Karol Buńkowski

In view of an upgrade of the CMS experiment, the GEM for CMS collaboration is performing feasibility studies on employing Triple-GEM detectors for the high-η region (1.6–2.4) of the CMS endcaps. A detailed review of the development and characterization of the CMS full-size prototype baseline detector will be presented. GEMs have excellent spatial and time resolution, high rate capability and radiation hardness, they are an appealing option for simultaneously enhancing muon tracking and triggering capabilities in the high-η region. The GEM for CMS collaboration has studied the performance of small and full-size prototype detectors during several test beam campaigns in order to validate new technologies and techniques in view of a mass production for CMS experiment. Results from measurements with x-rays and from test beam campaigns at the CERN SPS will be shown from both small and large prototypes.

The PAC (pattern comparator) is a dedicated muon trigger for the CMS (Compact Muon Solenoid) experiment at the LHC (Large Hadron Collider). The PAC trigger processes signals provided by RPC (resistive plate chambers), a part of the CMS muon system. The goal of the PAC RPC trigger is to identify muons, measure their transverse momenta and select the best muon candidates for each proton bunch collision occurring every 25 ns. To perform this task it is necessary to deliver the information concerning each bunch crossing from many RPC chambers to the trigger logic at the same moment. Since the CMS detector is large (the muon hits are spread over 40 ns), and the data are transmitted through thousands of channels, special techniques are needed to assure proper synchronization of the data. In this paper methods developed for the RPC signal synchronization and synchronous transmission are presented. The methods were tested during the MTCC (magnet test and cosmic challenge). The performance of the synchronization methods is illustrated by the results of the tests.

At present, part of the forward RPC muon system of the CMS detector at the CERN LHC remains uninstrumented in the high-\eta region. An international collaboration is investigating the possibility of covering the 1.6 < |\eta| < 2.4 region of the muon endcaps with large-area triple-GEM detectors. Given their good spatial resolution, high rate capability, and radiation hardness, these micro-pattern gas detectors are an appealing option for simultaneously enhancing muon tracking and triggering capabilities in a future upgrade of the CMS detector. A general overview of this feasibility study will be presented. The design and construction of small (10\times10 cm2) and full-size trapezoidal (1\times0.5 m2) triple-GEM prototypes will be described. During detector assembly, different techniques for stretching the GEM foils were tested. Results from measurements with x-rays and from test beam campaigns at the CERN SPS will be shown for the small and large prototypes. Preliminary simulation studies on the expected muon reconstruction and trigger performances of this proposed upgraded muon system will be reported.

During the summer 2006, a first integrated test of a part of the CMS experiment was performed at CERN collecting a data sample of several millions of cosmic rays events. A fraction of the Resistive Plate Chambers system was successfully operated. Results on the RPC performance are reported.

The CMS GEM collaboration is considering Gas Electron Multipliers (GEMs) for upgrading the CMS forward muon system in the 1.5 <; |η| <; 2.4 endcap region. GEM detectors can provide precision tracking and fast trigger information. They would improve the CMS muon trigger and muon momentum resolution and provide missing redundancy in the high-η region. Employing a new faster construction and assembly technique, we built four full-scale Triple-GEM muon detectors for the inner ring of the first muon endcap station. We plan to install these or further improved versions in CMS during the first long LHC shutdown in 2013/14 for continued testing. These detectors are designed for the stringent rate and resolution requirements in the increasingly hostile environments expected at CMS after the second long LHC shutdown in 2018/19. The new prototypes were studied in muon/pion beams at the CERN SPS. We discuss our experience with constructing the new full-scale production prototypes and present preliminary performance results from the beam test. We also tested smaller Triple-GEM prototypes with zigzag readout strips with 2 mm pitch in these beams and measured a spatial resolution of 73 μm. This readout offers a potential reduction of channel count and consequently electronics cost for this system while maintaining high spatial resolution.

The paper presents the concept of the Overlap Muon Track Finder (OTF) trigger for the CMS experiment in CERN as a system implemented in the modern FPGA device. The parametrized description of the complex data processing system, allowing further optimization by iterative simulations and recompilations, is presented. Problems associated with synthesis of such complex systems with currently available synthesis tools, and their workarounds are described.

