na62 straw detector read-out system

Peter LICHARD CERN (for NA62) 1

NA62 Straw detector read-out system• NA62 layout• Straw detector• Requirements for

straw detector electronics

• Readout electronics• frontend• backend

• integration in DAQ • Plans


Straw detector is Pion Spectrometer

Tracking Momentum 2 chambers before magnet 2 chambers after magnet

Recently VETO function Eventually can contribute

to trigger Straw detector operates

in vacuum (blue tube) Low mass , no influence on

observed particles


Straw detector Straw construction

Tube 2.1 meter * 9.8mm 36 m thin PET foils PET =

polyethylene terephthalate coated on the inside with 0.05 m of

Cu and 0.02 m of Au The anode wire (Ø=30 m) is gold-

plated tungsten Straw function

Proportional (drift) chamber Measure particle distance from wire by

drift time Operates in vacuum 1 bar working gas

Straw electrical properties Propagation time full length ~7ns Resistivity of anode 50 Ohm Resistivity of cathode 70 Ohm Metal few atomic layers, electrical

properties determined by surface effects, no skin effect

Straw is very lossy transmission line 50 % of signal from far end

Impedance frequency dependent 1000 Ohms up to 1MHz, 330 Ohm at 20 MHz


Basic readout unit of 16 straws Common electronics control, gas, LV,

HV, signal return, etc 8 straws from 2 layers

4 layers of straws form a ‘view’ 480 straws if all installed 30(15*2) groups of 16(8*2) straws Hole in the middle for beam

View is a system readout unit Data Control Services, DCS Grounding, shielding, ‘earth’

4 views form a ’chamber’ X,Y,U,V 4*480 = 1920 straws

4 chambers 2 before magnet, 2 after In total 1920*4 = 7680 straws (but hole

for the beam)

Straw detector


• Falling edge has the same time for all straws on track.

• Rising edge gives the arrival time of the first cluster

• The closer is the track to the wall, the bigger is the signal (clusters closer)

• Don’t want to see clusters => shaping must be chosen in relation to gas properties

• Tracks from drift time measurement.

Straw function


NA62 Straw tracker electronics

Requirements on straw tracker from electronics point of view• Good quality data (drift time)

• 130 um resolution for single straw• Efficiency -> 100%• This is required

• For all distances from the wire • All along the length of straw

• Low noise• Low crosstalk• efficiency and resolution versus rate

• Ion tail cancellation • Integration in global DAQ and TTC• Reliable and stable operation with tools for monitoring

• Readout chain• ‘classical’ for time measurement• Frontend

• PA+SH+BLR+COMP• CARIOCA chip as a baseline (LHCb)• Other possibilities under study (including discrete electronics)

• Backend• TDC + storage and event management• Frontend control, online monitoring


NA62 straw tracker electronics Required spatial resolution 130 um Needed TDC resolution

‘fast’ gas Ar/CO2 (70:30), muon test beam On X is bin (not resolution) Blue, unknown R-T dependence Red, known R-T dependence

Tools needed in DAQ (on/off line)

Threshold scans Threshold control must be integrated in DAQ Need control for each straw I2C interface per group of 16 straws

2 lines single, 3 lines differential Test pulse scans

Test pulse control and timing in DAQ Separate even and odd straws Need to control also amplitude? NOT calibration

Noise scans Clock delay tuning for detector timing Delay scans

Using test pulses with fine time tuning From data

Distributions of Rising edges Falling edges Pulse width

Hit maps Noise maps

Online R-T dependence would be useful


NA62 straw tracker readout

Current choice for NA62 DAQ does not provide control flow to the detector Only TEL1 (readout) from LHCB was selected but not the module for detector

control There are 3 options considered for straw tracker DAQ electronics (original

consideration)1. Use TELL1 boards + TDC mezzanine Most probably this option requires design and production of extra board for detector control and power distribution. It is assumed here, that the monitoring of the detector is done in DAQ. If it is not the case, the extra board could in small incremental cost include this feature. Test beam and lab small DAQ would try to adapt and profit from the NA62 DAQ development. Must prove connectivity with bulky cables.

2. Use TELL1 + custom mezzanine TDC would be designed with resources inside mezzanine FPGA. Detector control (and power supply, if possible) would be integrated as well. This option still requires bulky cables entering mezzanine, this must be proved possible. Otherwise we would need to reduce the number of straws per TELL1.

3. Design custom board. (baseline)Common NA62 functionalities would be copied (if possible) from current TELL1 design. This involves both TTC and data storage and manipulation. No mezzanine needed as everything is integrated in custom logic.

After considering all practical implications we have chosen 4-th option. We use TEL62 for DAQ and use Straw Readout Board (SRB) for control and monitoring



NA62 straw tracker FrontEnd electronics

• Front end PCB Gas tight PCB using blind vias (bottom faces working gas) thick PCB to ensure mechanical stability High voltage connection integrated on the board + HV filter gas feedthrough numerous configurable GND connections to try different grounding

scheme with detector


NA62 straw tracker FrontEnd electronics Front end board functionality

Two CARIOCA chips (16 straws) for signal processing

12-bit DAC with I2C control for threshold setting

LVDS buffers for outputs (to avoid current imbalances to feed-back to frontend)

Even and odd test pulse buffers Power ~8V/0.12A HV filter and connector

• Front end connectivity Data to DAQ on 16 differential

(LVDS) lines for group of 16 straws Control from DAQ on 5 differential

lines (I2C, TP) Power 8V DCS – temperature sensors and

power sensing lines changing connectors for HONDA

VHDCI, 68 pins


NA62 straw tracker electronics TDC at backend

• Transmission for required length >= 10meters would mean to include active cable equalizer for every line

