Characterization of thermal neutron beam monitors

Neutron beam monitors with a wide range of efficiencies, low $\gamma$ sensitivity, and high time and space resolution are required in neutron beam experiments to continuously diagnose the delivered beam. In this work, commercially available neutron beam monitors have been characterized using the R2D2 beamline at IFE (Norway) and using a Be-based neutron source. For the $\gamma$ sensitivity measurements different $\gamma$ sources have been used. The evaluation of the monitors includes, the study of their efficiency, attenuation, scattering, and sensitivity to $\gamma$. In this work we report the results of this characterization.

Figure 1

Photographs and diagrams of the neutron beam monitors tested in this work: (a) MWPC from ORDELA, (b) MWPC from Mirrotron-0D, (c) MWPC from Mirrotron-2D, (d) 2D-GEM from CDT, e) scintillator from Quantum Detectors UK, (f) fission chamber from LND.

Figure 2

The setup used for thermal neutron detection at R2D2 beam line at IFE-Norway.

Figure 3

Setup used at R2D2 beam for efficiency and attenuation measurements.

Figure 4

Pulse height spectra measured by the Mirrotron monitor using a neutron source and using three $\gamma$ sources separately (${}^{60}\mathrm{Co}$, ${}^{57}\mathrm{Co}$, ${}^{133}\mathrm{Ba}$).

Figure 5

Pulse height spectra measured by the Mirrotron-2D monitor using a neutron source and using three $\gamma$ sources separately (${}^{60}\mathrm{Co}$, ${}^{57}\mathrm{Co}$, ${}^{133}\mathrm{Ba}$).

Figure 6

Pulse height spectra measured by the ORDELA-He monitor using a neutron source and using three $\gamma$ sources separately (${}^{60}\mathrm{Co}$, ${}^{57}\mathrm{Co}$, ${}^{133}\mathrm{Ba}$).

Figure 7

Pulse height spectra measured by the ORDELA-N monitor using a neutron source and using three $\gamma$ sources separately (${}^{60}\mathrm{Co}$, ${}^{57}\mathrm{Co}$, ${}^{133}\mathrm{Ba}$).

Figure 8

Pulse height spectra measured by the scintillator monitor using a neutron source and using three $\gamma$ sources separately (${}^{60}\mathrm{Co}$, ${}^{57}\mathrm{Co}$, ${}^{133}\mathrm{Ba}$).

Figure 9

Pulse height spectra measured by the LND fission chamber using a neutron source and using ${}^{60}\mathrm{Co}$.

Figure 10

Pulse height spectra measured by the Mirrotron monitor using ${}^{60}\mathrm{Co}$ at three distances.

Figure 11

$\gamma$ and neutron counts using ${}^{60}\mathrm{Co}$ and Be-based neutron sources respectively. These counts are collected in 10 min as a function of the set threshold level which represents the energy (MeV) in the PHS.

Figure 12

Pulse height spectra measured by the ORDELA-He monitor using neutron beam line at 2.4 Å.

Figure 13

Pulse height spectra measured by the ORDELA-N monitor using neutron beam line at 2.4 Å.

Figure 14

Pulse height spectra measured by the Mirrotron monitor using neutron beam line at 2.4 Å.

Figure 15

Pulse height spectra measured by the Mirrotron-2D monitor using neutron beam line at 2.4 Å.

Figure 16

Schematic presentation showing the setup used for measuring transmission and scattering of neutrons, the detector used for transmission is a ${}^3\mathrm{He}$-tube and a ${}^6\mathrm{Li}$-glass scintillator from SCIONIX is used for measuring scattering.

Figure 17

Neutron counts measured by different monitors versus the variation in the incident neutron flux. Counts from ORDELA-N and Mirrotron-2D monitors were multiplied by a factor of 100 and 10, respectively.

Figure 18

Two-dimensional image measured by GEM monitor at R2D2 at IFE using a neutron beam size of $1\times 1{\mathrm{mm}}^2$ at 2.4 Å. The white strip is a dead electronics channel. One pixel size is 3.12 mm.

Figure 19

Two-dimensional image measured by Mirrotron-2D at R2D2 at IFE using a neutron beam size of $1\times 1{\mathrm{mm}}^2$ at 2.4 Å. The pixel size is $1\mathrm{mm}\times 1\mathrm{mm}$.