The dedicated CMS R&D program was intended to study the feasibility of using micropattern detectors for the instrumentation of the vacant |η|>1.6 region in the present Resistive Plate Chambers (RPCs) endcap system. The proposed detector for CMS is a Triple-Gas Electron Multiplier (GEM) trapezoidal chamber, equipped with 1D readout. While during 2010–2011 the Collaboration worked on the prototyping of the detector, during the first part of 2012 a newly developed assembly technique to be used for the mass production was adopted. GEMs can provide precision tracking and fast trigger information, contributing on one hand to the improvement of the CMS muon Trigger and on the other hand to provide the missing redundancy in the high η region. In the view of the next LHC long shutdown (LS1) the CMS GEM Collaboration designed and built four full-size Triple GEM-based muon detectors.

The Overlap Muon Track Finder (OMTF) is the new system developed during the upgrade of the CMS experiment which includes the upgrade of its Level-1 trigger. It uses the novelty approach to finding muon candidates based on data received from three types of detectors: RPC, DT, and CSC . The upgrade of the trigger system requires also upgrade of the associated Data Acquisition (DAQ) system. The OMTF DAQ transmits the data from the connected detectors that were the basis for the Level-1 trigger decision. To increase its diagnostic potential, it may also transmit the data from a few bunch crossings (BXes) preceding or following the BX, in which the L1 trigger was generated. The paper describes the technical concepts and solutions used in the OMTF DAQ system. The system is still under development. However, it successfully passed the first tests.

The results of proton irradiation test of electronic devices, selected for the RPC trigger electronic system of the CMS detector, will be presented. For Xilinx Spartan-IIE FPGA the cross-section for Single Event Upsets (SEUs) in configuration bits was measured. The dynamic SEUs in flip-flops were also investigated, but not observed. For the FLASH memories no single upsets were detected. Only after irradiating with a huge dose permanent damages of devices were observed. For Synchronous Dynamic Random Access Memory (SDRAM), the SEU cross-section was measured.

The CMS GEM collaboration is considering Gas Electron Multipliers (GEMs) for upgrading the CMS forward muon system in the 1.5<|eta|<2.4 endcap region. GEM detectors can provide precision tracking and fast trigger information. They would improve the CMS muon trigger and muon momentum resolution and provide missing redundancy in the high-eta region. Employing a new faster construction and assembly technique, we built four full-scale Triple-GEM muon detectors for the inner ring of the first muon endcap station. We plan to install these or further improved versions in CMS during the first long LHC shutdown in 2013/14 for continued testing. These detectors are designed for the stringent rate and resolution requirements in the increasingly hostile environments expected at CMS after the second long LHC shutdown in 2018/19. The new prototypes were studied in muon/pion beams at the CERN SPS. We discuss our experience with constructing the new full-scale production prototypes and present preliminary performance results from the beam test. We also tested smaller Triple-GEM prototypes with zigzag readout strips with 2 mm pitch in these beams and measured a spatial resolution of 73 microns. This readout offers a potential reduction of channel count and consequently electronics cost for this system while maintaining high spatial resolution.

This paper presents the implementation of the data acquisition system of the Resistive Plate Chamber (RPC) subdetector in the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) in CERN. The described readout system connects with the RPC detector, the RPC link system, the RPC trigger system and the CMS data acquisition system and creates one of multiple metrological systems in CMS experiment. The readout system receives the data provided by the multiple channels of the link system, filters out the non-triggered data, encapsulates the data into the standard CMS common data format events and sends them to the global data acquisition system. The main problem in the readout system design was to provide a sufficiently large throughput to reliably transfer the data. The implemented system is the scalable solution based on advanced Field Programmable Gate Arrays (FPGA) technology.

This paper describes firmware architecture of a new part of muon trigger system of the CMS detector – one of four detectors installed along LHC accelerator in CERN. Overlap Muon Track Finder (OMTF) is a new trigger subsystem designed to work in difficult barrel-endcap region of CMS detector. OMTF is designed to receive data from different detector types and process it to select 3 best muon candidates. These muon candidates are then forwarded to Global Muon Trigger (GMT). Performance requirements demanded usage of custom designed hardware. All the data reception and processing takes part in modern, large FPGA device. The IPBus module allows easy firmware control and diagnostics via Ethernet connection.

The article describes the algorithm of finding the highest transverse momentum muon based on the signals from fast RPC detectors in CMS experiment at the LHC collider in CERN (Geneva). Very fast progress in FPGA performance makes it possible to build Pattern Comparator Processor (PAC) using this technology. Compilation and simulation of different configurations of PAC are discussed. Improved algorithm which requires smaller resources in the FPGAs is presented.

