Readout Electronics for T2K-II TPCs: Towards a Technical Proposal Document D. Calvet, Irfu, CEA Saclay, 91191 Gif sur Yvette Cedex, FRANCE

Current Baseline Design outline New TPC A CurrentTPC N°1 CurrentTPC N°1 CurrentTPC N°1 New TPC A Current system: 3 TPCs; 12 bulk Micromegas per end-plate; MM size: ~35 cm × ~35 cm 36 × 48 pads; Total: 72 detector modules 121 K-channels CurrentTPC N°1 CurrentTPC N°2 CurrentTPC N°3 New TPC B New TPC B magnet M0 Resistive Micromegas 36 (h) × 32 (v) pads M2 M4 M6 ~80 cm ~34 cm M1 M3 M5 M7 ~180 cm ~41 cm Structure 2 TPCs, each composed of 2 end-plates supporting 8 Micromegas modules segmented in 36 x 32 pads Total of 32 detector modules; 36 K-channels (36.864) 4th Workshop on Neutrino Near Detectors based on gas TPCs | Geneva, 01-02 August 2017

Proposed Readout Architecture … ASIC Front-End Card FPGA Front-End Mezzanine Card … ASIC Front-End Card FPGA Front-End Mezzanine Card 36.864 detector pads 512 ASICs (72 channels) … 64 FECs (with 8 ASICs each) 32 FEMs (each drives 2 FECs) Inside magnet Detector module Optical fiber Outside magnet FPGA … Trigger and Data Concentrator Module 2 TDCMs (each controls 16 FEMs, i.e. 1 TPC) RJ45 cable Private Ethernet Slave Clock Module PC for TPC Control & DAQ 1 PC (controls 2 TDCMs) nd280 network Global Event Builder, Run Control, Condition Database, Event Display, Mass Storage Structure Identical to that of T2K phase 1, with the adaptations to match segmentation of new detector 4th Workshop on Neutrino Near Detectors based on gas TPCs | Geneva, 01-02 August 2017

front-end ASIC ?? AGET – DREAM - ASTRE Various pros and cons (e.g. these are 64-channels chips while AFTER has 72-channels), none of these chips are in stock: would need ~50 k€ for production, time (>6 months), manpower for test, etc. → Not retained New chip or improved AFTER-AGET-ASTRE or DREAM What to improve for T2K? Saturation? Development cycle >1.5 year. Budget required: ~50 k€ for prototyping + ~50 k€ for production. Manpower: 2-3 FTE total; some technical risks. → Idea not pursued (at least at Irfu) AFTER Proven solution. Current stock of tested, encapsulated chips: ~700 (need 512 + spares for 36-K channels) Plastic package obsolete: ceramic package OK (but costs ~180 € each); potential solution found to make an encapsulation with the same footprint Pros: low risk, ready now, no manpower, no extra cost. Cons: limited stock, end of life product → AFTER is proposed as a baseline choice. If channel count increased beyond current stock: produce new wafers and encapsulate in ceramic package or alternative packaging solution 4th Workshop on Neutrino Near Detectors based on gas TPCs | Geneva, 01-02 August 2017

Front-end card Baseline proposal ~20 cm max. Quantity for 36 K channels + 25% spares: 80 Estimated cost: 80*500 = 40 k€ AFTER 8-channel ADC Ctrl & Clock Fanout Fanin Power Regulator ~23 cm (6U) Each detector modules requires two of these 576-channel FECs AD9637 or equivalent 12.5 MHz clocking allows SCA conversion in ~3.3 ms, i.e. max. 33 event/second acquisition rate at 10% dead-time FEM connector Power input connector (separate or merged with FEM connector) LDOs make clean 3.3V and clean 1.8V (also 2.5V if needed) from 4-5V input Supply current: ~2 A Bard dissipation: 10 W 144 pad signal connector Design principles Aim to mount card parallel to the detector plane: possible if protection circuits not required (resistive MM) 8 AFTER per card + octal ADC (could also be put on the FEM side), connectors, clock/control fan in/out → Alternatively a design with four 288-channel FEC perpendicular to the detector module plane is possible (similar to the present system except it has six FECs per detector module 576-channel FEC 4th Workshop on Neutrino Near Detectors based on gas TPCs | Geneva, 01-02 August 2017

