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

2. 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, August 2017

3. Proposed Readout Architecture…
ASIC
Front-End Card
FPGA
Front-End
Mezzanine
Card …
ASIC
Front-End Card
FPGA
Front-End
Mezzanine
Card
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, August 2017

4. 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 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, August 2017

5. 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, August 2017

6. 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, August 2017

7. 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, August 2017

8. 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: 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 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, August 2017

9. Efficient Power Conversion
Requirements and constraints
Need to bring 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, August 2017

10. 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, August 2017

11. 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, August 2017

12. TPC back-end PC and Software
Quantity required: 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, August 2017

13. 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, August 2017

14. 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, August 2017

15. 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, August 2017

16. 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, August 2017