Post on 02-Jan-2016
description
transcript
Neutrino Detection, Position Calibration and Marine Science with Acoustic Arrays in the Deep Sea
Robert Lahmann
VLVnT 2011, Erlangen, 14-Oct-2011
2Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Outline
• Introduction: Neutrinos and Sound• Use of Sound in the Sea and the AMADEUS
acoustic system• Ambient Background and Transient Sources• The Future: Simulations and KM3NeT
3Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Outline
• Introduction: Neutrinos and Sound• Use of Sound in the Sea and the AMADEUS
acoustic system• Ambient Background and Transient Sources• The Future: Simulations and KM3NeT
4Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Neutrino Signatures in Different Media
radio lobe
sounddisk
optical light cone
light
radio
sound
Ice
Wat
er
Sal
t dom
es
Per
maf
rost
1016 eV 1017 eV 1018 eV
Ο(100)/km3
Ο(10)/km3
Ο(1000)/km3
sensor density
adapted from: R. Nahnhauer, ARENA Conf. 2010
5Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Acoustic Detection of Neutrinos
Ecasc= 1020 eV @ 1km
Adapted from arxiv/0704.1025v1 (Acorne Coll.)
Thermo-acoustic effect: (Askariyan 1979)energy deposition local heating (~μK) expansion pressure signal
Hadronic cascade:~10m lengthfew cm radius
~1km
Pressure field:Characteristic “pancake” patternLong attenuation length (~5 km @ 10 kHz)Allows for neutrino detection at E > 1018eV~
6Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Acoustic Detection Test Set-Ups
First generation acoustic test set-ups follow two “philosophies”:
• “We can get access to an acoustic array; why not use it for some tests for acoustic particle detection?”
• “We have a neutrino telescope infrastructure; why not install some acoustic sensors to test acoustic particle detection?”
7Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Acoustic Detection Set-Ups
ACORNE(military array)
ACORNE(military array)
AMADEUS(custom-built array)
AMADEUS(custom-built array) Lake Baikal
(custom-built sensor group)Lake Baikal
(custom-built sensor group)
ODE(custom-built sensor groups)
ODE(custom-built sensor groups)
SAUND(military array)
SAUND(military array)
SPATS(custom-built array)
SPATS(custom-built array)
8Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Overview Acoustic Detection Set-Ups
(*) The number of hydrophones was increased from 7 in SAUND I to 49 in SAUND II
9Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Limits on UHE Neutrino Flux
R. Abbasi et al.,arXiv:astro-ph/1103.1216
SPATS
SAUND2
ACORNE
10Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
The Lesson so Far
Existing Acoustic Setups:• Proof of principle• Limits not competitive
But first: Acoustic neutrino detection isn’t the first application of sound in water …
What is the potential of a “real” acoustic neutrino detector and what does it have to look like?
11Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Outline
• Introduction: Neutrinos and Sound• Use of Sound in the Sea and the AMADEUS
acoustic system• Ambient Background and Transient Sources• The Future: Simulations and KM3NeT
12Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Sound in Water
“Of all the forms of radiation known, sound travels through the sea the best”
(R. Urick, Principles of Underwater Sound, 3rd edition, 1967)
Used by marine animals and humans for communication and positioning
Speed of sound investigated (at least) since 1826 (from title page of “Physics Today”, Oct. 2004, experiment in Lake Geneva)
13Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
The Deep Sea is Loud!samples from www.dosits.org
t (0.2s)
snapping shrimps
snapping shrimps
dolphinsdolphins
sperm whalessperm whales
A(au)
14Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Interdisciplinary Cooperation
Nature New Feature, Vol. 463, p. 560 (2009)
OnDE I (Jan. 2005 –Nov. 2006)(Ocean Noise Experiment)
15Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Positioning in Deep Sea Cherenkov Neutrino Telescopes
AcousticEmitters
Detection Unit
Receiver
ANTARESNEMO II /
KM3NeT PPM
ANTARES:Commercial system calculates time delay measurements offshoreDisadvantage:- Raw signals not recorded, debugging difficult- Potential of hydrophones not fully used
Movement of Optical Modules withdeep sea currents needs to be monitored
16Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Principle of Future Deep Sea Acoustic Test Arrays
The obvious thing to do: All data to shore
Positioning
Acoustic detection
Marine science
Onshore:Filters and algorithms:
Offshore:Hydrophone array
~200 kSps16/24 bit
17Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
The AMADEUS System of the ANTARES detector• 34/36 sensors operational• Continuous data taking with >90% uptime• Online filter selects ~1% of data volume for
storage
Hydrophones:Typical sensitivity: -145 dB re 1V/PaDigitization:16bit @ 250kHzRecorded Frequency:2 ~ 100 kHz
Line 12:Operationstarted 30-May-2008
Instrumentation Line:Operationstarted 5-Dec-2007
18Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Goals of AMADEUS
Main objective: feasibility study for a potential future large-scale acoustic neutrino detector
Main tasks:
• Long term hardware tests
• Determine energy threshold for neutrino detection
• Investigate background conditions
• Devise high efficiency, high purity neutrino detection algorithms
Main science case: Cosmogenic neutrinos
19Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Position Reconstruction with Hydrophones
L12
IL07
Reconstruct position of each hydrophone individually using
emissionreceptionemissionreception tt scrr
Receive signals from emitters on anchors of the13 lines
20Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Outline
