Measurement of the Permanent Electric Dipole Moment of the Neutron.

We present the result of an experiment to measure the electric dipole moment (EDM) of the neutron at the Paul Scherrer Institute using Ramsey's method of separated oscillating magnetic fields with ultracold neutrons. Our measurement stands in the long history of EDM experiments probing physics violating time-reversal invariance. The salient features of this experiment were the use of a ^{199}Hg comagnetometer and an array of optically pumped cesium vapor magnetometers to cancel and correct for magnetic-field changes. The statistical analysis was performed on blinded datasets by two separate groups, while the estimation of systematic effects profited from an unprecedented knowledge of the magnetic field. The measured value of the neutron EDM is d_{n}=(0.0±1.1_{stat}±0.2_{sys})×10^{-26} e.cm.

Observation of Gravitationally Induced Vertical Striation of Polarized Ultracold Neutrons by Spin-Echo Spectroscopy.

We describe a spin-echo method for ultracold neutrons (UCNs) confined in a precession chamber and exposed to a |B0|=1 µT magnetic field. We have demonstrated that the analysis of UCN spin-echo resonance signals in combination with knowledge of the ambient magnetic field provides an excellent method by which to reconstruct the energy spectrum of a confined ensemble of neutrons. The method takes advantage of the relative dephasing of spins arising from a gravitationally induced striation of stored UCNs of different energies, and also permits an improved determination of the vertical magnetic-field gradient with an exceptional accuracy of 1.1 pT/cm. This novel combination of a well-known nuclear resonance method and gravitationally induced vertical striation is unique in the realm of nuclear and particle physics and should prove to be invaluable for the assessment of systematic effects in precision experiments such as searches for an electric dipole moment of the neutron or the measurement of the neutron lifetime.

Achieving ultra-low and -uniform residual magnetic fields in a very large magnetically shielded room for fundamental physics experiments.

High-precision searches for an electric dipole moment of the neutron (nEDM) require stable and uniform magnetic field environments. We present the recent achievements of degaussing and equilibrating the magnetically shielded room (MSR) for the n2EDM experiment at the Paul Scherrer Institute. We present the final degaussing configuration that will be used for n2EDM after numerous studies. The optimized procedure results in a residual magnetic field that has been reduced by a factor of two. The ultra-low field is achieved with the full magnetic-field-coil system, and a large vacuum vessel installed, both in the MSR. In the inner volume of ∼1.4m3, the field is now more uniform and below 300 pT. In addition, the procedure is faster and dissipates less heat into the magnetic environment, which in turn, reduces its thermal relaxation time from 12h down to 1.5h.

A large 'Active Magnetic Shield' for a high-precision experiment: nEDM collaboration.

We present a novel Active Magnetic Shield (AMS), designed and implemented for the n2EDM experiment at the Paul Scherrer Institute. The experiment will perform a high-sensitivity search for the electric dipole moment of the neutron. Magnetic-field stability and control is of key importance for n2EDM. A large, cubic, 5 m side length, magnetically shielded room (MSR) provides a passive, quasi-static shielding-factor of about 105 for its inner sensitive volume. The AMS consists of a system of eight complex, feedback-controlled compensation coils constructed on an irregular grid spanned on a volume of less than 1000 m3 around the MSR. The AMS is designed to provide a stable and uniform magnetic-field environment around the MSR, while being reasonably compact. The system can compensate static and variable magnetic fields up to ±50µT (homogeneous components) and ±5µT/m (first-order gradients), suppressing them to a few µT in the sub-Hertz frequency range. The presented design concept and implementation of the AMS fulfills the requirements of the n2EDM experiment and can be useful for other applications, where magnetically silent environments are important and spatial constraints inhibit simpler geometrical solutions.

The very large n2EDM magnetically shielded room with an exceptional performance for fundamental physics measurements.