The CMS muon system is conceived for trigger and muon track reconstruction. The redundancy and robustness of the system are guaranteed by three complementary subsystems: drift tube in the barrel, cathode strip chamber in the end-cap and resistive plate chamber in barrel and end-cap. The installation of muon stations and read-out trigger electronic has been completed in middle 2007. Since than, a remarkable effort has been addressed to the detector commissioning in order to ensure the readiness of the hardware/software chain for the LHC start up operation. At the end of 2007, a test of an entire CMS slice has been performed, involving about 5% of muon stations. Several thousand cosmic muons events have been collected. Performance of the barrel chambers are reported.

In the CERN CMS experiment at LHC Collider special trigger signals called Technical Triggers will be used for the purpose of test and calibration. The Resistive Plate Chambers (RPC) based Technical Trigger system is a part of the CMS muon trigger system and is designed to detect cosmic muon tracks. It is based on two boards, namely RBC (RPC Balcony Collector) and TTU (Technical Trigger Unit). The proposed tracking algorithm (TA) written in VHDL and implemented in the TTU board detects single or multiple cosmic muon tracks at every bunch crossing along with their track lengths and corresponding chamber coordinates. The TA implementation in VHDL and its preliminary simulation results are presented.

GEM detectors are used in high energy physics experiments given their good spatial resolution, high rate capability and radiation hardness. An international collaboration is investigating the possibility of covering the 1.6 < |η| < 2.4 region of the CMS muon endcaps with large-area triple-GEM detectors. The CMS high-η area is actually not fully instrumented, only Cathode Strip Chamber (CSC) are installed. The vacant area presents an opportunity for a detector technology able to to cope with the harsh radiation environment; these micropattern gas detectors are an appealing option to simultaneously enhance muon tracking and triggering capabilities in a future upgrade of the CMS detector. A general overview of this feasibility study is presented. Design and construction of small (10cm × 10cm) and full-size trapezoidal (1m × 0.5m) triple-GEM prototypes is described. Results from measurements with x-rays and from test beam campaigns at the CERN SPS is shown for the small and large prototypes. Preliminary simulation studies on the expected muon reconstruction and trigger performances of this proposed upgraded muon system are reported.

Gas Electron Multipliers (GEM) are an interesting technology under consideration for the future upgrade of the forward region of the CMS muon system, specifically in the 1.6 <; |η| <; 2:4 endcap region. With a sufficiently fine segmentation GEMs can provide precision tracking as well as fast trigger information. The main objective is to contribute to the improvement of the CMS muon trigger. The construction of large-area GEM detectors is challenging both from the technological and production aspects. In view of the CMS upgrade we have designed and built the largest full-size Triple-GEM muon detector, which is able to meet the stringent requirements given the hostile environment at the high-luminosity LHC. Measurements were performed during several test beam campaigns at the CERN SPS in 2010 and 2011. The main issues under study are efficiency, spatial resolution and timing performance with different inter-electrode gap configurations and gas mixtures. In this paper results of the performance of the prototypes at the beam tests will be discussed.

In the CMS experiment, sub-detectors may send special trigger signals, called “Technical Triggers”, for purposes like test and calibration. The Resistive Plate Chambers are part of the Muon Trigger System of the experiment, but might also produce a cosmic muon trigger to be used during the commissioning of the detectors, the CMS Magnet Test-Cosmic Challenge and the later running of CMS. The proposed implementation is based on the development of a new board, the RPC Balcony Collector (RBC); the test results on prototypes and their performance during the recent CMS Cosmic Challenge are presented.

The CMS L1 Trigger electronics are composed of a large number of different cards based on the VMEBus standard. The majority of the system is being replaced to adapt the trigger to the higher collision rates the LHC will deliver after the LS1, the first phase on the CMS upgrade program. As a consequence, the software that controls, monitors and tests the hardware will need to be re-written. The upgraded trigger will consist of a set of general purpose boards of similar technology that follow the TCA specification, thus resulting in a more homogeneous system. A great effort has been made to identify the common firmware blocks and components shared across different cards, regardless of the role they play within the trigger data path. A similar line of work has been followed in order to identify all possible common functionalities in the control software, as well as in the database where the hardware initialisation and configuration data are stored. This will not only increase the homogeneity on the software and database sides, but it will also reduce the manpower needed to accommodate the online SW to the changes on hardware. Due to the fact that the upgrade will take place in different stages, it has been taken into consideration that these new components had to be integrated in the current SW framework. This paper presents the design of the control SW and configuration database for the upgraded L1 Trigger.

