Trigger systems UA and LEP

1
Trigger systems UA and LEP

• bigger experiments ? more data per event
• higher luminosities ? more triggers per second
• both lead to increased fractional deadtime
• use multi-level triggers to reduce deadtime
• first level - fast detectors, fast algorithms
• higher levels can use data from slower detectors
  and more complex algorithms to obtain better
  event selection/background rejection

2
Level 1

• time one ? few microseconds
• NIM/Camac for small systems
• dedicated logic for larger systems (ASIC, FPGA)
• reduced granularity and precision
• calorimeter energy sums
• tracking by masks

3
Level 2

• 1) few microseconds (10-100)
• hardwired, fixed algorithm, adjustable parameters
  (LUT)
• 2) few milliseconds (1-100)
• dedicated microprocessors, adjustable algorithm
• 3-D, fine grain calorimetry
• tracking, matching
• topology

4
Level 3

• millisecs to seconds
• processor farm
• microprocessors/emulators/workstations
• full or partial event reconstruction
• after event building (collection of all data from
  all detectors)

5
Summary

• Trigger - multi level triggers with
• fast level 1
• local data storage until after level 2
• read-out and event-building for level 3
• DAQ - bus based read-out to processor farm
• event building in processor farm
• level 3 trigger in processor farm
• output to tape
• near on-line reconstruction

6
UA1 trigger and data acquisition

• luminosity 1030 /cm2/s
• bunch separation 4 µs 250kHz
• interaction rate lt105 Hz
• channels 105
• read-out rate 1?10 Hz
• transfer rate few Mbytes/sec
• storage rate 0.5Hz
• data transferred to multi-event buffer
  (derandomizer)
• event read-out and event building by VME DMA

7
UA1 Trigger

• Level 1 lt4 µs using hardwired processors
• muon track segment em showers jets ET
• rate 30 Hz. (reduction factor 103 ? 104)
• zero deadtime as decision time lt bunch separation
• Level 2 7 ms using 68020 CPUs
• muon tracking using drift time
• 3-D calorimetry position detectors
• rate 3 Hz (reduction factor 10)
• deadtime (30x0.007 20)
• front end frozen during level 2 decision time.

8
UA1 Level 1
9
UA1 Level 2 and 3
10
UA1 Trigger (cont).

• Level 3 100 ms using 3081E farm
• partial event reconstruction
• calorimeter and tracking
• event topology
• reduction factor 3
• deadtime (3Hz x 0.03s 10)
• time to read data into processor system (30 ms)

11
LEP (ALEPH)

• luminosity 1031 /cm2/s
• bunch separation 22 µs 45kHz (4 bunches) 11
  µs 90 kHz (8 bunches)
• event rate 0.1 Hz
• channels 106
• read-out rate 1?3 Hz
• transfer rate 10 Mbytes/sec
• event building over VME (Fastbus pre1994)
• optical link data transfer to a VAX system.
• VME/G-64 used for monitoring and slow control.

12
ALEPH trigger

• Level 1
• 4µs decision time 6 µs clear time (lt11µs )
• hardwired processors
• calorimeter energy sums and ITC tracks
• accept rate 3? 30 Hz (5 Hz typ.)
• zero deadtime as process time lt bunch separation

13
ALEPH trigger (cont.)

• Level 2
• 60µs decision plus clear time
• hardwired LUT processor for TPC data
• operates on L1 track triggers only.
• accept rate 2 ? 6 Hz (2 Hz typ.)
• deadtime 2bx x 5Hz(L1) / 45kHz 0.02, 5bx
  x 5Hz(L1) / 90kHz 0.03

14
ALEPH trigger (cont.)

• Level 3
• readout time 10ms.
• processing time 1s/processor
• microVAX farm (part reconstructed data)
• accept rate 1?3 Hz (design rate 1Hz)
• deadtime for readout 10ms x 2Hz(L2) 2

15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19
(No Transcript)
20
(No Transcript)
21
(No Transcript)
22
(No Transcript)
23
(No Transcript)
24
(No Transcript)
25
(No Transcript)