We present the magnetically shielded room (MSR) for the n2EDM experiment at the Paul Scherrer Institute, which features an interior cubic volume with each side of length 2.92 m, thus providing an accessible space of 25 m3. The MSR has 87 openings of diameter up to 220 mm for operating the experimental apparatus inside and an intermediate space between the layers for housing sensitive signal processing electronics. The characterization measurements show a remanent magnetic field in the central 1 m3 below 100 pT and a field below 600 pT in the entire inner volume, up to 4 cm to the walls. The quasi-static shielding factor at 0.01 Hz measured with a sinusoidal 2 µT peak-to-peak signal is about 100 000 in all three spatial directions and increases rapidly with frequency to reach 108 above 1 Hz.

Measurement of linear stark interference in 199Hg.

We present measurements of Stark interference in the (61)S(0)→6(3)P(1) transition in (199)Hg, a process whereby a static electric field E mixes magnetic dipole and electric quadrupole couplings into an electric dipole transition, leading to E-linear energy shifts similar to those produced by a permanent atomic electric dipole moment (EDM). The measured interference amplitude, a(SI) = (a(M1) + a(E2)) = (5.8 ± 1.5) × 10(-9) (kV / cm)(-1), agrees with relativistic, many-body predictions and confirms that earlier central-field estimates are a factor of 10 too large. More importantly, this study validates the capability of the (199)Hg EDM search apparatus to resolve nontrivial, controlled, and sub-nHz Larmor frequency shifts with EDM-like characteristics.

The design of the n2EDM experiment: nEDM Collaboration.

We present the design of a next-generation experiment, n2EDM, currently under construction at the ultracold neutron source at the Paul Scherrer Institute (PSI) with the aim of carrying out a high-precision search for an electric dipole moment of the neutron. The project builds on experience gained with the previous apparatus operated at PSI until 2017, and is expected to deliver an order of magnitude better sensitivity with provision for further substantial improvements. An overview is of the experimental method and setup is given, the sensitivity requirements for the apparatus are derived, and its technical design is described.

Cosmic Ray Background Removal With Deep Neural Networks in SBND.

In liquid argon time projection chambers exposed to neutrino beams and running on or near surface levels, cosmic muons, and other cosmic particles are incident on the detectors while a single neutrino-induced event is being recorded. In practice, this means that data from surface liquid argon time projection chambers will be dominated by cosmic particles, both as a source of event triggers and as the majority of the particle count in true neutrino-triggered events. In this work, we demonstrate a novel application of deep learning techniques to remove these background particles by applying deep learning on full detector images from the SBND detector, the near detector in the Fermilab Short-Baseline Neutrino Program. We use this technique to identify, on a pixel-by-pixel level, whether recorded activity originated from cosmic particles or neutrino interactions.

Single inhalation exposure to 90SrCl2 in the beagle dog: late biological effects.

Late-occurring biologic effects were studied in beagle dogs that were given graded levels of 90SrCl2 via single brief inhalation exposures and were subsequently observed for their life-span. Due to the soluble chemical form of the aerosol, 90Sr was rapidly translocated from lung and deposited in bone where it was subsequently retained for a long period of time. Radiation-induced lesions were confined to the bone, bone marrow, and adjacent soft tissue. Forty-five primary bone tumors occurred in 31 of 66 exposed dogs. Metastasis occurred from 21 tumors, with the lung being the most frequent site of metastasis (76%). Twenty-seven tumors were classified as different subtypes of osteosarcoma, 14 as hemangiosarcomas, 3 as fibrosarcomas, and 1 as a myxosarcoma. Four carcinomas arising from soft tissues adjacent to bone were also considered to be 90Sr induced. In contrast to bone tumors arising in beagles chronically exposed to 90Sr through ingestion, histologic lesions of radiation osteodystrophy were minimal in this study, indicating that these lesions are not a necessary precursor of osteosarcoma development. The incidences of hemangiosarcomas (31%) and telangiectatic osteosarcomas (11%) in addition to osteosarcomas suggest that the cell of origin for all of these neoplasms is a multipotent mesenchymal cell with the potential for various morphologic expressions dependent on local environmental factors.

An apparatus for studying electrical breakdown in liquid helium at 0.4 K and testing electrode materials for the neutron electric dipole moment experiment at the Spallation Neutron Source.

