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The MU radar experiment for searching radio echoes from EAS
Takuji Nakamura1 ,Toshio Terasawa2, Hiroyuki Sagawa3, Hideaki Miyamoto3, y g , y ,Hideto Yoshida3 and Masaki Fukushima3
1N i l I i f P l R h1National Institute of Polar Research2Tokyo Institute of Technology
3University of Tokyo
MU radar
University of Tokyo
MU radar, Kyoto Univ.at Shigarakiat Shiga aki
Contents• Introduction
Wh t i th MU d ?• What is the MU radar?• The upgraded MU radar system (2004)pg y ( )• Observation of meteor trails
EAS h b ti• EAS echo observations– What is the target?g– Results
• Best candidate of EAS echoBest candidate of EAS echo• Less significant echo
Estimation of Energy– Estimation of Energy• Summary
Energy spectrum of cosmic rays; extending over 12 orders of energy
Origin of the ultra high ienergy cosmic rays
(UHECRs) is a long-di istanding mystery in
cosmic ray physics.
Very rare!1/1km2・century!/ ce tu y
↑1020eV↑109eV
Augerhttp://www.auger.org/news/PRagn/AGN_correlation_more.htmlEffective area 5165 km2
Now Pierre Auger Observatory is counting ~50 UHECRs in a year.
But we need more UHECRs. ….several thousands UHECRs are desirable for astrophysical study
Possible (expensive!) answer: Extreme Universe Space Observatory (EUSO)( p ) p y ( )
air shower
Possible ground-based alternative:Radio technique for UHECR detection
Passive technique … detection of geo-synchrotron emissiondetection of molecular Bremsstrahlung emission…
Active technique … radar detection of echoes from UHECR air showers
Similarity between meteors and cosmic rays (1)
‘Dust from beyond the solar system’, Nature 380, 283 (1996)
Meteors and cosmic rays are both coming from extraterrestrial spaceMeteors and cosmic rays are both coming from extraterrestrial space.
>1017 1018eV
Similarity between meteors and cosmic rays (2)
Altitude: 90-120km
Altitude: 10~20km
>1017~1018eV
Gorham(2001)
EAS
Dusts of several mm size vs. elementary particles
Similarity in total energy Similar-sized ionization
Since the radar detection of meteors is an established technique we
Similarity in total energy(several hundredths J ~ several J)
Similar sized ionization column in the atmosphere
Since the radar detection of meteors is an established technique, we should be able to apply the radar technique to cosmic ray detection.
What is the MU radar?
MU radar (middle and upper atmosphere radar) since 1984
103 m
Monostatic coherent pulse Doppler radar VHF 46 5MHz 1MW outputMonostatic coherent pulse Doppler radar VHF 46.5MHz, 1MW output Antenna aperture: 8330 m2 Beam width: 3.6 degPulse length: 1 – 500 μs
Observation height of the MU radargMU radar: Middle and Upper Atmosphere radar, RISH, Kyoto Univ.
Uppery
Thermosphere
Satellite
r atmospherphereH
eig
MeteorsSodium layerM
re
Mesosp
ght (km
Middle atmp
here
m)
Ozone layer
osphere
T h
AerosolsStratosphere
Ozone layer
Troposphere
T(oC) Lidar baloon rocket MST MU ISMeteor radar radar radar radar
Target of atmospheric radar
Atmospheric radar: Coherent scatter echo
perturbation of refractive index
Incoherent scatter echo
Ionospheric electronsperturbation of refractive index (humidity, density, electron density) due to turbulence
Ionospheric electrons
T~0 1s T 1
Φ(δn): ------ turbulence intensity Σ σ: density of very
T~0.1s T~1ms
-------dn/dz refractive index gradient
Σ σ: density of very small scatterer
Characteristics of radar and lidar observationMeasure atmospheric parameters as a function of range
-> very good height resolution can be achieved y g g
Transmission pulse (transmitter or laser)
Propagation of light (or radiowave) (transmitter or laser)(or radiowave)
Range
Time
MU radar (middle and upper atmosphere radar)
1. Active phased array antenna (475 Yagis)beam can be steered pulse by pulse into 1657 directionsp y p
2.Flexible system design with computer controlChange of observation set-up only takes 10 sec to 1 minute.
