M. Piccini

Use of FPGA embedded processors for fast cluster reconstruction in the NA62 liquid krypton electromagnetic calorimeter

The goal of the NA62 experiment at the CERN SPS is the measurement of the Branching Ratio of the very rare kaon decay K+??+??? with a 10% accuracy by collecting 100 events in two years of data taking. An efficient photon veto system is needed to reject the K+??+??0 background and a liquid krypton electromagnetic calorimeter will be used for this purpose in the 1-10 mrad angular region. The L0 trigger system for the calorimeter consists of a peak reconstruction algorithm implemented on FPGA by using a mixed parallel architecture based on soft core Altera NIOS II embedded processors together with custom VHDL modules. This solution allows an efficient and flexible reconstruction of the energy-deposition peak. The system will be totally composed of 36 TEL62 boards, 108 mezzanine cards and 215 high-performance FPGAs. We describe the design, current status and the results of the first performance tests.

Development and test results of a digital data transmission system for Liquid Krypton Calorimeter level 0 trigger system for the NA62 experiment at CERN

The NA62 experiment at the European Organization for Nuclear Research (CERN) Super Proton Synchrotron (SPS) aims to measure the Branching Ratio of the very rare kaon decay K+ → π+νν, collecting O (100) events with a 10% background to make a stringent test of the Standard Model. One of the main backgrounds to the proposed measurement is represented by the K+ → π+π0, decay. To suppress this background an efficient photo veto system is foreseen with the Liquid Krypton (LKr) Electromagnetic Calorimeter Level 0 (L0) trigger. The development of a high-performance as well as reliable digital data system addresses this issue providing a mean to have the right bandwidth and efficiency to transmit experimental data to and from the counting room. This paper describes the LKr L0 trigger system, with particular emphasis for what concerns a LVDS digital data link used inside the system. Some aspects relative to the test set-up implementation as well as protocol test used to evaluate and qualify the digital data system are also part of the paper.

The Level-0 calorimetric trigger of the NA62 experiment

The NA62 experiment at the CERN SPS aims at measuring the branching ratio of the very rare kaon decay K+ → π+ ν (expected 10−10) with a 10% background. Since an high-intensity kaon beam is required to collect enough statistics, the Level-0 trigger plays a fundamental role in both the background rejection and in the particle identification. The calorimetric trigger collects data from various calorimeters and it is able to identify clusters of energy deposit and determine their position, fine-time and energy. This paper describes the complete hardware commisioning and the setup of the trigger for the 2015 physics data taking.

Performance and operation of the calorimetric trigger processor of the NA62 experiment at CERN SPS

The NA62 experiment at the CERN SPS aims at measuring the branching ratio of the very rare kaon decay K+ → π+ ν (expected 10−10) with a 10% background. Since an high-intensity kaon beam is required to collect enough statistics, the Level-0 trigger plays a fundamental role in both the background rejection and in the particle identification. The calorimetric trigger collects data from various calorimeters and it is able to identify clusters of energy deposit and determine their position, fine-time and energy. This paper describes the trigger system setup during the 2016 physics data taking. A newly implemented cluster counting algorithm is also presented.

Performance and advantages of a soft-core based parallel architecture for energy peak detection in the calorimeter Level 0 trigger for the NA62 experiment at CERN

The NA62 experiment at CERN SPS has started its data-taking. Its aim is to measure the branching ratio of the ultra-rare decay K+ → π+ν ν . In this context, rejecting the background is a crucial topic. One of the main background to the measurement is represented by the K+ → π+π0 decay. In the 1-8.5 mrad decay region this background is rejected by the calorimetric trigger processor (Cal-L0). In this work we present the performance of a soft-core based parallel architecture built on FPGAs for the energy peak reconstruction as an alternative to an implementation completely founded on VHDL language.

Performance of the NA62 RICH detector

NA62 is the last generation kaon experiment at CERN SPS aiming to study the decay K⁺ _ π⁺νν̅. The goal of the experiment is to measure the decay branching ratio (O(10^-10)) with 10% accuracy, collecting about 100 K⁺ → π⁺νν̅ events in three years of data taking and assuming a 10% signal acceptance. The NA62 detector must be able to reject background events from decay channels with branching ratios up to 10 orders of magnitude higher than the signal and with similar experimental signature. To this purpose, good Particle Identification (PID) and kinematic rejection are required. Precise timing is also needed to correctly associate the π⁺ with the parent K⁺ in a high rate environment. The key element of the PID in NA62 is the Ring Imaging CHerenkov detector (RICH) to identify π and μ in the momentum range between 15 and 35 GeV/c with a muon rejection factor better than 1%; it is also required to measure the pion arrival time with a precision better than 100 ps and the Cherenkov angle with a resolution better than 80 μ rad. Finally, it must provide a fast L0 trigger signal for charged particles. At the beginning of the NA62 pilot run, from mid October to mid December 2014, the RICH detector was completely installed and ready to take data. The installation details and the results on the detector performance will be presented together with preliminary results from the first NA62 physics run in 2015.

Status of the Level 0 Trigger Processor of the NA62 Liquid Krypton Electromagnetic Calorimeter

The NA62 experiment at the CERN SPS aims to measure the Branching Ratio of the ultra-rare decay K^+ rightarrow π^+νbarν, collecting about 100 events in two years of data taking with a signal to background ratio of 10:1. A hermetic photon veto system has been designed to efficiently reject the π0 background, one of the main background sources, and the 20-ton liquid krypton calorimeter is a fundamental component of such system in the angular acceptance region 1-10 mrad. In this paper, we present the design of the Level 0 trigger processor that is able to identify electromagnetic clusters in the calorimeter providing information on time, position and energy reconstruction for each cluster. In particular, it is composed of 36 readout boards (TEL62), organized in a three layer parallel system, 108 mezzanines and 215 high-performance FPGAs. The system has been designed to sustain an instantaneous hit rate of 40 MHz, to process data with a latency of about 100 μs, and to achieve a time resolution of 1.5 ns on the single cluster. Performance and functionality test results of a trigger slice, together with an updated status report of the whole level 0 trigger project, will be presented.