This work investigates gamma-rays induced radiation damage effect in LaBr3:Ce and CeBr3 crystals. Optical and scintillation properties of these crystals were characterized before and after irradiation up to 2 x 10(6) rad. The recovery of radiation damage was observed in both crystals. After the crystals were irradiated at various dose rates, it was confirmed that the radiation damage saturation cannot be attributed to the dose rate dependent effect. After the irradiation up to 2 x 10(6) rad, the loss of emission-weighted longitudinal transmittance (EWLT) values is approximately 4.7% for LaBr3:Ce and 6.0% for CeBr3. Meanwhile, the light yield (LY) loss of LaBr3:Ce and CeBr3 crystals is approximately 12.3% and 11.6%, respectively. The excellent correlation between EWLT loss and LY loss indicates that the LY degradation in both crystals can be mainly attributed to the loss of transmittance. The deterioration of energy resolution (ER) after 2-Mrad irradiation ranges from 5.1% to 6.7% for LaBr3:Ce and from 8.7% to 9.5% for CeBr3. The decay time is not affected by radiation damage. Compared with other scintillation crystals, LaBr3:Ce and CeBr3 crystals are radiation hard. These findings provide important insights into the behavior of these materials working in severe radiation environments, which is essential for their applications and production.

Measuring the reaction history of low-flux-density pulsed radiation fields has always been challenging because of the limitations of traditional counting methods and current methods. An array counting method based on lanthanide bromide concise scintillation detectors is proposed as a solution to overcome this challenge. This paper discusses the physical designs for implementing the method, as well as the well-designed pulse pile-up decomposition algorithm used to decompose the overlapped waveforms. The algorithm uses a pulse function template trained on many single-particle pulses collected at a low count rate, allowing for shortening the time interval for decomposable pulse pile-up to 8 ns. To experimentally validate the effectiveness of the method, an array counting detection system comprising 48 lanthanum bromide detection units is constructed, and a pulse verification experiment is conducted. These array units are employed to obtain single-particle pulse samples with a low probability of pulse pile-up. The waveforms output by these units are digitally sampled and subsequently analyzed using the pulse pile-up decomposition algorithm to extract the timestamp of individual radiation events. The experimental results demonstrate that the reaction history information obtained by the array counting system, which is positioned at a distance, is largely consistent with that obtained by a current-type detector placed in close proximity. Furthermore, the number distribution of single-particle events across the different array units followed a Poisson distribution, aligning with theoretical expectations. These results confirm the effectiveness of the method in capturing reaction history information in a low-flux-density pulsed radiation field.

Vacuum Compton detector (VCD) is a type of pulsed gamma/X-ray radiation detector with a fast response time (< 1 ns) and an upper limit for ultrahigh gamma/X-ray intensity detection. VCDs are widely used to measure the time behaviors of various pulsed X-ray generators. However, recent studies have found that the output signal of the detector is superimposed with strong interference signals under the condition of fast-pulse irradiation (full width at half maximum of nearly 1 ns), which negatively impacts the pulse responses of VCDs. In this study, a pulse response model for VCDs is established, and the pulse response characteristics of the VCDs under gamma/X-ray incidence conditions with different pulse durations are studied. The results show that the interferences with the detector output signal come from two aspects under the condition of half width 0.1 ns pulse radiation. One is mainly from the signal reflection caused by the impedance mismatch of the emitter, and the other is from electromagnetic oscillations that form inside the detector and cause strong interference with the output signals of the detector. In the case of a pulse input condition with a half width of 0.5 ns, the interferences with the detector mainly come from the signal reflection caused by the impedance mismatch of the emitter. When the half width of the pulse is 25 ns, the output signals are almost unaffected. This work provides an efficient and accurate method for researching the pulse response characteristics of VCDs and serves as a reference for the impulse response characterization of other types of charge collection detectors.