Most capable atmospheric radar In the world.
Machine time of the MU radarFor collaborative research(1984 2006)For collaborative research(1984 - 2006)2500
大気圏標準観測 電離圏標準観測 一般観測 キャンペーン観測 保守O(h
2000
Observ
h)/Hal Mainte
nance
1000
1500
vation f Year
nance
500
1000time
r
Observation
01984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
40
45
No.
prop 1984 Commencement of domestic collaborative
15
20
25
30
35
of posals
2005 O t I t ti l
research
0
5
10
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
s/HY
2005 Open to International community (2 - 4 /Half Year)
MU radar observation:Eff t f t h iEffect of atmospheric wave on
general circulation of the earth’s atmosphere
------Role of atmospheric gravity waves-----p g y----
Observation of typhoon (9426 typhoon:Orchid)
Courtesy: Dr. Yoshiaki Shibagaki (Osaka Elec-Comm. Univ.)
Cross section of tangential wind around the Typhoon 9426around the Typhoon 9426
Ctr-clockw
MotionMotion of typhootyphoonObserved wind
ClockwiMU radar Observed windRadial wind Tangential wind
MU radar
wind Tangential wind
Distance (km)Courtesy: Dr. Yoshiaki Shibagaki (Osaka Elec-Comm. Univ.)
The upgraded MU radar system(in 2004)
Upgrade of the MU radar (2004)
1984 MU radar installed Limited 4 ch1984 MU radar installed.1994 Upgrade of data taking system1997 2000 Minor upgrades
Limited 4 ch
Full 4chpg
(2001 Equatorial Atmosphere Radar in Indonesia)2004 MU ultra-multichannel digital receiver system +5 frequency d Di it l 29 hfrequency2005 International collaborative research(2-4 proposals/HY)
IT-radar system Digital 29 ch
UltraUltra--multichannel digital receiver sysrem multichannel digital receiver sysrem of the MU radarof the MU radarof the MU radarof the MU radar
1111
22 33 44 556677 88 99 1010
11115 frequency (f 46 4 )1111 1212 1313 1414 1515
1616 1717 1818
(from 46 – 47MHz)Transmission and
R i
+
1616 1717 1818 1919 20202121 2222 2323
2424Reception
Frequency domain i f f i i i2121 2222 2323
2525interferometer for imaging in radial direction (z)
Spatial domain interferometer , imaging in transversal direction (x,y)
New MU radar system is an imaging radar systemradar system
Detailed structure of turbulence layers is one of theDetailed structure of turbulence layers is one of the research target
Application of MU radar new system:Frequency Interferometer Imaging (Dr H Luce LSEET-LEPI
Time resolution: 2 minTime resolution: 32 77 sTime resolution: 32 77 sStable sheets and Turbulent structures by the range imaging
Frequency Interferometer Imaging (Dr. H. Luce, LSEET LEPI, France)
Time resolution: 2 minVertical resolution: 150 m
(=Standard observation mode)
Time resolution: 32.77 sVertical resolution: 150 mTime resolution: 32.77 sAfter Capon processingmode in the UTLS
物質輸送を司り大気環境変化の鍵を握る乱流等大気の微細構造の観測研究
Some well-organized “S” structuresbecome clearly visible after Thin layers are better resolved
application of the Capon processing
Courtesy:Prof. S. Fukao(Luce et al., 2008)
3-d imaging of quasi-periodic echo in the E-region Ionosshere (by S. Saito, NiCT, Japan)
02 June 200602 June 2006
Horizontal Images Mapped to 100 km altitude21:06:03 21:07:52 21:09:5721:09:01
war
d->
Nor
thw
EastWestVertical Images
140
tude
Vertical Images
100
Northward->
Alti
• High altitude (> 120 km) echoes.• Band (ribbon) structure aligned NW-SE drifting SW.
