13.8.12

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Data Acquisitionat a particle physics experiments

Sergey Mikirtytchiants, IKP FZJ

GGSWBS'12, Batumi Aug. 13-17

13.8.12 Slide 2

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 3

How to study interaction of an elementary particles?

p 1 ,m1

incident

targetpT ,mT

interaction ejectilesp 1 ,m1

p 2 , m 2

p21 ,m2

1

p n , m n

p22 ,m2

2?

Kinematics(conservation law)

Reconstruct ejectiles,unobservable directly(missing mass)

Example:

Strange particle production in proton-proton collisionpp → K + p Λ , Λ→π + p , BR=0.639

pp → K + p Σ 0 , Σ 0→γ Λ , BR=1.00

pp →K + n Σ + , Σ + → p π 0 , BR=0.516→π + n , BR=0.483

total

~ b

13.8.12 Slide 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 = 1012 1/s

Particle: p; Dencity (thikness): nt = 1014 1/cm2

Luminosity: L = nt n

b f

b= 1014 x 1012 x 106 = 1032 cm-2 s-1

Event rate: R = total

L = 10-29 cm-2 x 1032 cm-2 s-1 = 103s-1

13.8.12 Slide 5

Particle identification.

Energy losses in matter

Cherenkov radiation

Bending of trajectory in magnetic field B

Time of flight

Means the type of the particle (mass) and its momentum (P)Charged particles

(π + , π − , K + , K− , ... , p , n , ...)

E/x [ MeV/cm ]

(velocity)

R=P/eBR=P/eB → P=f(x,y)

tof = (t1-t

0)/L [ ns/m ]

13.8.12 Slide 6

Detectors.

Temporal resolution TOF Spatial resolution Tracking Energy resolution E, E Dead time

MW ChambersProp.

DriftScintillators Organic Inorganic Silicon

StripPixel

2 ns 2 ns 0.1 ns 10 ns 1 ns ------

0.1mm 0.1mm DG DG 10 m 1 m

------ ------ 1 MeV 0.1MeV 0.1MeV 0.1MeV

0.2 s 0.1 s 10 ns 1 s 10 s 100 s

DG - Detector Geometry

13.8.12 Slide 7

Digitizing (1).

TDC — Time Digital Converters

ADC — Analog Digital Converters

Resolution - [ns/bin]Range (full scale) – n-bits Nonlinearity - = f(bin)Conversion time ~ s

Resolution - [AV / bin]Range (full scale) – n-bitsNonlinearity - = f(bin) Conversion time ~ s

Amplitude A N i=k A⋅Ai

Flash ADC aj

N ij=k A⋅ai

j

0 m T

clk

0 < j < m

Charge Q N i=kQ⋅∫0

t

I (t)dt

t

t0

start t

0

stop t

1 t

stop_m t

n t

j

N i = k T ⋅(t 1−t0)N ij=k T ⋅(t j−t 0)Multihit TDC: m times

m times

13.8.12 Slide 8

Digitizing (2).

Registers

Scalers

Coordinate detector (MWPC)

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

0/1

0/10/10/1

1 0 1 1

Latch

Data MSB n MSB n 0 LSB 2 1

13.8.12 Slide 9

Data acquisition.

Common hardware structure

DATA stucture

Detectors Front endelectronics

Digitizers Digitizers Interface Computer

CAMACVME

LVDS BusPCI Bus

…..

ADCTDCREGSCL ….

PreAmpAmplifier

Discriminator ….

D1...Dn

HV, LVGas,

Cooling ….

TriggerLevel 1

…..

DATAstorage.

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};

Amount of DATA = <event size> x Accepted Trigger rate upto 100 MB/s !!!

→ Zero data suppression → Selective Trigger

13.8.12 Slide 10

Data acquisition.

Common hardware structure

Dead time: After each accepted event DAQ is insensitive during a period (DT)

Detectors Front endelectronics

Digitizers Digitizers Interface Computer

….. …. t

0 , gate

….

Trigger

…..

DATAstorage.

