Internal bremsstrahlung accompanying non-unique second-forbidden β-decay of 36Cl

The internal bremsstrahlung spectrum accompanying the non-unique second-forbidden β-decay of ³⁶Cl is measured using the magnetic deflection technique. The true IB spectrum is obtained with the help of the inverse of the detector response matrix. The experimental data in the energy interval 80 to 700 keV are compared with the theoretical spectra of Knipp and Uhlenbeck, and Bloch, Lewis and Ford, and Chang and Falkoff. The agreement between the measurement and theory is not good throughout the energy region of the present investigation, though the experimental points are close to the second-forbidden scalar theory of Chang and Falkoff.     

Internal Bremsstrahlung from14C and36Cl

The Internal Bremsstrahlung (IB) spectra emitted in the beta decays of¹⁴C and³⁶Cl are measured with a HPGe detector and a multichannel analyser along with a standard geometrical set up. The experimental results are compared with the corresponding theoretical distributions due to Knipp and Uhlenbeck and Bloch (KUB), Lewis and Ford, Nilsson and also due to Chang and Falkoff. The total IB yields of intensity and of energy from each of the isotopes in the investigated energy regions are also determined and compared with the corresponding theoretical values. The present results of IB from¹⁴C are found to be in excess over all the corresponding theoretical distributions throughout the investigated photon energy region from 60 keV to 130 keV. It may also be pointed out that the IB from this isotope has not been studied earlier and as such the results in this case are considered new and important. In the case of³⁶Cl the experimental results are found to be above KUB theory but corresponding closely to the theory of Chang and Falkoff, except below 150 keV where there is experimental excess over theory.     

Unfolding the fast neutron spectra of a BC501A liquid scintillation detector using GRAVEL method

Accurate knowledge of the neutron energy spectra is useful in basic research and applications. The overall procedure of measuring and unfolding the fast neutron energy spectra with BC501A liquid scintillation detector is described. The recoil proton spectrum of 241Am-Be neutrons was obtained experimentally. With the NRESP7 code, the response matrix of detector was simulated. Combining the recoil proton spectrum and response matrix, the unfolding of neutron spectra was performed by GRAVEL iterative algorithm. A MatLab program based on the GRAVEL method was developed. The continuous neutron spectrum of ²⁴¹Am-Be source and monoenergetic neutron spectrum of D-T source have been unfolded successfully and are in good agreement with their standard reference spectra. The unfolded ²⁴¹Am-Be spectrum are more accurate than the spectra unfolded by artificial neural networks in recent years.     

瞬时响应的粒子探测器模型

本文中将Unruh-DeWitt型粒子探测器改造成瞬时响应的粒子探测器。经过改进之后,所有理想的探测器应是等价的,尽管它们对同一物理状态的响应可能不一样。本文给出一个可行的方法用以计算在Minkowski真空中作任意运动的探测器的响应函数。 关键词：     

Simulation of the xenon gamma spectrometer for analyzing radioactive materials

The results of the calculation of the detection efficiency of gamma-rays for the xenon gamma spectrometer (XGS) obtained using the GEANT4 Monte Carlo simulation are presented. The gamma spectra of the set of basic standard gamma-sources (OSGI) are analyzed for a real detector, and the calculated and actual detection efficiencies are compared. The XGS spectra are analyzed to determine the minimum concentration of the ¹⁵²Eu radio nuclide in the ¹³⁷Cs and ⁶⁰Co mixture. It is shown that the xenon gamma spectrometer is capable of detecting the isotope at concentrations above 40% in the mixture.     

Statistical distribution based detector response function ofSi (PIN) detector for Kα and Kβ X-ray

A semi-empirical detector response function (DRF) model of Si (PIN) detector is proposed to fit element K_α and K_β X-ray spectra, which is based on statistical distribution analytic (SDA) method. The model for each single peak contains a step function, a Gaussian function and an exponential tail function. Parameters in the model are obtained by weighted nonlinear least-squares fitting method. In the application, six kinds of elements' characteristic X-ray spectra are obtained by Si (PIN) detector, and fitted out by the established DRF model. Reduced chi-square values are at the interval of 1.11-1.25. Other applications of the method are also discussed.     

