Table of Contents
Advertisement
Monochromated X-Ray Source with XR5 Electron Gun
Each of the lens modes gives in its title three pieces of information.
(i)
The size of the final X-Ray spot in m. This is defined the 20% to 80%
points of the spot when moved over a "knife-edge".
(ii)
The beam energy, in kVolts.
(iii)
The power in Watts of the electron source on the anode.
The first operation mode in the list is entitled "Standby" and is a relatively low power
X-Ray beam into a 500 m spot. This is designed to be used for setting up
experiments between acquisitions or during transfer of samples. The low power
density on the anode results in minimal "wear and tear" of the source.
When running the source the operation mode selected will depend upon the type of
experiment. The higher power modes give more signal but cover a larger area. The
lower power modes give less signal but can be used for source defined selected
area XPS.
It should be noted that there is a "warm up time" associated with the XR5 gun.
During this time the monochromated spot will appear to move on the sample surface
as the gun reaches a steady state condition. It is recommended that the gun is left in
the standby condition for 15-30 minutes before acquisition or alignment so that a
stead state is obtained.
4.3
Switching on the Re-circulated Water
The first task to carry out is to switch on the re-circulated water supply. Power for this
may be supplied from the system or from a separate mains circuit in the laboratory. If
this is not switched on then when an attempt is made to switch on the monochromator
the booster pump will run dry, be much louder than normal and possibly be damaged.
The monochromator gun will not turn on as the water flow interlock will have failed.
4.4
Observing the Monochromator Spot
For fine-tuning of the monochromator alignment or simple checking that the
monochromator is working properly it is often very useful to observe the
monochromator spot.
This is most easily achieved with a standard phosphor sample as demonstrated in
Figure 4-4.
Figure 4-4: Observing the Monochromator Spot Size on a Phosphor Sample
Issue 5
17
Monochromator and XR5 (HA600054)
Monochromated X-Ray Source with XR5 Electron Gun
4.5
Limits of Operation
The anode has set limits at which it can operate, exceeding these limits can damage
the anode and shorten its life time. These limits are shown in Figure 4-5. It is very
possible to cause some damage to the source, particularly to filaments and anode-
coatings if the figures are exceeded so expert knowledge is required to avoid these
conditions. Although the settings can be freely accessed from the XR5 user window it
is not recommended that the user should alter any value within this window, except
under instruction from a Thermo Fisher Scientific engineer. Hard copies of the values
set up for each mode will be made at the time of installation.
All the preset monochromated X-ray spot conditions all lie within the safe operation
conditions.
Figure 4-5: Anode Operation Limits for the XR5 Mono. X-ray Source
Monochromator and XR5 (HA600054)
18
Issue 5
Advertisement
Table of Contents
