Welcome to KU Astroparticle Physics

Jessica, Mark and Dave deploy the first of two radio-frequency LPDA antennas, sensitive from 40-100 MHz, at the experimental site of the TUNKA experiment (Tunka Valley, Siberia).

The KU Astroparticle Physics Program was launched in the early 1990's following Frichter, McKay and Ralston's seminal work on in-ice radiofrequency (RF) neutrino detection FMR, which laid the groundwork for the South Polar RICE experiment RICE06. With our collaborators at the University of Delaware and also the University of Canterbury (Christchurch, NZ)) that experiment first established the feasibility of long wavelength in-ice particle shower detection. Since then, radio-frequency detection of neutrinos, and ultra-high energy cosmic rays in general, has developed into an active, and still growing astroparticle physics sub-discipline.

A general introduction to the field of RadioWave detection of cosmic rays can be found at IntroToRadioWaveCR_Detection

We currently participate in the Askaryan Radio Array (ARA) experiment at the South Pole (short summary at ARA), the Radio Neutrino Observatory-Greenland (RNO-G) at Summit Station, Greenland, the PUEO balloon-borne radio receiver array in Antarctica (under which the KU-based HiCal experiment designed, built and operated HiCal-2 and HiCal-1 ; HiCal-3 recently [Jan, 2026] completed its Antarctic flights ), and the KU-based (led by KU Prof. Prohira) Radar Echo Telescope experiment (RET). We have recently (Sept., 2025) been awarded a 550K grant (thank you, US taxpayers!) to perform high-precision near-surface ice measurements at Summit Station.

Some of the tools we use are nuradiomc simulations of neutrino interactions in-ice, and described in nuradiomc, the ElectromagneticsSimulation (MEEP) code, Steven's paraprop code and also RadioScatter and the antenna simulation code 4nec2; ongoing work includes investigation of radio-frequency propagation of surface waves in our experimental data, design, construction and testing/calibration of antennas, and hardware to measure the density of ice cores and also electric field strengths close to the surface at either Summit Station, Greenland or the South Pole.

The group currently consists of 5 graduate students and several undergrads; we are funded through a combination of National Science Foundation and NASA grants. Recent publications by the graduate students include RadioAntennaPrimer, ARA nu and DoublePulseEvt . Measurements of radiofrequency properties of cold polar ice can be found in Radioglaciology and S11 paper, VolumeScattering as well as physics signals observed in radio detector arrays, including:, RF dielectric msrmnts, Solar Flares

The RET experiment deployed radio receivers at Summit Station, Greenland in 2023 and 2024 and is seeking first-ever detection of ultra-high energy neutrinos based on the RF echoes observed from a neutrino-induced shower. First demonstration of this technique is presented here: RadarTestBeam. More recent results and description of the hardware can be found at RET_recent and DesignPaper

Other experiments with which we have been involved in the past include TARA and TUNKA.

Ongoing Projects/Tasklist:

Data analysis:

=) Investigation of possible surface waves with ARA and RNO-G data: Using either python or C++, analyze signals observed in in-ice antennas as a weather balloon (WB) radiosonde (emitting at 403 MHz) ascends. Measure signal strength as f(WB height), and look for signal enhancement when WB is close to surface. We expect signal to be strongest for antennas closest to surface. By measuring relative signal:noise ratio in multiple receiver stations, we can do a fit to the fraction of 1/r² (volume) and 1/r (surface) flux-spreading. Best if this analysis has surface elevation data available. (DeeDee)

+ Use WB data to measure surface refractive index

=) Extract signal attenuation length from SPICE data, using relative SNR measured in A2 wrt A5 (same propagation direction).

=) Measure random occupancy in ARA or RNO-G data to quantify number of 'fake' hits

=) Software background template 'classifier' / Something like HSV background rejection in firmware

=) Analyze possible effect of borehole closure by examining evolution of response to either deep pulser signals over 2013 to 2022 or looking at frequency response cut in for thermal noise triggers, or cal pulser signals, over same time period.

=) Comparison of various event reconstruction algorithms, originally developed for RICE and ported to other experiments.

