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The integrated low-level trigger and data acquisition (TDAQ) system of the NA62 experiment at CERN is described. The requirements of a large and fast data reduction in a high-rate environment for a medium-scale, distributed ensemble of many different sub-detectors led to the concept of a fully digital integrated system with good scaling capabilities. The NA62 TDAQ system is rather unique in allowing full flexibility on this scale, allowing in principle any information available from the detector to be used for triggering. The design concept, implementation and performances from the first years of running are illustrated., Comment: 32 pages, 23 figures

The measurement of $BR(K^+\to\pi^+\nu\bar{\nu})$ with 10% precision by the NA62 experiment requires extreme background suppression. The Small Angle Calorimeter aims to provide an efficient veto for photons flying at angles down to zero with respect to the kaon flight direction. The initial prototype was upgraded and tested at the Beam Test Facility of the DA$\Phi$NE Linac at Frascati. The energy resolution and the efficiency were measured and are presented., Comment: 5 pages, 7 figures

The fixed target experiment NA62 at CERN aims at measuring the ultra-rare decay K+→π+νν¯, whose branching ratio is of the order of 10−11. The main challenges faced by the experiment to achieve a 10% precision measurement are the required beam intensity and background rejection factor. The differential Cherenkov detector KTAG must be able to tag charged kaons in an unseparated hadron beam with an average particle rate of 750 MHz, of which 45 MHz are kaons, with a time precision of at least 100 ps and an efficiency higher than 95%. The additional pion contamination must be kept lower than 10−4. The RICH has been designed to separate charged pions from muons in the momentum range 15

The GigaTracker is a hybrid silicon pixel detector built for the NA62 experiment aiming at measuring the branching fraction of the ultra-rare kaon decay K+→π+νν¯ at the CERN SPS. The detector has to track particles in a beam with a flux reaching 1.3 MHz/mm2 and provide single-hit timing with 200 ps RMS resolution for a total material budget of less than 0.5% X0 per station. The tracker comprises three 60.8 mm×27 mm stations installed in vacuum (∼10$^{−6}$mbar) and cooled with liquid C6F14 circulating through micro-channels etched inside a few hundred micron thick silicon plates. Each station is composed of a 200 μm thick silicon sensor read out by 2×5 custom 100 μm thick ASICs, called TDCPix. Each chip contains 40×45 asynchronous pixels, 300 μm×300 μm each and is instrumented with 100 ps bin time-to-digital converters. In order to cope with the high rate, the TDCPix is equipped with four 3.2 Gb/s serialisers sending out the data. We will describe the detector and the results from the 2014 and 2015 NA62 runs.

The Ring Imaging Cherenkov detector of the NA62 experiment at the CERN SPS is a key element of particle identification in the NA62 experimental strategy. According to the NA62 requirements, the RICH identifies π + and μ + in the momentum range between 15 and 35 GeV/c with a muon rejection factor of O(10 2 ), measures the arrival time of charged particles with a precision better than 100 ps and is one of the main components of the NA62 trigger system. After the commissioning in 2014–2015, the RICH detector has been successfully operated during the 2016, 2017 and 2018 data taking periods of NA62. The main design aspects and operational characteristics of the NA62 RICH are described and results on its performance, directly measured with data, are presented.

At CERN, the Detector Technologies (DT) group of the Experimental Physics (EP) department is actively investigating a number of innovative solutions for heat management and detector module assembly in HEP experiments. Among these, recent research carried out at EP-DT has focused on the development of microfluidic devices to cool silicon pixel detectors. In this respect, continuous advances in microengineering have opened the door to smaller and more efficient cooling devices capable of handling increasing power densities with a minimum mass penalty. In 2014, the NA62 experiment has pioneered the use of a silicon microfluidic system with single-phase liquid C 6F14 for the thermal management of its GigaTracKer (GTK) pixel detectors. Following the NA62 success, LHCb became the first LHC experiment to adopt a similar solution. The future upgrade of the LHCb Vertex Locator (VELO) will combine multiple silicon plates with embedded microchannels with an evaporative CO2 system to cool fifty-two pixel detector modules dissipating a total of about 2 kW. This paper will present the implementation of this novel approach for the construction and thermal management of the NA62 GTK and LHCb VELO pixel detectors. Future developments such as 3D-printed microfluidics and microchannels embedded on monolithic pixel detectors will also be discussed.

The NA62 experiment aims to measure the B R ( K + → π + ν ν ) with a 10% precision. One of the main backgrounds comes from the decay K + → μ + ν , therefore a highly powerful pion/muon separation is needed. The NA62 RICH, together with the calorimeter system, provides an accurate particle identification which has been essential to obtain the first results of the NA62 K + → π + ν ν analysis, based on 2016 data. Two different algorithms have been exploited which, used in combination, allowed to get a pion reconstruction and identification efficiency of 75%, with a muon suppression factor of about 500, in the momentum range 15–35 GeV/c.

