Table 1.
The detail scintillation crystal specification is in this table.
Light yield and decay time are important parameters of scintillation effect [29]. The photons generated from scintillation effect are affected by refractive index, attenuation length and the density of material [29, 30].
Fig 1.
The Longitudinal energy deposit distribution in each crystal is shown at various incident energies ranging from 50 to 400 MeV/u as a function of depth in mm.
The Bragg peak is shown in each energy of carbon beam. The red, green and blue lines denote LYSO, CsI and BGO respectively.
Fig 2.
The left plot is distribution of leakage energy from events simulated with 400 MeV/u carbon shot on LYSO crystal.
The diagram on the top right indicates the ratio of the number of events between fully deposited and leaked energy. The diagram on the bottom right shows the composition of leakage events, with the dominant leakage originating from neutrons.
Fig 3.
The geometry of our monitoring system consists of fiber layer and crystal.
The crystal, which is sky blue part, is 20 × 20 × 120mm3. The fiber hodoscope, which is orange part, is composed by two fiber layers is place in front of crystal. The red line indicates the beam line, and the reference coordinate is located on the middle side of figure.
Fig 4.
Zoom in on the boundary of the fiber layers and crystal in Fig 3.
The orange part represents the fiber layer, while the sky blue part represents the crystal. The horizontal line represents the beam line, and the red line indicates the path where the beam enters the scintillation material. When the beam is on the red line, the scintillation effect occurs. (a) refers to the square type fiber, while (b) refers to the round type fiber. The round type fiber has a lot of vacancies, making it unsuitable for use as a tracker.
Table 2.
Carbon beams are simulated with various energy; 100 to 400 MeV/u with a step size of 50 MeV/u.
And proton beams also are tested; 50 to 200 MeV with a step size of 50 MeV. With FTFP_BERT physics list, 5000 events are generated for all energy points. However, only carbon beams with LYSO are simulated with QGSP_BIC physics list for comparison purpose.
Fig 5.
The distributions of optical photon in crystals with 0.662 MeV gamma beam are shown.
The full peaks of each crystal are fitted with a Gaussian function, and their results are in top left corner of the plot. The red, green and blue lines denote LYSO, CsI and BGO respectively.
Table 3.
Calibration constants determined for each crystal are shown in this table.
The incident energy of gamma used in the calibration is 0.662 MeV. In gamma spectroscopy, The full peak is used in the calibration. The calibration constant is determined by dividing the incident energy by the mean value of the full peak.
Fig 6.
The comparison between reconstructed and generated positions in the x-axis (a) and z-axis (b) are shown.
The color bar means the number of events.
Fig 7.
The energy resolution and linearity results are shown in the plots.
The resolution plots on left side show the energy resolution by 1/. The linearity plots on right side indicate that the reconstructed energy is linear to the true deposited energy. Plots (a) and (b) correspond to the results for carbon beams, while plots (c) and (d) for proton beams. The red, green and blue lines denote LYSO, CsI and BGO respectively.
Fig 8.
The bottom left plot shows reconstructed position using Gaussian beam spot in the x-z plane and the fitteing results in the text.
The center of beam is located at (0,0) with the yellow region highlighting a higer beam intensity compared to the dark plue regions. The top and right plots represent the projection onto x-axis and z-axis, respectively, fitted with a Gaussian function. The σs of the incident beam are set to 1 mm, and those of reconstructed position are within 5% in comparison with the incident beam.
Fig 9.
(a) This figure shows the comparison of the Bragg peaks between FTFP_BERT and QGSP_BIC. The blue and red lines denote FTFP_BERT and QGSP_BIC, respectively. The incident beam energies are distinguished by style of lines. From front side of crystal of beam direction to Bragg peak, the difference of both lists is within ± 5%. The energy resolution and linearity are also compared between FTFP_BERT and QGSP_BIC in (b) and (c), respectively. Both are in good agreement within ± 5%.
Fig 10.
The prototype beam moniotring system based on geometry shown in Fig 3 is built.
(a) The crystal (LYSO) and PMT (R11265-100) are assembled using black square jigs. (b) The fiber hodoscope is composed of two fiber layers and jig for arranging the layers and a jig. (c) The prototype with fiber hodoscope and crystal are shown.