[Crater-team] CRaTER Side Shielding

Wed Dec 26 15:06:06 EST 2018

Hello—

                Sorry, I said I was going to get to this either in the hotel at or on the plane returning from the AGU meeting.  I attach six plots, one for each of the six detectors, showing the response of each to protons coming in at each energy and angle.  The angle is averaged over all azimuths as if the sensor was cylindrically symmetrical, and there is no obstruction from the spacecraft in the simulation; however, enough of the solid angle is covered by open space in reality that this should not make all that much difference quantitatively, and none qualitatively.  This set of plots, which includes the D5 and D6 plots I sent during the discussion about possible neutron or gamma response some months ago, is based on the response simulations that I did in 2010 using Geant4 version 9.3; the single-detector proton response is not likely to change much when I redo them with version 10.5 (that is mainly aimed at understanding shrapnel and “scruff” in multi-detector coincidences).

The colorscale is the logarithm of the effective area of that detector’s singles rate (with flight thresholds applied) for protons arriving at the given energy (X axis) from the given angle off the D6 normal (Y axis), with the white color denoting the full nominal area (9.6 cm^2) of each detector.  You can see that D3 and D4 have some off-axis leakage down to 50 MeV or so, and that D4 in particular has a small sneak path down to about 20 MeV.  Let me know if you need this integrated over angle as a curve vs. energy or something.

Happy new year—
--Mark Looper

Mark D. Looper
Space Sciences Department
The Aerospace Corporation
M/S M2-260
P.O. Box 92957
Los Angeles, CA 90009-2957
Mobile: 310-529-3406
Voicemail: 310-336-6302

From: Anthony Case <tonycase at cfa.harvard.edu>
Date: Thursday, December 6, 2018 at 11:12 AM
To: Mark D Looper <mark.d.looper at aero.org>
Cc: Harlan <spence at guero.sr.unh.edu>, "crater-team at lists.sr.unh.edu" <crater-team at lists.sr.unh.edu>
Subject: Re: [Crater-team] CRaTER Side Shielding

Mark,

In comparing with GOES, we were curious about he response to >50 MeV protons, since GOES has a data product that is integral flux above 50 MeV.  Specifically, we were wondering if 50 MeV protons could make it through the side of the instrument into D3/D4. In looking at the mechanical design, it seemed like there were some paths where protons with energies less than 50 MeV (maybe even down to 30 MeV) could make it through to the detector.  Do you have model runs that would answer that question?

Tony

---------------------------------------------------------------------

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

On Thu, Dec 6, 2018 at 4:02 PM Mark D Looper <mark.d.looper at aero.org<mailto:mark.d.looper at aero.org>> wrote:
Hello—

                I’m sorry I missed the call yesterday because of Aerospace AGU dry runs at the same time.  What is the specific question about side penetrators that was asked?  I can dig response functions vs. energy and angle out of my 2010 sensor-head simulations, though I’ll probably have to do it from my hotel room at AGU.  I do intend to port the code to the current version of Geant4 and re-run it, for use in the paper after the one containing the work I’m summarizing on the AGU poster, but for protons the results won’t change much.

--Mark Looper

Mark D. Looper
Space Sciences Department
The Aerospace Corporation
M/S M2-260
P.O. Box 92957
Los Angeles, CA 90009-2957
Mobile: 310-529-3406
Voicemail: 310-336-6302

From: Crater-team <crater-team-bounces at lists.sr.unh.edu<mailto:crater-team-bounces at lists.sr.unh.edu>> on behalf of Harlan Spence <spence at guero.sr.unh.edu<mailto:spence at guero.sr.unh.edu>>
Date: Thursday, December 6, 2018 at 10:53 AM
To: Anthony Case <tonycase at cfa.harvard.edu<mailto:tonycase at cfa.harvard.edu>>
Cc: "crater-team at lists.sr.unh.edu<mailto:crater-team at lists.sr.unh.edu>" <crater-team at lists.sr.unh.edu<mailto:crater-team at lists.sr.unh.edu>>
Subject: Re: [Crater-team] CRaTER Side Shielding

I love it when a plan comes together.  We meant to do that!  I guess it was in the instrument paper for a reason….too many years now.
________________________________
Harlan E. Spence
Director, Institute for the Study of Earth,
   Oceans, & Space and Prof. of Physics
Morse Hall, Room 306
University of New Hampshire
8 College Road
Durham, NH 03824-3525

Phone: 603-862-0322
Fax:   603-862-1915

http://www.eos.unh.edu/Faculty/Spence
________________________________

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

<image.png>

<image.png>

---------------------------------------------------------------------
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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