Are you F. Kniest?

Claim your profile

Publications (10)6.1 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The aim of the work is to investigate the revised concept of a neutron detector, offered by Saint Gobain-the BC-704 scintillation screen with a light readout by Wavelength Shifting (WLS) fibers. This detector was developed as a replacement of helium tubes, due to the lack of 3He on the world market. It is characterized by high sensitivity to gamma-rays, but the events from neutrons and gammas are well separated. Measurements with gamma and neutron sources have been performed and the results have been compared with helium-3 counter. According to American National Standards Institute (ANSI), we obtained n/γ discrimination on the level of 10−10, whereas absolute neutron detection efficiency was estimated as approximately two times higher than in the case of the reference 3He tube without the moderator. The tested detector is a sample prototype of one detector configuration of many possible, and that it can be modified to the neutron efficiency specification required.
    01/2011;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Liquid scintillators loaded with boron-10 or lithium-6 are capable to detect gamma rays, fast neutrons and also thermal neutrons. One of the popular methods applied in order to distinguish events originating from different particles is the pulse shape discrimination (PSD). The previously presented study of boron-10 loaded liquid scintillators using the PSD method showed different discrimination performance in scintillators such as BC523A, BC523A2, EJ339A2 and EJ309B5. It triggered a further study of the light pulse shapes in these scintillators originating from events related to gamma rays, fast and thermal neutrons. The light pulse shapes, measured using the single photon method, were recorded together with the 2-dimensional n/gamma discrimination data. Next, the recorded light pulses were gated using energy and the PSD information to extract pulses characteristic of the only one kind of particles. Finally, the analysis of the light pulse shapes with multi-exponential fits and calculation of decay time constants and intensities of components were performed. The results were compared with the data obtained for liquid scintillators not sensitive to thermal neutrons BC501A, EJ301 and EJ309.
    IEEE Transactions on Nuclear Science 01/2011; · 1.22 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Boron-10 loaded liquid scintillators were studied in order to improve n/¿ separation. Pulse shape discrimination (PSD) was implemented by means of a zero-crossing (ZC) method to distinguish between ¿-rays and fast/slow neutrons. Significant progress was done for BC523A2 and EJ339A2 scintillators loaded with reduced amount of <sup>10</sup>B (2% and 2.5%, respectively), as compared to the results obtained earlier with BC523A loaded with 4.4% of <sup>10</sup>B. The improvement was probably caused by the reduction of <sup>10</sup>B content, as indicated in the reported study. A <sup>10</sup>B loaded scintillator EJ309B5 based on non-flammable liquid was also studied, showing the best separation of thermal neutron capture events from fast neutrons, ¿-rays and noise.
    IEEE Transactions on Nuclear Science 03/2010; · 1.22 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The performance of undoped NaI crystal of a high purity of 7 N grade, developed by Saint-Gobain Crystals for a dark matter search, was studied at liquid nitrogen temperature using an avalanche photodiode. The measured quantities covered light output expressed in the electron-hole (e-h) pair number, non-proportionality characteristics, energy resolution and finally intrinsic resolution of the studied crystals. In contrast to the previous study, the new crystals showed comparable non-proportionality curves to that known for NaI(Tl) at room temperature and a poor energy resolution of about 8% for 662 keV gamma rays from a <sup>137</sup>Cs source. The performed study highlights a role of undoped NaI crystals in a better understanding of limitations of energy resolution in scintillation detectors. A high sensitivity to traces of doping may help to find the way of a modification of non-proportionality of other scintillators by a selective doping or co-doping. A further study of slow components of NaI light pulses and their influence on the energy resolution may clear up its possible deterioration caused by defects in the crystal structures.
    IEEE Transactions on Nuclear Science 07/2009; · 1.22 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A BC523A liquid scintillator loaded with boron-10 was tested as a detector for both fast and thermal neutrons. A pulse shape discrimination (PSD) method based on a zero-crossing principle was applied to distinguish between neutron and gamma radiation. High quantum efficiency Photonis XP5500B photomultiplier was used to enhance light detection from the scintillator. This allowed a good registration of the energy spectrum of neutron capture events on boron-10, corresponding to about 60 keV gamma-rays. The applied PSD method proved to be useful for n/gamma discrimination. A good resolving power of the method was achieved even without gating on neutron capture events. A comparison with a standard BC501A liquid scintillator was done to evaluate thermal neutrons detection efficiency in BC523A.
