Author Contributions
Conceptualization, A.B.-F., S.B., L.C., J.H., A.K. (Asher Kaboth), J.M., R.N., J.N., R.S., N.S., Y.S. and M.W. (Morgan Wascko); data curation, S.J., T.N., E.A., D.B., A.D. (Alexander Deisting), A.D. (Adriana Dias), P.D., J.H., P.H.-B., A.K. (Asher Kaboth), A.K. (Alexander Korzenev), M.M., J.M., R.N., J.N., W.P., H.R.-Y., Y.S., A.T., M.U., S.V., A.W. and M.W. (Morgan Wascko); formal analysis, S.J., T.N., P.D., A.K. (Alexander Korzenev), Y.S. and A.W.; funding acquisition, G.B., A.B.-F., S.B., A.K. (Asher Kaboth), J.M., R.N., J.N., S.R., R.S. and M.W. (Morgan Wascko); investigation, S.J., T.N., A.B.-F., S.B., L.C., P.D., P.H.-B., A.K. (Asher Kaboth), W.M., M.M., J.M., R.N., J.N., R.S., Y.S., J.S., M.U., S.V., A.W., M.W. (Mark Ward) and M.W. (Morgan Wascko); methodology, S.J., T.N., E.A., A.B.-F., C.B., S.B., Z.C.-W., L.C., A.D. (Alexander Deisting), A.D. (Adriana Dias), P.D., J.H., A.K. (Asher Kaboth), A.K. (Alexander Korzenev), P.M., J.M., R.N., W.P., H.R.-Y., R.S., N.S., Y.S., A.T., M.U., S.V., A.W., M.W. (Mark Ward) and M.W. (Morgan Wascko); project administration, G.B., S.B., L.C., A.D. (Alexander Deisting), A.K. (Asher Kaboth), J.M., R.N., J.N. and M.W. (Morgan Wascko); resources, S.B., L.C., A.K. (Asher Kaboth), J.M., R.N., J.N., S.R. and M.W. (Morgan Wascko); Software, S.J., T.N., E.A., D.B., Z.C.-W., L.C., A.D. (Alexander Deisting), A.D. (Adriana Dias), J.H., A.K. (Asher Kaboth), J.M., R.N., W.P., S.V., A.W. and M.W. (Mark Ward); supervision, G.B., A.B.-F., S.B., L.C., A.D. (Alexander Deisting), P.D., J.H., A.K. (Asher Kaboth), J.M., R.N., J.N., R.S., A.W. and M.W. (Morgan Wascko); validation, S.J., T.N., E.A., D.B., Z.C.-W., L.C., A.D. (Alexander Deisting), A.D. (Adriana Dias), A.K. (Asher Kaboth), M.M., J.M., R.N., W.P., H.R.-Y. and A.T.; visualization, S.J., T.N., L.C. and R.N.; writing—original draft, S.J., T.N., A.K. (Asher Kaboth), J.M. and M.W. (Morgan Wascko); writing—review and editing, S.J., T.N., E.A., S.B., D.B., Z.C.-W., L.C., A.D. (Alexander Deisting), A.D. (Adriana Dias), P.D., A.K. (Asher Kaboth), M.M., J.M., R.N., J.N., W.P., H.R.-Y., A.T., A.W. and M.W. (Morgan Wascko). All authors have read and agreed to the published version of the manuscript.
Figure 1.
Total reaction cross sections for protons on argon, neon, fluorine, oxygen, carbon and helium-4. Data [
14] are compared to a semi-empirical model [
11]. Figure from [
15].
Figure 1.
Total reaction cross sections for protons on argon, neon, fluorine, oxygen, carbon and helium-4. Data [
14] are compared to a semi-empirical model [
11]. Figure from [
15].
Figure 2.
Predicted proton kinetic energy (KE) spectra from GENIE, NEUT and NuWro [
18]. Energy spectra up to 1 GeV are shown on the left, and zoomed in to lower energies on the right. The figure uses the Long Baseline Neutrino Facility (LBNF) simulation for DUNE’s beam energy and flux. The LBNF beam has a mean energy of approximately 2.5 GeV [
4]. The dashed vertical line indicates the expected proton automated-reconstruction/identification threshold in liquid argon, and the solid vertical line shows the same for gaseous argon at 10 atm [
12].
