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

Tank2001 10 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 m2 x 0.99 m

Tank2000

99.1 cm

51 cm60 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 m2 x 0.99 m

Tank2001

99 cm

102 cm107.32 cm

Heating tapesThermo sensors

LEDs

Tank2000 Tank2001

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- Tank2000 2 OM coincidence - Tank2001 2 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 rate @ South Pole

Zenith Angle o Rate (Hz) 0 2.22 0.01 15 1.80 0.01 35 0.72 0.01

Tank Measurements

Calibration w/ Muon Telescope

all OMs @ high gain

SPE ~ 7mV, FWHM ~ 30ns

Vertical muon pulses ~ 150-200 mV FWHM ~50ns

<1VEM> ~ 42 pe

HV: OM1 @ 1130V OM2 @ 1350V

HV: OM1 @ 1350V OM2 @ 1380V

Tank Local Coincidences

Tank2000 rate

390 Hz each OM @ 0.5 pe 215 Hz each OM @ 12 pe

Tank2001 rate

1900 Hz each OM @ 0.5 pe 540 Hz each OM @ 12 pe

Tank Measurements

2 Tank Coincidence

3.8 Hz each OM @ 0.5 pe

1.2 Hz each OM @ 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 PMT Low-gain PMT

Ave

rage

pea

k s

ign

al in

mil

livo

lts

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 tank Bottom-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 45o

• 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 configurationFeb 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 simulationNote: 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 105

• Impedance: 50 • Quantum efficiency: ~0.16

• One PE pulse: Gaussian, =2.55 ns, t½=8ns

• One PE integrated charge: 1.6 x 10-10 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