Intrinsic fluence non-uniformity in D3He backlit proton radiography
Author(s)
Johnson, Timothy M.; Shan, J.; Kishimori, R.; Cufari, M.J.; Adrian, Partick J.; Buschmann, B.; Chang, C.W.; Dannhoff, S.G.; DeVault, A.; Evans, Tucker E.; Foo, B.; Kunimune, Justin H.; Lawrence, Y.; Pearcy, Jacob A.; Reichelt, Benjamin L.; Russell, L.; Sutcliffe, G.D.; Vanderloo, N.L.; Vargas, J.; Wink, Christopher W.; Gatu Johnson, Maria; Séguin, Frederick H.; Petrasso, Richard D.; Frenje, Johan A.; Li, Chi-Kang; ... Show more Show less
Download24ja068_full.pdf (430.4Kb)
Metadata
Show full item recordAbstract
Proton radiography is an essential diagnostic for studying magnetic fields in high energy density physics experiments. Protons are born in a fusion implosion, traverse the plasma, and are detected on CR-39 solid state nuclear track detectors. Here, it is shown that there is an intrinsic non-uniformity in ∼ 15 MeV D3He proton radiography data. The increasing angle between the proton trajectory and the center of the detector results in the proton traveling through more detector stack material. As the protons travel through more material and lose energy, the proton energy spectrum gets wider. Protons at the lower end of the spectrum can therefore be lost. The nominal filtering results in protons being ranged out at large angle, causing the intrinsic non-uniformity. This angular effect is confirmed with both OMEGA experiments and Geant4 simulations. It is found that reducing the filtering between the pieces of CR-39 in the detector stack mitigates this effect. Results from accelerator experiments show that this reduced filtering does not impact the detection efficiency of the CR-39. Accounting for this intrinsic fluence non-uniformity is essential for magnetic field reconstruction techniques using proton radiographs.
Description
Submitted for publication in Review of Scientific Instruments
Date issued
2024-04Department
Massachusetts Institute of Technology. Plasma Science and Fusion CenterJournal
Review of Scientific Instruments
Publisher
AIP
Other identifiers
24ja068