Northward
Observation of meteor trailsObservation of meteor trails
Meteor observation withnew MU radar receiving systemnew MU radar receiving system
April 30 – May 4, 2006Parameters
・Reception: 25 x 3-elememt crossed Yagi
・Pulse length :0.9km (16 bit complementary)
・IPP :2000μs
・Coherent integration:2
・Sample range: 70~280km
・On line meteor detection
Transmission beam patternPeak at 45 deg Zenith angle
25 receiving antennasRed: previous antenna set-up
Coherent output of 25 ch signalAntenna 1 Antenna 2
……. 全25出力
Power PhPhase
Time TimeTime (×4msec)
Time (×4msec)Improvement of S/N ratio by 14 dB
Meteor echo distribution03/M /200603/May/200650,000 echoes /day
Local time varationRange
distribution
HorizontalEcho height Zenith Angle
Horizontal distribution
f
Angle of arrival (AOA) estimationAngle of arrival (AOA) estimation -The receiving beam is very sharpAOA candidates are searched by steering the beam in all the possible-AOA candidates are searched by steering the beam in all the possibledirections rather than using a conventional interferometer technique
dBN dB
N
30 90W E 30 90W E 30 90
W E
Simulated received power S
Sp
when AOA is assumed to be zenith
An example of estimated AOA using real data
00-06 LT May 3, 2006N h d i d l i i (10 i )Northward wind velocities (10 min ave)
300x300km
95
9090
85
80
75
03LT付近に小ス100x100km
03LT付近に小スケールの波動が捉えられていると考えられる 同時観測さ
95
90られる。同時観測された大気光観測データ(塩川、名古屋大)と比較中
90
85
80
屋大)と比較中 75
EAS echo observations
What is the targetWhat is the target
free electrons inFresnel length LF
our target 2
EAS trailg F
incoming and reflected radar waves
relativisticrelativistic electrons
at the head of EAS radar
range REAS
475 Yagi Antennas
8330m2
103103m
Frequency: 46.5MHz Peak power: 1MWAverage power: 50kWShigaraki MU radar
C d f h b k b l h d l
What is our target? ★
Condition for coherent backscattering by electrons in the ionized column of the EAS trail
EAS axis propagation directionEAS axis propagation direction
NeThe effective length of scattering region
Ionized column(number of free electons Ne~NCR*105)Expected
Waveformeof scattering region is given by the Fresnel wavelength(~400-600m). The
fWe need a fast data sampling
incident waves
EAS front passes this distance within 1~2 μsec.
sampling.
incident waves
several μsThe lifetime of free electrons is determined by the attachment process
Relativistic electrons
backscattered wavesPredicted time profile (Gorham, 2001)
Benefit of coherent scattering
y pto atmospheric oxygen molecule, and is about 1μsec (e.g.,Vidmar, 1990)
NCR
Benefit of coherent scattering:Power of the scattered wave is
proportional to Ne2.
What is our target? ★
EAS axis propagation direction Geometrical condition satisfied
condition OK
ConditionNG
~ 5%
Limitation for backscatter radarheight10~20km
Total area covered ~several hundred km2
Limitation of pulse radar
Number of CRs to be detected by the MU
pduty ratio is 5% or less
Zenith angle <~40 60 deg Number of CRs to be detected by the MU radar (0.052=1/400 of incident CRs)
>1017 eV several tens/day>1017 5 V l/d
Zenith angle <~40-60 deg
>1017.5eV several/day>1018 eV several 10-1/day>1018.5eV several 10-2/day
Shigaraki MU radar
Contents:
MU radar: system description
Trial EAS echo observation (1) dTrial EAS echo observation (1)What is our target?Range determinationDi ti fi di
done
Direction findingThe ‘best’ EAS echo candidateLess significant EAS echo candidate
Trial EAS echo observation (2)Energy estimation
Next step: Multiple transmitters + receiversRealization of multiple stations for meteor echo casep
EAS echo observations
Range determinationRange determinationDirection finding
Range determination ★
Inter-Pulse Period (IPP)=4000μsecTransmission/Reception Timing
width64μsec
Reception ON192μsec
echo scattererΔt
0 142 334delay Δt
Δt
0 142 334μsec
0 78 272μsec
range L=cΔt/2y
radar
Reception ON:
From the head of the pulse: 142-334μsec (range 21.3-50.1km)
( 11 7 40 8k )
radar
Since the expected length of EAS echoes is less than pulse width,uncertainty of ~10km (±5km) is unavoidable.
