DMICA: exploring Dark Matter innatural muscovite MICAKASHIWA DARK MATTER SYMPOSIUM 2023
Shigenobu Hirose^1, Kohta Murase^2Natsue Abe^1, Qing Chang^1, Takeshi Hanyu^1, Noriko Hasebe^3,Yasushi Hoshino^4, Takashi Kamiyama^5, Yoji Kawamura^1, Tatsuhiro Naka^6,Kenji Oguni^1, Katsuhiko Suzuki^1, Seiko Yamasaki^7
1: JAMSTEC, 2: Penn State, 3: Kanazawa U, 4: Kanagawa U, 5: Hokkaido U, 6: Toho U, 7: AISTAbstracts

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Searching for dark matter typically requires a large amount of material to capture
extremely rare interactions. However, natural mineral crystals like mica have beenaround for geological time scales, o ering plenty of exposure even in small samples.
These crystals can hold onto nuclear recoil tracks—evidence of dark matterinteractions—for periods longer than the Earth's age. When etched, these tracks
appear as observable pits. Building on this, Snowden-I t and colleagues in 1995
studied natural muscovite mica that was 500 million years old, covering an area ofjust 0.08 square millimeters. We're now planning the DMICA experiment tosigni cantly expand upon this initial research, covering much larger areas. In thispresentation, we'll discuss our preliminary experiments aimed at replicating
Snowden-I t's work as a stepping stone for DMICA. We'll also cover how sensitive
the DMICA experiment could be in detecting dark matter, emphasizing that mica'slarge surface area to volume ratio is particularly useful for detecting very heavy dark
matter particles.

Overview of DM Searchwith Mineral Crystals

Exposure of minerals could potentially rival Xenon experiments
XENON1TDMDM

https://www.danspapers.com/2022/05/olivine-beach-replenishment-questions/2mg ✕ 500 Myr = 1 ton yr

https://xenonexperiment.org/photos/

1.3 ton ✕ 278 day = 1 ton yr
Aprile et al. XENON Collaboration
Phys. Rev. Lett. 121, 111302, 2018

Explore past events in mineral crystals
Recording past events over geological time

Exploring dark matter on a galactic scale

The sun orbits the galactic center
every 200 million years.

Credits: NASA/JPL-Caltech/R. Hurt (SSC/Caltech)https://www.matthewjkelleyauthor.com/timePioneering work using Muscovite mica: Snowden-I t et al. 1995

fffiffFollowing the methodology in Snowden-I t et al, DMICA plans to signi cantly extends theexploration volume beyond theirs, aiming for 1 ton yr

Mechanism of Mica Detector

Recording: recoil nuclei create latent tracks (lattice defects)
TRIM simulation of an oxygen ion (10 keV)traversing through muscovitevacancy• Nuclear recoil is recorded as lattice defects, or

50nm“latent tracks” (invisible to microscopes)• Latent tracks can be preserved longer than the age
track of oxygen ion

50nm

of the EarthReading out: “developing” tracks by etching with HF① Cleaving② Etching with hydro uoric acidtracktrackpitμm

melts overa thickness of 10 nmnm
pit

• Pits of several microns in size and nanometers in depth form at track sites• Relationship between pit formation and recoil energy is relevant for mica to function asfla DM detector

Investigate the relationship between recoil energy and pit
formation by ion irradiation of samples
DMion（keV/u）（vacuum）
nuclei（keV/u） track

Natural muscovite

track

Natural muscovite,
with natural tracks
removed by annealing

Experiments at Kanagawa U

AFM images of ion-irradiated sample surfaces after etchingarXiv:2301.07118
ion energy
O+ 0.63keV/u
total stopping power 355 keV/um

Irradiation dose is
80 particles pereld of view.

O+ 6.3 keV/u435 keV/um

Si+ 0.71keV/u713 keV/um

Ar+ 0.33 keV/u927 keV/um

Kr+ 0.33 keV/u1830 keV/um

Si+ 7.1 keV/u744 keV/um

Ar+ 1 keV/u1009 keV/um

Kr+ 1 keV/u2086 keV/um

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Figure 43: AFM images of etched muscovite irradiated by various species and energies
e ciency, the probability that recoil tracks of atoms+ constituting
muscovite• Mica detector+of ions at Kanagawa University. Upper: from left to right, O 10 keV, Si 20 keV, Ar+(O, Al, Si, K) become pits,is about several % to 10%+
13 keV, and Kr 28 keV. Lower: from left to right, O+ 100 keV, Si+ 200 keV, Ar+ 40 keV,e ciency
tends to increase with higher
stopping power• Detection and+72Kr 84 keV. The dose was 2 ⇥ 10 cm for all cases.
ffifiof 1011 cm 2 at JAEA. Left: Ground after irradiation. Right: Irradiated after grinding(Courtesy of Norito Ishikawa, JAEA).

Sensitivity Evaluation ofMica Detector

Mathematical model describing the relationship between pit
formation and stopping power (Snowden-I t and Chan 1995)
Lower stopping power
lower probability of defect formation
defectdefectparameter↓↓energy↑stopping powerff

Mica layer（1nm）

Higher stopping power
higher probability of defect formation

Mathematical model describing the relationship between pit
formation and stopping power (Snowden-I t and Chan 1995)
Higher stopping power
higher detection e ciency

Lower stopping power
lower detection e ciency
Layers dissolvedby etching

shallower pit

deeper pits

no pits

defect

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• Etched layer defects manifest as pits, illustrating detection e ciency's stopping power reliance• Pit depth, determined by number of defects, is calculable from recoil energy

Calculate pit depth histogram from recoil energy spectrum
Recoil Energy Spectrum using paleoSpec

Monte Caro simulations
basend on
the mathematical modelPit depth histogram

radiogenic neutrons
solar νDM (100GeV)

solar νGSNB νDM (100GeV)

atmospheric νradiogenic neutrons

GSNB νDSNB ν
atmospheric ν
DSNB ν

• Muscovite mica
• age: 500 Myr• Uranium concentration: 0.1ppb• exposure: 1 ton yrPerformance Evaluation of Detector Using Pit Depth Histogram
Likelihood ratio test
using paleoSens

Pit depth histogram

solar νDM (100GeV)

radiogenic neutrons

90% Con dence Detection Limit

Snowden-I t et al. 1995

GSNB νatmospheric νDSNB νfiff• Muscovite mica
• age: 500 Myr• Uranium concentration: 0.1ppb• exposure: 1 ton yr

XENON1T
arXiv: 2303.14729

XENON1T
single scatter
arXiv: 2304.10931

Exploration possible for extremely heavy dark matter
due to high surface area-to-volume ratio

XENON1T(not to scale)

DMICASummary• DMICA experiment utilizes mica as a detector for dark matter:• detects nuclear recoil events with an e ciency ranging from a few to 10%• pit depth histogram re ects the recoil energy spectrum

ffifl• Mica detector possesses unique characteristics:• records ancient events, enabling DM exploration on a galactic scale• geometrically thin nature allows for investigation of extremely heavy DM