X-ray Source & Optics
Hippie is a soft X-ray beamline designed to deliver high intensity photon flux (1012 ph/s) with exceptional resolution (up to 40 000 eV) by fully utilises very low emittance of the 3 GeV ring.
Main Beamline Parameters
|Energy Range||110 eV - 2000 eV (for horizontal polarisation)
263 eV - 2000 eV (for circular polarisation)
|Resolution||20 000 (at 1000 eV) - 40 000 (at 400 eV)|
|Photon Flux||> 1012 ph/s|
|Spot Size||50 x 50 µ2|
|Type||APPLE II with permanent magnets|
|Period Length||53 mm|
|Physical Length||4 m (placed inside 5m straight section)|
|Accessible Polarisations||Linear (inc. Horizontal), Elliptical, Circular|
(away from ring)
(away from ring)
|Incidence Angle||1°||0° - 9°||0° - 12°||1.5°||-||1.5°|
|Optical Size, mm||320 x 10||370x10||130 x 10||120x28||-||130x20|
The beamline uses a Collimated Plane Grating Monochromator (cPGM), a monochromator type which was developed at BESSY. Currently only one branchline (AP-XPS) is planned to be build. However, it will be possible to build a second branchline by inserting another focusing mirror in the beam path. The other branch will then only need a refocusing mirror, since its exit slit and vacuum components are already installed.
The first optical element (M1) in the beamline is a toroidal mirror, which collimates the beam vertically and focuses the beam horizontally onto the exit slit. The cPGM consists of a plane mirror and one or more plane gratings. The dispersed radiation from the grating is focused horizontally onto the exit slit by the cylindrical focusing mirror (M3). The refocusing for the AP-XPS branch is accomplished by a single toroidal mirror (M4) with tangential and sagittal exit arms of 2 m and 2.060 m, respectively. In this way, the mirror does not image the vertical opening of the exit slit directly, but the vertical image size at the sample plane (2 m from M4) is dictated by the vertical divergence of the beam, which can be controlled by the monochromator. All the mirrors, except for the plane mirror in the monochromator, deflect horizontally – hence, all slope errors and heat load deformations on these mirrors are diminished in the dispersion plane in a well-known manner.
The calculated maximum resolution of the beamline is limited mostly by the diffraction limit set by the grating at low C-value. Increasing the C-value will decrease that contribution, and for the installed grating the slope errors become dominant.. However, a resolution between 40000 (at 400 eV) and 20 000 (at 1000 eV) is easily within reach. Below is shown the calculated flux for R = 10 000 (red) and the linear variation of R from 40 000 (at 400 eV) to 20 000 (at 1000 eV) as well as the spot pattern on the sample.
For more detailed discussion of EPU53 and beamline optics, please see following documents