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Data Acquisition

at a particle physics experiments. Data Acquisition. Sergey Mikirtytchiants, IKP FZJ. GGSWBS'12, Batumi Aug. 13-17. Outline. How to study interaction of an elementary particles? Particle identification and detectors. Digitizing of detector signals. Data acquisition system.

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Data Acquisition

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  1. at a particle physics experiments Data Acquisition Sergey Mikirtytchiants, IKP FZJ GGSWBS'12, Batumi Aug. 13-17

  2. Outline. • How to study interaction of an elementary particles? • Particleidentification and detectors. • Digitizing of detector signals. • Data acquisition system. • Trigger. • Example: Strange particle production in p-p collision. • Summary.

  3. How to study interaction of an elementary particles? ejectiles interaction incident ? target Reconstruct ejectiles, unobservable directly (missing mass) Kinematics (conservation law) Example: Strange particle production in proton-proton collision stotal ~ mb

  4. What is needed to carry out such study? • Accelerator • Target • Setup to detect and identify ejectiles Incident particle beam Particle: p; Energy: 2 GeV; Intencity: nb = 10121/s Particle: p; Dencity (thikness): nt = 10141/cm2 Luminosity: L = nt nb fb= 1014 x 1012 x 106 = 1032 cm-2 s-1 Event rate: R = stotalL = 10-29 cm-2 x 1032 cm-2 s-1 = 103s-1

  5. Particleidentification. Means the type of the particle (mass) and its momentum (P)Charged particles • Energy losses in matter • Cherenkov radiation • Bending of trajectory in magnetic field B • Time of flight E/x [ MeV/cm ]  (velocity) R=P/eB R=P/eB → P=f(x,y) tof = (t1-t0)/L [ ns/m ]

  6. Detectors. • Temporal resolution TOF • Spatial resolution Tracking • Energy resolution E, E • Dead time MW Chambers Prop. DriftScintillators Organic Inorganic Silicon Strip Pixel DG - Detector Geometry

  7. Digitizing (1). t tj t0 t1 tn start stop stop_m t0  t Charge Q Amplitude A Tclk 0 m aj Flash ADC 0 < j < m • TDC — Time Digital Converters • ADC — Analog Digital Converters Resolution - s [ns/bin]Range (full scale) – n-bits Nonlinearity - s = f(bin)Conversion time ~ ms Multihit TDC: m times Resolution - s [AV / bin]Range (full scale) – n-bitsNonlinearity - s = f(bin) Conversion time ~ ms m times

  8. Digitizing (2). MSB n MSB n 2 0 LSB 1 Data 1 0 1 1 0/1 0/1 0/1 0/1 • Registers • Scalers Coordinate detector (MWPC) Latch Each input signal increments the counter content by ONE Data = Data + 1 Double pulse resolution ~ 5...10 ns Max. speed ~ 20...200 MHz Capacity – 24...32 bits

  9. Data acquisition. PreAmpAmplifierDiscriminator …. ADCTDCREGSCL …. CAMACVMELVDS BusPCI Bus ….. ….. D1...Dn HV, LVGas,Cooling …. TriggerLevel 1 DATAstorage. • Common hardware structure • DATA stucture Detectors Digitizers Digitizers Interface Computer Front endelectronics Amount of DATA = <event size> x Accepted Trigger rate upto 100 MB/s !!!→ Zero data suppression → Selective Trigger Header (Run number, comment) {Event number; Time stamp; Source ID (ADC_1); {Data_ADC_1}; Source ID (TDC_1); {Data_TDC_1}; …........ End of event}; // event size {Next Event};

  10. Data acquisition. …. …. t0 , gate D1...Dn ….. ….. Trigger DATAstorage. For a unit of time: Full Dead time: Full Live time: DT DT Efficienty e of Data taking: • Common hardware structure • Dead time: After each accepted event DAQ is insensitive during a period t (DT) Detectors Digitizers Digitizers Interface Computer Front endelectronics nacc nacc DT BUSY ninp ninp nacc Average DT: <t > = 100 ms Efficiency e increasing by → Clusters ( less DT )→ Selective Trigger (less ninp )

