SPECS 2D-CCD, User Manual

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Manual V2.docx | Status 10.12.2015 | Version 1
Phosphor screen 6.12
The phosphor coating on the screen is produced by sedimentation of phosphor grains on a
substrate. The sedimentation process leads to a very homogeneous layer structure. The
maximum thickness of the phosphor coating is technically limited to approximately 100 μm.
The screens are stable under vacuum conditions and can resist temperatures up to 400°.
Caution!
The phosphor coating is very sensitive to physical stress—a light touch with a finger
immediately destroys the surface. To remove dust or small particles from the screen, blow
them off with a jet of dry air or nitrogen.
Three criteria allow for the choice of the most suitable phosphor type:
•
Efficiency
•
Emission spectrum
•
Luminescence decay time
Most phosphors have a long after-glow—the emission of photons after operating at
brightness levels suitable for human vision. After-glow effects are reduced due to the
selection of the standard phosphor type P 43 (Gd
2
O
2
S:Tb). This has a high efficiency and a
true exponential decay.
Aging is accelerated by higher screen voltages. Therefore, we recommend a moderate screen
voltage of about 2500–3000 V for standard operation conditions.
If an electron hits the phosphor screen with energy E, then the number of excited photons,
n
, is
, -
.
/0
Here, ε ~ 0.2, the energy conversion factor of the phosphor and
h
ν
the energy of the emitted
photons.
Application data 6.13
This section presents some data acquired using SPECS CCD detectors as examples of the
flexibility of this detector.
The Cu(111) surface state was measured using a PHOIBOS 100 analyzer and the SPECS UVS
10/35 helium discharge lamp. The data acquisition time was 200 seconds for the whole
image. The energy and angle resolution is limited by the quality of the Cu(111) surface and