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

  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 - 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 0.021 185.411 18,19 10 .20 19 FADC3.1 0.031 185.421 U-238 20,21 23.3 17 FADC2.3 8 0.042 185.432 22,23 25.4 16 FADC2.2 0.052 185.442 Np-237 28,29 12.82 15 FADC3.3 10 0.077 185.467 U-234 50 14 11 0.087 185.477 5.17 13 12 0.098 185.488 OSC2.1 0.108 185.498 5.46 OSC1.4 0.119 185.509 5.28 OSC1.3 0.129 185.519 5.4 OSC1.2 0.14 185.53 13,14 12.79 FADC1.2 0.15 185.54 78 5 * FADC1.1 18 0.161 185.551 209,210 20* FADC2.1 BG Cf-252 20

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

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/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.

234U 237Np

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%

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

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

232U contamination 234U (2.5x105y) 232U (69y) 232U 228Th 224Ra 212Bi 220Rn 216Po 212Po 232U contamination : 0.03 %

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

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 %

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