[Ifeffit] Double crystal monochromator

Matthew mamarcus at lbl.gov
Fri Dec 4 12:43:30 CST 2009

The curve observed on beamlines is the convolution of the curves of the two crystals in the mono, which is why it looks different 
from the single -bounce curve in the textbooks.
----- Original Message ----- 
From: "sankaran anantharaman" <sankaran.anantharaman at gmail.com>
To: "ifeffit" <ifeffit at millenia.cars.aps.anl.gov>
Sent: Friday, December 04, 2009 8:57 AM
Subject: [Ifeffit] Double crystal monochromator

> Hi everyone,
> Could anyone help me with this.
> Why is that the Darwin reflectitivity curve plotted versus rotation
> angle (in text books for example) and rocking curve plotted against
> rotation angle (observed in the oscilloscope at XAS beamlines for
> example) look different?
> I understand that the double crystal rocking curve (photon counts in
> Ionization chamber1 as a function of Bragg angle) is obtained by
> rotating the second crystal and recording the photon count. Is it
> right?
> Regards,
> Sankaran Anantharaman
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