We present a description of the originally developed ������-spectrometer consisting of two Si(Li)-detectors with sensitive area thickness above 8 mm and 4 ������-geometry. The full absorption spectrometer allows for direct measurements of ������-spectra, disregarding the corrections to response function induced by the electron backscattering from the crystal surface. In case of ������-spectra of transitions to the excited state of the daughter isotope additional 3 & DPRIME;BGO-detector is used in order to detect the ������-quanta in coincidence with the pair of Si(Li)-spectrometers.

Точное измерение бета-спектров всегда имело большое значение в некоторых фундаментальных физических задачах, включая физику нейтрино. В этой работе мы представляем результаты измерения спектра источника \({}^{144}\) Ce– \({}^{144}\) Pr, выполненного с помощью установок двух типов с точностью, которая была существенно увеличена по сравнению с предыдущими исследованиями. Корректность теоретической подгонки была проверена формой разрешенного бета-перехода \({}^{144}\) Pr (0 \({}^{-}\) ) \(\to{}^{144}\) Nd (1 \({}^{-}\) ).

Precise measurement of beta spectra was always of great importance in some fundamental problems, including those of neutrino physics. The results obtained by measuring the spectrum of a Ce-144-Pr-144 source with setups of two types to a precision substantially improved in relation to earlier investigations are presented. The correctness of a theoretical fit is tested using the shape of the Pr-144 (0(-)) -> Nd-144 (1(-)) allowed beta transition.

Precise measurement of beta spectra was always of great importance in some fundamental problems, including those of neutrino physics. The results obtained by measuring the spectrum of a ^144 Ce– ^144 Pr source with setups of two types to a precision substantially improved in relation to earlier investigations are presented. The correctness of a theoretical fit is tested using the shape of the ^144 Pr (0 ^- ) →^144 Nd (1 ^- ) allowed beta transition.

Deterioration of the operation parameters of Al/SiO2/p-type Si surface barrier detector upon irradiation with alpha-particles at room temperature was investigated. As a result of 40-days irradiation with a total fluence of 8*10^9 α-particles, an increase of α-peak FWHM from 70 keV to 100 keV was observed and explained by increase of the detector reverse current due to formation of a high concentration of near mid-gap defect levels. Performed CV measurements revealed the appearance of at least 6*10^12 cm-3 radiation-induced acceptors at the depths where according to the TRIM simulations the highest concentration of vacancy-interstitial pairs was created by the incoming α-particles. The studies carried out by current-DLTS technique allowed to associate the observed increase of the acceptor concentration with the near mid-gap acceptor level at EV+0.56 eV. This level can be apparently associated with V2O defects recognized previously to be responsible for the space charge sign inversion in the irradiated n-type Si detectors.

Deterioration of the operation parameters of p-type Si surface-barrier detector and Si(Li) p-i-n detector upon irradiation by alpha-particles was investigated. The detectors were irradiated at room temperature up to a total number of the registered α-particles N α equal to 6 × 10 9 . Prolonged irradiation has resulted in a deterioration of the detectors energy resolution ability and it was found that the increase of α-peaks broadening can be described by a linear function of N α with a slope Δσ/Δ N α ∼ (1.4–1.8) × 10 –9 keV/α for both detectors. Resolution deterioration was associated with the increase of the detectors leakage current, which proceeds linearly with the number of absorbed α-particles with the slope ΔI/Δ Nα ∼ (7-17) × 10 -17 A/α. The increase of the detectors reverse current was related with appearance of radiation-induced defect level at 0.56 eV above the valence band.

Precision β-spectra measurement always had a great importance in some fundamental physics problems including neutrino physics. Magnetic and electrostatic spectrometers have high resolution, but at the same time usage of such kinds of equipment involves the size and cost issues. Since electron mean free path at the energy of 3 MeV (which is basically the maximum energy of a β-transition for the long-lived nuclei) does not exceed 2 g/crn 2 , electron registration could be effectively performed with the solid state scintillators and semiconductors. A strong probability of backscattering from detector surface is present in case of semiconductor detectors and is dependent upon the detector material. Such problem can be solved with 4π geometry detector development, which fully covers the radioactive source and is able to register the backscattered electrons. In this work we present the newly developed technology of 4π geometry β-spectrometer based on two semiconductor detectors. This spectrometer was used for measurement of the 144 Ce - 144 Pr spectrum, that is the perspective anti-neutrino source due to endpoint energy at 3 MeV and can be used for the sterile neutrino search experiments. The form-factor parameters that were obtained are: C(W ) = 1 + (-0.02877 ± 0.00028)W + (-0.11722 ± 0.00297)W -1 . The measurement accuracy was sufficiently enhanced with respect to the previous results.

The shape of 210 Bi β-spectrum was measured using a spectrometer based on Si(Li) detectors with a 4π geometry. Full absorption spectrometer allows for a direct measurement of the β-spectra without using the electron backscattering corrections for the response function. The measured value of nuclear shape factor C(W)=1+(-0.4378±0.0072)W+ (0.0526±0.0021) W 2 is in agreement with the results of previous studies.