Generally, the light output (LO) of scintillators decreases after the gamma-ray irradiation. However, the LO enhancement is observed in CsPbCl3 crystals after gamma-rays irradiation at doses of 102, 103, 104 and 105 rad. A new luminescence band around 580 nm with a decay time of 12 mu s is observed after the irradiation. Its intensity depends on the integrated dose of irradiation. A positive correlation between its intensity and LO is observed, illustrating the LO enhancement can be attributed to the new luminescence band. The absorption wavelength of radiation induced color centers at 2.84 eV is consistent with the excitation wavelength of the new luminescence band. There is a positive correlation between the concentration of color centers at 2.84 eV and the intensity of the new luminescence band. It indicates the new luminescence band is attributed to the luminescence of radiation induced color centers. Considering the high mobility of Cl-ions in the CsPbCl3 crystal, it is speculated the radiation induced color centers may be vacancies of Cl- ions. The intensity of the new luminescence band decreases with time, which is attributed to the annihilation of radiation induced color centers at room temperature. The study provides valuable insights into the performance of CsPbCl3 crystal under high irradiation. It also explains the abnormal LO enhancement in CsPbCl3 crystals after gamma-ray irradiations, which may be useful to understand the defects of inorganic halide perovskite crystals.

Recent developments in the field of ultra-high intensity gamma sources have led to a renewed interest in detection of pulsed gamma radiation. This paper thus proposed a scintillation detector system based on scattered gamma rays by using the tungsten target. System design parameters were investigated with Monte Carlo simulation and verified by 60Co/137Cs radiation experiments. The results showed that the system can raise the upper limit of gamma intensity detection by 4–5 orders. Signal-to-noise ratio of the system was studied in the 60Co radiation experiments. These findings suggested that this system is a suitable alternative for future needs for ultra-intense gamma-ray measurements.

A major method to obtain the characteristic information about equipment with transient pulse radiation is to detect the gamma rays released from the equipment. To explore the performances of the equipment, sophisticated diagnostic techniques and detecting systems have been developed and established. The detecting system serves as the main instrumentation for gathering details about radiation fields. It also serves as the technological basis for carrying out intense pulsed radiation detection, and its performance directly influences the selection of the measurement technique and the quality of the measured data. The detection principle, detector technology, and development situation of intense pulsed gamma rays are discussed in this study.

The energy thresholding characteristic of carbon dioxide (CO 2 ) Cherenkov gas is significant for the detection of fusion $\gamma $ -rays. In this article, the energy thresholding characteristic of CO 2 (at 300 K and 4.02 atm.) gas is experimentally calibrated by a pulse electron beam with picosecond duration time and adjustable energies. Three mirrors with the ultraviolet reflectivity are used to make an off-axis light collection system. For electron energy of 10 MeV (above the Cherenkov threshold energy), the collected pulse photon spectrum has good agreement with the theoretical spectrum of Cherenkov radiation, confirming that Cherenkov radiation dominates collected photons than non-Cherenkov sources. The threshold energy resolution (12/7.5 MeV) is improved to ~10 4 , an order higher than the reported value of ~10 3 . The improvement on the threshold energy resolution of CO 2 gas is mainly attributed to the ultraviolet mirrors, suppressing lights with a wavelength higher than 280 nm. This work can provide significant support for the further application of the Cherenkov detector in the fusion $\gamma $ -ray diagnosis.

Y3Al5O12:Yb (YAG:Yb) crystal has been applied as not only the laser crystal with infrared (IR) luminescence but also the fast scintillation crystal with the fast ultraviolet (UV) scintillation light. In the investigation, both the X-ray excited luminescence (XEL) and cathodoluminescence (CL) spectra of YAG:Yb crystals with various Yb concentrations were measured and compared. Generally, the CL spectrum is considered to be equivalent to the XEL spectrum in characterizing the luminescence of scintillation crystals. However, the inconsistent correlations between Yb concentrations and the spectrally integrated XEL, CL intensities were observed for the UV luminescence. Meanwhile the consistent correlations between Yb concentrations and the spectrally integrated XEL, CL intensities were observed for the IR luminescence. The phenomenon was attributed to the stronger self-absorption effect in the XEL spectra measurements, compared to the CL spectra measurement. It indicates the correction on the luminescence intensity is needed in comparing the integrated XEL intensity of scintillation crystal with self-absorption effect.

Due to its ultrafast cross-luminescence, the BaF 2 crystals with a subnanosecond decay time are promising for high-reputation radiation detection. However, there is a slow scintillation component with a decay time of about 600 ns in the crystal, which induces a pile-up effect. The Y doping in the crystal was confirmed to be effective in slow component suppression. In this investigation, the fast/total (F/T) light yield (LY) ratios and fast component LY of BaF 2 :Y crystals with various Y concentrations were investigated by the fast sampling technique. It was demonstrated that Y doping not only suppresses the slow component but also weakens the fast component. A good negative correlation was observed between the F/T LY ratios and fast component LY of BaF 2 :Y crystals, indicating that it was impossible to obtain the BaF 2 :Y crystal with a high F/T LY ratio and a high fast component LY at the same time. The influence of wrapping materials on the F/T LY ratio was also investigated. The result illustrates that both the undoped and Y-doped BaF 2 crystals without wrapping materials show the best F/T LY ratio, indicating that the tradeoff between LY and F/T LY ratio is needed in the applications.

