characterization of n_tof fission samples
DESCRIPTION
Characterization of n_TOF fission samples. National Technical University of Athens, Department of Physics, Athens, Greece. Rosa Vlastou. Characterization. - PowerPoint PPT PresentationTRANSCRIPT
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Characterization of n_TOF fission samples
Rosa Vlastou
National Technical University of Athens, Department of Physics, Athens, Greece
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FIC0 2003 targets description
Position in the beam
Position from U5 Flight path Isotope Label Mass Diameter
Front End channel
DAQ channel
TDC channel FADC.channel
1 -0.03 185.36 Dummy - - - 1 7 7(<66) OSC2.2
2 -0.02 185.37 Th-232 1,2 38.2 80 24 1 1 FADC4.2
3 -0.01 185.38 Th-232 3,4 37.6 80 25 9 9 FADC4.3
4 0 185.39 U-235 9,10 35.6 80 23 2 2 FADC1.3
5 0.01 185.4 U-236 16,17 11.15 80 21 3 3 FADC3.2
6 0.021 185.411 U-236 18,19 10 .20 80 19 5 5 FADC3.1
7 0.031 185.421 U-238 20,21 23.3 80 17 6 6 FADC2.3
8 0.042 185.432 U-238 22,23 25.4 80 16 8 8 FADC2.2
9 0.052 185.442 Np-237 28,29 12.82 80 15 4 4 FADC3.3
10 0.077 185.467 U-234 7 5 50 14 - - -
11 0.087 185.477 U-234 6 5.17 50 13 - - -
12 0.098 185.488 U-234 5 5.17 50 12 10 10 OSC2.1
13 0.108 185.498 U-234 4 5.46 50 11 11 11 OSC1.4
14 0.119 185.509 U-234 3 5.28 50 10 12 12 OSC1.3
15 0.129 185.519 U-234 2 5.4 50 9 13 13 OSC1.2
16 0.14 185.53 U-235 13,14 12.79 50 7 16 16 FADC1.2
17 0.15 185.54 U-235 78 5 * 50 5 14 14 FADC1.1
18 0.161 185.551 U-238 209,210 20* 50 3 15 15 FADC2.1
BG - - Cf-252 10 7 20 - - -
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1. Homogeneity Using CR-39 plastic track detectors
2. Mass – ContaminationUsing alpha-spectroscopy and Rutherford Back Scattering
The targets were thin layers of 100% enriched isotopes depοsited on 100μm thick Al backing using the painting technique
Characterization
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1. Homogeneity
K.Ioannidis & K.Stamoulis : University of Ioannina
CR-39 track plastic detectors, placed on top of the samples for a few seconds to a few hours, depending on the activity of the sample, in order to achieve a
surface tracks’ concentration of at least 200 tracks/mm2.
237Np: activity 1.3x10 5 Bq 4 min exposure time
234U : activity 2x10 6 Bq 16 sec exposure time
238U : activity 360 Bq 24 hours exposure time
The detectors were etched in a 6 N aqueous NaOH solution, maintained at 75 °C in a water bath with a temperature control better than 1°C. Then a number of
images of the detectors’ surfaces were captured with the use of a microscope - video camera - frame grabber - computer recording arrangement.
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234U 237Np
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8 cm diameter5.2 cm diameter
To construct the following diagrams, images were captured every 5 mm.
Then the images were automatically analyzed using the TRIAC II software to count the number of tracks per 5x5 mm2
Homogeneous distribution within 7-9%
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2. Mass – ContaminationM.Diakaki , R.Vlastou
Using alpha-spectroscopy, in a scattering chamber at a vacuum ~10-2 Torr 80mm2 Si Surface Barrier detector with a Ta mask of 4mm diameter and a calibrated
241Am α-source with various masks and at various distances from the detectorMCNP simulations to define the effective solid angle for each case
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234U (4a)
From the two sides of 324U (4a and 4b) the Total Mass was estimated as 5.38+- 0.26 mg , while the nominal Total Mass was 5.46 mg
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234U (2.5x105y)
232U (69y)
232U 228Th 224Ra 212Bi 220Rn 216Po 212Po
232U contamination : 0.03 %
232U contamination
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Contamination of the scattering chamber
4000sec
80.000sec
Cleaning the contaminated parts of the chamber reduced the contamination by ~50%
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237Np (28) measured in the air out of the chamber
From one side of 327Np (28 ) the Mass was estimated as 6.36+- 0.26 mg , while the nominal Total Mass from both sides was 12.82 mg
241Am contamination : 0.02 %
237Np
241Am
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In order to do RBS measurements the external beam system will be used to avoid further contamination of the chamber
Work in progress