Choice of oscillation range - Revision history

Kay at 20:06, 28 May 2014

2014-05-28T20:06:40Z

← Older revision		Revision as of 22:06, 28 May 2014
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	# preventing reflection overlap at high resolution (see table at end of [[IDXREF.LP]]) - for a given total rotation range, lower oscillation range is better		# preventing reflection overlap at high resolution (see table at end of [[IDXREF.LP]]) - for a given total rotation range, lower oscillation range is better
	# improving the signal-to-noise ratio - lower oscillation range is better (but see below)		# improving the signal-to-noise ratio - lower oscillation range is better (but see below)
	# minimizing the readout noise (should be 2-10 counts per pixel for CCD, and 0 for pixel array detectors) - larger oscillation range is better		# minimizing the readout noise (should be 2-10 counts per pixel for CCD, and 0 for pixel array detectors) - larger oscillation range is better (only for CCD)
	# minimizing the disk space and the readout time - larger oscillation range is better		# minimizing the disk space and the readout time - larger oscillation range is better

Kay at 11:00, 25 June 2012

2012-06-25T11:00:20Z

← Older revision		Revision as of 13:00, 25 June 2012
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	The choice of oscillation range reflects a compromise between conflicting targets - in order of importance:		The choice of oscillation range (=delta-phi for each frame) reflects a compromise between conflicting targets - in order of importance:
	# preventing reflection overlap at high resolution (see table at end of [[IDXREF.LP]]) - for a given total rotation range, lower oscillation range is better		# preventing reflection overlap at high resolution (see table at end of [[IDXREF.LP]]) - for a given total rotation range, lower oscillation range is better
	# ~~optimizing~~ the signal-to-noise ratio - lower oscillation range is better (but see below)		# improving the signal-to-noise ratio - lower oscillation range is better (but see below)
	# minimizing the readout noise (should be 2-10 counts per pixel for CCD, and 0 for pixel array detectors) - larger oscillation range is better		# minimizing the readout noise (should be 2-10 counts per pixel for CCD, and 0 for pixel array detectors) - larger oscillation range is better
	# minimizing the disk space ~~- larger oscillation range is better~~		# minimizing the disk space and the readout time - larger oscillation range is better
	~~# minimizing~~ the readout time - larger oscillation range is better

	The following aspects need to be considered when choosing the oscillation range:		The following aspects need to be considered when choosing the oscillation range:
	* crystal mosaicity: choosing the oscillation range less than (crystal mosaicity / 2) will not further increase the signal-to-noise ratio - see Müller et al (2012) ''Acta Cryst''. '''D68''', 42 ([http://scripts.iucr.org/cgi-bin/paper?S0907444911049833 open access])		* crystal mosaicity: choosing the oscillation range less than (crystal mosaicity / 2) will not further increase the signal-to-noise ratio - see Müller et al (2012) ''Acta Cryst''. '''D68''', 42 ([http://scripts.iucr.org/cgi-bin/paper?S0907444911049833 open access])
	* the maximum oscillation range to prevent angular overlap can be calculated from cell parameters and crystal orientation, and the mosaicity. Specifically, the mosaicity must be ''subtracted'' from the value given in the table at the end of [[IDXREF.LP]] ~~(if~~ the mosaicity is bigger than the table value, of course a positive value for the oscillation range must be chosen, but there ''will'' then be overlaps).		* the maximum oscillation range to prevent angular overlap can be calculated from cell parameters and crystal orientation, and the mosaicity. Specifically, the mosaicity must be ''subtracted'' from the value given in the table at the end of [[IDXREF.LP]] which takes all of this into account. If the mosaicity is bigger than the table value, of course a positive value for the oscillation range must be chosen, but there ''will'' then be overlaps.

