe main pmpose of this woticwas the calibrationof the CR39 polymer of so-called type ‘L6’,made in collaborarionwiththcIn~~tEuropeCo.ofPanna,ItalyanduscdasuadcetchdcrectorintheMACRO experiment at Gran Sasso. The MACRO track etch detector is of mom than loo0 m*, and the final sixe will be about 1300 m*, with 3 layers of CR39 and 3 layers of Lexan polym (MACRO Coll. 1991).The chemical composhio~ the curing cycle and a former calibrationcurve of the CR39of type L6 are reported in the previous reference. We present here new calibrationresults obtaii using telativistic silicon, sulphur and gold ion beams. Calibrationsof the CR39 with low velocity ions are in progress. Stacks of 13x7 cm* foils of CR39 of different batch production, were exposed to 14.5 GeV/nucleon 28Si14+ions at the AGS accelerator (BNL, June 1990). to 200 GeV/nucleon 3*Sla+ ions at the SPS (CERN, July 1990) and to 11.3 GeVlhucleon 197Au79+ions at the AGS (BNL, May 1992). The relativistic ion density was about 1500 ions/cm*. Each stack contained from 6 up to 12 foils of CR39 upstream and downstream of 14 mm thick Copper target; the CR39 foils were each 1.4 mm thick. We may thus identify the incoming and outgoing particleprojectilesand fragment particles. CALIBRATIONS After exposures the CR39 foils were etched in 6.0 N NaOH water solution at (70.0&0.1)°C(for 45h the ~exposcdtoSiandSbeamsand27hthesta~exposedtoAubeam).The~nrrfaceanasofthtctch pns were measured with a fully automated Elbek image analyzer system @Jell et ol., 1988).The calibrations am based on the measurements of the mean track amas produced by the ion beam particles and by the fragment panicles. Figure 1 shows a distribution of the track amas of sulpbur ions and their fragments using a single surface measurementafter backgroundreduction obmined with a cut on the track central brightmzssvalue and eccentricity.
l
Alao Faculty of Sciam
Univemy Mohammed I. Ou@a,Maroccr,
556
s. CECCHINIt?ral.
Fmm the meastuements of the track amas and of the bulk etching rate VB, the nduced etch rate p3DvT/vB was calculated using the usual formulae (Fleischer et al., 1976).The values of p obtained for each detected ion from silicon, sulphur and gold ion exposures are plotted in Fig. 2 vetsus the Restricted Energy Loss (REL) that was calculatedusing the expmssiongiven by the Panicle Data Gtoup. The new measurements with gold ions do not indicate any change either in sensitivity or threshold compamd to two year old measumments with silicon and sulphur ions.
Fig. 1 : Track surface area distributionof 200 GeV/nucleon S16+ nuclei and their fragmentsmeasuredon a single surface of a CR39 foil located downstmam of the copper target.
7 P5 5 4 3 2 1 lo* lo3 t?EL(MoV*cd/g)
Fig.2 : Experimentalcalibrationdata points of the reduced etch rate p versus REL from Si14+, S1& and Au’~+exposures. The line is the best fit to the experimentaldata. CHARGERESOLUTIONAND SEARCHFOR FRACI’lONALLYCHARGED NUCLEI It hasbeen suggested (De Rujula et al., 1978)thatfragments with fractional charge might be formed in high energy nucleus-nucleus collisions. Upper limits on the production probability of fragments with
557
CALIBRATION OF THE INTERCAST CR39
mctiaul~inthecollisionsof145GeVmucleacSi~JCjinco~andin~9wenestimrrted. FortMspuporrethetFajectoryo~eachsingleEnrgmentnu~~wris t@&t&edbytmckingtheetch arner~vclyfromsurhcetosurfacethroughoutsixfoilsofQ239afferthecopper~QIogt ~nuclerrfnsmeMatiorrsandetcctedasachangeintheareaofthectchpl~Weimroduceda conccrbnanrrrmrllvoristionofthcanrfrwnoncsurfaatotheothcr.ForePch~rmwru#lwas calculated as the average of 7 to 12 individual measurements. AM calibration we obtained tbe charge distrllnttion tiwn in Fig.3. The standard deviation is ag=O.O5efor -7 and 0g=O.O7efor Z=13. The slieht~ofthcchersertsolutionwithincreasingZisduetothtnonlinear~oftheetch_pit amaswlthkmashlgcharge. In Fig. 3 tkn is no indication of nuclei with fractional charge produced in tbe copper target. We measured . 920 fragment tracks with charge 7 ?; Z 5 13. From the number of detected fragments we dctummd the upper limit for the production in Cu of projectile fragments with charges 20/3 up to 4QI3 (iiger f 1/3e),using the relation: F=WCI/(&NF)
(1)
whereNC is the number of fragments with charge differing by more than 0.22e from an integer charge in the above intervals, Np is the number of measured ordinary fragments in the same charge intervals, e is the product of detection and selectionefficienciesof fractionallycharged nudei mlative to ordinarym&i and is estimated to be 98% ; K= 2.3 when NC=0 for 90% C.L.
