Challenges and Key Concepts in Building and Running a Large-Scale Instrumental Array

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The GRAND project involves building and running a massive array of detectors over a vast area, with a focus on simplicity and cost-effectiveness. Key components include signal reconstruction, background discrimination, broadband antennas, readout electronics, and data transfer considerations. The budget for each detection unit must remain below a certain power consumption and cost threshold. Various technical solutions and strategies are discussed to address the unique challenges of this ambitious project.

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GRAND instrumental challenges Building & running a 90 000 units array over 60 000km ?

GRAND detector key concepts Go large, go basic! Use as basic detection units as possible: Easier to deploy Easier to maintain Lower power consomption Less data to transfer Cheaper Some very preliminar ideas

What infos do we really need? Signal reconstruction with trig time (direction) & E-field amplitude (energy) Background discrimination with trigger pattern & polarization. trig time & waveforms (x,y,z) max amplitudes (or integral). (ie full waveform & frequency spectrum not relevant (?)) IF so, only necessary information would be antenna Only 4 words per detection unit!

GRAND antennas Broadband & sensitive active antennas (a la SUBATECH) Signal expected around horizon: limit lobe to few (~20?) degrees in zenith to improve signal/noise ratio & optimize threshold.

Readout electronics Selection/detection of EAS pulses (Sharp) filter Pulse shape discriminator (short/long) Trigger system Amplitude detector / Integrator (basic) ADC+FPGA GPS but how to reach ~ns time resolution? GHz clock synchronized with GPS? Beacon a la LOPES/AERA? (F Shroeder PhD thesis) Analog treatment

Data transfer Key is data volume. IF 4 words x 12bits x 100Hz trig rate = 600 By/antenna/s No need for real time transfert. Data buffering possible to limit communications. Full array: 54 GBy/s (but offline fast coinc search may reduce data volume significantly) Technical solution? wireless UART? (see D. Gerard talk) Data flux/Bandwidth? 1 concentrator for 500 units ~200 concentrators in total. Data handeling: - saved @ concentrator - sent to central DAQ by fiber - GSM: today 80$/GBy in China to be discussed?

Budget for the detection unit Element Power consumption Price Antenna - 10$ LNA ~500mW <10$ x3 Filter - <20$ x3 Signal detection (shape selection & trigger) negligeable ~10$x3 ADC+FPGA ~150mW ~50$ GPS ~100mW <50$ Com. ~100mW 10$ or ? Power generator: solar pannel (or wind mill?) - ~50$ Mechanics - 100$ Cables, connectors & PCB - 100$ Total ~ 1W 490$ Should remain below 2W & ~500$/unit.