Figure 2.
Predicted proton kinetic energy (KE) spectra from GENIE, NEUT and NuWro [
18]. Energy spectra up to 1 GeV are shown on the left, and zoomed in to lower energies on the right. The figure uses the Long Baseline Neutrino Facility (LBNF) simulation for DUNE’s beam energy and flux. The LBNF beam has a mean energy of approximately 2.5 GeV [
4]. The dashed vertical line indicates the expected proton automated-reconstruction/identification threshold in liquid argon, and the solid vertical line shows the same for gaseous argon at 10 atm [
12].
Figure 3.
Measurements of the unmoderated and unbent T10 beam over a baseline of 10.8 m for a selected beam momentum of 0.8 GeV/c. Measurements are made in the S3 detector. The peak between 50 ns and 60 ns is produced by protons. (Left) Time of flight spectrum. (Right) Measured kinetic energy of protons.
Figure 3.
Measurements of the unmoderated and unbent T10 beam over a baseline of 10.8 m for a selected beam momentum of 0.8 GeV/c. Measurements are made in the S3 detector. The peak between 50 ns and 60 ns is produced by protons. (Left) Time of flight spectrum. (Right) Measured kinetic energy of protons.
Figure 4.
Calculated intensity of the T10 beam as a function of selected beam momentum, separated by particle type [
19].
Figure 4.
Calculated intensity of the T10 beam as a function of selected beam momentum, separated by particle type [
19].
Figure 5.
Schematic diagram (plan view) of the High Pressure gas Time Projection Chamber (HPTPC) beam test configuration in the T10 area at CERN.
Figure 5.
Schematic diagram (plan view) of the High Pressure gas Time Projection Chamber (HPTPC) beam test configuration in the T10 area at CERN.
Figure 6.
Photos illustrating the time of flight (ToF) constituents. (Left) the downstream part of the setup which shows the S3, S4 detectors and HPTPC. (Right) S1 and S2 counters and the stand with four acrylic moderator blocks.
Figure 6.
Photos illustrating the time of flight (ToF) constituents. (Left) the downstream part of the setup which shows the S3, S4 detectors and HPTPC. (Right) S1 and S2 counters and the stand with four acrylic moderator blocks.
Figure 7.
Angular position of various objects within the T10 beamline. The origin in this view is at the centre of S1; the true centre of the steered beam is at +1° in and 0° in .
Figure 7.
Angular position of various objects within the T10 beamline. The origin in this view is at the centre of S1; the true centre of the steered beam is at +1° in and 0° in .
Figure 8.
The S1 and S2 beam counters. Together the coincidence of signals in the beam counters were recorded by the data acquisition (DAQ) systems.
Figure 8.
The S1 and S2 beam counters. Together the coincidence of signals in the beam counters were recorded by the data acquisition (DAQ) systems.
Figure 9.
Example of the timing spread of S1 hits. The time is calculated as an average of the hit time as measured in each of the four photomultiplier tubes (PMTs).
Figure 9.
Example of the timing spread of S1 hits. The time is calculated as an average of the hit time as measured in each of the four photomultiplier tubes (PMTs).
Figure 10.
View of the time of flight panels. (
Left) The
S3 panel [
22] upstream of the TPC. (
Right) The
S4 panel downstream of the TPC.
Figure 10.
View of the time of flight panels. (
Left) The
S3 panel [
22] upstream of the TPC. (
Right) The
S4 panel downstream of the TPC.
Figure 11.
Reconstructed positions of hits observed in S3. (Left) Minimum ionizing particles with four moderator blocks placed in the beamline. (Right) Protons detected with four moderator blocks placed in the beamline. This figure uses local S3 coordinates in which cm is the bottom right corner of the active area when viewed from S1.
Figure 11.
Reconstructed positions of hits observed in S3. (Left) Minimum ionizing particles with four moderator blocks placed in the beamline. (Right) Protons detected with four moderator blocks placed in the beamline. This figure uses local S3 coordinates in which cm is the bottom right corner of the active area when viewed from S1.
Figure 12.