From the tail of the pulse: 78-272μsec (range 11.7-40.8km)
Sampling frequency 500kHz (sampling time = 2μsec )
y ( )
Ordinary beam pattern
Transmission beam pattern Peak at 45 deg Zenith angle
Search of EAS position on the sky
Aperture Synthesis in Radio Astronomy
Direction finding
Aperture Synthesis in Radio AstronomyCorrelation between i&j antenna outputs
Fourier transformation
( Δrij =ri - rj )
1<= i, j <=25
Cij → Σ Cexp(-ikΔrij)ij=S(k)
Out of 475, 25 antennas are chosen.Signal intensity (brightness temperature)
toward the direction k
1423 directions are set in the sky area ofzenith angle θ =0-50o
0
zenith angle θ 0 50 , azimuthal angle φ=0-360o.
We calculate the brightness temperature for each direction every 2μsec. Then we search the peak of
10
20
30
40
direction every 2μsec. Then we search the peak of the brightness temperature.
(This is a time-consuming procedure. On a PC with Core2Duo 50
Zenith angle3.16GHz, it takes 2 and half hours to process the data of 20 sec duration. … factor 2h30m/20sec~450)
shows the size of antenna beam
EAS echo observations
The best candidate of EAS echoThe best candidate of EAS echo
Observations
• December 2 – 3, 2008 for 8 hours• Data analysis takes 500 times longer than
the observation timethe observation time• The survey of EAS echo candidate has
b fi h d l f h fi hbeen fished only for the first 3 hours.
5
In the panel (a), the brightness temperature (Tb) sky map for the range R=24+4.8 km
The ‘best’ EAS echo candidate
In the panel (a), the brightness temperature (Tb) sky map for the range R 24+4.8 km at 11:31:53.624 UT (02:31:53.624 LT) on 3 December 2009 is drawn. An EAS echo candidate (indicated by an arrow) was found at the direction of the zenith angle q = 12o and the azimuth angle f=185o.gThe time variation of Tb is shown in the panel (c), where the horizontal axis shows the time (ms) elapsed from the peak. A line with solid squares shows Tb at the peak direction (q = 12o , f=185o). We see that the duration of the echo was 4-6us, which is close to the duration expected for EAS echoes.We are tuning the MU system to optimize it for the detection of EAS echo candidates.
(zenith angle<50o)
Tb sky map
Echo search takes 500 times longer!
The ‘best’ EAS echo candidate
Npeak intensity~0.102008/12/3 02:32JST
synthesized map (zenith angle<50deg)
0.12
0.10 IQ_10IQ 11
Intensity time variations around the peak
bitr
ary
unit) E
peak intensity 0.10
Range: 24±4.8km0.08
0.06
0.04
IQ_11 IQ_12
nten
sity
(ar
b
0.02
0.00
3432302826242220sign
al i
# # # # # # # #8μs
N
E
Time variations of signal intensity at the peak, and surrounding points
range=24.8±4.8km
12/3 02:31:53.6 Time variation6μsec before the peakμ p
synthesized map
0 120.12
0.10
0.08
0 06
IQ_10 IQ_11 IQ_12
Intensity time variations around the peak
0.06
0.04
0.02
0 000.00
3432302826242220
range=24.8±4.8km
12/3 02:31:53.6 Time variation4μsec before the peakμ p
synthesized map
0 120.12
0.10
0.08
0 06
IQ_10 IQ_11 IQ_12
Intensity time variations around the peak
0.06
0.04
0.02
0 000.00
3432302826242220
range=24.8±4.8km
12/3 02:31:53.6 Time variation2μsec before the peak
時間変化μ p
synthesized map
0 120.12
0.10
0.08
0 06
IQ_10 IQ_11 IQ_12
Intensity time variations around the peak
0.06
0.04
0.02
0 000.00
3432302826242220
range=24.8±4.8km
12/3 02:31:53.6 Time variationJust at the peak
時間変化
p
synthesized map
0 120.12
0.10
0.08
0 06
IQ_10 IQ_11 IQ_12
Intensity time variations around the peak
0.06
0.04
0.02
0 000.00
3432302826242220
range=24.8±4.8km
時間変化
12/3 02:31:53.6 Time variation2μsec after the peak時間変化 μ p
synthesized map
0 120.12
0.10
0.08
0 06
IQ_10 IQ_11 IQ_12
Intensity time variations around the peak
0.06
0.04
0.02
0 000.00
3432302826242220
range=24.8±4.8km
時間変化
12/3 02:31:53.6 Time variation4μsec after the peak
時間変化μ p
synthesized map
0 120.12
0.10
0.08
0 06
IQ_10 IQ_11 IQ_12
Intensity time variations around the peak
0.06
0.04
0.02
0 000.00
3432302826242220
range=24.8±4.8km
12/3 02:31:53.6 Time variation6μsec after the peakμ p
synthesized map
0 120.12
0.10
0.08
0 06
IQ_10 IQ_11 IQ_12
Intensity time variations around the peak
0.06
0.04
0.02
0 000.00
3432302826242220
range=24.8±4.8km
The ‘best’ EAS echo candidate ★
Npeak intensity~0.102008/12/3 02:32JST
synthesized map (zenith angle<50deg)ExpectedWaveform
0.12
0.10 IQ_10IQ 11
Intensity time variations around the peak
bitr
ary
unit) E
peak intensity 0.10
Range: 24±4.8km We need a fast data li0.08
0.06
0.04
IQ_11 IQ_12
nten
sity
(ar
b sampling.