The response function of the recoil nuclei in detectors designed for detection of neutrinos or dark matter particles can be determined only through usage of a neutron source with a known energy spectrum. A possible solution for a compact neutron calibration source is a combination of a 252Cf neutron source and a semiconductor detector that detects fission fragments, and thus records the neutron emission moment. This work is devoted to the degradation study of the operating parameters for silicon semiconductor detectors irradiated by fission fragments of the nuclide of 252 Cf. Two types of Si detectors were under investigations - silicon-lithium Si(Li) p-i-n detectors and silicon surface barrier detectors. As a result of the measurements, the maximum permissible radiation doses for the correct operation of both types of detectors and the relation of the received radiation dose to the spectroscopic characteristics of the detectors were determined.

A newly developed experimental technique based on 169 Tm-containing cryogenic bolometer detector was employed in order to perform the search for solar axions. The inclusion of target material into the active detector volume allowed for significant increase in sensitivity to axion parameters. A short 6.6 days measurement campaign with 8.18 g detector crystal yielded the following limits on axion couplings: | g A γ ( g A N 0 + g A N 3 ) ≤ 1.44 × 10 − 14 GeV − 1 and | g A e ( g A N 0 + g A N 3 ) ≤ 2.81 × 10 − 16 . The achieved results demonstrate high scalability potential of presented experimental approach.

A 4π β spectrometer consists of two Si(Li) detectors with a sensitive region that is more than 8-mm thick. Using this total-absorption spectrometer it is possible to make a direct measurement of β spectra without correcting the response function for the electron backscattering from the crystal surface. The β spectra of transitions to the excited states of daughter nuclei have been measured using an additional 3'' BGO detector of γ rays, which is connected in coincidence with the pair of Si(Li) detectors.

The precision measurement of beta-spectrum shape for Bi-210 (historically RaE) has been performed with a spectrometer based on semiconductor Si(Li) detector. This first forbidden nonunique transition has the transition form factor strongly deviated from unity, and knowledge of its spectrum would play an important role in low-background physics in the presence of Pb-210 background. The measured transition formfactor could be approximated as C(W ) = 1 + (-0.4470 +/- 0.0013)W + (0.0552 +/- 0.0004)W-2, that is in good agreement with previous studies and has significantly increased parameter precision.

A spectrometer based on a Si(Li) detector has been tested by exposure to α particles with the aim of determining changes in the detector characteristics versus the fluence. As a result of 60-day measurements with a total fluence of 6.2 × 109 α particles, it has been established that the dependence of the deterioration in the energy resolution of α-particle peaks on the fluence is described by a linear function with a slope of Δσ/ΔФ = (8.4 ± 0.4) × 10–10 keV/α. The measured amplitude of the α-particle momentum decreases linearly with increasing fluence with a slope of (–4.8 ± 0.6) × 10–9 keV/α. These effects do not prevent reliable discrimination between the signals from α particles and fission fragments until the fluence reaches a value of 1010 α particles when the Si(Li) detector is a part of a neutron source for detecting fission fragments.

AbstractA search for resonant absorption of solar axions by $$^{169}\mathrm {Tm}$$169Tm nuclei was carried out. A newly developed approach involving low-background cryogenic bolometer based on $$\mathrm {Tm}_{3} \mathrm {Al}_{5} \mathrm {O}_{12}$$Tm3Al5O12 crystal was used that allowed for significant improvement of sensitivity in comparison with previous $$^{169}\mathrm {Tm}$$169Tm based experiments. The measurements performed with 8.18 g crystal during 6.6 days exposure yielded the following limits on axion couplings: $$|g_{A\gamma } (g_{AN}^0 + g_{AN}^3) \le 1.44 \times 10^{-14}\,{{\mathrm{GeV}}^{-1}}$$|gAγ(gAN0+gAN3)≤1.44×10-14GeV-1 and $$|g_{Ae} (g_{AN}^0 + g_{AN}^3) \le 2.81 \times 10^{-16}$$|gAe(gAN0+gAN3)≤2.81×10-16.

Precision measurements of beta-spectra have always been and are still playing an important role in several fundamental physical problems, predominantly in neutrino physics. Magnetic and electrostatic spectrometers possess the superior energy resolution, but at the same time such devices appear to be very complex and large-scale setups. Since the electron free path at 3 MeV (which is, basically, the maximum beta-transition energy for long-living isotopes) does not exceed 2 g/cm(3), solid state scintillation and ionization detectors were effectively employed for detection of electron. In case of semiconductor detectors there is a significant probability of back-scattering from the detector surface that depends on the detector material. This issue could be overcome by constructing a beta-spectrometer with 4 pi geometry, fully covering the source and capable of detecting backscattered electrons. Here we present a technology allowing production of a beta-spectrometer based on silicon detectors and having 4 pi geometry. The spectrometer developed had been fitted with a Ce-144-Pr-144 radioactive source and has demonstrated capability of performing precision beta-spectrometry for this nuclides.