Back-n white neutron facility at CSNS and first-year nuclear data measurements

Abstract

Back-streaming neutrons through the incoming proton channel at the spallation target station of China Spallation Neutron Source (CSNS) were exploited to build a white neutron beam line (the so-called Back-n). With a proton beam of 100 kW in beam power and 1.6 GeV in kinetic energy and a thick tungsten target and modest moderation by the cooling water through the target slices, the neutron beam is very intense which is in the order of 7.0×106 n/cm2/s at 77 m from the target and has an excellent energy spectrum spanning from 0.5 eV to 200 MeV. In addition, the time resolution related to the time-of-flight measurements is very good for neutron energy determination. Altogether, it makes the CSNS Back-n one of the best white neutron sources in the world and very suitable for nuclear data measurements, especially for neutron-induced cross-section measurements. Since the completion of the Back-n beamline and four physics spectrometers in March 2018, the first batches of experiments on nuclear data measurements have been carried out, which are summarized in this article.

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

“…The pulse features an 86ns pulse width. The beam peak intensity reaches up to 40A when the beam power is 100kW [5]. The signal traveling along the cable to WNS Control Station, is attenuated to 8V peak amplitude when the RCS runs full power, 100kW, and 0.8V peak amplitude with the 10kW beam power.…”

“…The characteristics of the signal mainly depend on the operation mode, the operation mode is detailed in ref. [5]. And it is called FCT-T0.…”

“…Neutron energy spectrum is a very important part for the measurement, the TOF (time of flight) is applied for the acquisition of neutron energy [5]. The kinetic energy of the neutrons is calculated relying on the measurement of the arrival T time and the starting time of the neutrons.…”

Initial years’ neutron-induced cross-section measurements at the CSNS Back-n white neutron source *

“…A white neutron beam facility (the so-called Back-n white neutron source) was built at the China Spallation Neutron Source (CSNS) [1][2][3][4]. It employs back-streaming neutrons from the proton beam channel to the spallation target, which has properties of high neutron flux, wide energy spectrum, and good time structure for timeof-flight measurements.…”

“…Guohui Zhang(张国辉) 6 Xichao Ruan(阮锡超) 7 Xiaoguang Wu(吴晓光) 7 Qi An(安琪) 1,8 Jiangbo Bai(白江博) 5 Jie Bao(鲍杰) 7 Yu Bao(鲍煜) 2,3 Ping Cao(曹平) 1,8…”