1. NA62 Straw tracker electronics
Toward final detector
Peter Lichard – CERN PH/ESE/FE group
New to project
Trying to understand requirements and what has been already done
I’ll repeat what you know, SORRY, that’s for my understanding!
Requirements on straw tracker from electronics point of view
Good quality data (drift time)
130 nm resolution for single straw
Efficiency -> 100%
This is required
For all distances from the wire
All along the length of straw
Low noise. What is acceptable for event reconstruction and trigger?
3 % ?? (even cross talk measurement yielded 4 %)
What about efficiency and resolution versus rate?
Ion tail cancellation
Integration in global DAQ and TTC
Reliable and stable operation with tools for monitoring

2. Drift time 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. Only DAQ or also TRIGGER ?
used as anti-coincidence ? Requirements on noise the same?

3. Straw properties

4. Straw properties Impedance changing dramatically in useful frequencies
~1000 (1 MHz) -> ~350 Ohms (20 MHz)
Attenuation very high in useful frequencies
2.3 at 20 MHz
Phase shift will create dispersion
lower frequencies propagating slower then high frequencies

5. Straw termination
Termination could be used to improve signal amplitude and spread
Far end open
signal created at this end of straw reflects back in right polarity and helps to increase signal amplitude at the preamp (compensates partially attenuation losses)
Signal created close to preamp will reflect back and return to preamp after ~ 15 ns, attenuated almost 6x
Far end terminated with high impedance ~1->10 kOhm
Can help to eliminate long tails (lower frequencies)
Does not influence very much high frequencies
Close end connected directly to preamp (through protection resistor)
Can increase signal amplitude if Rin + Rprot < Zstraw
Signal will reflect back in opposite polarity, input current to charge sensitive preamplifier will be higher
Status
Number of tests done in terms of sensitivity using charge injection and Fe55
To do
Verify straw termination with particles and influence on resolution and efficiency

6. Quality of data?
“Digital noise” – visible by reconstruction team and/or trigger
Sources
Electronics thermal noise
Discharges
Cross-talk
Fake hits
Missing hits
Efficiency
Rate dependent

7. CARIOCA noise

8. DISCHARGES Discharges (sparks?) Status To do Fake hits
damage to straw, metal coating?
recovery of electronics
Damage to electronics
Input protection
Status
Not known
To do
Measure rate
Check damage to straw metallization
Test input protection
Dead/recovery time of electronics?

9. Crosstalk Internal External Types of crosstalk Status To do
Between straws, electronics channels, etc.
Signal returns (“grounds”), sensitive input lines
External
From experimental hall, other devices, ground loops, etc
Grounding and ‘earthing’
Connection to metallic structures, safety ground
Need to fix voltage potential between remote systems
Types of crosstalk
Conductive
Often prevailing
Conductors shared by different signals, voltage developed on conductor impedance from 1 channel appears as a noise on another channel
Capacitive
Between straws, outputs to inputs
Inductive
Parallel lines, e.g. straws connection to preamp
Status
Detector crosstalk measured at testbeam 2009, 4% for thr=10fC
To do
Separate signal returns from straws to reduce conductive crosstalk
Study capacitive crosstalk (depends strongly on pream input impedance)
With FE prototype boards, study the digital output crosstalk to straws

10. ‘Fake hits’ PASH too fast in comparison with detector
Few hits per track, primary clusters start to be visible
From DAQ and trigger point of view
Special kind of noise
Instead of 1 long signal, few short pulses
Happens when PASH output pulse width < time between clusters
CARIOCA with 30pF input capacitance has output pulse width ~15 ns
‘slow’ gas primaries are spaced ~20 ns
CARIOCA was designed for Ar/CO2/CF4 (40:55:5)
1/(t+1.5ns)
Ion tail 20us
‘slow’ gas CO2/iso/CF4
1/(t+2.6ns)
Ion tail 200 us (???, from parameters)
Status not known, was it observed/searched for ?

11. Comment on gas
Electronegative gases (CF4, O2) are changing the signal shape
Less charge then expected
Ar/CO2 ‘follows’ 1/(t+t0)
(COSY-TOF straw 1m/1cm)

12. Slow versus fast gas
TH=6
simulation

13. External crosstalk, grounding and shielding
Interference with external objects
Voltage potential between front and back end
Safety ground
A lot of work already done!
To Do
Verification with new prototype
Experience
Straw signal returns must be separated as much as possible
All SigRet connected at PCB level close to input of preamp
The same point connected to metal case (vacuum tube)
Straws connected to GND only on 1 side
Metal case connected to experiment earth
All shields (data, control, LV, HV) should be connected on both sides; 1 side directly, other through dumping impedance
Backend (crate) connected to experiment earth. This provides the same potential for FE and BE – important for data transmission
No direct connection between FE and BE ground apart EARTH => no GND loops PA
CONNECT
PCB GND PLANE
METAL CASE (VACUUM TUBE)
SAFETY GND “EARTH”

