1. 04.02.2015V.Duk, INFN Perugia1 CHOD TDAQ status and rates Viacheslav Duk, INFN Perugia On behalf of the CHOD working group

2. 04.02.2015V.Duk, INFN Perugia Outlook 2 1.Data used for the analysis 2.Detector rates 3.Rates per slab 4.Conclusions

3. 04.02.2015V.Duk, INFN Perugia Data used for the analysis 3 Software: NA62Reconstruction r400 NA62Analysis r400 Data: Run 1348, 26 bursts (first file produced by Monica) Beam intensity ~6% of the nominal Trigger: πνν + Q1/1000 (CHOD always included) Total event number: N events = 1206398 Selection criteria: Hits with at least leading (leading only or leading+trailing) Signal region: 1600ns < hit_time < 1700ns (100ns interval out of 400ns)

4. 04.02.2015V.Duk, INFN Perugia Time distribution 4  Gap on the left: probably dead time of the PM+FE system  Maximum at ~1640ns  Reasonable time window: 100ns (4 time frames)  Selected region for signal studies: 1600 – 1700 ns (signal region)  Region for halo/pile-up studies: 1850 – 1950 ns (off-peak region) zoom for the signal region

5. 04.02.2015V.Duk, INFN Perugia N hits distribution 5 Before cut on time: Mean ~6.3 Signal region: Mean ~4.6 Off-peak region: Mean ~0.6 Off-peak region: ~1M events with 0 hits ~0.2M events with >0 hits ~ Mean * 1.2 / 0.2 ~ 3.6 Hit rate contributions Signal region: Signal Pile-up + halo Off-peak region: Pile-up + halo Signal: 4.0 hits/event Pile-up + halo: 0.6 hits/event NB Hits from decays are always called pile-up Pile-up and halo contribute as additional hits

6. 04.02.2015V.Duk, INFN Perugia Detector rates (low I) 6 Strategy:  Estimate hit number per event for signal and halo for low intensity  Estimate hit rates for signal, pile-up, halo for low intensity  Estimate hit rates for the nominal intensity Signal: 4.0 hits per event (see the previous slide) Pile-up: Intensity: 6% * I 0 (I 0 - nominal intensity) Event rate: ~ 0.06 * 10 MHz = 0.6 MHz Average event number in 100ns interval: λ = 0.6MHz * 100ns = 0.06 Probability to have one event in a 100ns interval (Poisson): P = exp(- λ) * λ ~ 0.056 Pile-up contribution (hit number normalized on N events ) to any 100ns region: 4.0 * 0.056 = 0.224 (~ 37% wrt 0.6) Halo contribution (hit number normalized on N events ) to any 100ns region: 0.6 – 0.224 = 0.376 (~73% wrt 0.6)

7. 04.02.2015V.Duk, INFN Perugia Detector rates (low I) 7 Off-peak region average hit number per event: ~ 3.6 (see slide 5) = 0.37 * + 0.73* ~4.0 (the same as for the signal) 3.6 = 0.37 * 4.0 + 0.73 * ~ 2.9

8. 04.02.2015V.Duk, INFN Perugia Detector rates (low I) 8 Pile-up contribution wrt signal (in terms of hit number): 0.056 Halo contribution wrt signal (in terms of hit number): 0.376 / 4.0 ~ 0.094 Pile-up contribution wrt the total hit rate (in terms of hit number): 0.224 / 4.6 ~ 0.049 Halo contribution wrt the total hit rate (in terms of hit number): 0.376 / 4.6 ~ 0.082

9. 04.02.2015V.Duk, INFN Perugia Detector rates (low I) 9 Detector rates in 2014 (run 1348): Signal event rate = 0.06 * 10MHz = 0.6MHz Signal hit rate (in the 100ns time interval) = 4.0 * 0.6MHz = 2.4 MHz Pile-up hit rate (in the 100ns time interval) = 0.056 * 2.4 MHz ~ 0.13 MHz Halo hit rate (in the 100ns time interval) = 0.094 * 2.4 MHz ~ 0.23 MHz Total hit rate (in the 100ns time interval) = 2.4MHz + 0.13MHz + 0.23MHz = 2.76 MHz NB At low rate pile-up contributes only as one extra particle, at the nominal intensity also two (or more) pile-up particles should be taken into account

10. 04.02.2015V.Duk, INFN Perugia Detector rates (nominal I) 10 Strategy: Calculate rates for different readout windows: 50ns, 75ns, 100ns Even with dt=50ns we take all leadings and almost all trailings

