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

CF

eF Y p p s a t

CY

e 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

CY

e 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

C

e s a t

Scattered events

Direct events (C)

Scattering Schematic

Transmission 13%

Attenuation 20%

(1 )nreference

CY

e 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)

Re

lati

ve

co

ntr

ibu

tio

n

Transmission

Portscattering

Backscattering

1 1nreference

CY

e 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

CY

e 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