G. Di Pirro

Effects of nonlinear terms in the wiggler magnets at DA/spl Phi/NE

Analysis of the experimental observations and comparison with magnetic measurements have pointed out relevant nonlinear terms in the DA/spl Phi/NE wigglers and in the C corrector magnets. Different optics configurations aimed at reducing the impact of nonlinear terms have been studied and their effects on the collider performances are presented.

Status report on DA/spl Phi/NE

DA/spl Phi/NE, the Frascati LNF /spl Phi/-factory, is providing luminosity for the KLOE experiment since July 2000. A steady increase of daily integrated luminosity in KLOE has been obtained, due to interspersed machine physics studies. The main results are: increase of single bunch luminosity by reduction of the effects of nonlinear terms in the machine, background reduction, refill of the colliding beams while keeping the KLOE detector taking data and increase of stable stored current. A fraction of machine time has been used to tune luminosity and reduce background in the DEAR configuration. The luminosity delivered to DEAR was sufficient to conclude the first phase of the experiment.

Proposal of an Experiment on Bunch Length Modulation in DAφNe

Obtaining very short bunches is an issue especially for colliders but also for CSR sources. The modulation of the bunch length in a strong rf focusing regime had been proposed, corresponding to a high value of the synchrotron tune. A ring structure where the function R56 along the ring oscillates between large positive and negative values will produce bunch length modulation. The synchrotron frequency can be tuned both by the rf power and by the integral of the function R56, up to the limit of zero value corresponding to the isochronicity condition. The proposal of a bunch length modulation along the ring in DAΦNE is here described. DAΦNE lattice can be tuned to positive or negative momentum compaction values, or to structures in which the two arcs are respectively set to positive/negative integrals of the R56 function. With the installation of an extra rf system at 1.3 GHz, experiments on bunch length modulation both in the regime of high and low synchrotron tune can be realized.

Non Linear Beam Dynamics at DAPHINE

Studies and measurements have been performed at DAΦ NE to improve dynamic aperture, beam lifetime and beam-beam performance. Measured tune scans for different working points are presented. After the measurement of an octupole-like term in the wiggler field, decoherence meas- urements with wigglers on and off have been performed. The effect of this cubic term on the chromaticity and dy- namic aperture is presented. . The Kloe experiment is routinely collecting data. The non-linearities present in the machine play a major role affecting the dynamic aperture, the beam lifetime, (with relation to the background and the integrated luminosity), and the beam-beam behaviour (single bunch luminosity). The study moved from extensive beam lifetime measurements vs. betatron tunes in both rings resulting in a high sensitivity of the machine to high order resonances (section 2). The deco- herence measurements, (dynamic tracking), with the wig- glers powered on and off show the effect of a strong dependence of the tune on the betatron amplitude oscillation, (section 3). The presence of a cubic term in the wiggler is accounted for the residual non-linear chromaticity of the machine even with sextupoles off. The strength of the octupole thin lens to be taken into account in each pole, found from the chromaticity measurements, agrees with the value obtained from the measurements of the betatron tunes vs. the localised orbit bumps inside the wiggler (6). The effect on the dynamic aperture is described in section 5.

100 bunch DA/spl Phi/NE operation

The DA/spl Phi/NE collider has been operating by filling 100 consecutive buckets out of the available 120 with a gap to avoid ion trapping in the electron beam. To reduce the effect of the parasitic crossings the crossing angle has been increased up to 29 mrad and the horizontal beta function at the interaction point lowered down to 1.7 m. Moreover both transverse and longitudinal feedbacks have been optimized for this more demanding mode of operation. Comparison between 100 and 50 bunches operation in 2002 runs is presented.

Non-linear beam dynamics at DA/spl Phi/NE

Studies and measurements have been performed at DA/spl Phi/NE to improve dynamic aperture, beam lifetime and beam-beam performance. Measured tune scans for different working points are presented. After the measurement of an octupole-like term in the wiggler field, decoherence measurements with wigglers on and off have been performed. The effect of this cubic term on the chromaticity and dynamic aperture is presented.