RESUMO
A new soft X-ray beamline, BL07LSU, has been constructed at SPring-8 to perform advanced soft X-ray spectroscopy for materials science. The beamline is designed to achieve high energy resolution (E/ΔE> 10000) and high photon flux [>10(12)â photons s(-1) (0.01% bandwidth)(-1)] in the photon energy range 250-2000â eV with controllable polarization. To realise this state-of-the-art performance, a novel segmented cross undulator was developed and adopted as a light source. The details of the undulator light source and beamline monochromator design are described. The achieved performance of the beamline, such as the photon flux, energy resolution and the state of polarization, is reported.
RESUMO
\textbf{Objective.} Proton radiotherapy's efficacy relies on an accurate Relative Stopping Power (RSP) map of the patient to optimise the treatment plan and minimize uncertainties. Currently, a conversion of a Hounsfield Units (HU) map obtained by a common X-ray Computed Tomography (CT) is used to compute the RSP. This conversion is one of the main limiting factors for proton radiotherapy. To bypass this conversion a direct RSP map could be obtained by performing a proton CT (pCT). The focal point of this article is to present a proof of concept of the potential of fast pixel technologies for proton tracking at clinical facilities. \textbf{Approach.} A two-layer tracker based on the TJ-Monopix1, a Depleted Monolithic Active Pixel Sensor (DMAPS) chip initially designed for the ATLAS, was tested at the proton MiniBeam RadioTherapy (pMBRT) beamline at the Curie Institute. The chips were subjected to 100 MeV protons passing through the single slit collimator (0.4$\times$20 mm$^2$) with fluxes up to $1.3 \times 10^7$ p/s/cm$^2$. The performance of the proton tracker was evaluated with GEANT4 simulations. \textbf{Main Results:} The beam profile and dispersion in air were characterized by an opening of 0.031~mm/cm, and a $\sigma_x=0.172$~mm at the position of the slit. The results of the proton tracking show how the TJ-Monopix1 chip can effectively track protons in a clinical environment, achieving a tracking purity close to~70~$\%$, and a position resolution below 0.5 mm; confirming the chip's ability to handle high proton fluxes with a competitive performance. \textbf{Significance:} This work suggests that DMAPS technologies can be a cost-effective alternative for proton imaging. Additionally, the study identifies areas where further optimization of chip design is required to fully leverage these technologies for clinical ion imaging applications.
RESUMO
We developed a vacuum-compatible pulse selector for a free-electron laser. A rotating cylinder with eight apertures in a vacuum is driven by a closed-loop stepping motor system through a magnetically coupled rotary feedthrough. A field programmable gate array is used to synchronize the cylinder rotation with a trigger signal of the accelerator at a maximum repetition rate of 60 Hz. We achieved to select specific pulses from a continuous pulse train of the SPring-8 Compact SASE Source.
RESUMO
The degree of circular polarization of soft X-rays emitted from the multi-polarization-mode undulator of BL17SU at SPring-8 has been deduced by means of magnetic circular dichroism in core-level X-ray absorption spectroscopy for a ferrimagnetic Gd-Fe-Co amorphous thin film. The results of reference measurements performed using well characterized undulator radiation of BL25SU at SPring-8 have also been utilized. The degrees of circular polarization were presumed for all the available operational modes and were compared with simple theoretical calculations. It was found that the calculated degrees of circular polarization were validated by the measurements reasonably well and will be useful in further experiments at BL17SU.