PHENIX DAQ RATES

RHIC Data Rates at Design Luminosity PHENIX Max = 25 kHz Every FEM must send in 40 us. Since we multiplex 2, that limit is 12 kHz and 80 us. For Au-Au, Level-1 rate is ~1400 Hz - we sample every event in the level-2. For p-p, the interaction rate is 10MHz - need very good level-1 rejection. Au-Au: L = 2 x cm -2 s -1 p-p: L = 2 x cm -2 s -1 Design Luminosities

Assumptions: –A total period of 25 weeks for beam availability –RHIC duty factor = 50% –PHENIX duty factor = 50% –Collision region rms = 20 cm. –All running at Au-Au segment of 17 weeks: –First 7 weeks: RHIC: commissioning from ~10% to 100% of design luminosity PHENIX: Commissioning, calibrating, start of data-taking –Last 10 weeks: Running at ~100% of design luminosity (2 x cm -2 s -1 ) –300  b -1 (possibly 600) of integrated luminosity recorded p-p segment of 8 weeks –2 weeks to commission collisions –1 week to commission polarization (> ~50%) –5 weeks of polarized running at 5 x cm -2 s -1 –3.5 pb -1 of integrated luminosity recorded: Run Segments (“borrowed” from Bill’s RBUP)

Data Volumes UnSuppressed2.93 x 10^6 Au-Au Central4.02 x 10^5 10% occ Au-Au mbias1.61 x 10^5 2.5% occ Au-Au mbias1.26 x 10^5 2.5% occ, min fem header p-p mbias4.30 x 10^4 0% occupancy min fem header Data TypeSize (bytes) Overhead Packet > 22 x 10^3 Header FEM Header 53.2 x 10^3 Minimal FEM 18.1 x 10^3 Header (clk, evt, summary) Data TypeSize (bytes) Is the minimal FEM header really “the” mininal? Packet and FEM headers can be dropped from empty packets, but not from non-empty ones We are currently running with all headers and packets...

PHENIX Hardware Throughput Spews out data at 25 kHz* Must be able to make L1 decision in 40 beam crossings (GL1 + LL1) *EMC needs short format FPGA, TOF needs extra controllers to get < 40us output time. FEM fiber 40 MHz DC, TEC 20 MHz all else. (ie, 160 or 80 MB/s) LEVEL-1 Reads in FEM data, 0-suppress Process Data Joins Data, further processing High Speed Transfer to SEB DSPs 1-4 DSP 5 (1 per DCB) 20 MB/s Link Port Joins Data, further processing Joins Data, further processing 160 MB/s (40 MHz) Token Passing Bus PARTITIONER LVDS CABLE to Event Builder DCM FPGA

PHENIX Hardware Throughput Dual Buffer Storage in RAID Arrays running on Linux Box (one writes to HPSS, one reads from ATPs) 28? x 100Mbit ethernet 10 Gbit/s aggregate, 5 each way 155 Mbit/s NIC 30-40? MB/s RAID LVDS CABLE (from PAR) Buffer Data from DCM’s JSEB Input Card (PCI, 132 MB/s) 26? SEBs (NT 4) Assemble Events, Run Level 2 Trigger 28? ATPs (NT 4) Event Builder Buffer Boxes HPSS 20 MB/s Each SEB can write out at 155 Mbit/s, so max rate is (155Mbit/s - overhead)/event size 20 MB/s sustained max overall output rate set by HPSS into the buffer boxes is instantaneous rate. 155 Mbit/s NIC Fore ASX-1000 ATM Switch

Current Status, Event Size = 120 kBytes Event Rate ~ 600 Hz MVD Largest Granule

Some Personal Thoughts... For the Au-Au running, we want to be at 1400 Hz, and it would be even better to get to 2100 Hz if we want the coherent peripheral program to succeed. We are currently somewhere around 600 Hz, but we’re still working on it. Given the limit of 155 MBits/s per SEB due to the ATM NIC, the Level 1 limit is set by the DC - at 2.5% occ, event size is 26.3 kB, so 15 MB/26.3 kB => max rate of 1140 Hz. If we go to minimal FEM headers, the DC size goes down to 21.8kB, or a max rate of ~1400 Hz. If we want coherent peripheral, we’d need to split the DC granules. Still a lot of work to do for p-p running, and none of it seems certain: minimize headers, drop packets, level-1 b oards…