The Status of Ice Cube Mark Krasberg University
The Status of Ice. Cube Mark Krasberg University of Wisconsin-Madison RICH 2004 Conference, Playa del Carmen, Mexico Dec 3, 2004
Ice. Cube – a next generation n observatory a cubic kilometer successor to AMANDA Detection of Cherenkov light from the charged particles produced when a n interacts with rock or ice Direction reconstructed from the time sequence of signals Energy measurement: • counting the number of photoelectrons • entire waveform read out Expected performance wrt AMANDA • increased effective area/volume • superior angular resolution • superior energy resolution 2
AMANDA-II 19 strings 677 OMs Trigger rate: 80 Hz Data years: >=2000 Optical Module PMT noise: ~1 k. Hz “Up-going” “Down-going” (from Northern sky) (from Southern sky) PMT looking downward 3
Polar Ice Optical Properties Scattering A Absorption ice bubbles dust Measurements: ►in-situ light sources ►atmospheric muons Average optical ice parameters: λabs ~ 110 m @ 400 nm λsca_eff ~ 20 m @ 400 nm
Ice. Cube Science Goals • High energy neutrinos from transient sources (GRBs and Supernovae) • Steady and variable sources of high energy neutrinos (AGNs and SNRs) • Sources of high energy cosmic rays • WIMPs (Dark Matter) • Unexpected or exotic phenomena • Cosmic Ray Physics 5
Ice. Cube Concept Deep In-Ice Array 80 strings / 60 DOMs each 17 m DOM spacing 125 m between strings hexagonal pattern over 1 km 2 geometry optimized for detection of Te. V – Pe. V (Ee. V) n’s based on measured absorption & scattering properties of Antarctic ice for UV – blue Cherenkov light Ice Top Surface Array 2 frozen-water tanks (2 DOM’s each) above every string 6
Amundsen-Scott South Pole Research Station 7
AMANDA muon event CC muon neutrino interaction track nm + N m + X 8
Track Reconstruction in Low Noise Environment 1200 m Ice. Top • • Typical event: 30 - 100 PMT fired Track length: 0. 5 - 1. 5 km Flight time: ≈4 µsecs Ice. Cube Accidental noise pulses: 10 p. e. / 5000 PMT / 4 µsec AMANDA 9
Energy Reconstruction Small detectors: Muon energy is difficult to measure because of fluctuations in d. E/dx Ice. Cube: Integration over large sampling + scattering of light reduces the energy loss fluctuations. Eµ=10 Te. V, 90 hits Eµ=6 Pe. V, 1000 hits
1 Pe. V t (300 m) t decays nt t 11
n - flavors and energy ranges pulse • Filled area: particle id, direction, energy • Shaded area: no particle id
Ice. Cube effective area and angular resolution for muons further improvement expected using waveform info Galactic center Median angular reconstruction E-2 nm spectrum uncertainty ~ 0. 8 quality cuts and background suppression (atm m reduction by ~106) 13
Diffuse Fluxes - Predictions and Limits Macro Baikal Amanda Ice. Cube Sensitivity after 3 years
Point sources: event rates Flux equal to 3 x current AMANDA limit d. N/d. E = 10 -6*E-2/(cm 2 sec Ge. V) Atmospheric Neutrinos All sky/year (after quality cuts) AGN* (E-2) Sensitivity (E-2/(cm 2 sec Ge. V)) - 100, 000 Search bin/year 20 2300 - 3 year: Nch > 40 (E > 7 Te. V) 0. 82 1370 2. 4 x 10 -9 Compared to AMANDA-II: 7 times more PMT --> 50 to 100 times more atmosph. neutrinos @ better angular and energy resolution
Ice. Cube Digital Optical Module 16
Digital Optical Module • records timestamps optical sensor 10 inch Hamamatsu R-7081 • digitizes waveforms penetrator HV board pressure sphere flasher board DOM main board delay board PMT optical gel mu metal cage • transmits to surface at request via digital communications • can do local coincidence triggering • design requirement Noise rate ~1 k. Hz • SN monitoring within our Galaxy
DOM Mainboard 2 four-channel ATWDs Analog Transient Waveform Digitizers low-power ASICs recording at 300 MHz over first 0. 5 ms signal complexity at the start of event fast ADC recording at 40 MHz over 5 ms event duration in ice HV Board Interface 2 x. ATWD FPGA Memories CPLD oscillator (Corning Frequency Ctl) running at 20 MHz maintains df/f < 2 x 10 -10 Dead time < 1% Dynamic range - 200 p. e. /15 ns - 2000 p. e. /5 ms energy measurement (Te. V – Pe. V) FPGA (Excalibur/Altera) reads out the ATWD handles communications time stamps waveforms system time stamp resolution 18 7 ns wrt master clock
