PTB’s sphere interferometer has been used in order to extract precisely the coefficient of thermal expansion (CTE) of ²⁸Si. This is necessary for the spheres of highly enriched ²⁸Si made for the Avogadro Project. For this purpose the diameter of one of the spheres was measured as a function of temperature between 17 °C and 30 °C. It could be demonstrated that the measured deviation of the CTE of ^2...

Between May 2005 and July 2006, the "Neutron Radiation" Department carried out three measurement campaigns for the determination of neutron spectra at altitudes of 85 m, 1195 m and 2650 m by means of the extended-range Bonner sphere spectrometer NEMUS [1]. The low neutron counting rates encountered under such ambient measurements made it necessary to develop new data analysis methods in which...

A commercially available detector made of a synthetic single-crystal diamond was investigated using PTB’s monoenergetic neutron reference fields in the energy range from 2.5 MeV to 14 MeV. Due to the high energy resolution, this detector is well suited for determining the properties of neutron fields and the influence of target properties on the neutron spectrum directly, without using...

Since electron scattering cross sections of numerous biomolecules cannot be experimentally determined under single collision conditions, an existing theoretical method for the computation of the elastic electron scattering cross sections has been refined. With this method, the differential elastic scattering cross-sections of trimethyl phosphate - which is very similar to the phosphate group...

Strahleninduzierte Schäden an der DNA werden zu einem großen Teil durch niederenergetische Elektronen verursacht. Die Simulation dieser Schädigung erfordert deshalb die Kenntnis der Elektronenstreuquerschnitte für Molekülgruppen, die als Bausteine in der DNA vorkommen oder diesen sehr ähnlich sind. Als Modellsysteme für die Molekülgruppe Deoxyribose wird gemeinhin das Molekül Tetrahydrofuran...

At PTB, a new method of activity determination for high-energy beta emitters has been developed and tested. This method offers numerous possibilities of application, e.g. in the fields of nuclear medicine or environmental radioactivity, and can be used for the investigation of beta spectra.

With the setting up of the thoron emanation measurement facility (TEM), it is the first time that a primary standard has been available for the short-lived radon isotope Rn-220 (T½ = 55 s). By means of activity standards, of the on-line measurement of the emanation capacity of the electrolytically deposited area sources of Th-228, and of the measured volume of the activity circuit, it is possible...

Within the scope of the international EURAMET project 749, PTB’s Working Group "Unit of Activity" has successfully dedicated itself to the task of determining alpha emission probabilities. At the same time, this project provided an opportunity for developing analytical algorithms and for improving existing ones.

At the Gustav Werner Cyclotron of The Svedberg Laboratory (TSL) in Uppsala, the high-intensity neutron beam ANITA (Atmospheric-like Neutrons from thIck TArget) is generated by bombarding a 25 mm thick tungsten target with 178 MeV protons. In the lethargy representation, the energy-weighted spectral yield E•YE, shows a so-called spallation peak at approx. 100 MeV and an evaporation peak at approx....

Working Group 6.22 has set up a spectrometry unit of its own for the requirements arising in the field of brachytherapy with photon sources. Due to their different composition, the different source types of brachytherapy seeds of the same nuclide (e.g. I-125) have different spectra. This leads to a change in the calibration factor and must be taken into account.

In 2008, the University Hospitals of Essen and Tübingen, which treat about 70% of the eye tumour patients in Germany with beta brachytherapy, as well as the only manufacturer worldwide of the eye applicators required for this therapy, BEBIG, asked PTB to carry out a verification of their respective beta basic dosimetry by means of a comparison. The comparison, which was started in 2009, is -...

Since the nuclear reactor accident of Chernobyl in 1986, early-warning systems have been established in all member states of the EU, with a total of approx. 4000 measurement stations to determine the area dose rate of external gamma radiation. Between 1999 and 2009, more than 70 detectors located at different measurement stations of the early-warning systems of 18 European member states, have been...

The dose distribution of the secondary radiation generated in a water phantom by a C-12 ion beam is measured in a tissue-equivalent proportional counter. The objective is to measure the dose distribution during ion therapy outside the patient to draw conclusions regarding the additional exposure of the patient to secondary radiation.

In an interdisciplinary cooperation between PTB, the German Collection of Microorganisms and Cell Cultures (Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH - DSMZ, Braunschweig) and the University Hospital of Düsseldorf, the new method of "live cell imaging" was established at the microbeam. Along particle tracks, DNA double strand breaks (DSB) occur which - within seconds and minutes...

A combination of neutron- and gamma-radiation transmission radiography allows explosives, drugs and fissionable material to be automatically detected. For this purpose, energy spectra and yields of the neutron and gamma emission of the nuclear reaction ¹¹B(d,n+γ)¹²C, which is the most interesting one for this application, were investigated and a concept for a combined inspection facility for air...

As the time for using the irradiation facility with thermal neutrons - which is currently operated by PTB at the research reactor of the GKSS - will expire next year, the possibility of setting up an irradiation facility at PTB in Braunschweig was investigated. For this purpose, calculations were made for the construction of a facility which is based on ²⁴¹Am-Be radionuclide sources, moderated by...

PTB has concluded a cooperation with the German manufacturer Carl-Zeiss Surgical GmbH in the field of absolute dosimetry for brachytherapy with miniature X-ray devices. This cooperation is aimed at developing a method for the determination of the absorbed dose to water in the near field of this radiation source.

It has been possible to determine the half-life of the long-lived isotope Be-10 with considerably reduced uncertainty. PTB has contributed to this especially by activity measurements by means of liquid scintillation counting.

Due to a lack of traceable measuring instruments in the field of radon and thoron progenies measurement, PTB and the Gammadata AB company have jointly developed a measuring instrument for progenies which can be used as a transfer standard.

In order to calibrate measuring devices for the determination of the Rn-222 activity concentration in air in the range below 1000 Bq/m³ in a traceable way, a low-level radon reference chamber is currently being set up. For the dissemination of the unit at such low radon activity concentrations, a high-sensitivity transfer standard is being developed.