The virtual source model for flattened beams was successfully adapted to a flattening filter free beam production. Water phantom and patient specific QA measurements show excellent results, and comparisons of IMRT plans generated in conventional and FFF mode are underway to assess dosimetric uncertainties and possible improvements in dose calculation and delivery.
The hydrodynamic response of metal targets to volume
heating by energy deposition of intense heavy-ion beams
was investigated experimentally. Recent improvements in
beam parameters led to a marked increase in specific deposition
power: 2·101040Ar18+
ions of 300 MeV/u focused to a spot size of 300 μm
(σ) × 540 μm (σ) yield a specific deposition
energy in solid lead of approximately 1 kJ/g in the Bragg
peak, delivered within 250 ns [full width at half
maximum (FWHM)]. This value allowed us for the first
time to observe heavy-ion-beam-induced hydrodynamic expansion
of metal volume targets. Measurements comprise expansion
velocities of free surfaces of up to 290 ± 20 m/s,
surface temperatures of ejected target matter of 1600–1750
K, and pressure waves in solid metal bulk targets of 0.16
GPa maximum absolute value and 0.8 μs FWHM. The experimental
results agree well with the results of a 2D hydrodynamic
code. Inside the interaction zone, which can only be accessed
by simulation, maximum temperatures are 2800 K and maximum
pressures are 3.8 GPa.
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