As an ultrafast inorganic scintillator, Yb-doped Y3Al5O12 [yttrium aluminum garnet (YAG)] crystals have potential applications in various fields, such as ultrafast radiation detection, solar neutrino detection, pulsed radiation imaging, and nuclear reaction kinetics diagnosis. In this work, the fluence rate effect of pulsed γ rays on the Yb:YAG scintillation crystal was investigated at the "QiangGuang-I" facility. The experiment results show that the fluence rate linear response upper limit of the Yb:YAG crystal is about 9.1 × 1018 MeV cm-2 s-1. The Yb:YAG crystal changed from colorless to yellow, and the relative light output decreased to 63% of its initial value after the irradiations, which were attributed to the radiation induced damage. It is deduced that oxygen vacancies and divalent Yb cations were generated after the irradiations.

The Doppler broadening of gamma rays occurs in the fast neutron analysis with photons emitted in inelastic scattering reactions on certain nuclei, such as 12C and 14N. In this paper, we developed an algorithm based on the Monte Carlo method to calculate the Doppler broadened gamma peak shape of the 4.438 MeV gamma ray emitted by 12C in graphite when exposed to fast neutrons of different energies. The SAND-II unfolding iterative method is applied to obtain the spectrum of the incident neutron beam by using the Doppler broadened gamma spectra. In the calculation example, the unfolded neutron spectrum shows reasonable agreements with the original incident neutron spectrum.

The temporal response of CdZnTe (CZT) detector to $\gamma $ -ray is experimentally studied in this article. Infrared (IR) illumination is utilized to improve the performance of CZT detector. The results show that with no IR illumination operated on the CZT detector, the output signal of the CZT detector appears as a short overshoot process (sharp peak) at the beginning of stable $\gamma $ -ray irradiation. After the sharp peak, a decay process follows, and finally, a stable output of CZT detector is achieved. IR illumination can eliminate the instability of CZT detector under $\gamma $ -ray irradiation, such as the output overshoot of detector (sharp peak) during the transition state. With the increase of IR illumination intensity, the sharp peak disappears gradually and the temporal response of CZT detector follows the intensity of $\gamma $ -ray irradiation without transition state. The fitting time constant of the sharp peak is in good consistency with the typical detrapping lifetime on the order of seconds. The stable current of CZT $\gamma $ -ray detector can be improved by 8.2% due to IR illumination, which can also be explained by the prefilling effects of IR illumination on the defect level. The sharp peak in the temporal response of CZT detector is probably caused by the deep level, related to the Te antisite-related deep donors. The current uncertainty of CZT $\gamma $ -ray detector under IR illumination is smaller than 1.4%, which is small enough to be ignored. The flux rate response of CZT detector can also be improved by IR illumination. This study will provide significant supports for the further application of CZT material in radiation measurements.

In this paper, the effects of dose and dose rate on the light output of LaBr3:Ce scintillator are studied in detail. The relative light output of the crystal is measured in real time by measuring the photoelectric current of the detector during irradiation at a 137Cs irradiation facility. It is found that the light output of the LaBr3:Ce scintillator continues to decrease with the increase in dose. Permanent radiation damage in LaBr3:Ce is also observed at a cumulative dose of 100kGy.

In the past two decades cooperating with Frank Laboratory of Neutron Physics (FLNP), Joint Institute for Nuclear Research (JINR) measurements of (n, α ) reaction cross sections for 6 Li, 10 B, 25 Mg, 39 K, 40 Ca, 54,56,57 Fe, 58 Ni, 63 Cu, 64,67 Zn, 95 Mo, 143 Nd and 147,149 Sm nuclei were performed in the MeV neutron energy region based on the 4.5 MV Van de Graaff accelerator at Peking University. In recent years, our measurements were extended in three aspects. Firstly, measurements were expanded from two-body reactions to three-body reactions such as 10 B (n, t2 α ). Secondly, the neutron energy region was extended from below 8 MeV to 8 - 11 MeV by using the HI-13 tandem accelerator of China Institute of Atomic Energy (CIAE), with which cross sections of 54,56 Fe(n, α ) 53,51 Cr reactions were measured. Thirdly, based on the newly-built China Spallation Neutron Source (CSNS) Back-n WNS (White Neutron Source), differential and angle-integrated cross sections for 6 Li(n, t) and 10 B(n, α ) reactions were measured in the neutron energy region from 1 eV to 3 MeV.

