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。