A new limit on the resonant absorption of solar axions obtained via 169Tm-containing bolometer

A newly developed experimental technique based on 169Tm-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.

Development of a position-sensitive fast scintillator (LaBr3(Ce)) detector setup for gamma-ray imaging application

We have characterized a Cerium doped Lanthanum Bromide (LaBr3(Ce) ) crystal coupled with the position-sensitive photo-multiplier system for the gamma-ray imaging application. One can use this detector set-up for the scanning of high purity germanium detectors for pulse shape analysis in gamma-ray spectroscopy experiments and the image formation of an object by Compton back-scattering . The sensor has been tested for energy, timing and position information of the gamma-rays interacting within the detector crystal. The GEANT4 simulation results are consistent with the experimental results. We have reconstructed the image of irradiation spots in different positions throughout the detector crystal. Position resolution is found to be around 3.5 mm with the 2 mm collimated gamma-rays. The 2-d image of hexagonal Bismuth Germanate (BGO) crystal and a cylindrical LaBr3(Ce) crystal have been reconstructed in coincidence technique. The performance of the detector for imaging application has been investigated by coincidence technique in GEANT4 simulation and compared with the experimental data. We have reconstructed the 2-d images of objects with various geometrical shapes by Compton back-scattered events of the gamma-rays. This position-sensitive detector can be used as an absorber of a Compton camera for the image reconstruction of an extended radioactive source. One can also use this kind of set-up as in radiation imaging and many other applications where the energy and source position of the gamma-ray is the main interest.

Photoacoustic trace detection of gases at the parts-per-quadrillion level with a moving optical grating

The amplitude of the photoacoustic effect for an optical source moving at the sound speed in a one-dimensional geometry increases linearly in time without bound in the linear acoustic regime. Here, use of this principle is described for trace detection of gases, using two frequency-shifted beams from a CO2 laser directed at an angle to each other to give optical fringes that move at the sound speed in a cavity with a longitudinal resonance. The photoacoustic signal is detected with a high-Q, piezoelectric crystal with a resonance on the order of 443 kHz. The photoacoustic cell has a design analogous to a hemispherical laser resonator and can be adjusted to have a longitudinal resonance to match that of the detector crystal. The grating frequency, the length of the resonator, and the crystal must all have matched frequencies; thus, three resonances are used to advantage to produce sensitivity that extends to the parts-per-quadrillion level.

Accounting for detector crystal edge rounding in gamma-efficiency calculations theoretical elaboration and application in ANGLE software

In absolute and semi-empirical calculations of full gamma-energy peak efficiencies (ep), geometrical/compositional data characterizing the detector should be known in much detail. Among these, detector crystal edge rounding (bulletization), if neglected, may lead to large systematic errors, especially for low gamma-energies and close counting geometries. The errors show quadratic dependence on the extent of bulletization (bulletization radius). Mathematical/analytical solution to the problem - not reported so far - is elaborated in the present work. Relevant mathematical formulae are derived for a number of counting arrangements most frequently encountered in gamma-spectrometry practice (point, disc, cylinder, and Marinelli sources). These are subsequently programmed for numerical calculations and are now part of commercially available ANGLE software. Extensive calculation testing is performed for HPGe (both p- and n-type) and LEPD detectors (several sizes each), with various sources (point, disc, cylinder, Marinelli) and counting geometries (0-20 cm source-to-detector distance). Energy range considered was 10-3000 keV. To elucidate the significance of the issue, an error propagation study was conducted: results with bulletization taken into account are compared to those when bulletization was neglected. Corresponding errors are tabulated in an extensive Excel file. The file comprises about 152 000 error calculation results which are available for download; a few characteristic ones are selected for presenting in the paper. ANGLE proved handy (in programming) and fast (in calculations) when accomplishing this task. The data convincingly illustrate the impact of detector bulletization on gamma-efficiency and thus the need to account for. Even only slight bulletization (1-2 mm bulletization radius) is not negligible in many realistic counting situations. Reader/analyst can (1) compare his/her counting situation with these data so as to get the first impression of the problem and (2) use the mathematical model presented and/or ANGLE software to address the issue.

Evaluating 30mm2 Si(Li) detectors for light-element x-ray analysis

Light element x-ray microanalysis with the Si(Li) detecor is dependent on two detector crystal characteristics. The first is resolution, which has been traditionally standardized to be FWHM at Mn Kα. The second factor is efficiency, which is primarily but not entirely established by the detector area. These two factors effect light element sensitivity in an inverse manner. A premium resolution detector can be produced by minimizing the area, but the efficiency, as previously discussed , is directly proportional to the detector area.A special effect of efficiency degradation exists in the very low energy end of the spectrum where the x-ray energy pulses are approximately equal to the electronic noise level. The detector dead layer plays an important role in the low energy detection efficiency, since good, low energy efficiency is much more important than good manganese resolution or good electronic noise resolution.In a common 10mm2 Kevex detector, ~135 eV resolution at Mn is obtainable and the electronic noise resolution is 65 eV.