Speaker
Description
The knowledge about prompt neutrons and $\gamma$-rays spectral characteristics in nuclear fission is essential to understand the nuclear de-excitation process of fission fragments [1,2]. Preferably, these observables should be known in correlation with fragment properties like mass and kinetic energy.
Typical multi-parameter experiments require long measurement times and efficient detector systems. A particular problem for prompt-neutron spectral measurements is that usual detectors are not sensible to low neutron energies. Liquid-scintillator (LS) detectors, which allow neutron-$\gamma$ separation, exhibit low-energy thresholds for neutrons from $500~\text{keV}$ to $700~\text{keV}$. For stilbene-based detectors this threshold is about $100~\text{keV}$ lower. In order to overcome this low-energy limitation, usually combined measurements are performed. Lithium-glass ($^6\text{Li}$) detectors are employed for lower-energy neutrons. Afterwards spectra coming from LS and $\text{Li}$-glass need to be matched.
Recently, the so-called Caesium Lanthanum Lithium BromoChloride (CLLBC) detectors became available on the market. The detector material consists of a lanthanide-halide compound. Due to the presence of $^6\text{Li}$ and $\text{Cl}$, it is sensitive to $\gamma$ rays and neutrons. The pulse shape discrimination capabilities allow to distinguish between radiation types. We performed a full characterization of this type of detectors in terms of energy resolution, detection efficiency and coincidence-timing resolution using $\gamma$-rays between $80\text{keV}$ and $9\text{MeV}$. We determined the neutron response relative to the prompt-neutron spectrum from the spontaneous fission of $^{252}\text{Cf}$.
Applicability of CLLBC detectors for simultaneous measurements of prompt $\gamma$ rays and neutrons in fission will be discussed.
[1] O. Litaize et al., Eur. Phys. J. A (2015) 51:177.
[2] M. Travar, V. Piau et al., Physics Letters B 817, 136293 (2021)