April 26, 2007Rolf Nahnhauer IceCube Spring Meeting1 IceCube Future Directions - Acoustic Rolf...

April 26, 2007 Rolf Nahnhauer IceCube Spring Meeting 1

IceCube

Future Directions - Acoustic

Rolf Nahnhauer

DESY


Where do we stand today?

SPATS:

Deployment successful

Detector operates well

Data taking ongoing

First preliminary results available

As usual for start of an experiment in an unexplored region:

more questions than answers


Unexpected Mysteries

1) Holes freeze (partly?) from below

2) Width of gaussian noise is ~twice as large as in laboratory- or lake tests and increasing in time

3) Clear peaks seen in noise spectra at f > 50 kHz which never have been observed before

4) Noise peak frequencies depend on string location and increase with depth

5) Signal strength in general much smaller than expected from water tests

6) Many transmitter-sensor combinations not seen at all

7) No transmitter signals seen from above 140 m


SPATS – Goals vs. MysteriesPart I : Noise Behaviour

In spite of mysteries and short time since data taking started

two very positive observations made

` - transient noise very small (~1 event / sensor and minute) (has still to be quantified better only question of time)

- gaussian noise very stable, no short time fluctuations

Mysteries (2,3,4) have still to be understood,

Noise sources and couplings to the setup have to be identified and removed or filtered out

First ideas are under discussion

No show stoppers envisaged here


SPATS – Goals vs. MysteriesPart II : Speed of Sound and Refraction

Analysis has not yet been started

Needs precise timing (still some DAQ software missing)

Results will help to understand attenuation behaviour

No precise attenuation length can be evaluated without having understood refraction


SPATS – Goals vs. MysteriesPart III : Attenuation Length

The bad news:

Mysteries 5,6,7 have to be demystified before a reasonable attenuation length estimate can be given

probably no quick shot possible

Need:

Improvement of analysis

Better understanding of detector properties

Better understanding of different environmental parameters

May be, additional hardware in the ice


Future Plans for Analysis

Do better signal extraction (fit, first peak only, etc.)

Use timing for signal identification

Include refraction effects

Use Fourier filters for background reduction

Take more statistics for averaging

+++ many other ideas

A5C5

A5B5

t / 2.5µs

A5B,Cd / m

t / 2.5 µs


Future Detector Understanding

Most urgent: ice calibration of sensors

For sensors in ice: hard to imagine (e.g. distant explosions from three different sites around SPATS)

For new sensors: calibration in medium size tank (usingreciprocity method?)

Also important: test of transmitter output and sensor response at high pressure and low temperature (pressure chamber…)

measurement of „4π“ angular sound profile of SPATS transmittersvolunteers ?


Environmental InfluenceAt least two important questions:

what firn is doing to our measurements

- look for more theoretical input- find out, if a „lab“ study is possible (could one go to a glacier in the North to study that question?)

what hole-ice is doing to our measurements

- how freeze-in happens- how many bubbles are formed at detector surfaces- what kind of „border“ is formed at bulk ice- is hole ice inventing a second (very small) att. length- how relaxation may happen - could one expect larger signals and lower noise with increasing time after deployment

volunteers ?


New In-Ice Hardware A fourth string, build, using experience from SPATS first results, would help to do a better measurement

- will we get support from IceCube management? (hopefully yes, everything went smooth last season)

- will we be able to build it in time? (hard to say, would have to take decisions soon, depends on number of coll. institutes and m+m

- where we should deploy it? (not too distant from existing strings, because both sites have to hear each other, may be a bit deeper)

In case it will be done, it should be used for carrying:

- a few „upgraded“ SPATS stations- a few new, louder transmitters- new sensors to be tested

volunteers ?


A Possible Scenario

New: hole 62, 13th of next season

Distance to present holes 300 - 400m

430 m

500 m

X

X

Make new string 100 m longer

Don‘ t put stations at80 m and 100 m

Add stations at 430 m and 500 m

Use three upgraded SPATS stations at 250 m, 320 m, 500 m

Put loud transmitters at 190 m and 430 m

Use 140 m, 190 m,400 m and 430 m for new glaciophones,if available


Necessary ActivitiesHave to buy or construct, assemble and test during next 6 month:

- new cablage (530m, 2*7 cables + connectors + parts)- acoustic surface junction box- ASJB power distribution unit- DSL modems- PC 104- 3 fast + 1 slow ADC-boards- interface PCB- new transmitters- new sensors- ???

Total amount of money needed: ~20000.- Euro ?

But who could (and wants) do what?

need good timing concept

need in any case a technical coordinator !


Longer Term Scenarios

Assume we don‘t build a fourth string this year:

- in all following seasons new holes are in a distance from present SPATS, that new detectors there, would not hear the old transmitters

Two possible alternatives in this case:

- use available breakouts at 1450 m, like radio people do now would most probably need digitized readout,

- who would do such a development - at which time scale for which cost- also depth is not really favourable

- build a new three string setup with longer own cables needs a lot of money and manpower and maybe

a different concept


The Global PictureShould not forget the final goal:

Build a hybrid optical-radio-acoustic detector of ~ 100 km3 instrumented volume around icecube, ready for operation in ~10 years (2017)

Outer boundary conditions require to stay with this time scale

BUTPreliminary SPATS results do not allow to go full speed aheadProgramme described will need at least another year

How to fight one year delay on an already tough time scale ?

- Attract more collaborators - Cooperate better with radio- Do things now, which already can be done (without knowing, if acoustic stays an option)


What Next (1)?

Need new structure for future increased acoustic effort

Need real integration into IceCube structure

Suggestion form a new IceCube working group

Acoustic Neutrino Detection

(do something similar for radio)

SAC-PAP recommendations , March 2007:xx


WHAT Next (2)?Need closer cooperation with radio group

- global simulation frame

- part of electronics

Sould profit from closer cooperation with physics groups

- UHE neutrinos- cascades

Should all together start*) to think about :

-- Justify scientific programJustify scientific program- Drilling and deployment- Drilling and deployment- Power and communication- Power and communication- Realization time scale - Realization time scale

*) see my Baton Rouge talk one year ago


THE END

Meeting of all parties interested to join an

Acoustic Neutrino Detection working group

suggested for Wednesday or Friday evening

April 26, 2007Rolf Nahnhauer IceCube Spring Meeting1 IceCube Future Directions - Acoustic Rolf...

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