Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

The dataset contains the data reported on https://www.hzdr.de/publications/Publ-39073 where 2 proton bunch monitors (PBMs), namely the diamond detector and the cyclotron monitoring signal U_phi, are established, characterized, and applied for correcting the prompt gamma-ray timing (PGT) data. Experimental setup, irradiation modalities, data acquisition, and data pre- and postprocessing are described there.

The process is summarized in the following:

Experimental setup: A homogeneous cylindrical PMMA phantom was irradiated with a proton beam. Two sets of measurements were considered:

S1) measurements at the horizontal fixed beamline with the control of the beam time structure and current. These data establish the relation between the investigated PBMs and calibrate them to the scattering setup that provides the proton bunch arrival time in the experimental room. The phantom was irradiated with 7 different proton energies E_p = {70, 90, 110, 130, 160, 190, 224} MeV. For each E_p, 3 irradiation modalities were applied:

• CW-mode represented the continuous beam lasting for 30 s, the beam current I_beam = 2 nA for all E_p excluding 70 MeV (for 70 MeV, I_beam = 0.5 nA);
• Plan I represented a clinically realistic plan with a spot duration of 4 ms and a spot repetition time of 7 ms. The beam current I_beam = 1 nA for all E_p excluding 70 MeV (for 70 MeV, I_beam = 0.5 nA);
• Plan II aimed to reproduce the measurements of Werner et al. (2019) in Phys. Med. Biol. 64 105023, 20pp (https://doi.org/10.1088/1361-6560/ab176d). For that, the spot duration was set to 69 ms, and the repetition time was 72 ms. The beam current I_beam = 1 nA for all E_p excluding 70 MeV (for 70 MeV, I_beam = 0.5 nA).

S2) measurements at the pencil beam scanning (PBS) beamline were similar to those at the clinical beam delivery nozzle. The PBS beamline delivers the beam as spots of given intensity (expressed in MU), (x,y)-coordinates, and energy (corresponds to the penetration depth or z-coordinate). These data comprise data from the PGT detector and PBMs and are used to correct the PGT data employing the investigated PBMs. The phantom was irradiated with 8 different proton energies E_p = {70, 90, 110, 130, 162, 180, 200, 220} MeV. For every energy, 2 spot intensities were considered: 0.1 MU per 1 spot (~1e7 protons) and 1 MU per 1 spot (~1e8 protons). For E_p = 162 MeV, an additional spot intensity of 10 MU per 1 spot (~1e9 protons) was applied to reproduce the measurements of Werner et al. (2019) in Phys. Med. Biol. 64 105023, 20pp (https://doi.org/10.1088/1361-6560/ab176d).

Data preprocessing:

The raw data of each measurement were converted from the binary list-mode format to ROOT TTrees. The data were corrected for the photomultiplier gain drift, and digitalization time non-linearities, and the integral signal was converted into deposited energy. For the measurements at the fixed beamline, the coincidence analysis was applied additionally for non-PBM detectors. The data were assigned to individual corresponding spots for the PBS beamline measurements.

Data structure:

The ROOT files are named u100-p00XX-yyyy-mm-dd_HH.MM.SS+TZ.root where p00XX is the detector’s number, yyyy-mm-dd_HH.MM.SS is the time of the measurement, and TZ is the time zone. Here, p0012 and p0019 mean scintillating detectors that were used both at the fixed beamline, and only detector p0012 was used for PGT measurements at the PBS beamline. P0015 is the diamond detector, and p0017 contains data of the U_phi signal.

In general, the data structure inside the ROOT files is different depending on the purpose of the detector. However, there are some general includes:

• data (TTree) contains list-mode data which comprises
  • uncorrected data: before corrections and calibrations steps;
  • corrected data: after correcations and calibrations steps;
• meta (TTree) is a measurement metadata (applied detector voltage, the start time of the measurements, etc.);
• histograms is a directory with selected example histograms (uncorrected);
• analysis is a directory with histograms with corrected data used for the analysis.

For further questions, please refer to the contact persons stated above.