The ACoRNE Collaboration Present projects and future plans

1. The ACoRNE Collaboration Present projects and future plans Prof. Sean Danaher University of Northumbria, Newcastle UK

2. Introduction • New PBH Predictions and acoustic simulation • Single Event Analysis (presented April IoP- • but very different conclusions)‏ • New Array calibration with a bipolar transmitter • Towards a full pancake simulator (New Results)‏ • Conclusions

3. Rona Hydrophone Array • MoD facility in North West Scotland • An array of high sensitivity hydrophones with a frequency response appropriate to acoustic detection studies • Existing large-scale infrastructure including DAQ, data transmission, buildings, anchorage • PPARC/MoD funding permitted us to upgrade Data Acquisition system and to record about a year’s worth of unfiltered data . • Provides an excellent test-bed for the “simulator” 30 June 2010 ARENA Workshop 3

4. Animation

5. How do we detect UHE neutrinos acoustically? • When a UHE neutrino (>c. 1018eV) interacts with a medium such as water the subsequent hadronic shower can deposit sufficient thermal energy to produce a detectable acoustic signal. Time rate of change of volume Rapid Expansion (ns)‏ Slow Decay (ms)‏ • At these frequencies the attenuation length in water is very long (kilometres)‏ • Leads to the possibility of huge effective volumes for neutrino detection for a sparsely populated hydrophone array

6. Can we find PBHs Acoustically? A bit of History (part of my PhD work), but was using Atmospheric Cherenkov PBHs may have formed during the big bang and radiate at a temperature of

7. PBH1 PBHs get hotter as they evaporate and eventually blow up. Their anticipated life time is given by PBHs of mass >5e14 have life times of greater than 1e18s and should still be around Theshapeofthespectrumisapproximately Gaussian on a loglog plot. Integrating gives a total power of

8. PBH2 The radiation will be mixture of electrons, neutrinos and about 20% photons. This energy is lost to the water through ionisation and Bremsstrahlung Where Assuming PBHs in the vicinity of the sun are moving through the galaxy at the same velocity, than the earth’s will sweep through the PBH at a velocity of about 30km/s

9. PBH3 We ignore the Bremsstrahlung term as it contributes little to the immediate thermal energy The PBH thermal deposition can be calculated from where is the total number of particles emitted per second =3.8x1025/M This energy is deposited in an axially symmetric ring and after some geometrical calculations we end up with

10. PBH Generated Acoustic Pulses The thermal energy can now be converted into an acoustic pulse using the standard acoustic integral technique

11. We have previously presented coincidence analysis Limits from array using 4 fold coincidence of hydrophones (from Simon Bevan UCL Thesis)‏ The array geometry at Rona is poor as we have so few hydrophones and on a plane. Because of the pancake only a small fraction of potential events hit the array. Need to do single hydrophone analysis Disadvantage is high noise background so need to look at bigger pulses.

12. Single Hydrophone Analysis • Neutrino interactions (>1020 eV)‏ • Primordial black holes • Any other unexpected phenomenon.

13. Preliminary data analysis ( 2 weeks)‏ • Observed pulses have an approx exponential spectrum above c 1Pa We applied some simple cuts • has to be >3 higher than the other pulses in the 2001 sample window • has to be a single – not part of a train • shorter than about 0.35 ms • No significant change in the background before and after the pulse • |Skewness| <0.5 • Kurtosis<5 APPLY CUTS Original Spectrum Only 5 pulses with magnitudes>0.4Pa

14. Examine all data (245 days)‏ • 81 events survive with peak pressure above 0.4 Pa. • Each scanned visually to look for bipolar pulses. • Most of them are multiple oscillations.

15. Some typical pulses

16. Pulses classified by number of oscillations Golden Event

17. Preliminary Conclusionsof single Hydrophone Analysis • 2 events (inverted probably background). • No neutrinos (limit 5 orders of magnitude above W-B). Sensible limits need very large targets e.g. moon or polar ice cap (ANITA). • No axions • No primordial black holes. • No other unexpected phenomena.

18. Omni Calibrator Two coupled masses seem to be OK for our transmit hydrophone. The two mechanical resonances are at 43.6 and 53.6kHz Mechanical Model Series of coupled masses Electrical model RC circuit with a current source Impedance matching network Different on Tx (velocity/acceleration) and Rx (pressure)‏ Electrical model Tank Reflection

19. Injects at Rona Sept ‘08 The 23kHz bipolar pulses were injected every 2s These are clearly visible. Analysis is ongoing.

20. Do these look bipolar? Hydro 1 Hydro 2 NO! An even bigger surprise is that Hydro 2 may be inverted wrt Hydro 1? Maybe Tfs different?

21. Possible Explanation We have no information as to the phase response of the Rona Hydrophones. But We have confidence that our simple hydrophone models work so the expected pulses may look like this Need to re-examine our data!

22. Creating a bipolar pancake • How many individual bipolar sources do we need to generate a suitable pancake? • Bipolar inject simulated • 1km from source • N sources deployed over 10m with (10/N)m spacing • Study the angular profile as a function of the number of sources • Of order 6 to 10 hydrophones (minimum) are needed

23. Need a different solution • The National Instruments system is fine for a single hydrophone, but we want to excite 8 hydrophones more or less simultaneously with pulses calibrated for each individual hydrophone • Also needs to be robust and hardened for a marine environment and work from a battery. • Need to Beam form – steer pancake electronically • Have gone for a PIC 18 series solution • Designed for 250kHz 12 bit DAC

24. 8x Power Amplifier Module The +/-100 Vdc is provided from a 12V or 230V mains

25. 8 Channel Module Designed by Wichian

26. Does it work? Bipolar 23kHz (PIC module)‏ Bipolar 23kHz (NI module)‏ 26

27. Teething Problems The joys of Hardware! Problem was tracked down to a 24p Quad OP-AMP. The slew rate was too slow! Temperature? PIC 10kHz Bipolar PIC 23kHz Bipolar

28. To be done • Electronics built and tested • Hydrophones sitting in a box in my office • Need to design and build the mechanical framework • Need to be able to steer the array – probably electronically by beam forming

29. Conclusions • We take ARENA seriously! • New PBH calculations presented here for the first time • Array calibration presented here for the first time • Pancake generator new results presented here. • We are very happy to deploy or calibrator over other arrays • Reality is always more interesting than theory so more analysis needs to be done • Small collaborations can achieve a lot. • Questions?