- \n
- 5e12 ph\/s (Kirby-2016<\/a>), beam size 130 x 250 \u00b5m FWHM, 12 keV, Australian synchrotron SAXS\/WAXS<\/a>. That translates to 1.54e14 ph\/s\/mm^2<\/li>\n
- ESRF’s flagship (or battleship) SAXS beamline ID02<\/a> states a flux on the order of 1e14 ph\/s over a beam of 200 x 400 \u00b5m at 12.4 keV. That translates to 1.25e15 ph\/s\/mm^2<\/li>\n
- Diamond I22<\/a> gives a flux of 6e12 with a beam of 320 x 80 \u00b5m at 12.4 keV, translating to 1.95e14 ph\/s\/mm^2<\/li>\n
- MAX-lab’s I711<\/a> in 2009 (Knaapila-2009<\/a>) had a flux of 4e10 in a beam of 0.37 x 0.37 mm, translating to 2.92e11 ph\/s\/mm^2, although they may since have improved a bit, since their website now claims “>1e11 ph\/s”.<\/li>\n
- SLS’s cSAXS<\/a> states 1e12 ph\/s at 11.2 keV, using a beam of 0.5 x 0.5 mm, translating to 4e12 ph\/s\/mm^2.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<\/div>\n
So all of the beamlines at large synchrotrons seem to be delivering pretty much the same amount of photons, give or take an order of magnitude. How about laboratory instruments?<\/p>\n
This information is a bit harder to find. Even papers with very interesting titles like “SAXS instruments with slit collimation: investigation of resolution and flux” (Fritz-2005<\/a>) contain only relative fluxes. Jan-skov Pedersen has been presenting about flux numbers for his new metaljet-based SAXS, but as far as I can see, that is not published. Here’s what I can find:<\/p>\n
- \n
- Andras Wacha in 2014 published<\/a> a value for their CREDO<\/a> pinhole-SAXS with microfocus source: 165000 ph\/s at 8 keV, with a 0.7mm dia. beam at the sample position, translating to 4.3e5 ph\/s\/mm^2<\/li>\n
- Jan-skov Pedersen published<\/a> in 2004 a value of 1.9e7 ph\/s at 8 keV for the total beam in his instrument, although the beam diameter) at the sample position is quite unclear. Assuming 0.5 mm^2, this translates to 9.7e7 ph\/s\/mm^2. He has since upgraded to a metaljet, which may have increased that by another order of magnitude.<\/li>\n
- Linda Br\u00fctzel in 2016 published<\/a> a rate of 2.5e6 ph\/s in a beam at the sample position of 1.2 x 1.2 mm (microfocus source), which translates to 1.7e6 ph\/s\/mm^2.<\/li>\n<\/ul>\n
So, some differences there, indicating a difference between labs and synchrotrons of about 1 million. However, we can also go one step further with some practical tests on our instruments.<\/p>\n
Practical comparison<\/h3>\n
Andy Smith at I22 kindly provided us with recent information on his instrument for one of our experiments, with a flux on the sample of about 2.1e12 ph\/s in a beam of 0.1 x 0.3 mm, translating to 7e13 ph\/s\/mm^2. That is well in line with the website claims above.<\/p>\n
We did a test on our SAXSess recently, with a tube source and (line) focusing optics. We got 900000 ph\/s on an area of approximately 0.75 x 0.2 mm, translating to 6e6 ph\/s\/mm^2.<\/p>\n
During the CEA visit<\/a>, we also automatically got information on the flux of that microfocus source instrument, which delivered 2.9 ph\/s in a beam of 1.2 x 0.8 mm, which is 3e7 ph\/s\/mm^2.<\/p>\n
Conclusion<\/h3>\n
![\"Comparison](\"http:\/\/www.lookingatnothing.com\/wp-content\/uploads\/2017\/04\/Summary-300x182.png\")
<\/a>Figure 1: Comparison between lab and synchrotron flux densities. Click to enlarge.<\/figcaption><\/figure>\n The result is shown in Figure 1, demonstrating there is not just a difference of a million in flux density, but up to a factor of 1e10 between the different instruments! That is an enormous difference. However, one lab instrument in your institute is worth 10 inaccessible synchrotron instruments: If you have the time, and you have a well-optimized lab instrument, you can collect data that rivals the best synchrotrons. Measure overnight, or over the week-end, throughout the year, and take the time to fine-tune those data corrections and sample conditions to get that damn fine quality.<\/p>\n
If, however, you find yourself with a (small) sample that changes rapidly over time, then it is good to know you can go faster. Much, much faster: 10 orders of magnitude, to be precise. And that’s when you head to the synchrotron!<\/p>\n","protected":false},"excerpt":{"rendered":"
- Jan-skov Pedersen published<\/a> in 2004 a value of 1.9e7 ph\/s at 8 keV for the total beam in his instrument, although the beam diameter) at the sample position is quite unclear. Assuming 0.5 mm^2, this translates to 9.7e7 ph\/s\/mm^2. He has since upgraded to a metaljet, which may have increased that by another order of magnitude.<\/li>\n
- ESRF’s flagship (or battleship) SAXS beamline ID02<\/a> states a flux on the order of 1e14 ph\/s over a beam of 200 x 400 \u00b5m at 12.4 keV. That translates to 1.25e15 ph\/s\/mm^2<\/li>\n