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Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasi-continuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields and the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. We benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution.

The European XFEL delivers up to 27000 intense (>1012 photons) pulses per second, of ultrashort (≤50 fs) and transversely coherent X-ray radiation, at a maximum repetition rate of 4.5 MHz. Its unique X-ray beam parameters enable groundbreaking experiments in matter at extreme conditions at the High Energy Density (HED) scientific instrument. The performance of the HED instrument during its first two years of operation, its scientific remit, as well as ongoing installations towards full operation are presented. Scientific goals of HED include the investigation of extreme states of matter created by intense laser pulses, diamond anvil cells, or pulsed magnets, and ultrafast X-ray methods that allow their diagnosis using self-amplified spontaneous emission between 5 and 25 keV, coupled with X-ray monochromators and optional seeded beam operation. The HED instrument provides two target chambers, X-ray spectrometers for emission and scattering, X-ray detectors, and a timing tool to correct for residual timing jitter between laser and X-ray pulses.

IntroductionColor processing is a central component of mammalian vision. Gender-related differences of color processing revealed by non-invasive functional transcranial Doppler ultrasound suggested right hemisphere pattern for blue/yellow chromatic opponency by men, and a left hemisphere pattern by women.Materials and MethodsThe present study measured the accumulation of [18F]fluorodeoxyglucose ([18F]FDG) in mouse brain using small animal positron emission tomography and magnetic resonance imaging (PET/MRI) with statistical parametric mapping (SPM) during light stimulation with blue and yellow filters compared to darkness condition.ResultsPET revealed a reverse pattern relative to dark condition compared to previous human studies: Male mice presented with left visual cortex dominance for blue through the right eye, while female mice presented with right visual cortex dominance for blue through the left eye. We applied statistical parametric mapping (SPM) to examine gender differences in activated architectonic areas within the orbital and medial prefrontal cortex and related cortical and sub-cortical areas that lead to the striatum, medial thalamus and other brain areas. The metabolic connectivity of the orbital and medial prefrontal cortex evoked by blue stimulation spread through a wide range of brain structures implicated in viscerosensory and visceromotor systems in the left intra-hemispheric regions in male, but in the right-to-left inter-hemispheric regions in female mice. Color functional ocular dominance plasticity was noted in the right eye in male mice but in the left eye in female mice.ConclusionsThis study of color processing in an animal model could be applied in the study of the role of gender differences in brain disease.

A four-rod RFQ accelerator is being built to accelerate deuterons from 20 keV to 3 MeV. At an operating frequency of 176 MHz the length is 3.8 m and the power consumption 250 kW, the beam current 5 mA. A special feature is the CW-mode operation. The status of the project and properties of the RFQ will be discussed. STATUS OF THE SET-UPTo assemble the RFQ and to put it into operation, mechanical alignment of the electrodes and RF tuning has to be done. First is the mechanical set-up consisting of an exact adjustment of the structure. Mechanical adjusting passes into adjusting of electrical properties.Finally, vacuum, power HF and beam tests will be handled.The actual state of this CW RFQ is the completion of the mechanical adjustment on the one, and some simulations for electrical properties on the other hand. MECHANICAL ADJUSTMENTThe set-up of a structure of 4 m length requires very accurate measurements in a conditioned environment. Already small changes i.e. in temperature can cause big errors. At all, the mechanical adjustment can be classified in three steps: The inner resonant structureThe RF structure, made up of copper, is composed of the base plate, on which the stems are mounted. On the stems, the electrodes are mounted. The electrodes are divided in three parts of about 1.3 m length. Table 1: RFQ property values Alignment to the cavityThe location of the beam, especially at input and output, should be oriented to the outer geometry of the cavity. Therefore, the inner structure, once installed in the cavity, needs to be aligned with respect to the cavity. This was done by the use of an align fixture which was attached to the cavity's head. The align fixture contains an arbour which is centred in the cylindric cavity and can be used as a reference for the beam position. Parts of the inner structure will be aligned to this reference. Exact adjustmentAs an other reference, the top flange of the cavity was used. This works very well, because the whole cavity has only one single lid all over the full length. This gives a very planar and exact reference for measurements in every position along the structure, as shown in figure 1. Adjustment of the electrodes is done in two steps: the vertical and the horizontal setting. For the horizontal, the tolerance of screws is used. The vertical step is more complex. Therefore, so called shims are made, which are Figure 1: Mechanical adjustment and reference face.Injection/output energy 20 / 1500 keV/u Isotope deuterium Frequency 176 MHz electrode voltage 65 kV RFQ length 3.8 m inner diameter 280 mm min. aperture 2.7 mm max. modulation 2.7 power consumption 250 kW vÃrvhprà x,v 160 S mm mrad a / b 0.85 / 0.28 mm mrad -1 number of cells 199 number of stems 40 long.outputemittance e-l 75 S deg. keV/u transmission 0 / 5mA 98 / 96 %