The abundances of the nuclides in nuclear materials change over time in reactors because of neutron-induced reactions like (n, gamma), (n, alpha), (n, p), etc. Among them, the effect caused by (n, gamma) reactions is especially significant in heavy water reactors because they have a large proportion of thermal neutron flux, and the cross sections of (n,.) reactions for most nuclides are dominant in the thermal region than in regions of higher energies. The changes of the abundances of Fe, Ni, and Zr isotopes in CANDU-6 reactors over 25 years through radiative capture reactions (thermal neutron flux of 2.7 x 10(18) n.m(-2).s(-1), and effects of epithermal, resonance, and fast neutrons are also included) are calculated. Results show that for Fe and Ni isotopes, the changes of abundances are obvious: Fe-57 enriches from 2.12% to 12.22%; Ni-58 drops from 68.09% to 36.88% and Ni-60 increases from 26.23% to 44.35%. For Zr isotopes, the effect is also noticeable, with the abundance of Zr-90 and Zr-91 decreasing from 51.45% and 11.22% to 50.67% and 9.58%, respectively.. Present results are verified with the ALARA code. Based on these calculations, a new approach to estimating the neutron fluence in heavy water reactors is proposed according to the abundances of several stable isotopes including Fe-56, Fe-57, Ni-58 and Ni-60.

A Monte Carlo simulation of the energy spectrum of the α particles emitted from a 238U3O8 sample is performed. Through comparing the simulated and measured energy spectra of the α particles, the non-uniformity of the 238U3O8 sample is obtained, and then the number of 238U target nuclei is determined. Using the obtained non-uniformity, a Monte Carlo simulation is developed to simulate the energy spectrum of neutron induced fission fragments. The simulated and measured energy spectra of neutron induced fission fragments agree well with each other.

$^{56,54}\mathrm{Fe}(n,\ensuremath{\alpha})^{53,51}\mathrm{Cr}$ cross sections were measured in the neutron energy region of 5--11 MeV using three neutron sources based on accelerators, a twin gridded ionization chamber, and highly enriched $^{56}\mathrm{Fe}$ and $^{54}\mathrm{Fe}$ foil samples. The $^{238}\mathrm{U}(n,f)$ reaction was used to monitor the neutron fluence, and the interferences from the low-energy neutrons were corrected according to the neutron energy spectra obtained through unfolding the pulse height spectra measured by a liquid scintillator. Both the measured cross sections show a ``shoulder'' structure in the 8--11 MeV region which may be caused by the level structure of the residual nuclei. The present paper aims to improve constraint of the $^{56,54}\mathrm{Fe}(n,\ensuremath{\alpha})^{53,51}\mathrm{Cr}$ excitation functions in the MeV region where their neutron energy dependences are significant, while related measurements are nonexistent or scarce and the deviations among existing measurements and evaluations are significant. To obtain more precise excitation functions of the $^{56,54}\mathrm{Fe}(n,\ensuremath{\alpha})^{53,51}\mathrm{Cr}$ reactions, further measurements and improved evaluations are required.

Fe-56,Fe-54 (n, alpha)Cr-53,Cr-51 cross sections were measured in the neutron energy region of 5-11 MeV using three neutron sources based on accelerators, a twin gridded ionization chamber, and highly enriched Fe-56 and Fe-54 foil samples. The U-238(n, f) reaction was used to monitor the neutron fluence, and the interferences from the low-energy neutrons were corrected according to the neutron energy spectra obtained through unfolding the pulse height spectra measured by a liquid scintillator. Both the measured cross sections show a "shoulder" structure in the 8-11 MeV region which may be caused by the level structure of the residual nuclei. The present paper aims to improve constraint of the Fe-56,Fe-54(n, alpha)Cr-53,Cr-51 excitation functions in the MeV region where their neutron energy dependences are significant, while related measurements are nonexistent or scarce and the deviations among existing measurements and evaluations are significant. To obtain more precise excitation functions of the Fe-56,Fe-54(n, alpha) Cr-53,Cr-51 reactions, further measurements and improved evaluations are required.