Loading in 5 sec....

N_TOF fission data of interest for ADSPowerPoint Presentation

N_TOF fission data of interest for ADS

- 53 Views
- Uploaded on

Download Presentation
## PowerPoint Slideshow about ' N_TOF fission data of interest for ADS' - sumana

**An Image/Link below is provided (as is) to download presentation**

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript

Nuclear data needs

- Simulation and design of Gen-IV and ADS systems require accurate nuclear data
- Current data libraries present important discrepancies and lacks.

Capture

decay

Thorium fuel- 232Th + n 233Th 233Pa 233U (fissile)

232U

233U

234U

235U

236U

237U

238U

231Pa

232Pa

233Pa

234Pa

235Pa

230Th

231Th

232Th

233Th

234Th

Experimental Campaign

- A set of measurements of neutron-induced fission in actinides was launched within the FP5.
- Fission measurements in the framework of the n_TOF Collaboration and construction of the n_TOF facility.

Fission Ionization Chamber Assembly

Ionization chamber

Gas used: Ar (90 %) CF4 (10 %).

Gas pressure: 720 mbar

Electric field: 600 V/cm

Gap pitch: 5 mm

Deposit diameter: 5 cm

Deposit thickness: 125 µg/cm

Support thickness: 100 µm (Al)

Deposits on both sides.

Electrode diameter: 12 cm

Electrode thick.: 15 µm (Al)

Windows diameter: 12 cm (KAPTON 125 µm)

List of Targets

----FIC0----

235U - 47mg (3 targets)

238U - 110mg (3 targets)

232Th - 80mg (2 targets)

236U - 20mg (2 targets)

237Np - 10mg (1 target)

234U - 34mg (6 targets)

----FIC1----

235U - 30mg (1 targets)

238U - 90mg (2 targets)

241Am - 2mg (4 targets)

243Am - 10mg (4 targets)

245Cm - 2mg (2 target)

233U - 20mg (2 targets)

PPACs @ n_TOF

- 10 detectors 9 targets
- U-234(2) and Th-232(5)
- Two reference targets: U-235 y U-238
- Less than 1 % of flux attenuation in the full setup.

Measured isotopes

- Minor actinide : 237Np
- Thorium cycle : 233U, 234U, 232Th
- Spallation target : 209Bi, natPb
- Reference isotopes : 235U, 238U

- Fissile target in a thin backing sandwiched by two detectors Detection of both fission fragments in coincidence.
- Fission event reconstruction: target position and emission angle. Efficiency limited by the cut at large angles.

Cathode Positioning (I)

- Positioning by using stripped cathodes and delay line readout.
- The cathode signal is split in the delay line and transmitted to both ends

Stripped Cathode

Delay Line

Cathode positioning (II)

Diagonal condition:

(Tch1-Tanode)+(Tch2-Tanode)=DLT

DLT: Total delay line length (~320 ns)

The time difference

between both cathode

ends provides

the position of the signal.

Targets (II)

- Measurement of thickness and homogeneity by alpha counting and/or proton scattering.
- High purity samples (> 99 % for U-234).

234U

Y (mm)

X (mm)

activity

The n_TOF Data Acquisition System

- The n_TOF DAQ consists of 54 flash ADC channels with 8 bit amplitude resolution and sampling of 500 MSample/s.
- The full history of EVERY detector (BaF2 crystals and monitors) is digitised during a period of 16 ms (0.7 eV < En < 20 GeV) and recorded permanently on tape. Very useful feature since the raw data can be always re-investigated.
- The system has nearly zero dead time.
- 7.5 TB disk space for temporary storage.
- Typical data rate of 2-3 TB/day on tape after compression.
- Pulse shape analysis is performed on the fly at the LXBATCH Linux Batch Farm at CERN (30 CPUs exclusively dedicated) and stored in highly compressed Data Summary Tapes.
- Quasi on-line analysis of the data with full statistics.

One of the big successes of n_TOF. Many TOF facilities are following the n_TOF example and moving to digital electronics!

PPAC signal analysis

- Negative loop should be first
- Xpos-Xneg < constant
- const1 < Hneg/Hpos < const2

Light vs. Heavy Fission Fragments

Cathode signals for En around 1 MeV

Cross Section Analysis

- (E): fission cross section
- n (x,y,E): fission rate obtained from raw data
- (x,y): surface density of the target
- (E): detection setup efficiency
a(x,y,E)/ b(x,y,E) ≈ 1 ± 0.01 (1%)

Log E =5.8

Log E =5.9

Cos ()

Cos ()

Cos ()

Log E =5.4

Log E =5.6

Log E =5.5

Fission Fragment Angular DistributionU-234 FFAD for neutron energies near the fission threshold

X (mm)

n_TOF beam at fission campaign- Neutron spectrum in the whole energy range.
- Beam profile

U234 resonances

Np237 resonances

Conclusions

- The coincidence method has been used to obtain the fission results for the extensive n_TOF neutron energy range.
- Th233, U234, Np237 results have been already produced and U233 is in progress.
- Important discrepancies have been found in the Np237 resonance region.

CERN

FIC Design

- Gas – Ar 90%+CF4 10%
- Pressure – 600 mbar
- Distance – 5 mm
- HV – 300 V
- 17 targets in the beam
- “noise” electrode

Download Presentation

Connecting to Server..