1. by E. Anassontzis, A. Belias, E. Kappos, K. Manolopoulos, P. Rapidis on behalf of the KM3NeT Collaboration

2. Potential neutrino sources TIPP’14K. Manolopoulos Supernova Remnants Pulsar Wind Nebula Gamma-Ray Burst ? Dark Matter ? ? ? ? ? ? ? ? ? Active Galactic Nuclei Cosmogenic neutrinos Micro Quasars

3. Detection principle TIPP’14K. Manolopoulos Active Galactic Nuclei Neutrino-induced muons in the deep sea Picture from ANTARES up-going neutrino µ Cherenkov Neutrino Telescope 43° water/ rock charge current interactions

4. KM3NeT Artistic Impression TIPP’14K. Manolopoulos ELECTRO-OPTICAL CABLE TO SHORE ~100m ~ 700m 6 Building Blocks (BBs) ~ 6 km 3 1 BB = 115 Detection Units (DU) 1 DU = 18 Digital Optical Modules

5. KM3NeT- Where & When TIPP’14K. Manolopoulos 200 People 40 Institutes 10 Countries  2 BBs in each site ~2km 3  KM3NeT-France: Toulon ( ~ 2500m)  KM3NeT-Italy: Capo Passero ( ~ 3500m)  KM3NeT-Greece: Pylos (depth ~ 4500m)  Common hardware, data handling and operation control  Centrally managed  Nodes for marine science at each site

6. Digital Optical Module (DOM) TIPP’14K. Manolopoulos Upper Hemisphere 12 PMTs Lower Hemisphere 19 PMTs Central Logic Board (CLB) PMT Base: High Voltage Supply Analog Front-End Power- Board

7. Digital Optical Module (DOM) Receives power from external 400V/12V power supply. Uses internal power supply board (DOM-PB) to generate 7 power rails at various voltages as required by its electronic modules, e.g. Central logic (FPGA) board. Photomultiplier (PMT) bases. Optical communications. Instrumentation boards inside the DOM, e.g. Acoustic piezo sensor for the DOM positioning system. Compasses and tiltmeters to monitor the orientation of PMTs. Temperature and humidity sensors. LED nanobeacons for timing calibration. TIPP’14K. Manolopoulos

8. DOM Power Supply Board (DOM-PB) Design considerations Multiple power rails derived from 12V input. High power conversion efficiency desirable. Power up sequencing requirements to adhere to (strictly sequential). Strict form factor constraints imposed by DOM mechanical design. Not easily accessible or serviceable inside the DOM. Attached directly to DOM heat conductor to improve cooling. DOM uses an internal mushroom-shaped aluminium heat conductor to improve heat flow to its environment (sea water). Shielded against EMI and acoustic noise to other DOM modules. Reliability – operating lifetime > 10 years. TIPP’14K. Manolopoulos

9. Design options Pre-production version, to be used only during DOM electronic systems development for power evaluation purposes, with capabilities for Current and voltage sensing of all power rails. I2C communication for data acquisition by FPGA firmware. PC software. Dynamic power profiling tool for DOM electronic modules. Reduced power efficiency due to: Extra ICs (ADCs, buffers, …) Current sensing resistors. Production version. Without the above capabilities, to increase power efficiency. TIPP’14K. Manolopoulos

10. Implementation considerations Use readily available off-the-shelf components (ICs). Modular design for flexibility in implementing future changes in case of component obsolescense or procurement problems. Low cost Component costs 2 power connectors, 1 mixed power/signal connector. Input DC power filter, output ferrite (LC) filters. Switching/linear regulator ICs, magnetics, other ICs PCB costs Use max 4 layers. No blind or buried vias. TIPP14K.MANOLOPOULOS.

11. Power rail specifications with current (power) estimates Step down: 12V → 1.0V2.3A (FPGA board) 12V → 1.8V 0.9A 12V → 2.5V0.9A 12V → 3.3V0.7A (digital) 12V → 3.3V0.3A (analog, PMT bases, low noise/ripple required) 12V → 5.0V0.4A Step up: 12V → 0V.. 30V5mA (programmable via I2C) Power sequencing: Power-up: Low voltages precede higher voltages. Power-down: Not specified. Power-good output asserted when all step-down rails are good. Separate power-good output for the PMT rail required. Step-up rail: no need for power-good. Activated when 5.0V rail is good. TIPP14K.MANOLOPOULOS.

12. Implementation decisions For efficiency, use switching regulators due to high step-down ratio. For reduced noise/ripple and higher efficiency on the PMT rail: Use linear regulator preceded by step-down 12V → 3.8V to reduce linear dropout. Avoid using power sequencer IC: Use the ENABLE input and POWER_GOOD outputs of switching regulators in a daisy-chain (i.e. domino-like) configuration, where each regulator is enabled by the power good output of the previous (lower) rail. TIPP14K.MANOLOPOULOS.

13. TIPP14K.MANOLOPOULOS. Voltage Rising Time

14. Implementation options for step- down switching regulators Regulator IC with external magnetics. Flexibility in selecting switching frequency and component values. Longer development for tests & qualification of each switcher design. Less flexibility in modifying the Power Board design. Modular point-of load (POL) switching regulator. Regulator IC with magnetics supplied as a single module. Encapsulated modules (expensive, but EMC qualified). Module on mini PCB (low cost). Speeds up development. Flexibility in upgrading and modifying the Power Board design. Guaranteed electrical and EMC specifications. Optimized PCB design by manufacturer, own GND plane. Widely available by several manufacturers, low cost. No flexibility in selecting switching frequency. TIPP14K.MANOLOPOULOS.

15. DOM Vout Settings TIPP14K.MANOLOPOULOS.

16. Power Board Overview TIPP14K.MANOLOPOULOS.

17. Conclusions Power efficiency of pre-production version approx. 80%. Estimated power efficiency of production version approx. 85%. Further work Use power profiling capability of pre-production version to provide precise figures on current consumption of all DOM electronic modules. Optimise power efficiency by replacing POL modular converters with bespoke switching regulators with own magnetics to achieve at least 90% efficiency on each rail. TIPP14K.MANOLOPOULOS.

18. Thank you for your attention. Questions? TIPP14K.MANOLOPOULOS.

19. Backup slides TIPP’14K.MANOLOPOULOS.