• 10 meters AWG28 TWP can cause few ns error

• TDC must be put directly on the detector

• Problems• Cables

• heavy and rigid, not easy to handle

• Always perpendicularly connected otherwise EMC compromised

• Crosstalk

FrontEnd electronics with RJ45 connector


Use smaller cable to circumvent mechanical problems standard ethernet cableSerial I/O interfacesFPGA contains TDC, derandomizer, serial links, tools for scans and controlUsing high speed serial links can also help with crosstalk as CARIOCA has a bandwidth of ~20 MHzData flow from 1 FE board

30 bits BX + 3(4) bits fine time + r/f edge + 4 bits straw ID + 1 bit control = 40 bits8B10B coding~800 MBits/s possible in CYCLONEIII, aim for ~160 MBits/sCategory 5e ethernet cable (shielded), 5 metersAverage rate 33kHz

Need 42 MBits/s1 link 160 Mbits/s sufficient

Max rate 500kHz on some strawsNeed 320 Mbits/s2 links 160 MBits/s (using spare output), can also increase the speed if needed

Derandomizer on TDC chip to prevent data loss

FrontEnd electronics with RJ45 connector


Tested now with ‘module-0’ Serial links 400 Mbits/s

1 control 1 control read-back 1 data 1 clock

The first impression from noise scans on- and off-detector seems to be very good

16 TDC channels with 0.78ns resolution in low cost CYCLONEIII (20Euro) ‘0’ integral non-linearity 70 ps differential non-linearity

caused by signal routing 1 pulse (rising+falling edge) in

12ns Minimum CARIOCA pulse >> 12ns

Full qualification needed before going for full production


NA62 straw tracker BackEnd electronics Control

SOB (start of burst) for counters reset and enabling TDC measurement EOB (end of burst) for disabling TDC Fine clock delay for detector TOF tuning Threshold setting for each straw Even/odd test pulses Tools for scans and monitoring

Event management and online monitoring ‘triggerless’ system for straw, everything buffered till higher level trigger decision Data rate

Max rate per straw 0.5MHz Mean rate 33kHz Need to store 32 bit clock ID from SPS START_OF_BURST + 8 bit ‘fine’ time + rising/falling edge +

straw ID 9 bits 33kHz * ~50 bits = 1.65Mbit/straw; 740Mbits/view

Desired functionality split to 2 boards Straw Readout Board (SRB)

Receives precise clock and TTC signals from SPS (SOB, EOB) Frontend control Online monitoring Serving 15 covers; ½ a view Sends data to TELL62 over 1 optical fiber (~400 Mbits/s) Can generate flow-control signals (choke, error)

TELL62 Developed for LHCB, adapted for NA62 (TEL62) Event building Event management Receives full NA62 TTC control


NA62 straw tracker readout board (SRB)

TTC interface for precise clock and commands Flow control (choke, error) if needed Serving 15 FE boards 9U VME board with control and monitoring

through VME bus Event pre-processing Data to TEL62 sent via optical link Eventual trigger L0 sent via optical link 2 needed per view 8 per station

If data flow from straws close to the beam is too high we can increase number of SRBs to 12

32 (48) needed for detector Scaled-down version in 6U VME now in use

FPGA

FPGA

VME

TRIG+DATA

TTC

TEL62 for straw readout

Mezzanine for TEL62 Need to design, produce and test a mezzanine

with 12 high speed serial links (12 SRBs sending data to TEL62)

Commercial solution with standard chips tested

2.4Gbit link using ethernet cable tested 1.2Gbit link needed now

Necessary to use shielded cable 10 meters with better then 10**13 BERR

Firmware Mezzanine data management and handling TEL62 FPGA

Event building and management Not easy with bad trailing edges Include same hits in different events?

Flow control Need 5

4 pieces, 1 for each chamber 1 spare



NA62 straw tracker data flow1 chamber contains 2 modules

1 module contains 2 views

1 view is a smallest readout system

30 FE boards for 1 view (2 groups of 15 boards)

2 StrawReadout Boards

2 fibers TEL62Serving 2 chambers(2x4 views)

Physical layout

Racks Each chamber has got 1 rack Should be less then 10 meters from the chamber due to

cables 1 VME 9U crate for SRBs 2 MPOD crates

1 needed at the moment Spare place for 1 more depending on frontend electronics

1 TEL62 crate housing 1 TEL62 If possible, try to combine at least 2 TEL62 in 1 crate

Do we need a special module to combine 13 flow-control signals for each chamber?

Services There is no manpower for DCS All designed to run without


TTC distribution

2 sets of LTU+TTCex ordered 1 set used in experiment 1 set in lab and spare

Each of 4 chambers has got a TTC link with 1:16 splitter for 12 SRBs and 1 TEL62

TTCex equipped with 4 lasers Either each laser drives directly chamber link Or we use optical 1:4 splitter and keep 3 lasers

as spare (failure rate of lasers not known)



Plans Finish characterization and testing of the frontend

Validation on frontend in February Re-design (some modification to existing cover design) and pre-production -> April Full production start in June

Finish characterization and testing of the backend Validation coupled to frontend Design of full SRB till April Prototypes of full SRB in June Firmware

Simplified version June Full functionality September (?, no chance if we participate to dry run)

TEL62 Mezzanine design starts after validation of FE and BE Probably till April Prototype in June Firmware September

Test beam 2 weeks in June

Dry run ??? Technical run

Partially equipped module-0. Final components as much as possible. If mezzanine and TEL62 firmware not ready, readout through VME

na62 straw detector read-out system

Documents

daq plans peter lichard

etc8 straws

view480 straws

triggerstraw detector

drift time measurement

layers4 layers of straws

daqneed control

arrival time