Simplified trigger logic diagram for the upstream ToF detection of a beam particle, showing the required coincidences. Left and right refer to the silicon photomultipliers (SiPMs) on the opposite ends of the same bar.
Figure 12.
Simplified trigger logic diagram for the upstream ToF detection of a beam particle, showing the required coincidences. Left and right refer to the silicon photomultipliers (SiPMs) on the opposite ends of the same bar.
Figure 13.
Difference in signal arrival time for PMTs at each end of a bar as measured using a 90Sr source placed 64 cm from one end of the bar.
Figure 13.
Difference in signal arrival time for PMTs at each end of a bar as measured using a 90Sr source placed 64 cm from one end of the bar.
Figure 14.
Cross-sectional view of the TPC; the thin mesh electrodes and copper ring drift volume can be seen inside the steel vessel. The walls of the vessel shown are 1 cm thick with a vessel outer diameter of 142 cm. At the point of hitting the vessel, the beam centre was 1 cm below the centre of the vessel vertically, where the distance from the inside of the vessel wall to the drift region was 15 cm.
Figure 14.
Cross-sectional view of the TPC; the thin mesh electrodes and copper ring drift volume can be seen inside the steel vessel. The walls of the vessel shown are 1 cm thick with a vessel outer diameter of 142 cm. At the point of hitting the vessel, the beam centre was 1 cm below the centre of the vessel vertically, where the distance from the inside of the vessel wall to the drift region was 15 cm.
Figure 15.
Calculated time of flight for a number of different particle species as a function of particle momentum. (Left) ToF between S1 and S3. (Right) ToF between S2 and S4.
Figure 15.
Calculated time of flight for a number of different particle species as a function of particle momentum. (Left) ToF between S1 and S3. (Right) ToF between S2 and S4.
Figure 16.
S3 time of flight spectra for varying numbers of moderator blocks.
Figure 16.
S3 time of flight spectra for varying numbers of moderator blocks.
Figure 17.
Reconstructed mass spectrum for the data taken without moderator blocks. The spectrum was calculated using the time difference between S3 and S1. Vertical arrows show predicted position of particles given a momentum of 0.8 GeV/c. Insert: Zoomed view of MIP region of the same spectrum.
Figure 17.
Reconstructed mass spectrum for the data taken without moderator blocks. The spectrum was calculated using the time difference between S3 and S1. Vertical arrows show predicted position of particles given a momentum of 0.8 GeV/c. Insert: Zoomed view of MIP region of the same spectrum.
Figure 18.
Examples of SiPM signal amplitude plotted against S1 to S3 time of flight for different numbers of moderator blocks. Clockwise from top left 0, 1, 3 and 2 moderator blocks are shown. A1 is the voltage recorded in the SiPM at the end of the bar. The red horizontal dashed line shows the amplitude cut used for this particular SiPM. Events in the area enclosed by the red dashed lines are selected as protons. Events enclosed by the green dashed lines are selected as MIPs.
Figure 18.
Examples of SiPM signal amplitude plotted against S1 to S3 time of flight for different numbers of moderator blocks. Clockwise from top left 0, 1, 3 and 2 moderator blocks are shown. A1 is the voltage recorded in the SiPM at the end of the bar. The red horizontal dashed line shows the amplitude cut used for this particular SiPM. Events in the area enclosed by the red dashed lines are selected as protons. Events enclosed by the green dashed lines are selected as MIPs.
Figure 19.
S4 time of flight spectra for varying numbers of moderator blocks. For all configurations, a flat background has been fitted and subtracted from the data. Additionally, the plot has also been corrected for the differing efficiencies of the various bars and for the variation in efficiency as a function of position along the bar, as described in
Section 3.2.
Figure 19.
S4 time of flight spectra for varying numbers of moderator blocks. For all configurations, a flat background has been fitted and subtracted from the data. Additionally, the plot has also been corrected for the differing efficiencies of the various bars and for the variation in efficiency as a function of position along the bar, as described in
Section 3.2.
Figure 20.
Reconstructed mass spectrum for the data taken without moderator blocks. The spectrum was calculated using the time difference between S4 and S2. Vertical arrows show predicted position of particles.
Figure 20.
Reconstructed mass spectrum for the data taken without moderator blocks. The spectrum was calculated using the time difference between S4 and S2. Vertical arrows show predicted position of particles.
