Generating picosecond x-ray pulses in synchrotron light sources using dipole kickers

The duration of the x-ray pulse generated at a synchrotron light source is typically tens of picoseconds. Shorter pulses are highly desired by the users. In electron storage rings, the vertical beam size is usually orders of magnitude less than the bunch length due to radiation damping; therefore, a shorter pulse can be obtained by slitting the vertically tilted bunch. Zholents proposed tilting the bunch using rf deflection. We found that tilted bunches can also be generated by a dipole magnet kick. A vertical tilt is developed after the kick in the presence of nonzero chromaticity. The tilt was successfully observed and a 4.2-ps pulse was obtained from a 27-ps electron bunch at the Advanced Photon Source. Based on this principle, we propose a short-pulse generation scheme that produces picosecond x-ray pulses at a repetition rate of 1–2 kHz, which can be used for pump-probe experiments.

Figure 1

Vertical decoherence due to longitudinal diffusion. The parameters are $C_y=3.5$, ${\nu }_s=0.0078$, ${\sigma }_{\delta }=9.6\times {10}^{-4}$, and $a_E=1.2\times {10}^{-4}$. The red envelop is given by Eq. (9) but with $\mu =0$ and $a_y=0$, the oscillation is obtained from simulation.

Figure 2

The side views of a bunch at turn 63 to 67 after a vertical kick.

Figure 3

The sinusoidal fit to the bunch slice centroid of turn 72. The fit function is $y=y_0+A_y\sin (\omega t+\varphi )$, $\omega =23.35{\mathrm{ps}}^{-1}$ is calculated from Eq. (6), $A_y=1.19\mathrm{mm}$ and $\varphi =2.92$ are obtained from fitting. Equation (6) gives $A_{y,\mathrm{cal}}=1.15\mathrm{mm}$.

Figure 4

The fit between ${\sigma }_y^2$ and $⟨y⟩$ for turn 48. The red crosses are obtained from five images of the same turn, the black curve is a hypobola fit. The fit result is ${\sigma }_y^2\propto -0.775⟨y{⟩}^2$. The predicted coefficient is $-0.113$.

Figure 5

The center angle changes with time.

Figure 6

The ${\sigma }_y^2$ of the center slice changes with turn number.

Figure 7

The length of the long-time-overlapped pulses. Red crosses, without the slit; blue squares, with the slit.

Figure 8

The average length of the slitted pulse when the time jitter is removed.

Figure 9

The short-pulse generation scheme.