We have constructed an apparatus to study DC electrical breakdown in liquid helium at temperatures as low as 0.4 K and at pressures between the saturated vapor pressure and ∼600 Torr. The apparatus can house a set of electrodes that are 12 cm in diameter with a gap of 1-2 cm between them, and a potential up to ±50 kV can be applied to each electrode. Initial results demonstrated that it is possible to apply fields exceeding 100 kV/cm in a 1 cm gap between two electropolished stainless steel electrodes 12 cm in diameter for a wide range of pressures at 0.4 K. We also measured the current between two electrodes. Our initial results, I < 1 pA at 45 kV, correspond to a lower bound on the effective volume resistivity of liquid helium of ρV > 5 × 10(18) Ω cm. This lower bound is 5 times larger than the bound previously measured. We report the design, construction, and operational experience of the apparatus, as well as initial results.

A systems-based computational model for dose-response comparisons of two mode of action hypotheses for ethanol-induced neurodevelopmental toxicity.

Investigations into the potential mechanisms for ethanol-induced developmental toxicity have been ongoing for over 30 years since Fetal Alcohol Syndrome (FAS) was first described. Neurodevelopmental endpoints are particularly sensitive to in utero exposure to alcohol as suggested by the more prevalent alcohol-related neurodevelopmental disorder (ARND). The inhibition of proliferation during neurogenesis and the induction of apoptosis during the period of synaptogenesis have been identified as potentially important mechanisms for ARND. However, it is unclear how these two mechanisms quantitatively relate to the dose and timing of exposure. We have extended our model of neocortical neurogenesis to evaluate apoptosis during synaptogenesis. This model construct allows quantitative evaluation of the relative impacts on neuronal proliferation versus apoptosis during neocortical development. Ethanol-induced lengthening of the cell cycle of neural progenitor cells during rat neocortical neurogenesis (G13-G19) is used to compute the number of neurons lost after exposure during neurogenesis. Ethanol-induced dose-dependent increases in cell death rates are applied to our apoptosis model during rat synaptogenesis (P0-P14), when programmed cell death plays a major role in shaping the future neocortex. At a human blood ethanol concentration that occurs after 3-5 drinks ( approximately 150 mg/dl), our model predicts a 20-30% neuronal deficit due to inhibition of proliferation during neurogenesis, while a similar exposure during synaptogenesis suggests a 7-9% neuronal loss through induction of cell death. Experimental in vitro and in vivo dose-response research and stereological research on long-term neuronal loss after developmental exposure to ethanol is compared to our model predictions. Our computational model allows for quantitative, systems-level comparisons of mechanistic hypotheses for perturbations during specific neurodevelopmental periods.

Sites of particle retention and lung tissue responses to chronically inhaled diesel exhaust and coal dust in rats and cynomolgus monkeys.

The usefulness of pulmonary carcinogenicity data from rats exposed to high concentrations of particles for quantitatively predicting lung cancer risk in humans exposed to much lower environmental or occupational concentrations has been questioned. The results of several chronic inhalation bioassays of poorly soluble, nonfibrous particles have suggested that rats may be more prone than other rodent species to develop persistent pulmonary epithelial hyperplasia, metaplasia, and tumors in response to the accumulation of inhaled particles. In addition, rats and primates differ in their pulmonary anatomy and rate of particle clearance from the lung. This paper reviews results of recent Lovelace Respiratory Research Institute (Albuquerque, NM) investigations that directly compared the anatomical patterns of particle retention and the lung tissue responses of rats and monkeys exposed chronically to high occupational concentrations of poorly soluble particles. Lung sections from male cynomolgus monkeys and F344 rats exposed 7 hr/day, 5 days/week for 24 months to filtered ambient air, diesel exhaust (2 mg soot/m3), coal dust (2 mg respirable particulate material/m3), or diesel exhaust and coal dust combined (1 mg soot and 1 mg respirable coal dust/m3) were obtained from a study conducted at the U.S. National Institute for Occupational Safety and Health and examined histopathologically and morphometrically. Within each species, the sites of particle retention and lung tissue responses were the same for diesel soot, coal dust, and combined material. Rats retained a significantly greater portion of the particulate material in the lumens of alveolar ducts and alveoli than monkeys. Conversely, monkeys retained a significantly greater portion of the particulate material in the interstitium than rats. Rats, but not monkeys, had significant alveolar epithelial hyperplastic, inflammatory, and septal fibrotic responses to the retained particles. These results suggest that anatomic patterns of particle retention and lung tissue reactions in rats may not be predictive of retention patterns and tissue responses in primates that inhale poorly soluble particles at concentrations representing high occupational exposures.

