1. Level-zero trigger status
Francesco Gonnella
CERN – TDAQ Working group
16 December 2015

2. NA62 time alignment (1/2) before 2015 since 2015 time trigger
Physics 1
trigger latencies
Physics 2
Physics 3
since 2015
time
trigger
fixed trigger latency
TDC offsets
Physics
In 2014 run we tuned the latency of every detector in order to match physics
Since 2015 we use the TDC offsets (directly fed to HPTDC chips, through the XML configuration files) to move physics and used the same latency in every detector.
Thanks to this choice, all the detectors produce synchronous data from the very beginning, as if the cable length was properly tuned to synchronise them all
This means that data are time-aligned both for Level 0 and for Level 1 and 2 trigger for free
Francesco Gonnella - University of Birmingham
16 December 2015

3. NA62 time alignment (2/2) Event Dump Orange plots
Event header and number length c83 timestamp 3ec76 trword 38801
Number of detectors: 9
Detector 4 offset 11 (hex) 17 (dec) length 2c (hex) 44 (dec)
c 0003ec f 0003ff ff ff ff c
ec f 0003ff ff ff ff ec76
f 0103ff ff ff ff c
ec f 0003ff ff ff ff c 0003ec76
f 0003ff ff ff ff c 0003ec f
ff ff ff ff00
Detector 18 offset 3d (hex) 61 (dec) length 7 (hex) 7 (dec)
c 0003ec f 0003ff ff ff ff00
Detector 40 offset 44 (hex) 68 (dec) length c (hex) 12 (dec)
ec dda
Detector 10 offset 50 (hex) 80 (dec) length 4f (hex) 79 (dec)
ec ff ff ff ec76
ff ff ff00 010a001c 0003ec76 020a040f 0003ff00
ff ff ff c 0003ec f 0003ff ff00
ff ff c 0003ec f 0003ff ff ff00
ff c 0003ec f 0003ff ff ff ff00
c 0003ec f 0003ff ff ff ff
ec ff ff ff c 0003ec f
ff ff ff ff ec ff00
ff ff00 010b001c 0003ec76 020b040f 0003ff ff ff00
ff ec ff ff ff00
Detector 30 offset 9f (hex) 159 (dec) length 6 (hex) 6 (dec)
ec ff ff ff00
Orange plots
Thanks to the TDC-offset tuning, data are time-aligned at the raw level with respect to the trigger time
An easy cross check can be performed in the reconstruction and by eye with the event-dump software
If we plot the raw time ps) minus the trigger time 100 ps) we obtain the so-called ‘orange plots’ that are fundamental for data monitoring
Francesco Gonnella - University of Birmingham
16 December 2015

4. What’s in a trigger primitive?
NA62 trigger-primitives are made of two 32-bit words containing:
Primitive IDs depend upon the sub-detector, nevertheless some general rules exist (and must be respected):
Every bit must carry an information independently of the others, so that the L0TP can take decisions based on single bits
L0TP can require 1, 0 or ignore a bit, cannot (by construction) perform any OR operation among the bits of a primitive ID and among primitive IDs of different detectors. If an OR is needed it must be calculated by the detector itself prior to sending the primitive to L0TP
Bit 15 must be at 0 for any physics primitive and 1 for calibration primitives
Bit 14 must always be at 1 for every primitive (MUV3 guys won)
31 TimeStamp (25 ns) 0
31 primitive ID 16
15 reserved 7
7 fine time (100 ps) 0
Francesco Gonnella - University of Birmingham
16 December 2015

5. What’s in an MTP?
A MTP (Multi Trigger Packet) is a UDP packet sent from the detector participating to the level-0 trigger to the L0TP
The MTP are sent every 6.4 us
If no primitives were produced in a given 6.4-us interval, an empty MTP is sent
The L0TP needs MTPs to be delivered periodically in order to be sure all the primitives have arrived before starting to evaluate the coincidences
Other than primitive data, an MTP contains a header (64 bit):
The time stamp (25ns) at which the packet itself was sent
The detector ID and the subdetector ID
The number of primitives contained in the packet and the dimension of the packet in bytes
Francesco Gonnella - University of Birmingham
16 December 2015

6. Level-0 trigger bit-mask
Every detector that is participating to L0 and is producing primitives can send 15 independent ‘type of triggers’ (PrimitiveID)
This type of triggers strongly depend on the detector itself
Every type of trigger is represented by a bit in the trigger mask for that detector
The meaning of each bit is a matter of the L0 experts (and is or should be written in the documentation)
Nevertheless bit 14 (0xE) must always be at one so it can be used:
for triggering on any primitive, if set to 1, (all other bits to don’t care)
for vetoing on any primitive, if set to 0, (all other bits to don’t care)
for ignoring any primitive, if set to don’t care (all other bits to don’t care)
Francesco Gonnella - University of Birmingham
16 December 2015

7. Detectors participating in level 0 trigger
CHOD
Primitive: Coincidence between two slabs
ID: multiplicity and quadrants
RICH
Primitive: Time clusters
ID: Hit multiplicity
LAV12
Primitive: Coincidence between high and low threshold crossing
ID: Hit multiplicity (possible cut on ToT)
MUV3
Primitive: Coincidence between the 2 PMTs coupled to the same tile
ID: Position, Multiplicity, see documentation
IRC/SAC (using LAV firmware)
LKr (LKr, MUV1-2, IRC/SAC)
Primitive and ID: Energy threshold, number of clusters
Francesco Gonnella - University of Birmingham
16 December 2015

