Summary :
High intensity photon beams have various applications in advanced accelerators, from medical imagery (X-rays) to high energy physics (polarized positron beams, photon colliders) passing by nuclear physics (fundamental and applied). They can be obtained by laser-Compton backscattering off electrons, the main advantage being the possibility to produce high flux monochromatic photon beams. In this context, an optical cavity is a unique system to reach the requested laser beam power at high repetition rates. LAL and KEK are developing such light sources and are trying to push forward the technical limits to increase the maximal power stored in these optical cavities.

French members :
A. Martens, K. Cassou, I. Chaikovska, R. Chiche, K. Dupraz, P. Favier, D. Jehanno, V. Soskov, T. Williams, F. Zomer

Japanese members :
Y. Honda, T. Akagi, S. Araki, M. Fukuda, U. Hosaka, A. Kosuge, T. Omori, K. Sakaue, T. Takahashi, N. Terunuma,

References :
[1] J Bonis et al 2012 JINST 7 P01017, http://dx.doi.org/10.1088/1748-0221/7/01/P01017
[2] T Akagi et al 2012 JINST 7 P01021, http://dx.doi.org/10.1088/1748-0221/7/01/P01021
[3] ThomX Technical Design Report, http://hal.in2p3.fr/in2p3-00971281

Summary:
We will test a new granular converter consisting of small tungsten spheres in a hybrid positron source configuration. The beam test is scheduled for the summer of 2014 or later at the KEK injector linac. We have already built the granular converters with four different thicknesses at LAL-Orsay for this experiment. The impinging electron with beam energy of 7-8 GeV and bunched charge of 1 nC is foreseen. In these beam tests, the observations of the temperature rise will be done, putting high-precision thermocouples on the exit face of the converter. Additional observations through infrared cameras are considered. The goal of this project is to evaluate the feasibility of this new granular converter toward the high intensity positron sources.

French members :
I. Chaikovska, X. Artru, D. Dauvergne, H. Guler, R. Chehab, M. Chevallier

Japanese members :
M. Satoh, K. Furukawa, T. Kamitani, F. Miyahara, T. Suwada, K. Umemori

References:
[1] Y. Uesugi et al., Nuclear Instrum. Methods B 319 (2014) 17-23.
[2] P. Sievers et al., "Granular Converter Test at KEK"; Presented at the 8-th POSIPOL Workshop (POSIPOL2013), Argonne National Lab., Argonne, IL, U.S.A., Sep. 4-6, 2013.

Summary :
Magnetic shielding is a key technology for super-conducting RF cavities.It is necessary to optimize the shielding method, including the choice of materials and the shape of the magnetic shield, and to establish a method for quality control suitable for large-scale production.We plan to continue to evaluate the permeability of various shielding materials, and also investigate possible causes for the performance degradation of the shielding material at cryogenic temperature. We would also like to study the dependence of cavity performance on the permeability

French members :
J. Plouin, O. Napoly

Japanese members :
K. Umemori, M. Masuzawa, K. Tsuchiya

References :
[1] Mika Masuzawa, et al. “Study of Magnetic Shielding Materials and Fabrication of Magnetic Shield for Superconducting Cavities” IEEE Transactions on Applied Superconductivity, 2014. Volume: 24, Issue: 3
[2] Mika Masuzawa, Juliette Plouin, et al. “MAGNETIC SHIELDING: OUR EXPERIENCE WITH VARIOUS SHIELDING MATERIALS”, Proc. For SRF2013, Paris, 2013.
[3] Juliette Plouin, “Magnetic Shielding Activities for IFMIF/CEA and Study on the Magnetic Shielding in the FJPPL Collaboration”, presented at “MSU FRIB Workshop on Magnetic Shielding for Cryomodules” Feb.4-6, 2013.
[4] Mika Masuzawa, et al. “Magnetic Properties of Shielding Materials for Superconducting Cavities” IEEE Transactions on Applied Superconductivity, 2012. Volume: 22, Issue: 3

Summary :
SuperKEKB e+e- collider is designed to provide a very high luminosity for Belle-II experiment, using nano-beam scheme. In this context, the fast luminosity monitoring collaboration aims to develop a reliable instrumentation to measure the luminosity and provide fast input for luminosity feedback corrections as well as for luminosity optimization phase. The measurements are based on the detection of the electron or positron arising from the Bhabha scattering process at zero degree photon angle, which offers a significant amount of signal. The fast luminosity monitoring system will be set ten to thirty meters downstream of the interaction point, ideally both in the High and Low energy rings, just immediately outside the beam-pipe. Several kind of detectors are under development, combining thus complementary technologies, namely scintillator, Cerenkov counter and diamond sensor, all requiring fast readout electronics enabling both the measurements of the whole-ring averaged luminosity and the bunch by bunch luminosity.

French members :
P. Bambade, F. Bogard, D. Jehanno, V. Kubytskyi, C. Rimbault

Japanese members :
S. Uehara, Y. Funakoshi, M. Iwasaki

References :
[1] D. El Khechen, C. Rimbault, P. Bambade, “Fast Luminosity Monitoring using diamond sensors for the Super Flavour Factories SuperKEKB”, proceeding for the 5th International Particle Accelerator Conference (IPAC2014), Dresden, Germany, 15-20 June 2014.