Figure 21.
Relative detection efficiency of S4 as a function of bar number and position along each bar as measured with cosmic rays. The data from bar 10 was not used in the analysis due to the poor efficiency along the bar.
Figure 21.
Relative detection efficiency of S4 as a function of bar number and position along each bar as measured with cosmic rays. The data from bar 10 was not used in the analysis due to the poor efficiency along the bar.
Figure 22.
Example of the time of flight spectrum observed in S4 with combined signal and background functions fitted (shown in red).
Figure 22.
Example of the time of flight spectrum observed in S4 with combined signal and background functions fitted (shown in red).
Figure 23.
Proton kinetic energy spectrum as measured in S3. (Left) All protons. (Right) The subset of protons passing through the HPTPC drift volume. The errors shown in the legend are the statistical error in particle number per spill.
Figure 23.
Proton kinetic energy spectrum as measured in S3. (Left) All protons. (Right) The subset of protons passing through the HPTPC drift volume. The errors shown in the legend are the statistical error in particle number per spill.
Figure 24.
Distribution of hits in S3 as a function of the horizontal off-axis angle, measured from S1, for varying numbers of moderator blocks. No coincident hit in S2 was required. (Left) Minimum ionizing particles. (Right) Protons. The errors shown in the legend are the statistical error in particle number per spill.
Figure 24.
Distribution of hits in S3 as a function of the horizontal off-axis angle, measured from S1, for varying numbers of moderator blocks. No coincident hit in S2 was required. (Left) Minimum ionizing particles. (Right) Protons. The errors shown in the legend are the statistical error in particle number per spill.
Figure 25.
Proton–MIP ratio in S3 for varying numbers of moderator blocks as a function of off-axis angle, as measured from S1. (Left) Horizontal angle. (Right) Vertical angle. The TPC spans horizontal angles 1.4–3.6° and vertical angles −2.6–+2.6°.
Figure 25.
Proton–MIP ratio in S3 for varying numbers of moderator blocks as a function of off-axis angle, as measured from S1. (Left) Horizontal angle. (Right) Vertical angle. The TPC spans horizontal angles 1.4–3.6° and vertical angles −2.6–+2.6°.
Figure 26.
Distribution of hits in S4 as a function of the number of moderator blocks and the horizontal off-axis angle. (Left) Minimum ionizing particles. (Right) Protons. The errors shown in the legend are the statistical error in particle number per spill.
Figure 26.
Distribution of hits in S4 as a function of the number of moderator blocks and the horizontal off-axis angle. (Left) Minimum ionizing particles. (Right) Protons. The errors shown in the legend are the statistical error in particle number per spill.
Figure 27.
Proton–MIP ratio in S4 for varying numbers of moderator blocks as a function of off-axis angle. (Left) Horizontal off-axis angle. (Right) Vertical off-axis angle.
Figure 27.
Proton–MIP ratio in S4 for varying numbers of moderator blocks as a function of off-axis angle. (Left) Horizontal off-axis angle. (Right) Vertical off-axis angle.
Figure 28.
Energy profile of simulated protons reaching S4, with kinetic energy above the detection threshold of 10 MeV.
Figure 28.
Energy profile of simulated protons reaching S4, with kinetic energy above the detection threshold of 10 MeV.
Figure 29.
Comparison of simulated and measured proton ToF between S2 and S4. Solid lines correspond to the simulated distributions, while points correspond to data. All distributions are area normalised to 1.
Figure 29.
Comparison of simulated and measured proton ToF between S2 and S4. Solid lines correspond to the simulated distributions, while points correspond to data. All distributions are area normalised to 1.
Figure 30.
(Left) Momentum profile of simulated protons reaching the active region of the TPC. (Right) Energy profile of simulated protons reaching the active region of the TPC. The errors shown in the legend are the statistical error in particle number per spill.
Figure 30.
(Left) Momentum profile of simulated protons reaching the active region of the TPC. (Right) Energy profile of simulated protons reaching the active region of the TPC. The errors shown in the legend are the statistical error in particle number per spill.
Table 1.
Angular extents of objects within the T10 beamline as measured from S1.
Table 1.