DOM Waveform Capture High Gain • Altera Excalibur ARM 922 t m. P+ 400 k gate FPGA on a single chip • CPU runs data acquisition, testing facility, and diagnostic utilities • FPGA controls communications interface, time critical control of DAQ hardware, fast feature extraction of waveforms Medium Gain • 2× ATWD – each with 4 channels capable of digitizing 128 samples at rates from 0. 25 – 1. 0 GHz. 2 of them for ‘ping-pong’ mode. • 3 gain channels in ATWD for complete coverage of PMT linear region Low Gain • 10 -bit, 40 MHz FADC for capture of extended photon showers in the ice (6 ms wide). t 400 ns window 19
Calibration 1. Calibration of sensors in the lab at temperatures between -20 and -55 C (deep ice: -18 C to -42 C) 2. LED Flashers on each module, 12 LEDs, in 6 directions and 2 angles (10^10 photons) 3. Special “high energy” lasers 4. Timing calibration is feature of DOM: 5 nsec 5. Ice. Top: High level cross calibration of muon tracks with air showers. 6. Shadow of the Moon (at 25 to 30 degree elevation): Muon rate of about 1500 Hz will allow to calibrate angular resolution in astrophysical coordinates in short time scales.
DOM Testing DFL (Dark Freezer Lab) is large, dark, cold container which holds N test stations (N is sitedependent) each of which schematically looks like the figure. Optical fiber system carries light from optics breadboard (diode laser, LED pulser, monochromator-tuned lamp) to each DOM. Optics spreads light evenly out across PMT photocathode. 21
Dark Freezer laboratory: Test all optical sensors for ~2 weeks at temperatures -55°C to +20°C 22
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PMT HV Calibration C O U N T S CHARGE G A Nominal HV Setting I N VOLTAGE 24
Final Acceptance Test Results • In-Ice Noise Rate ~ 1 k. Hz • Time Resolution < 3 ns • Noise Stability Monitor detected Synchrotron radiation from the SRC, Physical Sciences Lab, Wisconsin Detection of Synchrotron across the street 25
Triggering on Cosmic Rays Single PE trigger Local Coincidence triggering for DOMs with 1. 5 m vertical separation 26
Getting to the South Pole A six hour flight from New Zealand to Mc. Murdo Station, via C-141 “Starlifter” 27
28 A three hour flight from Mc. Murdo to South Pole Station, via C-130 “Hercules”
Hose-reel with hose, built at Physical Sciences Laboratory UW-Madison (Nov 2003) Hose-reel at South Pole (Jan 2004) 29
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Summary Ice. Cube is deploying 256 DOMs next month! Ice. Cube is expected to be • considerably more sensitive than AMANDA • provide new opportunities for discovery • with Ice. Top – a unique tool for cosmic ray physics Ice. Cube strings 4 16 32 50 68 80 Ice. Top tanks 8 32 64 100 136 160 Jan 2005 Jan 2006 Jan 2007 Jan 2008 Jan 2009 Jan 2010 • Data taking begins early next year 31
Ice. Cube drill camp construction site of the first hole, Nov 25, 2004 32
• Bartol Research Institute, Delaware, USA • Univ. of Alabama, USA • Pennsylvania State University, USA • UC Berkeley, USA • Clark-Atlanta University, USA • Univ. of Maryland, USA • IAS, Princeton, USA • University of Wisconsin-Madison, USA • University of Wisconsin-River Falls, USA • LBNL, Berkeley, USA • University of Kansas, USA • Southern University and A&M College, Baton Rouge, USA (12) Japan Europe (12) Venezuela • Universidad Simon Bolivar, Caracas, Venezuela • Chiba university, Japan • University of Canterbury, Christchurch, NZ New Zealand ANTARCTICA • Universite Libre de Bruxelles, Belgium • Vrije Universiteit Brussel, Belgium • Université de Mons-Hainaut, Belgium • Universität Mainz, Germany • DESY-Zeuthen, Germany • Universität Dortmund, Germany • Universität Wuppertal, Germany • Uppsala university, Sweden • Stockholm university, Sweden • Imperial College, London, UK • Oxford university, UK • Utrecht, university, Netherlands 33
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