Performance Evaluation of Trigger Algorithm for MACE Gamma Ray Telescope

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Performance evaluation of trigger algorithm for the MACE telescope Kuldeep Yadav BARC Mumbai February 20, 2013 (On behalf of: N. Bhatt, N. Chouhan, S.S. Sikder, A. Behere, C.K. Pithawa, A.K. Tickoo, R.C. Rannot, S. Bhattacharyya, A.K. Mitra, R. Koul ) Kuldeep Yadav (BARC, Mumbai) ASI-2013 February 20, 2013 1 / 16

description

Major Atmospheric Cherenkov Experiment: The state of the art Gamma Ray Telescope being built by BARC

Transcript of Performance Evaluation of Trigger Algorithm for MACE Gamma Ray Telescope

Performance evaluation of trigger algorithm forthe MACE telescope

Kuldeep Yadav

BARCMumbai

February 20, 2013

(On behalf of: N. Bhatt, N. Chouhan, S.S. Sikder, A. Behere, C.K. Pithawa, A.K. Tickoo, R.C.

Rannot, S. Bhattacharyya, A.K. Mitra, R. Koul )

Kuldeep Yadav (BARC, Mumbai) ASI-2013 February 20, 2013 1 / 16

Detection technique for very high energy γ-rays

Eγ < 100 GeV direct observations onsatellites

Eγ > 20 GeV indiret observations viaextensive air showers (EAS)

> 99% air showers produced in theatmophere are isotropic CR

Typically γ-ray : CR : : 1 : 103-104

Gamma-ray sources can be detectedIdentify a single photon event from thesea of background event (shower shape,muon contents)They emit so many photons that thenumber of particles from this directionstands out of the background (excess ofevents from certain sky positions)

Cherenkov light from chargedsecondaries can reach the ground withtight time structure and maintainingdirection of primary

Kuldeep Yadav (BARC, Mumbai) ASI-2013 February 20, 2013 2 / 16

Detection of atmospheric Cherenkov radiation

Purpose of detection of an EASexperimentally: Determine the type ofparticle (though difficult) andproperties of the primary particle e.g.direction, energy and chemicalcomposition in case of CR

IACT: most successful

Characteristic features ofCherenkov pulse:facilitate its detection in the presence of NSB

Narrow pulse width (∼ 5 ns)

Limited angular size (< 1) on the ground

Nature of its photon spectrum i.e.Cherenkov light peaks at shortwavelength (blue/UV) whereas NSBpeaks at longer wavelength

Example

A telescope with 1 field of view and 10 nstrigger formation time would receive∼ 5 photons/m2 from the NSB while a muchhigher expected value of ∼ 65 photons/m2 froma 1 TeV γ-ray shower. Thus, a 1 TeV showershould be detectable above NSB with atelescope having 1 m2 mirror area.

Kuldeep Yadav (BARC, Mumbai) ASI-2013 February 20, 2013 3 / 16

Bias Curve

Bias curve obtained from a simpledetector has two components

Both components can be fitted withpower law

Exponent of hard component is ≈ thatof CR spectrum

Kuldeep Yadav (BARC, Mumbai) ASI-2013 February 20, 2013 4 / 16

Trigger threshold of the telescope

The signal due to Cherenkov photons (pe)S = ργ A R ηpmt = yγ E A R ηpmt

where ηpmt : quantum efficiency of the PMT

The noise level in terms of fluctuationsN =

φLONS Ω A R ηpmt τNote: in actual case the wavelength dependence of both Cherenkov and LONS production

and collection should also we considered

The energy threshold: is the minimum γ-ray energy for which(S/N) is sufficient to adequately trigger the telescope. Thesmallest detectable light pulse is therefore inversely proportionalto S/N, i.e.

Eth ∝ (1/yγ)√

φLONS Ω τA R ηpmt

Kuldeep Yadav (BARC, Mumbai) ASI-2013 February 20, 2013 5 / 16

MACE telescope

Location: Hanle, Ladakh(32.7N, 79 E, 4200m asl)

Number of Photometric Nights:∼ 190/yr

Diameter: 21 m

Focal Distance: 25, m

Light collector configuration:Paraboloid with graded FL

Panel Size: 984 mm × 984 mm

Number of Panels: 352, Number ofFacets: ∼ 1500

Total light Collector Area: 337 m2

PSF: R95 at 0∼ 15 mm

R95 at 1∼ 43 mm

Telescope weight: ∼ 150 T

Kuldeep Yadav (BARC, Mumbai) ASI-2013 February 20, 2013 6 / 16

MACE camera

Integrated Camera (all signalprocessing instrumentation housedwithin the camera structure of2mx2mx1.2m size)

Temperature control of the cameraduring operation and standbycondition.

