Effect of multiple coulomb scattering on the beam tests of silicon pixel detectors

In the research and development of new silicon pixel detectors,a collimated monoenergetic charged-particle test beam equipped with a high-resolution pixel-beam telescope is crucial for prototype verification and performance evaluation.When the beam energy is low,the effect of multiple Coulomb scattering on the measured resolution of the Device Under Test(DUT)must be considered to accurately evaluate the performance of the pixel chips and detectors.This study aimed to investigate the effect of multiple Coulomb scattering on the measured resolution,particularly at low beam energies.Simulations were conducted using Allpix^(2) to study the effects of multiple Coulomb scattering under different beam energies,material budgets,and telescope layouts.The simulations also provided the minimum energy at which the effect of multiple Coulomb scattering could be ignored.Compared with the results of a five-layer detector system tested with an electron beam at DESY,the simulation results were consistent with the beam test results,confirming the reliability of the simulations.

Aging behavior of large area MCP–PMT

The Institute of High Energy Physics, Chinese Academy of Sciences have designed a new type of photomultiplier tube(PMT) based on microchannel plates(MCPs) with large area photocathode, known as large area microchannel plate photomultiplier tube(MCP–PMT). The aging characteristics of the large area MCP–PMTs are different from dynode PMTs and small proximity-focus MCP–PMT. In this work, a prototype large area MCP–PMT was aged by operating with nearly 1000 photoelectrons per pulse for 3 months, and aging process of the MCP–PMT was discussed based on the aging curve.

Attenuation length measurements of a liquid scintillator with LabVIEW and reliability evaluation of the device

An attenuation length measurement device was constructed using an oscilloscope and LabVIEW for signal acquisition and processing. The performance of the device has been tested in a variety of ways. The test results show that the set-up has a good stability and high precision （sigma/mean reached 0.4 percent）. Besides, the accuracy of the measurement system will decrease by about 17 percent if a filter is used. The attenuation length of a gadolinium-loaded liquid scintillator （Gd-LS） was measured as 15.1±0.35 m where Gd-LS was heavily used in the Daya Bay Neutrino Experiment. In addition, one method based on the Beer-Lambert law was proposed to investigate the reliability of the measurement device, the R-square reached 0.9995. Moreover, three purification methods for Linear Alkyl Benzene （LAB） production were compared in the experiment.

Physics potential of searching for 0νββ decays in JUNO

In the past few decades,numerous searches have been made for the neutrinoless double-beta decay（0νββ） process,aiming to establish whether neutrinos are their own antiparticles（Majorana neutrinos）,but no 0νββdecay signal has yet been observed.A number of new experiments are proposed but they ultimately suffer from a common problem： the sensitivity may not increase indefinitely with the target mass.We have performed a detailed analysis of the physics potential by using the Jiangmen Underground Neutrino Observatory（JUNO） to improve the sensitivity to 0νββ up to a few me V,a major step forward with respect to the experiments currently being planned.JUNO is a 20 kton low-background liquid scintillator（LS） detector with 3%/（E（MeV））1/2 energy resolution,now under construction.It is feasible to build a balloon filled with enriched xenon gas（with136Xe up to 80%） dissolved in LS,inserted into the central region of the JUNO LS.The energy resolution is 1.9% at the Q-value of 136Xe 0νββ decay.Ultra-low background is the key for 0νββ decay searches.Detailed studies of background rates from intrinsic 2νββ and 8B solar neutrinos,natural radioactivity,and cosmogenic radionuclides（including light isotopes and 137Xe） were performed and several muon veto schemes were developed.We find that JUNO has the potential to reach a sensitivity（at 90% C.L.） to T1/20νββof 1.8×1028yr（5.6×1027yr） with 50 tons（5 tons） of fiducial136 Xe and 5 years exposure,while in the 50-ton case the corresponding sensitivity to the effective neutrino mass,mββ,could reach（5–12） meV,covering completely the allowed region of inverted neutrino mass ordering.

Laboratory measurement of radioactivity purification for ^(212)Pb in liquid scintillator

Liquid scintillator（LS） has been widely used in past and running neutrino experiments, and is expected also to be used in future experiments. Requirements on LS radio-purity have become higher and higher. Water extraction is a powerful method to remove soluble radioactive nuclei, and a mini-extraction station has been constructed. To evaluate the extraction efficiency and optimize the operation parameters, a setup to load radioactivity to LS and a laboratory scale setup to measure radioactivity using the ^212Bi-^212Po-^208Pb cascade decay have been developed. Experience from this laboratory study will be useful for the design of large scale water extraction plants and the optimization of working conditions in the future.

Performance evaluation of an SOI pixel sensor with in-pixel binary counters

Introduction Pixel detectors fabricated with the silicon-on-insulator(SOI)technology suffered from the digital pickup,due to the capacitive coupling between the sensing electrode and the in-pixel circuit.In order to tackle this issue,an advanced process called double SOI has been developed.A prototype chip CPIXTEG3b adopting this new process was designed and characterized.While optimization concerning the double-SOI design and testing of the single pixel were already presented in a separate publication,this paper focuses on its noise performance of the full matrix and X-ray detection utilizing a synchrotron photon beam.Methods Equivalent noise charge(ENC)of the full pixel matrix was measured with electrical pulse tests.The threshold dispersion was minimized by the DAC tuning in each individual pixel.As a photon-counting X-ray imager,noise count accumulated up to 1 h was measured.Detection efficiency was measured with a micro-focused beam as well as a flat field generated by the X-ray scattering on a glassy carbon at the KEK PF beam line 14A.Results The typical ENC is 52 e−and the sigma of threshold dispersion is 10 e−over the full matrix.A merit of“zero”noise count is also demonstrated,which is consistent with the low ENC.The prototype chip has been tested with microbeam and used to measure the beam profile to be with a full width of 50µm at 2.4%of the maximum height.Both sensor depletion and charge sharing between neighboring pixels have been carefully characterized,providing insights for further development.The homogeneity of response to X-ray photons has been demonstrated in the flat field test.This work has drawn a final conclusion to the solution of digital pickup issue and opened a promising prospect in low-noise and high-resolution X-ray imaging.