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Tian, Kai

Publications and source records attributed to Tian, Kai.

4 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Optical synchrotron radiation beam imaging with a digital mask

The 3GeV SPEAR3 synchrotron light source operates in top-up injection mode with up to 500mA circulating in the storage ring (equivalently 392nC). Each injection pulse contains only 40-80 pC producing a contrast ratio between total stored charge and injected charge of about 6500:1. In order to study transient injected beam dynamics during User operations, it is desirable to optically image the injected pulse in the presence of the bright stored beam. In the present work this is done by re-imaging visible synchrotron radiation onto a digital micro-mirror-array device (DMD), which is then used as an optical mask to block out light from the bright central core of the stored beam. The physical masking, together with an asynchronously-gated, ICCD imaging camera makes it is possible to observe the weak injected beam component on a turn-by-turn basis. The DMD optical masking system works similar to a classical solar coronagraph but has some distinct practical advantages: i.e. rapid adaption to changes in the shape of the stored beam, high extinction ratio for unwanted light and minimum scattering from the primary beam into the secondary optics. In this paper we describe the DMD masking method, features of the high dynamic range point spread function for the SPEAR3 optical beam line and measurements of the injected beam in the presence of the stored beam.

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

Trajectory studies for SPEAR3 LTB

In this note, trajectory stability in SPEAR3 Linac-to-booster (LTB) transport line is studied. It is observed that an electron gun body temperature variation or a linac RF phase variation may introduce beam energy variation which then translates into a trajectory change after certain dipole magnets. Long time BPM resolution is also investigated, plus a calculation on the initial beam angle variation. Beam trajectory is controlled for a good injection efficiency into the booster, by using the measured response matrix of certain steering correctors. Dispersion is also measured for a future implementation of a beam energy feedback.

ACCPHY, ACCSYS↗