Statistical Properties of Undulator Radiation: Classical and Quantum Effects

This dissertation presents two experiments studying the statistical properties of the undulator radiation in the Integrable Optics Test Accelerator (IOTA) storage ring at Fermilab. The first experiment studies the turn-to-turn fluctuations in the power of the radiation generated by an electron bunch (1--3 billion electrons). Generally, these turn-to-turn fluctuations depend on the full 6D phase-space distribution of the electron bunch. This effect is related to the interference of fields radiated by different electrons. Changes in the relative electron positions and velocities inside the bunch result in fluctuations in the total emitted energy per pass in a synchrotron radiation source. This dissertation presents the most complete (to date) theoretical description of this effect. The experiment in IOTA confirms that the fluctuations depend on the shape, size, and angular divergence of the electron bunch. It reveals the possibility to measure some electron bunch parameters via the fluctuations. The bunch length has been measured by this method in previous experiments. In IOTA, it is shown that it is also possible to measure some transverse properties of the electron bunch distribution (size, angular divergence). This non-invasive electron beam diagnostic technique may be particularly beneficial for the existing and next-generation low-emittance high-brightness ultraviolet and x-ray synchrotron light sources. The second experiment studies the photon statistics of the undulator radiation generated by a single electron circulating in the ring. When there is only one electron, any classical interference-related collective effects are eliminated, and the quantum fluctuations can be studied in detail. In this experiment, on average, there is only one photocount per several hundred revolutions. The collected data are analyzed to find possible deviations from the expected Poisson process exhibiting uncorrelated detection events. In addition, the arrival times of the photocounts are used to track the longitudinal motion of the single electron and to compare it with the simulation. This allows to determine several useful parameters of the storage ring

Statistical properties of spontaneous synchrotron radiation with arbitrary degree of coherence

In a storage ring, turn-to-turn fluctuations in the intensity of spontaneous synchrotron radiation occur due to two mechanisms. The first mechanism is the quantum uncertainty in the number of emitted photons. The second mechanism is the turn-to-turn variations in the relative positions of classical pointlike electrons in the bunch. We present a unified description of both effects in the framework of quantum optics. We derive an equation for the fluctuations for an arbitrary degree of coherence, which generalizes previously reported results for temporally incoherent radiation. We compare the predictions of our calculation with a previous experiment at Brookhaven National Laboratory, where the latter mechanism was dominant and propose a new dedicated experiment in the Integrable Optics Test Accelerator (IOTA) at Fermilab, where the two mechanisms may have comparable contributions to the fluctuations. Finally, our calculation shows that the magnitude of the fluctuations is rather sensitive to the dimensions and the shape of the electron bunch, thereby indicating possible applications in beam instrumentation. In particular, the small vertical size of the flat beams in IOTA may be estimated via these fluctuations, whereas measurement by a conventional synchrotron radiation monitor is difficult due to the diffraction limit

Measurements of undulator radiation power noise and comparison with <i>ab initio</i> calculations

Generally, turn-to-turn fluctuations of synchrotron radiation power in a storage ring depend on the 6D phase-space distribution of the electron bunch. This effect is related to the interference of fields radiated by different electrons. Changes in the relative electron positions and velocities inside the bunch result in fluctuations in the total emitted energy per pass in a synchrotron radiation source. This effect has been previously described assuming constant and equal electron velocities before entering the synchrotron radiation source. In this paper, we present a generalized formula for the fluctuations with a non-negligible beam divergence. Further, we corroborate this formula in a dedicated experiment with undulator radiation in the Integrable Optics Test Accelerator (IOTA) storage ring at Fermilab. Lastly, possible applications in beam instrumentation are discussed

Beam Delivery and Beamstrahlung Considerations for Ultra-High Energy Linear Colliders

International audienceAs part of the Snowmass'21 community planning excercise, the Advanced Accelerator Concepts (AAC) community proposed future linear colliders with center-of-mass energies up to 15 TeV and luminosities up to 50$\times10^{34}$ cm$^{-2}$s$^{-1}$ in a compact footprint. In addition to being compact, these machines must also be energy efficient. We identify two challenges that must be addressed in the design of these machines. First, the Beam Delivery System (BDS) must not add significant length to the accelerator complex. Second, beam parameters must be chosen to mitigate beamstrahlung effects and maximize the luminosity-per-power of the machine. In this paper, we review advances in plasma lens technology that will help to reduce the length of the BDS system and we detail new Particle-in-Cell simulation studies that will provide insight into beamstrahlung mitigation techniques. We apply our analysis to both $e^+e^-$ and $\gamma\gamma$ colliders

Beam delivery and beamstrahlung considerations for ultra-high energy linear colliders

As part of the Snowmass'21 community planning excercise, the Advanced Accelerator Concepts (AAC) community proposed future linear colliders with center-of-mass energies up to 15 TeV and luminosities up to 50 × 1034 cm-2 s-1 in a compact footprint. In addition to being compact, these machines must also be energy efficient. We identify two challenges that must be addressed in the design of these machines. First, the Beam Delivery System (BDS) must not add significant length to the accelerator complex. Second, beam parameters must be chosen to mitigate beamstrahlung effects and maximize the luminosity-per-power of the machine. In this paper, we review advances in plasma lens technology that will help to reduce the length of the BDS system and we detail new Particle-in-Cell simulation studies that will provide insight into beamstrahlung mitigation techniques. We apply our analysis to both e + e - and γγ colliders. The challenges and solutions described in this paper are considered independently. A unified, self-consistent concept for a BDS system for a 15 TeV linear collider will be the subject of future work

First Results of the IOTA Ring Research at Fermilab

The IOTA ring at Fermilab is a unique machine exclusively dedicated to accelerator beam physics R&D. The research conducted at IOTA includes topics such as nonlinear integrable optics, suppression of coherent beam instabilities, optical stochastic cooling and quantum science experiments. In this talk we report on the first results of experiments with implementations of nonlinear integrable beam optics. The first of its kind practical realization of a two-dimensional integrable system in a strongly-focusing storage ring was demonstrated allowing among other things for stable beam circulation near or at the integer resonance. Also presented will be the highlights of the world’s first demonstration of optical stochastic beam cooling and other selected results of IOTA’s broad experimental program