Trigger Glossary

Central Trigger Board. Piece of Electronics that receives simple inputs (primitives) from all subsystems and issues triggers based on pre-configured conditions
Better described as Timing and trigger distribution system. It distributes a common clock to all subsystems and is responsible for transmitting the triggers from the CTB to the other systems. It can inhibit triggers from the CTB.. It is also the system that generates the random triggers.
What the CTB produces and the timing system distributes. Everything else that is called that way are not really triggers, but trigger inputs, or primitives, or...
Low Level Triggers. These are pseudo-triggers (interesting conditions) that are matched at the subsystem level and are fed to decide on global triggers.
High Level Triggers. Also known as global triggers. These are the real triggers that are matched by combining inputs of several LLTs and propagated by the timing system.
CTB data stream
Every time a LLT or HLT is produced, a 16 byte data word is generated. These are aggregated and sent periodically to the DAQ through a TCP connection.
Board Reader
The artdaq software driver that communicates with the CTB. It is responsible for passing the configuration and receiving the data stream. It reformats the data sent by the CTB into a format that is then stored into the events.
CTB software
The software that runs on the ARM core of the CTB. It is responsible for configuring the firmware and communicating with the board reader.

CTB Trigger Definitions

For more details, here's a link to the spreadsheet where all LLT's and HLT's that are in place :

NOTE: The trigger word sent to the DAQ by the CTB shows the state of all HLTs at a given moment. In the list below the index of the HLT corresponds to the bit in the trigger word payload.

ID Payload Bit Description
HLT_0 0 Random trigger. Usually not used. Can be configured to fire only during beam spill.
HLT_1 1 Beam particle trigger. No particle selection.
HLT_2 2 Beam particle trigger with Cherenkov based particle selection. HP=1,LP=1. In low energy beam this tags electrons
HLT_3 3 Beam particle trigger with Cherenkov based particle selection. HP=0,LP=1.
HLT_4 4 Spare
HLT_5 5 CRT trigger matching any US/DS coincidence within 240 ns. Only enabled outside the beam spill.
HLT_6 6 Spare
HLT_7 7 Beam particle trigger with Cherenkov based particle selection. Excludes HP=1,LP=1. On low energy beam this is a heavy particle trigger.
HLT_31 31 Random trigger. Usually not used. Can be configured to fire only outside beam spill.

In schematic form, the assignment of HLTs to the payload of the HLT word is,


Similarly, the assignment of the LLTs to the LLT word payload is,


Central Trigger Board Cable/Fiber Connections

See the link for a spreadsheet with details of which cables/fibers are connected to which channels on the CTB.

Central Trigger Board Data Words

See the link for a spreadsheet for details of the CTB words.

Run Stats

Timing summaries are available on np04-srv-012 : /log/runsummary/

The important numbers for physics data taking are FakeTrig0 and BeamTrig. FakeTrig0 are fake triggers generated by the timing system for partition 0 (the standard partition for physics). BeamTrig refers to triggers coming from the CTB. In each case, the first column is accepted triggers, and the second column is rejected triggers.

An example:

TimeSync        5816    0
Echo    0       0
SpillStart      293     0
SpillStop       293     0
RunStart        1       0
RunStop 0       0
WibCalib        0       0
SSPCalib        0       0
FakeTrig0       10934   601
FakeTrig1       0       0
FakeTrig2       0       0
FakeTrig3       0       0
BeamTrig        1125    75
NoBeamTrig      0       0
ExtFakeTrig     0       0

CTB summaries are in /nfs/sw/trigger/counters

Good Part is the total number of particles identified by the beam instrumentation trigger. The HLT numbers refer to the number of each HLT trigger that has been accepted. In this case, 280 triggers have been accepted with HLT 7 ( with Cherenkov cuts) out of a total of 871 if only the basic Beam Trigger was used. Example:

Good Part        871
Total HLT        280
HLT 0    0
HLT 1    0
HLT 2    0
HLT 3    0
HLT 4    0
HLT 5    0
HLT 6    0
HLT 7    280
Topic attachments
I Attachment History Action Size Date Who Comment
PNGpng hlt_trig_payload.png r3 r2 r1 manage 126.6 K 2018-10-20 - 00:15 JonathonLeeSensenig  
PNGpng llt_trig_payload.png r1 manage 114.0 K 2018-10-20 - 00:16 JonathonLeeSensenig  
PNGpng llt_word_payload.png r1 manage 113.8 K 2018-10-20 - 00:09 JonathonLeeSensenig  
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Topic revision: r6 - 2019-05-14 - AndreaDellAcqua
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