=) DP with variable channel-specific dt(S1,S2) times search in RICE/ARA/RNO-g [rj] data / What is the pattern in A(R)/A(D) that we see in surface-reflected data in A1 SPICE/RICE/RNO-G 8/25/RNO-G 8/24 Saltzman hole IDL pulser? There must be some universal description here. (deedee and jaydee remone) - caution: Fresnel zone(λ)

=) rno-g multi-station coincident trigger analysis and triangulate on source and i) measure trigger time resolution, ii) develop background templates (Cassie ramone).

=) PUEO solar reflectivity analysis (MFHS). (mohammad ramone)

=) Finally finish quantification of ARA XPol + Xtalk measurements.

=) Statistically quantify coherence length of density cores from LM and SumUp25 comprehensive density profiles (MA)

=) Extract n(surface) from TIR limit or near surface signals

=) can we decode something about the thermal noise field from interferometry?

=) Comprehensive survey of RNO-G triboelectric events

=) In-situ Gain(elevation) and dedicated double-pulse search in RNO-G (RJ ramone)

Antenna modeling projects:

=) Properties (polarization and S11) of various antennas. Links to previous .nec models can be found in antcal

=) Does spiral antenna have mixed V/H?

HFSS/MEEP FDTD simulation projects:

=) How does antenna beam pattern change in-medium?

=) Are there waveguide effects for antennas in boreholes? If so, how large are they?

=) How does surface roughness effect signals transmitted across air-ice boundary? What is XPol for reflecting off rough surface

Python software/simulation projects:

=) Modeling thermal noise at ARA to try to recover observed trigger rate. (KM20?)

=-) Vostok photogrammetry (/data/user/dbesson/AGAVE_Mirny_Vostok_traverse_data); AGAVE translate to 3d cloud + surface roughness by digitizing surface maps at http://www.pgc.umn.edu/ using digitizing photography

=) CRESIS birefringence and South Pole internal layer reflectivity quantify

=) FAFAIRIE - Fast FAIRIE using known AraSim evolution of SNR_geo(E_primary,θ), SNR_Ask(E_primary,θ)

Hardware/Firmware lab projects:

=) Measure effect of density fluctuations on small microwave antenna signal propagation in lab.

=) Adapt PVA design to HPol/+cable - simulate output

=) Construction of i) acoustic resonator, ii) strain gauge to measure antenna borehole diameter - all data stored on local flash drive. This would be used in May, 2026 at Summit Station, Greenland to produce a map of borehole diameter vs. depth, which would be used in successive years to measure possible borehole closure. Device to measure and log verticality of boreholes

=) Construct optimized pizero-based signal generator and record signal strength for each pulse - the piezo signal generator, we know, is capable of producing multi-kV signals at 10 ns durations. What we'd like to do is to (try, at least to) build a piezo, which is mechanically stressed, with the subsequent relaxation coupled to an antenna which would be used to generate a radio-frequency signal (of use to all of our ultra-high energy neutrino-detection experiments). What is raw piezo signal vs. attached to antenna?

=) Solar-powered device to go into holes to-be-drilled in 2026 and measure temperature profile as f(time). We have received a grant to measure variations in density, as a function of depth, of the ice surface at Summit Station, Greenland. This is part of a broader plan to understand how much ice properties (including temperature, which has so far not been tracked in such detail) vary on a horizontal length scale of 1/10/100 meters. This again has implications for radio-frequency reconstruction of cosmic rays.

=) Melter to get through DISC ice crusts

=) Can we excite surface waves with high-frequency antennas in lab?

=) With a given Tx 2λ above the surface, broadcast to an Rx also >2λ above the surface above a borehole, then measure the signal as the Rx is lowered into the borehole.

CRESIS data analysis

=) Correlation b/w Greenland and Antarctic internal layers

Shameless Self-glorifying music links:

Galactique Acid, with Mark and Andy: https://galactiqueacid.bandcamp.com/

Shannon's Dress, with Chris and Brian, at the Taz, Binghamton, NY: https://www.youtube.com/watch?v=59YkSlimVGg

StarTruck, with Rod and Mic: https://user-web.icecube.wisc.edu/~dbesson/ST/