{"id":867,"date":"2020-03-11T11:02:54","date_gmt":"2020-03-11T15:02:17","guid":{"rendered":"http:\/\/www.nuclearphysicslab.com\/npl\/?page_id=867"},"modified":"2020-03-18T20:28:33","modified_gmt":"2020-03-19T00:28:33","slug":"cosmogenic-be-7","status":"publish","type":"page","link":"http:\/\/www.nuclearphysicslab.com\/npl\/npl-home\/spectroscopy\/gamma-ray-spectroscopy\/cosmogenic-be-7\/","title":{"rendered":"Cosmogenic Be-7"},"content":{"rendered":"\n

Author: Tim<\/em><\/p>\n\n\n\n

On March 1, 2020 I repeated an experiment that I ran a few years back (~7 years ago). In the present experiment, I’ve run a high-volume air sampler for 2 hours on the back deck. I then took a long “live time” background count (4 days or 96 hours or 345,600 seconds) on my 20% HPGe in the low background shield while I simultaneously let the filter paper “cool down” – letting all the radon daughters decay. Then after the 4-day Background count, I counted the filter paper on the HPGe over the next 4 days. All of the radon daughters products are clearly gone. At the end of 8 days, I subtract the 4-day background from the 4-day filter paper spectrum, and see what is left. There is only 1 line, and that is of Be-7 at 478keV.<\/p>\n\n\n\n

After the first 2-hour air sample, I took a second 2-hour air sample under identical conditions, and I repeated the process with my 50% HPGe, but that is in a higher radon-background environment<\/p>\n\n\n\n

Here are the photos of all the experiment and the analysis results.<\/p>\n\n\n\n

\"\"<\/a>
The Staplex high volume air sampler<\/figcaption><\/figure>\n\n\n\n
\"\"<\/a>
The Staplex filter paper used in this experiment<\/figcaption><\/figure>\n\n\n\n
\"\"<\/a>
The volume of air moved during the sampling.<\/figcaption><\/figure>\n\n\n\n
\"\"<\/a>
The outdoors sample collect scene.<\/figcaption><\/figure>\n\n\n\n
\"\"<\/a>
Tim’s 20%, 1.8keV FWHM HPGe in its low-background shield.<\/figcaption><\/figure>\n\n\n\n
\"\"<\/a>
Filter paper sample placement on HPGe.<\/figcaption><\/figure>\n\n\n\n
\"\"<\/a>
Sample placement is filter paper folded up and place into a plastic petri dish.<\/figcaption><\/figure>\n\n\n\n
\"\"<\/a>
Both background and filter paper spectra.<\/figcaption><\/figure>\n\n\n\n
\"\"<\/a>
Both background and filter paper spectra in log scale.<\/figcaption><\/figure>\n\n\n\n
\"\"<\/a>
Background subtracted filter paper spectrum reveals a single peak.<\/figcaption><\/figure>\n\n\n\n
\"\"<\/a>
We identify that single peak as Be-7 cosmogenically created in our upper atmosphere.<\/figcaption><\/figure>\n\n\n\n

Performing an identical analysis with my other HPGe. This detector is a 50% relative efficiency detector (the above is 20%), however, this detector while shielded by a lead castle, it in a higher background from my basement’s radon (which of course is a variable background).<\/p>\n\n\n\n

The second filter paper sample was similarly let to “cool off” for four days. It was then counted for four days. Then I took a four-day background count. Sure enough, the Be-7 peak presented itself:<\/p>\n\n\n\n

\"\"<\/a>
Region of Interest highlighted in red, shows the Be-7 peak at 478keV.<\/figcaption><\/figure>\n\n\n\n
\"\"<\/a>
Region of Interest highlighted in red, shows the Be-7 peak at 478keV, which the nuclide library correctly identifies.<\/figcaption><\/figure>\n\n\n\n

It is interesting to note, despite the higher background, that still number of net counts was roughly double for this filter paper, taking advantage of the higher detector efficiency.<\/p>\n\n\n\n

\"\"<\/a>
Background and background subtracted spectra compared in PeakEasy. The large peak to right of the Be-7 peak is the 511keV annihilation peak.<\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"

Author: Tim On March 1, 2020 I repeated an experiment that I ran a few years back (~7 years ago). In the present experiment, I’ve run a high-volume air sampler for 2 hours on the back deck. I then took a long “live time” background count (4 days or 96 hours or 345,600 seconds)…<\/p>\n

Read More Read More<\/span><\/a><\/p>\n","protected":false},"author":3,"featured_media":852,"parent":25,"menu_order":2,"comment_status":"closed","ping_status":"closed","template":"","meta":{"advanced-sidebar-menu\/link-title":"","advanced-sidebar-menu\/exclude-page":false},"categories":[45,5,37],"tags":[],"_links":{"self":[{"href":"http:\/\/www.nuclearphysicslab.com\/npl\/wp-json\/wp\/v2\/pages\/867"}],"collection":[{"href":"http:\/\/www.nuclearphysicslab.com\/npl\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"http:\/\/www.nuclearphysicslab.com\/npl\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"http:\/\/www.nuclearphysicslab.com\/npl\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"http:\/\/www.nuclearphysicslab.com\/npl\/wp-json\/wp\/v2\/comments?post=867"}],"version-history":[{"count":10,"href":"http:\/\/www.nuclearphysicslab.com\/npl\/wp-json\/wp\/v2\/pages\/867\/revisions"}],"predecessor-version":[{"id":2244,"href":"http:\/\/www.nuclearphysicslab.com\/npl\/wp-json\/wp\/v2\/pages\/867\/revisions\/2244"}],"up":[{"embeddable":true,"href":"http:\/\/www.nuclearphysicslab.com\/npl\/wp-json\/wp\/v2\/pages\/25"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/www.nuclearphysicslab.com\/npl\/wp-json\/wp\/v2\/media\/852"}],"wp:attachment":[{"href":"http:\/\/www.nuclearphysicslab.com\/npl\/wp-json\/wp\/v2\/media?parent=867"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.nuclearphysicslab.com\/npl\/wp-json\/wp\/v2\/categories?post=867"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.nuclearphysicslab.com\/npl\/wp-json\/wp\/v2\/tags?post=867"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}