# Why do I need to move the detector in a Goniometer to 2-omega?

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• JanSpintronics
In summary, there is a difference in angular speed between moving the detector and the Röntgen source in a Goniometer or Bragg-Bretano measurement. According to the provided link, if the sample is rotated, the angular speed is double that of the source, while if the source is rotated, the angular speed is the same. This is due to the angle of the primary beam and the reflected beam being the same.
JanSpintronics
Hola,

I have a question to a Goniometer or more specific of a Bragg-Bretano- measurement, where you need to move your detector in die double angular speed then you move your Röntgen source. Why is it so? In my thoughts, it makes sense to move them in the same speed of the röntgen source and you will get always the intensity. Because if you have an angle of ## \theta ## which is the angle of your primary beam, your reflected beam is just taking the same angle. Why you need to move it just the double angle here?

Hi Jan,

JanSpintronics said:
you need to move your detector in die double angular speed then you move your Röntgen source
Says who ? How is your detector angle defined ?
Picture on sheet 21 here agrees with you

The link that @BvU provided (sheet 21) answers this completely: If the sample is rotated (rather than the source), then the angular speed is ## 2 \omega ##. If the source is rotated, then the angular speed is ## \omega ##.

## 1. Why is it necessary to move the detector in a Goniometer to 2-omega?

The movement of the detector in a Goniometer to 2-omega is necessary for obtaining accurate measurements of the diffraction pattern. This movement allows for the detector to capture the full range of diffraction angles, resulting in a more complete and precise analysis of the crystal structure.

## 2. What is the significance of 2-omega in a Goniometer?

2-omega is the angle of rotation in a Goniometer that corresponds to the diffraction angle of the crystal lattice. This angle is important because it allows for the accurate measurement of the diffraction pattern, which is essential for determining the crystal structure.

## 3. Can the detector be moved to a different angle in a Goniometer?

Yes, the detector can be moved to different angles in a Goniometer, but 2-omega is the most commonly used angle for diffraction measurements. Other angles, such as omega and chi, may also be used for specific types of analysis.

## 4. How does moving the detector to 2-omega affect the diffraction pattern?

Moving the detector to 2-omega allows for the detection of a wider range of diffraction angles, resulting in a more complete and accurate diffraction pattern. This can help to identify additional peaks and provide a more detailed analysis of the crystal structure.

## 5. Is it possible to analyze a crystal structure without moving the detector to 2-omega?

Yes, it is possible to analyze a crystal structure without moving the detector to 2-omega, but the results may not be as accurate or comprehensive. 2-omega is the standard angle used in Goniometers for diffraction measurements and is recommended for obtaining the most precise and reliable data.

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