Magnetic Shielding
Figure 10: PHOIBOS µ-Metal Shielding
3.3.1 Magnetic Coupling for μ-Metal Chambers
A proper shielding of the front of the lens and the experiment chamber is also neces-
sary, and to facilitate magnetic coupling to these parts, the PHOIBOS analyzer is de-
livered with a collar attached to the front of the lens shielding. The chamber shielding
needs good physical connection to the analyzer shielding, especially for slowly charged
particles. The insertion depth of the analyzer shielding has to be modified if the shield-
ing is too far inside the chamber (normally by a non-magnetic lens protection cap ad-
ded to the lens shielding). Please contact SPECS for advice regarding the -metal shieldμ -
ing.
3.3.2 Trim Coil
The PHOIBOS analyzer can be equipped with a trim coil around the outer hemisphere
of the analyzer. With a coil current |Icoil| < 150 mA the residual magnetic field compon-
ent within the analyzer along the lens axis can be compensated. The magnitude and
the sign of the coil current depends on local terms.
The radius of gyration G for an electron with kinetic energy E
kin
in a magnetic field B is
RG
[
m
]=3.37⋅
E
kin
[
eV
]
B
[
T
]
(14)
At the center of a very short coil with coil current I, radius R and n windings the mag-
netic field is
PHOIBOS 21
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