A. BA. Bâ, â, S. Balestra, M. Cozzi, G. Giacomelli, R. Giacomelli, M. Giorgini, A. Kumar S. Balestra, M. Cozzi, G. Giacomelli, R. Giacomelli, M. Giorgini, A. Kumar G. Mandrioli, S. Manzoor, A.R. Margiotta, E. Medinaceli, L. Patrizii, V. Popa,G. Mandrioli, S. Manzoor, A.R. Margiotta, E. Medinaceli, L. Patrizii, V. Popa,I.E. Qureshi, M.A. Rana, Z. Sahnoun, G. Sirri, M. Spurio, I. Traoré, C. Valieri I.E. Qureshi, M.A. Rana, Z. Sahnoun, G. Sirri, M. Spurio, I. Traoré, C. Valieri

Bulk etch rate measurements and calibrations

of plastic nuclear track detectors

V. TOGOINFN - BOLOGNA

Bologna, Sept 1st 2008 – 24th ICNTSBologna, Sept 1st 2008 – 24th ICNTS

New calibrations of CR39 and Makrofol nuclear track detectors have been obtained using 158 A GeV Pb82+ and In49+ ions

A new method for the bulk etch rate determination, using both cone height and base diameter measurements, was developed.

The most sensitive Nuclear track detector employed in several scientific and technological applications is CR39

We recall that more than 4000 m2 of CR39 detectors were used in the MACROand SLIM experiments devoted to the search for new massive particles in the cosmic radiation (magnetic monopoles, nuclearites...)

Makrofol and Lexan polycarbonates are also largely employed.

Accurate detector calibrations are requiredAccurate detector calibrations are required

CR39 and MAKROFOLCR39 and MAKROFOL

CR39® (PPG Industries Inc.) (C12H18O7; 1.32 g/cm3)

Standard INTERCAST CR39: mainly used for sun glasses

Improved in order to achieve:• low detection threshold; (Z/ ~ 5)• high sensitivity in a large range of energy losses, • high quality of the post-etched surface • stability of the sensitivity over long periods of time (several years) [Aging effect] • uniformity of sensitivity for mass-produced sheets

In order to achieve these goals, a specific scientific line of production was designed and implemented.

MAKROFOL® (BAYER) (CMAKROFOL® (BAYER) (C1616HH1414OO33 ; 1.29 g/cm ; 1.29 g/cm33))

Polycarbonate films Polycarbonate films • high quality transmission, high quality transmission, • excellent surface uniformityexcellent surface uniformity• high detection threshold; (Z/high detection threshold; (Z/ ~ 50) ~ 50)

Survived beam

Fragments

Target

Incident beam

Target

50 cm

Air gapCR39

EXPOSURE SET UPEXPOSURE SET UP

Beams:Beams: ► ► SPS@ CERN (Geneva)SPS@ CERN (Geneva) 158 A GeV Pb158 A GeV Pb82+82+ & In & In49+49+

CR39CR39

in 6 N NaOH + 1% ethyl alcohol at 70°C for 40 h

MAKROFOLMAKROFOL

in 6 N KOH + 20% ethyl alcohol at 50°C for 8 h

ETCHING CONDITIONSETCHING CONDITIONS

The etching was performed in a stainless steel tank equipped with internal thermo-resistances and amotorized stirring head. The temperature was stable to within ±0.1 C. In order to keep homogeneous the solution and to avoid that etched products deposit on the detector surfaces, a continuous stirring was applied during etching

BULK ETCH RATE (VBULK ETCH RATE (VBB) MEASUREMENTS) MEASUREMENTS

Original Surface

Etched SurfacevBt

By Thickness methodBy Thickness method

vvB B = = xx/2.t/2.t

Based on the measurement of the thickness of the detector after different etching times. The thickness is measured with an electronic micrometer of 1 µm accuracy in 25 positions on the detector foil.

BULK ETCH RATE (VBULK ETCH RATE (VBB) MEASUREMENTS) MEASUREMENTS

Le

D

By D-LBy D-Lee method method The bulk etch rate from the cone height and base diameter measurements

Normally incident particle

D and Le measured with a Leica optical microscope coupled to aCCD camera and a video monitor

Le obtained by multiplyingthe measured cone height by the refractive index n of the etched detector material

BULK ETCH RATE (VBULK ETCH RATE (VBB) MEASUREMENTS) MEASUREMENTS

Le

D

By D-LBy D-Lee method method

Le (vT vB )t

D2vB t(vT vB )

(vT vB )

CALIBRATION OF CR39CALIBRATION OF CR39

Area distribution (measurement on two faces) of 158 A Area distribution (measurement on two faces) of 158 A GeV GeV 4949In ions and their fragments in CR39 after 40 h In ions and their fragments in CR39 after 40 h etching in 6N NaOH+1 % Ethyl Alcohol (by volume) at 70 etching in 6N NaOH+1 % Ethyl Alcohol (by volume) at 70 ooCC

(a)

Z/ = 10

2030 40

Z/ = 46

Z/ = 49(b)

p versus REL for CR39 exposed to relativistic indium ions using vBevaluated with the new method. Typical statistical standard deviations are shown at Z/ = 40, 45, 49; for Z/ ≤ 37 the errors are inside the black points.

CALIBRATION OF MAKROFOLCALIBRATION OF MAKROFOL

(a) (b)

Z/ = 78

Z/ = 82

Z/ = 51

60 70

78

83

Area distribution of 158 A GeV Pb ions and their Area distribution of 158 A GeV Pb ions and their fragments (measurement on two faces) in Makrofol fragments (measurement on two faces) in Makrofol after 8 h etching in 6N KOH + Ethyl Alcohol (80 : 20 % after 8 h etching in 6N KOH + Ethyl Alcohol (80 : 20 % by volume) at 50 by volume) at 50 ooC.C.

p versus REL for the Makrofol detector exposed to relativistic Pb ions using vB evaluated with the new method. Typical statistical standard deviations are shown at Z/ = 70, 75, 77; for Z/ ≤ 67 the errors are inside the black points.

