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High-Energy Cosmic Particles —effects of SKA cost-saving measures

Justin Bray, for the High-Energy Cosmic Particles Focus Group:J. Alvarez-Muniz, J. Bray, S. Buitink, D. Butler, R. Dagkesamanskii, R. Dallier, R. Ekers, T. Ensslin,

H. Falcke, K. Gayley, N. Hashim, A. Haungs, J. Horandel, T. Huege, C. James, K. Mack, L. Martin,

R. McFadden, M. Mevius, R. Mutel, A. Nelles, J. Rautenberg, B. Revenu, O. Scholten, F. Schroeder,

R. Spencer, S. Tingay, S. ter Veen, T. Winchen, A. Zilles

Summary

Most of the cost-saving measures do not severely affect ourprojects

. . . except analogue beamforming for SKA-LOW, which might ruleout atmospheric detection of cosmic rays.

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Two techniques

Atmospheric detection

Area ∼ 1 km2

Energy & 1017 eV

Lunar detection

Area ∼ 105 km2

Energy & 1020 eV

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SKA-LOW

Commonalities

Atmospheric signal path

core stations particledetectors

antennabuffers

data trigger

storagemetadata

I short (∼nanosec) pulse

I buffer/trigger approach

I custom experiment

Lunar signal path

core stations remote stations

stationbeamforming

stationbeamforming

pulsarbeamformer

stationbuffers

triggeringunit

trigger

metadata storage

data

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Atmospheric signal path

core stations particledetectors

antennabuffers

data trigger

storagemetadata

Data rate (core): 140 TB/s

Triggers:

I duration: 50 µs

I volume: 7 GB

I rate: 1/min

I data rate: 120 MB/s

Aim for commensality.

H. Schoorlemmer & K.D. de Vries

Radio: high precision

Particles: reliable trigger

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I ∼ 150 detectors

I two inputs each

backend ≈ one station(0.2% of SKA-LOW)

Most common particle detectors:scintillation detectors.

scintillator

photodetectorparticletrack

photons

Designs exist, but will needmodification.

Work under way in Manchester.

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Our starting point

Antoni et al., NIMA 513 (2003), 490

Scintillator module.

One of ∼ 200 fromKASCADE experiment.

Kindly provided by A.Haungs et al., Karlsruhe.

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Particle-detector development

Design considerations:

I reliability

I maintainability

I power consumption

I latency

I particle aperture

I radio-frequency interference

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Particle-detector development

light-tight box and RFI shieldingscintillatorphotodetectorlight guide

coincidenceunit

trigger

Design considerations:

I reliability

I maintainability

I power consumption

I latency

I particle aperture

I radio-frequency interference

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Particle-detector development

Work under way at Jodrell BankObservatory:

I component testing

I prototype soon

pulse-amplitude distribution for3mm SensL SiPM

light-guide directional sensitivity

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N. Cartiglia, INFN Turin

From Xmax, we get science:

I composition

I particle physics

Radio with LOFAR: fit simulationsto radio footprint.

Resolution ∼ 17 gm/cm2

Buitink et al., Phys. Rev. D 90 (2014) 082003

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Radio composition results from LOFAR

Buitink et al. (2016), Nature, 531, 70 Taylor (2016), Nature, 531, 43

Unexpected preponderance of low-mass cosmic rays (e.g. protons,helium nuclei) around 1017.5 eV.

I new class of Galactic cosmic-ray accelerators, reaching higherenergies than SNRs?

I extragalactic cosmic rays dominating at lower energies thanexpected?

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Radio hardware results from LOFAR

Also contributions to finding and solving issues with timing,antenna model.

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Cosmic-ray radio experiments

A. Zilles; published in T. Huege (2016), Physics Reports, 620, 1

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A. Zilles

Completely-sampled footprint.

Extreme precision:

∆Xmax,stat ∼ 7 g/cm2

Need new observables.

Other experiments in the high-precision space:

I Auger-HEAT: operational; less precision; larger aperture

I IceTop: planned radio/scintillator expansion; similar aperture

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Effects of cost-saving measures

High precision requires precisecalibration of the antenna model.

Terrible with analogue beamforming!

I events detected through sidelobes

I analogue variability

Attempted with LOFAR-HBA;abandoned in favour of LOFAR-LBA.

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Effects of cost-saving measures

High precision requires precisecalibration of the antenna model.

Difficult with analogue beamforming!

I events detected through sidelobes

I analogue variability

Attempted with LOFAR-HBA;abandoned in favour of LOFAR-LBA.

Reduced bandwidth iseasier to quantify.

0 50 100 150 200 250 300 350 400Frequency (MHz)

0

2

4

6

8

10

12

14

Xmax

reso

lutio

n (g

/cm

2 )

band

simulations: A. Zilles

. . . but this does not dependon processed bandwidth.

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Effects of cost-saving measures

High precision requires precisecalibration of the antenna model.

Difficult with analogue beamforming!

I events detected through sidelobes

I analogue variability

Attempted with LOFAR-HBA;abandoned in favour of LOFAR-LBA.

Losing core stations is a direct loss ofaperture . . . but this is not so abruptlycatastrophic.

Reduced bandwidth iseasier to quantify.

0 50 100 150 200 250 300 350 400Frequency (MHz)

0

2

4

6

8

10

12

14

Xmax

reso

lutio

n (g

/cm

2 )

band

simulations: A. Zilles

. . . but this does not dependon processed bandwidth.

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Lunar particle detection

Candidate detection in real time.

LOFAR as SKA pathfinder.

Work by Tobias Winchen, VUB.

Lunar signal path

core stations remote stations

stationbeamforming

stationbeamforming

pulsarbeamformer

stationbuffers

triggeringunit

trigger

metadata storage

data

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Effects of cost-saving measures

Neutrino flux limits

1016 1017 1018 1019 1020 1021 1022 1023 1024

Eν (eV)

104

105

106

107

108

109

E2 ν

Φν (e

V m−

2 s−

1 s

r−1)

ANITA

RICE

Auger

exotic-physicsneutrinos

GZKneutrinos

SKA-LOWpre-rebaseliningcurrentcost-cut

Detection threshold∝

√Tsys/Aeff∆ν

I collecting area isimportant

I beamformed bandwidthis important

Resolution is not so important.

We already assumed we need to supply our own triggering unit.

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Summary

Analogue beamforming for SKA-LOW

I may rule out atmospheric detection of cosmic rays

I and any contribution it can make to calibration

Losing core stations

I loss of aperture for atmospheric detection

I loss of sensitivity for lunar detection

Reducing digitised bandwidth

I loss of precision for atmospheric detection

I loss of sensitivity for lunar detection

Reducing processed bandwidth

I loss of sensitivity for lunar detection

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Summary

Analogue beamforming for SKA-LOW

I may rule out atmospheric detection of cosmic rays

I and any contribution it can make to calibration

Losing core stations

I loss of aperture for atmospheric detection

I loss of sensitivity for lunar detection

Reducing digitised bandwidth

I loss of precision for atmospheric detection

I loss of sensitivity for lunar detection

Reducing processed bandwidth

I loss of sensitivity for lunar detection

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