Large area^(3)He tube array detector with modular design for multi‑physics instrument at CSNS

The multi-physics instrument(MPI)is the first user cooperative instrument at the China Spallation Neutron Source(CSNS).It was designed to explore the structures of complex materials at multiple scales based on the neutron total scattering technique.This imposes the requirements for the detector,including a high detection efficiency to reduce the measurement time and a large solid angle coverage to cover a wide range of momentum transfers.To satisfy these demands,a large-area array of 3He-filled linear position-sensitive detectors(LPSDs)was constructed,each with a diameter of 1 inch and pressure of 20 atm.It uses an orbicular layout of the detector and an eight-pack module design for the arrangement of 3He LPSDs,covering a range of scattering angles from 3°to 170°with a total detector area of approximately 7 m2.The detector works in air,which is separated from the vacuum environment to facilitate installation and maintenance.The characteristics of the MPI detector were investigated through Monte Carlo(MC)simulations using Geant4 and experimental measurements.The results suggest that the detectors are highly efficient in the wavelength range of the MPI,and an efficiency over 25%is achievable for above 0.1 A neutrons.A minimal position resolution of 6.4 mm full width at half maximum(FWHM)along the tube length was achieved at a working voltage of 2200 V,and a deviation below 2 mm between the real and measured positions was attained in the beam experiment.The detector module exhibited good consistency and an excellent counting rate capacity of up to 80 kHz,which satisfied the requirements of experiments with a high event rate.Observations of its operation over the past year have shown that the detector works steadily in sample experiments,which allows the MPI to serve the user program successfully.

Optimization of the cavity beam-position monitor system for the Shanghai soft X-ray free-electron laser user facility

To achieve high-efficiency operation of the highgain free-electron laser(FEL),the electron beams and radiated photon beams need to be overlapped precisely and pass through the entire undulator section.Therefore,a high-resolution beam-position monitor(BPM)is required.A cavity BPM(CBPM)with a resonant cavity structure was developed and used in the Shanghai Soft X-ray FEL(SXFEL)test facility and can achieve a position resolution of<1μm.The construction and operation of the SXFEL user facility also bring about higher requirements for beamposition measurement.In this case,the factors that affect the performance of the CBPM system were further analyzed.These included the amplitude and phase stability of the local oscillator,stability of the trigger signal,performance of the radio frequency front-end,signal processing electronics,and signal processing algorithms.Based on the upgrade and optimization of the system,a beam test platform was built at the end of the linear acceleration section of the SXFEL,and the experimental results show that the position resolution of the system can reach 177 nm at a bunch charge of 500 pC,and the dynamic range is controlled within±300μm,and the relative measurement uncertainty of the bunch charge can reach 0.021%,which are significant improvements compared to the attributes of the previous system.

Performance Calibration Using Cosmic Rays for the Multi-Neutron Correlation Spectrometer

Efficient calibration methods have been applied to a complex neutron detector array by using the cosmic-ray muons. Through a differential operation on the time difference spectrum, the two edges of this spectrum can be precisely determined, corresponding to the geometrical two ends of the bar, and therefore the relationship between the position and time difference spectrum can be deduced for each bar. The alignment between different bars is realized by choosing cosmic- rays which are perpendicular to the bars. The position resolutions are extracted through a track fitting procedure which uses all tracks detected coincidently by the whole system, together with a simulation analysis. A method is also developed to calibrate the deposited energy by using cosmic-rays at different incident angles.

A high-position-resolution trajectory detector system for cosmic ray muon tomography:Monte Carlo simulation

Purpose The research focuses on the related designing and simulating the high-position-resolution trajectory detector system based on cosmic ray muon tomography.Methods The energy deposition of muon in the detector varies with the length of the ionization path.Results The simulation of the submillimeter detector system was designed for muon imaging.The optimal position resolution of the detector reached 0.6 mm.Conclusions The entire research process includes the selection of analysis of parameters affecting system design,designing of two high-position-resolution detectors based on plastic scintillators,implementation of different imaging algorithms and image quality assessment based on different imaging models.It provides a solution based on high positional resolution plastic scintillator detectors for cosmic ray muon scattering imaging.

