arXiv subjects

Christian Joachim Schmidt

Publications and source records attributed to Christian Joachim Schmidt.

8 recordsLinked to original sources

arXiv2026

CBM T0 Detector Performance Study with Light Ions (4He, 12C) and the DOGMA Readout System

This paper presents the realization and performance of the CBM T0 detector system. Built upon an approximately 70 μm thin polycrystalline CVD (pcCVD) diamond sensor with pad metallization, the detector is mounted on a flexible vacuum manipulator and operates entirely under passive cooling. Interfaced with the DOGMA readout architecture, the system successfully meets all operational requirements for CBM. It demonstrates a high detection efficiency (near 100%) and a timing precision below 50 ps RMS across a broad range of beam species, from light ions (such as Carbon) to heavy ions (such as Gold). The DOGMA readout features two distinct data paths: a high-precision TDC path routing data directly to the global CBM DAQ, and a secondary path deliver in real-time rate measurements crucial for online beam quality monitoring and fast beam abort logic. Finally, detailed performance studies conducted with light-ion beams at EBG MedAustron are discussed.

physics.ins-det↗

arXiv2026

The Silicon Tracking System of the E16 experiment at J-PARC: construction, installation and commissioning in beam test experiments

The J-PARC E16 experiment aims to search for signatures of chiral symmetry restoration. It studies in-medium modifications of vector mesons that decay via the dielectron channel. The measurements use a high-intensity 30 GeV proton beam with C and Cu targets at rates up to 10 MHz. To achieve this, the experiment upgrades its tracking, by introducing innermost detector modules constructed with the same technology and procedures as the modules of the Silicon Tracking System (STS) of the Compressed Baryonic Matter (CBM) experiment at Facility for Antiproton and Ion Research (FAIR). A total of 15 modules were assembled, tested, characterized and then installed in the E16 detector setup. The detector was commissioned in a beam test experiment at Tsukuba, where the detector modules could be exposed to a 3 GeV electron beam. In preparation for the beam test the modules were characterized and calibrated, and performance studies were accomplished to assess the quality of the setup. During beamtime, three modules were operated and illuminated in two planes by the electron beam. This paper presents the results of the construction, characterization, commissioning, and operation of the E16-STS modules in beam test experiments.

physics.ins-det↗

arXiv2025

Evaluation of a large-area double-sided silicon strip detector for quality assurance in ion-beam radiotherapy

Designed to provide quality assurance for ion-beam radiotherapy, the prototype fIVI (filtered Interaction Vertex Imaging) Range Monitoring System is a two-layer tracker which employs double-sided strip-segmented silicon detectors. To meet the high demands of a clinical environment, a large sensitive area is required, along with a fast and compact readout. As this device utilizes sensors and readout electronics adapted from particle physics, where the expected energy and count rate differ significantly from radiotherapy, validation was necessary to ensure that these sensors would function effectively at the order 100 MeV/u energies and order MHz count rates expected during clinical irradiation. Tests were conducted using scattered subclinical 19 MeV protons at high intensity, and clinical 207 MeV/u carbon ions at low intensity to independently validate these variables. The detection system is found to operate at rates up to 1.3 MHz, with a negligible fraction of events being affected by pileup. The efficiency of hit reconstruction is high, with a timestamp resolution of 6.25 ns, and a coincidence window of 31.25 ns, as is required for clinical event rates. With these settings, over 90% of particle interactions are able to reconstruct unique hit positions and contribute to track formation. This device is the first system using large-area, high-resolution detectors which meets the demanding count rate requirements associated with clinical radiotherapy.

physics.ins-det↗

arXiv2025

Clinical beam test of inter- and intra-fraction relative range monitoring in carbon ion radiotherapy

Interaction Vertex Imaging (IVI) is used for range monitoring (RM) in carbon ion radiotherapy. The purpose of RM is to measure the Bragg peak (BP) position for each contributing beam, and detect any changes. Currently, there is no consensus on a clinical RM method, the use of which would improve the safety and consistency of treatment. The prototype filtered IVI (fIVI) Range Monitoring System is the first system to apply large-area and high-rate-capable silicon detectors to IVI. Two layers of these detectors track prompt secondary fragments for use in RM. This device monitored 16 cm and 32 cm diameter cylindrical plastic phantoms irradiated by clinical carbon ion beams at the Heidelberg Ion Beam Therapy Center. Approximately 20 different BP depths were delivered to each phantom, with a minimum depth difference of 0.8 mm and a maximum depth difference of 51.9 mm and 82.5 mm respectively. For large BP range differences, the relationship between the true depth difference and that measured by fIVI is quadratic, although for small differences, the deviation from a linear relationship with a slope of 1 is negligible. RM performance is strongly dependent on the number of tracked particles, particularly in the clinically-relevant regime. Significant performance differences exist between the two phantoms, with millimetric precision at clinical doses being achieved only for the 16 cm phantom. The performance achieved by the prototype fIVI Range Monitoring System is consistent with previous investigations of IVI, despite measuring at more challenging shallow BP positions. Further significant improvements are possible through increasing the sensitive area of the tracking system beyond the prototype, which will both allow an improvement in precision for the most intense points of a scanned treatment plan and expand the number of points for which millimetric precision may be achieved.

