9.2 Overall alignment procedure

9.2.1 Starting conditions: Pre-alignment of Secondary optics

It is required that the secondary optics has been previously aligned so that it is possible to display a focused secondary sample image on the MCP (Micro Channel Plate).

- Detection mode: Image

- Transfer lens: 250 μm

- FA: #1 (1800μm)

- CA: #2 (150 μm)

In order to have a good grid image on the MCP, adjust fine controls of the Immersion lens, stigmators and Transfer lenses (LTR1, LTR2).

9.2.2 Starting conditions: Primary optics

The Cs source must be arrived at the working position before starting the alignment. It is required to have the following instrumental conditions.

- D0=3000 μm (no apertures)

- D4=750 μm (#2)

- All lenses and deflectors to 0, except:

○ L4: ~ 6800V

- Beam Pos X: -400~ -500 digits

- Def FC: 160 – 180eV

which should be close to the typical values (for the source HV=10kV, Sample HV=-5kV)

- Raster size: 100 μm × 100 μm

- DTOS: ON

Check that DTOS is correctly calibrated by comparing with Raster Off. Beam shape when turn on raster and DTOS should be the same as the beam shape when raster off. If not, DTOS values (X, Y) must be adjusted until both cases have the same beam shape.