• Introduction: Neutrinos and Sound• Use of Sound in the Sea and the AMADEUS
acoustic system• Ambient Background and Transient Sources• The Future: Simulations and KM3NeT
21Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
N.G
. Le
htin
en
et
al.,
arX
iv:a
stro
-ph
/010
4033
Background for Acoustic Detection in the Sea
Bipolar (BIP) events
d3NdAdVdt
Bipolar Pressure Signals (BIPs)
Have to measure
rate of BIP events:
A
Determines fake neutrino rate Determines intrinsic energy threshold
Depends on “sea state” (surface agitation)
cf. Wenz, J. Acoust.Soc. Am. 34 (1962) 1936
Ambient noise
22Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Ambient Noise: DeepSea
N. Kurahashi, G. Gratta.Phys. Rev. D 78 (2008)
SAUND (Bahamas)OnDE (Sicily)
G. Riccobene, NIMA 604 (2009) 149
23Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Distribution of Ambient Noise Level (AMADEUS)
For sensor sensitivity of -145 dB re 1V/µPa (lab calibration),the mean noise level is 10 mPa
+2-2
+3-2
Median:
≈ 8 mPa
noise8.0
1 entry = noise level (f = 10 – 50kHz) of 10s of continuous data recorded every hour with one hydrophone (2008 – 2010 data)
24Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Ambient Noise Conclusion
• Median: Pthd = 16 mPa Ethd ≈ 1~2 EeV
• 95% of time ambient noise is below (~20 mPa) Pthd = 40 mPa Ethd ≈ 4 EeV
noise2
Good conditions for neutrino detection (stable threshold, level as expected)
Evaluate for f = 10 to 50 kHz (best S/N)
Assume detection threshold for bipolar signals with S/N = 2 @200m along shower axis
25Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011 2525
• Formula Pic with Threshold
Source Direction Reconstruction
t0 t
1 t
2 t
3 t
4 t
5
2)),((expectedmeasured
iii tt
minimize
Error: ~3° in φ, < 1° in
26Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
AMADEUS - Source Direction Distribution0o
90o-90o
-60o
120o
27Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Marine Science with AMADEUS
• Life data from AMADEUS web page: http://listentothedeep.org/(Maintained by University of Barcelona)
• Press releases Dec. 2010, picked up by several media:
e.g. http://www.economist.com/blogs/babbage/2010/12/astroparticle_physics
28Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Life Data from AMADEUS
29Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Transient Background Conclusions
• Exclude region near surface• Very diverse transient background,
signal classification crucial• Cut on pattern of pressure field
(“pancake”)
~50
0m“q
uite
zon
e”em
issi
ons,
refle
ctio
ns
30Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Outline
• Introduction: Neutrinos and Sound• Use of Sound in the Sea and the AMADEUS
acoustic system• Ambient Background and Transient Sources• The Future: Simulations and KM3NeT
31Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
The Neutrino Detection Rate
N 2T dE(E)Veff (E)
(E)
Effective volume:Depends on detection method
Flux: Depends on process of neutrino production
Mean Free Path: Depends on neutrino cross section
Number of detected events
Energy threshold:Depends on detection method
32Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Energy Deposition by UHE Hadronic Showers
S. Bevan et al., Astropart.Phys.28 (2007)
longitudinal and lateral hadronic shower profile from CORSIKA (adapted for
seawater)
z (cm)
33Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Simulation of Neutrino-Induced Acoustic Pulses
14.5
m
Sto
rey
1S
tore
y 2
10 EeV shower
200 m
x (m)
z (m
)
Ene
rgy
dens
ity (
a.u.
)
MC according to arxiv/0704.1025v1 (Acorne Coll.)
34Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Hybrid Detection in KM3NeT
• “all data to shore”-principle adopted• already: one software framework
⇒ intermediate step for acoustic detection Cooperation of European players
KM3NeT, artists viewKM3NeT, artists view
35Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Conclusions and Outlook
• Acoustic detection is a promising approach for the detection of UHE neutrinos
• Ambient background in the Mediterranean Sea: Stable, level as expected
• Transient background in the Mediterranean Sea: Methods for suppression developed; work in progress;Interesting for marine science
• Monte Carlo simulations and algorithms for neutrino selection under development
• KM3NeT: Combined system for acoustic positioning and neutrino detection planned; intermediate step for acoustic detection of UHE neutrinos
Funded by:
36Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Backup transparencies
37Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Setup of Acoustic Storey with Hydrophones
Titanium cylinderwith electronics
3 custom designed Acoustic ADC boards
16bit @ 250kHz
~1
0cm
Hydrophone:Piezo sensor
with pre-amplifierand band pass
filter in PU coating
Typical sensitivity: -145 dB re
1V/Pa
38Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
The Onshore Filter System
Task: Reduce incoming data rate of ~1.5 TByte/day to ~10 GByte/day
System extremely flexible, all components scalable
Local clusters (storeys) big advantage for fast (on-line) processing
10 s of continuous data/hour
Minimum bias trigger
39Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Properties of the Mediterranean Sea (ANTARES site)
Speed of sound depends on temperature, salinity, pressure (depth);temperature gradient only relevant up to ~100m below surface
40Robert Lahmann – VLVnT 2011, Erlangen – 14 October 2011
Refraction of Signals Reaching AMADEUS
Furthest signals from surface to reach AMADEUS: ~30 km distance, ~ -5.5° arrival angle
“Open water model”:Using conditions ofANTARES site forcomplete volumeof the simulation