Max Philip Rauch

This work reports the testing of a Forward Calorimeter (FoCal) prototype based on an n-type Si pad array detector at the CERN PS accelerator. The FoCal is a proposed upgrade in the ALICE detector operating within the pseudorapidity range of 3.2 < $\mathrm{\eta}$ < 5.8. It aims to measure direct photons, neutral hadrons, vector mesons, and jets for the study of gluon saturation effects in the unexplored region of low momentum fraction x ($\mathrm{\sim10^{-5} - 10^{-6}}$). The prototype is a $\mathrm{8\times9}$ n-type Si pad array detector with each pad occupying one cm$^2$ area, fabricated on a 6-in, 325~$\mathrm{\pm 10 \thinspace \mu}$m thick, and high-resistivity ($\sim$7 k$\Omega \thinspace$ cm) Si wafer which is readout using HGCROCv2 chip. The detector is tested using pion beams of energy 10~GeV and electron beams of energy 1-5~GeV. The measurements of the Minimum Ionizing Particle (MIP) response of pions and the shower profiles of electrons are reported.

Highly integrated multichannel readout electronics is crucial in contemporary particle physics experiments. A novel silicon photomultiplier readout system based on the VMM3a ASIC was developed, for the first time exploiting this chip for calorimetric purposes. To extend the dynamic range the signal from each SiPM channel was processed by two electronics channels with different gain. A fully operational prototype system with 256 SiPM readout channels allowed the collection of data from a prototype of the ALICE Forward Hadron Calorimeter (FoCal-H). The design and the test beam results using high energy hadron beams are presented and discussed, confirming the applicability of VMM3a-based solutions for energy measurements in a high rate environment.

Abstract Die Versuche, durch Kondensation von Orange II mit p‐Phenylendiamin einen „Semidin”︁ ‐artigen Azofarbstoff: magnified image zu erhalten, führten nicht zum Ziel. Vielmehr zeigte sich, daß die Kondensation, im Gegensatz zu der analogen mit Phenylhydrazin: magnified image unter gleichzeitiger weitgehender Veränderung des Azofarbstoffes erfolgt. Die dabei erhaltene farbige Verbindung, deren Konstitution nicht aufgeklärt wurde, zeigt den Charakter eines verküpbaren Farbstoffs.

The pixel detector of the CMS experiment will be exchanged during the year-end technical stop in 2016/2017, as part of the experiment's Phase-1 upgrade. The new device will feature approximately twice the number of readout channels, and consequently the power consumption will be doubled. By moving to a DC-DC conversion powering scheme, it is possible to power the new pixel detector with the existing power supplies and cable plant.

A novel powering scheme based on the DC-DC conversion technique will be exploited to power the CMS Phase-1 pixel detector. DC-DC buck converters for the CMS pixel project have been developed, based on the AMIS5 ASIC designed by CERN. The powering system of the Phase-1 pixel detector is described and the performance of the converter prototypes is detailed, including power efficiency, stability of the output voltage, shielding, and thermal management. Results from a test of the magnetic field tolerance of the DC-DC converters are reported. System tests with pixel modules using many components of the future pixel barrel system are summarized. Finally first impressions from a pre-series of 200 DC-DC converters are presented.

The CMS collaboration has adopted a DC-DC conversion powering scheme for the Phase-1 Upgrade of its pixel detector. DC-DC buck converters with a conversion ratio of around 3 are installed on the support structures, outside of the sensitive tracking region, requiring a re-design of the low and high voltage distribution to the pixel modules. After several years of R&D, the project has entered the production phase. A total of 1800 DC-DC converters are being produced, and rigorous quality assurance and control is being employed during the production process. The testing program is outlined, results from mass production are presented and issues that have been encountered are described. In addition, two system level challenges, namely the choice of output voltage in the presence of large, load-dependent voltage drops, and the thermal management required to remove the heat load caused by the DC-DC converters, are discussed.

A new pixel detector for the CMS experiment was built in order to cope with the instantaneous luminosities anticipated for the Phase~I Upgrade of the LHC. The new CMS pixel detector provides four-hit tracking with a reduced material budget as well as new cooling and powering schemes. A new front-end readout chip mitigates buffering and bandwidth limitations, and allows operation at low comparator thresholds. In this paper, comprehensive test beam studies are presented, which have been conducted to verify the design and to quantify the performance of the new detector assemblies in terms of tracking efficiency and spatial resolution. Under optimal conditions, the tracking efficiency is $99.95\pm0.05\,\%$, while the intrinsic spatial resolutions are $4.80\pm0.25\,\mu \mathrm{m}$ and $7.99\pm0.21\,\mu \mathrm{m}$ along the $100\,\mu \mathrm{m}$ and $150\,\mu \mathrm{m}$ pixel pitch, respectively. The findings are compared to a detailed Monte Carlo simulation of the pixel detector and good agreement is found.

