# tglied der HelmholtzGemeinschaft Data Acquisition at a particle

• Slides: 24

tglied der Helmholtz-Gemeinschaft Data Acquisition at a particle physics experiments 13. 8. 12 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. Trigger. Example: Strange particle production in p-p collision. Summary. 13. 8. 12 Slide 2

How to study interaction of an elementary particles? incident interaction ejectiles ? target Kinematics (conservation law) Reconstruct ejectiles, unobservable directly (missing mass) Example: Strange particle production in proton-proton collision stotal ~ mb 13. 8. 12 Slide 3

What is needed to carry out such study? Accelerator Incident particle beam Particle: p; Energy: 2 Ge. V; Intencity: nb = 1012 1/s Target Particle: p; Dencity (thikness): nt = 1014 1/cm 2 Luminosity: L = nt nb fb= 1014 x 1012 x 106 = 1032 cm-2 s-1 Event rate: R = stotal L = 10 -29 cm-2 x 1032 cm-2 s-1 = 103 s-1 Setup to detect and identify ejectiles 13. 8. 12 Slide 4

Particle identification. Means the type of the particle (mass) and its momentum (P) Charged particles Energy losses in matter E/ x [ Me. V/cm ] Cherenkov radiation (velocity) Bending of trajectory in magnetic field B R=P/e. B Time of flight 13. 8. 12 → P=f(x, y) tof = (t 1 -t 0)/L [ ns/m ] Slide 5

Detectors. Temporal resolution TOF Spatial resolution Tracking Energy resolution E, E Dead time 2 ns 0. 1 mm ------ 0. 1 ns 10 ns 1 ns DG 10 m 1 Me. V 0. 2 s 0. 1 s 10 ns DG ------ 0. 1 Me. V 1 s 100 s MW Chambers Prop. Drift Scintillators Organic Inorganic Silicon Strip Pixel DG - Detector Geometry 13. 8. 12 Slide 6

Digitizing (1). TDC — Time Digital Converters Resolution - s [ns / bin] Range (full scale) – n-bits Nonlinearity - s = f(bin) Conversion time ~ ms t 0 start tj t tn stop_m Multihit TDC: m times ADC — Analog Digital Converters Resolution - s [AV / bin] Range (full scale) – n-bits Nonlinearity - s = f(bin) Conversion time ~ ms t 1 stop t 0 t Charge Q Amplitude A Tclk 0 Flash ADC aj m 0<j<m m times 13. 8. 12 Slide 7

Digitizing (2). Registers Coordinate detector (MWPC) MSB n Data 1 2 1 0 LSB 0 1 1 Latch 0/1 0/1 Scalers 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 13. 8. 12 Slide 8

Data acquisition. Common hardware structure Detectors Front end electronics D 1. . . Dn Pre. Amplifier Discriminator …. Digitizers HV, LV Gas, Cooling …. DATA stucture 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}; 13. 8. 12 ADC TDC REG SCL …. Trigger Level 1 Interface Computer CAMAC VME LVDS Bus PCI Bus …. . DATA storage. Amount of DATA = <event size> x Accepted Trigger rate upto 100 MB/s !!! → Zero data suppression → Selective Trigger Slide 9

Data acquisition. Common hardware structure Detectors Front end electronics D 1. . . Dn …. Digitizers Interface …. Computer …. . t 0 , gate nacc Trigger ninp DT nacc BUSY DATA storage. Dead time: After each accepted event DAQ is insensitive during a period t For a unit of time: Full Dead time: Full Live time: Efficienty e of Data taking: 13. 8. 12 ninp DT (DT) nacc Average DT: <t > = 100 ms <ninp> e 103 1/s 0. 91 104 1/s 0. 50 105 1/s 0. 09 106 1/s 0. 01 Efficiency e increasing by → Clusters ( less DT ) → Selective Trigger (less ninp ) Slide 10

