On Dec 6, 2018, at 2:36 PM, Anthony Case <tonycase@cfa.harvard.edu> wrote:

Since we were discussing the possibility of side-penetrators yesterday, I went back and looked at the solid model for the instrument to see how much shielding is on the sides of the detectors.  There are a couple images attached.  The outer wall of the telescope housing is 0.2 cm, and the added shielding was essentially a C-channel with 0.2cm walls that was bolted onto the outside of the telescope housing.  So for normally incident particles there is just the end-caps which are 0.076 cm (which gives us our usual ~10-12 MeV protons required to get into the instrument).  And for side-penetrators to get through a 0.4cm thick wall requires about 27.5 MeV.  That neglects the detector frame, which could add another >0.5 cm.  Of course any particular particle's path through all of this junk is fairly complex, but roughly speaking 30-50 MeV seems like the minimum energy a side-penetrating proton would need to reach the detector.

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Anthony Case

Astrophysicist

High Energy Astrophysics Division (HEAD/SSXG)

Center for Astrophysics | Harvard & Smithsonian

Cell: (617) 304 0768

60 Garden Street | MS 58 | Cambridge, MA 02138

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