Measurement of avalanche size and position resolution of RPCs with different surface resistivities of the high voltage provider

The effects of surface resistivity of the high voltage provider on the space dispersion of the induced charge of a prototype Resistive Plate Chamber （RPC） have been studied experimentally and theoretically. The results of both experiment and theory agree and confirm that a two-Gaussian function can be used to fit the dispersion of the induced charge of the RPC. It is shown that the Gaussian function with the narrower width is mainly due to the expansion of the avalanche charge in the gas gap of the RPC, and the Gaussian function with the larger width is due to the charge dispersion when it passes through the resistive carbon film. This will be useful in the RPC design when one wants to make an RPC with high position resolution.

A position resolution MRPC for muon tomography

Muon tomography is a promising method in the detection and imaging of high Z material. In general, considering the quality of track reconstruction in imaging, a detector of good position resolution, high efficiency and large area is required. This paper presents the design and study of a prototype of position sensitive MRPC with 0.15 mm narrow gas gap and 2.54 mm strip readout. Through a cosmic-ray experiment, the performance of MRPC module is carefully observed and each channel is calibrated. Through an X ray experiment with a narrow slit, the position resolution is studied. The results show that the time resolution of the module can reach 61ps and the spatial resolution can reach 0.36 mm.

Development of a MWDC prototype of the CSR external-target experiment

The cooling storage ring(CSR)external-target experiment(CEE)is a spectrometer used in construction to study the properties of nuclear matter in high-baryon density regions at the Heavy-Ion Research Facility in Lanzhou(HIRFL).This study presents the design,simulation,manufacturing,and testing of a half-size prototype of a multi-wire drift chamber(MWDC)for the CEE.First,the performance of the MWDC connected to homemade electronics was simulated.The results demonstrated that an energy resolution of 18.5% for 5.9-keV X-rays and a position resolution of 194μm for protons can be achieved by the current design.Because the size of the largest MWDC reached 176 cm×314 cm,a set of 98 cm×98 cm prototypes was built using the new techniques.The positioning accuracy of the anode wires in this prototype is better than 20μm.After optimization,using commercially available electronics,the prototype can achieved an energy resolution of 19.7%for a^(55)Fe X-ray source.The CEE-MWDC detector and electronics were simultaneously tested.An energy resolution of 22%was achieved for the^(55)Fe source;the track residuals were approximately 330μm for the cosmic rays.The results demonstrate that the current design and techniques meet the requirements of the CEE-MWDC array.

Effect of the integrated time of the induced current signal on the position resolution of the RPC detector

A prototype RPC with position resolution less than 1 mm has been produced and studied. Based on this RPC detector, the effect of the width of the integrated FADC time window on the position resolution of a RPC has been studied experimentally and theoretically. The results of theoretical calculation and experimental measurement have shown good agreement.

Development and study of an imaging detector based on high-position resolution THGEM

Introduction THickGaseous Electron Multiplier(THGEM)has many advantages while the moderate position resolution is regarded as the main inferiority comparing with the traditional GEM,so this limits the applications of THGEM,such as X-ray imaging and charge particle tracking.Materials and methods By improving the production techniques,THGEMs with smaller pitch and hole diameter can be made,i.e.,0.4 and 0.15 mm by mechanical drilling,and 0.3 and 0.1 mm by laser etching,respectively.Based on the new THGEMs,a two-dimensional imaging detector with 50×50mm sensitive area was developed for 0.1∼50 MeVlow-energy electrons detection and reaching better than 100μm position resolution(sigma).At the same time,a set of front-end electronics was developed based on homemade ASIC chips,i.e.,Charge Amplifier and Shaping Amplifier for GEM(CASAGEM),and applied successfully to the detector.Conclusion The X-ray and beam tests results indicate that both detector and Front End Electronics(FEE)worked well,and the position resolution achieved 74.9μm by using the charge center-of-gravity method.This indicates that the high-position resolution THGEM is promising for imaging and tracking application.

Development of 3He-filled linear position-sensitive detector for neutron scattering instruments at CSNS