Them are no candidate events which differ by more than 0.22e from integer charge. The upper limit on the production of fragments in Cu with fractionalcharge at 90% confidence level is F s 2.6~1~. This limit is valid for projectile fragmentspenetratingat least 7 mm of CR39 and 14 mm of Cu. 600 sf, 14.5 GeV/nucleon
6
7
6
9
10 11 CHARGEZ
12
13
14
15
Fig.3:Chargedistributionof
14.5GeV/nucleon Si14+ions and their fragments based on ten surface ama measutwnents for each detected particle. The points in the horixontal axis show the expected positions of the fractional charges. There is no indicationof nuclei with fractionalcharge.
CHARGECHANGINGFRAGMENTATIONCROSS SECTlONS OF %i14+ AND 32Ste+ IN Cu TARGET To dcteminc
the KW and partial charge changing fragmentation cross sections in Cu of 14.5 GcWhdam silicon nudei and of 200 GeV/nudeon sulphur nuclei, we tbetn#uoriesof rhe beam and fragment nuclei through four foil surfaces u tmam and downstmam of the target. We coneued our mcIIunmeNs for the fragmentationin the CRY9 foils. A pmpaga&n fonnula (Bmchtmann er al., 1988a)for the mlation between the distributions of the incoming and outgoing partides on the target a&ces was used. A correction was made for the electnnnagnetic dissociationeffect ( Brechtmann et ul.. 1988b).For the total charge changing fragmentationcross sections we okained :
558
s. CEccHINI et al.
0
0
0
r
0
I
0
0
0
0
Fig.4 : Partial fragmentationcross sections in Cu for silicon ions of 14.5 GeV/nucleon and sulphur ions of 200 GeV/nucleon into various nuclear fragments for AZ ranging from 1 to 9. CONCLUSIONS We have perfoned a new calibration of the INTERCAST CR39 of type L6; there is no indication of aging in the reduced etch rate p for two yeas old CR39. We have placed an upper limit at 9098confrdencc level for the production of nuclei with fractionalcharge at the level of less than 2.6x10-4of the analysed fragments. We have measured the total and partial charge changing fragmentation cross sections of silicon and sulphur in Cu targets. ACKNOWLEDGEMENTS We would like to thank Drs. P.Baiocchi, G.G.Gianiand G.Iori of the lntetcast Company for their active cooperation. We thank Dr. D.Beavisand the staff of the Brookhaven AGS acceleratorfor the silicon and gold exposures, the CERN SPS staff for the sulphur exposure. We thank our technical staff for the help in the analysis of the stacks. REFERENCES
Bmchunann, C., and W.Heinrich (1988a).Measurementsof elemental fragmentationcross section for relativisticheavy ions using CR39 plastic nuclear track detectors. Nucl. Instr. Merh..B2p. 675. Bnchtmann, C.. and W. Heinrich (1988b).Fragmentation cmss section of 3% at 0.7, 1.2 and 200 GeV/nucleon. ZPhys. U ,463. Btechtmann, C., W. Heinrich, and E.V.Benton (1989). Fragmentation cross section of %i at 14.5 GeV/nucleon. Phys. Rev. C 2.2222. De Rujula, A., R.C.Giles and R.L.Jaffe (1978). Unconfined quarks and gluons. Phys. Rev. DJl ,285. Fleischer, R., P.B.Price, and R.M.Walker(1976). Nuclear Trucks in Soli&, California Press, pg.18 MACROCollaboration(1991).lmptovements of the CR39 polymer for the MACROexperiment at the Gran Sasso Laboratory. Nucl.Tracks Rat&at. Meas.,&I, 641. No& A.. 0. Rusch, H. Rocher. J. Dmute and W. Heinrich (1988) . ‘IBe Siegen automatic measurmg system for nuclear track detectors: new development&Nucl. Tracks Radiat. Meas., 15,265. Rice, P.B.. R.Guoxiao. and T.WilJiams(1988). Electromagneticspallation of 6.4-TeV % nuclei. Phys.Rev. Lat. 41 , 2193.