Physics

We have developed a low-energy electron recoil (ER) calibration method with 220 Rn for the PandaX-II detector. 220 Rn, emanated from natural thorium compounds, was fed into the detector through the xenon purification system. From 2017 to 2019, we performed three dedicated calibration campaigns with different radon sources. We studied the detector response to α , β , and γ particles with focus on low energy ER events. During the runs in 2017 and 2018, the amount of radioactivity of 222 Rn were on the order of 1\% of that of 220 Rn and thorium particulate contamination was negligible, especially in 2018. We also measured the background contribution from 214 Pb for the first time in PandaX-II with the help from a 222 Rn injection. Calibration strategy with 220 Rn and 222 Rn will be implemented in the upcoming PandaX-4T experiment and can be useful for other xenon-based detectors as well.

We present analytical calculations, Finite Element Analysis modeling, and physical measurements of the interstrip capacitances for different potential strip geometries and dimensions of the readout boards for the GE2/1 triple-Gas Electron Multiplier detector in the CMS muon system upgrade. The main goal of the study is to find configurations that minimize the interstrip capacitances and consequently maximize the signal-to-noise ratio for the detector. We find agreement at the 1.5--4.8% level between the two methods of calculations and on the average at the 17% level between calculations and measurements. A configuration with halved strip lengths and doubled strip widths results in a measured 27--29% reduction over the original configuration while leaving the total number of strips unchanged. We have now adopted this design modification for all eight module types of the GE2/1 detector and will produce the final detector with this new strip design.

The LaBr 3 (Ce) detector has attracted much attention in recent years for its superior characteristics to other scintillating materials in terms of resolution and efficiency. However, it has relatively high intrinsic radiation background due to the naturally occurring radioisotope in lanthanum, actinium and their daughter nuclei. This limits its applications in low counting rate experiments. In this paper, we identified the radioactive isotopes in the ϕ 3 ′′ × 3 ′′ Saint-Gobain B380 detector by a coincidence measurement using a Clover detector in a low-background shielding system. Moreover, we carried out a Geant4 simulation to the experimental spectra to evaluate the activities of the main internal radiation components. % by means of the α , γ and β decays from the 138 La and 227 Ac. The activity of radiation background of B380 is determined to be 1.480 (69) Bq/cm 3 , the main sources of which include 138 La of 1.425 (59) Bq/cm 3 , 211 Bi of 0.0136 (15) Bq/cm 3 , 219 Rn of 0.0125 (17) Bq/cm 3 , 223 Ra of 0.0127 (14) Bq/cm 3 , and 227 Th of 0.0158 (22) Bq/cm 3 .

The LHC is undergoing a high luminosity upgrade, which is set to increase the instantaneous luminosity by at least a factor of five, resulting in a higher muon flux rate in the forward region, which will overwhelm the current trigger system of the CMS experiment. The ME0, a gas electron multiplier detector, is proposed for the Phase-2 Muon System Upgrade to help increase the muon acceptance and to control the Level 1 muon trigger rate. To lower the probability of HV discharges, the ME0 was designed with GEM foils that are segmented on both sides. Initial testing of the ME0 showed substantial crosstalk between readout sectors. Here, we investigate, characterize, and quantify the crosstalk in the detector, and estimate the performance of the chamber as a result of this crosstalk via simulation of the detector dead time, efficiency loss, and frontend electronics response. The results of crosstalk via signals produced by applying a square voltage pulse directly on the readout strips of the detector with a pulser are summarized, and the efficacy of various mitigation strategies are presented. The crosstalk is a result of capacitive coupling between the readout strips on the readout board and between the readout strips and the bottom of GEM3. The crosstalk also generally follows a pattern where the largest magnitude of crosstalk is within the same azimuthal readout segment in the detector and in the nearest horizontal segments. The use of bypass capacitors and larger HV segments successfully reduce the crosstalk: we observe a maximum decrease of crosstalk in sectors previously experiencing crosstalk from (1.66±0.03)% to (1.11±0.02)% with all HV segments connected in parallel on the bottom of GEM3, with an HV low-pass filter, and an HV divider. These mitigation strategies slightly increase crosstalk (�?.4%) in readout sectors farther away.

To study vertical sag requirements and factors affecting the stretched wire alignment method, the vertical sag equation is first derived theoretically. Subsequently, the influencing factors,such as the hanging weight or tension, span length, temperature change, elastic deformation, and the Earths rotation, of the vertical sag are summarized, and their validity is verified through actual measurements. Finally, the essential factors affecting vertical sag, the specific strength and length, are discussed. It is believed that the vertical sag of a stretched wire is proportional to the square of the length and inversely proportional to the specific strength of the material.

The surface resistance reduction can further suppress the surface power loss of a superconducting radio-frequency cavity. Since the surface resistance of a superconducting radio-frequency cavity is mainly originated from the magnetic flux trapping, and thus the corresponding magnetic field strength could be measured to reflect the residual resistance. A fluxgate magnetometer is always employed to measure the ambient surface magnetic field of a superconducting radio-frequency cavity. However, this kind of equipment is relatively larger than the cavity and always need expensive cost. In this paper, we developed a magneto-inductive (MI) magnetic sensor, which is smaller, lighter weight, and lower cost than the fluxgate magnetometer. The specifications such as the noise floor, resolution, etc., are measured. In addition, a comparative observation of the magnetic field between the proposed MI sensor and a highly precise is conducted. The experimental results identify the capability of the proposed MI sensor in weak magnetic detection.

It is essential to investigate various types of noise in gravitational-wave telescopes such as KAGRA. A crackling noise is an intermittent noise, which can occur when a material experiences stress. KAGRA could be prevented from reaching the target sensitivity if the crackling noise appears in the geometric anti-spring filter (GAS) of the vibration isolation system. Therefore it is necessary to investigate the effect of crackling noise in the GAS. For this research, a crackling noise measurement system with a miniature GAS was built, and the noise was measured when stress was intentionally added to the GAS. The scaling law of crackling noise was also investigated using a GAS of a different design. Then the upper limit of the crackling noise in KAGRA was estimated, from the results of the experiment and the derived scaling law, to be less than the target sensitivity of KAGRA at frequencies above 55 Hz.

The precise measurement of the pressure of the gas enclosed in the starting volume of a static expansion system is important for achieving low measurement uncertainties. This work focuses on the valve closing process and the resulting pressure difference. The flow conservation law is used to set up a model and an experimental procedure has been developed to investigate the pressure drop across the moving valve plate. Various parameters are evaluated and compared with experimental data.

In this paper, we present the design and test results of LOCx2, a transmitter ASIC for the ATLAS Liquid Argon Calorimeter trigger upgrade. LOCx2 consists of two channels and each channel encodes ADC data with an overhead of 14.3% and transmits serial data at 5.12 Gbps with a latency of less than 27.2 ns. LOCx2 is fabricated with a commercial 0.25-um Silicon-on-Sapphire CMOS technology and is packaged in a 100-pin QFN package. The power consumption of LOCx2 is about 843 mW.

In this paper, we present the design and test results of LOCx2-130, a low-power, low-latency, dual-channel transmitter ASIC for detector front-end readout. LOCx2-130 has two channels of encoders and serializers, and each channel operates at 4.8 Gbps. LOCx2-130 can interface with three types of ADCs, an ASIC ADC and two COTS ADCs. LOCx2-130 is fabricated in a commercial 130-nm CMOS technology and is packaged in a 100-pin QFN package. LOCx2-130 consumes 440 mW and achieves a latency of less than 40.7 ns.