The effect of dose, dose rate, route of administration, and species on tissue and blood levels of benzene metabolites.

Studies were completed in F344/N rats and B6C3F1 mice to determine the effect of dose, dose rate, route of administration, and rodent species on formation of total and individual benzene metabolites. Oral doses of 50 mg/kg or higher saturated the capacity for benzene metabolism in both rats and mice, resulting in an increased proportion of the administered dose being exhaled as benzene. The saturating air concentration for benzene metabolism during 6-hr exposures was between 130 and 900 ppm. At the highest exposure concentration, rats exhaled approximately half of the internal dose retained at the end of the 6-hr exposure as benzene; mice exhaled only 15% as benzene. Mice were able to convert more of the inhaled benzene to metabolites than were rats. In addition, mice metabolized more of the benzene by pathways leading to the putative toxic metabolites, benzoquinone and muconaldehyde, than did rats. In both rats and mice, the effect of increasing dose, administered orally or by inhalation, was to increase the proportion of the total metabolites that were the products of detoxification pathways relative to the products of pathways leading to putative toxic metabolites. This indicates low-affinity, high-capacity pathways for detoxification and high-affinity, low-capacity pathways leading to putative toxic metabolites. If the results of rodent studies performed at high doses were used to assess the health risk at low-dose exposures to benzene, the toxicity of benzene would be underestimated.

Animal models of beryllium-induced lung disease.

The inhalation Toxicology Research Institute (ITRI) is conducting research to improve the understanding of chronic beryllium disease (CBD) and beryllium-induced lung cancer. Initial animal studies examined beagle dogs that inhaled BeO calcined at either 500 or 1000 degrees C. At similar lung burdens, the 500 degrees C BeO induced more severe and extensive granulomatous pneumonia, lymphocytic infiltration into the lung, and positive Be-specific lymphocyte proliferative responses in vitro than the 1000 degrees C BeO. However, the progressive nature of human CBD was not duplicated. More recently, Strains A/J and C3H/Hej mice were exposed to Be metal by inhalation. This produced a marked granulomatous pneumonia, diffuse infiltrates, and multifocal aggregates of interstitial lymphocytes with a pronounced T helper component and pulmonary in situ lymphocyte proliferation. With respect to lung cancer, at a mean lung burden as low as 17 micrograms Be/g lung, inhaled Be metal induced benign and/or malignant lung tumors in over 50% of male and female F344 rats surviving > or = 1 year on study. Substantial tumor multiplicity was found, but K-ras and p53 gene mutations were virtually absent. In mice, however, a lung burden of approximately 60 micrograms (-300 micrograms Be/g lung) caused only a slight increase in crude lung tumor incidence and multiplicity over controls in strain A/J mice and no elevated incidence in strain C3H mice. Taken together, this research program constitutes a coordinated effort to understand beryllium-induced lung disease in experimental animal models.

Biological effects of inhaled 144CeCl3 in beagle dogs.

