Beam halo is an important factor in any high intensity accelerator. It can cause difficulties in the control of the beam, emittance growth, particle loss and even damage to the accelerator. It is therefore essential to understand the mechanisms of halo formation and its dynamics in order to control and minimize its effects. Experimental measurement of the halo distribution is an important tool for such studies. In this paper, we present a new adaptive masking method that we have developed to image beam halo, which uses a digital micro-mirror-array device (DMD). This method has been thoroughly investigated in the laboratory using laser and white light sources, and with real beams produced by the University of Maryland Electron Ring (UMER). A high dynamic range ~10(5) has been demonstrated with this new method and recent studies indicate that this number can be exceeded for more intense beams by at least an order of magnitude. The method is flexible, easy to setup and can be used at any accelerator or light source. We present the results of our measurements of the performance of the method and images of beam halos produced under various experimental conditions.
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