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Scientific news from division 6

News 2011

To traceably calibrate measuring instrument for the determination of the Rn-222 activity concentration in air in the range below 1000 Bq/m3, a Low-Level Radon Reference Chamber is at present being set-up: this comprises a traceable volume for the generation of the reference atmosphere, a facility for the generation and transfer of defined activity and a highly sensitive transfer standard.

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In the recent past, radiation therapy with ion beams (e.g. protons or C-12 ions) has become of increasing importance. For this application, the ion beam is directed very precisely across the whole tumour volume by means of the so-called "raster scanning method". For carbon ions, this method has been developed at the Gesellschaft für Schwerionenforschung (GSI, Darmstadt) and is now used in therapy,...

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PTB is significantly involved in a project which is funded by the Ministry for the Environment, Nature Conservation and Nuclear Safety and deals with the quality control of test bodies for image quality assurance in X-ray diagnosis. In the first instance, the project is performed to develop procedures for the non-destructive testing of test body specifications. These procedures are then to be used...

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As the first metrology institute worldwide, the Physikalisch-Technischen Bundesanstalt (PTB) aims at establishing a calibration chain for miniature X-ray tubes in the unit "absorbed dose to water".

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The human eye is very sensitive to ionizing radiation. Scientists of the Physikalisch-Technische Bundesanstalt (PTB) have carried out large-scale calculations to determine the dose of the eye lens in different radiation fields. The calculations are intended to contribute to the definition of concrete requirements for eye dosemeters, which will then have to be included in the respective standards....

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Within the scope of a technology transfer project (BMBF Project IND 08/10, January 2010 to December 2011), neutron dosimetry techniques relying on optically stimulated luminescence (OSL) were improved in cooperation with scientists from the Bhabha Atomic Research Centre (BARC; Mumbai/India).

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Since the beginning of the 1990s, PTB has carried out dosimetric investigations of the secondary cosmic radiation in the atmosphere. In the course of time, the measuring instruments became more and more compact but also considerably smaller. The measurements were, however, always performed at cruising altitudes between 8 km and 12 km. In July 2011, a measuring instrument developed in cooperation...

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Radon Metrology has moved: After 20 years of successful work in the establishment, research and development of new procedures, the laboratory area had become too small, as the extension of radon metrology from radon-222 to radon-220 (thoron) has resulted in an increase in measuring equipment. In the new building, the renovated Elster Geitel Building, a new radon standard chamber RNK-II and a...

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Within the scope of a project funded by the European Fusion Development Agreement (EFDA), a compact neutron spectrometer has been characterized. To this end, a new analysis program has been developed which is based on CERN’s ROOT platform. The detector is used to measure the neutron spectra resulting from fusion plasma discharges at the Joint European Torus (JET, Culham, UK).

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For measurements in low-intensity neutron fields, it is absolutely indispensable to know the intrinsic background of detectors. During a two-month measurement campaign, all He-3 detectors of the NEMUS neutron spectrometer were investigated in the underground laboratory of PTB (UDO) and their lower detection limit was determined.

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The module, which was developed for radioactivity measurements, is very flexible thanks to the use of an FPGA, since its functionality is mainly determined by means of software (VHDL). In this way, the otherwise external coincidence counters could be integrated, and sufficient resources are available, also for future extensions of the tasks.

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The activation induced in air freight - and the possible resulting exposure of operators, passengers and end-users - when a system involving high-energy neutrons and gamma radiation is used to screen air freight has been calculated for diverse scenarios. The calculations were validated by means of a benchmark experiment at the PIAF accelerator.

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Nach dem Unfall des Kernkraftwerkes in Fukushima hat die Spurenmessstelle der PTB eine Messkampagne mit verkürzter Probenentnahme zur Bestimmung der Aktivitätskonzentration der in Fukushima freigesetzten Radionuklide in der Luft in Braunschweig durchgeführt. Die in Deutschland gemessenen Aktivitätskonzentrationen waren radiologisch unbedeutend. Die neben Braunschweig auch an Spurenmessstellen des...

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Generally, physical parameters of the track structure (ionization cluster size, particle flux, energy deposition), which are calculated by means of detailed Monte Carlo simulations, are used to estimate radiation-induced DNA damage. In collaboration with the Frankfurt Institute for Advanced Studies (FIAS), it is being investigated to which extent it is possible to describe these track structure...

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Experimentally determined energy spectra of emitted secondary electrons after the incidence of 6 MeV protons on a layer of 40 nm of amorphous ice were used to verify the Monte Carlo simulations of track structure. Especially when the electron affinity at the surface of the ice (at the limit of vacuum) was taken into account in the simulations, good agreement was observed between the experimental...

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For a new experiment aimed at determining the cross sections for the ionization and fragmentation of biomolecules by ions with energies lower than and close to the maximum of the collision stopping power, an accelerator has been designed to generate a beam of light ions with a kinetic energy of up to 150 keV/q (where q is the electric charge of the ion). The cross sections will be determined by...

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The potential for a magnetic field to influence the biological effectiveness of ionizing radiation has been investigated by means of irradiation experiments on human blood cells. For X-rays such as those used in mammography, the yield of chromosome aberrations did not demonstrate a clear effect when the cells were irradiated in the the presence of a 1 tesla magnetic field.

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