The results of proton radiation test of electronic devices for RPC trigger electronic system of CMS detector are presented. For Xilinx Spartan-IIE FPGA the cross section for Single Event Upsets (SEUs) in configuration bits was measured. The dynamic SEUs in flip-flops was also investigated, but not observed. For the FLASH memories no single upsets were detected, but after a huge dose permanent damages of devices were observed. For SDRAM memories, the SEU cross section was measured. A brief description of radiation inducted effects in FPGAs, SRAM and FLASH memories is also presented.

The Resistive Plate Chambers [M. Abbrescia, et al., Nucl. Instr. and Meth. A 550 (2005) 116] are used in the CMS experiment [CMS Collaboration, The CMS experiment at the CERN LHC 2008, J. Inst. 3 (2008) S08004] as a dedicated muon trigger both in barrel and endcap system. About 4000m2 of double gap RPCs have been produced and have been installed in the experiment since more than one and half Years. The full barrel system and a fraction of the endcaps have been monitored to study dark current behaviour and system stability, and have been extensively commissioned with Cosmic Rays collected by the full CMS experiment.

1 Structure 2 My contribution 2 Chapter 2 LHC and CMS detector 5 Chapter summary 5 2.1 LHC 5 The main physic goals of the LHC 7 2.2 An overview of the CMS detector 7 2.2.1 Subdetectors 8 Tracker 8 Electromagnetic Calorimeter 9 Hadron Calorimeter 9 Muon system 10 2.3 Trigger and data acquisition 11 2.3.1 Level-1 Trigger 11 Calorimeter L1 Trigger 13 Muon L1 Trigger 13 Physic requirements for the Muon Trigger 13 The architecture of the Level-1 Muon Trigger 15 Global Trigger 16 Trigger Control System (TCS) and Timing Trigger and Control (TTC) System ......... 17 TCS system 17 TTC system 17 2.3.2 Data Acquisition System 18 Event Filter 18 2.4 CMS online software framework 19 XDAQ 20 Run Control and Monitor System (RCMS) 20 Trigger Supervisor (TS) 21 Detector Control System (DCS) 21

This paper describes the design of the Link Box Control System for the RPC Detector (RLBCS), emphasizing the features needed to assure reliable operation in the irradiated environment of the RPC detector and its neighbourhood. The development process required to balance different factors - radiation hardness, reliability, flexibility, firmware upgrade possibilities, diagnostic features. The final design presented in the paper is a result of compromise between the above requirements.

This paper presents a FPGA based DSP system for realtime simulation of superconducting accelerator's cavity. The superconducting linacs require sophisticated control systems for maintaining the constant amplitude and phase of accelerating field in the accelerator's cavities. The debugging of these systems on real hardware can be both difficult and dangerous. To allow testing of the real LLRF systems in the real time and with different cavity parameters, the FPGA based system has been developed.

The resistive plate chambers (RPCs) muon trigger electronics of the Compact Muon Solenoid (CMS) detector performs a number of tasks: synchronization of detector signals, optical data transmission from the detector to the trigger electronics, pattern recognition, muons momentum measurement, selection of track candidates. For the diagnostic purposes, as well as for the calibration and real-time monitoring of the RPC detectors and electronic hardware, a set of flexible diagnostic modules was designed and implemented into the field programmable gate arrays on which the trigger electronics is based. These include: multichannel counters, timing histograms, test pulses generators, diagnostic readout and data spying ("snap-shots" of the data stream). Test results presented in this paper, including tests with Large Hadron Collider-like muon beam, illustrate the performance and the usefulness of these diagnostic modules

Gas Electron Multipliers (GEM) are an interesting technology under consideration for the future upgrade of the forward region of the CMS muon system, specifically in the $1.6<| \eta |<2.4$ endcap region. With a sufficiently fine segmentation GEMs can provide precision tracking as well as fast trigger information. The main objective is to contribute to the improvement of the CMS muon trigger. The construction of large-area GEM detectors is challenging both from the technological and production aspects. In view of the CMS upgrade we have designed and built the largest full-size Triple-GEM muon detector, which is able to meet the stringent requirements given the hostile environment at the high-luminosity LHC. Measurements were performed during several test beam campaigns at the CERN SPS in 2010 and 2011. The main issues under study are efficiency, spatial resolution and timing performance with different inter-electrode gap configurations and gas mixtures. In this paper results of the performance of the prototypes at the beam tests will be discussed.

