1. The 14 MeV Frascati Neutron Generator (FNG)
HeRe in Italy, ENEA Centro Ricerche Frascati
December 2-3, 2013
The 14 MeV Frascati Neutron Generator (FNG)
Maurizio Angelone
Associazione ENEA-EURATOM sulla Fusione
Via E. Fermi, 45 – Frascati (Italy)

2. Introduction
The Frascati Neutron Generator (FNG) started operations in November making available 14 MeV neutrons at a medium intensity (10^11n/s) to EU Fusion Community. The Fusion Neutronics community strongly supported the idea of international collaboration in neutronics experiments, in data base & code improvement and in development of (new) experimental techniques.
FNG has been designed at ENEA.
FNG has been realized by ENEA (Fusion Division) at is own expense.
FNG has been (and is) extensively used for performing benchmarks and mock-up experiments of interest to Fusion neutronics to validate Nuclear Data and Codes.
A number of activities in various fields (& collaborations) carried out at FNG so far

3. Miscellaneous Activities at FNG
Apart from the Benchmarks and Mock-yup experiment for fusion neutronics, FNG is used for several collaboration/service in many different fields:
Test of electronics chips, components, cards, software etc.
Irradiation of “in vivo” samples (e.g. cells, mice, vegetables etc. for radiation induced effects  space dosimetry)
Test of new detectors (e.g. diamond, GEM, RPC, etc.)
Detector calibration (e.g. Xenon detector for DAMA exp.)
Efficiency of dosimeters (for dosimetry, e.g. CR-39)

4. The Facility
The 14 MeV Frascati Neutron Generator (FNG) is in operation since November 1992.
FNG is a linear electrostatic accelerator in which up to 1 mA D+ ions are accelerated onto a tritiated target to produce up to 1.0E+11 n/s 14 MeV neutrons via the nuclear fusion reaction :
D+T a+n (Q=17.4 MeV)
The FNG neutron source is almost isotropic, its absolute strenght is calibrated at ±3% using the Associated Particle method.
Using a deuterated target also 2.5 MeV neutrons can be produced by the D+D n+3He reaction The maximum strenght is < 1.0E+09 n/s calibrated by activation methods (Indium foils) 4

5. FNG Parameters Operation continuous or pulse mode (tp = 6s minimum)
D-T operation
D-D operation
Max neutron yield
1*1011 n/s
1*109 n/s
Max neutron flux  volume
5*109 neutrons cm-2 s-1  1cm3
5*107 neutrons cm-2 s-1  1cm3
Max irradiation volume  flux
A few cm3  107/s/(4**m2)
A few cm3  105/s/(4**m2)
Max irradiation time- targets
25 hours (one target)
continuous
Average utilization/year
> 150 hours/years
Free time available for irradiation
200 hours/years
Maximum achievable fluence
1*1015 n/cm2 on a 1 cm3 sample
1*1013 n/cm2 on a 1 cm3 sample
Operation continuous or pulse mode (tp = 6s minimum)

6. FNG MAIN COMPONENTS H.V. TERMINAL ION SOURCE
ION SOURCE CHAMBER –EINZ LENS
BENDING MAGNET
QUADRUPOLES
ACCELERATOR TUBE
VACUUM PUMP
TARGET

8. FNG
A neutron generator to be reliable must have its neutron source absolutely calibrated at the state-of-the-art technique  mandatory for performing benchmarks and mock-up experiments

9. Absolute source calibration
Ratio activation measurements to SSD using the 27Al(n,)24Na ad 92Nb(n,n’)92mNb reactions
Neutron yield is monitored measuring the alpha particles from the T(d,n) with a Silicon Surface barrier Detector (SSD)

10. Experimental Calibration & simulation using MCNP
U-238 F.C response

11. SOURCE SPECTRUM SIMULATION
D-T and D-D neutron energy spectra are properly modelled as a two body reaction
Beam energy goes from Emax to 0 during deuteron slowing down (thick target!)
Relativistic formula used in the latest version

12. A “ad hoc” source routine was implemented in MCNP.
This routine takes in to account all the physical aspects of the neutron production from the beam-target interaction, including ions scattering, fusion cross-section anisotropy, etc. In the MCNP geometry the target holder and the used detectors dimensions and materials are also described.
Pd = point detector
Cf = cell flux estimator
The Source routine was developed by ENEA Frascati and Institut Jozef Stefan (JSI) in Ljubljana and is available in SINBAD database at NEA. Latest version up to 10 MeV beam energy (not yet in SINBAD)

13. Spectrum with Diamond detector at 90°°
The Source routine was recently validate using Diamond Detectors located at various angles around FNG target
Spectrum with Diamond detector at 90°°
FNG 0°
90°
Diamond Detector

14. CVD diamond 0°respect the beam. (Beam energy 230 keV)

15. CVD diamond 0° respect the beam. (Beam energy 290 keV)

16. Experimental techniques in the FNG laboratories :
Activation technique
X- and g-ray spectroscopy
Dosimetry
Decay heat detection system

17. Main Experimental Tools
Two HPGe detectors absolutely calibrated for g-ray spectroscopy plus a number of activation foils.
TOLEDO TLD reader plus several types of TLD detectors (LiF, GR-206, GR-207, TLD-300); g and n dose separation
GM tubes for g-dose measurements
Two F.C. detectors (U-238 and U-235)
Scintillators
CVD diamond detectors for thermal and fast neutrons, X-ray and UV detection.
MCNP and MCNPX codes for modelling and testing the experiments.
Codes for neutron spectrum unfolding

18. Thank You !