TREND DAQ proposal Version II

Trigger module (see C) Trigger inhibit Trigger bypass Threshold value Trigger order FPGA Antenna signal Ch1 Antenna signal Ch2 Antenna signal Ch3 Signal analog shapping (see B) Signal sampling (see D) A: GENERAL DAQ SCHEME FOR ONE DETECTION UNIT Antenna signals or 75Ω load (switch driven by FPGA command) Downstream: data Upstream: Commands & parameters Digitized data GPS 1Hz clock (  t =30ns) Time stamping (see E)

B: analog shaping Signal power containt up to 100MHz, BUT relevant infos are only: - position (  time) of signal maximum - enveloppe of the signal (needed to discriminate between signal (prompt transient) and background (longer + several bumps) No need for fast sampling! We can slow down the signal as long as envelope is recorded. Easier (and cheaper) DAQ. Typical signal Typical background

B: analog shaping Exemple: would signal integration preserves relevant info (  signal envelope)? Integrating filter: H(  ) = 1/(1+j(  /  c ) 4 ) With f c =  c /2  =50MHz Test with data for backround & simulated event for signal. Gain Phase (°)

Legend: input signal Output signal Output signal after 100MHZ sampling Output: clean signal (duration~150ns) Output: dirty signal (duration~600ns) Input ( ) : bckgd event (TREND data 1GHz sampling) Input ( ) : simulated EAS signal Integration seems to preserve signal shape. f c =50MHz and 100MSPS seem OK. To be confirmed with systematic study over larger sample (in progress).

B: analog shaping Possible design Filter MHz G~ -10dB Analog card Antenna (channel 1,2 or 3) integrator Power detector is also possible. It should be slow enough (f c ~50MHz at most) to smooth fast variations of signal. LNA ASIC

Trigger module Comparator 1 Ch1 Threshold 1 (updated at ~Hz rate from uplink fiber) OR Comparator 2 Ch2 Th. 2 Comparator 3 Ch3 Th 3 Trigger by-pass Trigger order FPGA AND Trigger inhibit C: TRIGGER

12-bit ADC for each channel (& 3 channels per detection unit) 5µs event size  MSPS. ADCADC Circular Buffer Memory FIFO - Continuous writing to circular memory (depth= 1Kx12-bit) - At trigger signal, transfer of data of interest to FIFO for 3 channels in parallel. Duration~ 15nsx500=7.5µs. Trigger inibited meanwhile. - After transfert, trigger possible again. - FIFO (2Kx12-bit) to un-randomize entry flux (FIFO size ~ 4 events). - Transfert of total event (3x500words serialized + header) through fiber. -Expected data rate: 3x500x12bx1000Hz/8 ~ 2.2 MBy/s ADCADC Circular Buffer Memory FIFO ADCADC Circular Buffer Memory FIFO Interface Eth fiber 1Gb/S FPGA D: SAMPLING

E: Time stamping A time stamp provides absolute time info at given moment (the time of trigger). Baseline solution: – an internal 32bits-100MHz counter re-synchronized each second on the 1Hz signal from a GPS clock. – Expected precision: 30ns. Important notice: this time stamping is initiated by the trigger module. It is totaly independant from the signal sampling and ADC sampling frequency.

Timing precision Time stamping unit (GPS+100MHz counter) Trigger Generator Gate generated at time t i Time stamp t* i t* i –t i [ns] A 30ns resolution means that t* i- t i should be within ±30ns in 66% of the cases realisations

Time stamping Alternative solution: keep track of ADC counts since the beggining of the run and record ADC count for each trigger (same as present TREND DAQ). As all ADC run at the same pace (100MSPS), relative time info between all antennas can be determined if their relative offset at start of run is determined. This can be done by sending a calibrating signal at a specific time seen by all antennas. To perform ADC count: count the number of full circular buffers + position of pointer in present buffer at time of trigger. This method has not been validated yet. This is R&D we want to test. Therefore we also need GPS method (see before).

1234 i-2i-1 i i+1 Channel x of antenna A t (ns) 1234 i-2 i-1 i i+1 Channel y of antenna B 1234 i-2i-1 i i+1 Channel y of antenna B Undetermined relative offset when ADCs start [~ constant over run duration] : ADC count corresponding to trigger instant on this antenna. Calibrating signal seen by all antennas Comparison of ADC count at trigger instant allows determination of relative ADC offsets. run t=0

Possible mechanical design Filter MHz 9 analog independant encapsulated elements to be screwed on a metalic plate in electrical contact with the external box (same as present in TREND-50). Integrator / power detector LNA ASIC G=15dB ADC FIFO Buff FPGA GPS Trigger module Optical interface Filter MHz Integrator / power detector LNA ASIC G=15dB ADC FIFO Buff Filter MHz 3 antenna channels Integrator / power detector LNA ASIC G=-10dB ADC FIFO Buff Digital card ALIM TRANSFO 220V~ to 12V- Box has to be dust & raintight + no elm radiation BUT allowing heat dissipation. Bias Tee BiasTee used to power ASIC LNA on antennas. To be plugged to coax cable going to antenna. 220V~

Timeline t0: agreement/signature of contract (including definition of specifications & delay penalties) t0 + xx months: first prototype Test & validation (NAOC+France) t0 + yy months: production of 35 units Validation & installation on site

Validation of specs Following steps should be checked: Digital part: Check communication with board from DAQ computer (start/stop DAQ, register data, turn on/off triggers/channels, get monitoring data (see TrendElectronicUnitSpecs.pdf for details) Check that there are triggers on transient pulses (20MHz sine wave in burst of ~100ns duration, amplitude down to trigger threshold) Check max trigger rate (up to 1kHz on average, up to ~100kHz for a short period of burst according to the proposed scheme) Check ADCs relative time offsets/drifts. Check time stamping (send a pulse at given periodicity (eg 1 every 0.001s), check that relative delay between triggers is OK (1ms±30ns) Full chain (analog + digital part) Check that there are triggers on transient pulse (100MHz sine wave in burst of ~100ns duration, amplitude down to trigger threshold) Check that envelope is well recorded (test with several sine wave bursts close to each other or a modulated sine wave). Check precison of amplitude measurement. Test with antenna at input in the lab. Test on the field. The more NAOC can be associated to the tests, the better.

Componant list ADC: 12bits+100MSPS Standard performances are OK. Max price: 100€/unit FPGA: CYCLONE V 5CEFA4F23C6N (40€/unit in France) GPS: UBLOX LEA-6T (60€ / unit in France, antenna not included) Optical interface: Ethernet (50€ for one transmitter + receiver pair)

R&D on signal shaping to be done by TREND. Software & user interface to send commands & retrieve data to be done by TREND. One fiber per detection unit: commands sent upstream, data + monitoring downstream. Enough computers to deal with the expected data flux (on average: 2.2MB/s/unit) should be considered. Go for standard solutions: – FPGA programmation language should be VHDL. – Ethernet much prefered over home-made protocols. Distributed clock as a back-up solution.