Status of IceTop tank testing Tom Gaisser, Madison, Feb 20, 2003

Outline Tests at South Pole – Serap’s report at Berkeley, March 2002 (next 9 slides) Development work in lab at Bartol – end of 2001, first half of 2002 Testing in Port of Wilmington freezer – Sept 2002 – present Paul Evenson: detailed report on top-down method and discussion of deployment

Tank2000 Tank m SPASE2 Shack MAPO Where are the Tanks?

Technical details: Deployed in December 2000 Cylindrical Polyethylene tank radius=60cm height= 124cm Lined with white Tyvek inside for diffusive,high reflectance Black velvet on top 2 Standard AMANDA OMs frozen in top looking down Heating rod in the middle to channel excess water during freezing Filled with station water 36 days to freeze Block of ice of 1.14 m 2 x 0.99 m Tank cm 51 cm 60 cm Heating rod (later removed) crack

Technical details: Deployed in December 2001 Cylindrical Polyethylene tank radius=107cm height= 124cm Lined with white Tyvek inside Black velvet on top 2 Standard AMANDA OMs frozen in top looking down PVC pipe in the middle with heating tapes, thermo sensors to channel excess water during freezing Several different color LEDs for later calibration Filled with station water 28 days to freeze Block of ice of 3.6 m 2 x 0.99 m Tank cm 102 cm cm Heating tapes Thermo sensors LEDs

Tank2000Tank2001 Tank2000 Tank2001

A stand alone DAQ for waveform acquisition 2 digital scopes connected to a Linux PC through PCI-GPIB 4 different triggers through separate Tank dedicated electronics - Muon telescope - Tank OM coincidence - Tank OM coincidence - 2 tank coincidence Tank OM signals are integrated into SPASE DAQ 4 OM TDCs and ADCs are read whenever there is a SPASE trigger Readout & Triggers

ICRC 2001 paper Muon Telescope Record waveforms of through going muons Time dependence of muon signals Muon flux at the South Pole Coincidence with SPASE Tank Measurements Amplitude and Charge change 2000 during freezing 2001 after 1 year Through-going Muon South Pole Zenith Angle o Rate (Hz)   

Tank Measurements Calibration w/ Muon Telescope all high gain SPE ~ 7mV, FWHM ~ 30ns Vertical muon pulses ~ mV FWHM ~50ns ~ 42 pe HV: 1130V 1350V HV: 1350V 1380V

Tank Local Coincidences Tank2000 rate 390 Hz each 0.5 pe 215 Hz each 12 pe Tank2001 rate 1900 Hz each 0.5 pe 540 Hz each 12 pe Tank Measurements

2 Tank Coincidence 3.8 Hz each 0.5 pe 1.2 Hz each 12 pe Tank Measurements

Coincidences with air showers (from Hamburg ICRC paper) Core distance 5 – 20 m 20 – 35 m 35 –50 m 50 – 65 m High-gain PMTLow-gain PMT Average peak signal in millivolts Shower size as S(30) = density of charged particles 30 m from shower core

Various tests freezing water in small containers in the lab led to design of controlled top-down freeze Small-scale tests in chest freezer in lab

Freezing tests in the lab 2002: small tank with degasser

Commercial (bottom-up) method Photos: summer 2002

Lab tests: bottom-up

Test tanks at Port of Wilmington Top-down tankBottom-up tank (with two rows of insulation remaining) Both tanks slightly over half frozen at present

Two methods Top-down –Natural to freeze from top, as in a lake –Problem is to manage expansion in confined volume while removing gas from freezing front with active degassing –Last (cloudy?) ice is at bottom, away from PMT Paul Evenson will show in detail how to do this Bottom-up –Problem is to keep top from freezing when it’s cold outside –Gas bubbles tend to rise so circulation alone removes gas as ice front advances –Last (cloudy?) ice is at the top, near PMT Next 4 slides describe status of bottom-up

Depth profile of bottom-up tank Andrew McDermott measuring ice thickness in bottom-up tank --pump is on the right of the photo

Top view of bottom-up tank showing cover and grid for depth measurements Heater mounted under hat 3 piece cover of styrofoam insulation mounted below plywood backing

Ice-depth vs time for bottom-up tank Dec 23 Jan 3 Jan 17 Feb 6 Feb 12 Blue line connects measurements of average depth Red dashed lines: upper—depth near edge lower—depth near center Middle insulation band removed Feb 5 Tank filled Nov 18

Photo on 5 Feb 2003 showing skim of ice after pump had been off for several hours

Signals of vertical and 45 o  Trigger on SPASE scintillators, one above and one below the tank Vertical muon deposits 200 MeV in 1 m water/ice Compare runs taken just after filling with runs taken with half ice, half water Compare with simulations

Muon signals Four locations of muon telescope: Setting 2: some trajectories go through OM Setting 1: diagonal trajectory deposits more energy Setting 3: opposite pump Setting 4: near pump

Average wave forms in water-filled tank, 4 telescope configurations

Configuration 1: diagonal

Vertical, configuration 2

Bottom-up tank, diagonal configuration Feb 13 (bottom ice, top water)

Simulations Based on GEANT4 –As used for Auger tanks –Modified for specifications of smaller tanks (2 m diameter, 1 m depth) with Tyvek lining by Ralf Ulrich and Todor Stanev –Tuning for ice and imperfections in progress –Need to determine and insert parameters for AMANDA PMTs we are using

Compare simulations with data (in water)

Assumptions in simulation Note: except for tank size, these are Auger parameters Need to use parameters for our PMTs Tank geometry Muon generates Cherenkov photons: GEANT4 Tyvek reflectivity = specular (  > 0)+ Lambertian PMT gain: 2 x 10 5 Impedance: 50  Quantum efficiency: ~0.16 One PE pulse: Gaussian,  =2.55 ns, t ½ =8ns One PE integrated charge: 1.6 x C

Current status and plan Both tanks somewhat over half frozen with a layer of imperfections Try to finish freezing both tanks, including layer of imperfections Final layer of ice may be cloudy Take data triggering on muons with pair of SPASE scintillators Compare signals in imperfect ice with simulations Determine a minimum clarity/ice-quality requirement for tank detectors Perform tests of stability of ice under mechanical and thermal stresses