Re: Peltier-cooled solid state detector

Thomas Taut ( thomas.taut@do.netsurf.de )
Tue, 14 Oct 1997 08:03:03 +0200

Here is the possible reason for resolution decrease:
- If the sum pulse rate exceeds a certain amount of, say, 20000 cps the
resolution of the detector decreases dramatically. The actual decrease
depends on the used detection system and the parameters of the electronics.
Assuming the sample has high fluorecsency you have a continuous high pulse
rate, which is normally not visible in the region of interest (K-alpha of
the primary radiation). Thats why the resolution decreases.

Thomas Taut

> Questions for powder diffractionists (conventional X-rays).

> 1- I have noticed some resolution decrease when using a Peltier-
> cooled solid state detector instead of a proportional counter +
> a graphite back monochromator (Bragg-Brentano diffractometer).
> The observation applies only for samples with high fluorescency.
> No difference was detected with samples like Al2O3 or LaB6
> (standards from NIST). However, the conclusion is dubious as
> coming from a few patterns proposed by manufacturers.

> Any opinion welcome (preferably provide data from both
> diffractometer configurations, operating with same fluorescent
> sample and same slit systems).

> 2- The combination of an incident beam monochromator + a Peltier-
> cooled solid state detector is claimed to be the current best
> choice for a Bragg-Brentano powder diffratometer (eliminating
> K-alpha-2 and avoiding fluorescency). Nevertheless, it is hard
> to find data recorded with such an instrument (CuK-alpha-1) for
> samples containing non negligible amount of, say, V or Cr or
> Mn or Fe atoms...

> Has somebody such data available (another measurement with the
> same system of slits and a more conventional diffractometer
> (back graphite monochromator + proportional counter) would help
> for comparison) ?

> Thanks in advance,

> Armel Le Bail - Laboratoire des Fluorures - Universite du Maine
> Avenue O. Messiaen - 72085 Le Mans Cedex 9 - France
> http://fluo.univ-lemans.fr:8001/

Viele Gruesse
Thomas Taut