The NA62 experiment at CERN aims to measure the branching ratio of the ultra-rare charged kaon decay K+→π+νν¯ with a 10% accuracy and with a background contamination at the 10% level. Since the branching ratio of this decay is O (10 −10 ), to fulfill such request one of the main backgrounds, the decay K+→μ+ν (BR ~63% ), must be suppressed by a rejection factor of 4×10 −13 (assuming 10% signal acceptance). This can be partially accomplished using a combination of kinematical cuts (8×10 −6 ) and the different power of penetration through matter of pions and muons (10 −5 ). A further 5×10 −3 suppression factor will be provided by a RICH detector, in a momentum range between 15 and 35 GeV/c. The details of the RICH project as well as the results from test runs performed on a RICH prototype of the same length of the final detector will be presented. The current status of the construction and the description of the final readout and trigger electronics will also be reviewed.

Microscope investigations of new-type thin-wall tubes (straws) produced for NA62 drift chambers revealed that they are semitransparent and allow anode wires to be observed under illumination by visible light. In this work it is shown that positions of wires in straws and thus the anode spacing in the drift chambers can be directly determined with a high accuracy (~5–10 µm) using a microscope mounted on a high-precision optical bench. These data are important for decreasing errors during reconstruction of charged particle track coordinates in the drift chambers. The proposed technique is much simpler than the X-ray or radioactive source methods.

The main aim of the NA62 experiment (NA62 Technical Design Report, 〈http://na62.web.cern.ch/NA62/Documents/TD_Full_doc_v1.pdf〉 [1] ) is to study ultra-rare Kaon decays. In order to select rare events over the overwhelming background, central systems with high-performance, high bandwidth, flexibility and configurability are necessary, that minimize dead time while maximizing data collection reliability. The NA62 experiment consists of 12 sub-detector systems and several trigger and control systems, for a total channel count of less than 100,000. The GigaTracKer (GTK) has the largest number of channels (54,000), and the Liquid Krypton (LKr) calorimeter shares with it the largest raw data rate (19 GB/s). The NA62 trigger system works with 3 trigger levels. The first trigger level is based on a hardware central trigger unit, so-called L0 Trigger Processor (L0TP), and Local Trigger Units (LTU), which are all located in the experimental cavern. Other two trigger levels are based on software, and done with a computer farm located on surface. The L0TP receives information from triggering sub-detectors asynchronously via Ethernet; it processes the information, and then transmits a final trigger decision synchronously to each sub-detector through the Trigger and Timing Control (TTC) system. The interface between L0TP and the TTC system, which is used for trigger and clock distribution, is provided by the Local Trigger Unit board (LTU). The LTU can work in two modes: global and stand-alone. In the global mode, the LTU provides an interface between L0TP and TTC system. In the stand-alone mode, the LTU can fully emulate L0TP and so provides an independent way for each sub-detector for testing or calibration purposes. In addition to the emulation functionality, a further functionality is implemented that allows to synchronize the clock of the LTU with the L0TP and the TTC system. For testing and debugging purposes, a Snap Shot Memory (SSM) interface is implemented, that can work both in an input or an output mode. The trigger rates will be permanently monitored by reading counters at regular intervals. This paper describes the overall NA62 trigger system focusing on the setup for the dry and technical runs in 2012.

One of the most challenging detectors of the NA62 experiment is the silicon tracker, called Gigatracker. It consists of three hybrid silicon pixel stations, each one covering an area of 27 mm×60 mm. While the maximum pixel size is fairly large, 300 μ m × 300 μ m the system has to sustain a very high particle rate, 1.5 MHz/mm 2 , which corresponds to 800 MHz for each station. To obtain an efficient tracking with such a high rate the required track timing resolution is 150 ps (rms). Therefore the front-end ASIC should provide for each pixel a 200 ps time measurement capability, thus leading to the requirement of time walk compensation and very compact TDCs. Moreover, Single Event Upset protection has to be implemented in order to protect the digital circuitry. An ASIC prototype has been realized in CMOS 130 nm technology, containing three pixel columns. The chip performs the time walk compensation by a Constant Fraction Discriminator circuit, while the time measurement is performed by a Time to Amplitude Converter based TDC, both of them implemented on each pixel cell. The End of Column circuit containing only digital logic is responsible for the data readout from the pixel cell. The whole chip works with a system clock of 160 MHz and the digital logic is SEU protected by the use of Hamming codes. The detailed architecture of the ASIC prototype and test results are presented.

The goal of the NA62 experiment is to collect about 80 K + → π + ν ν ¯ events with a S/B ratio of ∼ 10 : 1 . The branching ratio (BR) for this decay is ∼ 10 − 10 and can be predicted in the Standard Model with minimal theoretical uncertainties, making it a sensitive probe for new physics. Measurement of this BR is challenging because of the background from dominant channels. To reduce background from K + → π + π 0 decays (BR=21%) to an acceptable level, the π 0 must be detected with an inefficiency of less than 10−8. NA62 will make use of the existing NA48 beam-line and liquid-krypton calorimeter. A new photon veto system consisting of 12 rings placed along the vacuum volume is needed to detect large-angle photons (7–50 mrad) with an inefficiency below 10−4 over the energy interval from a few hundred MeV to 35 GeV. A comprehensive R&D program was carried out in 2007–2008 to compare different detector technologies, including the re-use of lead-glass blocks from the OPAL barrel calorimeter, ultimately demonstrating the feasibility of this approach. In 2009, a complete prototype of one veto ring was constructed, complete with front-end electronics to measure energies through time-over-threshold with a dynamic range of 1000, and an in situ calibration and monitoring system. The prototype was successfully tested with electron and muon beams at the CERN SPS in fall 2009. The status of the project and present preliminary results from the recent tests will be reviewed.

