General-purpose readout electronics for white neutron source at China Spallation Neutron Source

Detector development at the Back-n white neutron source

Purpose

Back-n is a white neutron beamline at China spallation neutron source, which was established in the year of 2018. It is a powerful facility for nuclear data measurement, neutron detector calibration, and radiation effect research.

Method

A series of detectors were built for different experiments, including beam monitoring, beam profile measurement, neutron induced secondaries (fission fragments, light charged particles and gamma) cross section measurement, and neutron resonance radiography, etc. A common digitization electronics and a cluster-based DAQ were developed for these detector systems. Most detectors have been employed at Back-n and serviced for experiments from the beginning of the beamline running.

Results and conclusion

As an overview of detectors of Back-n, the details of the detector design and the experiment performing are described in this paper. Some developing systems, e.g., MTPC and B-MCP, are also included.

Introduction of a C6D6detector system on the Back-n of CSNS

Radiative neutron capture cross sections are very important in the field of basic physics research and nuclear device R&D. The Back-n white neutron beam line of China Spallation Neutron Source (CSNS) is the first spallation neutron beam line in China. On the purpose for radiative neutron capture cross section measurement, a C6D6detector system was built in the Back-n experimental station. The pulse height weighting technique (PHWT) was used to make the system’s detective efficiency independent of the cascade path and the energy of cascade gamma rays. The neutron energy spectrum was measured for the energy between 1eV and 80keV with a6Li loaded ZnS scintillation detector. Besides, a testing experiment with197Au and169Tm samples was carried out to examine this system. According to the preliminary results, this C6D6detector system can be used to perform neutron capture cross section measurement.

Measurement of the neutron energy spectrum of Back-n #ES1 at CSNS

The China spallation neutron source (CSNS) was built and started running since 2018. It produces neutrons by impinging 1.6 GeV protons onto a tungsten target with 25 Hz repetition frequency. A beam line exploiting the back-streaming neutrons (Back-n) was built mainly for nuclear data measurement and started commissioning simultaneously with CSNS in 2018. There are two experimental endstations along the Back-n beam line: endstation 1 (#ES1) with a neutron flight path of about 55 m and endstation 2 (#ES2) with about 76 m. The neutron energy spectra of both #ES1 and #ES2 were measured since it is important for feasibility study and analysis. In this paper, the measurement of the neutron energy spectrum of Back-n #ES1 is reported. It is measured by a multi-layer fission chamber using the 235U samples as the neutron converters. The neutron energy spectrum from 0.1 eV to 30 MeV is obtained. The integral neutron flux (from 0.1 eV to 30 MeV) normalized to the proton beam power of 100 kW is 1.55×107 neutrons/cm2/s.