14. Rate effects Resolution and efficiency space charge in detector
HV on anode
Ion tail cancellation
Need to validate combination CARIOCA<->slow gas
Status
Lot of measurements done
But difficult to compare different combinations
To do
more high-rate runs with slow and fast gas at low threshold

15. NA62 straw tracker electronics
PASH followed by comparator
Can we confirm CARIOCA as a final candidate after next testbeam?
Match straw properties (gas)
Performance
Connectivity
Trend in electronics
PCB price increasing
Processing power decreasing
Everything in 1 cable
Just 1 cable to handle
Services and data in the same bundle
Can go to 1 backend board doing everything
Easy to use, cheaper
Separate cables
More difficult to handle
Can go to different places
Need more boards with separate functions
More expensive

16. NA62 straw tracker electronics
TDC
What is required TDC resolution? 3/4/5 ns?
Minimum space between hits?
Do we want to have a local monitoring, DAQ system for testing, testbeam, etc?
Able to run standalone
Integrate with global DAQ when needed
Or, ‘all done’ in global DAQ?
How easy/difficult is it to adapt NA62 DAQ for testbeam, lab testing, other purposes?
Should we participate to trigger?
Falling edge always the same, tag straws belonging to the same track
Sometimes even this crude resolution is sufficient
Precise track position from rising edges
Physics motivation, is it useful?

17. NA62 straw tracker electronics
Front end board functionality
Frontend board designed and produced for 4 cells
Two CARIOCA chips (16 straws) for signal processing
12-bit DAC with I2C control for threshold setting
LVDS drivers for outputs (need a test whether they are needed)
One power supply line to the board, all required voltages have a regulator on the board
Front end PCB
Gas tight PCB using blind vias
thick PCB to ensure mechanical stability under pressure
High voltage connection integrated on the board + HV filter
gas feedthrough
numerous configurable GND connections to try different grounding scheme with detector

18. NA62 straw tracker electronics
There are 3 options considered for straw tracker readout 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 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 requires bulky cables entering mezzanine, this must be proved possible. Otherwise we would need to reduce the number of straws per TELL Design custom board. 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.
Consequences For all 3 options I see non-negligible effort needed in electronics design. 2. and 3. probably more then 1. Cost implications should be carefully evaluated together with securing spare boards. Custom board may prove to be the cheapest solution but requires securing sufficient number of spares as later production could be very inefficient (which, in fact, could be true for TELL1 as well) "Obsolete" components like quartz, QPLL, TTCRX, etc are needed for every option; so whatever solution we choose at the end, we need to order them as soon as possible.

19. NA62 straw tracker electronics
Plans near future at CERN
Equip new detector prototype with prototype FE boards based on CARIOCA
Build small VME readout, possibly scalable to full DAQ
VME 9U board
Contains
TDC (3ns?)
Data buffer
Timing
FE control (threshold, test pulses)
Data collected by SBC
Tests with Fe55
Variation of signal along length
termination
X-talk
Testbeam
Resolution and efficiency for different rates to verify selection gas-FE
Try to better understand readout based on TELL1 board
Compare/optimize DAQ solution
Functionality
Budget
Amount of work

20. NA62 straw tracker electronics
Needs not covered now in electronics
Discharges
Noise
Damage to straw and chip
Deformed straw
What can be tolerated by FE electronics?
Probably more

21. NA62 straw tracker services and DCS
Need to understand them now so they could be designed in the system
Do we want to have a local DCS interfaced to NA62 DCS or just be integrated?
What do we want to control and monitor
HV power supplies
3kV (CO2), 2kV (Ar); current for max particle rate?
granularity
Settings for voltage, max current, on/off, output current monitoring
LV power supplies
Each FE board has got a regulator, this avoids difficult voltage tuning
8V/~100A, commercial crate with modules, like Wiener
granularity, 1 PS/view?
Temperature
Straw or structure temperature
Gas temperature
FE board
How many places?
View frame or station ?
Gas entry/exit ?
all PCBs ?
Do we also want to CONTROL the temperature?
Cooling electronics
Cooling/heating gas/straws

22. NA62 straw tracker services and DCS
Straw gain
1 control straw per view? Or?
Direct feedback to HV to keep gas gain constant?
Crates
On/off
reset
Monitoring voltages, currents, temperatures?
Types HV LV
VME 9U
Special for DCS?
Other
Gas pressure
Gas flow ?
Protocol for DCS
CANBUS
I2C
Other?
Better to fix one if possible

23. Tough decisions needed as soon as possible
Conclusions
Tough decisions needed as soon as possible
Gas-frontend chip
DAQ
DCS + services
Complement measurements to convince ourselves and others that this detector will fulfill requirements