Time dynamics of the dose deposited by relativistic ultra-short electron beams.

Ultra-short electron beams are used as ultra-fast radiation source for radiobiology experiments aiming at very high energy electron beams (VHEE) radiotherapy with very high dose rates. Laser plasma accelerators are capable of producing electron beams as short as 1 fs and with tunable energy from few MeV up to multi-GeV with compact footprint. This makes them an attractive source for applications in different fields, where the ultra-short (fs) duration plays an important role. The time dynamics of the dose deposited by electron beams with energies in the range 50-250 MeV have been studied and the results are presented here. The results set a quantitative limit to the maximum dose rate at which the electron beams can impart dose.

Characterization of OSL dosimeters used at the ELI-beamlines laser-driven accelerator facility.

The Extreme Light Infrastructure (ELI) Beamlines laser-driven accelerator facility is set to operate the most intense non-military laser system in the world, with ultra-high power up to 10 PW, concentrated plasma intensities of up to 1024W cm-2, and ultra-short laser pulses of the order of few femtoseconds. A robust and redundant radiation monitoring system is in place to minimise risks to personnel and general public. Beryllium oxide optically stimulated luminescence (BeO-OSL) detectors are used to monitor radiation levels in the experimental building and surrounding grounds. In fact, in recent years, BeO-OSL have become an increasingly more popular choice for personal and environmental dosimetry. At ELI Beamlines, an exhaustive and thorough characterization process of the BeO-OSLs is in place. Dosimeter responses are studied as a function of delivered air kerma and photon energies. Calibration curves are calculated. Results from the latest calibration campaign are presented.

Compact high energy x-ray spectrometer based on forward Compton scattering for high intensity laser plasma experiments.

This article describes the design and presents recent results from testing and calibration of a forward Compton scattering high energy X-ray spectrometer. The calibration was performed using a bremsstrahlung source on the photon scattering facility at the γ Electron linac for beams with high brilliance and low emittance accelerator at Helmholtz-Zentrum Dresden-Rossendorf, which provides high energy X-ray photons with energies up to 18 MeV. The calibration was conducted at different bremsstrahlung end point energies-10.5, 13, 15, and 18 MeV. Experimental spectra show a systematic increase in the maximum energy, photon temperature, and flux. The spectrometer is effective for an energy range of 4-20 MeV with 20%-30% energy resolution. The spectrometer operates in low vacuum with pressure less than 0.1 mbar. Experimental tests showed that operating such a spectrometer in air causes a spuriously enhanced high energy signal due to Compton scattering of photons within air. The article also describes the design and shielding considerations which helped to achieve a dynamic range greater than 30 with this spectrometer. The comparison between the experimental results and Monte Carlo simulations are also presented.

Absolute calibration of imaging plate detectors for electron kinetic energies between 150 keV and 1.75 MeV.

This paper presents the calibration of two different kinds of image plates (IPs) for detecting electrons with kinetic energy in the range of 150 keV-1.75 MeV. The calibration was performed using a 90Sr ß source. The paper also provides the measured fading response for the IPs in the time range from 12 min to 18 h. Calibration results are compared to Monte Carlo simulations of energy deposited by the electrons in the sensitive layer of the IPs. It was found that within this energy range a linear relation between simulated energy deposited by the electron in the phosphor layer and the measured photo stimulated luminescence in the IP is adequate to model the response of the IP.

RESPONSE OF DOSEMETERS IN FIELDS GENERATED BY LASER-ACCELERATED PROTONS.

In laser-driven acceleration, ultra-short and intense laser pulses are focussed on targets to generate beams of ionising radiation. One of the most important issues to be addressed is personal monitoring. While traditional dosemeters were designed primarily for measurements in continuous fields, dosemeters for laser laboratories must be capable of working in pulsed fields of pulse length below 1 ps, in a single-shot regime up to the repetition rate of 1 kHz. Responses of conventional dosemeters (films, polyallyldiglycol carbonate, electronic personal dosemeter) to proton bunches of up to 30 MeV energy produced by South Korean PW laser system at the Advanced Photonics Research Institute, Gwangju Institute of Science and Technology were studied, both by means of Monte Carlo simulations and experimentally.

Behavioral and personality features in patients with lateralized Parkinson's disease.

BACKGROUND: Dopamine neurotransmission plays a key role in several brain activities, including motor, cognitive, and behavioral functions. Parkinson's disease (PD) typically begins with asymmetrical motor features related to asymmetrical dopamine denervation. This study was designed to examine whether distinct cognitive, behavioral, and personality features are related to this asymmetry. METHODS: Fifty-six patients with mild PD and lateralized motor features were grouped according to dominant side of motor features and evaluated using a neuropsychological assessment focused on attention and executive functions, impulse control disorders, and personality inventory. RESULTS: There were no differences in neuropsychological functions between patients with right and left lateralized PD, but differences occurred in personality features. Patients with motor impairment predominant on the left-hand side had prevalence of hypomania and conversion profile. CONCLUSIONS: This study suggests that side dominance of dopaminergic denervation may be related to personality features in patients with PD that could influence behavioral aspects.