Background Helium-3-filled linear position-sensitive detectors(LPSDs)have been widely applied to neutron scattering instruments in recent decades owing to the high detection efficiency,the excellent neutron/gamma discrimination,and the ability to construct the detector with large area coverage.More than 65%of neutron instruments at the China Spallation Neutron Source(CSNS)require ^(3)He LPSDs for the building of the detector system.The detector of a neutron scattering instrument is normally an array detector composed of a large number of ^(3)He LPSDs.However,no appropriate substitute detector is available for the ^(3)He LPSD for operation over a short period,and its specifications need to be customized to satisfy the requirements of different instruments.This necessitates the development of ^(3)He LPSDs with different specifications for building and upgrading the detectors of neutron scattering instruments at CSNS.Purpose To meet the general requirements specified by the neutron instruments at CSNS,a ^(3)He LPSD was developed and its performances were investigated by using the neutron beam.Methods The neutron beam experiments for this ^(3)He LPSD,including measurements of counting rate plateau curve,position calibration,and position resolution along the tube path,were carried out at the beamline-20 of CSNS.To evaluate its performance in the instrument operation,a detector module made of this ^(3)He LPSD has been installed in the multi-physics instrument(MPI),and the comparison test with the commercial ^(3)He LPSD has been conducted at neutron scattering experiments.Results and conclusion The experimental measurements for this ^(3)He LPSD based on the neutron beam showed that it satisfies the requirements for use in neutron scattering instruments.It reaches a plateau slope of 2.6%/100 V with a plateau range from 1750 to 1950 V and attained a minimal position resolution of 5.3 mm(FWHM),superior to the one achieved by the commercial ^(3)He LPSD.In addition,this ^(3)He LPSD detector module applied to the MPI has been working steadily for half of year and is available for use in experiments.These results provide a sound basis for the subsequent construction and upgradation of the detector of neutron scattering instruments at CSNS.

Study on the imaging ability of the 2D neutron detector based on MWPC

A 2D neutron detector based on 3He convertor and MWPC with an active area of 200 mmx200 mm has been successfully designed and fabricated. The detector has been tested with Am/Be neutron source and with collimated neutron beam with the wavelength of λ=1.37A. The best spatial resolution of 1.18 mm （FWHM） and good linearity were obtained. This is in good agreement with theoretical calculations.

Observable-specific phase biases of Wuhan multi-GNSS experiment analysis center’s rapid satellite products

Precise Point Positioning(PPP)with Ambiguity Resolution(AR)is an important high-precision positioning technique that is gaining popularity in geodetic and geophysical applications.The implementation of PPP-AR requires precise products such as orbits,clocks,code,and phase biases.As one of the analysis centers of the International Global Navigation Satellite System(GNSS)Service(IGS),the Wuhan University Multi-GNSS experiment(WUM)Analysis Center(AC)has provided multi-GNSS Observable-Specific Bias(OSB)products with the associated orbit and clock products.In this article,we first introduce the models and generation strategies of WUM rapid phase clock/bias products and orbit-related products(with a latency of less than 16 h).Then,we assess the performance of these products by comparing them with those of other ACs and by testing the PPP-AR positioning precision,using data from Day of the Year(DOY)047 to DOY 078 in 2022.It is found that the peak-to-peak value of phase OSBs is within 2 ns,and their fluctuations are caused by the clock day boundary discontinuities.The associated Global Positioning System(GPS)orbits have the best consistency with European Space Agency(ESA)products,and those of other systems rank in the medium place.GLObal NAvigation Satellite System(GLONASS)clocks show slightly inconsistency with other ACs’due to the antenna thrust power adopted,while the phase clocks of other GNSSs show no distortion compared with legacy clocks.With well-estimated phase products for Precise Orbit Determination(POD),the intrinsic precision is improved by 14%,17%,and 24%for GPS,Galileo navigation satellite system(Galileo),and BeiDou-3 Navigation Satellite System(BDS-3),respectively.The root mean square of PPP-AR using our products in static mode with respect to IGS weekly solutions can reach 0.16 cm,0.16 cm,and 0.44 cm in the east,north,and up directions,respectively.The multi-GNSS wide-lane ambiguity fixing rates are all above 90%,while the narrow-lane fixing rates above 80%.In conclusion,the phase OSB products at WUM have good precision and performance,which will benefit multi-GNSS PPP-AR and POD.

A normal-pressure MWPC for beam diagnostics at RIBLL2

A normal pressure MWPC for beam diagnostics at RIBLL2 has been developed, wmcn has a sensluve area of 80 mm×80 mm and consists of three-layer wire planes. The anode plane is designed with a wider frame to reduce the discharge and without using protection wires. The detector has been tested with a 55Fe X-ray source and a 200 MeV/u ^12C beam from CSRm. A position resdution better than 250 μm along the anode wires and a detection efficiency higher than 90% have been achieved.

Study of a multi-wire proportional chamber with a cathode strip and delay-line readout

The design principle for a multi-wire proportional chamber with a cathode strip and delay-line readout is described. A prototype chamber of a size of 10 cm×10 cm was made together with the readout electronics circuit. A very clean signal with very low background noise was obtained by applying a transformer between the delay-line and the pre-amplifier in order to match the resistance. Along the anode wire direction a position resolution of less than 0.5 mm was achieved with a ^55Fe-5.9 keV X ray source. The simple structure, large effective area and high position resolution allow the application of a gas chamber of this kind to many purposes.

