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Automatic α-spot-diameter measurements of large ECE CR39 detectors
0735-245X/91 S3.00 + .00 Pergamon Press pie
NucL Tracks Radiat. Meas., Vol. 19, Nos I--4, pp. 239-240, 1991 Int. J. Radiat. Appl. lnstrum., Part D
Printed in Great Britain
AUTOMATIC e-SPOT-DIAMETER
MEASUREMENTS
OF LARGE ECE CR39 DETECTORS +
M. BALCAZAR,
M. E. CAMACHO,
L. TAVERA and C. ANDRADE
Instituto Nacional de Investigaciones Nucleares. Apartado Postal 18-1027, M6xico, 11801, M~xico. + Instituto Mexicano del Petr61eo, M~xico, D.F., M~xico.
D.F.
ABSTRACT Sheets of ECE CR39 detectors, 56 cm 2 of area are analyzed in a fast-real-time opto-electronic system. Developed software permits: i) automatic scanning of the whole detector area, 2) elimination of unwanted b a c k g r o u n d noise, 3) separation of mixed spots, 4) printing of spot-di~ meter histograms and 5) fast ECE efficiency determination. To test the sy~tex., CR39 were exposed to ten energies of an e-collimated beam in ten separated zones. Optimization of pre-etching time, electric field and frequency parameters are easily achieved, after ECE in a large electrochemical etching cell. KEYWORDS Automatic ~-ECE spots measurements; Description
of Experimental
large electrochemical
etching cell;
SSNTD.
set up
An opto-electronic system and a large electrochemical etching cell, both home made devices, is a useful combination for fast-real-time analysis of electrochemically etched CR39 detectors. The main advantages of this combination are: i) Analysis of different irradiation conditions, such as type of particles, energies and angles of incidence can be performed on the same detector sheet. 2) All irradiated areas in the detector are under the same ECE conditions, i.e. electric field, frequency, time, temperature and concentration of etchant. 3) Spot density, diameter distribution and mean spot diameter are automatically evaluated using identically analysis conditions An the optoelectronic system, i.e. erosion, filtering and background elimination level. Resdl£s and Discussion Several sheets of CR39 detectors, 300 ~m thick, 56 cm 2 of area were irradiated in vacuum with a collimated beam of monoenergetic e-particles in ten separated zones, e-particle energies from .7 MeV up to 5.5 MeV were obtained by degrading a beam of 2~ IAm source with thin films. Electrochemical etching process is carried out in a large electrochemical etching cell, then detectors are evaluated in a real-time opto-electronic system. The analyzer consists of a horizontal detector holder which is automatically scanned under an optical microscope and a CCD camera by an attached computer. The effectof ECE conditions are appreciated in CR39 detector sheets shown in Figure la~and Figure 2. Electric field was similar in both cases, 35 kV/cm and 30 kV/cm, respectively. NO pre-etching time was used in the first case~ whereas sheet 2 has 60 minutes pre-etching time, reducing electrochemical etching time from 90 minutes for the first case to 50 minutes for the second one. Frequencies were 5 kHz and 20 kHz, respectively. All detectors were etched in 25% NaOH at 70*C. The main difference in both detectors is : presence of unwanted background and a tendency of fading for hi gh~nergy ~-spots when no pre-etching is used. Mean track spot as a function of a-energy is shown in Figure 2; the fading effect and large deviation of size spot is evident for the no pre-etched detector; its efficiency is 15% lower than the pre-etched one. Finally, Figure 3 shows six CR39 detector sheets, irradiated under the same controlled conditions with ten e-energies each. Sheet 1 and sheet 2 are the same of those shown in Figure 1 and Figure 2, respectively. Sheet 3 was over pre-etched for 210 minutes which avoided spot formation for 1 MeV, 1.5 MeV, 2 MeV and 2.5 MeV a-particles . Sheet 4 through sheet 6 had no pre-etching; additionally, sheet 4 had short ECE time (60 minutes), sheet 5 had small electric field (20 kV/cm) and sheet 6, both small electric field (15 kV/cm) and short ECE time (60 minutes).
239
240
M. BALCAZAR et aL
Fig. la. Unwanted background is obtained without preetching time.
MEAN
TRACK
SPOT
Fig. 2. Good ECE efficiency and background removal is achieved. See text for ECE conditions.
=m
90
rf
t\ 70
'i
I
-
.L
50
2C
|
t
t
|
I
I
2
3
4
5
ENERGY
I
MeV
Fig. lb. Decreasing of spot-diameter size is observed at high S-energy without pre-etching.
Fig. 3. The six CR39 detector sheets were irradiated under the same controlled conditions with ten ~-energies each. Proper ECE conditions are a key factor for good detection efficiency.
