The MIYAKE beamline at ASTRID
The MIYAKE monochromator beamline is one of three which uses the undulator source. A schematic diagram of the beamline is shown below.
| Optical Element | Optical parameters |
|
| HFM | horizontal-focusing mirror | spherical, R = 150 m, q = 87.5o |
| PG | plane grating | 1200 lines/mm |
| CM | cylindrical mirror | R = 2.40 m |
| ES | exit slit | |
| VFM | vertical-focusing mirror | spherical, R = 573 cm, q = 85.0–85.4o |
| PM | plane mirror | |
| FH + CH | foil holder (for second-order absorbers) + chopper | |
| IR | photon–ion interaction region | |
| IC + PD | gas ionization chamber + Al2O3 photodiode |
The basic design of the monochromator was proposed by Miyake et al. [1] and adapted for a wider energy range by West et al. [2]. It was originally made for the NINA Synchrotron Radiation Facility (SRF) at Daresbury, and was later modified for use at the Daresbury Synchrotron Radiation Source which replaced the NINA SRF. However, it was never used there and the optical elements were only acquired and installed when it was set-up at ASTRID. The design consists of a plane grating (1200 lines/mm) and a cylindrical mirror that focuses the beam on an exit slit. There is no entrance slit; the electron beam in the storage ring defines the magnitude of the source point.
The resolution of the photons with an energy <150 eV is typically of the order 4000–1000, and improves as the energy of the photons decrease. A resolving power of 10,000 can be observed with a photon energy of 30 eV.
The MIYAKE beam line is used in a merged beam set-up for absolute measurement of photoionisation cross-section of ions. The facility is capable of recording cross-sections as low as 10-19 cm2 and has been used to study a large number of singly- and multiply-charged, atomic and molecular, positive and negative ions. Photons from the MIYAKE monochromator in the energy range 15 to 200 eV are merged co-linearly with target ions over a distance of 50 cm, and the absolute photoionisation cross-section is determined from the resulting photonion yield with a typical accuracy of 10%.
For further information regarding this beam line and the photoionisation
experiment please see:
- H Kjeldsen et al., Nucl. Instr. and Meth. in Phys. Res. B 234 (2005) 349-361
- A recent Topical Review H. Kjeldsen J. Phys. B 39 (2006) R325-R377
- Henrik Kjeldsen's homepage (http://owww.phys.au.dk/~hkj/).
Photoionisation experiment: Finn Folkmann:
[1] K.P. Miyake, R. Kato, H. Yamashita, Sci. Light 18 (1969) 39.
[2] J.B. West, K. Codling, G.V. Marr, J. Phys. E 7 (1974) 137.
Last Modified 20 November 2009