Delay line readout of a large dimension multi-wire proportional chamber

A two dimensional multi-wire proportional chamber with delay line readout was developed, which has a large sensitive area of 30 cmx30 cm. Two cathode planes using printed circuit boards are orthogonally placed to give two coordinates of the impact point of the particle. Signals collected from the cathode strips are amplified and discriminated from two ends of the delay line at each cathode board. By recording the time difference between the two discrimination pulses and the common gate pulse from anode wires, a coordinate position was reconstructed, and a position resolution of better than 1 mm could be obtained in the whole sensitive area along the anode wires.

Fast calibration methods using cosmic rays for a neutron detection array

An overall irradiation and calibration technique was introduced and applied to a test scintillation detector array. An integral conversion method was used to reduce the nonlinearity of the time difference spectrum, and to improve the position determination especially for positions close to the two ends of a long scintillation bar. An overall position resolution of about 3.0 cm （FWHM） was extracted from the residual analysis method and verified by a direct measurement. Energy calibration was also realized by selecting cosmic rays at different incident angles. The bulk light attenuation lengths for the four test bars were also determined. It is demonstrated that these methods are especially efficient for calibrating large and complex detector arrays

A large area plastic scintillation detector with 4-corner-readout

A 760 mm × 760 mm× 30 mm plastic scintillation detector viewed by photomultiplier tubes （PMTs） from four corners has been developed, and the detector has been tested with cosmic rays and γrays. A position- independent effective time Teff has been found, indicating this detector can be used as a TOF detector. The hit position can also be reconstructed by the time from the four corners.A. TOF resolution of 236 ps and a position resolution of 48 mm have been achieved, and the detection efficiency has also been investigated.

Test and simulation of a MICROMEGAS detector

We report on the recent test results of a MICROMEGAS detector in terms of position resolution, time resolution and efficiency. With a Ar＋CO2 （10%） gas mixture and a strip pitch of 200 μm an accuracy of 80 μm in sigma on the position has been measured. The time resolution is better than 20 ns and a cosmic ray detection efficiency of 94% was obtained. A Monte Carlo simulation indicates that transverse diffusion, gain fluctuation and electronic noise limit the position resolution.

Evaluation of a position-sensitive prototype detector unit for fast neutron imaging and spectroscopy

Purpose A novel fast neutron scatter camera with capabilities of neutron imaging and spectroscopy is under development.The detection principle is based on multiple neutron–proton(n–p)elastic scattering interactions in organic scintillator.In order to improve position measurement accuracy of recoil protons,a position-sensitive prototype detector unit has been designed and characterized experimentally.Methods The presented detector unit consisted of a plastic scintillator sheet of 10 cm×10 cm×1 cm dimensions and two groups(6×2)of wavelength-shifting fibers with orthogonal directions embedded into grooves on two opposite scintillator surfaces.Scintillation signals were read out by silicon photomultipliers(SiPMs).A collimated Sr-90 radioactive source was utilized for system calibration and position resolution measurement.Results Light output of the unidimensional six fiber channels from one side of the detector unit was calibrated to be 14.45 photoelectrons per MeVee.Position resolution of the detector unit was measured to be 0.35–0.44 times fiber pitch,corresponding to 5.48 mm for proton recoil energy interval of 1.63–2.60 MeV,and 4.60 mm for proton recoil energy interval of 4.82–5.50 MeV.Energy threshold for recoil proton localization was estimated to be 1.18 MeV.Conclusion The results shown satisfy basic requirements of the scatter camera,while space exists for further improvements.The positioning performance optimization consists of three aspects.The first one is to increase the fiber diameter so as to reduce signal loss.The second one is to depress dark rate of the SiPMs.The last one is to decrease the number of channels involved in position reconstruction by narrowing the scintillation signal distribution function of the detector unit.

Development of a sub-millimeter position-sensitive gas detector

Abstract： Position-sensitive thin-gap gas detectors have been developed in the laboratory, based on the ATLAS Thin Gap Chamber. The signal collection structure has been redesigned while retaining other configurations to keep the good time performance of the detector. The position resolution was measured using cosmic muons for two versions of the detector and found to be 409 μm and 233 μm respectively. This paper presents the structure of these two detector prototypes, with the position resolution measurement method and results.