The PICASSO dark matter search experiment operated an array of 32 superheated droplet detectors containing 3.0 kg of C4F10 and collected an exposure of 231.4 kgd at SNOLAB between March 2012 and January 2014. We report on the final results of this experiment which includes for the first time the complete data set and improved analysis techniques including acoustic localization to allow fiducialization and removal of higher activity regions within the detectors. No signal consistent with dark matter was observed. We set limits for spin-dependent interactions on protons of sigma(SD)(p) = 132 x 10(-2) pb (90% C.L.) at a WIMP mass of 20 GeV/c(2). In the spin-independent sector we exclude cross sections larger than sigma(SI)(p) = 4.86 x 10(-5) pb (90% C.L.) in the region around 7 GeV/c(2). The pioneering efforts of the PICASSO experiment have paved the way forward for a next generation detector incorporating much of this technology and experience into larger mass bubble chambers. (C) 2017 Elsevier B.V. All rights reserved.

The Project In CAnada to Search for Supersymmetric Objects (PICASSO) at SNOLAB searches for Weakly Interacting Massive Particle (WIMP) interactions with 19F. It is particularly sensitive to spin-dependent particle interactions. It uses a droplet technique, based on the principle of a bubble chamber, in which phase transitions in superheated liquids can be triggered by WIMP induced nuclear recoils. The detection process allows a highly efficient suppression of backgrounds from cosmic muons, γ rays and electrons. Recent results and progress are presented and future plans to scale this technique to large masses with the PICO collaboration are briefly discussed.

The Antarctic Muon And Neutrino Detector Array (AMANDA) is a high-energy neutrino telescope based at the geographic South Pole. It is a lattice of photo-multiplier tubes buried deep in the polar ice, which is used as interaction and detection medium. The primary goal of this detector is the observation of astronomical sources of high-energy neutrinos. This paper shows the latest results of the search for a diffuse flux of extraterrestrial ν μ s with energies between 10 11 eV and 10 18 eV, ν μ s emitted from point sources and ν μ s from dark matter annihilation in the Earth and the Sun.

PICASSO at SNOLAB searches primarily for spin-dependent WIMP interactions on F-19 using the superheated droplet technique. This technique is based on the bubble chamber principle, where phase transitions in superheated liquid droplets can be triggered by WIMP induced nuclear recoils. The physics of the detection process allows a highly efficient suppression of backgrounds from cosmic muons, gamma-and beta-rays. We will discuss qualitatively recent progress in PICASSO and its sensitivity reach for spin-dependent and spin-independent WIMP searches.

Recent results from the PICASSO dark matter search experiment at SNOLAB are reported. These results were obtained using a subset of 10 detectors with a total target mass of 0.72 kg of 19F and an exposure of 114 kgd. The low backgrounds in PICASSO allow recoil energy thresholds as low as 1.7 keV to be obtained which results in an increased sensitivity to interactions from Weakly Interacting Massive Particles (WIMPs) with masses below 10 GeV/c2. No dark matter signal was found. Best exclusion limits in the spin dependent sector were obtained for WIMP masses of 20 GeV/c2 with a cross section on protons of σpSD=0.032 pb (90% C.L.). In the spin independent sector close to the low mass region of 7 GeV/c2 favoured by CoGeNT and DAMA/LIBRA, cross sections larger than σpSI=1.41×10−4 pb (90% C.L.) are excluded.

We report new results obtained in calibrations of superheated liquid droplet detectors used in dark matter searches with different radiation sources (n,$\alpha$,$\gamma$). In particular, detectors were spiked with alpha-emitters located inside and outside the droplets. It is shown that the responses are different, depending on whether alpha particles or recoil nuclei create the signals. The energy thresholds for $\alpha$-emitters are compared with test beam measurements using mono-energetic neutrons, as well as with theoretical predictions. Finally a model is presented which describes how the observed intensities of particle induced acoustic signals can be related to the dynamics of bubble growth in superheated liquids. An improved understanding of the bubble dynamics is an important first step in obtaining better discrimination between particle types interacting in detectors of this kind.

The PICASSO experiment at SNOLAB reports new results for spin-dependent WIMP interactions on 19F using the superheated droplet technique. A new generation of detectors and new features which enable background discrimination via the rejection of non-particle induced events are described. First results are presented for a subset of two detectors with target masses of 19F of 65 g and 69 g respectively and a total exposure of 13.75±0.48 kgd. No dark matter signal was found and for WIMP masses around 24 GeV/c2 new limits have been obtained on the spin-dependent cross section on 19F of σF=13.9 pb (90% C.L.) which can be converted into cross section limits on protons and neutrons of σp=0.16 pb and σn=2.60 pb respectively (90% C.L.). The obtained limits on protons restrict recent interpretations of the DAMA/LIBRA annual modulations in terms of spin-dependent interactions.