0.02
0.00
3432302826242220sign
al i
# # # # # # # #8μs
N
Eseveral μs
Time variations of signal intensity at the peak, and surrounding points Predicted time profile (Gorham, 2001)
range=24.8±4.8km
EAS echo observations
Example of less significant echoExample of less significant echo
MUI.080909.020441_CR+zen.txt
BB nn hgh Rmin Rmax Zmin Zmax zan ph IQsynthMax IQsynthZen
05 422 17 16.80 26.40 13.15 20.67 38.47 216.00 1.123E-001 3.092E-003
observed image0.15
0.10
0.05
0.00
252015101bin=2μsec
data#range_max
range_min25 27.5km
15 17.5kmS h i d iSynthesized image
MUI.080909.020441_CR+zen.txt
BB nn hgh Rmin Rmax Zmin Zmax zan ph IQsynthMax IQsynthZen
05 422 17 16.80 26.40 13.15 20.67 38.47 216.00 1.123E-001 3.092E-003
4 b f th t observed image0.15
4μs before the event
0.10
0.05
0.00
25201510ジ
1bin=2μ秒データ番号
Aperture synthesisにより合成した画像
最大レンジ
最小レンジ
25 27.5km
15 17.5km Aperture synthesisにより合成した画像
MUI.080909.020441_CR+zen.txt
BB nn hgh Rmin Rmax Zmin Zmax zan ph IQsynthMax IQsynthZen
05 422 17 16.80 26.40 13.15 20.67 38.47 216.00 1.123E-001 3.092E-003
2 b f th t observed image0.15
2μs before the event
0.10
0.05
0.00
25201510ジ
1bin=2μ秒データ番号
Aperture synthesisにより合成した画像
最大レンジ
最小レンジ
25 27.5km
15 17.5km Aperture synthesisにより合成した画像
MUI.080909.020441_CR+zen.txt
BB nn hgh Rmin Rmax Zmin Zmax zan ph IQsynthMax IQsynthZen
05 422 17 16.80 26.40 13.15 20.67 38.47 216.00 1.123E-001 3.092E-003
j t th t observed image0.15
just the event
0.10
0.05
0.00
25201510ジ
1bin=2μ秒データ番号
Aperture synthesisにより合成した画像
最大レンジ
最小レンジ
25 27.5km
15 17.5km Aperture synthesisにより合成した画像
MUI.080909.020441_CR+zen.txt
BB nn hgh Rmin Rmax Zmin Zmax zan ph IQsynthMax IQsynthZen
05 422 17 16.80 26.40 13.15 20.67 38.47 216.00 1.123E-001 3.092E-003
2 ft th t0.15
observed image2μs after the event
0.10
0.05
0.00
25201510ジ
1bin=2μ秒
最大レンジ
最小レンジ
25 27.5km
15 17.5km
MUI.080909.020441_CR+zen.txt
BB nn hgh Rmin Rmax Zmin Zmax zan ph IQsynthMax IQsynthZen
05 422 17 16.80 26.40 13.15 20.67 38.47 216.00 1.123E-001 3.092E-003
4 ft th t0.15
observed image4μs after the event
0.10
0.05
0.00
25201510ジ
1bin=2μ秒データ番号
最大レンジ
最小レンジ
25 27.5km
15 17.5km
MUI.080909.020441_CR+zen.txt
BB nn hgh Rmin Rmax Zmin Zmax zan ph IQsynthMax IQsynthZen
05 422 17 16.80 26.40 13.15 20.67 38.47 216.00 1.123E-001 3.092E-003
observed image0.15
0.10
0.05
0.00
252015101bin=2μsec
data#range_max
range_min25 27.5km
15 17.5kmS h i d iSynthesized image
MUI.080909.020441_CR+zen.txt
BB nn hgh Rmin Rmax Zmin Zmax zan ph IQsynthMax IQsynthZen
05 422 17 16.80 26.40 13.15 20.67 38.47 216.00 1.123E-001 3.092E-003
observed image (0<θ <90)0.15
simulated image (0<θ <90)simulated image
0.10
0.05
0.00
25201510ジ
1bin=2μ秒データ番号
最大レンジ
最小レンジ
25 27.5km
