Nikkie Deelen

Particle physics experiments make use of magnetic fields up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$4 \,\mathrm{T}$</tex-math></inline-formula> to bend electrically charged particles such that their charge and momentum can be determined. The particle energy measurement requires a low amount of material, or material that is highly transparent to particles inside the calorimeter volume. The conflict between the small volume of space reserved for a magnet and having a field of several teslas inside the detector is often resolved by using superconducting magnets. Up to now, large particle physics detector magnets have been constructed with low temperature superconductors, but there are clear benefits from using high temperature superconductors in future particle physics detector designs, such as allowing for an elevated operating temperature and the reduced amount of superconductor needed. In addition to the HTS material itself, additional material is needed to support the Lorentz forces, and to temporarily carry the current in case of a quench since these magnets are always one-of-a-kind and they need to operate reliably and without damage in case of a failure scenario. The stabilizer has to be a low-density material for high particle transparency, such as aluminium. Since the density of the superconductor is a factor of 4 higher than the density of aluminium, a reduction of superconducting material also means an improvement of the particle transparency: the density of a material is directly related to its particle transparency. This paper presents a conceptual design for high temperature superconducting detector magnets and a study of the type of aluminium stabilizer used.

Various superconducting detector solenoids for particle physics have been developed in the world. The key technology is the aluminum-stabilized superconducting conductor for almost all the detector magnets in particle physics experiments. With the progress of the conductor, the coil fabrication technology has progressed as well, such as the inner coil winding technique, indirect cooling, transparent vacuum vessel, quench protection scheme using pure aluminum strips and so on. The detector solenoids design study is in progress for future big projects in Japan and Europe, that is, ILC, FCC and CLIC, based on the technologies established over many years. The combination of good mechanical properties and keeping a high RRR is a key point for the development of Al-stabilized conductor. The present concern for the detector solenoid development is to have been gradually losing the key technologies and experiences, because large-scale detector magnets with Al-stabilized conductor has not been fabricated after the success of CMS and ATLAS-CS in LHC. Complementary efforts are needed to resume an equivalent level of expertise, to extend the effort on research and to develop these technologies and apply them to future detector magnet projects. Especially, further effort is necessary for the industrial technology of Al-stabilized superconductor production. The worldwide collaboration with relevant institutes and industries will be critically important to re-realize and validate the required performances. Some detector solenoids for mid-scale experiment wound with conventional copper-stabilized Nb-Ti conductor require precise control of magnetic field distribution. The development efforts are on-going in terms of the magnetic field design technology with high precision simulation, coil fabrication technology and control method of magnetic field distribution.

The Rasnik alignment system was developed initially in 1983 for the monitoring of the alignment of the muon chambers of the L3 Muon Spectrometer at CERN. Since then, the development has continued as new opto-electronic components become available. Rasnik systems are 3-point optical displacement monitors and their precision ranges from below nanometers to several micrometers, depending on the design and requirements of the systems. A result, expressed in the range/precision ratio of 2 × 106, is presented. According to the calculations of the Cram&aposer-Rao limit, and by means of MonteCarlo simulations, a typical Rasnik image should have enough information to reach deep sub-nanometer precision. This paper is an overview of the technological developments and achievements since Rasnik was applied in high energy physics experiments.

As part of the European Strategy for Particle Physics there is an ongoing development towards a Future Circular Collider (FCC-ee) where electron-positron collisions could be used to study the entire electro-weak sector in a low background environment. Particle detectors are used to study these collisions and a strong magnetic field is required to measure the particles’ momenta. Currently, two detector concepts are being studied: the Innovative Detector for Electron-positron Accelerators (IDEA) and the CLIC-Like Detector (CLD). Both these detectors include a superconducting solenoid magnet with a central field of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2 \,\mathrm{T}$</tex-math></inline-formula> of which the designs are presented here. The IDEA magnet has an stored magnetic energy density of 14 kJ/kg and in CLD this is 12 kJ/kg. Taking into account their respective free-bore diameters of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$4.2 \,\mathrm{m}$</tex-math></inline-formula> for IDEA and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$7.2 \,\mathrm{m}$</tex-math></inline-formula> for CLD this results in very challenging designs for which the mechanical and quench studies are presented. Their results are promising, but extensive R&D on these magnets would be needed in the future to reach the goals set out in the Conceptual Design Report (CDR).

