SLAC, Menlo Park, California, USA
KEK, Ibaraki, Japan
CERN, Geneva, Switzerland
The next generation of future linear colliders (LC) demands nano-meter beam sizes at the interaction point (IP) in order to reach the required luminosity. The final focus system (FFS) of a LC is meant to deliver such small beam sizes. The Accelerator Test Facility (ATF) aims to test the feasibility of the new local chromaticity correction scheme which the future LCs are based on. To this end the ATF2 nominal and ultra-low β* lattices are design to vertically focus the beam at the IP to 37nm and 23nm, respectively if error-free lattices are considered. However simulations show that the measured field errors of the ATF2 magnets preclude to reach the mentioned spot sizes. This paper describes the optimization of high order aberrations of the ATF2 lattices in order to minimize the detrimental effect of the measured multipole components for both ATF2 lattices. Specifically three solutions are studied, the replacement of the last focusing quadrupole (QF1FF), insertion of octupole magnets and optics modification. By applying the mentioned cures the design vertical beam size at the IP is almost recovered for both ATF2 lattices.
KEK, Ibaraki, Japan
RISE, Tokyo, Japan
We have developed a compact X-ray source via inverse Compton scattering (ICS) between multi-bunch electron beam and a laser pulse stacked in an optical cavity at Laser Undulator Compact X-ray (LUCX) accelerator in KEK. Since the autumn of 2011, we have begun X-ray imaging test. In the beginning, it had taken two hours to get an X-ray image because of low intensity of X-ray with 104 photons/pulse. To get a clear X-ray image in a shorter period of times, we have upgraded the accelerator, which consists of a 3.6 cell photo-cathode rf-gun, a 12cell standing wave accelerating structure and a 4-mirror planar optical cavity. The target intensity of an electron beam is 500nC/train with 1000 bunches at 30 MeV. The one of laser pulse is also 6mJ/pulse. The expected number of X-ray is 1.7x107 photons/train with 10% bandwidth. We have already started the multi-bunch beam generation and X-ray imaging test after upgrade. The accelerator produces 24 MeV beam with the total charge of 180nC in 150 bunches per pulse. The aging process is also continued to increase energy and intensity. We will report the results of the beam test and future plan of the development of a compact X-ray source at LUCX.
Waseda University, Tokyo, Japan
KEK, Ibaraki, Japan
We have been studying on a system to measure ultra-short electron beam bunch length at Waseda University. We adopted the rf-deflector system which can convert the longitudinal distribution to transverse by sweeping the electron bunch. We used HFSS for designing the rf-deflector cavity and GPT for beam tracking. In order to achieve the desired magnitude of magnetic field in the rf-deflector, we decided to use a 2-cells cavity of rectangular structure. Finally we optimized the design for the rf-deflector which is operating on π-mode, standing wave, dipole (TM120) mode at 2856 MHz. We have confirmed this rf-deflector has enough performance, which is 100 femt seconds bunch measurement, by GPT simulations. Now we have finished manufacturing with the collaboration of High Energy Accelerator Research Organization (KEK). We could adjust resonant frequency to 2856 MHz and combine the waveguide with the rf-deflector precisely. We will integrate the rf-deflector into an S-band Cs-Te photocathode rf electron gun system in Waseda University, and carry out bunch length measurement in this summer. In this conference, we will report the present progresses and future plan.
Waseda University, Tokyo, Japan
AIST, Tsukuba, Ibaraki, Japan
KEK, Ibaraki, Japan
JSPS Grant-in-Aid for Young Science (B) 23740203 and Scientific Research (A) 10001619
