arXiv subjects

Y. A. Ramachers

Publications and source records attributed to Y. A. Ramachers.

22 records · Page 2Linked to original sources

arXiv2008

Optical readout tracking detector concept using secondary scintillation from liquid argon generated by a thick gas electron multiplier

For the first time secondary scintillation, generated within the holes of a thick gas electron multiplier (TGEM) immersed in liquid argon, has been observed and measured using a silicon photomultiplier device (SiPM). 250 electron-ion pairs, generated in liquid argon via the interaction of a 5.9KeV Fe-55 gamma source, were drifted under the influence of a 2.5KV/cm field towards a 1.5mm thickness TGEM, the local field sufficiently high to generate secondary scintillation light within the liquid as the charge traversed the central region of the TGEM hole. The resulting VUV light was incident on an immersed SiPM device coated in the waveshifter tetraphenyl butadiene (TPB), the emission spectrum peaked at 460nm in the high quantum efficiency region of the device. For a SiPM over-voltage of 1V, a TGEM voltage of 9.91KV, and a drift field of 2.5KV/cm, a total of 62 photoelectrons were produced at the SiPM device per Fe-55 event, corresponding to an estimated gain of 150 photoelectrons per drifted electron.

physics.ins-det↗

arXiv2008

Characterisation of a silicon photomultiplier device for applications in liquid argon based neutrino physics and dark matter searches

The performance of a silicon photomultiplier has been assessed at low temperature in order to evaluate its suitability as a scintillation readout device in liquid argon particle physics detectors. The gain, measured as 2.1E6 for a constant over-voltage of 4V was measured between 25degC and -196degC and found to be invariant with temperature, the corresponding single photoelectron dark count rate reducing from 1MHz to 40Hz respectively. Following multiple thermal cycles no deterioration in the device performance was observed. The photon detection efficiency (PDE) was assessed as a function of photon wavelength and temperature. For an over-voltage of 4V, the PDE, found again to be invariant with temperature, was measured as 25% for 460nm photons and 11% for 680nm photons. Device saturation due to high photon flux rate, observed both at room temperature and -196degC, was again found to be independent of temperature. Although the output signal remained proportional to the input signal so long as the saturation limit was not exceeded, the photoelectron pulse resolution and decay time increased slightly at -196degC.

physics.ins-det↗

arXiv2008

ACTIVIA: Calculation of Isotope Production Cross-sections and Yields

We present a C++ computer package, ACTIVIA, that can calculate target-product cross-sections and the production and decay yields of isotopes from cosmic ray activation using data tables and semi-empirical formulae. We describe the structure and user interface of the computer code as well as provide comparisons between the calculations and experimental results. We also outline suggestions on how the code can be improved and extended for other applications.

nucl-ex↗

arXiv2006

Radiation shielding for underground low-background experiments

The design task of creating an efficient radiation shield for the new COBRA double-beta decay experiment led to a comprehensive study of commercially available shielding materials. The aim was to find the most efficient combination of materials under the constraints of an extreme low-background experiment operating in a typical underground laboratory. All existing shield configurations for this type of experiment have been found to perform sub-optimally in comparison to the class of multilayered configurations proposed in this study. The method used here to create a specific shield configuration should yield a close to optimal result when applied to any experiment utilising a radiation shield. In particular, the survey of single material response to a given radiation source turns out to give a guideline for the construction of efficient multilayer shields.

nucl-ex↗