Arc suppression Snubbers offer safety in high energy superconducting magnet systems. Large superconducting magnets may have arcing across their breakers at the moment of slow dump initiation resulting from a sudden current redistribution in the powering circuit. The ATLAS Experiment at CERN experiences such arcing with its 7.3 H Toroidal magnet powering circuit. To discharge the magnets, the current is redistributed to a parallel branch called the Run Down Unit (RDU) by means of a breaker. Due to the physical layout and other metallic components in the vicinity, the power supply and RDU branches have undesirable and unavoidable parasitic inductance, causing a voltage spike over the main breakers at the moment of opening. The resulting arcing deteriorates the breaker contacts, resulting in increased operating temperatures and a more frequent need for maintenance. The arc suppression system developed takes the form of an RC Snubber (Resistor-Capacitor). The Snubber offers the current a low-impedance path, thus smoothing out the current redistribution and suppressing the voltage spike. This initial charging period of the capacitors gives the current enough time to overcome the parasitic inductance, therefore allowing the RDU to smoothly ramp up without a sudden voltage spike. To test the concept, a 1/50th scale demonstrator was developed and showed successful results. After the demonstrator, endurance testing of the electrolytic capacitors was performed to ensure no degradation of the charging characteristics for an equivalent of 20 years of operation. The Snubber was manufactured and implemented with successful results on the ATLAS Toroidal powering circuit.

This thesis is on the research of tuning the Foward Calorimeter (FoCal) prototype detector with cosmic muons. First the performance of the prototype detector was investigated. An important result was that the detector prototype response was stable in time. In order to estimate the detector performance, the amount of lost triggers and lost tracks were investigated too. During this study it was found that (3 ± 2) % of the triggers was lost during a measurement and that (50 ± 3) % of the tracks was lost with the present version of the software (code13052013). An understanding of what is causing this problem has not yet been reached. The second part of the investigation was meant to come to an understanding of how the chips in the detector can be tuned using cosmic muons. For this purpose, one of the chip parameters was changed (P1 ) and the results were analysed. It was found that some of the chips were already operating with good P1 settings but for other chips better settings were obtained. There were also some patterns discovered of how the P1 chip settings relate to results of a measurement.

Various superconducting detector solenoids for particle physics have been developed in the world. The key technology is the aluminum-stabilized superconducting conductor for almost all the detector magnets in particle physics experiments. With the progress of the conductor, the coil fabrication technology has progressed as well, such as the inner coil winding technique, indirect cooling, transparent vacuum vessel, quench protection scheme using pure aluminum strips and so on. The detector solenoids design study is in progress for future big projects in Japan and Europe, that is, ILC, FCC and CLIC, based on the technologies established over many years. The combination of good mechanical properties and keeping a high RRR is a key point for the development of Al-stabilized conductor. The present concern for the detector solenoid development is to have been gradually losing the key technologies and experiences, because large-scale detector magnets with Al-stabilized conductor has not been fabricated after the success of CMS and ATLAS-CS in LHC. Complementary efforts are needed to resume an equivalent level of expertise, to extend the effort on research and to develop these technologies and apply them to future detector magnet projects. Especially, further effort is necessary for the industrial technology of Al-stabilized superconductor production. The worldwide collaboration with relevant institutes and industries will be critically important to re-realize and validate the required performances. Some detector solenoids for mid-scale experiment wound with conventional copper-stabilized Nb-Ti conductor require precise control of magnetic field distribution. The development efforts are on-going in terms of the magnetic field design technology with high precision simulation, coil fabrication technology and control method of magnetic field distribution.

Various superconducting detector solenoids for particle physics have been developed in the world. The key technology is the aluminum-stabilized superconducting conductor for almost all the detector magnets in particle physics experiments. With the progress of the conductor, the coil fabrication technology has progressed as well, such as the inner coil winding technique, indirect cooling, transparent vacuum vessel, quench protection scheme using pure aluminum strips and so on. The detector solenoids design study is in progress for future big projects in Japan and Europe, that is, ILC, FCC and CLIC, based on the technologies established over many years. The combination of good mechanical properties and keeping a high RRR is a key point for the development of Al-stabilized conductor. The present concern for the detector solenoid development is to have been gradually losing the key technologies and experiences, because large-scale detector magnets with Al-stabilized conductor has not been fabricated after the success of CMS and ATLAS-CS in LHC. Complementary efforts are needed to resume an equivalent level of expertise, to extend the effort on research and to develop these technologies and apply them to future detector magnet projects. Especially, further effort is necessary for the industrial technology of Al-stabilized superconductor production. The worldwide collaboration with relevant institutes and industries will be critically important to re-realize and validate the required performances. Some detector solenoids for mid-scale experiment wound with conventional copper-stabilized Nb-Ti conductor require precise control of magnetic field distribution. The development efforts are on-going in terms of the magnetic field design technology with high precision simulation, coil fabrication technology and control method of magnetic field distribution.