NucL Tracks Radiat. Meas., Vol. 19, Nos I--4, pp. 239-240, 1991 Int. J. Radiat. Appl. lnstrum., Part D
Printed in Great Britain
AUTOMATIC e-SPOT-DIAMETER
MEASUREMENTS
OF LARGE ECE CR39 DETECTORS +
M. BALCAZAR,
M. E. CAMACHO,
L. TAVERA and C. ANDRADE
Instituto Nacional de Investigaciones Nucleares. Apartado Postal 18-1027, M6xico, 11801, M~xico. + Instituto Mexicano del Petr61eo, M~xico, D.F., M~xico.
D.F.
ABSTRACT Sheets of ECE CR39 detectors, 56 cm 2 of area are analyzed in a fast-real-time opto-electronic system. Developed software permits: i) automatic scanning of the whole detector area, 2) elimination of unwanted b a c k g r o u n d noise, 3) separation of mixed spots, 4) printing of spot-di~ meter histograms and 5) fast ECE efficiency determination. To test the sy~tex., CR39 were exposed to ten energies of an e-collimated beam in ten separated zones. Optimization of pre-etching time, electric field and frequency parameters are easily achieved, after ECE in a large electrochemical etching cell. KEYWORDS Automatic ~-ECE spots measurements; Description
of Experimental
large electrochemical
etching cell;
SSNTD.
set up
An opto-electronic system and a large electrochemical etching cell, both home made devices, is a useful combination for fast-real-time analysis of electrochemically etched CR39 detectors. The main advantages of this combination are: i) Analysis of different irradiation conditions, such as type of particles, energies and angles of incidence can be performed on the same detector sheet. 2) All irradiated areas in the detector are under the same ECE conditions, i.e. electric field, frequency, time, temperature and concentration of etchant. 3) Spot density, diameter distribution and mean spot diameter are automatically evaluated using identically analysis conditions An the optoelectronic system, i.e. erosion, filtering and background elimination level. Resdl£s and Discussion Several sheets of CR39 detectors, 300 ~m thick, 56 cm 2 of area were irradiated in vacuum with a collimated beam of monoenergetic e-particles in ten separated zones, e-particle energies from .7 MeV up to 5.5 MeV were obtained by degrading a beam of 2~ IAm source with thin films. Electrochemical etching process is carried out in a large electrochemical etching cell, then detectors are evaluated in a real-time opto-electronic system. The analyzer consists of a horizontal detector holder which is automatically scanned under an optical microscope and a CCD camera by an attached computer. The effectof ECE conditions are appreciated in CR39 detector sheets shown in Figure la~and Figure 2. Electric field was similar in both cases, 35 kV/cm and 30 kV/cm, respectively. NO pre-etching time was used in the first case~ whereas sheet 2 has 60 minutes pre-etching time, reducing electrochemical etching time from 90 minutes for the first case to 50 minutes for the second one. Frequencies were 5 kHz and 20 kHz, respectively. All detectors were etched in 25% NaOH at 70*C. The main difference in both detectors is : presence of unwanted background and a tendency of fading for hi gh~nergy ~-spots when no pre-etching is used. Mean track spot as a function of a-energy is shown in Figure 2; the fading effect and large deviation of size spot is evident for the no pre-etched detector; its efficiency is 15% lower than the pre-etched one. Finally, Figure 3 shows six CR39 detector sheets, irradiated under the same controlled conditions with ten e-energies each. Sheet 1 and sheet 2 are the same of those shown in Figure 1 and Figure 2, respectively. Sheet 3 was over pre-etched for 210 minutes which avoided spot formation for 1 MeV, 1.5 MeV, 2 MeV and 2.5 MeV a-particles . Sheet 4 through sheet 6 had no pre-etching; additionally, sheet 4 had short ECE time (60 minutes), sheet 5 had small electric field (20 kV/cm) and sheet 6, both small electric field (15 kV/cm) and short ECE time (60 minutes).
239
240
M. BALCAZAR et aL
Fig. la. Unwanted background is obtained without preetching time.
MEAN
TRACK
SPOT
Fig. 2. Good ECE efficiency and background removal is achieved. See text for ECE conditions.
=m
90
rf
t\ 70
'i
I
-
.L
50
2C
|
t
t
|
I
I
2
3
4
5
ENERGY
I
MeV
Fig. lb. Decreasing of spot-diameter size is observed at high S-energy without pre-etching.
Fig. 3. The six CR39 detector sheets were irradiated under the same controlled conditions with ten ~-energies each. Proper ECE conditions are a key factor for good detection efficiency.