Experimental 3-dimensional tracking of the dynamics of a single electron in the Fermilab Integrable Optics Test Accelerator (IOTA)

Abstract

We present the results of experimental studies on the transverse and longitudinal dynamics of a single electron in the IOTA storage ring. IOTA is a flexible machine dedicated to beam physics experiments with electrons and protons. A method was developed to reliably inject and circulate a controlled number of electrons in the ring. A key beam diagnostic system is the set of sensitive high-resolution digital cameras for the detection of synchrotron light emitted by the electrons. With 60–130 electrons in the machine, we measured beam lifetime and derived an absolute calibration of the optical system. At exposure times of 0.5 s, the cameras were sensitive to individual electrons. Camera images were used to reconstruct the time evolution of oscillation amplitudes of a single electron in all 3 degrees of freedom. The evolution of amplitudes directly showed the interplay between synchrotron-radiation damping, quantum excitations, and scattering with the residual gas. From the distribution of measured single-electron oscillation amplitudes, we deduced transverse emittances, momentum spread, damping times, and beam energy. Estimates of residual-gas density and composition were calculated from the measured distributions of vertical scattering angles. Combining scattering and lifetime data, we also provide an estimate of the aperture of the ring. To our knowledge, this is the first time that the dynamics of a single electron are tracked in all three dimensions with digital cameras in a storage ring.

The design of Optical Stochastic Cooling for IOTA

“…The work with a single electron in a storage ring was pioneered by scientists of BINP, Novosibirsk [31]. Recently single electron studies we also carried out in IOTA [32]. That allowed us to obtain the first-hand experience in such operations.…”

Statistical Properties of Undulator Radiation

“…The detection arrival times can be used to study the synchrotron motion of a single electron and to infer some dynamical parameters of the storage ring, such as the rms rf cavity phase jitter and the synchrotron motion period as a function of amplitude. This diagnostics of the longitudinal motion can complement the diagnostics of the transverse motion [19,20] and facilitate a complete 3D tracking of a single electron in a ring.…”

Single electron in a storage ring: a probe into the fundamental properties of synchrotron radiation and a powerful diagnostic tool

“…By comparing the measurements with the model, we inferred the rms rf cavity phase jitter and the synchrotron motion period as a function of amplitude. We are currently developing experiments and techniques to combine timing information of longitudinal motion with transverse diagnostics [12,43]. This will enable a complete 3D tracking of a single electron in the ring and provide further insights in the physics of nonlinear integrable optics [44][45][46].…”

“…In the Integrable Optics Test Accelerator (IOTA) at Fermilab [11], injection and storage of a small countable number of electrons was demonstrated in 2018. Experiments with single electrons at 100-150 MeV with lifetimes of minutes to hours are now part of standard operations [12]. This capability has opened up a new research program on the fundamental properties of synchrotron radiation, beam cooling, nonlinear dynamics, and novel diagnostic techniques.…”