1. New instruments for real-time neutron spectrometry from thermal to GeV
R. Bedogni1, J.M. Gomez-Ros1,2, D. Bortot1,3, A. Pola3, M.V. Introini3, A. Esposito1, A. Gentile1, G. Mazzitelli1, B. Buonomo1
1 INFN – LNF Frascati (Italy)
2 CIEMAT Madrid (Spain)
3 Politecnico di Milano (Italy)

2. Introduction

3. Broad energy interval neutron spectrometry at beam-lines
Introduction
Broad energy interval neutron spectrometry at beam-lines
No single-device instrument exists to perform a complete energy range spectrometry (eV - GeV).
To date, the only spectrometric technique able to provide all energy component is the Extended Range Bonner Sphere spectrometer
Limitations:
- time consuming irradiation sessions
- poor energy resolution (partially compensated with a-priori information taken from MC simulations)

4. Introduction
ERBSS

5. BSS counts Guess hypothesis Unfolding (FRUIT) Spectrum Introduction
(+ uncertainties)
Guess hypothesis
(physical models, parameterized spectrum,
MC simulation)
Unfolding (FRUIT)
Altering guess hypothesis till “guess” counts counts are sufficiently in agreement with measured counts
Spectrum

6. ERBSS spectrometry at Vesuvio (ISIS)
Introduction
ERBSS spectrometry at Vesuvio (ISIS)
NIM A 612 (2009)143–148
Radiation Measurements 45 (2010)

7. Introduction
Goal
Providing devices for “real-time” spectrometry of neutron producing facilities over the whole energy interval of production (eV - GeV) with similar measurement performance as the Bonner spheres.
Condensing the characteristics of a BSS in TWO single moderator devices embedding multiple active thermal neutron detectors:
SP2 Spectrometer with isotropic response
CYSP Directional spectrometer
Fields of application
Research accelerators, industry, medical, aerospace, homeland security, cosmic rays measurements

8. Project breakdown Stage 1 Theoretical design of the instruments
Introduction
Project breakdown
Stage 1 Theoretical design of the instruments
Response matrix calculation
Manufacturing and testing passive prototypes
Stage 2 Setting up active thermal detectors (TNDs)
Stage 3 Manufacturing and testing the final spectrometers equipped with active TNDs. 8

9. The SPherical SPectrometer SP2
Stage 1
The SPherical SPectrometer SP2
• Thirty-one thermal neutron detectors along three axes of a 25 cm sphere.
• Positions: radius 0.0 (centre), 5.5, 7.5, 9.5, 11 and 12.5 cm (external)
• Response defined as average reading of detectors at the same radius
• An internal 1 cm thick lead shell (3.5 to 4.5 cm) to enhance high-Energy response
• Isotropic response for practical purposes Pb
NIM A 613, (2010)
NIM A 677, 4-9 (2012)
R = 9

10. The SPherical SPectrometer SP2 - Response matrix
Stage 1
The SPherical SPectrometer SP2 - Response matrix 10

11. Response matrix verification (PTB, 144 keV to 14.8 MeV)
Stage 1
Response matrix verification (PTB, 144 keV to 14.8 MeV)
Tests at different mono-chromatic energies performed with Dy activation foils. Overall uncertainty estimated as ±3% 11

12. Response matrix verification (TSL-Uppsala, 50-180 MeV)
Stage 1
Response matrix verification (TSL-Uppsala, MeV) 12

13. The CYlindrical SPectrometer CYSP
Stage 1
The CYlindrical SPectrometer CYSP
• Seven TNDs along the axis
• Spectral resolution and lateral rejection
• HPDE Collimator 50 cm diam x 30 cm h
Hole diameter 16 cm, B-plastic lined
• Capsule for detectors: 20 cm diam,
includes one cm lead disk (high-E)
• Air holes to increase deep response
HDPE AIR Pb B-plastic 13

14. Stage 1
CYSP response matrix 1 2 3 4 6 5 7 14

15. Active detectors Constraints (1) Miniaturization (≈1 cm)
Stage 2
Active detectors
Constraints
(1) Miniaturization (≈1 cm)
(2) Sensitivity such to allow responding from Sv/h to Sv/h
(3) Excellent photon rejection
(4) Low-cost (31 TNDs in a single spherical device)
Two types of TNDs (different levels of cost/sensitivity):
TNPD pulse detector (~0.04 cm2), producing a PHD
TNRD rate detector, giving a DC voltage level that is proportional to the thermal neutron fluence rate.
Lowest measurable thermal neutron flux ≈ tens cm-2 s-1 15

16. Fabrication and testing facilites
Stage 2
Fabrication and testing facilites
Commercially available solid state devices are made sensitive to thermal neutrons through a customized physico-chemical process
Each detector is individually calibrated in a known thermal neutron field.
Batch reproducibility ±5%
Conv. Thermal Flux
1270±40
True thermal Flux
1440±40
Total flux
3300±100
“Non thermal” contrib.
1.6% 16

17. The “rate detector” TNRD
Stage 2
The “rate detector” TNRD
The device. The active area is one cm2 and overall dimensions are 1.5 cm x 1 cm x 0.4 cm. This signal is amplified in a low-voltage electronics module (developed by the project team) and acquired by a PC through an ADC.
Typical calibration coefficient (93±3) cm-2 s-1 mV-1.
Linearity Tested in ex-core thermal column at the ENEA Casaccia (Rome) Triga reactor
• Linear response de 7E E+5 cm-2 s-1.
• Uncertainty better than 4%
• Minimum detectable flux < 50 cm-2 s-1.
The measurement range can be changed by modifying the gain of the amplification module. 17

18. Stage 3
Manufacturing and testing the final spectrometers equipped with active TNDs.
lateral protection
B-plastic
collimator
detectors
capsule for detectors 18

19. CYSP was fabricated and tested with:
Stage 3
Manufacturing and testing the final spectrometers equipped with active TNDs.
CYSP was fabricated and tested with:
a continuous-spectrum Am-Be source
( MeV)
monochromatic beams at NPL (0.144 to 16.5 MeV) 19

20. Simultaneous acquisition of up to eight detectors
Stage 3
Signal processing = +
Analog module
designed within the project
Eight channels
(Bias regulator + Preamp +amp)
8 channel digitizer
Simultaneous acquisition of up to eight detectors
(Labview based) 20

21. 3. New active thermal neutron detectors developed 4. Testing phase
Conclusions
Conclusions
1. Broad-energy interval neutron spectrometry at beam-lines can be performed “on-line” with similar performance as those of the ERBSS
2. Two prototypal single-moderator neutron spectrometers, called SP2 and CYSP, were designed in the framework of the INFN project
3. New active thermal neutron detectors developed
4. Testing phase
Done for the CYSP
In progress for CP2

22. End of 2014 / NEURAPID project
Conclusions
End of 2014 / NEURAPID project
ETHERNES Extended THERmal NEutrons Source
A thermal pile at INFN-LNF for thermal neutron detector testing with
Uniformity area 30 cm x 30 cm