IceCube is a km-scale neutrino observatory under construction at the South Pole with sensors both in the deep ice (InIce) and on the surface (IceTop). The sensors, called Digital Optical Modules (DOMs), detect, digitize and timestamp the signals from optical Cherenkov-radiation photons. The DOM Main Board (MB) data acquisition subsystem is connected to the central DAQ in the IceCube Laboratory (ICL) by a single twisted copper wire-pair and transmits packetized data on demand. Time calibration is maintained throughout the array by regular transmission to the DOMs of precisely timed analog signals, synchronized to a central GPS-disciplined clock. The design goals and consequent features, functional capabilities, and initial performance of the DOM MB, and the operation of a combined array of DOMs as a system, are described here. Experience with the first InIce strings and the IceTop stations indicates that the system design and performance goals have been achieved.

We present a search for point sources of high energy neutrinos using 3.8 years of data recorded by AMANDA-II during 2000-2006. After reconstructing muon tracks and applying selection criteria designed to optimally retain neutrino-induced events originating in the Northern Sky, we arrive at a sample of 6595 candidate events, predominantly from atmospheric neutrinos with primary energy 100 GeV to 8 TeV. Our search of this sample reveals no indications of a neutrino point source. We place the most stringent limits to date on E{sup -2} neutrino fluxes from points in the Northern Sky, with an average upper limit of E{sup 2}{Phi}{sub {nu}{sub {mu}}+{nu}{sub {tau}}} {le} 5.2 x 10{sup -11} TeV cm{sup -2} s{sup -1} on the sum of {nu}{sub {mu}} and {nu}{sub {tau}} fluxes, assumed equal, over the energy range from 1.9 TeV to 2.5 PeV.

The PICASSO experiment searches WIMPs via their spin‐dependent interactions with nuclei. At their operating temperatures, PICASSO threshold detectors are not sensitive to γ‐rays, while it is necessary to suppress neutron and α‐ray backgrounds. The different types of neutron shielding (water, polyethylene, borated water and polyethylene doped with different compounds of boron and lithium) were studied via the Monte Carlo method using MCNPX code. Efficiencies of these different types of neutron shielding were compared from the point of view of neutron suppression as well as number of newly born y‐rays. The neutrons and γ‐rays were followed up to the PICASSO detector active material. The most suitable neutron shielding for the PICASSO experiment was determined following these simulations.

A search for TeV-PeV muon neutrinos from unresolved sources was performed on AMANDA-II data collected between 2000 and 2003 with an equivalent live time of 807 days. This diffuse analysis sought to find an extraterrestrial neutrino flux from sources with nonthermal components. The signal is expected to have a harder spectrum than the atmospheric muon and neutrino backgrounds. Since no excess of events was seen in the data over the expected background, an upper limit of E-2 Phi(90%C.L.)< 7.4x10(-8) GeV cm(-2) s(-1) sr(-1) is placed on the diffuse flux of muon neutrinos with a Phi proportional to E-2 spectrum in the energy range 16 TeV to 2.5 PeV. This is currently the most sensitive Phi proportional to E-2 diffuse astrophysical neutrino limit. We also set upper limits for astrophysical and prompt neutrino models, all of which have spectra different from Phi proportional to E-2.

In order to increase the accelerating gradient, the next-generation of Superconducting Radio Frequency (SRF) cavities will be operated with superfluid helium cooling. This upgrade requires the development of a state-of-the-art cryogenic temperature mapping system, which can be used to identify quench initiation in new cavities, and thereby assess their suitability for installation. This paper presents a new mapping system based on an array of Transition Edge Sensors (TESs): electrical devices that exploit the superconducting transition of a thin film to identify temperature changes.The TES array is manufactured using photolithography to deposit a thin film on a 100 mm diameter glass wafer. Two different designs of Au-Sn TES have been assessed; Design 1 was composed of a 10 nm Cr adhesive layer, followed by 20 nm of Au and 100 nm of Sn, and Design 2 was identical except that the Cr layer was not applied.Design 1 showed excellent film adherence, however no superconducting transition was observed. In contrast, Design 2 showed poor film bonding but a superconducting transition. These insights are being used to design a new cryogenic temperature mapping device that combines Design 1 for robust electrical contacts and Design 2 for second sound detection.

IceCube is a new high-energy neutrino telescope which will be coming online in the near future.IceCube will be capable of measuring fluxes of all three flavors of neutrino, and its peak neutrino energy sensitivity will be in the TeV-PeV range.Here, after a brief description of the detector, we describe its anticipated performance with a selection of physics topics: supernovae, extraterrestrial diffuse and point sources of neutrinos, gamma-ray bursts, neutrinos from WIMP annihilation, and cosmic ray composition.

The PICASSO collaboration observed for the first time a significant difference between the acoustic signals induced by neutrons and alpha particles in a detector based on superheated liquids. This new discovery offers the possibility of improved background suppression and could be especially useful for dark matter experiments. This new effect may be attributed to the formation of multiple bubbles on alpha tracks, compared to single nucleations created by neutron-induced recoils.