The addition of a Forward Calorimeter (FoCal) to the ALICE experiment is proposed for LHC Run 4 to provide unique constraints on the low-x gluon structure of protons and nuclei via forward measurements of direct photons.A new high-resolution electromagnetic silicon-tungsten calorimeter using both low-granularity silicon pads and high-granularity silicon pixel layers is being developed to discriminate single photons from pairs of photons originating from 0 decays.A conventional sampling hadron calorimeter is foreseen for jet measurements and the isolation of direct photons.This article reports on results from test beam campaigns in 2021 and 2022 at CERN with first prototypes for the electromagnetic and hadronic calorimeter.

Objective.Proton therapy is highly sensitive to range uncertainties due to the nature of the dose deposition of charged particles. To ensure treatment quality, range verification methods can be used to verify that the individual spots in a pencil beam scanning treatment fraction match the treatment plan. This study introduces a novel metric for proton therapy quality control based on uncertainties in range verification of individual spots.Approach.We employ uncertainty-aware deep neural networks to predict the Bragg peak depth in an anthropomorphic phantom based on secondary charged particle detection in a silicon pixel telescope designed for proton computed tomography. The subsequently predicted Bragg peak positions, along with their uncertainties, are compared to the treatment plan, rejecting spots which are predicted to be outside the 95% confidence interval. The such-produced spot rejection rate presents a metric for the quality of the treatment fraction.Main results.The introduced spot rejection rate metric is shown to be well-defined for range predictors with well-calibrated uncertainties. Using this method, treatment errors in the form of lateral shifts can be detected down to 1 mm after around 1400 treated spots with spot intensities of 1 × 107protons. The range verification model used in this metric predicts the Bragg peak depth to a mean absolute error of 1.107 ± 0.015 mm.Significance.Uncertainty-aware machine learning has potential applications in proton therapy quality control. This work presents the foundation for future developments in this area.

Abstract Objective. Gradient-based optimization using algorithmic derivatives can be a useful technique to improve engineering designs with respect to a computer-implemented objective function. Likewise, uncertainty quantification through computer simulations can be carried out by means of derivatives of the computer simulation. However, the effectiveness of these techniques depends on how ‘well-linearizable’ the software is. In this study, we assess how promising derivative information of a typical proton computed tomography (pCT) scan computer simulation is for the aforementioned applications. Approach. This study is mainly based on numerical experiments, in which we repeatedly evaluate three representative computational steps with perturbed input values. We support our observations with a review of the algorithmic steps and arithmetic operations performed by the software, using debugging techniques. Main results. The model-based iterative reconstruction (MBIR) subprocedure (at the end of the software pipeline) and the Monte Carlo (MC) simulation (at the beginning) were piecewise differentiable. However, the observed high density and magnitude of jumps was likely to preclude most meaningful uses of the derivatives. Jumps in the MBIR function arose from the discrete computation of the set of voxels intersected by a proton path, and could be reduced in magnitude by a ‘fuzzy voxels’ approach. The investigated jumps in the MC function arose from local changes in the control flow that affected the amount of consumed random numbers. The tracking algorithm solves an inherently non-differentiable problem. Significance. Besides the technical challenges of merely applying AD to existing software projects, the MC and MBIR codes must be adapted to compute smoother functions. For the MBIR code, we presented one possible approach for this while for the MC code, this will be subject to further research. For the tracking subprocedure, further research on surrogate models is necessary.

