Backgrounds/Interference, etc: Lessons from RICE expt, OR: Everything We Did Wrong

• Due to limitations, will have to be selective. Will cover blunders, boners, bungles, plain dumb moves, egregious errors, faux pas, major goofs, howlers, tragic mistakes, blanket failures, gross miscalculations and original sins

• Will have to omit garden-variety errors, lapses, misbeliefs, gaffes, slipups, glitches, misjudgments and screw-ups…

RICE data-taking >1999/16 Rx/<50K/yr budget

RICERICE

SPASE

Structural Deficiencies: RICE-I• Filter directly @antenna output (into in-ice LNA)• As much gain as possible in-ice vs. surface• Multi-tiered trigger: hierarchy of localglobal

triggering (frequency/pol. banding a la’ ANITA)• High-Amplitude veto @L0!• Resist inclination towards symmetry – deploy

antennas @unique (x,y,z): avoid reconstruction ambiguities. (-entirely xy-planar array has no theta=0 vs. theta=180 discrimination)

• Geometric lever arm as (more?) important than squeezing on timing resolution

Justin MC file:

200x500m array (dt=5ns)

1500x1000m array (dt=10ns; red) v

1500x1000m array (dt=30ns; blue, shaded)

Physics BackgroundsRadio threshold above atmospheric neutrinos:

GOOD – NO NEED TO STATISTICALLY SUBTRACT ATMOSPHERIC NEUTRINO EVENTS (AS W/ AMANDA/ICECUBE) BAD – NO CONVINCING “CALIBRATION” SIGNAL Need to nail down charm component of atm. nu flux.

RICE/SalSA threshold above e+eW resonance (6.4 PeV)Muon bremstrahlung signals, e.g? Ped/RadovanAir Shower coincidences good, mebbe not possible with SalSA

Surface Backgroundsnot same as SALSA - Water above dome provides

RF insulation against surface-generated backgrounds! (Tholian Web)

• Anthropogenic Activity –– Long time-over-threshold, multiple bursts, narrow

band, etc… (waveforms look like…)• Solar Flares

– Still under study – no obvious correlation with, e.g., 29Sept04 flare, but work continuing…

• What-Not• In practice, ~60% of triggers (rest thermal)

“Irreducible” Backgrounds• Thermal noise: plot distribution of Voltages

Voltages for Random triggers; Solid=t1

Dashed=t2

Generally Gaussian, with coherent drifts in amplitude

Or plot distribution of 4-hit verticesVertices in random triggers – if thermalvertices

populate region determined by light x-ing time

And modelable…

Solid=Data

Points=MC

Data bias towards center not understood…

“Other Stuff”• Events-most-likely-to-pass-software+hardware

filters: – 3- or 4-hit surface triggers + random hit in channel 15

(deep channel)– Channel 15 deeper (x2) than most other channels, so

disproportionately weights reconstructed vertex– Identified by large timing residual in channel 15.– Annoying, but identifiable.

• Simple (previous) model of fast, all-hardware trigger no longer feasible. To squeeze sensitivity, will need firmware @L1/L2

Raw (online) vertex distribution, all triggers, last week of Jan 05

General CommentWithout a measurable physics background,

imperative to demonstrate that, environment, as well as all other backgrounds are understood in order to convince community that experiment “works”

(Halzen & Hooper: astro-ph/0310152: “IceCube-Plus: A UHE Nu Telescope”

“Unlike other proposals (sic: radio/acoustic), the expanded detector uses methods that are understood and calibrated on atmospheric neutrinos”)

Ray Tracing:”Characterize thy medium”

Well-known from a) WWII submarine warfare, b) failed attempts to broadcast TxRx horizontally 03-04 (JiWoo&dzb), c) Justin et al. SAUND calculations, d) many radiowave ray tracing calculations, rays refract towards v

Since some of current RICE receivers in upper ice (150 m depth), this costs effective volume; lesson: Deploy in “focussed” regions, or (to avoid ray-tracing headaches) in v=constant region

n(z)

Shadowing

Shadow region

Acceptance region

Results of MC simulation

Limited by attenuation

60,000 e- showers at E = 1 EeVBlack dots – sampleRed dots – events which would trigger RICE

~ 5% efficiency

Limited by Čerenkov angle

Hit distributions with raytracing

Old vs. New (corrected ray-tracing) effective volume

(also includes other mods; ray tracing ~50% of hit in Veff)

Aside: “The energy has to go somewhere”. Compensating effect of caustics, or after-pulses NOT included in Veff calc.

Absorption (Im(eps)) at SP

Temperature Profiles

How well is dielectric constant known for salt? domes?

• Expect that density of salt should be constant with depth (~2.2 gm/cc)– Hockley: 98.4% halite (PG: 95%?)

• Need data on Re(m as f(pressure,Temp,frequency,density)

• DC limit: Re(eps)=5.354+0.001833T (NBS Monograph 167, “Physical Properties Data for Rock Salt”)

• Typically, 1 degree C per 40 m depth http://www.oilfield.slb.com/media/resources/oilfieldreview/ors95/jan95/01950422.pdf

Temperature Dependence

Density Profile

Summary• Key is long attenuation length and large Veff

• SalSA surface backgrounds should be more tractable – can we drop an antenna+digital scope into a borehole now??

• Radio landscape much different than 10 yrs ago: SalSA will benefit considerably from collective GLUE/RICE/ANITA experience in DAQ design

• In absence of physics background, must still do more characterization of environment + backgrounds (IMHO)

Transmitter Location Reconstruction

True (known)

Transmitter Depth

Tx → Rx simulation vs. data

data

simulated