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

2. April 26, 2007Rolf Nahnhauer IceCube Spring Meeting2 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

3. April 26, 2007Rolf Nahnhauer IceCube Spring Meeting3 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

4. April 26, 2007Rolf Nahnhauer IceCube Spring Meeting4 SPATS – Goals vs. Mysteries Part 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

5. April 26, 2007Rolf Nahnhauer IceCube Spring Meeting5 SPATS – Goals vs. Mysteries Part 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

6. April 26, 2007Rolf Nahnhauer IceCube Spring Meeting6 SPATS – Goals vs. Mysteries Part 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

7. April 26, 2007Rolf Nahnhauer IceCube Spring Meeting7 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 A5  C5 A5  B5 t / 2.5µs A5  B,C d / m t / 2.5 µs

8. April 26, 2007Rolf Nahnhauer IceCube Spring Meeting8 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 (using reciprocity 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 transmitters volunteers ?

9. April 26, 2007Rolf Nahnhauer IceCube Spring Meeting9 Environmental Influence At 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 ?

10. April 26, 2007Rolf Nahnhauer IceCube Spring Meeting10 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 ?

11. April 26, 2007Rolf Nahnhauer IceCube Spring Meeting11 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 at 80 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

12. April 26, 2007Rolf Nahnhauer IceCube Spring Meeting12 Necessary Activities Have 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 !

13. April 26, 2007Rolf Nahnhauer IceCube Spring Meeting13 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

14. April 26, 2007Rolf Nahnhauer IceCube Spring Meeting14 The Global Picture Should not forget the final goal: Build a hybrid optical-radio-acoustic detector of ~ 100 km 3 instrumented volume around icecube, ready for operation in ~10 years (2017) Outer boundary conditions require to stay with this time scale BUT Preliminary SPATS results do not allow to go full speed ahead Programme 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)

15. April 26, 2007Rolf Nahnhauer IceCube Spring Meeting15 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

16. April 26, 2007Rolf Nahnhauer IceCube Spring Meeting16 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 program - Drilling and deployment - Power and communication - Realization time scale *) see my Baton Rouge talk one year ago

17. April 26, 2007Rolf Nahnhauer IceCube Spring Meeting17 THE END Meeting of all parties interested to join an Acoustic Neutrino Detection working group suggested for Wednesday or Friday evening