Multi-Blade, a Novel Neutron Detector

Multi-Blade, a novel neutron detector

Gábor Galgóczi

MTA Wigner RCP of HAS REGARD group

Outline

● European Spallation Source ● Thermal and cold neutron detection: – Techniques – Challenges at ESS ● The Multi-Blade detector ● Geant4 simulations: – Effect of neutron scattering quantified

European Spallation Source (ESS)

● Novel concepts for neutron sources ● 17 European countries ● User programme starts 2023 ● Benefits: – manufacturing, pharmaceutical drugs – aerospace, engines, plastics – biotechnology

Brightness of ESS

How does ESS work?

● 17 European countries ● User programme starts 2023

LINAC for protons (2GeV)

Samples W target

How does ESS work?

● 17 European countries ● User programme starts 2023 ● Proton beam → Spallation → Neutrons – Moderator idea by Ferenc Mezei LINAC for protons (2GeV) ● Thermal and cold neutrons: Samples W target – ~meV (RHIC: ~GeV)

How does ESS work?

● 17 European countries ● User programme starts 2023 ● Proton beam → Spallation → Neutrons – Moderator idea by Ferenc Mezei LINAC for protons (2GeV)

● Thermal and cold neutrons: Samples W target – ~meV (RHIC: ~GeV) ● Brightness: 30x state of. a. ● New detectors needed!!

Instruments at ESS

Neutron detection w. 3He

● n + 3He → 3H + 1H + 0.764 MeV ● Gamma-ray production → Needs to be surpressed ● Neutron capture x-section huge

Neutron detection w. 3He

● n + 3He → 3H + 1H + 0.764 MeV ● Gamma-ray production → Needs to be surpressed ● Neutron capture x-section huge ● Main source: nuclear weapons programme

https://fas.org/sgp/crs/misc/R41419.pdf Neutron detection w. 10B

● 10 B in B4C ceramic

● Alpha and Li ions are detected in MWPCs

● Dealing with high flux with a high grazing angle C 4 B

neutrons 0 10 4C 1 neutrons B θ θ

q q = 90 degrees = 5 degrees Efficiency 45% at 2.5Å Efficiency <5% at 2.5Å The Multi-Blade

● Usage: – At ESS: FREIA and ESTIA reflectometers ● Requirements: – High rate capability: 105 mm-2s-1 – Spatial resolution (4x0.5 mm) – Max. window scattering: 10-4

F. Piscitelli, F. Messi et al., The Multi-Blade Boron-10-based neutron detector for high intensity neutron reflectometry at ESS, Journal of Instrumentation 12, P03013 (2017) The Multi-Blade

● Usage: – At ESS: FREIA and ESTIA reflectometers ● Requirements: – High rate capability: 105 mm-2s-1 – Spatial resolution (4x0.5 mm) – Max. window scattering: 10-4 ● Geant4 simulations: – To understand scattering in the complex geometry

F. Piscitelli, F. Messi et al., The Multi-Blade Boron-10-based neutron detector for high intensity neutron reflectometry at ESS, Journal of Instrumentation 12, P03013 (2017) The Multi-Blade

● Usage: – At ESS: FREIA and ESTIA reflectometers ● Advantages: – Spatial resolution: ● 2.5 mm x 0.5 mm ● 3 times state of the art

The Multi-Blade

● Usage: – At ESS: FREIA and ESTIA reflectometers ● Advantages: – Spatial resolution: ● 2.5 mm x 0.5 mm ● 3 times state of the art – Max instantaneous rate: – 100 - 500 kHz / mm2 – 10 – 100 times state of the art

The Multi-Blade

Detection process

B4C

, Ti) sample te (Al bstra (0,0,0)n su θ

B4C

sample α (0,0,0)n θ 7Li

B4C

, Ti) sample α te (Al bstra (0,0,0)n su θ 7Li

conversion point in B4C

B4C

, Ti) sample α te (Al bstra (0,0,0)n su θ 7Li detection point approximation (hit)

conversion point in B4C

Neutron scattering

detection point (hit) flat sample (0,0,0) w o d n i α w

e c 7 ideal conversion n Li

a point (geantino) in same B C volume

r 4 t

n as detection point 21 e

y y’ Entrance window coordinate system, rotated wrt to global to be perpendicular to the incoming neutrons Z Z’ Results of the simulations

● Scattering with: – diff. window thicknesses – diff. neutron wavelengths – diff. Boron thicknesses – Etc.

G. Galgoczi, K. Kanaki et al., Investigation of neutron scattering in the Multi-Blade detector with Geant4 simulations, Journal of Instrumentation (accepted, not yet published) Results of the simulations

● Scattering for: – diff. window thicknesses

B4C

α n 7 y θ Li

● Scattering for: – diff. window thicknesses – diff. neutron wavelengths

B4C

α n θ 7Li

● Scattering for: – diff. window thicknesses – diff. neutron wavelengths – diff. Boron thicknesses – etc.

B4C

α n θ 7Li

G. Galgoczi, K. Kanaki et al., Investigation of neutron scattering in the Multi-Blade detector with Geant4 simulations, Journal of Instrumentation (accepted, not yet published) Summary

● European Spallation Source (ESS) is the world's next generation spallation-based neutron source

● Challenges for neutron detectors

● Multi-Blade neutron detector

● ~ 10-4 misplaced detections due to scattering

● Effect of scattering on the window (0.5 mm) satisfies the requirements

Neutron detection

● 3He: – Price increased – Limited detection rates ● Novel technologies: – LiCaAIF6 – BF3 – 10Boron – Gadolinium