Radiation protection modelling for 2.5 Petawatt-laser production of ultrashort x-ray, proton and ion bunches: Monte Carlo model of the Munich CALA facility.

The 'Centre for Advanced Laser Applications' (CALA) is a new research institute for laser-based acceleration of electron beams for brilliant x-ray generation, laser-driven sub-nanosecond bunches of protons and heavy ions for biomedical applications like imaging and tumour therapy as well as for nuclear and high-field physics.The radiation sources emerging from experiments using the up to 2.5 petawatt laser pulses with 25 femtosecond duration will be mixed particle-species of high intensity, high energy and pulsed, thus posing new challenges compared to conventional radiation protection. Such worldwide pioneering laser experiments result in source characteristics that require careful a-priori radiation safety simulations.The FLUKA Monte-Carlo code was used to model the five CALA experimental caves, including the corridors, halls and air spaces surrounding the caves. Beams of electrons (<5 GeV), protons (<200 MeV),12C (<400MeV/u) and197Au (<10MeV/u) ions were simulated using spectra, divergences and bunch-charges based on expectations from recent scientific progress.Simulated dose rates locally can exceed 1.5 kSv h-1inside beam dumps. Vacuum pipes in the cave walls for laser transport and extraction channels for the generated x-rays result in small dose leakage to neighboring areas. Secondary neutrons contribute to most of the prompt dose rate outside caves into which the beam is delivered. This secondary radiation component causes non-negligible dose rates to occur behind walls to which large fluences of secondary particles are directed.By employing adequate beam dumps matched to beam-divergence, magnets, passive shielding and laser pulse repetition limits, average dose rates in- and outside the experimental building stay below design specifications (<0.5µSv h-1) for unclassified areas,<2.5µSv h-1for supervised areas,<7.5µSv h-1maximum local dose rate) and regulatory limits (<1mSv a-1for unclassified areas).

Resolution of pulmonary embolism on CT pulmonary angiography.

OBJECTIVE: The objective of our study was to retrospectively determine the rate of resolution of pulmonary emboli (PEs) in individual vessels and the rate of complete resolution of PEs on CT angiography. MATERIALS AND METHODS: Follow-up CT pulmonary angiograms, obtained during the period from January 2006 through May 2009, of 69 patients with acute PE from two hospitals were assessed. Initial and follow-up CT angiograms were reread together by one radiologist at both of the hospitals. Images were obtained using a 10-, 16-, 40-, or 64-MDCT angiography unit with a 0.5-mm collimation, 1.25- to 2.0-mm reconstruction, 0.3- to 0.5-second rotation time, and 7.5-mm/rotation table speed. All CT angiograms were obtained using a PE protocol. RESULTS: Follow-up CT angiograms were obtained in 35 men and 34 women who ranged in age from 17 to 92 years (mean age, 58 +/- 17 [SD] years). Complete CT angiographic resolution of PE was seen in six of 15 patients (40%) 2-7 days after diagnostic imaging. After day 28, complete resolution occurred in 17 of 21 patients (81%). The main pulmonary arteries showed complete PE resolution during days 2-7 in seven of nine patients (78%) and after day 28 in 34 of 36 (94%). The lobar pulmonary arteries showed complete resolution of PE during days 2-7 in 23 of 33 patients (70%) and after 28 days in 44 of 48 (92%). The segmental pulmonary arteries showed complete resolution during days 2-7 in eight of 21 patients (38%) and after day 28 in 38 of 38 (100%). CONCLUSION: Most patients (81%) showed complete resolution of PE on CT angiography after 28 days. PEs resolved faster in the main and lobar pulmonary arteries than in the segmental branches.