Laserwire at the Accelerator Test Facility 2 with Sub-Micrometre Resolution

A laserwire transverse electron beam size measurement system has been developed and operated at the Accelerator Test Facility 2 (ATF2) at KEK. Special electron beam optics were developed to create an approximately 1 x 100 {\mu}m (vertical x horizontal) electron beam at the laserwire location, which was profiled using a 150 mJ, 71 ps laser pulse with a wavelength of 532 nm. The precise characterisation of the laser propagation allows the non-Gaussian transverse profiles of the electron beam caused by the laser divergence to be deconvolved. A minimum vertical electron beam size of 1.07 ${\pm}$ 0.06 (stat.) ${\pm}$ 0.05 (sys.) {\mu}m was measured. A vertically focussing quadrupole just before the laserwire was varied whilst making laserwire measurements and the projected vertical emittance was measured to be 82.56 ${\pm}$ 3.04 pm rad.Comment: 17 pages, 26 figures, submitted to Phys. Rev. ST Accel. Beam

Radiation of a Charge Exiting Open-Ended Waveguide with Dielectric Filling

We consider a semi-infinite open-ended cylindrical waveguide with uniform dielectric filling placed into collinear infinite vacuum waveguide with larger radius. Electromagnetic field produced by a point charge or Gaussian bunch moving along structure's axis from the dielectric waveguide into the vacuum one is investigated. We utilize the modified residue-calculus technique and obtain rigorous analytical solution of the problem by determining coefficients of mode excitation in each subarea of the structure. Numerical simulations in CST Particle Studio are also performed and an excellent agreement between analytical and simulated results is shown. The main attention is paid to analysis of Cherenkov radiation generated in the inner dielectric waveguide and penetrated into vacuum regions of the outer waveguide. The discussed structure can be used for generation of Terahertz radiation by modulated bunches (bunch trains) by means of high-order Cherenkov modes. In this case, numerical simulations becomes difficult while the developed analytical technique allows for efficient calculation of the radiation characteristics.Comment: 13 pages, 11 figure

Beam waist manipulations at the ATF2 interaction point

TH6PFP024International audienceThe ATF2 project is the final focus system prototype for ILC and CLIC linear collider projects, with a purpose to reach a 37nm vertical beam size at the interaction point. We report on techniques developed based on simulation studies to adjust the horizontal and vertical beam waists independently in the presence of errors, at two different IP locations where the beam size can be measured with different accuracies. During initial commissioning, we will start with larger than nominal β -functions at the IP, to reduce the effects from higher-order optical aberrations and thereby simplify the optical corrections needed. The first measurements in such intermediate β -configurations are reported

Q-FACTOR OF AN OPEN RESONATOR FOR A COMPACT SOFT X-RAY SOURCE BASED ON THOMSON SCATTERING OF STIMULATED COHERENT DIFFRACTION RADIATION

Abstract High-brightness and reliable sources in the VUV and the soft X-ray region may be used for numerous applications in such areas as medicine, biology, biochemistry, material science, etc. We have proposed a new approach to produce the intense beams of X-rays in the range of 500 ω ≤ eV based on Thomson scattering of Coherent Diffraction Radiation (CDR) on a 43 MeV electron beam. CDR is generated when a bunch of charged particles moves in the vicinity of an obstacle if a radiation wavelength is comparable to or longer than the bunch length. In our case the CDR is generated by bunches passing through holes in two mirrors formed an open resonator. In this report the status of the experiment, the first CDR measurements at the multibunch beam of the LUCX facility and general resonator tuning procedure will be reported

Experimental validation of a novel compact focusing scheme for future energy-frontier linear lepton colliders.

A novel scheme for the focusing of high-energy leptons in future linear colliders was proposed in 2001 [P. Raimondi and A. Seryi, Phys. Rev. Lett. 86, 3779 (2001)]. This scheme has many advantageous properties over previously studied focusing schemes, including being significantly shorter for a given energy and having a significantly better energy bandwidth. Experimental results from the ATF2 accelerator at KEK are presented that validate the operating principle of such a scheme by demonstrating the demagnification of a 1.3 GeVelectron beam down to below 65 nm in height using an energy-scaled version of the compact focusing optics designed for the ILC collider

DESIGN OF AN OPTICAL DIFFERACTION RADIATION BEAM SIZE MONITOR AT SLAC FETB

We design a single bunch transverse beam size monitor which will be tested to measure the 28.5 GeV electron/positron beam at the SLAC FFTB beam line. The beam size monitor uses the CCD images of the interference pattern of the optical diffraction radiation from two slit edges which are placed close to the beam path. In this method, destruction of the accelerated electron/positron beam bunches due to the beam size monitoring is negligible, which is vital to the operation of the Linear Collider project

A Laser-Wire System at the ATF Extraction Line

A new laser-wire (LW) system has been installed at the ATF extraction line at KEK, Tsukuba. The system aims at a micron-scale laser spot size and employs a mode-locked laser system. The purpose-built interaction chamber, light delivery optics, and lens systems are described, and the first results are presented