Radio Čerenkov measurements in salt
UH Salt Detector Testbed

P. Miočinović

University of Hawaii at Manoa, Honolulu, Hawaii, USA

May 19, 2005

ARENA Workshop, DESY Zeuthen

Motivation

Experimental setup

Analysis progress

Summary and Outlook

Outline

Motivation

Detecting the first coherent radio Čerenkov signal of natural origin

Exploration of Askaryan effect in rock salt in broad range of energies

Evaluating potential of rock salt as a medium for detection of UHE particles

Electronics evaluation testbed for ANITA and SalSA

Experiment

Target material: 20 tons of synthetic rock salt

- rock salt blocks, weighing 22.7 kg each

- purity of the salt: 93-96%

Bowtie antennas embedded in salt and amplified by cable TV technology

Computer controlled waveform readout

Camac-based trigger from MACRO particle counters;
100 GeV threshold, ~2500 ev/day

20,000 kg of synthetic rock-salt placed in the rectangular wooden box.

index of refraction n = 2.4; θC = 65°

specific density ρ = 2.08 g/cm3

radiation length Xo = 13.5 cm

critical energy EC = 52.6 MeV

dimensions of the box 12 x 1.2 x 0.8 m

interior walls covered with thin zinc plated steel sheets

two rows of antennas were placed on the lowest layer of salt blocks.

3 MACRO counters track charged particles as a trigger for antenna readout.

Experimental Setup

Antennas and RF readout

Dual linear polarized bowtie antenna
printed on PCB

Frequency response ~0.2-2.0 GHz

300 MHz

600 MHz

920 MHz

RF readout through a custom, low-power digitizer chip (STRAW2) mounted on cPCI card (ANITA/SalSA prototype)

12 RF channels per card

sampling rate 2.12 GS/sec,
~250 samples per waveform

~120 ns

Data Taking

For each trigger, 48 RF signal and 12 PMT signal channels are readout

Two dimensional reconstruction of particle track is based on PMT timing

2.7 sec later, background RF reading is taken

fully captured particle

transit window (~ 60 ns)

MC expectations

based on Askaryan signal strength measured at SLAC, 1σ voltage level for cascade energy of 2.8 TeV

Total expected event rate is
3.45 events/yr

2σ rate 0.86 ev/yr

Analysis

Strategy I:

build matched filter based on SLAC measurements of bowtie response to Askaryan pulse + lab measured system response

scan all events for coincident pulses consistent with the expected shape

analyzed 2 months of data, but no clear candidates yet

Bowtie response to Askaryan pulse

RF data filtering:

need to digitally filter out RFI; 50-95 MHz and 200-260 MHz bands due to local FM (college radio station next door) and UHF TV stations

To improve our sensitivity, coherently add RF data;
i.e. add sub-threshold events in order to boost SNR

Look for a statistical increase in RF power seen by antennas during triggered events compared to background RF events

So far, analyzed 1 month of data and we have no statistically meaningful result, yet. Better event selection required.

Analysis, cont.

Strategy II:

Summary

The testbed experiment is looking for Askaryan radio pulses induced by cosmic ray secondaries

Built on a shoestring budget ($40-50k), but proving to be essential for hardware development platform for both ANITA and SalSA

Motivated by a good physics goal, not just a technology testbed

Outlook

Data rates are limited by:

RF noise

custom low noise amplifiers

better RF readout with new digitizing chips and cards

place experiment further away from RF noise pollution

Atmospheric depth

move to higher ground for increased particle flux

Size, size, and size

Increase the volume of instrumented salt

coco

2002-08-19T21:13:14