D1...Dn

DT ninp

nacc

ninp

Full Dead time: Full Live time:

nacc⋅1−nacc⋅

For a unit of time:

Efficienty of Data taking:

naccninp

= 11+ninp⋅

= ninp⋅(1− ninp⋅ )

nacc

Average DT: <> = 100

s<n

inp>

103 1/s 0.91

104 1/s 0.50

105 1/s 0.09

106 1/s 0.01

Efficiency increasing by

→ Clusters ( less DT ) → Selective Trigger (less n

inp )

DT

DT BUSY

nacc

13.8.12 Slide 11

Data acquisition.

Cluster structure

Advantages: a) Flexibility; b) High performance …

Detectors Front endelectronics

Digitizers Interface Computer

….. …. …..

DATAstorage.

D1

nacc

cluster_1

Triggern

inp

DT DAQBUSY

nacc

…. t

0 , gate

…. Dn cluster_n

clustersynchro

clusterevent builder

13.8.12 Slide 12

Trigger.

Level 1: very fast, but pure rejection

Level 2: stronger rejection, but slower ; needs data buffering

Higher trigger levels: more selective and slower

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.

Hardware logic based on Timing (restricted time window for TOF)E,E (cut π 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.

13.8.12 Slide 13

Example.Strange particle production in p-p collision near to threshold T

p 1.8 – 2.2 GeV

pp → K + p Λ , Λ→π + p , BR=0.639

pp → K + p Σ 0 , Σ 0→γ Λ , BR=1.00

pp →K + n Σ + , Σ + → p π 0 , BR=0.516→π + n , BR=0.483

total

Searching for pair: (K+p), (K+π+)

Триггер: K+

Aim of experiment:

13.8.12 Slide 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

13.8.12 Slide 15

Spectrometer ANKE.

STT

Target

1 m

ND (SC, MWPC)

H2,D

2

cluster jet

FD (SC, MWPC, MWDC)

PD (SC, MWPC) K+,π

p, d

13.8.12 Slide 16

Frontend electronics of Scintillator Detectors.

Y= 0

Front endelectronics

Sc

PMT_up

PMT_dn

HV_up

PS

HV_dn

FanOut

CFD

Meantimer

FanOut

CFD

PdSo14_Tup → TDC, Scaler

PdSo14_MT → TDC, Scaler , Trigger

PdSo14_Tdn → TDC, Scaler

PdSo14_Tdn → QDC

PdSo14_Tup → QDC

Y= L

L=1m =7 ns/mt = 2L = 14 ns

13.8.12 Slide 17

Raw spectra.

Source: TDC'sTOF spectra between So13 and Sa1...23

Source: QDC'sEnergy loss spectra So13 and Sa1...23

criterion efficiency of registration K+ BGValid Sa 1.0 0.25

13.8.12 Slide 18

Time of flight (TOF).

TOF spectrum of So13 (& Sa1...23)

criterion efficiency of registration K+ BGTOF onl 1.0 0.11TOF ofl 0.99 0.29

online

offline

Energy loss spectrum of So13

13.8.12 Slide 19

'Delayed Veto'.

criterion efficiency of registration K+ BGDel_Ve onl ~0.2 ~ 5x10 -3

Del_Ve ofl 0.2 < 10 -3

offline online

Delayed Veto spectrum of Tel13

&

t-So

&del_1

&del_2

&del_n

Valid Sa

TOF triggerunit

So

t-Ve

del_Ve Trigger

Ve

K+→+ν ; (BR=0.63)

K+=12.4 ns

13.8.12 Slide 20

Vertical angle.

criterion efficiency of registration K+ BGVertical angle 0.99 0.11

Vertical angles after K+-cuts in SC of Tel.13

13.8.12 Slide 21

Summary of Criteria

criterion efficiency of registration K+ BGValid Sa 1.0 0.25TOF 1.0 0.11Del_Ve ~0.2 ~ 5x10 -3

TOF 0.99 0.29Del_Ve 0.2 < 10 -3

Vertical angle 0.99 0.11

All 0.2 < 3.5x10 -6

Trigger ratesuppresion

10 — 30 times

50 — 200 times

Right Criteria allows to study rare processes !

13.8.12 Slide 22

Result: total cross section

Σ nKpp

PLB 652, 245-249 (2007)

)( Σ

Tp =2.16 GeV

13.8.12 Slide 23

Summary.

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

For effictiveness data taking it is needed:

13.8.12 Slide 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?