The LUX-ZEPLIN (LZ) Experiment

We describe the design and assembly of the LUX-ZEPLIN experiment, a direct detection search for cosmic WIMP dark matter particles. The centerpiece of the experiment is a large liquid xenon time projection chamber sensitive to low energy nuclear recoils. Rejection of backgrounds is enhanced by a Xe skin veto detector and by a liquid scintillator Outer Detector loaded with gadolinium for efficient neutron capture and tagging. LZ is located in the Davis Cavern at the 4850' level of the Sanford Underground Research Facility in Lead, South Dakota, USA. We describe the major subsystems of the experiment and its key design features and requirements

Identification of Radiopure Titanium for the LZ Dark Matter Experiment and Future Rare Event Searches

The LUX-ZEPLIN (LZ) experiment will search for dark matter particle interactions with a detector containing a total of 10 tonnes of liquid xenon within a double-vessel cryostat. The large mass and proximity of the cryostat to the active detector volume demand the use of material with extremely low intrinsic radioactivity. We report on the radioassay campaign conducted to identify suitable metals, the determination of factors limiting radiopure production, and the selection of titanium for construction of the LZ cryostat and other detector components. This titanium has been measured with activities of $^{238}$U$_{e}$~$<$1.6~mBq/kg, $^{238}$U$_{l}$~$<$0.09~mBq/kg, $^{232}$Th$_{e}$~$=0.28\pm 0.03$~mBq/kg, $^{232}$Th$_{l}$~$=0.25\pm 0.02$~mBq/kg, $^{40}$K~$<$0.54~mBq/kg, and $^{60}$Co~$<$0.02~mBq/kg (68\% CL). Such low intrinsic activities, which are some of the lowest ever reported for titanium, enable its use for future dark matter and other rare event searches. Monte Carlo simulations have been performed to assess the expected background contribution from the LZ cryostat with this radioactivity. In 1,000 days of WIMP search exposure of a 5.6-tonne fiducial mass, the cryostat will contribute only a mean background of $0.160\pm0.001$(stat)$\pm0.030$(sys) counts

LUX-ZEPLIN (LZ) Technical Design Report

In this Technical Design Report (TDR) we describe the LZ detector to be built at the Sanford Underground Research Facility (SURF). The LZ dark matter experiment is designed to achieve sensitivity to a WIMP-nucleon spin-independent cross section of three times ten to the negative forty-eighth square centimeters

LUX-ZEPLIN (LZ) Conceptual Design Report

The design and performance of the LUX-ZEPLIN (LZ) detector is described as of March 2015 in this Conceptual Design Report. LZ is a second-generation dark-matter detector with the potential for unprecedented sensitivity to weakly interacting massive particles (WIMPs) of masses from a few GeV/c2 to hundreds of TeV/c2. With total liquid xenon mass of about 10 tonnes, LZ will be the most sensitive experiment for WIMPs in this mass region by the end of the decade. This report describes in detail the design of the LZ technical systems. Expected backgrounds are quantified and the performance of the experiment is presented. The LZ detector will be located at the Sanford Underground Research Facility in South Dakota. The organization of the LZ Project and a summary of the expected cost and current schedule are given

The LUX-ZEPLIN (LZ) radioactivity and cleanliness control programs

LUX-ZEPLIN (LZ) is a second-generation direct dark matter experiment with spin-independent WIMP-nucleon scattering sensitivity above 1.4×10−48cm2 for a WIMP mass of 40GeV/c2 and a 1000days exposure. LZ achieves this sensitivity through a combination of a large 5.6t fiducial volume, active inner and outer veto systems, and radio-pure construction using materials with inherently low radioactivity content. The LZ collaboration performed an extensive radioassay campaign over a period of six years to inform material selection for construction and provide an input to the experimental background model against which any possible signal excess may be evaluated. The campaign and its results are described in this paper. We present assays of dust and radon daughters depositing on the surface of components as well as cleanliness controls necessary to maintain background expectations through detector construction and assembly. Finally, examples from the campaign to highlight fixed contaminant radioassays for the LZ photomultiplier tubes, quality control and quality assurance procedures through fabrication, radon emanation measurements of major sub-systems, and bespoke detector systems to assay scintillator are presented

Surgical treatment of pelvic organ prolapse: a historical review with emphasis on the anterior compartment

Item does not contain fulltextINTRODUCTION AND HYPOTHESIS: The objective of this work was to collect and summarize a detailed historical review of the surgical treatment of pelvic organ prolapse (POP) in which we specifically focused on the anterior compartment. METHODS: A literature search in English, Dutch, and German was carried out using the keywords pelvic organ prolapse, anterior colporrhaphy, cystocele, and interposition operations in several databases (e.g., PubMed and HathiTrust Digital Library). Other relevant journal and textbook articles were found by retrieving references cited in previous articles and textbooks. RESULTS: Probably the first explanation of the treatment of POP dates from 1500 B.C. The Egyptians gave a description to "falling of the womb" in the Kahun Papyrus. More than a millennium later, Euryphon, a contemporary of Hippocrates (400 B.C.) described some interesting therapeutic options, from succussion (turning a women upside down for several minutes) to irrigating the displaced uterus with wine. A wide range of techniques has been attempted to repair the prolapsing anterior vaginal wall. By 1866, Sim had already performed a series of operations very similar to a modern anterior repair. The first reviews about the abdominal approach to correcting a cystocele were in 1890. The first description of using mesh to cystoceles was the use of tantalum mesh in 1955. In 1970, the first report of collagen mesh in urogynecology was described. Nowadays, robot-assisted surgery and cell-based tissue engineering are the latest interventions. CONCLUSION: Many surgeons have tried to find the ideal surgical therapy for anterior compartment prolapse, but to date, this has not been achieved

A spectrometer for study of high mass objects created in relativistic heavy ion reactions

Experiment E864 at the Brookhaven AGS accelerator uses a high sensitivity, large acceptance spectrometer, designed to search for strangelets and other novel forms of matter produced in high-energy heavy ion collisions. The spectrometer has excellent acceptance and rate capabilities for measuring the production properties of known particles and nuclei such as (p) over bar, (d) over bar and He-6. The experiment uses a magnetic spectrometer and employs redundant time of flight and position detectors and a hadronic calorimeter. In this paper we describe the design and performance of the spectrometer. (C) 1999 Elsevier Science B.V. All rights reserved