8. Trigger-primitive acquisition system 1/3
7 switches were added to duplicate trigger-primitive streams going from the detectors to the L0TP
Daemons running on two na62 PCs, na62prim1 and na62prim2, acquire trigger-primitive data and store them on na62merger1
The primitive-online-monitor uses this data to provide fast tiggerless information that was fundamental for beam monitoring and for trigger debugging during 2015 run
The switches send data coming from input port (3) to the output port (1) and mirror the input port (3) onto one output port (8)
2 more ports (6, 7) are used to create a private LAN to remotely configure the switches themselves
Every port can be enabled or disabled remotely (from the control room), so that the trigger-primitive stream coming from every detector can be enabled or disabled for primitive acquisition and/or for real trigger to L0TP
Francesco Gonnella - University of Birmingham
16 December 2015

9. Trigger-primitive acquisition system 2/3
to PC-Farm
L0TP A B C D E F G
to LTU (to send triggers to detectors)
USB (firmware programming and
configuration)
na62prim1 2 3 4 5
na62prim2 2 3 4 5
na62l0tp
Switch
Switch
Switch
Switch
Switch
Switch
Switch
private LAN
primitive
primitive
primitive
primitive
primitive
primitive
primitive
CHOD
RICH
LAV12
MUV3
IRC/SAC
TALK
LKr
Francesco Gonnella - University of Birmingham
16 December 2015

10. Trigger primitive acquisition system 3/3
Francesco Gonnella - University of Birmingham
16 December 2015

11. Primitive data and decoder
Detector ID
Send Timestamp
All the information is decoded into a root tree
The root file is primitive- based
The information contained in the MTP header is saved in the entries of each primitive contained in the packet
Nothing is saved for empty packets
Integrated in official NA62 analysis
Subdetector ID
100075f1 0b
100076f1 0b a c3
Number of primitives
Dimension of the packet (Bytes)
Timestamp
Primitive ID
Fine time
Francesco Gonnella - University of Birmingham
16 December 2015

12. Trigger-primitive monitor
The primitive OM has become a fundamental monitoring-tool during 2015 run
Francesco Gonnella - University of Birmingham
16 December 2015

13. Trigger-primitive syncronisation
In order to allow the L0TP to perform coincidences and vetoes, primitive coming from different detectors must be synchronised
We synchronised the primitives by changing the TDC offsets so that all the ‘physics’ moves accordingly
What we call ‘synchronisation’ has nothing to do with the time of arrival of the primitive to the L0TP, it has to do only with the value of the primitive Timestamp and Fine-time
In the end, synchronising the trigger-primitives is exactly the same as time-aligning detectors for data acquisition
Exception made for the LKr having two completely independent systems for data acquisition (CREAM) and primitive generation (TEL62).
Francesco Gonnella - University of Birmingham
16 December 2015

14. Cross-correlation between primitive streamsxi
50 ps yi
time
50 ps xi
yi+t
The C(t) is plotted to find a peak
Considering just the centre (mainly 100* *106 )of the burst
The absolute value does not have a real meaning as the matching windows is much smaller than L0TP’s window.
Francesco Gonnella - University of Birmingham
16 December 2015

15. Syncronisation examples
Cross-correlation plots can be used both for synchronising the primitive generation and for spotting anomalous behaviours
Francesco Gonnella - University of Birmingham
16 December 2015

16. MTP alignment (1/3)
The L0TP works under the assumption that the primitive contained in the Nth MTP has a TS that matches the MTPs of the Nth packets of all the other detectors
The L0TP waits for 3 MTPs to arrive for the reference detector (CHOD in the example below) before starting to compute coincidences
An MTP offset n can be set into the L0TP that discards the first n MTPs before starting to process them
In order to perform the alignment, the difference between the timestamp of the MTP and the primitive time stamp is used
In the example the LKr MTP offset should be set to 3
CHOD
LAV
MUV3
LKr 10 - 11 8 12 9 13 14 15
L0TP tolerance
Francesco Gonnella - University of Birmingham
16 December 2015

17. MTP alignment (2/3) MUV3 LKr IRC CHOD LAV12 X axes are in 25ns unit
Francesco Gonnella - University of Birmingham
16 December 2015

18. MTP alignment (3/3) CHOD MUV3 LKr LAV
packets (6.4 us)
From this study we evaluate the difference in unit of packets to be set into the L0TP
The so-called ‘max delay detector’ must be set to be the detector with the biggest MTP offset
The primitive-correlation program automatically prints out the correct values
Such plots should be monitored during data taking
Francesco Gonnella - University of Birmingham
16 December 2015

19. The lucky case of SAC/IRC
SAC/IRC use LAV FEE boards that allow them to be readout by a TEL62 and CREAM (LKr readout system) at the same time
Thanks to LAV primitive-generating firmware installed in the SAC/IRC TEL62 primitive could be produced using LAVFEE internal pulser
L0TP was set to trigger on IRC/SAC primitives and triggers were sent to the whole experiment allowing us to look for a peak in data distribution
The peak was found in the CREAM data of SAC/IRC allowing to evaluate the offset between the two readout systems with no beam
This study allowed us to time-align MUV1, MUV2, and SAC/IRC readout through CREAM boards
The LKr level-0 system was also aligned using primitive-acquisition system and correlation software
Francesco Gonnella - University of Birmingham
16 December 2015

20. Conclusions The TDC-based time alignment proved to be the best choice
The trigger-primitive acquisition system is now well established and working
There might be the need of integrating it into Run Control
A downscale system should be implemented
Primitive data is integrated in NA62 analysis
The primitive raw-decoder is also committed
The trigger-primitive monitor is now a fundamental tool for NA62 data and beam monitoring
Primitive synchronisation and MTP alignment procedures are well established
Thanks to all the L0 team!
Francesco Gonnella - University of Birmingham
16 December 2015