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Scientific news from division 6

News 2021

Silizium-32 hervorgehoben auf Nuklidkarte

In collaboration with the Paul Scherrer Institute (PSI) and other partners, PTB determines the half‑lives of very long‑lived radionuclides. Current studies include molybdenum‑93, manganese‑53, silicon‑32, potassium‑40, terbium‑157, and lanthanum‑137.

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A novel photon irradiation facility that provides reference fields for the harmonization of early‑warning dosimetry systems has been successfully tested and put into operation. This system will also be used for ensuring a uniform federal quality standard in accordance with the German Radiation Protection Ordinance (StrlSchV § 103).

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With the aid of an imaging Timepix3 radiation detector, the angle of ionizing radiation incidence for photons was determined using the shadow cast by a specific mounted absorber set‑up. For data analysis, a stochastic particle filter algorithm was implemented that is able to quickly and efficiently calculate the angle of incidence from image data at very low dose values of only 480 nGy and to do...

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The response of a germanium detector was determined for photon energies up to 420 keV. Subsequently, the photon spectra of several of the division's X-ray facilities were measured with this detector.

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An innovative development in radiation therapy combines a medical linear accelerator with an MRI scanner. Due to the magnetic field required for the MRI, the dose distribution and the behavior of the measuring devices change during irradiation, something that had already been the subject of scientific studies for large irradiation fields. As part of the EMPIR project “<acronym title="Traceable...

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two CT scans of a torso

The aim of personalized computed tomography (CT) dosimetry is to obtain an immediate indication of the effective dose following CT imaging. The effective dose is regarded as the measure of the magnitude of radiation exposure with respect to stochastic radiation effects. As part of a doctoral project, a...

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Reference dosimetry performed with calibrated ionization chambers in carbon ion beams has a significantly higher measurement uncertainty than when done in high‑energy photon fields. This is mainly due to the high uncertainty of the correction factor for the beam quality, kQ, which must be theoretically calculated in carbon ion beams because no experimental data is available.

In order to reduce...

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In the last few years, a new radiotherapy modality, called FLASH radiotherapy, has been investigated and is showing advantages over conventional treatment modalities. To test the FLASH modality and quantify its advantage over conventional treatment, new dose measurement techniques and codes of practice have to be studied and elaborated. For this purpose, the...

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For the calibration of neutron measuring instruments, PTB uses a neutron reference field produced by a Cf‑252 source which is moderated by means of heavy water. Having exact knowledge of the neutron spectrum is of decisive importance for determining the values of the operational radiation protection quantities in this reference field. A detailed simulation model of the Cf‑252 source moderator...

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The air kerma at Co‑60, Cs‑137 and Ir‑192 gamma radiation is the central dose quantity in the field of radiation protection as well as in brachytherapy. In a new research project at PTB, two high‑volume, air‑filled cavity ionization chambers were characterized. These ionization chambers are specifically suited for the primary measurement of air kerma at low air kerma rates.

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PTB’s Working Group 6.11, Unit of Activity, has recently succeeded in determining three short half‑lives with high accuracy (< 100 ns). In the study, the short‑lived isomeric states of Np‑237, Pa‑233, and Ac‑227 were investigated by digital 4πα(LS)‑γ coincidence counting.

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Through a collaboration between the PTB (Department 6.3), IRSN, NCBJ and EURADOS, new important interaction cross‑section data are being implemented in the Monte Carlo Geant4‑DNA simulation toolkit. This development should not only improve the accuracy of radiation transport simulations in tissue‑equivalent media, but also increase the versatility of using Geant4‑DNA in micro- and nanodosimetry.

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The International Commission on Radiation Units and Measurements (ICRU) has recommended new quantities for radiation protection in its Report No. 95. Values were calculated for these quantities to be able to estimate the consequences for the calibrations or irradiations of radiation protection dosemeters in the newly recommended radiation protection quantities with photon and/or beta radiation.

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