Synchrotron applications of an amorphous silicon flat‐panel detector

A GE Revolution 41RT flat‐panel detector (GE 41RT) from GE Healthcare (GE) has been in operation at the Advanced Photon Source for over two years. The detector has an active area of 41 cm × 41 cm with 200 µm × 200 µm pixel size. The nominal working photon energy is around 80 keV. The physical set‐up and utility software of the detector system are discussed in this article. The linearity of the detector response was measured at 80.7 keV. The memory effect of the detector element, called lag, was also measured at different exposure times and gain settings. The modulation transfer function was measured in terms of the line‐spread function using a 25 µm × 1 cm tungsten slit. The background (dark) signal, the signal that the detector will carry without exposure to X‐rays, was measured at three different gain settings and with exposure times of 1 ms to 15 s. The radial geometric flatness of the sensor panel was measured using the diffraction pattern from a CeO₂ powder standard. The large active area and fast data‐capturing rate, i.e. 8 frames s^?1 in radiography mode, 30 frames s^?1 in fluoroscopy mode, make the GE 41RT one of a kind and very versatile in synchrotron diffraction. The loading behavior of a Cu/Nb multilayer material is used to demonstrate the use of the detector in a strain–stress experiment. Data from the measurement of various samples, amorphous SiO₂ in particular, are presented to show the detector effectiveness in pair distribution function measurements.     

Response function of the CdZnTe SPEAR detector

The response function of the SPEAR CdZnTe detector developed by eV Microelectronics was studied in detail. This compact detector includes a CdZnTe crystal and a preamplifier. It is operational at room temperature. The energy range of the detector is between 10 keV and 1 MeV, and its relative resolution is less than 4% at 122 keV. The goal of our study was to establish an empirical analytical approximation of the response function to be used in Monte Carlo simulations (e.g. for spectrum unfolding). Various radionuclides were used for the study. The energy spectrum obtained from the detector not only showed smooth peaks but also had a tail on the low‐energy side of the peak. This tail part was more prominent at higher energies. By using the experimental spectrum for various nuclides such as ²⁴¹Am, ¹⁰⁹Cd, ⁵⁷Co and ¹³⁷Cs, the parameters required to replicate the experimental response with a peak plus exponential model were evaluated. Copyright © 2011 John Wiley & Sons, Ltd.     

Precise measurement of 14C beta spectrum by using a wall-less proportional counter

The technique and results of a precise measurement of the ¹⁴C beta spectrum in the energy range 10–160 keV by using a wall-less proportional counter are presented. The results of analysis and the inclusion of possible factors that distort the spectrum in the calculation of the detector response function are reported. Considerable deviations from the distribution expected for an allowed transition are found.     

Measurement of the beta spectrum of the 0− (120 keV) state of16N

We have measured the beta spectrum of the 0^?(120 keV,t _1/2=5.25 μs) state of¹⁶N. The response function of our detector has been measured, parameterized and then fitted to known spectral shapes taken under conditions close to those in the actual experiment. Using this response function and subtracting a 56 μs half-life background due to neutron capture in the detector, the measured 0^? spectrum compares well with the allowed shape for the 0^?→0⁺ spectrum plus a small contribution from the allowed 0^?→1^? transition.     

Investigation of the n+-p-π-p+ structure of silicon avalanche diodes by charged particles

+ -p-π-p⁺ silicon avalanche diodes for the detection of heavy charged particles. Two sets of measurements of the alpha spectrum of ²⁴¹Am were carried out, one without a collimator and one with a collimator. The obtained alpha spectra for all bias voltages differ substantially from the spectrum obtained with a conventional semiconductor detector. The experiments clarified the amplification mechanism of the type n⁺-p-π-p⁺ silicon avalanche detector for charged particles. We demonstrated that the reasons for the unconventional alpha spectra are the mechanisms of internal amplification and also the specific detector design. Received: 14 July 1997/Accepted: 12 January 1998     

An intercomparison of indoor radon data using NTD and different dynamic recording systems

Indoor radon data monitored with several different recording systems in a controlled cellar were analyzed. The one-room cellar is carved into volcanic rock and presents an almost constant radon emanation throughout the year. Measurements were performed using the AlphaGUARD^®, Sun Nuclear^® 1027, DOSEman^® and RAD7^® radon monitors, and CR-39 Lantrack^® in a passive integrating detector. The radon concentrations measured by the active detection systems and averaged over the three-month measurement period ranged from 533 to 805 Bq m⁻³. The response of the passive detector system was a linear function for exposure times of one, two and three months. The data are discussed as a function of changes in the distribution of radon within the cellar and the response characteristics of the detection devices.     

