Muon Cathode Strip Chambers

Detectors

• Total # of Anode channels :                      183168
• Total # of  Cathode channels :                  231552
• Total # of AFEB :                                         11448 (16 channels)
• Total # of CFEB:                                          2412 (96 channels)
• Total # of DAQMB or CLCT/TMB or ALCT :     540
• Total # of Chambers :                                                    468

Data Rates

• Average LCT rate per chamber :                             22.62 kHz                     (300kHz)
• Average L1A and LCT rate per chamber :              226 Hz                        (3kHz)
• Data size at DAQMB with one LCT:                           2.8 kB
• Average Data rate per chamber  or  DAQMB:      ~1032 kB/s                 (~9MB/s)
• Average Data rate per DDU (one DAQMB per DDU) :  ~ 1.03 MB/s

                                                        ( 9     DAQMB pre DDU):  ~  9.3 MB/s
• Total Data rate         :  1032 kB/s x 468 = 483 MB/s
• Average muon event size for each L1A trigger :  483 MB/s   / 100kHz (L1A) = 4.8 kBytes

At DDU level, the event size for each L1A trigger is
                             4.8kBytes / number of  DDU  = 9 Bytes  (for  DAQMB = DDU)  or 80 Bytes (DAQMB = 9 x DDU)

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Above numbers vary depending on ME sections. 
For example, ME4/1 has 112kHz LCT rate which is 5 times higher than the average. 
So, the Maximum conservative data rate can be drived from the highest LCT rate chamber and MC uncertainty.

Detail CSC Data Rate Calculations

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Chamber Rates

• CFEB has 96 channels and AFEB has 16 channels.
• Chamber counts are a combination of both symmertic endcaps.
• The ME 1/1 chambers have divided cathode strips, 64 strips on top, 48 stips on bottom; ignoring the Lorentz tilt of the ME 1/1 anode wires, the chamber is effectively two logically distinct pieces, each with a DAQMB.
• The ME 4 chambers are not part of the current baseline design.  But, ME4/1 is most likely to be built.
• It must be noted that the highest rate occurs in ME4/2, a result of insuficient shielding againt back-scattered particles with the shielding model used. If ME 4 is used, the real system would involve better shielding.
• A conservative estimate of the LCT rate, we use 300 kHz per chamber independent of chamber types. The LCT rate in a chamber section covered by 1 FEB is, conservatively, 300kHz/(5 FEB's) = 60 KHz. The rate of (Lev-1)(LCT) coincidence is 100kHz x 300kHz x 100ns = 3 kHz per chamber or 0.6kHz in a chamber section covered by 1 FEB.

However, this rate is MUCH MUCH  higher than what expected from MCs as shown below.

Data Volume

• a) # FE Chips X 16 = # Channles
• b) Integrated rate is from the TOP table using each ME section LCT rates.
• c) L1A Rate (100kHz) X LCT Rate X 100ns (worst case time slop. 75ns might be better. +-1 CMS clock)
• d) 2.8 kBytes assumed for one LCT.  (ex:  0.152 kHz x 2.8kB = 426 kB/s )

    Also, you need to account NO LCT rate,(ex: ~100kHz x 4Bytes = 400 kB/s )
    For more detail, see below and  refer to DDU input format and DDU output format
• Data size at DAQMB ( WORD unit is used since 16bit FIFO all over the place )

 

	LCT  x  L1Acc (words)	no LCT x L1Acc(words)
Header Words	6	0
ALCT99	10 (Head) + 360 *	0
CLCT99	10(Head) + 210 **	0
CFEB	( 96 + 2(check)) x 8 = 784	0
Trailer Words	2	2(even words)
Total  with 1 LCT	1382 (2.8 kBytes)	2 (4 Bytes)
Total with 1 LCT w/o CLCT 99	1162 (2.3 kBytes)	2 (4 Bytes)

* Depends on how many ALCT channels are on a chamber
    (  36(#AFEB/chamber)X16 (channels) X 5(time bins) /  8 = 360 bytes  )
** 48 bits/CFEB X 5 (CFEBs) X 7(time bins) /  8 = 210 bytes
--- ALCT, CLCT sends 8 bit wide data to DAQMB 16bit wide FIFO due to the constraint on DDU bit and Glink (16bit)
          --->  So, a lot of empty bits are going to. This is not included in the number at the moment.
--- At present,  CLCT read out all boards. In future, it can do only for CFEB with LCT or  No Data for CLCT.
        ( CFEB data is better than CLCT data which is good for trigger checking or other system check )
• e)  Average L1A+LCT Rate per chamber is 0.152 kHz which means only 0.15% (=0.152 / L1A rate)of chambers has LCT.

      0.15% of 468 chambers is 0.7 chamber has a LCT for each L1A.  Ofcourse, this highly depends on which section of ME.
• f)  1 Chamber ~ 1 DAQMB which is valid for except ME1/1
• Given the uncertainty of the rate Monte Carlo, a conservative estimate would include an additional factor of about 5. That is, one should allow for  482 MB/s X 5 = 2.4 GB/s into the switch.

DDU Distribution

A rough estimate can be made nonetheless.

Present S-link :  32bit 40MHz ===>   160 MB/s                   ====> Already can handle  9 chambers/DDU rate,
                                                                                                                         9.3 MB/s x (10 conservative factor )
                                                                                                   =====>  More Chambers per DDU  ???????????

Maximum S-link : 64bit 100Mhz ===>  800 MB/s
 

Guide line from RUWG : Event size at DDU level  ~ 2kB   or   200 MB/s    at  100kHz trigger rate

*******EMU is much small than this guide line even 9 DAQMB connected to a DDU. *************