Optical dissector for longitudinal beam profile measurement

Abstract

Experimental study of beam profile dynamics at circular accelerator was carried out due to creation of the sources of synchrotron radiation and colliders, at which the beam consists of several tens or hundreds of bunches distributed over the separatrices. Dynamics of a longitudinal profile of separate bunches was studied by means of streak cameras, however, they are not applied for regular, permanent diagnostics unlike beam position monitors or CCD cameras Streak cameras are very good for study of single processes, not for routine accelerator performance. BINP SB RAS has developed the optical analyzer on the basis of LI-602 dissector which was used for studying the beam dynamics at VEPP-2, VEPP-3, VEPP-4, electron-positron colliders and other electron circular accelerators: Siberia-2, ESRF, etc The dissector provides permanent measurements of the longitudinal beam profile. Nevertheless, the ultimate temporal resolution of the device is about 20 picoseconds Now it is not enough for application at modern accelerators. In this paper we describe the first experimental results obtained with the dissector of the next generation. The measured technical resolution of this device is about 2 picoseconds, but we believe that this value can be improved.

Direct temporal-resolution calibration of new-generation dissector

“…At that stage of the study, we were not interested in dependence of temporal resolution on the phase shift of the acquired signal relative to U rf phase. Our purpose was to confirm the value of technical temporal resolution of the device stated earlier [5]. The best temporal resolution of 3,5 ps (FWHM) was measured for the 10-ps interval, as shown in Fig 5 . The average value for all pairs of pulses is 4, 5 ± 0, 6 ps.…”

“…The LI-602 dissector is a part of many optical diagnostic systems and provides temporal resolution of about 20 ps. The detailed description of the dissector operation can be found in [3,5,6]. We will remind just very common ideas of the device operation.…”

“…In this report we will describe the experimental procedure for direct and precise measurements of ultimate temporal resolution of new dissectors with the help of femtosecond laser pulses used at experimental set-up specially assembled for such a purpose at the GPI Photoelectronics Department. We intended to verify the value of technical temporal resolution of the device stated earlier [5].…”

A new station for optical observation of electron beam parameters at electron storage ring SIBERIA-2

“…The dissector LI-602 has a disadvantage of a relatively low temporal resolution τ, about 40 ps FWHM. Recently a new version of the dissector with τ ≈ 3 ps was developed [10,11]. The instrumental function of the dissector can be easily measured with a permanent light source [10], but the true temporal resolution of the device depends on the stability of the jitter of the RF sweep voltage of the dissector relative to the arrival time of electron bunch to the source point.…”

“…With appearance of coherent oscillations, the shape of the beam profile acquired by the dissector is distorted because of the beats of 50-Hz slow sweep of the dissector and beam oscillations with synchrotron frequency because the beam image oscillates across the image slits of the dissector [10]. The character of the distortion depends on the relation between the amplitude of the oscillations and the bunch length.…”