A neutron trigger detector for pulsed neutron sources

A variety of experiments investigating properties of neutrons can be performed at pulsed source facilities like the research reactor TRIGA Mainz. A typical problem faced by these experiments is the non-availibility of a reliable facility-provided trigger signal in coincidence with the neutron production. Here we present the design and implementation of a neutron pulse detector that provides a coincident trigger signal for experimental timing with a relative precision of 4.5 ms.Comment: 16 pages, 10 figure

Assessment of efficacy and safety of endoscopic lung volume reduction with one-way valves in patients with a very low FEV1

Introduction Endoscopic lung volume reduction (ELVR) with one-way valves produces beneficial outcomes in patients with severe emphysema. Evidence on the efficacy remains unclear in patients with a very low forced expiratory volume in 1 s (FEV1) (≤20% predicted). We aim to compare clinical outcomes of ELVR, in relation to the FEV1 restriction. Methods All data originated from the German Lung Emphysema Registry (Lungenemphysem Register), which is a prospective multicentric observational study for patients with severe emphysema after lung volume reduction. Two groups were formed at baseline: FEV1 ≤20% pred and FEV1 21–45% pred. Pulmonary function tests (FEV1, residual volume, partial pressure of carbon dioxide), training capacity (6-min walk distance (6MWD)), quality of life (modified Medical Research Council dyspnoea scale (mMRC), COPD Assessment Test (CAT), St George's Respiratory Questionnaire (SGRQ)) and adverse events were assessed and compared at baseline and after 3 and 6 months. Results 33 patients with FEV1 ≤20% pred and 265 patients with FEV1 21–45% pred were analysed. After ELVR, an increase in FEV1 was observed in both groups (both p<0.001). The mMRC and CAT scores, and 6MWD improved in both groups (all p<0.05). The SGRQ score improved significantly in the FEV1 21–45% pred group, and by trend in the FEV1 ≤20% pred group. Pneumothorax was the most frequent complication within the first 90 days in both groups (FEV1 ≤20% pred: 7.7% versus FEV1 21–45% pred: 22.1%; p=0.624). No deaths occurred in the FEV1 ≤20% pred group up to 6 months. Conclusion Our study highlights the potential efficacy of one-way valves, even in patients with very low FEV1, as these patients experienced significant improvements in FEV1, 6MWD and quality of life. No death was reported, suggesting a good safety profile, even in these high-risk patients

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.ISSN:0034-6748ISSN:1089-762

Search for an interaction mediated by axion-like particles with ultracold neutrons at the PSI

We report on a search for a new, short-range, spin-dependent interaction using a modified version of the experimental apparatus used to measure the permanent neutron electric dipole moment at the Paul Scherrer Institute. This interaction, which could be mediated by axion-like particles, concerned the unpolarized nucleons (protons and neutrons) near the material surfaces of the apparatus and polarized ultracold neutrons stored in vacuum. The dominant systematic uncertainty resulting from magnetic-field gradients was controlled to an unprecedented level of approximately 4 pT cm⁻¹ using an array of optically-pumped cesium vapor magnetometers and magnetic-field maps independently recorded using a dedicated measurement device. No signature of a theoretically predicted new interaction was found, and we set a new limit on the product of the scalar and the pseudoscalar couplings gₛgₚλ² < 8.3 × 10⁻²⁸ m² (95% C.L.) in a range of 5 µm < λ < 25 mm for the monopole–dipole interaction. This new result confirms and improves our previous limit by a factor of 2.7 and provides the current tightest limit obtained with free neutrons.ISSN:1367-263

Mapping of the magnetic field to correct systematic effects in a neutron electric dipole moment experiment

Experiments dedicated to the measurement of the electric dipole moment of the neutron require outstanding control of the magnetic-field uniformity. The neutron electric dipole moment (nEDM) experiment at the Paul Scherrer Institute uses a Hg199 co-magnetometer to precisely monitor temporal magnetic-field variations. This co-magnetometer, in the presence of field nonuniformity, is, however, responsible for the largest systematic effect of this measurement. To evaluate and correct that effect, offline measurements of the field nonuniformity were performed during mapping campaigns in 2013, 2014, and 2017. We present the results of these campaigns, and the improvement the correction of this effect brings to the neutron electric dipole moment measurement.ISSN:1094-1622ISSN:0556-2791ISSN:1050-294