Internal bremsstrahlung in the electron capture decay of 145Sm

Internal bremsstrahlung (IB) emitted in the non-unique first-forbidden electron capture decay of the $\text{7}\text{2}{}^{\mathrm{?}}$ ground state of ¹⁴⁵Sm to the $\text{7}\text{2}{}^{\mathrm{+}}\text{61}\text{keV}$ first excited level of ¹⁴⁵Pm has been studied. The total IB spectrum and the IB spectrum for captures proceeding via the 1s shell were measured for photons in the energy range of 100–580 keV and the spectra were normalized to the non-radiative capture rate. The experimental data agree with theoretical predictions.     

Program for the analysis of pulse height spectra and the background from a proportional detector

A PC-Fortran program is presented for fitting of lineshapes and the analysis of pulse height spectra obtainable with proportional detectors. The common fitting and analysis of pulse height spectra by means of mixed Gaussian lineshapes is readily improved by using Voigt lineshapes. In addition, the background can be evaluated during the fitting process without the need of extra measurements. As an application of the program, a pulse height transmission spectrum accumulated with a static⁵⁷Co source and detected with an argon-metane proportional detector, was least squares fitted to an elaborated complex trial lineshape function containing two Voigt lines plus a straight line. The fitting straight line parametersa andb characterize quantitatively the background. The very good PC-fitting obtained shows that the fitting of experimental spectra with the more realistic Voigt lineshapes is no longer a formidable task and that it is possible to evaluate and subtract the background inherent to the experiment during the fitting process.     

Experimental evaluation of effective atomic number of composite materials using back-scattering of gamma photons

A method has been presented for calculation of effective atomic number (Z_eff) of composite materials, by using back-scattering of 662?keV gamma photons obtained from a ¹³⁷Cs mono-energetic radioactive source. The present technique is a non-destructive approach, and is employed to evaluate Z_eff of different composite materials, by interacting gamma photons with semi-infinite material in a back-scattering geometry, using a 3^″?×?3^″ NaI(Tl) scintillation detector. The present work is undertaken to study the effect of target thickness on intensity distribution of gamma photons which are multiply back-scattered from targets (pure elements) and composites (mixtures of different elements). The intensity of multiply back-scattered events increases with increasing target thickness and finally saturates. The saturation thickness for multiply back-scattered events is used to assign a number (Z_eff) for multi-element materials. Response function of the 3^″?×?3^″ NaI(Tl) scintillation detector is applied on observed pulse-height distribution to include the contribution of partially absorbed photons. The reduced value of signal-to-noise ratio interprets the increase in multiply back-scattered data of a response corrected spectrum. Data obtained from Monte Carlo simulations and literature also support the present experimental results.     

Neutron fluence spectrometry using disk activation

A simple and robust detector for spectrometry of environmental neutrons has been developed. The technique is based on neutron activation of a series of different metal disks followed by low-level gamma-ray spectrometry of the activated disks and subsequent neutron spectrum unfolding. The technique is similar to foil activation but here the applied neutron fluence rates are much lower than usually in the case of foil activation. The detector has been tested in quasi mono-energetic neutron fields with fluence rates in the order of 1000–10000 cm⁻² s⁻¹, where the obtained spectra showed good agreement with spectra measured using a Bonner sphere spectrometer. The detector has also been tested using an AmBe source and at a neutron fluence rate of about 40 cm⁻² s⁻¹, again, a good agreement with the assumed spectrum was achieved.     

Dielectric response in ferroelectric BaTiO3

The far-infrared optical and dielectric properties of ferroelectric perovskite titanate powder BaTiO₃ are reported. The terahertz time-domain spectroscopy (THz-TDS) measurement reveals that the low frequency dielectric response of BaTiO₃ is closely related to the lowest pair of transverse optical (TO) and longitudinal optical (LO) modes near at 180 cm⁻¹, which is verified by Raman spectroscopy. This result provides a better understanding of the relation of low-frequency dielectric function with the optical phonon mode for ferroelectric materials. Combining terahertz TDS with Raman spectra, the overall low frequency optical phonon response of BaTiO₃ is presented in an extended spectral range from 6.7 to 1200 cm⁻¹.     

Muon bundles produced by UHE cosmic rays at large zenith angles

The first experimental results on a new EAS observable, the local muon density spectra measured with a large area coordinate detector DECOR in a wide range of zenith angles, are presented. These data correspond to the interval of primary particle energies from 10¹⁵ to 10¹⁸ eV. Some features of local muon density phenomenology are considered on the basis of an analytical model. Expected distributions of the events in the muon density have been calculated by means of the CORSIKA code and compared with experimental data. The text was submitted by the authors in English.