Connectors: an important choice! Detector to FEC connector (T2K phase 1) ERNI 1.27 mm pitch 80 pin connector Straight and right angled version available Found fragile, risk of being pulled out of PCB Easy to bend and break pins on male side (FEC) Need precise alignment mechanics FEC to FEM connector (T2K phase 1) Hirose 1.27 mm 80 pin through hole connector Robust and reliable Straight and right angled version available Need good alignment for insertion – maybe still mechanical stress Right angle socket (T2K Phase 1 FEM uses straight version) Straight female header (as used on T2K Phase 1 Micromegas) Straight male socket (T2K Phase 1 FEC use right-angle version) Straight plug (T2K Phase 1 FEC uses right angle version) → Not recommended → Would be OK but 80 contacts may not be enough 4th Workshop on Neutrino Near Detectors based on gas TPCs | Geneva, 01-02 August 2017

Ideas on Connectors for T2K Phase II Samtec 160 pin 0.8 mm pitch dual row Used in Minos (nuclear physics) experiment for Micromegas to FEC cable connection Rather robust although lock pin may brake Floating contact dual row connectors Models from Hirose and Samtec Allows ± 0.5 mm misalignment in X and Y 0.5 mm pitch (this is small…) Up to 140 contacts Male header – card edge mount version shown → A possible choice Samtec one piece-array 300-pin version used on an ILC TPC prototype Very low stacking height, difficult to get reliable contacts (excellent planarity of PCB required) → Not recommended → Seems nice, but personally no experience → Many different possibilities. Need careful analysis before making final choices 4th Workshop on Neutrino Near Detectors based on gas TPCs | Geneva, 01-02 August 2017

Front-end Mezzanine card Baseline proposal 1152-channel readout FEM Quantity for 36 K channels + 25% spares: 40 Estimated cost: 40*500 = 20 k€ FPGA Optical TX/RX SRAM DC/DC Converter & LDOs Event buffer requires memory external to FPGA Each detector modules requires one FEM Single optical fiber carries clock, data, control and connects to back-end electronics Local power generation: 3.3V (optical TX/RX, interface to AFTER chips) 2.5 V (SRAM), 1.0V (FPGA core), etc. Core of FEM logic in FPGA logic, e.g. Xilinx Artix 7 family or newer FEM block Power input connector Voltage: 12, 24 maybe 48 V? Required Power per module: 20-25 W Power block Magnetic field tolerant (0.2 T) DC/DC converter. Output: 4 V 5 A Input: e.g. 24 V 1.2 A Design principles Two blocks: FEM and Power – may be put on same board or could be split into two separate cards FEM drives 2 FECs, i.e. 1152-channels total. Most functions in FPGA logic (no processor) + optical fiber No separate slow control network like CANbus in T2K phase 1 (simpler, cheaper) DC-DC converters may be used to bring power efficiently but magnetic field tolerance is a constraint 4th Workshop on Neutrino Near Detectors based on gas TPCs | Geneva, 01-02 August 2017

Efficient Power Conversion Requirements and constraints Need to bring 20-25 W of electrical power to each detector module, 4 V × 5 A DC-DC converters provide efficient conversion (>75-85% efficiency) with input at 12 V, 24 V up to 48 V But need to be tolerant to magnetic field 0.2 T and non perturbative for this magnetic field Up to 15V in 5A out DC-DC with external inductor Up to 20V in 3A out DC-DC with embedded inductor CERN FEASTMP DC-DC Up to 12V in 10W power Air inductor. Tolerant to 4 T magnetic field and 200 Mrad Design options Commercial part with embedded inductor. De-rate to account for 0.2 T? Add custom magnetic field shield? Commercial chip with external air core inductor (does not saturate, but low inductance) CERN made device (also rad-tolerant which is not needed in our case) → Some R&D / component testing needed for magnetic field compliant efficient power conversion Dissipative solution – like currently used in T2K is still a proven fallback solution 4th Workshop on Neutrino Near Detectors based on gas TPCs | Geneva, 01-02 August 2017

Detector Module Front-end electronics Shield Heat Spreader and Water Cooling Loop Water in Water out 1152-channel Resistive Micromegas Detector AFTER 8-channel ADC Ctrl & Clock Fanout Fanin Power Regulator AFTER 8-channel ADC Ctrl & Clock Fanout Fanin Power Regulator FPGA Optical TX/RX SRAM DC/DC Converter & LDOs Fiber to Back-end GND 12-48 V Structure One 1152-channel Micromegas plane + two 576-channel FEC + one FEM + heat sink + water cooling pipe → The complete system is the duplication of 32 of these modular blocks 4th Workshop on Neutrino Near Detectors based on gas TPCs | Geneva, 01-02 August 2017