On 2006 December 13 the IceTop air shower array at the South Pole detected a major solar particle event. By numerically simulating the response of the IceTop tanks, which are thick Cerenkov detectors with multiple thresholds deployed at high altitude with no geomagnetic cutoff, we determined the particle energy spectrum in the energy range 0.6-7.6 GeV. This is the first such spectral measurement using a single instrument with a well-defined viewing direction. We compare the IceTop spectrum and its time evolution with previously published results and outline plans for improved resolution of future solar particle spectra.

A search for TeV-PeV muon neutrinos with AMANDA-II data collected between 2000 and 2003 established an upper limit of E 2 90%C:L: < 7:4 10 ÿ8 GeV cm ÿ2 s ÿ1 sr ÿ1 on the diffuse flux of extraterrestrial muon neutrinos with a / E ÿ2 spectrum between 16 TeV and 2.5 PeV.The upper limit calculation correctly included event simulations and remains as stated.However, the calculation of the detector's efficiency, which is based only on simulations, was incorrectly tabulated in an appendix and shown in a figure.The values were approximately a factor of 10 too high, although the exact error varies in each bin.The correction has been applied in Tables I and II and Fig. 1.The effective area is the equivalent area over which the detector would be 100% efficient for detecting neutrinos.The typical uncertainty on the effective area from simulation statistics is lowest between 10 5 GeV and 10 6 GeV (2%).The uncertainty increases to 6% at 10 4 GeV and 5% around 10 7 GeV.In the remainder of this document, the number of optical modules (OMs) triggered during an event is referred to as N ch and cos t refers to the cosine of the simulated (true) zenith angle of an event.The term angle-averaged indicates that results are averaged over t between 100 and 180 .All other results reported in the paper, including the upper limit, remain unchanged.

A search for diffuse neutrinos with energies in excess of 105 GeV is conducted with AMANDA-II data recorded between 2000 and 2002. Above 107 GeV, the Earth is essentially opaque to neutrinos. This fact, combined with the limited overburden of the AMANDA-II detector (roughly 1.5 km), concentrates these ultra-high-energy neutrinos at the horizon. The primary background for this analysis is bundles of downgoing, high-energy muons from the interaction of cosmic rays in the atmosphere. No statistically significant excess above the expected background is seen in the data, and an upper limit is set on the diffuse all-flavor neutrino flux of E2Φ90% CL < 2.7 × 10−7 GeV cm−2 s−1 sr−1 valid over the energy range of 2 × 105 to 109 GeV. A number of models that predict neutrino fluxes from active galactic nuclei are excluded at the 90% confidence level.

The IceCube neutrino detector is a cubic kilometer TeV to PeV neutrino detector under construction at the geographic South Pole. The dominant population of neutrinos detected in IceCube is due to meson decay in cosmic-ray air showers. These atmospheric neutrinos are relatively well understood and serve as a calibration and verification tool for the new detector. In 2006, the detector was approximately 10% completed, and we report on data acquired from the detector in this configuration. We observe an atmospheric neutrino signal consistent with expectations, demonstrating that the IceCube detector is capable of identifying neutrino events. In the first 137.4 days of livetime, 234 neutrino candidates were selected with an expectation of 211 {+-} 76.1(syst.) {+-} 14.5(stat.) events from atmospheric neutrinos.

We report the results of a five-year survey of the northern sky to search for point sources of high energy neutrinos. The search was performed on the data collected with the AMANDA-II neutrino telescope in the years 2000 to 2004, with a live time of 1001 days. The sample of selected events consists of 4282 upward going muon tracks with high reconstruction quality and an energy larger than about 100 GeV. We found no indication of point sources of neutrinos and set 90% confidence level flux upper limits for an all-sky search and also for a catalog of 32 selected sources. For the all-sky search, our average (over declination and right ascension) experimentally observed upper limit Phi(0)=(E/1 TeV)(gamma)center dot d Phi/dE to a point source flux of muon and tau neutrino (detected as muons arising from taus) is Phi(nu mu)+nu(0)(mu)+Phi(nu tau)+nu(0)(tau)=11.1x 10(-11) TeV-1 cm(-2) s(-1), in the energy range between 1.6 TeV and 2.5 PeV for a flavor ratio Phi(nu mu)+nu(0)(mu)/Phi(nu tau)+nu(0)(tau)=1 and assuming a spectral index gamma=2. It should be noticed that this is the first time we set upper limits to the flux of muon and tau neutrinos. In previous papers we provided muon neutrino upper limits only neglecting the sensitivity to a signal from tau neutrinos, which improves the limits by 10% to 16%. The value of the average upper limit presented in this work corresponds to twice the limit on the muon neutrino flux Phi(nu mu)+nu(0)(mu)=5.5x10(-11) TeV-1 cm(-2) s(-1). A stacking analysis for preselected active galactic nuclei and a search based on the angular separation of the events were also performed. We report the most stringent flux upper limits to date, including the results of a detailed assessment of systematic uncertainties.