Website :
https://www.belle2.org/

Summary :
KEK and CEA/Irfu are pursuing their effort to improve technology related to ILC cavity production/surface treatment. Presently, main steps studied are :
- Cavity Fabrication at Cavity Fabrication Facility at KEK
- Vertical Electro-polishing of cavities (VEP set-up at CEA Saclay and at Marui Galavanizing Company ltd.)
Alternative environmental-friendly surface treatments are also investigated (Electro-chemical Buffing).
The proposal mainly consists in the continuous process of cavity from fabrication at KEK through surface treatment and test at Saclay.
The aim is to optimize the process with the view of an industrial fabrication of cavities.

French members :
F. Eozénou, C. Antoine, S. Berry, C. Madec, C. Servouin,

Japanese members :
T. Saeki, H. Hayano, S. Kato, H. Monjushiro, M. Sawabe, M. Yamanaka

References :
[1] K. Nii et al., “Vertical Electro-polishing of Nb single-cell cavity using cathode with variable-geometry wings and its results of vertical test”, LINAC 2014, MOPP108.

Summary :
As a demonstrator for Future Linear Colliders (LC) with nanometer (nm) size e+-e- beams, ATF2 (Accelerator Test Facility) has achieved 44nm vertical beam size, very near to its 37nm goal. It is realized under low intensity beam and the studies on beam intensity dependence will continue. Next major step for our French and Japanese Teams is maintaining the beam position stability of 2nm at IP. To achieve this, Beam Position Monitors, used with an efficient upstream feedback, will be installed and calibrated in a vacuum chamber with internal moving mechanisms. Ground Motion (GM) sensors will be tested for the development of a new GM feedforward acting on the beam stability. Additional Beam Instrumentation like an in-vacuum diamond sensor for beam halo and linear Compton scattering measurements will be developed. This project is an ideal precision study for the training of students.

French members :
A. Jeremie, B. Aimard, P. Bambade, F. Bogard, L. Brunetti, P. Cornebise, H. Guler, V. Kubytskyi, S. Wallon, T. Yldizkaya

Japanese members :
N. Terunuma, S. Araki, K. Kubo, S. Kuroda, T. Naito, T. Okugi, T. Tauchi

References :
[1] G.White et al., Experimental Validation of a Novel Compact Focusing Scheme for Future Energy-Frontier Linear Lepton Colliders, Phys. Rev. Lett. 112 (2014) 034802.
[2] T. Okugi et al., Linear and second order optics corrections for the KEK Accelerator Test Facility final focus beam line, Physical Review Special Topics - Accelerators and Beams 17, 023501 (2014)
[3] E. Marin et al., Design and high order optimization of the Accelerator Test Facility lattices, Physical Review Special Topics - Accelerators and Beams 17, 021002 (2014)
[4] D. Wang et al., Analytical Estimate of ATF Beam Halo Distribution, Chinese Physics C 2014 Vol. 38(12): 127003
[5] Y. Renier et al., Trajectory measurements and correlations in the final focus beam line at the KEK Accelerator Test Facility, Physical Review Special Topics - Accelerators and Beams 16, 062803 (2013)
[6] Bambade P. et al., Present status and first results of the final focus beam line at the KEK Accelerator Test Facility, Phys. Rev. ST Accel. Beams 13, (2010) 042801.

Website : http://lcdev.kek.jp/ATF2/

Summary :
Many developments on Input Power Couplers for superconducting LINAcs have been performed during the last few years at LAL (IN2P3), IRFU (CEA) and KEK. Different prototypes, pre-series and even serial couplers (XFEL case) have been manufactured and are undergoing validation processes. Collaboration between the three already mentioned institutes on Superconducting Power Couplers aims to enhance technical exchanges on design and experience feedbacks as they represent a great potential source of information, both for the current Power Coupler tests and future Couplers developments, especially for the large scale machines.
In the frame of this collaboration we will mainly focus on the issues we consider as very problematic because they are still partially based on qualitative specifications. Therefore, validation criteria and tests have to be carefully specified. Copper plating, cleaning and RF conditioning are the main emphasis of our studies.

French members :
H. Jenhani, S. Berry, G. Devanz, H. Guler, W. Kaabi

Japanese members :
E. Kako, K. Umemori, H. Sakai, Y. Yamamoto

References :
[1] W. Kaabi, “Power couplers for XFEL”, IPAC2013, Shanghai,China, WEPWO001.
[2] H. Jenhani, “Validation procedures for the IFMIF power coupler prototypes”, SRF2013, Paris, France, THP056.
[3] E. Kako, “High power tests of CW input couplers for CERL injector cryomodule”, IPAC2012, New Orleans, Louisiana, USA, WEPPC012.

Summary

French members :
E. Cenni, J. Plouin

Japanese members :
Y. Yamamoto, H. Sakai, K. Umemori

References

Website