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At least 199 records · Page 11Linked to original sources
PubMed1999

Vacuum electron acceleration by coherent dipole radiation.

The validity of the concept of laser-driven vacuum acceleration has been questioned, based on an extrapolation of the well-known Lawson-Woodward theorem, which stipulates that plane electromagnetic waves cannot accelerate charged particles in vacuum. To formally demonstrate that electrons can indeed be accelerated in vacuum by focusing or diffracting electromagnetic waves, the interaction between a point charge and coherent dipole radiation is studied in detail. The corresponding four-potential exactly satisfies both Maxwell's equations and the Lorentz gauge condition everywhere, and is analytically tractable. It is found that in the far-field region, where the field distribution closely approximates that of a plane wave, we recover the Lawson-Woodward result, while net acceleration is obtained in the near-field region. The scaling of the energy gain with wave-front curvature and wave amplitude is studied systematically.

Journal Article↗
PubMed2000

TLD efficiency of 7LiF for doses deposited by high-LET particles.

The efficiency of 7 LiF TLDs (TLD-700) in registering dose from high-LET (> or = 10 keV/micrometers) charged particles (relative to 137Cs gamma rays) has been measured for a number of accelerated heavy ions at various particle accelerator facilities. These measured efficiency values have been compared with similar results obtained from the open literature and a dose efficiency function has been fitted to the combined data set. While it was found that the dose efficiency is not only a function of LET, but also of the charge of the incident particle, the fitted function can be used to correct the undermeasured value of dose from exposures made in mixed radiation fields where LET information is available. This LET-dependent dose efficiency function is used in our laboratory in determining total absorbed dose and dose equivalent from combined TLD and CR-39 plastic nuclear track detector measurements.

Calibration↗
PubMed1983

Recent muon fluence measurements at Fermilab.

Muon fields at Fermilab were measured during 1980-81 using a Mobile Environmental Radiation Laboratory (MERL). During the spring of 1980, measurements were made with the accelerator operating at 350 GeV; in the spring of 1981, measurements were made at 400 GeV. The measurements were used to obtain an understanding of muon dose-equivalent rates at various locations both on and off the Fermilab site. These were found to be less than 1 mrem/yr at any given location. The data indicate that more severe problems may be encountered during operations of the 1000 GeV accelerator presently being installed.

Elementary Particles↗
PubMedDate not supplied

Backscatter into the beam monitor chamber: implications for dosimetry of asymmetric collimators.

Backscatter from the asymmetric collimators of a linac into the beam monitor chamber (BMC) has been investigated for two accelerators having different BMC configurations. The effect has been quantified as a function of field size and collimator jaw position for 6 and 18 MV beams. The results indicate a maximum 2.5% (6 MV) and 4% (18 MV) decrease in output in one case and a negligible effect in the other case. The experiments indicate that the difference can be attributed to the different construction of the BMC's for the two accelerators.

Humans↗