Operation of a double-sided CMOS pixelated detector at a high intensity <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="d1e123" altimg="si1.svg"><mml:mrow><mml:msup><mml:mrow><mml:mi>e</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi>e</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> particle collider

Cuesta, D.; Baudot, J.; Claus, G.; Goffe, Mathieu; Jaaskelainen, Kimmo; Šantelj, L.; Specht, Matthieu; Szelezniak, Michal; Ripp-Baudot, I.

doi:10.1016/j.nima.2020.163862

Cited by 4 publications

(9 citation statements)

References 13 publications

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“…The Pixelated Ladder with Ultra-low Material Embedding (PLUME) detector is designed as a hit rate monitor, with a material budget low enough to minimally impact particle trajectories [10]. It is based on ultra-light double-sided ladders equipped with CMOS pixel sensors, initially developed as a generic concept for the vertex detector of the International Large Detector (ILD) [11].…”

Section: Plume Detector Systemmentioning

confidence: 99%

Measurements of Beam Backgrounds in SuperKEKB Phase 2

Liptak,

Paladino,

Santelj

et al. 2021

Preprint

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The high design luminosity of the SuperKEKB electron-positron collider will result in challenging levels of beam-induced backgrounds in the interaction region. Understanding and mitigating these backgrounds is critical to the success of the Belle II experiment. We report on the first background measurements performed after roll-in of the Belle II detector, a period known as Su-perKEKB Phase 2, utilizing both the BEAST II system of dedicated background detectors and the Belle II detector itself. We also report on first revisions to the background simulation made in response to our findings. Backgrounds measured include contributions from synchrotron radiation, beam-gas, Touschek, and injection backgrounds. At the end of Phase 2, single-beam backgrounds originating from the 4 GeV positron Low Energy Ring (LER) agree reasonably well with simulation, while backgrounds from the 7 GeV electron High Energy Ring (HER) are approximately one order of magnitude higher than simulation. We extrapolate these backgrounds forward and conclude it is safe to install the Belle II vertex detector.

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Section: Plume Detector Systemmentioning

confidence: 99%

Measurements of Beam Backgrounds in SuperKEKB Phase 2

Liptak,

Paladino,

Santelj

et al. 2021

Preprint

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“…The vessels are filled with a 70:30 mixture of He:CO 2 gas, which serves as the target gas with which neutrons interact. When a fast neutron enters a TPC, it may scatter off of a 4 He, 12 C, or 16 O nucleus, causing the nucleus to recoil. The recoiling nucleus will then collide with other gas atoms in the vessel until it eventually stops.…”

Section: The Tpc Systemmentioning

confidence: 99%

“…5 shows the probability of an incident neutron interacting with a gas nucleus per centimeter of travel within the fiducial volume of the vessel. Given the low probability of interaction of a neutron passing through the fiducial volume of a TPC, we scale up the elastic scattering cross sections between neutrons and 4 He, 12 C, and 16 O nuclei in the G4NDL4.6 library, each by factors of 100, to reduce the computational resources necessary to generate adequate simulated nuclear recoil samples for analysis. This leads to a roughly 100-fold increase in the nuclear recoil detection efficiency in each TPC, so when comparing measured and simulated nuclear recoil rates in the TPCs in Section 6, we divide the rates predicted by simulation by 100 to compensate for these cross section adjustments.…”

Section: Simulation Of Tpc Detectorsmentioning

confidence: 99%

“…The relatively flat lowest energy band (dE/dx ∼ 0) corresponds to electron recoils from X-ray conversions, which is the predominant source of background in all TPCs. The remaining two curved dE/dx bands correspond to, in order of increasing dE/dx: 4 He recoils and 12 C/ 16 O recoils. The dE/dx distributions of recoiling 12 C and 16 O nuclei are similar enough that we do not distinguish between them in measurement.…”

Section: Event Classificationmentioning

confidence: 99%

“…Additional descriptions and analyses of background sources at Su-perKEKB can be found in Refs. [12,13,14,15,16,17,18,19].…”

Section: Introductionmentioning

confidence: 99%

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Application of recoil-imaging time projection chambers to directional neutron background measurements in the SuperKEKB accelerator tunnel

Schueler,

Vahsen,

Lewis

et al. 2021

Preprint

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Gaseous time projection chambers (TPCs) with high readout segmentation are capable of reconstructing detailed 3D ionization distributions of nuclear recoils resulting from elastic neutron scattering. Using a system of six compact TPCs with pixel ASIC readout, filled with a 70:30 mixture of He:CO 2 gas, we analyze the first directional measurements of beam-induced neutron backgrounds in the tunnel regions surrounding the Belle II detector at the SuperKEKB e + e − collider. With the use of 3D recoil tracking, we show that these TPCs are capable of maintaining nearly 100% nuclear recoil purity to reconstructed ionization energies (E reco ) as low as 5 keV ee . Using a large sample of Monte-Carlo (MC)-simulated 4 He, 12 C, and 16 O recoil tracks, we find consistency between predicted and measured recoil energy spectra in five of the six TPCs, providing useful validation of the neutron production mechanisms modeled in simulation. Restricting this sample to 4 He recoil tracks with E reco > 40 keV ee , we further demonstrate axial angular resolutions within 8 • and we introduce a procedure that under suitable conditions, correctly assigns the vector direction to 91% of these simulated 4 He recoils. Applying this procedure to assign vector directions to measured 4 He recoil tracks, we observe consistency between the angular distributions of observed and simulated recoils in five of the six TPCs, providing first experimental evidence of localized neutron "hotspots" on either side of the Belle II detector. Observed rates of nuclear recoils in these TPCs suggest that simulation overestimates the neutron flux from these hotspots. Despite this, simulation predicts these hotspots to produce the majority of neutron backgrounds in the accelerator tunnel at SuperKEKB's design luminosity of 6 × 10 35 cm −2 s −1 , making them important regions to continue to monitor.

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