	In the absence of mosaicity information (or assuming a mosaicity of 0.3° or less), a reasonable default value for crystals that diffract to 2A resolution or less, and longest (primitive!) unit cell axis of ~~150A~~ or less is, in my opinion (and as suggested in publications by Phil Evans and Jim Pflugrath which should be referenced here:		In the absence of mosaicity information (or assuming a mosaicity of 0.3° or less), a reasonable default value for crystals that diffract to 2Å resolution or less, and have longest (primitive!) unit cell axis of 150Å or less is, in my opinion and as suggested in publications by Phil Evans and Jim Pflugrath (which should be referenced here ...):
	* around 0.25-0.5° for CCD detectors		* around 0.25-0.5° for CCD detectors
	* around 0.1° for the Pilatus detector		* around 0.1° for the Pilatus detector

Kay: moved Choice of OSCILLATION RANGE to Choice of oscillation range

2012-06-24T18:45:15Z

moved Choice of OSCILLATION RANGE to Choice of oscillation range

← Older revision	Revision as of 20:45, 24 June 2012
(No difference)

Kay at 18:43, 24 June 2012

2012-06-24T18:43:18Z

← Older revision		Revision as of 20:43, 24 June 2012
Line 1:		Line 1:
	The choice of oscillation range reflects a compromise between conflicting targets - in order of importance:		The choice of oscillation range reflects a compromise between conflicting targets - in order of importance:
	# preventing reflection overlap at high resolution (see table at end of [[IDXREF.LP]]) - lower oscillation range is better		# preventing reflection overlap at high resolution (see table at end of [[IDXREF.LP]]) - for a given total rotation range, lower oscillation range is better
	# optimizing the signal-to-noise ratio - lower oscillation range is better (but see below)		# optimizing the signal-to-noise ratio - lower oscillation range is better (but see below)
	# minimizing the readout noise (should be 2-10 counts per pixel for CCD, and 0 for pixel array detectors) - larger oscillation range is better		# minimizing the readout noise (should be 2-10 counts per pixel for CCD, and 0 for pixel array detectors) - larger oscillation range is better
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	The following aspects need to be considered when choosing the oscillation range:		The following aspects need to be considered when choosing the oscillation range:
	# crystal mosaicity: choosing the oscillation range less than (crystal mosaicity / 2) will not further increase the signal-to-noise ratio - see Müller et al (2012) ''Acta Cryst''. '''D68''', 42 ([~~open access~~ http://scripts.iucr.org/cgi-bin/paper?S0907444911049833])		* crystal mosaicity: choosing the oscillation range less than (crystal mosaicity / 2) will not further increase the signal-to-noise ratio - see Müller et al (2012) ''Acta Cryst''. '''D68''', 42 ([http://scripts.iucr.org/cgi-bin/paper?S0907444911049833 open access])
	# the maximum oscillation range to prevent angular overlap can be calculated from cell parameters and crystal orientation, and the mosaicity. Specifically, the mosaicity must be ''subtracted'' from the value given in the table at the end of [[IDXREF.LP]] (if the mosaicity is bigger than the table value, of course a positive value for the oscillation range must be chosen, but there ''will'' then be overlaps).		* the maximum oscillation range to prevent angular overlap can be calculated from cell parameters and crystal orientation, and the mosaicity. Specifically, the mosaicity must be ''subtracted'' from the value given in the table at the end of [[IDXREF.LP]] (if the mosaicity is bigger than the table value, of course a positive value for the oscillation range must be chosen, but there ''will'' then be overlaps).

	A reasonable default value for crystals that diffract to 2A resolution or less, ~~have a mosaicity of 0.3° or less~~ and longest (primitive!) unit cell axis of 150A or less is, in my opinion:		In the absence of mosaicity information (or assuming a mosaicity of 0.3° or less), a reasonable default value for crystals that diffract to 2A resolution or less, and longest (primitive!) unit cell axis of 150A or less is, in my opinion (and as suggested in publications by Phil Evans and Jim Pflugrath which should be referenced here:
	* around 0.25-0.5° for CCD detectors		* around 0.25-0.5° for CCD detectors
	* around 0.1° for the Pilatus detector		* around 0.1° for the Pilatus detector

