CYGNO is an international collaboration with the aim of operating a Image 3 optical time projection chamber (TPC) for directional Dark Matter (DM) searches and solar neutrino spectroscopy, to be deployed at the Laboratori Nazionali del Gran Sasso (LNGS). A Image 1/Image 2 (60/40) mixture is used, along with a triple Gas Electron Multiplier (GEM) cascade to amplify the ionisation signal. The scintillation produced in the electron avalanches is read out using a scientific complementary metal–oxide–semiconductor (sCMOS) camera. This solution has proven to provide very high sensitivity to interactions in the few Image 4 energy range. The inclusion of a hydrogen-based gas will offer an even lighter target, resulting in a more efficient energy transfer in a DM particle collision, and consequently, a lower detection threshold. Additionally, longer track lengths of light nuclear recoils are easier to detect with a clearer direction. However, the addition of such gas will contribute to quenching the scintillation, jeopardizing the TPC performance. In this work, we demonstrate the feasibility of adding 1% to 5% isobutane to the Image 1/Image 2 (60/40) mixture by measuring the respective absolute scintillation yield output. The overall scintillation produced in the charge avalanches is not drastically suppressed by quenching due to the isobutane addition. The presence of Penning transfer from excited He atoms to isobutane molecules increases the number of electrons in the avalanches, partially compensating for the loss of scintillation due to quenching. For the highest applied GEM voltage, the total number of photons produced in the avalanche per Image 4 deposited in the absorption region presents a decrease of only a factor of about three, from <math><mn>2.30</mn><mo>(</mo><mn>20</mn><mo>)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>4</mn></mrow></msup></math> to <math><mn>8.2</mn><mo>(</mo><mn>4</mn><mo>)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>3</mn></mrow></msup></math> Image 5, as the isobutane content increases from 0 to 5%. The quantification of the visible component of the scintillation shows that isobutane quenches both visible and ultraviolet (UV) photons emitted by Image 1/Image 2.

Portugal

F.D. Amaro

Italy

E. Baracchini

L. Benussi

S. Bianco

C. Capoccia

M. Caponero

Brazil

D.S. Cardoso

G. Cavoto

A. Cortez

I.A. Costa

G. D'Imperio

E. Dané

G. Dho

F. Di Giambattista

E. Di Marco

F. Iacoangeli

H.P. Lima Júnior

G.S.P. Lopes

G. Maccarrone

R.D.P. Mano

United Kingdom

R.R. Marcelo Gregorio

D.J.G. Marques

G. Mazzitelli

A.G. McLean

A. Messina

C.M.B. Monteiro

R.A. Nobrega

I.F. Pains

E. Paoletti

L. Passamonti

F. Petrucci

S. Piacentini

D. Piccolo

D. Pierluigi

D. Pinci

A. Prajapati

F. Renga

R. J.d.C. Roque

F. Rosatelli

A. Russo

G. Saviano

N.J.C. Spooner

R. Tesauro

S. Tomassini

S. Torelli

J.M.F. dos Santos

Secondary scintillation yield from GEM electron avalanches in - And - -isobutane for CYGNO — Directional Dark Matter search with an optical TPC

The absolute secondary scintillation yield is of paramount importance for modelling dual-phase or high-pressure gas detectors, to be used in contemporary and in future rare event detection experiments. In addition, the search for neutrinoless double electron capture complements the search for neutrinoless double beta decay and has been measured for $^{124}$Xe in several Dark Matter and Double Beta decay detectors, operating at present. Krypton presents itself as an interesting candidate for double electron capture detection experiments. We have studied the krypton secondary scintillation yield, at room temperature, as a function of electric field in the gas scintillation gap. A large area avalanche photodiode has been used to allow the simultaneous detection of the scintillation pulses as well as the direct interaction of x-rays, the latter being used as a reference for the calculation of the number of charge carriers produced by the scintillation pulses and, thus, the determination of the number of photons impinging the photodiode. An amplification parameter of 113 photons per kV per drifting electron and a scintillation threshold of 2.7 Td (0.7 kVcm$^{−1}$bar$^{−1}$ at 293 K) was obtained, in good agreement with the simulation data reported in the literature. On the other hand, the ionisation threshold in krypton was found to be around 13.5 Td (3.4 kVcm$^{−1}$bar$^{−1}$), less than what had been obtained by the most recent simulation work-package. The krypton amplification parameter is about 80% and 140% of those measured for xenon and argon, respectively.

C.A.O. Henriques

Secondary scintillation yield in pure krypton

In this paper, we describe the XENON100 data analyses used to assess the target-intrinsic background sources radon ( ), thoron ( ) and krypton ( ). We detail the event selections of high-energy alpha particles and decay-specific delayed coincidences. We derive distributions of the individual radionuclides inside the detector and quantify their abundances during the main three science runs of the experiment over a period of ∼4years , from January 2010 to January 2014. We compare our results to external measurements of radon emanation and krypton concentrations where we find good agreement. We report an observed reduction in concentrations of radon daughters that we attribute to the plating-out of charged ions on the negatively biased cathode.

