Unexpected 13N concentrations in ISIS synchrotron room air.

The specific activity of air in the large open room housing the 800-MeV proton synchrotron of the ISIS Spallation Neutron and Muon Source has been measured. Air from several positions within the ISIS synchrotron room was sucked through a long flexible tube, and run past a shielded HPGe gamma-ray detector outside the synchrotron room. In spite of an expectation that 13N should be the largest component of the overall activity in the air, the results of the measurements are consistent with the presence in the air of 11C and 41Ar only, and suggest that the activity in the air is mostly created not in the synchrotron room itself but in the massive shielding monoliths around the neutron-producing targets, monoliths through which ventilation air is drawn into the synchrotron room. Typical specific activities of 11C and 41Ar in the air in the synchrotron room are ∼0.10 and ∼0.03 Bq cm-3 respectively, the upper limit for 13N being at most ∼0.01 Bq cm-3.

Radiological characterisation of photon radiation from ultra-high-intensity laser-plasma and nuclear interactions.

With the increasing number of multi-terawatt (10(12) W) and petawatt (10(15) W) laser interaction facilities being built, the need for a detailed understanding of the potential radiological hazards is required and their impact on personnel is of major concern. Experiments at a number of facilities are being undertaken to achieve this aim. This paper describes the recent work completed on the Vulcan petawatt laser system at the CCLRC Rutherford Appleton Laboratory, where photon doses of up to 43 mSv at 1 m per shot have been measured during commissioning studies. It also overviews the shielding in place on the facility in order to comply with the Ionising Radiation Regulations 1999 (IRR99), maintaining a dose to personnel of less than 1 mSv yr(-1) and as low as reasonably practicable (ALARP).

Cell kinetics methods for clinical use: assessment of autoradiography and 125I-iodo-deoxyuridine with mouse Ehrlich tumour.

Superficial Ehrlich tumours in mice were used to assess how much information on cell kinetics could be obtained from only the simplest techniques of autoradiography, and in situ monitoring of 125I-iodo-deozyuridine. These techniques were selected as being readily applicable to clinical situations. Intradermal tumours were studied from the earliest stages of rapid growth to large slow growing tumours with necrotic cores, as well as tumours undergoing regression. For comparison, intramuscular tumours were studied with systemic injections of radioactive DNA precursors. It was found that extensive information on cell production and loss rates was obtained from a single injection of tritiated thymidine followed by a single biopsy, or alternatively in vitro labelling of one minute biopsy specimen, and measurements of only the labelling index, together with a knowledge of the tumour's growth characteristics. Following a single localized injection of 125I-iodo-deoxyuridine, the loss rate of radioactivity measured in situ for a period of about 1 week provided an index of cell loss rate from the tumours.