Kay at 18:29, 24 June 2012

2012-06-24T18:29:44Z

← Older revision		Revision as of 20:29, 24 June 2012
Line 1:		Line 1:
	The choice of oscillation range reflects a compromise between conflicting targets: preventing reflection overlap at high resolution (see table at end of [[IDXREF.LP]]), optimizing the signal-to-noise ratio~~, minimizing the disk space, and~~ minimizing the readout ~~time~~ (~~less important with~~ CCD and pixel detectors)~~. It~~ is ~~also influenced by~~ the ~~type of detector used.~~		The choice of oscillation range reflects a compromise between conflicting targets - in order of importance:
			# preventing reflection overlap at high resolution (see table at end of [[IDXREF.LP]]) - lower oscillation range is better
			# optimizing the signal-to-noise ratio - lower oscillation range is better (but see below)
			# minimizing the readout noise (should be 2-10 counts per pixel for CCD, and 0 for pixel array detectors) - larger oscillation range is better
			# minimizing the disk space - larger oscillation range is better
			# minimizing the readout time - larger oscillation range is better

	The following aspects need to be considered when choosing the oscillation range:		The following aspects need to be considered when choosing the oscillation range:
	# crystal mosaicity: choosing the oscillation range less than (crystal mosaicity / 2) will not further increase the signal-to-noise ratio		# crystal mosaicity: choosing the oscillation range less than (crystal mosaicity / 2) will not further increase the signal-to-noise ratio - see Müller et al (2012) ''Acta Cryst''. '''D68''', 42 ([open access http://scripts.iucr.org/cgi-bin/paper?S0907444911049833])
	# the maximum oscillation range to prevent angular overlap can be calculated from cell parameters and crystal orientation, and the mosaicity. Specifically, the mosaicity must be ''subtracted'' from the value given in the table at the end of [[IDXREF.LP]] (if the mosaicity is bigger than the ~~given~~ value, of course a positive value must be chosen, but there ''will'' then be overlaps).		# the maximum oscillation range to prevent angular overlap can be calculated from cell parameters and crystal orientation, and the mosaicity. Specifically, the mosaicity must be ''subtracted'' from the value given in the table at the end of [[IDXREF.LP]] (if the mosaicity is bigger than the table value, of course a positive value for the oscillation range must be chosen, but there ''will'' then be overlaps).

	A reasonable default value for crystals that diffract to 2A resolution or less, have a mosaicity of 0.3° or less and longest (primitive!) unit cell axis of 150A or less is, in my opinion:		A reasonable default value for crystals that diffract to 2A resolution or less, have a mosaicity of 0.3° or less and longest (primitive!) unit cell axis of 150A or less is, in my opinion:
	* around 0.5° for CCD detectors		* around 0.25-0.5° for CCD detectors
	* around 0.1° for the Pilatus detector		* around 0.1° for the Pilatus detector

Kay: Created page with "The choice of oscillation range reflects a compromise between conflicting targets: preventing reflection overlap at high resolution (see table at end of IDXREF.LP), optimi..."

2012-06-22T00:31:36Z

Created page with "The choice of oscillation range reflects a compromise between conflicting targets: preventing reflection overlap at high resolution (see table at end of IDXREF.LP), optimi..."

New page

The choice of oscillation range reflects a compromise between conflicting targets: preventing reflection overlap at high resolution (see table at end of [[IDXREF.LP]]), optimizing the signal-to-noise ratio, minimizing the disk space, and minimizing the readout time (less important with CCD and pixel detectors). It is also influenced by the type of detector used.

The following aspects need to be considered when choosing the oscillation range:
# crystal mosaicity: choosing the oscillation range less than (crystal mosaicity / 2) will not further increase the signal-to-noise ratio
# the maximum oscillation range to prevent angular overlap can be calculated from cell parameters and crystal orientation, and the mosaicity. Specifically, the mosaicity must be ''subtracted'' from the value given in the table at the end of [[IDXREF.LP]] (if the mosaicity is bigger than the given value, of course a positive value must be chosen, but there ''will'' then be overlaps).

A reasonable default value for crystals that diffract to 2A resolution or less, have a mosaicity of 0.3° or less and longest (primitive!) unit cell axis of 150A or less is, in my opinion:
* around 0.5° for CCD detectors
* around 0.1° for the Pilatus detector