Acoustic test setup at south pole

1. Acoustic test setup at south pole IceCube Collaboration Meeting, Berkeley, March 2005

2. Motivation Evalution of acoustic detection needs acoustic parameters of south polar ice • Absorption length • ≈ few km • temperature dependant depth dependant • Speed of sound / refraction • vice≫ vwater larger signals ( Pmax∞ vice2) • density dependant refraction of surface noise • Noise level • determines energy threshold • Background events • few signal events/year few transient events or good suppression

3. Setup • Use IceCube • 3 distant holes • down to 400 m • 7 levels per hole • sensors • transmitters • auxiliary • Surface digitization • String PCs • DAQ • Power • Fiber LAN

4. Acoustic stage • In all three holes • at the same height do measurement in same layer • sensor and transmitter at each stage reduce systematic error in redundant setup • Sensor module and transmitter module • close together  check with low signals • standard pressure housing • 10 cm diameter steel tube • end caps with commercial penetrators • String support • own steel cable • avoid signal shielding by IceCube cable need spacer • Auxiliary devices • temperature or pressure sensors • commercial hydrophones

5. Acoustic stage: sensor • Sensor module • based on existing design • PZT5 piezoceramics plus amplifier directly coupled to steel tube • three channels per module local coincidences directional information • Power supply • cable losses use larger supply voltage ±5V generated in module

6. Acoustic stage: transmitter • Active element • piezoceramic transducer signals ≥ 1000 V possible • no orientation possible ring-shaped ceramic  azimuthal symmetry • broad resonance large pressure amplitude • directly coupled to the ice calculable system • HV Signals • Problem: cable capacitance down in the ice • use LC-circuits sine bursts and pulses

7. Cables • Sensors • differential signals 3×2 (twisted pairs) • power supply 1×2 • Transmitters • signal 1×2 • power supply 1×2 • Option 1: flexible outdoor robot cable • 6×2, 8×2 … 16×2 twisted pairs • 0.51 mm2 (ATW24), 100 Ohmloss: < 2 dB/100m • used for moving parts at -40 deg •  ≈ 6€ / m (8×2  one cable) • Option 2: use cheap ethernet cables • 4×2 twisted pairs • 0.52 mm2 (ATW24), 100 Ohmloss: < 2 dB/100m • two free pairs from transmitter use for auxiliary sensors • tested for -20 deg test at lower temperatures •  ≈ 0.3 € / m (4×2  two cables)

8. String PC • Limitations • cable costs • cable losses •  DAQ at top of each string • String PC • DAQ board(s) • Power supply • Fiber LAN switch • only used for data handling slow CPU, small disk • buried in snow waterproof container

9. String PC: DAQ • DAQ requirements • Low sampling rates • low data rates •  use of the shelf DAQ • Proposal: NI-DAQ 6259 • 16 differential inputs two cards per strings • 1.25 MHz single channel • 1.0 MHz multichannel 83.3 kHz per channel • digital and analog triggering • variable gain: ± 50 mV to ± 10 V large dynamic range • 4 differential outputs transmitter signals

10. String PC: Power supply • Power consumption • Wire resistance: AWG24 (0.5mm2), 500m 86 ohm / pair • Sensor • ± 5V / 30mA per amplifier ~ 1W / 100mA per module • cable loss (86ohm, 0.1A)  ΔU = 8.6V • Transmitter • +5V / 200mA, ~ 1W per module • cable loss (86ohm, 0.2A) ΔU = 17.2V •  Power Supply: TXL Series • Uin = 86V-264 VAC 50/60Hz • size 99x82x35 mm fits into standard PC housing • sensors: TXL 035-1515D Uout = ±15V / 1.3A • transmitters: TXL Series, TXL 060-24S Uout = 24V / 2.5A • Total: ~15 W per string

11. String PC: Fiber LAN • Data rates • 2 DAQs x 1.0 MS/s x 16 Bit ≤ 32 MBit/s per string • Optical fiber LAN • 2- or 4-port (String-PC/Master-PC) • 1 GBit/s standard • 10 km Point-to-Pointon single mode fibers • Cheap outdoor cable rated-50 degrees test for large arrays

12. Cost estimate

13. Project schedule 2005

14. Cargo cables, PCs, DAQ Sensor and transmitter modules  total cargo need ≤ 5m3 Manpower deployment: trained person at the spot commissioning: DAQ connection and setup, primary testing one person, two weeks Deployment separate deployment deployment with string possible only affecting the last 400 m  OMs are in safe depth  find best solution with IceCube deployment responsibles Interference with IceCube Acoustic signals 1 km above IceCube  < 10 mPa signal at OMs Electric signals low voltage (±5Vpp) High voltage generated locally low duty cycle (≤ 1%). DAQ, power supply separate from IceCube  no interference expected Constraints from IceCube

15. Summary • all components are available and tested • reasonable cost and time scale • major activities at all other neutrino telescopes • go for pole season 05/06