The biological effects of 144Ce were studied in beagle dogs that were exposed to graded activity levels of 144CeCl3 via a single, brief inhalation exposure and observed for their life span. The long-term retained body burdens ranged from 0.06 to 13 MBq/kg with a median of 1.2 MBq/kg. After a short residence time in the lung, most of the 144Ce was translocated to liver and skeleton, where the 144Ce was retained with a half-time approaching the physical half-life of 144Ce, 284 days. Significant radiation doses were delivered to the lung, 28 Gy (median) and 2.5-370 Gy (range); liver, 68 Gy (median) and 6.1-250 Gy (range); and skeleton, 21 Gy (median) and 1.9-100 Gy (range). Lesions induced by the beta-particle radiation were noted in the lung, liver, skeleton, bone marrow, and oral and nasal mucosae closely associated with bone. Early deaths (within 2.5 years) were generally related to hematological dyscrasia, radiation pneumonitis, or hepatocellular degeneration and atrophy. Neoplasms that occurred relatively early, from 2.2-6.8 years after exposure, were noted in the liver, bone, bone marrow and oral mucosa closely associated with bone. Neoplasms that occurred later, beyond 7 years after exposure, were noted in the liver, lung and nasal mucosa closely associated with bone. Increased numbers of neoplasms were not found in two other organs that had relatively high radiation doses, namely the thyroid and kidney. Only one primary bone tumor was noted, but 11 tumors of bone-associated tissues (oral and nasal mucosae and bone marrow) were found. Radiation doses and effects in tissues adjacent to bone, especially those of epithelial or marrow origin, should be considered when determining risks from internally deposited bone-seeking radionuclides, such as 144Ce. The property of 144Ce in depositing on and remaining associated with bone surfaces for long times may be an important factor in the radiation dose to bone marrow and epithelium adjacent to bone.

The induction of chromosome damage in CHO cells by beryllium and radiation given alone and in combination.

Studies were conducted to determine the effects of BeSO4 or X rays, alone and in combination, on cell cycle kinetics, cell killing, and the production of chromosome aberrations in Chinese hamster ovary (CHO) cells. The concentration of BeSO4 required to kill 50% of CHO cells exposed to BeSO4 for 20 h was determined to be 1.1 mM with 95% confidence intervals of 0.72 to 1.8 mM. During the last 2 h of the 20-h beryllium treatment (0.2 and 1.0 mM), cells were exposed to 0.0, 1.0, or 2.0 Gy of X rays. Exposure to either BeSO4 or X rays produced a change in cell cycle kinetics which resulted in an accumulation of cells in the G2/M stage of the cell cycle. However, combined exposure to both agents resulted in a block similar to that observed following exposure to X rays only. The background level of chromosome damage was 0.05 +/- 0.015 aberrations/cell in the CHO cells. Seven hours after the end of exposure to 0.2 and 1.0 mM beryllium, 0.03 +/- 0.003 and 0.09 +/- 0.02 aberrations/cell, respectively, were observed. The data for chromosome aberrations following X-ray exposure were fitted to a linear model with a coefficient of 0.14 +/- 0.01 aberrations/cell/Gy. When beryllium was combined with the X-ray exposure the interactive response was predicted by a multiplicative model and was significantly higher (P less than 0.05) than predicted by an additive model. The influence of time after radiation exposure on the interaction between beryllium and X rays was also determined. No interaction between beryllium and X-ray exposure in the induction of chromosome-type aberrations (P greater than 0.05) was detected. The frequency of chromatid-type exchanges and total aberrations was significantly higher (P less than 0.05) in the radiation plus beryllium-exposed cells when compared to cells exposed to X rays only, at both 9 and 12 h after X-ray exposure. These data suggest that the multiplicative interaction may be limited to cells in the S and G2 stages of the cell cycle.

The biological effects of radium-224 injected into dogs.

