The Compact Pulsed Hadron Source (CPHS) project that was launched in September 2009 at Tsinghua University has reached a first commissioning stage in conjunction with on-going activities to fulfill the eventual design goal of a ~10 13 n/s epithermal-to-cold neutron yield for education, instrumentation development, and industrial applications. Here, we report the latest progress on the design, fabrication, engineering of the 13 MeV/16 kW proton accelerator system, the neutron target station and neutron beamlines, especially regarding the successful delivery of the first 3-MeV proton beam and the realization of the first neutron generation in 2013.

In this paper, the Child–Langmuir law and Langmuir–Blodgett law are generalized to the relativistic regime by a simple method. Two classical laws suitable for the nonrelativistic regime are modified to simple approximate expressions applicable for calculating the space-charge-limited currents of one-dimensional steady-state planar diodes and coaxial diodes under the relativistic regime. The simple approximate expressions, extending the Child–Langmuir law and Langmuir–Blodgett law to fit the full range of voltage, have small relative errors less than 1% for one-dimensional planar diodes and less than 5% for coaxial diodes.

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This paper describes the measurement of the transverse, two-dimensional profile of the high current proton beam in the linac at the Tsinghua University, by tomography mapping using a rotatable multi-wire scanner. The experiment is conducted at a beam energy of 3 MeV, a peak current of up to 32 mA, a repetition frequency of 20 Hz, and a beam pulse width of 50 μs. The transverse density distribution is reconstructed utilizing the algebraic reconstruction technique (ART), by using the beam profiles measured at different rotation angles. The beam profile, measured at a fixed rotation angle, is obtained by 19 parallel carbon wires mounted on one board of the wire scanner monitor (WSM) moving along a straight line with a step increment of 0.1 mm. The results gathered from the computer tomography (CT) method could be verified by an independent profile measurement downstream of a multiple-slit aperture. This paper presents first measurement results of the high current proton beam during normal operation of the linac at the Tsinghua University. A dynamic range of 10 2 for the two-dimensional distribution was achieved.

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