The main task of the RPC (Resistive Plate Chamber) Muon Trigger monitoring system design for the CMS (Compact Muon Solenoid) experiment (at LHC in CERN Geneva) is the visualization of data that includes the structure of electronic trigger system (e.g. geometry and imagery), the way of its processes and to generate automatically files with VHDL source code used for programming of the FPGA matrix. In the near future, the system will enable the analysis of condition, operation and efficiency of individual Muon Trigger elements, registration of information about some Muon Trigger devices and present previously obtained results in interactive presentation layer. A broad variety of different database and programming concepts for design of Muon Trigger monitoring system was presented in this article. The structure and architecture of the system and its principle of operation were described. One of ideas for building this system is use object-oriented programming and design techniques to describe real electronics systems through abstract object models stored in database and implement these models in Java language.

The Muon System of the CMS experiment at CERN employees three different detector technologies—Drift Tube Chambers (DT) in the barrel part, Cathode Strip Chambers (CSC) in the endcaps and Resistive Plate Chambers (RPC) both in the barrel and the endcaps. TDs and CSCs serve as precise muon trajectory measurement devices. The RPCs are responsible for the bunch crossing identification and for a fast muon transverse momentum measurement. The total number of RPCs is 480 in the barrel and 756 in the endcaps, covering an area of about 3500 square meters. A brief overview of the system will be presented as well as some recent results about the system stability and performance.

The CMS detector will start its operation in the end of 2007. Until that time great care must be taken in order to assure that hardware operation is fully understood. In this paper an example of how emulation software helps achieving this goal in the CMS Level-1 RPC Trigger system is presented. The design of the RPC trigger allows to insert sets of so-called test pulses at any stage of the hardware pipeline. Reading out data from different stages is also possible. Such design allows for easy debugging of the trigger hardware by comparing hardware and software emulation values, since the software and hardware algorithms are identical.

The CMS Level-1 trigger, based on custom electronics built around FPGA devices, was upgraded in 2016 to achieve the required performance with almost two times higher LHC luminosity than originally designed. The upgraded Level-1 muon trigger merges data from the three muon detectors in the CMS (DT, CSC, and RPC) in the track reconstruction stage — contrary to the legacy trigger which comprised three separate systems each based on one muon detector. This approach allows better use of the detector redundancy and improved measurement of the muon transverse momentum. However, it is particularly challenging in the barrel-endcap transition region, where up to 18 muon chamber layers are present, the detector geometry is complex, and the magnetic field bending the muon tracks is heterogeneous. For this region the Overlap Muon Track Finder (OMTF) uses a novel algorithm based on a naive Bayes classifier. The algorithm identifies the muon tracks and measures their momentum by calculating the probabilities of matching the detector hits to defined transverse momentum hypotheses. The algorithm was tailored to the needs of muon measurements based on the detector data (e.g. to cope with missing hits or multi-muon events) and implementation in FPGA technology. The algorithm details, performance, and optimization methods are discussed in this report.

The RPC muon trigger electronics of the CMS detector performs a number of tasks: synchronization of detector signals, optical data transmission from the detector to the trigger electronics, pattern recognition, muon momentum measurement, selection of track candidates. For the diagnostic purposes, as well as for the calibration and real-time monitoring of the RPC detectors and electronic hardware, a set of flexible diagnostic modules was designed and implemented into the FPGAs on which the trigger electronics is based. These include: multi-channel counters, timing histograms, test pulses, and data spying ("snapshots" of the data stream). Tests results presented in this paper, including test with LHC-like muon beam, illustrate the performance and usefulness of these diagnostic modules.

In this paper the object oriented hardware-software model and its sample implementation of diagnostics for the Overlap Muon Track Finder trigger for the CMS experiment in CERN is described. It presents realization of test-bench for control and diagnosis class of multichannel, distributed measurement systems based on FPGA chips. The test-bench fulfills requirements for system’s rapid changes, configurability and efficiency. This ability is very significant and desirable by expanded electronic systems. The solution described is a software model based on a method of address space management called the Component Internal Interface (CII). Establishment of stable link between hardware and software, as a purpose of designed and realized programming environment, is presented. The test-bench implementation and example of OMTF algorithm test is presented.

Gas Electron Multipliers (GEM) are an interesting technology under consideration for the future upgrade of the forward region of the CMS muon system, specifically in the $1.6

The Large Hadron Collider at CERN restarted in 2015 with a 13 TeV centre-of-mass energy. In addition, the instantaneous luminosity is expected to increase significantly in the coming years. In order to maintain the same efficiencies for searches and precision measurements as those achieved in the previous run, the CMS experiment upgraded the Level-1 trigger system. The new system consists of the order of 100 electronics boards connected by approximately 3000 optical links, which must be controlled and monitored coherently through software, with high operational efficiency. These proceedings present the design of the control software for the upgraded Level-1 Trigger, and the experience from using this software to commission and operate the upgraded system.