the cosmic ray air shower and its radio detection

The Cosmic Ray Air Shower and its Radio Detection

陈学雷

国家天文台

EAS

Exp.

Cosmic Ray Energy Spectrum

The maximum energy observed so far is about

3.2x1020eV eq. 50 J

Many discoveries in particle physics: positron, muon, pion, Kaon, ...

Now: astrophysical side

Origin of Cosmic Ray

Fermi acceleration

Propagation of Cosmic Ray

charged particle moving in random magnetic field

E< 1015 eV, confined around galaxy

(some diffuse out)

Puzzle of Ultra High Energy Cosmic Ray: the GZK cutoff

Greisen 1966, Zatsepin & Kuzmin 1966

Possible solutions

• Incorrect measurement? Heavy nuclei?

• produced nearby: superheavvy dark matter? topological defects?

• produced nearyby: strong IGM magnetic field?

• produced far away: neutrino?

• produced far away: break down of relativity (violation of Lorentz invariance)?

GZK or not?

Detection of air showers

• Ground Array: small area emulsion, scintillator, water Cherenkov

• Optical: low duty cycle atmosphere Cherenkov Fluorescence

• radio: large area, high duty cycle

Radio Signal

Geosynchrotron (Kahn & Lerche 1966) charge seperation by geomagnetic field

Negative charge excess in EAS and radio signal (Askayran 1962): production of delta-ray (knocked out electrons) annihilation of positron in flight

First detection (Jelley et al 1965)

Review (Allan 1971), loss of interest

Revival (Falcke & Gorham 2002)

CASA-MIA, LOPES/LOFAR, CODALEMA

EM wave ~ apparant acceleration of electric charge

Coherent Emission: Radio Pulse

Radio pulse for a 1017 eV shower, at 0, 100,250 m from axis (Huege & Falcke astro-ph/0309622)

Signal Strength

Allan’s formula:

Spectrum

Monte Carlo Simulation by Huege & Falcke, astro-ph/0501580,

at 20m, 140m, 260m, 380m, 500m

distribution and polarization

total EW pol NS pol vertical pol

0o

30o

60o

90o

Energy Dependence

Background Noise

Falcke & Gorham, astro-ph/0207226

LOPESLOfar PrototypE Station

Measurements of air showers in the energy range E0 = 100 TeV - 1 EeV

KASCADE-Grande= KArlsruhe Shower Core and Array

DEtector + Grande

•10 antennas at KASCADE array•frequency band 40-80 MHz•trigger: >10/16 cluster of KASCADE

( E0 > 1016 eV)•2004: 7 months runtime•~630.000 triggered events

(and correlated EAS information) sufficient sample of events for detailed analyses

Progress

LOPES-10

LOPES-30

LOPES-STAR, LOPES-Auger

LOPES collaboration, Nature 425 (2005) 313

LOPES 10 Results

CODALEMA experiment

current setup (astro-ph/0608550)

Nancay DAM

COsmic ray Detection Array with Logarithmic ElectroMagnetic Antennas

Auger Detector

Results

Radio Detection in China

• relatively easy and cheap

• particularly suitable for UHECR

• not yet well-developed, room for exploration

• technology spin-off (application in military & technology)

Road Map

(1) concept design

(2) preliminary test: site selection, RFI background, instrument basics

(3) prototype: 4-10 antenna

(4) after analyzing prototype data, decide what to do

(5) Large scale deployment: core array for lower energy (10 17 eV) flux and sparse array for high energy. Area: 103-4 km2 with spacing 0.5-1 km.

prototype proposal

已申请本年度天文联合基金（仪器研制类重点项目 , 200万）

PI: 陈学雷

coI:施浒立 , 秦波等

Preliminary Design

• center frequency: 30 MHz

• wide bandwidth or multi-band (to overcome artificial RFI which is usually narrow band)

• multi-polarization loaded-dipole/half-wave antenna (ominidirectional, wide and smooth frequency response)

Amplification: 30-40 dB (to 0.1 V signal)

ADC: 10-100 MHz, 14 bit,

Simulated detection rate

Site Selection

西藏羊八井 :　　 coincidence test (AS, ARGO) but: (1) high altitude, (2) RFI, (3) too far

内蒙正镶白旗：　　 good EM environment, nearby, logistics readybut need coincidence detector, est. 100k per piece (Cao Zhen)

Plan

２００８年，研究大气簇射射电机制，设计模拟程序，进行天线和探测系统的初步设计、试制和实验室检测，对羊八井和正镶白旗站址进行测试， 对数据处理方法进行调研和初步设计；与国外有关研究人员联系，探讨国际合作研究的可能性。

２００９年，完成大气簇射射电模拟程序并进行模拟研究，对天线和探测系统进行野外测试和优化，设计、调试数据处理软件，邀请国外有关专家参与实验。

２０１０年，收集数据并进行分析处理，研究大规模宇宙线实验的可行性。