physics.med-ph↗

arXiv2025

A parallel, pipeline-based online analysis system for Interaction Vertex Imaging

Objective Interaction vertex imaging (IVI) is used for range monitoring in carbon ion radiotherapy, detecting depth differences between Bragg peak positions. Online range monitoring, which provides feedback during beam delivery, is particularly desirable, creating an opportunity to detect range errors before the treatment fraction is completed. Incorporating online range monitoring into clinical workflows may therefore improve the safety and consistency of radiotherapy. Approach The data analysis system was broken into a task-parallel pipeline approach, to allow multiple analysis stages to occur concurrently, beginning during acquisition. Computationally-expensive operations were further parallelized to reduce bottleneck effects. Data collected from irradiation of homogeneous plastic phantoms was replayed at the same rate it was initially acquired, to mimic data acquisition, and the time required to determine a range shift was measured. Main Results With an optimized pipeline, the delay between the end of irradiation and the determination of a range shift is consistently less than 200 ms. The majority of this time is associated with the final range shift determination, with a minor effect from the time required to analyze the last data packet. The most significant contribution to an optimized analysis workflow is the formation of clusters, requiring almost 50% of compute time. Significance This system is the first IVI implementation to achieve clinically-relevant online analysis times. The 200 ms time required to determine a range shift is less than the time required to accelerate a new spill in a synchrotron, and is comparable to the time required for reacceleration if multiple energies are delivered in the same spill. Clinical implementation of online range monitoring would allow treatment to be quickly paused or aborted if significant range errors are detected.

physics.med-ph↗

arXiv2025

Integration Concept of the CBM Micro Vertex Detector

The Micro Vertex Detector (MVD) is the most upstream detector of the fixed-target Compressed Baryonic Matter Experiment (CBM) at the future Facility for Antiproton and Ion Research (FAIR). It enables high-precision low-momentum tracking in direct proximity of the target. Reaching the stringent requirements for the MVD, a material budget of~$0.3\,-\,0.5\%\,X_0$ per layer, operating the dedicated CMOS MAPS~(`MIMOSIS') in the target vacuum, the strong magnetic dipole field, and a harsh radiation environment~(5\,Mrad, $7\times10^{13}\,n_{\text{eq}}/\text{cm}^2$ per CBM year), poses an unprecedented integration challenge. In this paper, the integration concept of the detector is be outlined, elaborating on the selection and preparation of materials, assembly procedures, and quality assessment steps in the ongoing preparation of pre-series production and detector commissioning in 2028.

physics.ins-det↗

arXiv2025

In beam performances of the MIMOSIS-2.1 CMOS Monolithic Active Pixel Sensor

MIMOSIS is a CMOS Monolithic Active Pixel Sensor developed to equip the Micro Vertex Detector of the Compressed Baryonic Matter (CBM) experiment at FAIR/GSI. The sensor will combine an excellent spatial precision of $5~μm$ with a time resolution of $5~μs$ and provide a peak hit rate capability of $\mathrm{\sim 80~ MHz/cm^2}$. To fulfill its task, MIMOSIS will have to withstand ionising radiation doses of $\sim 5~ \mathrm{MRad}$ and fluences of $\sim 7 \times 10^{13}~\mathrm{n_{eq}/cm^2}$ per year of operation. This paper introduces the reticle size full feature sensor prototype MIMOSIS-2.1, which was improved with respect to earlier prototypes by adding on-chip grouping circuts and by improving the analog power grid. Moreover, it features for a first time a $50~μm$ epitaxial layer, which is found to improve the performances of the non-irradiated device significantly. We discuss the in beam sensor performances as measured during beam tests at the CERN-SPS.

physics.ins-det↗

arXiv2023

First experimental time-of-flight-based proton radiography using low gain avalanche diodes

Ion computed tomography (iCT) is an imaging modality for the direct determination of the relative stopping power (RSP) distribution within a patient's body. Usually, this is done by estimating the path and energy loss of ions traversing the scanned volume via a tracking system and a separate residual energy detector. This study, on the other hand, introduces the first experimental study of a novel iCT approach based on time-of-flight (TOF) measurements, the so-called Sandwich TOF-iCT concept, which in contrast to any other iCT system, does not require a residual energy detector for the RSP determination. A small TOF-iCT demonstrator was built based on low gain avalanche diodes (LGAD), which are 4D-tracking detectors that allow to simultaneously measure the particle position and time-of-arrival with a precision better than 100um and 100ps, respectively. Using this demonstrator, the material and energy-dependent TOF was measured for several homogeneous PMMA slabs in order to calibrate the acquired TOF against the corresponding water equivalent thickness (WET). With this calibration, two proton radiographs (pRad) of a small aluminium stair phantom were recorded at MedAustron using 83 and 100.4MeV protons. Due to the simplified WET calibration models used in this very first experimental study of this novel approach, the difference between the measured and theoretical WET ranged between 37.09 and 51.12%. Nevertheless, the first TOF-based pRad was successfully recorded showing that LGADs are suitable detector candidates for TOF-iCT. While the system parameters and WET estimation algorithms require further optimization, this work was an important first step to realize Sandwich TOF-iCT. Due to its compact and cost-efficient design, Sandwich TOF-iCT has the potential to make iCT more feasible and attractive for clinical application, which, eventually, could enhance the treatment planning quality.

physics.med-ph↗