STATION MPW6.1
Phoenix

Description

MPW6.1 does not have a dedicated end chamber, hence a variety of different experimental chambers can be used on this station. Experiments can be carried out using one of the existing experimental systems provided by the Physics College (details of which can be found on the station website under Compatible Equipment), alternatively you are welcome to use your own chamber (provided it meets the laboratories health and safety requirements) . We also welcome the opportunity to develop new experimental chambers through both in-house and external research grants. Examples of some of the techniques that have been carried out on the station include Photoelectron Spectroscopy (PES) and X-ray absorption near edge structure (XANES) using the ARUPS10 chamber, Optically detected X-ray absorption (OD-EXAFS), using the MOLES chamber. Spin Polarised photoelectron spectroscopy using both micro-mott and time of flight detectors. Gas Phase photoelectron spectroscopy using the TEARES chamber and SR Kelvin Force Microscopy.

News

Successful Commissioning Experiments - June 2004
Drs C. Cacho (Principal Investigator) and C. Baily have recently carried out successful commissioning experiments on the new Spin Polarisation Chamber (SPS2) on Station 6.1 at the SRS. This chamber was refurbished during the last shutdown and has a new OMICRON Leed/Auger system installed on it. The chamber utilizes the time-of -flight (TOF) spin polarisation detector that was also designed and assembled at the SRS. This research group showed that it was possible to detect spin asymmetry using linearly polarised light and pulsing the field in the sample via a set of magnetisation coils placed behind the sample. The results obtained showed for the first time that the TOF detector is able to detect such asymmetry.

Functional Description

Commissioned in June, 2001, MPW6.1 ("PHOENIX") is a new beamline. Based on a multi-pole wiggler insertion device, providing about 10 times the flux output, as compared with traditional bending magnets at Daresbury. The energy range covered is from 40-450 eV (nominally), but there is significant flux available to 500 eV. This is achieved at good resolution across the whole energy range; typical working values for the resolving powers are up to 4000, although the design capability is ultimately for 10000.

Technical Description

The optical components of the beamline consist of 3 focussing mirrors, and a monochromator that has 3 interchangeable diffraction gratings. The beamline also has entrance and exit slits, to improve the beamline resolution and a series of baffles to shape the beam. A more detailed description of the mirrors and gratings is given below, all mirrors are gold coated.

• Mirror 1 - Horizontal deflecting and focusing mirror - This removes approximately half the radiation fan for use on 6.1 (the other half goes to 6.2).
  Heatload = 1200W (300mA beam). Material = Silicon
• Mirror 2 - Vertically deflecting and focusing mirror - This focuses the source onto the monochromator slits.
  Heatload = 40W (300mA). Material = Silicon
• Mirror 3 - Horizontal and vertical focus. - Focuses the light onto the sample.
  Heatload = negligible. Material = Silica
• Grating 1 - Low energy (40 to 80eV).
  Line density = 300l/mm. Surface coating = gold.
• Grating 2 - Medium energy (80 to 160eV).
  Line density = 600l/mm. Surface coating = gold.
• Grating 3 - High energy (160 to 320eV).
  Line density = 1200l/mm. Surface coating = nickel.

Developments

A new improved fast pumping stage has been installed on the station for gas phase experiments. Ozone cleaning of the mirrors has led to a significant reduction in the levels of carbon detected on the surface, this has allowed carbon K edge experiments to be routinely carried out on the station.

Proposed Developments

A temperature stabalised enclosure is to be constructed around the monochromator. This is to minimise the effect of temperature changes to the tilt of the grating.
An argon ion gun will be installed on the Io mesh, this will allow cleaning of the mesh to remove any carbon contamination from the surface which can lead to absorption effects.
A partial yield detector (PYD), is to be installed on the Io mesh. This would help to ensure more accurate data normalisation, especially during experiments that involve sample analysis using a PYD itself.

Benchmarks

Turnaround times - UHV surface science experiments normally require at least 3 days of preparation prior to the beamtime (for configuration and bakeout) and one day to dismantle the apparatus. More complex experimental arrangements may require additional time for setup. Please contact one of the Station Scientists to discuss this in more detail.
Gas phase experiments and those requiring moderate vacuum levels without bakeout (10-7 to 10-8 torr) can normally be set up with only one day of preparation.