In high energy physics experiment the trigger system is crucial to reduce the quantity of data recorded on tape and the acquisition bandwidth requirements. This is particularly true in rare decays experiments. The NA62 experiment aims at measuring the Branching Ratio of K+ -> π+νν, predicted in the Standard Model (SM) at level of ~ 10 -10. In this paper we describe the idea to use the commercial video card processor (GPU) to construct a fast and effective trigger system, both in hardware and software level. Due to the use of off the shelf technology, in continuous development for other purposes, the architecture described would be easily exported to other experiments, to build a versatile and fully customizable trigger system.

The NA62 experiment at CERN, aimed to measure K + → π + ν ν ¯ branching fraction (O(10−10)), relies on a Neon based RICH detector for π / μ separation, time measurement and level 0 trigger. The experimental requirements for this detector are: a muon contamination in pion samples lower than 5×10−3 in the momentum range 15–35 GeV/c and a time resolution on the charged track better than 100 ps. A prototype of such a detector was built and tested in 2009; it consists of a full length ( ≈ 18 m ) Ne filled vessel equipped with a spherical mirror and 414 PMs on its focal plane, located about 17 m upstream of the mirror. This prototype was tested at CERN SPS on a positive hadron beam, in the required momentum range, to measure the π / μ separation and to confirm the time resolution obtained with a previous prototype; the μ misidentification probability is about 0.7% and the time resolution is better than 100 ps in the whole momentum range.

The NA62 experiment at CERN aims at measuring the ultra-rare kaon decay K+→π+νν¯ with a decay in flight technique. The nature of the experiment puts stringent requirements on the trigger and data acquisition system, which is being developed exploiting in part existing solutions. The design concepts for the system are discussed, the chosen solutions are described, together with some results from the prototype test systems.

The NA62 experiment is designed to measure the very rare kaon decay K + → π + ν ν ¯ at the CERN SPS with a statistical precision of less than 10 % . The Standard Model prediction for the branching ratio is ( 8 ± 1 ) × 10 - 11 . One of the challenging aspects of the experiment is the suppression of the K + → μ + ν μ background at the 10 - 12 level. To satisfy this requirement we need a Ring Imaging Cherenkov Detector able to separate π ± from μ ± in the momentum range between 15 and 35 GeV / c with a muon suppression factor of at least 10 - 2 . We discuss the design and the construction of a RICH detector with a very long focal length ( 17 m ) , neon radiator gas at atmospheric pressure and ∼ 2000 fast photodetectors. With a total time resolution of the order of 100 ps this RICH detector can also be used to measure the arrival time of the pion and provide the experiment's trigger.

In the NA62 experiment at CERN, the intense flux of particles requires a high-performance trigger for the data acquisition system. A Level 0 Trigger Processor (L0TP) was realized, performing the event selection based on trigger primitives coming from sub-detectors and reducing the trigger rate from 10 to 1 MHz. The L0TP is based on a commercial FPGA device and has been implemented in two different solutions. The performance of the two systems are highlighted and compared.

Three possible solutions for a system of large-angle vetoes (LAV) have been analyzed and tested in order to choose the best option for the NA62 experiment, expected to take data in 2011/12 at CERN. The rejection power assured by the veto system, whose goal is mainly to veto photons from the K + → π + π 0 and K + → π + π 0 π 0 decays, is a key-point to collect ∼ 100 events of the K + → π + ν ν ¯ decay ( BR ∼ 10 - 10 ) with a total background (BG) of the order of 10%, thus providing a very stringent test of the Standard Model (SM) and a measurement of the V td element of the Cabibbo–Kobayashi–Maskawa (CKM) matrix. The details of this study and the final decision taken will be reviewed in this paper.

The proposal (CERN no. P326) for a new experiment, NA62, is described. This experiment aims to perform a precise measurement of the very rare kaon decay K + → π + ν ν ¯ branching ratio. About 80 K + → π + ν ν ¯ events with 10% of background are expected to be obtained in two years of data taking. To reconstruct charged pion tracks with high efficiency and high resolution a single magnet spectrometer based on straw tubes, working in vacuum, should be designed and produced. The current status of R&D of this detector and the results of its prototype tests are discussed.

The silicon tracker for the NA62 experiment has to provide both a time resolution of 150 ps rms and a space resolution of about 100 mu m rms. These challenging specifications require the development of a new readout electronics in order to address the problem of measuring the tracks arrival time with such a high channel density. Moreover, the high particle density (up to 1.5 MHz/mm(2) in the center and 0.8-1 GHz in total) requires a high speed measurement and data transmission in order to keep the dead time below 1%. (C) 2009 Elsevier B.V. All rights reserved.