CONCLUSIONSCONCLUSIONS

The ‘‘new method’’ for measuring the bulk etch rate for intermediate or high z-values yields slightly smaller uncertainties than the ‘‘standard method’’ (change in thickness)

This comes from the use at the same time of both cone heights and base diameter measurements of tracks.

The values obtained by the two methods are in reasonable agreement

(a)

(b)

(c)

Place the samples in the same positions in the rack if etching performed in more steps

(a) (b)

CR39 sheets after targetCR39 sheets before target

Survived beam

Fragments

Target

Incident beam

Exposure geometry for the relativistic heavy ions for calibration of both CR39 and Makrofol NTDs.

(a) tracks of beam ions before the target and (b) beam tracks and a fragment track after the target from the 0.41 A GeV Fe26+ exposure, see the tracks marked with a red circle.

TRACK SHAPE PARAMETERSTRACK SHAPE PARAMETERS

Track diameter:Track diameter:D = 2vBt[(vT-vB)/(vT+vB)]

1/2

Track length:Track length:LLee = (v = (vTT-v-vBB).t).t

Reduced etch rate:Reduced etch rate:p = vp = vTT/v/vBB

G = 6.3x

158 AGeV Pb82+

G = 6.3x

0.414 AGeV Fe26+

VBt

LVTt

D

IMPROVEMENTS ON CHEMICAL PROCESSINGIMPROVEMENTS ON CHEMICAL PROCESSING

Tracks of 158 A GeV Pb ions in CR39Tracks of 158 A GeV Pb ions in CR39

6N NaOH, 70 6N NaOH, 70 00C, 30 hrC, 30 hr Z/Z/(min.) ~ 5(min.) ~ 5

20 X 20 X

6N NaOH + 1% alcohol 70 6N NaOH + 1% alcohol 70 00C, 40 C, 40 hrhr

Z/Z/(min.) ~ 7(min.) ~ 7

TRACKS OF 158 A GEV PbTRACKS OF 158 A GEV Pb82+82+ IONS + FRAGMENTS IONS + FRAGMENTS IN MAKROFOLIN MAKROFOL

6N KOH + 30% ethyl alcohol, 10 h, 6N KOH + 30% ethyl alcohol, 10 h, 45 45 00CC

50 X

6N NaOH, 95 h, 50 6N NaOH, 95 h, 50 00CC

20 X

Makrofol, 50 Makrofol, 50 ooC, 6N KOH + 20% ethyl alcohol 8 h C, 6N KOH + 20% ethyl alcohol 8 h (a) (a) normal incidence and (b) for 45 incidence, normal incidence and (b) for 45 incidence,

20 X50 X

Z/ (m

in.)

~ 50

OLD

NEW

CALIBRATION GRAPH FOR CR39 CALIBRATION GRAPH FOR CR39

By thickness MethodBy thickness Method

2

2ln

2

1 22

max222

2

2

max

I

TcmAZz

KdxdE

REL e

TE

For each detected charge Restricted Energy Loss (REL)

REL (MeV cm2 g-1)

By D-LBy D-Lee Method Method6N NaOH 70 oC, 30h1.11 ± 0.07 m/h

CALIBRATION GRAPH FOR CR39 CALIBRATION GRAPH FOR CR39

Comparison for CR39 NTDs exposed to 158 A GeV InComparison for CR39 NTDs exposed to 158 A GeV In49+49+ and Pb and Pb82+82+

heavy ions and etched under different “soft” condition. Notice the heavy ions and etched under different “soft” condition. Notice the

p values at Z = 40 and 49 for two etching conditions for CR39. A p values at Z = 40 and 49 for two etching conditions for CR39. A

sharp rise in sensitivity is evident for etching with small fraction of sharp rise in sensitivity is evident for etching with small fraction of

alcohol after Z/alcohol after Z/ 20. 20.

Z = 10

20

40

49

10 20

40

49

67

60

By D-LBy D-Lee Method Method

CALIBRATION COMPARISON FOR CR39 CALIBRATION COMPARISON FOR CR39

RESPONSE CURVES FOR CR39 AND MAKROFOL RESPONSE CURVES FOR CR39 AND MAKROFOL

Comparison for CR39 NTDs exposed to 158 A GeV InComparison for CR39 NTDs exposed to 158 A GeV In49+49+ and Pb and Pb82+82+

heavy ions and etched under different “soft” condition. Notice the heavy ions and etched under different “soft” condition. Notice the

p values at Z = 40 and 49 for two etching conditions for CR39. A p values at Z = 40 and 49 for two etching conditions for CR39. A

sharp rise in sensitivity is evident for etching with small fraction of sharp rise in sensitivity is evident for etching with small fraction of

alcohol after Z/alcohol after Z/ 20. 20.

By D-LBy D-Lee Method Method

LENGTH AND BASE AREA OF TRACKS IN LENGTH AND BASE AREA OF TRACKS IN CR39 EXPOSED TO PbCR39 EXPOSED TO Pb82+82+ IONS (158 A IONS (158 A

GEV)GEV)

Z = 82eZ = 82eD = 75 D = 75 mmL = 650 L = 650 mm

Z = 65eZ = 65eD = 69 D = 69 mmL = 169 L = 169 mm

Z = 76eZ = 76eD = 74 D = 74 mmL = 425 L = 425 mm

Z = 20eZ = 20eD = 40 D = 40 mmL = 23 L = 23 mm

Z = 45eZ = 45eD = 59 D = 59 mmL =77 L =77 mm