15 17.5km Aperture synthesisにより合成した画像Aperture synthesisにより合成した画像Synthesized image for a simulated signal coming from this di ti S b kdirection. Subpeaks appearing on the sky map are due to the effect of antenna sideeffect of antenna side lobes.
Calibration of System Sensitivity
Npeak intensity~0.102008/12/3 02:32JST
synthesized map (zenith angle<50deg)The ‘best’ EAS echo candidate
0.12
0.10 IQ_10IQ 11
Intensity time variations around the peak
bitr
ary
unit) E
peak intensity 0.10
Range: 24±4.8km0.08
0.06
0.04
IQ_11 IQ_12
nten
sity
(ar
b
0.02
0.00
3432302826242220sign
al i
# # # # # # # #8μs
N
E
Noise level (~0.0063)Time variations of signal intensity at the peak,
and surrounding points
Noise level ( 0.0063)
We estimate S/N=0.10/0.0063~16.
range=24.8±4.8kmHere noise temperature is determined by the galactic radio background, which is estimated to be ~10000K i l di th i ’ t t tincluding the receiver’s system temperature.
Calibration of System Sensitivity
Noise intensity
Pr =Signal intensity
Radar Equation
whereλ: wavelength 6.4 mgR: range (distance to EAS) 24±4.8 km …σb : radar cross section Pt: transmission power 1MW
(R24=0.8~1.2)
Pt: transmission power 1MWGt: transmission antenna gain ~1Gr: reception antenna gain ~137
Substituting appropriate values to λ, R, Pt, Gt, Gr, we have
From the observation of an EAS candidate, we have obtained Pr= 1.1×10-12 W.Finally, we obtain the estimation of the RCS,Finally, we obtain the estimation of the RCS,
d dCosmic ray energy, EAS structure, Geometrical condition for scattering
dependence
Summary• We applied a large VHF atmospheric radar (MU radar)• We applied a large VHF atmospheric radar (MU radar)
for detection of EAS radar echoes, in order to investigate echo characteristics and feasibility ofinvestigate echo characteristics and feasibility of multistatic large aperture radar observations.U i t t f t lti h l i i t EAS• Using a state-of-art multichannel receiving system, EAS echoes are scanned.F b i f b 3 h h d d• From observations of about 3 hours, we have detected one EAS echo candidate and 4 possible signals.
• The echo length was ~4us (HMFW) or less. From the observed echo power, we are trying to get the energies f h i i l ibl f hof the cosmic ray particles responsible for these
candidates.
Summary (cnt’d) – future plan• Since the echo duration is short, we will continueSince the echo duration is short, we will continue
our survey with a faster sampling rate (up to 0.5 us) with the MU radar for clarifying echowith the MU radar, for clarifying echo characteristics.
• After the investigations with the MU radar, we will design a set-up for field observations, and radar des g se up o e d obse v o s, d dexperiments with other EAS observation instruments will be carried out possibly at TA site in Utahwill be carried out possibly at TA site, in Utah.
E dEnd
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