>> Scientific Significance

Neutron, like x-ray, is a powerful means to probe the structure of the microscopic world. Moreover, neutron has some special properties that x-ray does not possess: 1)neutron bears with no charge, but with magnetic vector; 2)neutron owns high ability of penetration through a matter; 3)neutron is much more sensitive to light element and isotopes; 4)neutron can detect both the structure and dynamics behavior of a matter. For these reasons, neutron scattering becomes a complementary means to x-ray in the advanced researches in physics, chemistry, biology, life science, material science, new energy, as well as in applications.

Two high performance x-ray sources based on synchrotron radiation facility are operated for users at Beijing (BSRF at IHIIP)and Hefei (NSRF at USTC), and another new one will soon be commissioned in Shanghai (Shanghai Light Source). However there is no high performance pulsed neutron source in China. To meet the increasing demand from user community, China decided to build a. world-class spallation neutron source, called CSNS. It can provide users a neutron scattering platform with high flux, wide wavelength range and high efficiency. The pulsed-beam feature allows studies not only on the static structure but also the dynamic mechanisms of the microscopic world. The high-flux pulsed neutrons, muons, and protons from CSNS will also complement continuous-wave neutrons from the China Advanced Research Reactor (CARR).

　　　　　  

>> Facilities

CSNS mainly consists of an H- linac and a proton rapid cycling synchrotron. It is designed to accelerate proton beam pulses to 1.6 GeV kinetic energy at 25 Hz repetition rate, striking a solid metal target to produce spallation neutrons. As shown in Table 1, the accelerator is designed to deliver a beam power of 120 kW with the upgrade capability to 500 kW by raising the linac output energy and increasing the beam intensity

　

1, Accelerator

Negative hydrogen ions (H-) are firstly generated from a Penning ion source. RFQ accelerator forms beam bunches at 324MHz RF frequency and accelerates the beam to 3 MeV丁he four-vane RFQ is similar to the one previously developed at IHEP for the ADS program. Four DTL tanks further increase the beam energy to 81 MeV. A long beam transport line is followed with the DTL linac to send the beam a rapid cycling synchrotron (RCS) accelerator. In this beam line, a sufficient space is reserved for the additional linac structures, such as DTL tanks or superconducting linac, for the power upgrade in future. The H- beam is stripped to become proton beam and injected into the RCS ring. In the ring the proton beam is accumulated to a high current pulse and then accelerated to 1.6 GeV.

2, Target

The high-energy proton beam extracted from the accelerator bombards on the target to generate neutrons through spallation reaction. Tungsten is used as the target material with heavy water as the cooling media. The high-energy neutrons are then cooled down by moderator to become thermal or cold neutrons, which meet for the neutron scattering experiments. A rotating target mockup in vertical direction is under development as a backup of the horizontal target on the trolley

 

 

3, Instruments

CSNS' First target station accommodates at least 18 neutron scattering instruments. However, due to limited project funds, only three day-one instruments are supported: a high intensity diffractometer, a broad Q-range small angle diffractometer, and a multi-purpose refleetometer. Efforts are made to attract interested institutes and universities to invest in dedicated neutron instruments

 

>> Schedule

CSNS construction is expected to Start in 2009 and will last 6.5 years. Facility commissioning will take about 1.5 years to reach the specified beam power on the target and neutron flux. The normal operation for users is foreseen in 2017

>> Site

CSNS construction site locates at Dongguan, Guangdong province. It is about 85km from Guangzhou and about 125 km from Hong Kong. IHEP will setup a new branch on the present green field. CSNS will be the first large scientific facility in the south China where the econom3 go very rapidly. It is expected the CSNS construction and operation will have positive effects in promoting the sciences and high-tech development in the area.