1. M. Circella and the NEMO Coll., Timing Calibration in NEMO VLV T workshop, Amsterdam, October 2003 Timing calibration in NEMO M. Circella Istituto Nazionale di Fisica Nucleare, Bari on behalf of the NEMO Collaboration

2. M. Circella and the NEMO Coll., Timing Calibration in NEMO VLV T workshop, Amsterdam, October 2003 NEMO Telescope layout Secondary JB 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 Electro-optical cable to shore: 48 optical fibres 3 – 4 conductors Primary JB Tower 200 m 1400 m

3. M. Circella and the NEMO Coll., Timing Calibration in NEMO VLV T workshop, Amsterdam, October 2003 Tower Layout Junction Box FCM (Floor Control Module) Optical Module 19.44 Mbps SDH STM-1 (155 Mbps) DWDM communications (2.5 Gbps) DWDM mux

4. M. Circella and the NEMO Coll., Timing Calibration in NEMO VLV T workshop, Amsterdam, October 2003 Front-end electronics (inside the Optical Modules) PMT ADC 8bit [100MHz] DOUT clk ADC 8bit [100MHz] DOUT clk Log. Compr. off1off2 com Sensors Out In ADC\DAC 10bit [Slow control] Offset & Gain Cal. 8 F C M FCM interface 19.44 Mbps 432 kbps clk@1.2MHz Vcc DSP Flash 256kX8 JTAG SCI Lock In PLLout FPGA Soft trigger FIFO To FCM Counter From FCM 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)

5. M. Circella and the NEMO Coll., Timing Calibration in NEMO VLV T workshop, Amsterdam, October 2003 Floor Control Module Tower Base DSP OM 1 OM 2 OM 3 OM 4 Slow Control FPGA STM-1 Interface PCI Bus Power Conditioning Sinchronous Serial (SPI) STM-1 Protocol (optic fibre) 155 Mbps 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 Proprietary Protocol (Electric) Rx: 19.44 Mbps Tx: 432 kbps clock TBTI Overhead Full description of the NEMO SDH transport in Fabrizio Ameli’s presentation later (A1.4.9) E/O/E interface (Finisar FTR-1631) SDH mapper (Transwitch Fast-3N)

6. M. Circella and the NEMO Coll., Timing Calibration in NEMO VLV T workshop, Amsterdam, October 2003 STM-1 Payload

7. M. Circella and the NEMO Coll., Timing Calibration in NEMO VLV T workshop, Amsterdam, October 2003 270 bytes 9 bytes 261 bytes 9 rows SDH STM-1 data frame

8. M. Circella and the NEMO Coll., Timing Calibration in NEMO VLV T workshop, Amsterdam, October 2003 Tower # 1 Floor # 1 Floor # 16 Tower # 1 Floor # 1 Floor # 16 ShoreTower from tower to shore from shore to tower (DWDM) DATA TRANSPORT in NEMO 1/16 DWDM DEMUX 1/16 DWDM MUX 1/16 DWDM MUX 1/16 DWDM DEMUX One colour per floor (50 GHz spacing)

9. M. Circella and the NEMO Coll., Timing Calibration in NEMO VLV T workshop, Amsterdam, October 2003 1.The signals from the Optical Modules are continuously sampled at 200 MHz (by means of two ‘staggered’ ADC’s) 2. 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 3.The readout at the trigger time of a 16-bit 100 MHz counter is stored together with the sampled signals Time measurements in NEMO 1.The clock signal is recovered offshore (in each Floor Control Module) from the SDH frames received from the onshore station 2.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) 3.A 1.215 MHz clock is delivered from the FCM to the Optical Modules 4.This 1.215 MHz clock is fed to a PLL to give rise to the 100 MHz clock used for all front-end operations Synchronization in NEMO

10. M. Circella and the NEMO Coll., Timing Calibration in NEMO VLV T workshop, Amsterdam, October 2003 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 Timing calibration in NEMO Same problem for all neutrino telescopes Same problem for all neutrino telescopes if the digitization and time measurements are performed offshore

11. M. Circella and the NEMO Coll., Timing Calibration in NEMO VLV T workshop, Amsterdam, October 2003 Optical Module (& FE electronics) Floor Control Module Tower JB Time calibration in NEMO (the approach) I. SDH “echo” calibration III. Shore station: It will be equipped for the SDH “echo” time measurements and with GPS II. Optical calibration Secondary JB

12. M. Circella and the NEMO Coll., Timing Calibration in NEMO VLV T workshop, Amsterdam, October 2003 The FCM interface to the timing calibration system Tower Base DSP OM 1 OM 2 OM 3 OM 4 Slow Control FPGA STM-1 Interface PCI Bus Power Conditioning clock TBTI Overhead 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. M. Circella and the NEMO Coll., Timing Calibration in NEMO VLV T workshop, Amsterdam, October 2003 Optical beacons are ineffective for km 3 -scale detectors! Distance of a PMT from the optical source Number of photoelectrons

14. M. Circella and the NEMO Coll., Timing Calibration in NEMO VLV T workshop, Amsterdam, October 2003 Optical calibration system (+ time stamp) FCM electronics interface splitter Optical source Optical fibre FCM (Floor Control Module) Attenuator Photodiode Optical Module diffuser

15. M. Circella and the NEMO Coll., Timing Calibration in NEMO VLV T workshop, Amsterdam, October 2003 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