11. 04.02.2015V.Duk, INFN Perugia Detector rates (nominal I) 11 Extrapolation to the nominal intensity (100ns time window): Average event number in 100ns interval: λ = 10MHz * 100ns = 1 Suppose that halo contribution is the same (0.094 of the signal in terms of hit rate) Probability to have one pile-up event in a 100ns interval (Poisson): P = exp(- λ) * λ ~ 0.37 Probability to have 2 pile-up events in a 100ns interval (Poisson): P = exp(- λ) * λ 2 / 2 ~ 0.184 Probability to have 3 pile-up events in a 100ns interval (Poisson): P = exp(- λ) * λ 3 / 3! ~ 0.061 Total pile-up hit contribution: 0.37 + 0.184* 2 + 0.061*3 = 0.92 Signal hit rate (in the 100ns time interval) = 4.0 * 10MHz = 40 MHz Pile-up hit rate (in the 100ns time interval) = 0.92 * 40MHz = 36.8 MHz Halo hit rate (in the 100ns time interval) = 0.094 * 40MHz ~ 3.8 MHz Total hit rate (in the 100ns time interval) = 40MHz + 36.8MHz + 3.8MHz = 80.6 MHz 100 ns time window

12. 04.02.2015V.Duk, INFN Perugia Detector rates (nominal I) 12 Extrapolation to the nominal intensity (75ns time window): Average event number in 75ns interval: λ = 10MHz * 75ns = 0.75 Suppose that halo contribution is the same (0.094*0.75 ~ 0.07 of the signal in terms of hit rate) Probability to have one pile-up event in a 75ns interval (Poisson): P = exp(- λ) * λ ~ 0.35 Probability to have 2 pile-up events in a 75ns interval (Poisson): P = exp(- λ) * λ 2 / 2 ~ 0.133 Probability to have 3 pile-up events in a 75ns interval (Poisson): P = exp(- λ) * λ 3 / 3! ~ 0.015 Total pile-up hit contribution: 0.35 + 0.133*2 + 0.015*3 = 0.66 Signal hit rate (in the 75ns time interval) = 4.0 * 10MHz = 40 MHz Pile-up hit rate (in the 75ns time interval) = 0.66 * 40MHz = 26.4 MHz Halo hit rate (in the 75ns time interval) = 0.07 * 40MHz ~ 2.8 MHz Total hit rate (in the 75ns time interval) = 40MHz + 26.4MHz + 2.8MHz = 69.2 MHz 75 ns time window

13. 04.02.2015V.Duk, INFN Perugia Detector rates (nominal I) 13 Extrapolation to the nominal intensity (50ns time window): Average event number in 50ns interval: λ = 10MHz * 50ns = 0.5 Suppose that halo contribution is the same (0.094*0.5 = 0.047 of the signal in terms of hit rate) Probability to have one pile-up event in a 50ns interval (Poisson): P = exp(- λ) * λ ~ 0.30 Probability to have 2 pile-up events in a 50ns interval (Poisson): P = exp(- λ) * λ 2 / 2 ~ 0.076 Probability to have 3 pile-up events in a 50ns interval (Poisson): P = exp(- λ) * λ 3 / 3! ~ 0.013 Total pile-up hit contribution: 0.30 + 0.076*2 + 0.013*3 = 0.49 Signal hit rate (in the 75ns time interval) = 4.0 * 10MHz = 40 MHz Pile-up hit rate (in the 75ns time interval) = 0.49 * 40MHz = 19.6 MHz Halo hit rate (in the 75ns time interval) = 0.047 * 40MHz ~ 1.9 MHz Total hit rate (in the 75ns time interval) = 40MHz + 19.6MHz + 1.9MHz = 61.5 MHz 50 ns time window

14. 04.02.2015V.Duk, INFN Perugia Detector rates: limits 14 Current CHOD TDAQ configuration:  Both leading and trailing are written (1 hit = 2 words = 8 byte)  Two thresholds are used (see next slide)  1 TEL62, 2 TDCBs (2 PPs)  One timestamp per event First limit: data rate 1 GB/s * 80% [efficiency] * 2 cables / 8 [B/byte] = 200 Mbyte/s Second limit: raw hit rate (rate per L1_buffer/TDC/PP) 20MHz per L1 buffer, 20MHz per TDC, 80MHz per PP (NB: this rate does not depend on the trigger and roughly corresponds to 6.4μs readout window) NB For limits see the talk by Marco Sozzi at the weekly meeting on 22.01.2015

