Energy Spread Compensation Research Articles

Emittance and energy spread compensation in future synchrotron light sources

This paper shows a result of the effect on the beam emittance and energy spread induced by active insertion device (ID) in future synchrotron light sources. The online ID magnetic gap data of Shanghai Synchrotron Radiation Facility (SSRF) was sampled to evaluate the emittance variation in an 864mRing with the beam emittance of 26 pm⋅rad. A new compensation method using two compensation wigglers was developed to simultaneously improve both the beam emittance and energy spread stability, resulting in improved brightness stability during operation.

Emittance and energy spread compensation for current and future low emittance synchrotron light sources

This paper presents the results of an analysis focused on the behavior of emittance, energy spread and radiated power, as well as their variations in relation to the complement of active insertion devices in National Synchrotron Light Source II (NSLS-II) operations. The spectra of radiated power of the installed insertion devices and analytic values of the emittance are compared to that measured by the NSLS-II online diagnostics. A conceptual design of a compensation wiggler that will maintain a constant emittance or energy spread is investigated for NSLS-II and a potential low emittance upgrade scenario.

Compact Multistage Plasma-Based Accelerator Design for Correlated Energy Spread Compensation.

The extreme electromagnetic fields sustained by plasma-based accelerators could drastically reduce the size and cost of future accelerator facilities. However, they are also an inherent source of correlated energy spread in the produced beams, which severely limits the usability of these devices. We propose here to split the acceleration process into two plasma stages joined by a magnetic chicane in which the energy correlation induced in the first stage is inverted such that it can be naturally compensated in the second. Simulations of a particular 1.5-m-long setup show that 5.5GeV beams with relative energy spreads of 1.2×10^{-3} (total) and 2.8×10^{-4} (slice) could be achieved while preserving a submicron emittance. This is at least one order of magnitude below the current state of the art and would enable applications such as compact free-electron lasers.

Single-stage plasma-based correlated energy spread compensation for ultrahigh 6D brightness electron beams

Plasma photocathode wakefield acceleration combines energy gains of tens of GeV m−1 with generation of ultralow emittance electron bunches, and opens a path towards 5D-brightness orders of magnitude larger than state-of-the-art. This holds great promise for compact accelerator building blocks and advanced light sources. However, an intrinsic by-product of the enormous electric field gradients inherent to plasma accelerators is substantial correlated energy spread—an obstacle for key applications such as free-electron-lasers. Here we show that by releasing an additional tailored escort electron beam at a later phase of the acceleration, when the witness bunch is relativistically stable, the plasma wave can be locally overloaded without compromising the witness bunch normalized emittance. This reverses the effective accelerating gradient, and counter-rotates the accumulated negative longitudinal phase space chirp of the witness bunch. Thereby, the energy spread is reduced by an order of magnitude, thus enabling the production of ultrahigh 6D-brightness beams.

Energy-spread compensation in a solenoid-based secondary radioactive beam apparatus

Methods for reducing the energy spread in low-energy short-lived secondary radioactive nuclear beams produced in a solenoid-based system are examined. In particular, the use of a tapered energy-loss absorber placed off-focus is studied and a first set of in-beam tests reported. In addition, realistic ion-optical ray-tracing time-of-flight calculations for energy-spread compensation are presented for both short-(3 m) and long-(6 m) flight path options. The advantages and disadvantages of the various techniques are discussed.

Initial-beam-loading compensation system for high-intensity electron linacs

We developed an initial-beam-loading compensation system for electron linacs. This system consists of a Δ Φ – A (phase-to-amplitude) modulator and a fast-phase detector. The Δ Φ – A modulator can modulate the phase and the amplitude of a low-power RF simultaneously. Low-power and high-power tests were successfully carried out at KEK. The result of the high-power tests show that our system can reduce the energy spread from 27 to 0.3% for a 300-mA average current. The system that we developed can be a powerful tool for initial-beam-loading compensation. In addition, a numerical calculation method using the power-flow matrix was formulated to perform a fast beam-energy calculation with a simple algorithm. This method can be used to obtain the target RF waveform for energy-spread compensation.