Fe-55 X-ray source
For precise measurements of Charge Transfer Efficiency (CTE) we are using
a Fe-55 X-ray source. It is emitting K-alpha photons with energy of
5.9KeV (80%) and K-beta photons with energy of 6.2KeV (20%).
Impacting the CCD these will free 1616 and 1778 electrons, respectively.
As the X-rays cannot penetrate a fused silica window, the source is placed
directly
in front of the CCD in vacuum.
From examining the amplitude of registered events versus their location, the
CTE and conversion factor can be determined.
Our source is manufactured by Dupont, product number NEN NES400S.
The intensity was 100 micro-Ci at delivery. With a half-life of 2.7 years, it
still delivers plenty of radiation 10 years after production.
It is a capsule 31.7mm in diameter, 9.6mm in height.
Outside of the Fe-55 source house.
To the lower left is the air-tight manual actuator for the shutter.
Source house facing detector. The shutter is a rotating plate of
1mm aluminium.
Shutter is open, and source exposed.
The source is held in place by a plate with
a 1cm diameter hole in order to reduce the flux to an
appropriate level for a 30 sec. exposure.
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Last updated March 15, 2001