Since its start-up in $2008$ the Large Hadron Collider has been producing proton-proton collisions with a center-of-mass energy approaching $14\,\text{TeV}$ for high-energy physics experiments at the European Center for Nuclear research. The resulting physics events are studied by four large experiments around the $27\,\text{km}$ collider ring one of them being the Compact Muon Solenoid detector. To boost the discovery potential of the Large Hadron Collider it will be upgraded in several phases, such that its particle interaction flux will be increased from $1\cdot10^{34}\,\text{cm}^{-2}\text{s}^{-1}$ to $5\cdot10^{34}\,\text{cm}^{-2}\text{s}^{-1}$. This is referred to as the High Luminosity Upgrade. Consequently, the four large experiments at the laboratory will be improved as well to cope with these operating conditions. This research is focused on the characterization of prototype modules designed for the upgrade of the Compact Muon Solenoid's tracking sub-detector. It is composed of the Inner Tracker at its center that is surrounded by the Outer Tracker. The prototype modules under study consist of silicon pixel sensors and silicon strip sensors for the Inner and Outer Tracker, respectively. Prototype front-end readout chips are connected to the sensors for the initial signal processing. These are mounted on printed circuit boards that are used to supply power to, and to extract data from the readout chips. In the first part of this thesis the calibration of the threshold setting of the prototype binary front-end chips for the Outer Tracker is described. The second part covers a beam test setup that was designed, build, and tested with the aim to perform high-rate studies ($1\,\text{MHz}$) with the tracker prototypes. This kind of setup can be used to characterize any kind of silicon tracker module in particle beams. Due to the technology that is used to produce the binary readout chips a $10\,\%$ difference in response and threshold calibration value is expected between chips and their individual readout channels. For this reason, a method to calibrate this threshold setting was developed. This method makes use of fluorescent, or radioactive photons of a single energy that irradiate the silicon sensors while a threshold scan is executed with the binary chip. The threshold setting corresponding to the signal in the silicon can be extracted from the scan by estimating at what value the number of particle hits per event reaches zero. A calibration curve is obtained by repeating the threshold scan with photons of different energies, and from this curve the gain of the binary front-end readout chip can be estimated. The average calibration value found for the thus far tested readout chips, expressed as the signal induced in silicon, was $367$ electrons per threshold unit. Different calibration values for different chips and readout channels were measured. For the chips used in this research the differences were not greater than $10\,\%$. A toy Monte-Carlo simulation was developed in order to study the results of the thresholds scans in further detail. This simulation included a simple model for the charge sharing between the strips of the silicon sensors. As a preparation for high-rate beam studies with Upgrade Tracker modules that can measure particle fluxes of up to $100\,\text{MHz}/\text{cm}^2$, a new beam telescope was developed. This telescope can be used to reconstruct particle tracks that are then compared to clusters measured by a prototype module that is placed in the center of the setup. Commonly used beam telescopes have a $4600$ times slower readout $113\,\mu\text{m}$ versus $25\,\text{ns}$) than the tracker prototypes concerned in this research. Therefore, this new setup dedicated to stress testing prototype tracker modules was build with pixel detectors with the same readout speed as the tracker prototypes. To validate the setup it was tested in a particle beam with a prototype tracker module installed in its center. The tracking resolution of the telescope was determined to be $7\,\mu\text{m}$ in the horizontal, and $10\,\mu\text{m}$ in the vertical direction. This is better than what was expected from a straight line fit that takes as the uncertainty of the hit locations measured by the telescope $100\,\mu\text{m}/\sqrt{12}$ and $150\,\mu\text{m}/\sqrt{12}$, where $100\,\mu\text{m}$ is the pixel pitch in the horizontal direction and $150\,\mu\text{m}$ the pixel pitch in the vertical direction. This was explained by the charge-sharing between the pixels of the telescope modules that allows for having sub-pixel precision on the location of the particle hit. Tests with a Tracker prototype module in the the center of the new beam telescope confirmed that it is fully operational and ready for use in high-rate studies. Both the telescope and the prototype tracker module could be readout simultaneously. This was confirmed by a clear correlation between the tracks reconstructed with the telescope data, and the particle hit positions found with the new tracker module.