Data acquisition. Cluster structure Detectors Front end electronics D 1 …. Dn Digitizers Interface Computer cluster_1 …. . t 0 , gate cluster_n …. Trigger nacc DT ninp nacc DAQ BUSY DATA storage. cluster synchro cluster event builder Advantages: a) Flexibility; b) High performance … 13. 8. 12 Slide 11

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 Hardware logic based on Timing (restricted time window for TOF) E, E (cut by setting of high threshold Spatial selection by coincidence of certain SC's Level 2: stronger rejection, but slower ; needs data buffering Dedicated digital signal processing based on special algoriythm (rough track reconstruction) Higher trigger levels: more selective and slower Software based, can be applied ofline. 13. 8. 12 Slide 12

Example. Strange particle production in p-p collision near to threshold Tp 1. 8 – 2. 2 Ge. V Aim of experiment: stotal Searching for pair: (K+p), (K+ +) Триггер: K+ 13. 8. 12 Slide 13

COoler SYnchrotron COSY. p, d (un)polarized momentum 0. 3. 7 Ge. V/c intencity upto 1010 1/s Cooling electron: ~0. 3 Ge. V/c stochastic: >1. 5 Ge. V/c 13. 8. 12 Slide 14

Spectrometer ANKE. 1 m STT ND (SC, MWPC) FD (SC, MWPC, MWDC) Target H 2, D 2 cluster jet 13. 8. 12 p, d PD (SC, MWPC) K+ , + Slide 15

Frontend electronics of Scintillator Detectors. Front end electronics Fan Out PMT_up Y= L L=1 m t =7 ns/m Dt = 2 Lt = 14 ns Pd. So 14_Tup → QDC CFD Pd. So 14_Tup → TDC, Scaler HV_up Sc Mean timer PS Pd. So 14_MT → TDC, Scaler , Trigger HV_dn Pd. So 14_Tdn → TDC, Scaler CFD Y= 0 PMT_dn 13. 8. 12 Fan Out Pd. So 14_Tdn → QDC Slide 16

Raw spectra. Source: TDC's TOF spectra between So 13 and Sa 1. . . 23 criterion Valid Sa 13. 8. 12 Source: QDC's Energy loss spectra So 13 and Sa 1. . . 23 efficiency of registration K+ BG 1. 0 0. 25 Slide 17

Time of flight (TOF). online offline TOF spectrum of So 13 (& Sa 1. . . 23) criterion TOF onl TOF ofl 13. 8. 12 Energy loss spectrum of So 13 efficiency of registration K+ BG 1. 0 0. 11 0. 99 0. 29 Slide 18

'Delayed Veto'. Delayed Veto spectrum of Tel 13 online Valid Sa So Dt-So del_1 & del_2 & del_n & TOF trigger unit 13. 8. 12 offline Ve Dt-Ve & del_Ve Trigger criterion Del_Ve onl Del_Ve ofl efficiency of registration K+ BG ~0. 2 ~ 5 x 10 -3 0. 2 < 10 -3 Slide 19

Vertical angle. Vertical angles after K+-cuts in SC of Tel. 13 criterion Vertical angle 13. 8. 12 efficiency of registration K+ BG 0. 99 0. 11 Slide 20

Summary of Criteria criterion Valid Sa TOF Del_Ve efficiency of registration K+ BG 1. 0 0. 25 1. 0 0. 11 ~0. 2 ~ 5 x 10 -3 TOF Del_Ve Vertical angle 0. 99 0. 29 < 10 -3 0. 11 All 0. 2 < 3. 5 x 10 -6 Trigger rate suppresion 10 — 30 times 50 — 200 times Right Criteria allows to study rare processes ! 13. 8. 12 Slide 21

Result: total cross section PLB 652, 245 -249 (2007) Tp =2. 16 Ge. V 13. 8. 12 Slide 22

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 13. 8. 12 Slide 23

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? 13. 8. 12 Slide 24