A life-span study was conducted in 128 beagle dogs to determine the biological effects of intravenously injected 224Ra chloride. The 224Ra chloride was prepared by the same method used for intravenous injections in humans who were treated for ankylosing spondylitis and tuberculosis. Thus the results obtained from dogs can be compared directly to the population of treated humans, both for the elucidation of the effect of exposure rate and for comparison with other radionuclides for which data for humans are unavailable. Using equal numbers of males and females, the dogs were injected with one of four levels of 224Ra resulting in initial body burdens of approximately 13, 40, 120 or 350 kBq of 224Ra kg-1 body mass. A control group of dogs was injected with diluent only. All dogs were divided further into three groups for which the amount of injected 224Ra (half-life of 3.62 days) or diluent was given in a single injection or divided equally into 10 or 50 weekly injections. As a result of these three injection schedules, the accumulation of dose from the injected 224Ra was distributed over approximately 1, 3 or 12 months. Each injection schedule included four different injection levels resulting in average absorbed alpha-particle doses to bone of 0.1, 0.3, 1 and 3 Gy, respectively. The primary early effect observed was a hematological dyscrasia in the dogs receiving either of the two highest injection levels. The effect was most severe in the dogs receiving a single injection of 224Ra and resulted in the death of three dogs injected at the highest level. The late-occurring biological effects were tumors. Bone tumors were the most common followed by tumors in the nasal mucosa. The occurrence of bone tumors was highest in the dogs given the highest dose in 50 injections. The age-specific incidence rate for mammary tumors was increased in all three injection groups. The results of this study revealed two important exposure-rate effects. Hematological dyscrasia was amplified by delivery of relatively high doses at a high exposure rate. In contrast, bone tumors were amplified by delivery of relatively high doses at a lower exposure rate (i.e. dose delivered over 1 year rather than 1-3 months). There was a dose-response relationship for the induction of nasal mucosal tumors and mammary tumors. These findings in dogs are similar to those in humans injected with 224Ra, except for the nasal tumors. The calculated risk of developing a bone tumor was about 40 times higher in dogs than reported for humans.

Effect of chronic exposure to ultraviolet radiation and photoreactivation on life span and tumor development in the marsupial Monodelphis domestica.

The effect of exposure to chronic ultraviolet (UV) radiation on life span was examined in Monodelphis domestica, which is capable of photoreactivation repair of UV-radiation-induced pyrimidine dimers. Shaved Monodelphis were exposed to 500 J/m2 UV radiation, 500 J/m2 UV radiation then 90 min of photoreactivating light (PRL), or 90 min of PRL three times weekly for 104 weeks. Opossums were weighed weekly; samples for serum chemistry and hematology testing were obtained periodically. Complete postmortem examinations revealed a primary cause of death for each opossum. Meaningful differences among the groups in weight gain, serum chemistry values or hematology values were not seen. Significant life-shortening due to UV-radiation exposure was found for females but not males. Photoreactivation prolonged life only in the females exposed to UV radiation. Exposure to UV radiation was not associated with accelerated development of degenerative disease. Significant treatment-related mortality occurred in both male and female opossums exposed to UV radiation. Photoreactivation reduced the relative risk of skin tumors but not eye tumors in Monodelphis exposed to UV radiation. Eye and skin tumors were less likely to be a cause of death in UV-radiation-exposed opossums subsequently exposed to PRL than in opossums exposed to UV radiation alone. Females exposed only to UV radiation had an increased risk of skin tumor development relative to males.

Effects of protraction of the alpha dose to the lungs of mice by repeated inhalation exposure to aerosols of 239PuO2.

To determine the long-term biological effects of protracted alpha irradiation of the lung, 84-day-old C57BL/6J mice were repeatedly exposed by inhalation to aerosols of 239PuO2 every other month for up to six exposures in 10 months to reestablish lung burdens of 20, 90, or 460 Bq. Other mice were exposed only once when either 84 or 460 days of age to achieve desired initial lung burdens of 20, 90, 460, or 2300 Bq. Suitable control groups were maintained. Groups of mice with similar cumulative alpha doses to the lung had 3.4 to 4.4 times greater incidence of pulmonary tumors (adenomas and adenocarcinomas) when the dose to the lung was protracted by the repeated inhalation exposures compared to mice that received a single inhalation exposure. Excess pulmonary tumors per unit dose to the lung were also greater in groups of repeatedly exposed mice compared to those exposed only once. Repeatedly exposed mice also died earlier with pulmonary tumors than did those exposed once. It appears that protraction of an alpha dose to lungs increases the carcinogenic risk of inhaled 239PuO2 in mice.