Angular extents of objects within the T10 beamline as measured from S1.
Object | Minimum θ | Maximum θ | Minimum ϕ | Maximum ϕ |
---|
S2 | −3.96° ± 0.03° | 0.36° ± 0.03° | −2.01° ± 0.03° | 2.94° ± 0.03° |
S3 | −5.923° ± 0.004° | 3.040° ± 0.004° | −3.215° ± 0.004° | 3.344° ± 0.004° |
S4 | −6.083° ± 0.003° | −0.410° ± 0.003° | −1.426° ± 0.003° | 1.771° ± 0.003° |
TPC upstream face | −3.59° ± 0.01° | −1.44° ± 0.01° | −2.66° ± 0.01° | 2.58° ± 0.01° |
TPC downstream face | −3.778° ± 0.009° | −1.806° ± 0.009° | −2.440° ± 0.009° | 2.361° ± 0.009° |
Table 2.
Distances between objects in the T10 beamline. US and DS refer to the upstream and downstream edges of the TPC, respectively.
Table 2.
Distances between objects in the T10 beamline. US and DS refer to the upstream and downstream edges of the TPC, respectively.
Points | Distance between Centres/m |
---|
Beam monitor – S1 | |
S1 − S2 | |
S1 − S3 | |
S3 − TPC US side | |
TPC DS side − S4 | |
S2 − S4 | |
Table 3.
Total number of spills recorded for each moderator block configuration included in this paper.
Table 3.
Total number of spills recorded for each moderator block configuration included in this paper.
Number of Moderator Blocks | Recorded Spills |
---|
0 | 257 |
1 | 254 |
2 | 267 |
3 | 220 |
4 | 3884 |
Table 4.
Background rates for the time of flight spectra measured in S4. To convert these to the number of expected background events in a spill, the rate is multiplied by the size of the timing window for either MIPs or protons.
Table 4.
Background rates for the time of flight spectra measured in S4. To convert these to the number of expected background events in a spill, the rate is multiplied by the size of the timing window for either MIPs or protons.
Number of Moderator Blocks | Background/Events × spill−1 × ns−1 |
---|
0 | |
1 | |
2 | |
3 | |
4 | |
Table 5.
List of systematic errors and values for data and Monte Carlo (MC) simulation. All values are the percent error on the S4 proton count with the exception of the uncertainty on the efficiency of S3, which is the percent error on the S3 proton count. All uncertainties are treated as uncorrelated. nS4,MC refers to the number of protons reaching S4 in MC simulations.
Table 5.
List of systematic errors and values for data and Monte Carlo (MC) simulation. All values are the percent error on the S4 proton count with the exception of the uncertainty on the efficiency of S3, which is the percent error on the S3 proton count. All uncertainties are treated as uncorrelated. nS4,MC refers to the number of protons reaching S4 in MC simulations.
Monte Carlo |
---|
| Number of moderator blocks |
| 0 | 1 | 2 | 3 | 4 |
Systematic uncertainty on nS4,MC | 9.5% | 8.0% | 8.5% | 17.0% | 8.0% |
Data |
| Number of moderator blocks |
Source of systematic error | 0 | 1 | 2 | 3 | 4 |
Absolute efficiency of S3 | 1.1% | 11.4% | 7.0% | 11.4% | 4.9% |
Absolute efficiency of S4 | 11.0% | 11.0% | 11.0% | 11.0% | 11.0% |
S4 angular correction | 2.9% | 1.5% | 6.7% | 8.2% | 4.1% |
S4 background uncertainty | 0.18% | 0.16% | 1.1% | 1.4% | 8.1% |
Total | 11.5% | 16.0% | 14.7% | 18.3% | 18.9% |
Table 6.
Ratio of number of protons reaching S4 to number protons reaching S3 for different numbers of moderator blocks in MC and data. In each instance, the combined statistical and systematic errors are shown.
Table 6.
Ratio of number of protons reaching S4 to number protons reaching S3 for different numbers of moderator blocks in MC and data. In each instance, the combined statistical and systematic errors are shown.
Number of Moderator Blocks | Monte Carlo | Data | Data/MC |
---|
0 | | | |
1 | | | |
2 | | | |
3 | | | |
4 | | | |