Physics

For the generation of static magnetic fields solenoids are frequently used for the purpose of research and development of magnetic field sensors. When such a sensor is to be analyzed with regard to its inherent noise the influence of other noise sources of the measurement system needs to be minimized. This article reports on the low-frequency magnetic noise within such a coil system. On the one hand, the impact of the intrinsic noise of the coil itself and on the other hand the impact of additional current noise of various commercially available current sources, which accordingly also leads to magnetic noise within the coil, are investigated. With low-frequency values in the range of a few tens of fT/ Hz − − − √ , the coil's inherent noise is mostly neglectable. However, frequently utilized current sources for the generation of a static magnetic bias field lead to significant low-frequency magnetic flux noise typically in the nT/ Hz − − − √ regime. It is found that this noise cannot be decreased by increasing the coil's magnetic sensitivity, i.e. the magnetic flux density as a function of the static current. Instead, current sources with very high current-to-current-noise ratios are required.

COMPASS is a fixed target experiment at CERN SPS aimed to study hadron structure and spectroscopy. Hadron identification in the momentum range between 3 and 55GeV/c is provided by a large gaseous Ring Imaging Cherenkov Counter, RICH-1. To cope with the challenges imposed by the new physics program of COMPASS, RICH-1 has been upgraded by replacing four MWPC-based photon detectors with newly developed MPGD-based photon detectors. The architecture of the novel detectors is a hybrid combination of two layers of THGEMs and a Micromegas. The top of the first THGEM is coated with CsI acting as a reflective photo-cathode. The anode is segmented in pads capacitively coupled to the APV-25 based readout. The new hybrid detectors have been commissioned during the 2016 COMPASS data taking and stably operated during the 2017 run. In this paper design, construction, operation and performance aspects of the novel photon detectors for COMPASS RICH-1 are discussed.

Imaging Cherenkov detectors are largely used in modern nuclear and particle physics experiments where cutting-edge solutions are needed to face always more growing computing demands. This is a fertile ground for AI-based approaches and at present we are witnessing the onset of new highly efficient and fast applications. This paper focuses on novel directions with applications to Cherenkov detectors. In particular, recent advances on detector design and calibration, as well as particle identification are presented.

26,000 3-inch photomultiplier tubes (PMTs) have been produced for Jiangmen Underground Neutrino Observatory (JUNO) by the Hainan Zhanchuang Photonics Technology Co., Ltd (HZC) company in China and passed all acceptance tests with only 15 tubes rejected. The mass production began in 2018 and elapsed for about 2 years at a rate of ??1,000~PMTs per month. The characterization of the PMTs was performed in the factory concurrently with production as a joint effort between HZC and JUNO. Fifteen performance parameters were tracked at different sampling rates, and novel working strategies were implemented to improve quality assurance. This constitutes the largest sample of 3-inch PMTs ever produced and studied in detail to date.

The mass concentrations of Th-232 and U-238 in several strong, unfilled, high performance polymers are reported as measures of their radiopurity. Highly radiopure polymers are required as dielectric materials in the construction of rare event physics detectors, in order to minimize background signals arising from the detector materials themselves. New data are reported for carefully sourced samples of polyetheretherketone (PEEK), polyetherketoneketone (PEKK), a polyamide imide (PAI, branded as Torlon) and polybenzimidazole (PBI). Data for solid polyetherimide (PEI) are also discussed and new data for PEI in the form of a commercial 3D printing filament stock are reported. Strong high performance polymers PEKK, PBI, PAI and PEI were found with levels for Th-232 and U-238 that are below one milliBq/kg, including the PEI 3D printing filament. Specifically, for Th-232 and U-238 respectively, in microBq/kg, we found values of 149 and 184 for Arkema Kepstan PEKK 6002 flake; 69 and 2250 for Solvay Ketaspire PEEK flake; 346 and 291 for PBI Performance Products low metals grade 100 mesh PBI powder; 66 and 105 for Drake Plastics PAI Torlon T-4200 pellets; 401 and 285 for Drake Plastics cured PAI rod; 32 and 41 for Ensinger PEI Ultem 1000 solid; and 15 and 85 microBq/kg, for ThermaX PEI Ultem 1010 filament material. These results were all obtained using a novel dry ashing method in crucibles constructed of ultra low background (ULB) electroformed copper. Samples were spiked with T-229h and U-233 as internal standards prior to ashing and determinations were made by inductively coupled plasma mass spectrometry (ICP-MS). Radiopurity is displayed graphically relative to numerical measures of mechanical strength for these and several other polymers.

