X-rays only when you want them: optimized pump-probe experiments using pseudo-single-bunch operation.

Laser pump-X-ray probe experiments require control over the X-ray pulse pattern and timing. Here, the first use of pseudo-single-bunch mode at the Advanced Light Source in picosecond time-resolved X-ray absorption experiments on solutions and solids is reported. In this mode the X-ray repetition rate is fully adjustable from single shot to 500 kHz, allowing it to be matched to typical laser excitation pulse rates.

Targeting of macrophage activity by adenovirus-mediated intragraft overexpression of TNFRp55-Ig, IL-12p40, and vIL-10 ameliorates adenovirus-mediated chronic graft injury, whereas stimulation of macrophages by overexpression of IFN-gamma accelerates chronic graft injury in a rat renal allograft model.

Adenovirus (Ad)-mediated gene transfer of immunoregulatory molecules prevents acute allograft rejection. It is here analyzed for the first time whether this approach may prevent the development of chronic renal allograft injury in rats. Renal allografts (F344-->Lewis rat) were ex vivo transduced in group I with control Ad-construct, group II with three different therapeutic Ad-constructs expressing the immunoregulatory molecules vIL-10, TNFRp55-Ig, and IL-12p40, and group III with AdIFN-gamma.

Observation of broadband self-amplified spontaneous coherent terahertz synchrotron radiation in a storage ring.

Bursts of coherent synchrotron radiation at far-infrared and millimeter wavelengths have been observed at several storage rings. A microbunching instability has been proposed as the source for the bursts. However, the microbunching mechanism has yet to be elucidated.

Variable linear polarization from an X-ray undulator.

A new X-ray undulator has been designed and constructed which produces linearly polarized X-rays in which the plane of polarization can be oriented to a user selectable angle, from horizontal to vertical. Based on the Apple-II elliptically polarizing undulator (EPU), the undulator rotates the angle of the linear polarization by a simple longitudinal motion of the undulator magnets. Combined with the circular and elliptical polarization capabilities of the EPU operating in the standard mode, this new undulator produces soft X-ray radiation with versatile polarization control.

Measuring and optimizing the momentum aperture in a particle accelerator.

Particle motion in storage rings is confined by various aperture limits, the size of which restricts the performance of the ring in terms of injection efficiency, lifetime, etc. Intrabeam scattering makes particles sweep a large portion of the phase space, where their motion may eventually be resonantly or chaotically excited to large amplitudes leading to collision with the vacuum chamber. We report here the studies performed at the Advanced Light Source (ALS) on the on- and off-momentum particle motion that provides a good understanding of these limitations.