Far Infrared Coherent Synchrotron Edge Radiation at ANKA

Abstract

A synchrotron radiation source emits coherent infrared (IR) radiation when the electron bunch length is comparable to the wavelength of the emitted radiation (see for example [1,2]). To generate coherent radiation in the far IR (THz) region, a 'low alpha mode' has been devised at the ANKA storage ring operating at 1.3 GeV. The corresponding lattice has a significantly reduced momentum compaction factor. The spectral dependence of the emitted radiation is recorded at the ANKA-IR beam line, where the synchrotron light is produced in the fringe field of a bending magnet [3]. This edge radiation has the advantage of being more collimated than constant field radiation. This allows the observation of frequencies down to 1 cm −1 through a modest vertical aperture, which would not be possible with classical constant field emission due to the increasing beam divergence with decreasing frequency. The onset of coherent emission is found at a synchrotron frequency of about 10 kHz. At 5 kHz, an intensity enhancement of up to 5 orders of magnitude, with respect to the incoherent emission, is observed in the spectral range between 1 and 65 cm −1 .

Probability of radiation of twisted photons in the infrared domain

“…The only restriction is that the breaks of the trajectories (30) are located at one point and this point lies on the detector axis. In particular, the symmetry property (41) is fulfilled in the far infrared for the radiation produced by charged particles moving along the arbitrary trajectories with asymptotes (23). The trajectory of the form (30) does not possess a distinguished length scale when x 0 = y 0 = 0.…”

Cold vacuum chamber for diagnostics: Instrumentation and first results

“…The resistive wall heating model nicely reproduces the measured values of the beam heat load to the cold beam pipe of the superconducting undulator built by ACCEL Instruments GmbH, Bergisch Gladbach, Germany, at the synchrotron light source ANKA in the so-called low alpha operation mode of the machine, where the electron bunches are shortened to a few ps [5] to generate coherent synchrotron radiation [6]. During the normal user operation mode of ANKA and for the other superconducting cold bore wigglers installed in MAX-II and in the Diamond Light Source (DLS), the estimated values of the beam heat load are higher than the values calculated from synchrotron radiation from the upstream bending magnet and resistive wall heating.…”

High throughput data streaming of individual longitudinal electron bunch profiles

“…During the measurements, the storage ring was operated at a beam energy of 1.3 GeV, with a radio frequency (RF) voltage of 1500 kV and a bunch current of 0.35 mA stored in a single bunch (for additional parameters see [12]). The storage ring was operated in the so-called low-α c mode [21] compressing the electron bunch length to a few picoseconds. Our setup, displayed in Figure 1, is based on well-known techniques for single-shot electro-optical sampling measurement of THz field transients [13].…”