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Feasibility demonstration of continuous signal-based neutron noise measurements by experiments and simulations
Authors:
Máté István Boros,
Máté Szieberth,
Gergely Klujber,
Imre Pázsit,
István Barth,
Yasunori Kitamura,
Tsuyoshi Misawa
Abstract:
Neutron noise methods are used to determine kinetic parameters such as the prompt neutron decay constant, but traditional pulse-counting suffers from dead-time and pile-up at high detection rates. Recent theory shows that analysing the continuous detector current can avoid these limitations if pulse-shape effects are properly treated. This work presents a feasibility study of continuous-signal neu…
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Neutron noise methods are used to determine kinetic parameters such as the prompt neutron decay constant, but traditional pulse-counting suffers from dead-time and pile-up at high detection rates. Recent theory shows that analysing the continuous detector current can avoid these limitations if pulse-shape effects are properly treated. This work presents a feasibility study of continuous-signal neutron noise analysis based on simulations and experiments performed at two research reactors. The stochastic model of the detector current is applied to derive Rossi- and Feynman-type formulations, and pulse-shape distortions are mitigated using detector pairs or by deconvolving the average pulse-shape through inverse Fourier and Wiener filtering. Simulations demonstrate accurate $α$-parameter estimation at count rates where pulse-counting becomes unusable, and enable evaluation of significantly higher $α$ values. Measurements at KUCA and BME TR confirm that continuous and deconvolved signals provide unbiased results despite dead-time and electronic artifacts, establishing the method as a practical alternative for high-rate reactor noise diagnostics.
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Submitted 9 June, 2026;
originally announced June 2026.
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Ultrahigh nitrogen-vacancy center concentration in diamond
Authors:
S. Kollarics,
F. Simon,
A. Bojtor,
K. Koltai,
G. Klujber,
M. Szieberth,
B. G. Márkus,
D. Beke,
K. Kamarás,
A. Gali,
D. Amirari,
R. Berry,
S. Boucher,
D. Gavryushkin,
G. Jeschke,
J. P. Cleveland,
S. Takahashi,
P. Szirmai,
L. Forró,
E. Emmanouilidou,
R. Singh,
K. Holczer
Abstract:
High concentration of negatively charged nitrogen-vacancy ($\text{NV}^{-}$) centers was created in diamond single crystals containing approximately 100 ppm nitrogen using electron and neutron irradiation and subsequent thermal annealing in a stepwise manner. Continuous wave electron paramagnetic resonance (EPR) was used to determine the transformation efficiency from isolated N atoms to…
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High concentration of negatively charged nitrogen-vacancy ($\text{NV}^{-}$) centers was created in diamond single crystals containing approximately 100 ppm nitrogen using electron and neutron irradiation and subsequent thermal annealing in a stepwise manner. Continuous wave electron paramagnetic resonance (EPR) was used to determine the transformation efficiency from isolated N atoms to $\text{NV}^{-}$ centers in each production step and its highest value was as high as 17.5 %. Charged vacancies are formed after electron irradiation as shown by EPR spectra, but the thermal annealing restores the sample quality as the defect signal diminishes. We find that about 25 % of the vacancies form NVs during the annealing process. The large $\text{NV}^{-}$ concentration allows to observe orientation dependent spin-relaxation times and also the determination of the hyperfine and quadrupole coupling constants with high precision using electron spin echo (ESE) and electron-nuclear double resonance (ENDOR). We also observed the EPR signal associated with the so-called W16 centers, whose spectroscopic properties might imply a nitrogen dimer-vacancy center for its origin.
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Submitted 10 December, 2021; v1 submitted 5 October, 2021;
originally announced October 2021.
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Optical-microwave pump-probe studies of electronic properties in novel materials
Authors:
S. Kollarics,
A. Bojtor,
K. Koltai,
B. G. Márkus,
K. Holczer,
J. Volk,
G. Klujber,
M. Szieberth,
F. Simon
Abstract:
Combined microwave-optical pump-probe methods are emerging to study the quantum state of spin qubit centers and the charge dynamics in semiconductors. A major hindrance is the limited bandwidth of microwave irradiation/detection circuitry which could be overcome with the use of broadband coplanar waveguides (CPW). We present the development and performance characterization of two spectrometers: an…
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Combined microwave-optical pump-probe methods are emerging to study the quantum state of spin qubit centers and the charge dynamics in semiconductors. A major hindrance is the limited bandwidth of microwave irradiation/detection circuitry which could be overcome with the use of broadband coplanar waveguides (CPW). We present the development and performance characterization of two spectrometers: an optically detected magnetic resonance spectrometer (ODMR) and a microwave detected photoconductivity measurement. In the first method light serves as detection and microwaves excite the investigated medium, while in the second the roles are interchanged. The performance is demonstrated by measuring ODMR maps on the nitrogen-vacancy center in diamond and time resolved photoconductivity in p-doped silicon. The results demonstrate both an efficient coupling of the microwave irradiation to the samples as well as an excellent sensitivity for minute changes in sample conductivity.
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Submitted 1 October, 2020;
originally announced October 2020.