We present the performance of a full-length prototype of the ALICE Forward Calorimeter (FoCal). The detector is composed of a silicon-tungsten electromagnetic sampling calorimeter with longitudinal and transverse segmentation (FoCal-E) of about 20$X_0$ and a hadronic copper-scintillating-fiber calorimeter (FoCal-H) of about 5$\lambda_{\rm int}$. The data were taken between 2021 and 2023 at the CERN PS and SPS beam lines with hadron (electron) beams up to energies of 350 (300) GeV. Regarding FoCal-E, we report a comprehensive analysis of its response to minimum ionizing particles across all pad layers. The longitudinal shower profile of electromagnetic showers is measured with a layer-wise segmentation of 1$X_0$. As a projection to the performance of the final detector in electromagnetic showers, we demonstrate linearity in the full energy range, and show that the energy resolution fulfills the requirements for the physics needs. Additionally, the performance to separate two-showers events was studied by quantifying the transverse shower width. Regarding FoCal-H, we report a detailed analysis of the response to hadron beams between 60 and 350 GeV. The results are compared to simulations obtained with a Geant4 model of the test beam setup, which in particular for FoCal-E are in good agreement with the data. The energy resolution of FoCal-E was found to be lower than 3% at energies larger than 100 GeV. The response of FoCal-H to hadron beams was found to be linear, albeit with a significant intercept that is about factor 2 larger than in simulations. Its resolution, which is non-Gaussian and generally larger than in simulations, was quantified using the FWHM, and decreases from about 16% at 100 GeV to about 11% at 350 GeV. The discrepancy to simulations, which is particularly evident at low hadron energies, needs to be further investigated.

The CMS pixel detector will be replaced during the technical stop 2016/2017. To allow the new pixel detector to be powered with the legacy cable plant and power supplies, a novel powering scheme based on DC–DC conversion will be employed. After the successful conclusion of an extensive development and prototyping phase, mass production of 1800 DC–DC converters as well as motherboards and other power PCBs has now been completed. This contribution reviews the lessons learned from the development of the power system for the Phase-1 pixel detector, and summarizes the experience gained from the production phase.

The ``2S'' silicon strip modules for the CMS Phase-2 tracker upgrade will require two operating voltages. These will be provided via a two-step DC-DC conversion powering scheme, in which one DC-DC converter delivers 2.5 V while the second DC-DC converter receives 2.5 V at its input and converts it to 1.2 V. The DC-DC converters will be mounted on a flex PCB, the service hybrid, together with an opto-electrical converter module (VTRx+) and a serializer (LP-GBT). The service hybrid will be mounted directly on the 2S module. A prototype service hybrid has been developed and its performance has been evaluated, including radiative and conductive noise emissions, and efficiency. In addition system tests with a prototype module have been performed. In this work the service hybrid will be described and the test results will be summarized.

This paper describes prototyping work for service hybrids, flexible circuits that form an integral part of the silicon strip modules to be used in the CMS Phase-2 Outer Tracker.The service hybrid is responsible for power distribution, data serialization, and opto-electrical conversion.First prototype service hybrids, featuring the complete functionality, have been developed, produced, and characterized.In addition a first prototype of a test board, which allows to test all aspects of the complex service hybrids, as will be required during the production phase, has been developed.After a short introduction to the CMS strip modules the functionality of the service hybrid will be explained and the present prototype will be described, followed by selected test results.The test system concept will be introduced and first results will be presented.

First full size 2S module prototypes for the CMS Phase-2 Outer Tracker Upgrade have been assembled. With two sensors of realistic dimensions and 16 CBC2 readout ASICs on two front-end hybrids, the characteristics of these novel and complex objects can be studied. A MicroTCA based readout system was developed to test multiple front-end hybrids simultaneously. Therefore the concurrent information of the full module can be used for noise and signal studies.

Objective. Algorithmic differentiation (AD) can be a useful technique to numerically optimize design and algorithmic parameters by, and quantify uncertainties in, computer simulations. However, the effectiveness of AD depends on how "well-linearizable" the software is. In this study, we assess how promising derivative information of a typical proton computed tomography (pCT) scan computer simulation is for the aforementioned applications. Approach. This study is mainly based on numerical experiments, in which we repeatedly evaluate three representative computational steps with perturbed input values. We support our observations with a review of the algorithmic steps and arithmetic operations performed by the software, using debugging techniques. Main results. The model-based iterative reconstruction (MBIR) subprocedure (at the end of the software pipeline) and the Monte Carlo (MC) simulation (at the beginning) were piecewise differentiable. Jumps in the MBIR function arose from the discrete computation of the set of voxels intersected by a proton path. Jumps in the MC function likely arose from changes in the control flow that affect the amount of consumed random numbers. The tracking algorithm solves an inherently non-differentiable problem. Significance. The MC and MBIR codes are ready for the integration of AD, and further research on surrogate models for the tracking subprocedure is necessary.

