Figure 1

(a) Side view of the experimental setup drawn schematically. (b) A photograph of the hemicylindrical target, of $350\mu \mathrm{m}$ radius of curvature, fielded in the experiment.Reuse & Permissions

Figure 2

Proton beam profiles obtained experimentally for (a) reference flat foil and (b) hemicylindrical targets for two different energies. The blank areas in the dose distribution in Fig. 2a correspond to horizontal slots cut in the RCFs in order to allow the proton beam to be diagnosed by complementary Thompson spectrometers. (c) and (d) are the schematics showing the proton beam longitudinal envelope and observed beam transverse profiles at different planes (viz., at meshes and the RCF) for flat foil and hemicylindrical targets, respectively.Reuse & Permissions

Figure 3

(a) Data points showing beam transverse size at the plane of mesh-2 over focusing (black squares) and nonfocusing (blue circles) planes of the hemicylindrical target. (b) Graph showing beam VS positions for different energies from the hemicylindrical target for focusing (black squares) and nonfocusing (black circles) planes; reference flat foil target across two orthogonal planes (blue diamonds and triangles). The thick gray line illustrates that the positions of the VS for the nonfocusing plane of the hemicylindrical target remain in line with the characteristics of the planar reference foil case. Black dashed and solid curves in both (a) and (b) represent the respective results obtained from the simple geometrical curvature modeling for the hemicylindrical target by considering lower and upper limit profiles, respectively, of proton source sizes shown in Fig. 4c.Reuse & Permissions

Figure 4

(a) Schematic (not to scale) showing nonballistic (upper half) and ballistic (lower half) emergence of proton beamlets from an expanding ion front of Gaussian and parabolic shapes, respectively. The arrows show the direction of local normal to the ion fronts. (b) Half cone divergence angle of the proton beam from $25\mu \mathrm{m}$ thick Al target (black squares), from $250\mu \mathrm{m}$ thick (red diamonds) plain foil, and across the nonfocusing plane of the hemicylindrical target (black circles). (c) Proton source sizes $r(E)$ for different energies obtained from the reference shot. It is estimated by extrapolating a linear beam envelope, defined by the beam size at the mesh planes, back to the target rear surface. Black dashed and solid curves represent the profiles used in the modeling attributing to lower [$r(E{)}_{\min }$] and upper [$r(E{)}_{\max }$] limits, respectively. Since the peak proton energies of the hemicylindrical and planar shots were different (23 MeV and 33 MeV, respectively) due to shot to shot variations, ${\theta }_i(E)$ and $r(E)$ are plotted against energy normalized to the peak proton energy.Reuse & Permissions