15. 04.02.2015V.Duk, INFN Perugia Two FE thresholds 15  LAV FEE: 2 thresholds  We need only low threshold (60mV)  High threshold can be set to maximal value (~280mV) to reduce the rate Pics from my talk on 10.12.2014 (slide 22): At least factor of 3 reduction between iteration 1 (145mV) and 30 (290mV) Total hit rate will be ~1.3 wrt hit rate at low threshold

16. 04.02.2015V.Duk, INFN Perugia (Data rate) limit 16 Time window50ns75ns100ns Hits/ev8911 Words/ev171923 Bytes/ev687692 Data rate, Mbyte/s687692 Data rate limit, Mbyte/s 200 Hits/ev = hit_rate / ev_rate * 1.3 (two thresholds) Words/ev = Hits/ev * 2 (leading+trailing) + 1 (timestamp) Bytes/ev = words/ev * 4 Data rate = bytes/ev * 1MHz (L0 trigger rate) Limits are respected for all time windows

17. 04.02.2015V.Duk, INFN Perugia (Rate per PP/TDC) limit 17 Max rate per PP/TDC = EOB rate * 1.3/2 (two thresholds) * 8 (intensity) = 5.2 * EOB rate Time windowPPTDC Max rate, MHz67.618.7 Limit on the rate, MHz 8020 We are close to the limit, splitting is necessary EOB counts from Jacopo Pinzino: NB Rate per PP can be lowered by simple recabling

18. 04.02.2015V.Duk, INFN Perugia Rates per slab 18 V-plane H-plane CHOD slab numbering x y

19. 04.02.2015V.Duk, INFN Perugia Multiplicity per slab 19  Most events have 1 hit per slab  Pile-up contribution at nominal intensity: even for 1 pile-up particle per event the probability to hit the same slab is low: ~ 1/64 (1.6%)

20. 04.02.2015V.Duk, INFN Perugia Rates per slab 20 Strategy:  Draw hit occupancy  Estimate max hit number per slab (max bin content)  Normalize on the event number (1.2M)  Estimate max hit rate using calculated event rate (0.6 MHz)  Recalculate for nominal intensity: factor = 1 / 0.06 ~ 16.7

21. 04.02.2015V.Duk, INFN Perugia Rates per slab 21 Max data rate (dt=100ns): 120k / 1.2M * 0.6MHz ~ 60 kHz At nominal intensity: ~1.0 MHz

22. 04.02.2015V.Duk, INFN Perugia Rates per L1 buffer 22  L1 buffer contains 8 channels (4 slabs x two thresholds)  4 consecutive slabs have < 110k (ID ~110-113) event per slab in average  16 consecutive slabs (TDC) have ~55k event per slab (in average)  Factor ~2 for the hottest L1 buffer wrt average  Max rate ~18.7MHz (per TDC) * 1/4 * 2 (factor for hot L1 buffers) ~ 9.4MHz  The limit is ~20MHz (256 words/6.4μs or 20MHz for leading+trailing) Limits are respected

23. 04.02.2015V.Duk, INFN Perugia Rate limits: summary 23 Max rate, MHzLimit, MHz L1 buffer9.420 TDC18.720 PP67.680 data92200 Plan A for CHOD TDAQ:  1 TEL62 fully dedicated for the CHOD  Splitting board to reduce rate per TDC  Increase high FE thresholds to maximal value  Reduce readout window to 50-100ns Plan B:  Kill high thresholds  Do not write trailings

24. 04.02.2015V.Duk, INFN Perugia Conclusions 24  Hit rates are estimated for CHOD slabs and the whole detector in 2014 Run (Run 1348, 26 bursts, dt = 100 ns)  Hit rates are estimated for the nominal intensity (dt=100ns, dt=75ns, dt=50ns)  For detector rates contributions from pile-up and halo particles are analyzed  Limits on data and raw hit rates are analyzed  1 TEL62 dedicated to the old CHOD needed (and seems to be enough)  Another TEL62 needed for NHOD, NewCHOD, MUV0  Splitting board is needed to reduce rate per TDC  High FE threshold should be maximal to reduce a hit rate  Time window can be from 50ns to 100ns Analysis summary: TDAQ for the full intensity:

25. 04.02.2015V.Duk, INFN Perugia conclusions 25 Hit rate, MHz2014 Run (dt=100ns) Full intensity (dt=100ns) Full intensity (dt=75ns) Full intensity (dt=50ns) Signal2.4040.0 Pile-up0.13 (4.9%)36.8 (45.7%)26.4 (38.2%)19.6 (31.9%) Halo0.23 (8.2%)3.8 (4.7%)2.8 (4.0%)1.9 (3.1%) total2.7680.669.261.5 Per slab < 0.060 < 1.0