CSC LCT Occupancy per LHC Bunch

Results based on ~1 million minimum bias events in full ORCA simulation

Equivalent to ~50,000 bunch crossings, assuming ~17 minimum bias events per BX

Assumes 100 kHz rate of random Level-1 triggers, and no Level-1 algorithms are applied

Correlations with Level-1 "good physics" triggers are NOT INCLUDED

This is our best-estimate from ORCA as of September 2001

First possibility: assume that only CLCT coincidence required with L1A (16-time samples unless noted)

CSC per BX Occupancy for CLCT-only trigger	1 BX only	3 * 1 BX Result: for ⁺/-1 BX	EMU Data Bandwidth	# Readout SLINKs Needed
No Neutrons, all CSCs	0.6	1.8	1070 MB/sec	6
Add Neutrons, all CSCs	1.2	3.6	2040 MB/sec	12
Add Neutrons, but no ME4/2	0.9	2.7	1560 MB/sec	9
Add *3Neutrons*, all CSCs (imposed 3 safety factor)	2.4	7.2	4000 MB/sec	23 [36]
Add *3Neutrons**, but no ME4/2	1.5	4.5	2530 MB/sec	15 [18]

Second possibility: assume that ALCT.and.CLCT required with L1A (16-time samples unless noted)

CSC per BX Occupancy for ALCT+CLCT trigger	1 BX only	3 * 1 BX Result: for ⁺/-1 BX	EMU Data Bandwidth	# Readout S-LINKs Needed
No Neutrons, all CSCs	0.6	1.8	1070 MB/sec	6
Add Neutrons, all CSCs	0.7	2.1	1230 MB/sec	7 [9]
Add Neutrons, but no ME4/2	0.65	2.0	1170 MB/sec	7 [9]
Add Neutrons, all CSCs: 8-time samples	0.7	2.1	720 MB/sec	5 [6]
Add Neutrons, but no ME4/2: 8-time samples	0.65	2.0	690 MB/sec	4 [6]
Add *3Neutrons*, all CSCs (imposed 3 safety factor)	0.9	2.7	1560 MB/sec	9
Add *3Neutrons**, but no ME4/2	0.75	2.2	1280 MB/sec	7 [9]
Add 3*Neutrons, with no ME4 at all	0.70	2.1	1230 MB/sec	7 [9]
Add *3Neutrons, all CSCs: 8-time samples**	0.9	2.7	900 MB/sec	5 [6]
Add *3Neutrons, but no ME4/2: 8-time samples**	0.75	2.2	750 MB/sec	4 [6]
Add 3Neutrons, with no ME4 at all: 8 samples*	0.70	2.1	720 MB/sec	4 [6]

Notes:

The number in [brackets] is the number of Readout S-LINK/DCCs required for our planned DDU configuration

There is one DMB per CSC, and up to 15 DMBs per DDU
EMU plans to have 3 FED crates in the counting house, each with 12 DDUs and at least two DCCs
This crate structure requires an integer multiple of 3 readout DCCs (Data Concentrator Cards)

one readout S-LINK per DCC

Average event volume is 5400 bytes per CSC for 16-time samples, 3000 bytes for 8-time samples
Total EMU Average Data Bandwidth is determined by

Bandwidth = Occupancy * L1A rate * DMB Event Size + Overhead

L1A rate assumed to be 100 kHz; assume that each L1A originates from a proton bunch
DMB Event Size = 5424 bytes (16-time-samples) OR 3024 bytes (8-time-samples)
Overhead (due to S-Link-64 Headers and Empty-Events) = L1A Rate * 24 bytes/DDU * 36 DDUs = 86.4 MB/s nominal

Average EMU Trigger Rates

These are the AVERAGE rate estimates

The maximum instantaneous "burst" rates are certainly higher (but not simulated yet)

Average DDU trigger rate = Occupancy * L1A rate / 36 DDUs
Average DMB Trigger rate = Occupancy * L1A rate / # CSC-DMBs

540 DMBs in full design (assumes ganged ME1/A)
468 DMBs with descoped ME4/2

Our old estimate for CSC occupancy was only ~0.8 per 3 BX

The old estimates used a naive approximation model for neutron and charged particle LCT backgrounds

Old average LCTxL1A for all CSCs in a DDU was 2205 Hz
Old Occupancy = 2205 Hz * 36 DDUs / 100 kHz = 0.794

Occupancy here refers to the average number of CSCs with an LCT in any given bunch crossing

17.3 minimum bias events per crossing is assumed
25 ns beam crossing period
Preliminary estimates suggest that the addition of simulated "good physics" events and applying the Level-1 trigger algorithms in ORCA could increase the average occupancy by ~60% or more beyond what is stated here!

Latest Update 5/9/02.

gilmore@mps.no_.-more-._spam.ohio-state.edu