  11. Data acquisition. cluster_1 …. …. t0 , gate D1 ….. ….. …. cluster_n Dn clusterevent builder DATAstorage. • Cluster structure • Advantages: a) Flexibility; b) High performance … Digitizers Interface Computer Detectors Front endelectronics nacc clustersynchro Trigger DAQBUSY DT ninp nacc

  12. Trigger. Aim: digitize and store data only in case of the certain conditions.Goal: reduce data losses and amount of stored data by ignoring of undesirable background events. • Level 1: very fast, but pure rejection • Level 2: stronger rejection, but slower ; needs data buffering • Higher trigger levels: more selective and slower • Hardware logic based on • Timing (restricted time window for TOF) • DE,E (cut p by setting of high threshold • Spatial selection by coincidence of certain SC's Dedicated digital signal processing based on special algoriythm (rough track reconstruction) Software based, can be applied ofline.

  13. Example. Strange particle production in p-p collision near to threshold Tp 1.8 – 2.2 GeV stotal Aim of experiment: Searching for pair:(K+p), (K++) Триггер:K+

  14. COoler SYnchrotron COSY. • p, d (un)polarized • momentum 0.3...3.7 GeV/c • intencity upto 1010 1/s Cooling electron: ~0.3 GeV/c stochastic: >1.5 GeV/c

  15. Spectrometer ANKE. 1 m STT Target ND (SC, MWPC) FD (SC, MWPC, MWDC) p,d H2,D2 cluster jet PD (SC, MWPC) K+,p +

  16. Frontend electronics of Scintillator Detectors. FanOut PMT_up CFD Sc HV_upPSHV_dn Meantimer CFD FanOut PMT_dn Front endelectronics PdSo14_Tup → QDC Y= L L=1mt=7 ns/mDt = 2Lt = 14 ns PdSo14_Tup → TDC, Scaler PdSo14_MT → TDC, Scaler , Trigger PdSo14_Tdn → TDC, Scaler Y= 0 PdSo14_Tdn → QDC

  17. Raw spectra. criterion efficiency of registration K+ BG Valid Sa 1.0 0.25 Source: TDC's TOF spectra between So13 and Sa1...23 Source: QDC's Energy loss spectra So13 and Sa1...23

  18. Time of flight (TOF). criterion efficiency of registration K+ BG TOF onl 1.0 0.11 TOF ofl 0.99 0.29 online offline TOF spectrum of So13 (& Sa1...23) Energy loss spectrum of So13

  19. 'Delayed Veto'. Delayed Veto spectrum of Tel13 online offline Dt-So & del_1 Dt-Ve & del_2 & & criterion efficiency of registration K+ BG Del_Ve onl ~0.2 ~ 5x10 -3 Del_Ve ofl 0.2 < 10 -3 del_n Valid Sa So Ve del_Ve Trigger TOF trigger unit

  20. Vertical angle. criterion efficiency of registration K+ BG Vertical angle 0.99 0.11 Vertical angles after K+-cuts in SC of Tel.13

  21. Summary of Criteria criterion efficiency of registration K+ BG Valid Sa 1.0 0.25 TOF 1.0 0.11 Del_Ve ~0.2 ~ 5x10 -3 TOF 0.99 0.29 Del_Ve 0.2 < 10 -3 Vertical angle 0.99 0.11 All 0.2 < 3.5x10 -6 Trigger rate suppresion 10 — 30 times 50 — 200 times Right Criteria allows to study rare processes !

  22. Result: total cross section PLB 652, 245-249 (2007) Tp =2.16 GeV

  23. Summary. For effictiveness data taking it is needed: • Data Acquisition : Small dead time • Cluster stucture • Flexibility • Trigger: Compromise of a criteria Cut Background Do not cut effect • Online Data Handling: • To control trigger criteria setting and thus be sure in quality of taken data

  24. Questions. • Detectors: 1. Which types of detectors can be used for tracking? • 2. Which detectors have fast time response? • Digitizers: 1. Types and main characteristics of a digitizers? • Data Acquisition : 1. What is important for effictiveness data taking? • 2. Ways how to increase the efficiency of data taking? • Trigger: 1. What is aim of trigger? 2. Which criteria could be used on the first level of trigger?

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