The CMS Phase-1 pixel detector and the CMS Phase-2 tracker are upgrade detectors for the silicon tracker of the CMS experiment at LHC, CERN. The upgrades are inevitable for the efficient performance of the CMS tracker at higher instantaneous and integrated luminosities of the LHC and the HL-LHC, respectively. The Phase-1 pixel detector was installed in winter2016/2017 and the Phase-2 upgrade tracker will be installed from 2025 to 2027.The detectors will experience radiation damage at levels which are nearly an order of magnitude higher than the values the original detectors were designed for. The higher radiation damage leads to higher leakage currents in the silicon sensors, because of induced defects in the crystal lattice. Their values depend approximately exponentially on the sensor temperature, with roughly a factor 2 at a temperature increase of 7 K. The effect of thermal runaway, which denotes the non-linear self-heating of the silicon sensors because of their leakage current, will eventually make the detectors inoperative. By cooling the detectors to low temperatures, the leakage current scan be drastically mitigated and their longevity enhanced. Hence, the thermal performance of the cooling structure is crucial for the operation. Coolant temperatures (a few 10 K below 0 °C) are necessary. The mechanics of the detectors have to be optimized for small temperature gradients in the order of 10 K between the silicon sensors and the coolant. Both detectors use the concept of evaporative CO 2 cooling systems at nominal coolant temperatures of −22 °C and −35 °C, respectively. Thermal measurements with test prototypes, so-called thermal dummies or mock-ups, are an important part of the detector design and construction. This thesis presents measurements and characterizations of the thermal properties for the Phase-1 barrel pixel detector and for the 2S modules of the Phase-2 Upgrade tracker with evaporative CO2 cooling systems. Within the CMS Tracker collaboration, the results of both measurement projects contributed substantially to the understanding of the thermal properties of these detectors. For the Phase-2 part, a detailed characterization of the thermal properties of the 2S module is presented. The 2S module is a silicon strip module with two silicon sensors and three electronic hybrids. Typical power values are 5.4 W for the hybrids and 0.3 to 0.5 W for each sensor. Dummy2S modules were built and systematic thermal measurements were made. A dedicated test setup was developed, constructed, and commissioned. A custom CO2 system with a cooling temperature of −30 °C was used. The thermal resistance of the sensors to the cooling system was measured with bare modules with no hybrids attached and the thermal coupling of the sensors to the ambient was estimated. The thermal performance of a fully assembled 2S module with hybrids and wire bonds is studied. The effect of thermal runaway is demonstrated. All test results are directly compared to predictions from Finite Element simulations which have been developed. The mechanical assumptions made in the Finite Element model could be confirmed with measurements. For the Phase-1 part, thermal measurements with a thermal mock-up of one Layer 2 barrel pixel detector half-shell and 114 thermal pixel dummy modules were conducted. The measurements were made with a LUKASZ CO2 cooling system. At the full heat load of 200 W temperature drops of 4 to 5 K along one cooling line could be observed because of pressure drops in the two-phase CO2 in the pipes. The temperature gradient in the detector leads to a systematic temperature distribution in the detector. This effect directly affects the temperature dependent leakage currents of the silicon pixel sensors. The observed leakage current distributions with relative factors of 1.4 between power sectors in the real BPIX detector are compatible with the predictions from the measurements with the mock-up. It was predicted from the measurements and shown in the real detector that changing the CO2 mass flow reduces the temperature gradients in the detector.

The clock system provides bunch crossing related timing signals to various detector subsystems. Accelerator synchronization and monitoring as well as timing signal generation and distribution are discussed. The system is built using three module types implemented in Eurostandard hardware with a VME communications interface. The first two types of module are used to facilitate synchronization with the accelerator and to generate 23 timing signals that are programmable with one RF bucket (18.8 ns) resolution and 1-ns accuracy. Fifty-four of the third module type are used to distribute the timing signals and two synchronous 53-MHz and 106-MHz clocks to various detector subsystems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The clock system provides bunch-crossing-related timing signals to various detector subsystems. Accelerator synchronization and monitoring as well as timing signal generation and distribution are discussed. The system was built using three module types implemented in Eurostandard hardware with a VME communications interface. The first two types of modules were used to facilitate synchronization with the accelerator and to generate 23 timing signals that were programmable with one RF bucket (18.8-ns) resolution and 1-ns accuracy. Fifty-four modules of the third type were used to distribute the timing signals and two synchronous 53-MHz and 106-MHz clocks to various detector subsystems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>