Back-end electronics: Trigger and Data concentrator Module Commercial System-On-Module Mercury ZX1 (Xilinx Zynq 7045) JTAG LEDs RESET PCI Express Gigabit Ethernet SFP General purpose SFPs RJ45 Gigabit Ethernet Connectors for ZX1 FPGA Module FMC connector for Physical Layer Mezzanine #0 Debug Connector RJ45 for Master TDCM (or T2K SCM) RJ45 for Slave TDCM TTL Input Outputs MicroSD Flash Card microUSB (RS232 Console) 12V Power Input NIM Inputs NIM Outputs 16-optical ports SFP Mezzanine card (second mezzanine at bottom optional) Concept Re-use hardware, firmware and large parts of software of TDCM under development for PandaX-III exp. → Prototype board under test; minor adaptations needed for T2K-II (changes anticipated at design) 4th Workshop on Neutrino Near Detectors based on gas TPCs | Geneva, 01-02 August 2017

TPC back-end PC and Software Quantity required: 1 + 1 spare Estimated cost: 8 k€ TDCM A FEM x 16 FEC x 32 TPC readout configuration, data acquisition and system monitoring Global event builder Gbe nd280 network Gbe MIDAS runtime database, slow control database TDCM B FEM x 16 FEC x 32 Gbe Concept Entirely based on commercial hardware On-line software to bridge new TPC readout system to current MIDAS based DAQ → Could be based on earlier development made at Irfu for other experiments 4th Workshop on Neutrino Near Detectors based on gas TPCs | Geneva, 01-02 August 2017

detector production test bench Purpose & tools Test all the detectors of the new TPC Robot arm to move radioactive source and scan detector Gas box, HV, LV, readout electronics for 1module and small DAQ cooperating with robot arm Test bench for production of detectors T2K phase 1 (IFAE/CERN/IRFU) Proposed strategy Probably difficult to re-use or adapt system used 10 years ago (obsolete, dismantled?) Mostly new system; could be based on T2K-II electronics (but need ~1.5 year for development) or use some other hardware, e.g. 4 Harpo readout card (4 AFTER, 256 channels) + PandaX TDCM → Warsaw group requested funding for this project and obtained it! 4th Workshop on Neutrino Near Detectors based on gas TPCs | Geneva, 01-02 August 2017

T2K-II TPC readout Electronics blocks Front-end ASIC (design), production, test Front-End Card design, production, test Front-End Mezz. design, production, test Front-End Mezz. firmware Front-end ASIC Prod. test-bench Front-end card Prod. test-bench Front-end mezz. Prod. test-bench on-detector off-detector Back-end Board design, production, test Embedded Firmware & Software DAQ hardware & software Power supplies Cabling, … Detector test & calib. Test-bench Mechanics, Cooling Services and specific functions Project structure Various building blocks; mostly electronic hardware and software, but also mechanical components Interface to detector, cooling, system, etc. 4th Workshop on Neutrino Near Detectors based on gas TPCs | Geneva, 01-02 August 2017

Services and specific functions Possible work Sharing Front-End Card design, production, test Front-End Mezz. design, production, test Front-End Mezz. firmware Supply AFTER chips Front-end card Prod. test-bench Front-end mezz. Prod. test-bench on-detector off-detector Back-end Board design, production, test Embedded Firmware & Software DAQ hardware & software Power supplies Cabling, … Detector test & calib. Test-bench Mechanics, Cooling Services and specific functions Irfu – CEA Saclay Lpnhe? or IFAE? Warsaw Shared and others Collaborative view Tentative plan. Not final commitment from all partners 4th Workshop on Neutrino Near Detectors based on gas TPCs | Geneva, 01-02 August 2017

Summary and Next steps Before design: confirm hypothesis Need to validate detector technology option (Resistive Micromegas) Need to confirm detector segmentation (1152 channels), approximate size, and number of modules (32) → Proposed architecture very sensitive to some of these assumptions (e.g. FEC size increase and card orientation change if protection circuits are needed, limited stock of AFTER chips, etc) Pre-studies and starting design Back-end development, FEM firmware, DAQ software Connector selection, solution for efficient power conversion Component choices, partial board schematics, excluding layout Detector testbench – keeping some flexibility Collaborative Technical proposal document Consolidation of work sharing plan 4th Workshop on Neutrino Near Detectors based on gas TPCs | Geneva, 01-02 August 2017