General Description

A first heatload shutter can be operated in a single shot mode to prevent optical elements as the toroidal mirror and the monochromator from a constant heatload. This device has been designed to deliver short bursts of unattenuated white radiation as needed for pulsed Laue diffraction. It is integrated far upstream in the beamline remove heatload from as many components as possible. A water cooled copper block with a 4 mm high slit is inserted in the beam pipe connected by flexible vaccum bellows. It is actuated by a stepper motor. The circular motion is translated into a +/- 7.7 deg oscillation of the copper block around its horizontal resting position. An inductive sensor is used to define a closed "home" position. The design goal was give a 10 ms oping window.

A safety shutter enables to switch off the x-rays in the experiments hutch to be able to enter safely. It has a gap of approx. 26 mm and thus the height has to be adjusted to the specific experiment (eg. the monochromatic mode implies a positional change of the beam by up to 200 mm with respect to a polychromatic mode)

We have installed a ms-shutter in the beamline vacuum in front of the chopper to allow single shot exposures. It consists of a 60 mm long bar with a trapezoidal tunnel along its length. The tunnel is 5 mm wide and its height increases linearly from 0.3 to 2.0 mm. The tunnel is centred on the axis of rotation, which gives two openings per turn. The bar is mounted on the axis of a stepper motor, which is mounted outside the vacuum via a ferrofluid feed-through. Normally this shutter is used in single-shot mode. In its closed position, the shutter tunnel is pointing down at –90 degrees. The shortest exposure times are obtained by accelerating the tunnel from –90 to +90 degree and opening times down to 0.2 ms have been obtained.