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Timing calibration in NEMO

Timing calibration in NEMO. M. Circella Istituto Nazionale di Fisica Nucleare, Bari on behalf of the NEMO Collaboration. NEMO Telescope layout. 200 m. Tower. 200 m. 1 primary Junction Box 8 secondary Junction Boxes 64 towers 200 m grid pitch 64 PMT on each tower

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Timing calibration in NEMO

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  1. Timing calibration in NEMO M. Circella Istituto Nazionale di Fisica Nucleare, Bari on behalf of the NEMO Collaboration

  2. NEMO Telescope layout 200 m Tower 200 m • 1 primary Junction Box • 8 secondary Junction Boxes • 64 towers • 200 m grid pitch • 64 PMT on each tower • 4096 PMT in total Secondary JB Primary JB 1400 m • Electro-optical cable to shore: • 48 optical fibres • 3 – 4 conductors

  3. 19.44 Mbps SDH STM-1 (155 Mbps) Tower Layout FCM (Floor Control Module) Optical Module DWDM communications (2.5 Gbps) Junction Box DWDM mux

  4. FPGA FCM interface Log. Compr. DOUT ADC 8bit [100MHz] Soft trigger clk Counter FIFO PMT com off1 off2 From FCM To FCM clk@1.2MHz DOUT ADC 8bit [100MHz] clk 432 kbps 19.44 Mbps Vcc Offset & Gain PLLout DSP Full description of the NEMO Front-End electronics in Domenico Lo Presti’s and Carlo Nicolau’s presentations tomorrow (A2.4.1 and A2.4.3) Lock In JTAG Flash 256kX8 Out SCI ADC\DAC 10bit [Slow control] Cal. In 8 Front-end electronics (inside the Optical Modules) F C M Sensors

  5. SDH mapper (Transwitch Fast-3N) E/O/E interface (Finisar FTR-1631) Power Conditioning OM1 OM2 Tower Base OM3 OM4 Full description of the NEMO SDH transport in Fabrizio Ameli’s presentation later (A1.4.9) PCI Bus Proprietary Protocol (Electric) Rx: 19.44 Mbps Tx: 432 kbps Floor Control Module clock FPGA STM-1 Interface TBTI Overhead STM-1 Protocol (optic fibre) 155 Mbps Sinchronous Serial (SPI) DSP Slow Control STM-1 Interface Control Circuits Indipendent Bidirectional Communication between DSP and STM-1 Interface through TOH channels (E1, E2, F1, DCC) PCI Bandwidth: 120 MBps, enough to allow real-time transmission to Host of STM-1 protocol data

  6. STM-1 Payload

  7. SDH STM-1 data frame 270 bytes 9 bytes 261 bytes 9 rows

  8. (DWDM) DATA TRANSPORT in NEMO from tower to shore Floor # 1 1/16 DWDM MUX 1/16 DWDM DEMUX Tower # 1 Floor # 16 Floor # 1 1/16 DWDM DEMUX 1/16 DWDM MUX Tower # 1 from shore to tower Floor # 16 Tower Shore One colour per floor (50 GHz spacing)

  9. Time measurements in NEMO • The signals from the Optical Modules are continuously sampled at 200 MHz (by means of two ‘staggered’ ADC’s) • When a threshold value (remotely programmable through slow control) is met, the over-threshold samples, plus a fixed number of pre-trigger samples, are stored in a FIFO for transmission to shore • The readout at the trigger time of a 16-bit 100 MHz counter is stored together with the sampled signals Synchronization in NEMO The clock signal is recovered offshore (in each Floor Control Module) from the SDH frames received from the onshore station The SDH mapper inside the FCM recovers a low-jitter 19.44 MHz clock (also used to clock out the ‘payload’ data received in the SDH data frames) A 1.215 MHz clock is delivered from the FCM to the Optical Modules This 1.215 MHz clock is fed to a PLL to give rise to the 100 MHz clock used for all front-end operations

  10. Timing calibration in NEMO • Two different problems: • Compare the time measured in the apparatus with UTC time (“absolute” timing calibration) • Determine the offsets in local time measurements (“relative” timing calibration), i.e. the propagation time of commands and clock signals from onshore to offshore Same problem for all neutrino telescopes Same problem for all neutrino telescopes if the digitization and time measurements are performed offshore

  11. I. SDH “echo” calibration II. Optical calibration Time calibration in NEMO (the approach) Floor Control Module Optical Module (& FE electronics) III. Shore station: It will be equipped for the SDH “echo” time measurements and with GPS Tower JB Secondary JB

  12. Power Conditioning OM1 OM2 Tower Base OM3 OM4 PCI Bus The FCM interface to the timing calibration system clock FPGA STM-1 Interface TBTI Overhead DSP Slow Control The FPGA will sinchronously: • Deliver the reset signal to the time counters in the optical modules • Deliver an echo signal to the shore station • Activate the optical calibration system • in response to a shore command

  13. Optical beacons are ineffective for km3-scale detectors! Number of photoelectrons Distance of a PMT from the optical source

  14. Optical calibration system Optical Module diffuser Optical fibre splitter Attenuator Photodiode Optical source (+ time stamp) FCM (Floor Control Module) FCM electronics interface

  15. Timing calibration in NEMO: conclusions and perspectives • The relative timing calibration will be performed by means of a SDH “echo” measurement and an optical calibration system • Interface with the data trasport system under definition • Different choices under study for the optical calibration system

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