Conventional CDC/GHz Sampling

Kuldeep Yadav (BARC, Mumbai) ASI-2013 February 20, 2013 7 / 16

Trigger region of MACE camera

16 channel CIM module

Total PMTs: 1088 (68 CIM)

PMTs in the trigger region: 576 (36

CIM)

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Implementation of trigger algorithm

SLT hardware

Two level trigger generation

FLT: within the CIM

SLT: sytem level trigger

Kuldeep Yadav (BARC, Mumbai) ASI-2013 February 20, 2013 9 / 16

Trigger configuration 4NN tight cluster

Table: Number of combinationsTrigger Mode Desired desired + undesired

Due to implimentationFULL 36 × 21 36 × 21N+N 240 6588S+W 210 5582

& +W+S 210 5612

N+2W – –4W – –

Kuldeep Yadav (BARC, Mumbai) ASI-2013 February 20, 2013 10 / 16

Estimates of chance trigger rates

SCR ( kHz)

100 1000

Ra

te (

Hz)

10-1

100

101

102

103

104

(1)

(2)

(3)

(4)

(1) Chance 4NN --full alone ( 5ns )

(2) Chance 4NN -- (N+N) alone ( 5ns , 10ns)

(3) Chance 4NN -- (S+W: W+S) alone ( 5ns , 10ns)

(4) Chance 4NN -- total (1)+(2)+(3)

(5) Rate at which trigger patterns need to be validated

Fu

ll

alo

ne

(4

9.0

5 %

pa

tte

rns

)

Fu

ll

+N

N+

SW

+W

S

(9

1.8

8 %

pa

tte

rns

)(5)

Chance rate : 20 Hz

Chance rate due to desired

combinations

1 Full triggers:36 × 21 × 4 × R4τ3

flt2 N+N triggers: 240 × 2 ×

(2R2τflt )(2R2τflt )τslt3 W+S triggers:

420 × 2 × (3R3τ2flt )(R)τslt

Total chance rate due to

implementation

1 N+N triggers:6588 × 2 ×

(2R2τflt )(2R2τflt )τslt2 W+S triggers: 11194 ×

2 × (3R3τ2flt )(R)τslt

TRIGGER INFORMATION IN TWOPHASES !

Kuldeep Yadav (BARC, Mumbai) ASI-2013 February 20, 2013 11 / 16

Effective area

Biggest advantage of groundbased Cherenkov telescopesLarge effective collection area

Satellite exp.: Geometrical areaCherenkov tel.: Cherekov pool(120 m radius)

Large collextion area isessential due to power lawnature of sources

Effective area for point γ-raysourcesAeff (E) = 2π

R

0 R×p(R, E)dR

Discretized form Aeff (E) =P

0 π(R2i − R2

i−1)p(Ri , E)

p(R,E): Probability of trigger

10000

100000

100

Effe

ctiv

e A

rea

(m2 )

Energy (GeV)

5pe-4NN-FullCascade7pe-4NN-FullCascade

7pe-4NN-Full10pe-4NN-FullCascade

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Trigger Efficiency

Trigger Probability , p(R, E) =number of triggered showers

Total number of showers generated

depends on Cherenkovphoton density, trigger FOV,trigger multiplicity and singlepixel threshold

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Trigger rates for Gamma-ray at various single pixelthresholds

Differential rate: Number of particles (E and E+dE)

trigger the telescope per unit time

0.01

0.1

1

10 100

Diff

. Rat

e (G

amm

a-ra

y/se

c)

Energy (GeV)

5pe-4NN-FullCascade7pe-4NN-FullCascade

7pe-4NN-Full10pe-4NN-FullCascade

D(E)dE = Aeff × N(E)dEPeak of differential trigger ratedetermines the energy thresholdNγ (e) = 2.79 × 10−7( E

GeV )−2.59

ph m−2 s−1 GeV−1

Trigger Threshold IntegralMode Energy rate

(GeV) (Hz)

5peFC 16 8.0

7peFC 21 3.4

7peF 23 2.2

10peFC 30 1.5

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Simulation results: Effective area and trigger ratesEffective area

Particle Threshold Integraltype Energy rate

(GeV) (Hz)

Gamma-rays 18.78 11.86

Electrons 27.27 37.13

Differential rates

Particle Threshold Integraltpye Energy rate

(GeV) (Hz)Protons 127.1 818.8Alpha 660.8 137.7Total 1000.49rate

Kuldeep Yadav (BARC, Mumbai) ASI-2013 February 20, 2013 15 / 16

Summary

In the actual implementation of 4NN tight cluster trigger schemeprovides an integral trigger rate for gamma-rays which is less thanobtained from MC simulation of the MACE telescope. Whichmeans the total trigger rate should not exceed the estimated dataacquisition rate of cosmic-ray (∼ 1 kHz)

Data acquisition of the MACE telescope is capable of handling asustained trigger rate of 1 kHz.

Thank you

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