United States

E. Aprile

Netherlands

J. Aalbers

F. Agostini

Germany

M. Alfonsi

M. Anthony

United Arab Emirates

F. Arneodo

Switzerland

P. Barrow

L. Baudis

Sweden

B. Bauermeister

M.L. Benabderrahmane

T. Berger

P.A. Breur

A. Brown

E. Brown

S. Bruenner

G. Bruno

Israel

R. Budnik

L. Bütikofer

J. Calvén

J.M.R. Cardoso

M. Cervantes

D. Cichon

D. Coderre

A.P. Colijn

J. Conrad

France

J.P. Cussonneau

M.P. Decowski

P. de Perio

P. Di Gangi

A. Di Giovanni

S. Diglio

G. Eurin

J. Fei

A.D. Ferella

A. Fieguth

W. Fulgione

A. Gallo Rosso

M. Galloway

F. Gao

M. Garbini

C. Geis

L.W. Goetzke

Z. Greene

C. Grignon

C. Hasterok

E. Hogenbirk

R. Itay

B. Kaminsky

S. Kazama

G. Kessler

A. Kish

H. Landsman

R.F. Lang

D. Lellouch

L. Levinson

Q. Lin

S. Lindemann

M. Lindner

F. Lombardi

J.A.M. Lopes

A. Manfredini

I. Maris

T. Marrodán Undagoitia

J. Masbou

F.V. Massoli

D. Masson

D. Mayani

M. Messina

K. Micheneau

A. Molinario

K. Morå

M. Murra

J. Naganoma

K. Ni

U. Oberlack

P. Pakarha

B. Pelssers

R. Persiani

F. Piastra

J. Pienaar

M.C. Piro

V. Pizzella

G. Plante

N. Priel

D. Ramírez García

L. Rauch

S. Reichard

C. Reuter

A. Rizzo

N. Rupp

G. Sartorelli

M. Scheibelhut

S. Schindler

J. Schreiner

M. Schumann

L. Scotto Lavina

M. Selvi

P. Shagin

Intrinsic backgrounds from Rn and Kr in the XENON100 experiment

The XENON1T dark matter experiment aims to detect weakly interacting massive particles (WIMPs) through low-energy interactions with xenon atoms. To detect such a rare event necessitates the use of radiopure materials to minimize the number of background events within the expected WIMP signal region. In this paper we report the results of an extensive material radioassay campaign for the XENON1T experiment. Using gamma-ray spectroscopy and mass spectrometry techniques, systematic measurements of trace radioactive impurities in over one hundred samples within a wide range of materials were performed. The measured activities allowed for stringent selection and placement of materials during the detector construction phase and provided the input for XENON1T detection sensitivity estimates through Monte Carlo simulations.

D. Franco

L. Grandi

M. Le Calloch

T. Marrodán Undagoitia

B. Miguez

S. Rosendahl

R. Saldanha

Material radioassay and selection for the XENON1T dark matter experiment

The XENON1T experiment at the Laboratori Nazionali del Gran Sasso (LNGS) is the first WIMP dark matter detector operating with a liquid xenon target mass above the ton-scale. Out of its 3.2Â t liquid xenon inventory, 2.0Â t constitute the active target of the dual-phase time projection chamber. The scintillation and ionization signals from particle interactions are detected with low-background photomultipliers. This article describes the XENON1T instrument and its subsystems as well as strategies to achieve an unprecedented low background level. First results on the detector response and the performance of the subsystems are also presented.

B. Antunes

M. Balata

A. Breskin

A. Chiarini

R. Corrieri

J.M. Disdier

M. Doets

E. Duchovni

D. Front

K.L. Giboni

C. Huhmann

A. James

R. Maier

D. Orlandi

R. Othegraven

S. Parlati

The XENON1T dark matter experiment

We describe the purification of xenon from traces of the radioactive noble gas radon using a cryogenic distillation column. The distillation column was integrated into the gas purification loop of the XENON100 detector for online radon removal. This enabled us to significantly reduce the constant 222 Rn background originating from radon emanation. After inserting an auxiliary 222 Rn emanation source in the gas loop, we determined a radon reduction factor of R&gt;27 (95% C.L.) for the distillation column by monitoring the 222 Rn activity concentration inside the XENON100 detector.

Y. Meng

S.E.A. Orrigo

Online 222 Rn removal by cryogenic distillation in the XENON100 experiment

The XENON1T experiment aims for the direct detection of dark matter in a detector filled with 3.3Â tons of liquid xenon. In order to achieve the desired sensitivity, the background induced by radioactive decays inside the detector has to be sufficiently low. One major contributor is the Î² -emitter 85 Kr which is present in the xenon. For XENON1T a concentration of natural krypton in xenon natKr/Xe&lt;200ppq Â (partsÂ perÂ quadrillion,Â 1ppq=10-15mol/mol ) is required. In this work, the design, construction and test of a novel cryogenic distillation column using the common McCabeâThiele approach is described. The system demonstrated a krypton reduction factor of 6.4Â·105 with thermodynamic stability at process speeds above 3Â kg/h. The resulting concentration of natKr/Xe&lt;26ppq is the lowest ever achieved, almost one order of magnitude below the requirements for XENON1T and even sufficient for future dark matter experiments using liquid xenon, such as XENONnT and DARWIN.

Removing krypton from xenon by cryogenic distillation to the ppq level