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。
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