Re: Noise in XRD
I think you need to close the windows to reduce the Background On Apr 25, 2016 20:52, "Peter Stephens" wrote: > Use of a chopper won't improve on the limit imposed by shot noise. You're > probably better off chasing down the cause of the low angle background. > > > ** > Peter W. Stephens > Professor, Department of Physics and Astronomy > Associate Dean for Research and Facilities, College of Arts and Sciences > Stony Brook University > (631) 632-8156 > http://mini.physics.sunysb.edu/~pstephens > Please update your records to my new email: peter.steph...@stonybrook.edu > > On Mon, Apr 25, 2016 at 1:02 PM, Shay Tirosh wrote: > >> Thank you all who answered my question. >> >> I would like to add in this frame: >> >> Are there attempts to use chopping X-ray source coupled to lock-in >> amplifier to dump noise further? >> I would use this technique specifically at low angles where the detector >> tends to saturate with background light. >> >> Thanks >> >> Shay >> >> -- >> _ >> >> Dr. Shay Tirosh >> Institute for Nanotechnology & Advanced Materials >> Bar Ilan University >> Ramat Gan, 52900 >> Israel >> Phone: +972-(0)30-531-7320 >> Mobile: +972-(0)54-8834533 >> Email: stiro...@gmail.com >> _ >> >> ++ >> Please do NOT attach files to the whole list > > >> Send commands to eg: HELP as the subject with no body >> text >> The Rietveld_L list archive is on >> http://www.mail-archive.com/rietveld_l@ill.fr/ >> ++ >> >> >> > > > > ++ > Please do NOT attach files to the whole list > > Send commands to eg: HELP as the subject with no body > text > The Rietveld_L list archive is on > http://www.mail-archive.com/rietveld_l@ill.fr/ > ++ > > > ++ Please do NOT attach files to the whole list Send commands to eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++
Re: Noise in XRD
Use of a chopper won't improve on the limit imposed by shot noise. You're probably better off chasing down the cause of the low angle background. ** Peter W. Stephens Professor, Department of Physics and Astronomy Associate Dean for Research and Facilities, College of Arts and Sciences Stony Brook University (631) 632-8156 http://mini.physics.sunysb.edu/~pstephens Please update your records to my new email: peter.steph...@stonybrook.edu On Mon, Apr 25, 2016 at 1:02 PM, Shay Tirosh wrote: > Thank you all who answered my question. > > I would like to add in this frame: > > Are there attempts to use chopping X-ray source coupled to lock-in > amplifier to dump noise further? > I would use this technique specifically at low angles where the detector > tends to saturate with background light. > > Thanks > > Shay > > -- > _ > > Dr. Shay Tirosh > Institute for Nanotechnology & Advanced Materials > Bar Ilan University > Ramat Gan, 52900 > Israel > Phone: +972-(0)30-531-7320 > Mobile: +972-(0)54-8834533 > Email: stiro...@gmail.com > _ > > ++ > Please do NOT attach files to the whole list > > Send commands to eg: HELP as the subject with no body > text > The Rietveld_L list archive is on > http://www.mail-archive.com/rietveld_l@ill.fr/ > ++ > > > -- ++ Please do NOT attach files to the whole list Send commands to eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++
Noise in XRD
Thank you all who answered my question. I would like to add in this frame: Are there attempts to use chopping X-ray source coupled to lock-in amplifier to dump noise further? I would use this technique specifically at low angles where the detector tends to saturate with background light. Thanks Shay -- _ Dr. Shay Tirosh Institute for Nanotechnology & Advanced Materials Bar Ilan University Ramat Gan, 52900 Israel Phone: +972-(0)30-531-7320 Mobile: +972-(0)54-8834533 Email: stiro...@gmail.com _ ++ Please do NOT attach files to the whole list Send commands to eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++
Re: Noise in XRD
You are referring to the different sources of electronic noise <https://en.wikipedia.org/wiki/Noise_(electronics)> produced by your detector. Frequency analysis of that noise (white noise vs noise at particular frequencies) might tell you something about your detector, but not about your sample. Here I assume you are talking about counting noise, not background due to imperfect crystallinity or sample environment. Hopefully most noise in a diffraction pattern will simply be the statistical noise in counting individual photons or neutrons. With low counts that will indeed have different distributions; in the background, with asymmetric Poisson statistics with a cut-off at zero counts, and in strong peaks, with a transition to a symmetrical normal distribution. Fitting (smoothing), and especially Rietveld fitting which constrains the positions and relative intensities of the peaks, will obtain the best estimate of even weak peaks, provided you have a physically realistic model for the scattering and not too much correlation between parameters. For low (neutron) counts, Rietveld assigned weights inversely proportional to the count, which can be justified by statistics, and which helps prevent the important information in weak or absent peaks being swamped by the fit to strong peaks. There have been attempts to shorten scanning time by spending more time on weak peaks, which are "noisier", but in practice that is difficult, if as usual you have a multi-detector that collects the whole pattern at the same time. But weak or absent peaks are indeed more important than strong peaks. I am not sure that I have answered your questions, or even if I have correctly understood them :-) But then you didn't receive many other answers either. Alan. On 24 April 2016 at 19:16, Shay Tirosh wrote: > Dear Rietvelders > > Does the noise in XRD tell something? > > Correct me if I'm wrong but I think the noise on a peak is different then > the noise in baseline. > If this is correct then is there a possibility to identify broad peaks or > very small peaks? using some noise analysis. > Can noise analysis help in better smoothing or fitting? > Distinguishing between different noise types at baseline vs peak (Shot > noise, flicker noise <https://en.wikipedia.org/wiki/Flicker_noise> and > Johnson–Nyquist > noise <https://en.wikipedia.org/wiki/Johnson%E2%80%93Nyquist_noise> > ) may leads to shortening the scanning time, or even to help finding the > appropriate fitting function. > > Please comment > > Shay > > -- > _ > > Dr. Shay Tirosh > Institute for Nanotechnology & Advanced Materials > Bar Ilan University > Ramat Gan, 52900 > Israel > Phone: +972-(0)30-531-7320 > Mobile: +972-(0)54-8834533 > Email: stiro...@gmail.com > _ > > ++ > Please do NOT attach files to the whole list > > Send commands to eg: HELP as the subject with no body > text > The Rietveld_L list archive is on > http://www.mail-archive.com/rietveld_l@ill.fr/ > ++ > > > -- __ * Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE * +33.476.98.41.68 http://www.NeutronOptics.com/hewat __ ++ Please do NOT attach files to the whole list Send commands to eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++
Noise in XRD
Dear Rietvelders Does the noise in XRD tell something? Correct me if I'm wrong but I think the noise on a peak is different then the noise in baseline. If this is correct then is there a possibility to identify broad peaks or very small peaks? using some noise analysis. Can noise analysis help in better smoothing or fitting? Distinguishing between different noise types at baseline vs peak (Shot noise, flicker noise <https://en.wikipedia.org/wiki/Flicker_noise> and Johnson–Nyquist noise <https://en.wikipedia.org/wiki/Johnson%E2%80%93Nyquist_noise> ) may leads to shortening the scanning time, or even to help finding the appropriate fitting function. Please comment Shay -- _ Dr. Shay Tirosh Institute for Nanotechnology & Advanced Materials Bar Ilan University Ramat Gan, 52900 Israel Phone: +972-(0)30-531-7320 Mobile: +972-(0)54-8834533 Email: stiro...@gmail.com _ ++ Please do NOT attach files to the whole list Send commands to eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++
