Abstract. Time-resolved experimental techniques are increasingly abundant at storage ring facilities. Recent developments in accelerator technology and beamline instrumentation allow for simultaneous operation of high-intensity and timing-based experiments. The MAX IV facility is a state-of-the-art synchrotron light source in Lund, Sweden, that will come into operation in 2016. As many storage ring facilities are pursuing upgrade programs employing strong-focusing multibend achromats and passive harmonic cavities (HCs) in high-current operation, it is of broad interest to study the accelerator and instrumentation developments required to enable timing-based experiments at such machines. In particular, the use of hybrid filling modes combined with pulse picking by resonant excitation or pseudo single bunch has shown promising results. These methods can be combined with novel beamline instrumentation, such as choppers and instrument gating. In this paper we discuss how these techniques can be implemented and employed at MAX IV.

The ongoing trend towards synchrotron light storage rings with ultralow emittance lattices leads to greater challenges to achieve beam stability, sufficient Touschek lifetime, low heating of machine components, and conservation of the emittance at high bunch charge. One solution to meet these challenges is to lengthen the electron bunches with harmonic cavities. Many upgrade proposals therefore include harmonic cavities to enhance the machine performance. This is also the case for the MAX IV 3 GeV storage ring, which employs passive third harmonic cavities to achieve up to five times bunch lengthening. Unfortunately, the performance of the harmonic cavities is reduced if a gap in the fill pattern is required. In this paper, the effect on synchronous phase and bunch length due to a gap in the fill pattern for rings with passive harmonic cavities is calculated in a self-consistent way including the bunch form factor. The aim is to achieve faster simulation of various schemes for compensating a gap compared to multiparticle tracking. A new semianalytical method based on an iterative matrix formulation is presented, as well as a singleparticle tracking code including the bunch form factor. The results from these methods are compared to both results from a multiparticle tracking code and measurements at the MAX IV 3 GeV storage ring. The importance of including the bunch form factor in simulations is evaluated and discussed.

Fi.+ 1. Optical simulation experiment to verify feasibility of the "chirped" coded aperture. Fig. 2. Decoded image obtaimd in e x b t illustrated in Fig. 1. are negligible and the light travek a straight line. path. The wmpression filter was a surface acoustic wave delay line [9] having a compression ratio of 50 at a center frequency of about 14 MHz. ThedecodedimageisshowninFig.2.The vextical bars result from the carrier frequency on the compressed puke since no filtering was resolution corresponds to a compression ratio of about 40, rather close to the predicted value ofSO.TheshadingofoneconwoftheEis due to uneven illumination in the decoding step. In s u m m a r y , we have demonstrated that a linearspatialchirpcanbeusedasacoded aperture, with a significant inaease in photon collection efkienq. Although the linear chirp may be regarded as a one-dimensional & -a x i s Fresnel u~e plate, this system has the advantage over the zone plate apertures previously reported [a], [7] that the critical photographic steps are eliminated and essentially real-time processing can be obtained. employed after video detection. The measured ACKNOWLEDGMENT The author would like to thank D. Wilson for assistance with the experimental work, and G. DeMeester, F. Horrigan, J. Sage. and R. Bierig for valuable discussious. The excellent design for the delay line was contributed by P. Meyer. HARRLWN H. BARRETT Raytheon Res. Div. Waltham, Mass. 02154 REFER-[I] H. 0. Anger, Ykintillation camera, . ' in Instrummtarion in Nwkm Malicinr, C. 3. Him, Ed. vol. I . Near York: Acadnnic Pres, 1967. p. 501. [2l M. A. Bender and M. Blau, "The autofluoroscope," 131 J. R. Mallard and R. 3. Wilh. "The A b a gamma-scop~, an image intenrifia c a m e r a : in Mea7ca.l RRdioirotope Scintigraphy, vd. I. V i Austria : Int. Atomic Eoergy Agency, 1969, p. Scintigraphy. vol. 1. V i m . Alatria: Interna-

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