1. Characterization of n_TOF fission samples
Rosa Vlastou
National Technical University of Athens, Department of Physics, Athens, Greece

2. FIC 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 - 7
7(<66)
OSC2.2 2
-0.02
185.37
Th-232
1,2
38.2 80 24
FADC4.2 3
-0.01
185.38
3,4
37.6 25 9
FADC4.3 4
185.39
U-235
9,10
35.6 23
FADC1.3 5
0.01
185.4
U-236
16,17
11.15 21
FADC3.2 6
0.021
18,19
10 .20 19
FADC3.1
0.031
U-238
20,21
23.3 17
FADC2.3 8
0.042
22,23
25.4 16
FADC2.2
0.052
Np-237
28,29
12.82 15
FADC3.3 10
0.077
U-234 50 14 11
0.087
5.17 13 12
0.098
OSC2.1
0.108
5.46
OSC1.4
0.119
5.28
OSC1.3
0.129
5.4
OSC1.2
0.14
185.53
13,14
12.79
FADC1.2
0.15
185.54 78
5 *
FADC1.1 18
0.161
209,210
20*
FADC2.1 BG
Cf-252 20

3. Characterization
1. Homogeneity Using CR-39 plastic track detectors 2. Mass – Contamination Using 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

4. 1. Homogeneity K. Ioannidis & K
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/mm Np: activity 1.3x10 5 Bq min exposure time 234U : activity 2x10 6 Bq sec exposure time U : activity 360 Bq 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.

5. 234U Np

6. To construct the following diagrams, images were captured every 5 mm
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
5.2 cm diameter
8 cm diameter
Homogeneous distribution within 7-9%

7. 2. Mass – Contamination M. Diakaki , R
2. Mass – Contamination M.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 detector MCNP simulations to define the effective solid angle for each case

8. 234U (4a)
From the two sides of 324U (4a and 4b) the Total Mass was estimated as mg , while the nominal Total Mass was 5.46 mg

9. 232U contamination 234U (2.5x105y) 232U (69y)
232U 228Th 224Ra 212Bi 220Rn Po Po
232U contamination : %

10. Contamination of the scattering chamber
4000sec
80.000sec
Cleaning the contaminated parts of the chamber reduced the contamination by ~50%

11. 237Np (28) measured in the air out of the chamber
From one side of 327Np (28 ) the Mass was estimated as mg , while the nominal Total Mass from both sides was mg
241Am contamination : %

12. In order to do RBS measurements the external beam system will be used to avoid further contamination of the chamber
Work in progress