Method for 14-MeV neutron yield determination using a
MPR neutron spectrometer
Göran Ericsson, H.Sjöstrand, S.Conroy,
E.Andersson Sundén, A.Combo1, N.Cruz1, M.Gatu Johnson, L.Giacomelli, W.Glasser, G.Gorini2, H.Henriksson, A.Hjalmarsson, N.Kronborg, J.Källne, A.Murari3,
S.Popovichev3, P.Ricardo1, E.Ronchi, J.Sousa1, M.Tardocchi2, M.Weiszflog, and EFDA-JET contributors
Dept. of Neutron Research, Uppsala University, Sweden EURATOM-VR Association
1) Associação EURATOM/IST, Centro de Fusão Nuclear, Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal.
2)INFM, Dept. of Physics, Univ. of Milano-Bicocca and Istituto di Fisica del Plasma, EURATOM-ENEA-CNR Association, Milan, Italy
3) JET, Culham Science Center, Oxfordshire, Culham, UK
Neutron yield determination
(1 )
(1 )
n
n n reference
nreference
CFe
F Y p p s a t
CYe p p s a t
•Tokamak•Neutron camera•Absolutely calibrated spectrometer
Neutron emission profile
Δp is derived from neutron camera data
Δp = ±0.15 Uncertainty in Δp is
normally around 0.01 Only the shape of the
neutron emission profile is needed
Neutron emission profile reconstruction from neutron camera data
(1 )referencen
CYe s a tp p
MPR efficiency and count rate
Efficiency calculated from first principles
Depends on well known quantities
Spectrometer able to separate direct and scattered events
2.5% uncertainty
(1 )nreference
Yp p
Ce s a t
Scattered events
Direct events (C)
Scattering Schematic
Transmission 13%
Attenuation 20%
(1 )nreference
CYe p p s a t
Direct
Backscatter < 1%Inscatter (port) 2%
Target foil
Collimation
Vacuum vessel
Plasma (neutron source)
Neutron trajectories
Inscatter (collimator) 7%
MCNP model layoutHorizontal cut Vertical cut
Scattering and transmission is profile dependent (small corrections)
Optimal LOS should minimizes s, t, Δp and Δst
Profile dependence on the scattered flux
Profile dependence along Z=0
0,2
0,4
0,6
0,8
1
1,2
1,4
240 260 280 300 320 340 360
R (cm)
Rel
ativ
e co
ntrib
utio
n
Transmission
Portscattering
Backscattering
1 1nreference
CYe p p a s stt
ResultsTTE DTE1
Systematic uncertainties
Uncertainties are uncorrelated and well defined Efficiency (e) = 2.5% Scattering, attenuation and transmission (t)+ (s) + (a) =
4% Neutron emission profile and LOS (preference) = 3% Background corrections (C) = 0 - 3% Resulting systematic error = 5.5-6.5%
1 1nreference
CYe p p a s t st
Summary
A method to determine the 14-MeV n rate (power) using an absolutely calibrated spectrometer and a neutron camera has been developed
The method provides the yield with <6.5% systematic error
The method has been validated with data from JET’s DTE1 and TTE campaigns