IPAC2012 - List of Authors (Tanaka, Y.)

Paper	Title	Page
MOPPP036	Progress in Reducing the Back-bombardment Effect in the ITC-RF gun for t-ACTS Project at Tohoku University	643
	X. Li, H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, T. Muto, K. Nanbu, Y. Tanaka Tohoku University, Research Center for Electron Photon Science, Sendai, Japan F. Miyahara KEK, Ibaraki, Japan
	An ITC (independently tunable cells) thermionic RF gun* has been developed to produce sub-picosecond electron pulses as part of the injector for coherent terahertz radiation at Tohoku University. Both experiments and simulations have shown that the back-bombardment (B.B.) effect on the LaB6 cathode is a serious issue for option. A numerical model has been developed to evaluate the temperature increase of the cathode due to B.B. in which a 2D equation for heat conduction is solved by taking the back-streaming electrons into account. Using this model we have studied the possibility of suppressing the B.B. by employing dipole field and optimization of the cathode radius, compared with experimental data. Other methods and the prospect of the RF gun will also be reported. * H. Hama et al., New J. Phys. 8 (2006) 292

MOPPP074	Magnetic Field Measurement for a THz Undulator Using the Vibrating Wire Method	732
	S. Kashiwagi, H. Hama, F. Hinode, M. Kawai, X. Li, T. Muto, K. Nanbu, Y. Tanaka Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
	Funding: This work is supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (S), Contract #20226003. We constructed the undulator that is a basically a Halbach planer type for a generation of intense coherent terahertz radiation from the very short electron bunch. The period length of the undulator and the number of periods are 100 mm and 25, respectively. Its maximum magnetic field is 0.41 T and the K-value is 3.82 with 54 mm gap. The vibrating wire method is studied to measure the periodic magnetic field of the undulator. By measuring amplitudes and phases of standing waves excited on the wire by the Lorentz force between AC current and magnetic field, we can reconstruct the magnetic field distribution along the wire. The theoretical analysis has been performed for the THz undulator and derived a relation between a reproducibility of undulator field and the number of the harmonic mode to use for the reconstruction. A model experiment was demonstrated using 20cm wire and one pair of permanent magnet block. The theoretical study and the results of model experiment using the vibrating wire method will be shown in this conference.

Paper

Title

Page

Progress in Reducing the Back-bombardment Effect in the ITC-RF gun for t-ACTS Project at Tohoku University

643

X. Li, H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, T. Muto, K. Nanbu, Y. Tanaka
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
F. Miyahara
KEK, Ibaraki, Japan

An ITC (independently tunable cells) thermionic RF gun* has been developed to produce sub-picosecond electron pulses as part of the injector for coherent terahertz radiation at Tohoku University. Both experiments and simulations have shown that the back-bombardment (B.B.) effect on the LaB6 cathode is a serious issue for option. A numerical model has been developed to evaluate the temperature increase of the cathode due to B.B. in which a 2D equation for heat conduction is solved by taking the back-streaming electrons into account. Using this model we have studied the possibility of suppressing the B.B. by employing dipole field and optimization of the cathode radius, compared with experimental data. Other methods and the prospect of the RF gun will also be reported.
* H. