The Beijing intense slow positron beam facility is based on the 1.3 GeV linac of Beijing Electron- Positron Collider(BEPC)aiming to produce mono-energetic intense slow positron beam for material science investigation.The plugged-in ^(22)Na based slow positron beam section has been newly constructed to supply continuous beam time for the debugging of positron annihilation measurement stations and improve the Beijing intense slow positron beam time using efficiency.Performance testing result of the plugged-in ^(22)Na based slow positron beam facility are reviewed in this paper,with the measurement of the beam transport efficiency,the view of beam spot,the adjustment of beam position,the measurement of beam intensity and energy spread etc.included.
This paper describes the development and application of an intense slow positron beam at IHEP with regard to its two main components.The Variable-Energy Positron Lifetime Spectroscopy (VEPLS) based on the pulsing system consisting of a chopper,a prebuncher and a buncher has been constructed in order to meet the needs of materials science development.At present,the time resolution of the VEPLS can easily reach about 386 ps with a peak-to-background ratio of about 600:1.A plugged-in ^(22)Na positron source section for adjusting the newly built experimental station and for increasing the beam operation efficiency has been constructed.A slow positron beam with an intensity of 2.5×10~5 e^+/s and the beam profile whose diameter is 10 mm has been obtained;the moderation efficiency of the tungsten mesh moderator reaches 5.1×10^(-4) as calculated with an original positron source activity of 52 mCi.
