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Digital & Analog electronics for an autonomous, deep-sea Gamma Ray Burst Neutrino prototype detector K. Manolopoulos, A. Belias, E. Kappos, C. Markou DEMOKRITOS NATIONAL CENTER FOR SCIENTIFIC RESEARCH Slide 2 GRBNeT Gamma Ray Burst Neutrino Telescope Development, construction and testing of a prototype autonomous detection unit anchored at the sea bed without any cabled connection to the shore able to operate for a prolonged time ( ~1year) A few tens of such arrays separated by 300-400 meters from each other, will be able to cover a volume of ~ 10km 3 in the deep sea provide a sufficiently large observational volume capable of detecting high-energy neutrinos originating from GRBs 2 Slide 3 GRBNeT prototype layout Grey spheres: Optical Modules Orange spheres: data acquisition electronics, acoustic communication, power units Green spheres: Buoyancy 40m 200m 130m Detection Unit 3 Slide 4 4 Optical Modules arranged in a cross shaped frame Optical Module: 13-inch PMT (R8055) housed inside a pressure resistant glass sphere Detects Cherenkov light produced by muons in the deep-sea Each cluster operates autonomously in terms of Power supply data acquisition trigger systems Optical Modules 4 Slide 5 GRBNeT basic characteristics No dependency on cables Cost effective & easy to deploy Can be placed around any active underwater telescope PMTs look towards the horizon where there is maximum sensitivity for UHE neutrinos Use high signal thresholds (> 5 p.e) to reduce data rate and minimize background Deep-sea deployment to reduce atmospheric background Power will be supplied by batteries at ambient pressure! Low power electronics Each floor has its own trigger and DAQ Synchronization between floors through LED beacons. Data stored locally and recovered through an acoustic modem or at recovery time. 5 Slide 6 Deployment Location Several locations near Pylos available at various depths Prototype deployment at 3500m GRBNeT autonomous prototype lines can also be deployed in other KM3NeT sites 6 Slide 7 Block Diagram of the Electronics Container 7 Spartan - 6 FPGA Atomic Clock Multiple Threshold Discriminator Optical Modules Input lines FMC 10MHz Clock PPS Compass Tilt-meter Microcontroller Acoustic Modem PMTs voltage controller Slow Control Unit Electronics Container Slide 8 8 ANALOG ELECTRONICS Slide 9 PMT base To minimize power consumption we developed a new PMT base Cockroft-Walton (CW) voltage multiplier to operate up to 2.5kV HV-controller with ultra low-power microcontrollers Each Optical Module features a HV control unit to drive the CW, producing the desired voltage for the specific PMT (R8055) 9 Slide 10 Gain vs. High Voltage 10 Comparison between PMTs with CW-base and Resistive-base Slide 11 Multiple Threshold Discriminator Each PMT transmits the analog signal to a multiple threshold level discriminator 4 thresholds for this prototype are chosen to cover a large dynamic range of PMT signals Analog signal is compared to a very low, low, medium and a high threshold When a threshold level is crossed the discriminator outputs a digitized pulse Pulse lasts for as long as the analog signal remains above that threshold. The digitized pulses are used as input to the FPGA 11 Slide 12 DIGITAL ELECTRONICS 12 Slide 13 FPGA Design Requirements Detect events of interest, based on PMTs digitized outputs Measure spatial and temporal characteristics of these events (i.e. duration, intensity) Use an atomic clock as an autonomous, free-running reference clock for synchronicity and time-stamping Store the result locally to a permanent data storage Collect and store operational data and data from auxiliary devices 13 Slide 14 Hardware Components FMC XM105 Spartan-6 LX16 Evaluation Kit Chip Scale Atomic Clock 14 Slide 15 FPGA Design Block Diagram 15 Slide 16 Coincidence Logic Unit Searches for PMT signals that coincide within a small time window State machine monitors if at least 2 out of 4 PMTs produce a pulse within a 200ns window (2-fold coincidence) If a 2-fold coincidence is detected Time window expands to 200ns + 100ns At the end of the expanded 300ns window all PMT data are stored 16 Slide 17 Time Over Threshold calculation Use of different clock domains to calculate coarse time and fine time 17 Slide 18 Rate Measurement Unit Detects incoming pulses (monitoring the every threshold level) Counts the number of incoming pulses within a programmable time window (i.e. 1sec) At the end of the time window results are stored to a RAM Permanent storage of the rate measurements is done periodically 18 Slide 19 Writing to SD Card Communication wit SD cards via SPI protocol Current estimate of trigger rates ~ 10Hz Data size of each detected event ~200bytes Worst-case scenario of continuous 10Hz rate => 7.2Mb/hour => ~63Gb/year (regarding the data rates see also K. Pikounis talk) 19 Slide 20 Control Unit Handles synchronization and control signals Responsible for data and command handling Periodically initiate data storage to the SD cards Slow Control Unit Implemented at a separate board that hosts a PIC microcontroller Controls/monitors the PMTs voltages Communicates via I2C with Tiltmeter Compass Communicates with the Acoustic Modem Stores periodically the gathered data to an SD Card 20 Slide 21 FPGA Design Implementation Results Implementation Results Slice Registers Slice LUTsOccupied Slices MUXCYsRAMB16 FPGA Design 3098 (17%) 2039 (22%) 1168 (51%) 672 (15%) 25 (78%) 21 FPGA Utilization Total Power375 mW Quiescent Power93mW Dynamic Power282 mW Power Consumption (Xilinx power analyzer) Slide 22 CSAC Atomic Clock Chip Scale Atomic Clock (Microsemi SA) Worlds smallest, lowest power atomic clock technology Low power consumption (< 125mW) Enables atomic timing accuracy in portable, battery powered applications Provides 10 MHz clk and PPS 22 Simplified CSAC block diagram Slide 23 23 Slide 24 24 Slide 25 Conclusions Developed the DAQ system of the GRBNeT autonomous detection unit Flexible design utilize general purpose FPGA Compartmentalized functionality Can easily be adapted to future changes Project is on-going All aspects of the project are being tested in lab. environment Preparations for the deployment have started Schedule for deployment with HCMR R/V "AEGAEO" is being prepared Stay tuned!!! 25 Slide 26 Thank you for your attention!! 26 Slide 27 BACKUP SLIDES 27 Slide 28 PMT Calibration with the CW-base 28