All systems are expected to be designed to fulfil their functions over their requested lifetime. Nevertheless, failure of a system may occur, and this is unfortunately, true also for vacuum systems. From a mechanical point of view, buckling, leak by fatigue crack propagation, rupture of a fixed support under unbalanced vacuum force... may happen. To well understand and anticipate the behaviour of a structure, it is mandatory to first understand the mechanical behaviour of materials as well as their failure modes. This is presented in a first part of the document. Then, the structural behaviour of a vacuum system and its relationship with the material properties is discussed. Finally, guidelines for the material selection for a given application are roughed out.

This paper presents studies of the performance of water-based liquid scintillator in both 1-kt and 50-kt detectors. Performance is evaluated in comparison to both pure water Cherenkov detectors and a nominal model for pure scintillator detectors. Performance metrics include energy, vertex, and angular resolution, along with a metric for ability to separate the Cherenkov from the scintillation signal, as being representative of various particle identification capabilities that depend on the Cherenkov / scintillation ratio. We also modify the time profile of scintillation light to study the same performance metrics as a function of rise and decay time. We go on to interpret these results in terms of their impact on certain physics goals, such as solar neutrinos and the search for Majorana neutrinos. This work supports and validates previous results, and the assumptions made therein, by using a more complete detector model and full reconstruction. We confirm that a high-coverage, 50-kt detector would be capable of better than 10 (1)\% precision on the CNO neutrino flux with a WbLS (pure LS) target in 5 years of data taking. A 1-kt LS detector, with a conservative 50\% fiducial volume of 500~t, can achieve a better than 5\% detection. Using the liquid scintillator model, we find a sensitivity into the normal hierarchy region for Majorana neutrinos, with half life sensitivity of T 0νββ 1/2 >1.4× 10 28 years at 90\% CL for 10 years of data taking with a Te-loaded target.

In this paper we present the outcome of the first international comparison in the terahertz frequency range among three different kinds of spectrometers. A Fourier-Transform infrared spectrometer, a Vector Network Analyzer and a Time-Domain Spectrometer have been employed for measuring the complex refractive index of three travelling standards made of selected dielectric materials in order to offer a wide enough range of parameters to be measured. The three spectrometers have been compared in terms of measurement capability and uncertainty.

A neutron lifetime measurement conducted at the Japan Proton Accelerator Research Complex (J-PARC) is counting the number of electrons from neutron decays with a time projection chamber (TPC). The γ rays produced in the TPC cause irreducible background events. To achieve the precise measurement, the inner walls of the TPC consist of 6 Li-enriched lithium-fluoride ( 6 LiF) tiles to suppress the amount of γ rays. In order to estimate the amount of γ rays from the 6 LiF tile, prompt gamma ray analysis (PGA) measurements were performed using germanium detectors. We reconstructed the measured γ -ray energy spectrum using a Monte Carlo simulation with the stripping method. Comparing the measured spectrum with a simulated one, the number of γ rays emitted from the 6 LiF tile was ( 2.3 +0.7 −0.3 )× 10 −4 per incident neutron. This is 1.4 +0.5 −0.2 times the value assumed for a mole fraction of the 6 LiF tile. We concluded that the amount of γ rays produced from the 6 LiF tile is not more twice the originally assumed value.

225Ac is a valuable medical radionuclide for targeted alpha therapy, but 227Ac is an undesirable byproduct of an accelerator-based synthesis method under investigation. Sufficient detector sensitivity is critical for quantifying the trace impurity of 227Ac, with the 227Ac/225Ac activity ratio predicted to be approximately 0.15% by end-of-bombardment (EOB). Superconducting transition edge sensor (TES) microcalorimeters offer high resolution energy spectroscopy using the normal-to-superconducting phase transition to measure small change in temperature. By embedding 225Ac production samples in a gold foil thermally coupled to a TES microcalorimeter we can measure the decay energies of the radionuclides embedded with high resolution and efficiency. This technique, known as decay energy spectroscopy (DES), collapses several peaks from alpha decays into single Q-value peaks. In practice there are more complex factors in the interpretation of data using DES, which we will discuss herein. Using this technique we measured the EOB 227Ac impurity to be (0.142 +/- 0.005)% for a single production sample. This demonstration has shown that DES can distinguish closely related isotopic features and is a useful tool for quantitative measures.