Nov 2008 beamrun, day 3
31/10/08 18:31 Filed in: Work Experiments
Today has been frustrating as well. We’ve switched to looking at Zinc oxide surfaces while we consider what’s going on with my gold samples. However, things have not gone as planned. Getting a properly prepared surface on a metal oxide is considerably more difficult (in my opinion) than my metal crystals. That struggle has taken quite a bit of effort.
For a while I thought I’d found something really cool. I had weak diffraction peaks at forbidden locations which is (sometimes) and indication that there’s a small ordered surface layer or adsorbate. Sadly in this case it was not that, rather it was just higher energy x-rays playing havoc.
We use a device called a “mono-chromator” to select out a particular wavelength of light. In principle it works great. It uses crystal lattices to diffract the initial beam. Only photons with the correct wavelength make it through the reflections from the crystals. However there is a problem... It can’t tell the difference between photons of the correct wavelength and photons with only half that wavelength and other integer fractions of smaller and smaller wavelength x-rays. These phonies get through the monochromator and also hit our samples. Now, the real problem is that the same mechanism that let them through the monochromator also diffractors them up at times into our detector. The detector can be set to not count them, but very often they can get counted anyways as things are not perfect. So instead of finding something new, all I really saw for an hour were peaks due to these rogue photons of shorter wavelength.
Things like that happen in science. It’s not an easy process. Often at first when you think you’ve found something interesting it later turns out to be some artifact of something else. The best you can really hope and aim for is to make fewer of those mistakes (though they’ll happen) and to correct them early before you waste entire experiments on them.
No one said this would be easy... In fact, we often say just the opposite. If it was easy, someone else would’ve done it.
For a while I thought I’d found something really cool. I had weak diffraction peaks at forbidden locations which is (sometimes) and indication that there’s a small ordered surface layer or adsorbate. Sadly in this case it was not that, rather it was just higher energy x-rays playing havoc.
We use a device called a “mono-chromator” to select out a particular wavelength of light. In principle it works great. It uses crystal lattices to diffract the initial beam. Only photons with the correct wavelength make it through the reflections from the crystals. However there is a problem... It can’t tell the difference between photons of the correct wavelength and photons with only half that wavelength and other integer fractions of smaller and smaller wavelength x-rays. These phonies get through the monochromator and also hit our samples. Now, the real problem is that the same mechanism that let them through the monochromator also diffractors them up at times into our detector. The detector can be set to not count them, but very often they can get counted anyways as things are not perfect. So instead of finding something new, all I really saw for an hour were peaks due to these rogue photons of shorter wavelength.
Things like that happen in science. It’s not an easy process. Often at first when you think you’ve found something interesting it later turns out to be some artifact of something else. The best you can really hope and aim for is to make fewer of those mistakes (though they’ll happen) and to correct them early before you waste entire experiments on them.
No one said this would be easy... In fact, we often say just the opposite. If it was easy, someone else would’ve done it.