    IEEE Transactions on Nuclear Science 01/2009; · 1.22 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Boron-10 loaded liquid scintillators were studied in order to improve n/γ separation. Pulse shape discrimination (PSD) was done by means of a zero-crossing (ZC) method to distinguish between γ-rays and fast/slow neutrons. A significant progress was achieved for BC523A2 and EJ339A2 loaded with reduced amount of <sup>10</sup>B (2% and 2.5%, respectively), as compared to the results obtained earlier with BC523A loaded with 5% of <sup>10</sup>B. The improvement was probably caused by the reduction of <sup>10</sup>B content, as indicated in the latter study. A <sup>10</sup>B loaded scintillator EJ309B5 based on a non-flammable liquid was also studied, showing the best separation of thermal neutron capture events from fast neutrons, γ-rays and noise.
    Nuclear Science Symposium Conference Record, 2008. NSS '08. IEEE; 11/2008
  • [Show abstract] [Hide abstract]
    ABSTRACT: The performance of undoped NaI crystal of a high purity of 7 N grade, developed by Saint-Gobain Crystals for a dark matter search, was studied at liquid nitrogen temperature using avalanche photodiode. The measured quantities covered the light output expressed in the electron-hole (e–h) pair number, non-proportionality characteristics, energy resolution and finally the intrinsic resolution of the studied crystals. In contrast to the previous study, the new crystals showed comparable non-proportionality curves to that known for NaI(Tl) at room temperature and a poor energy resolution of about 8% for 662 keV gamma rays from <sup>137</sup>Cs source. The performed study highlights a role of undoped NaI crystals in a better understanding of limitations of energy resolution in scintillation detectors. A high sensitivity to traces of doping may help to find the way of a modification of non-proportionality of other scintillators by a selective doping or co-doping. A further study of slow components of the NaI light pulses and their influence on energy resolution may clear up its possible deterioration by defects in the crystal structures.
    Nuclear Science Symposium Conference Record, 2008. NSS '08. IEEE; 11/2008
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The performance of several BrilLanCe LaBr<sub>3</sub> crystals that range in size from Oslash 6 times 6 mm<sup>2</sup> up to Oslash 38 times 38 mm<sup>2</sup> coupled to XP5212 and R6231MOD photomultipliers were studied, and in the case of the small crystals, the crystals were also coupled to large area avalanche photodiodes (LAAPD) of Advanced Photonix, Inc. First, the performance of several photomultipliers from Photonis and Hamamatsu with LaBr<sub>3</sub> were compared to select the best one, not affecting energy resolution, besides the photoelectron statistics. The light output and energy resolution for 662 keV gamma rays from<sup>137</sup> Cs source were measured for all crystals. Moreover, for some crystals, the non-proportionality of the light yield and energy resolution versus gamma ray energy were measured and the intrinsic resolution of the crystals was calculated. For the smallest crystals of Oslash 6 times 6 mm<sup>2</sup> further comparative tests with LAAPD were carried out.
    IEEE Transactions on Nuclear Science 07/2008; · 1.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The performance of several BrilLanCetrade LaBr<sub>3</sub> crystals with the size of O6 times 6 mm<sup>2</sup> up to O38 times 38 mm<sup>2</sup> were studied coupled to the XP5212 and R6231MOD photomultipliers and in case of the small crystals, coupled also to large area avalanche photodiodes of Advanced Photonix, Inc. First, several photomultipliers of Photonis and Hamamatsu were compared in the work with LaBr<sub>3</sub> to select the best one, not affecting energy resolution, besides the photoelectron statistics. The light output and energy resolution for 662 keV gamma rays from <sup>137</sup>Cs source were measured for all crystals. Moreover, for some of them, the non-proportionality of the light yield and energy resolution versus gamma rays energy were measured and the intrinsic resolution of the crystals was calculated. For the smallest crystals of O6 times 6 mm<sup>2</sup> further comparative tests with LAAPD were carried out.
    Nuclear Science Symposium Conference Record, 2007. NSS '07. IEEE; 06/2008
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A BC523A liquid scintillator loaded with boron-10 was tested as a detector for both fast and thermal neutrons. Pulse shape discrimination (PSD) method based on a zero-crossing principle was applied to distinguish between neutron and gamma radiation. High quantum efficiency Photonis XP5500B photomultiplier was used to enhance light detection from the scintillator. This allowed a good registration of the energy spectrum of neutron capture events on boron-10, corresponding to about 60 keVee. The applied PSD method proved to be useful for n/y discrimination. A good resolving power of the method was achieved even without gating on neutron capture events. A comparison with a standard BC501A liquid scintillator was done to evaluate thermal neutrons detection efficiency in BC523A.
    Nuclear Science Symposium Conference Record, 2007. NSS '07. IEEE;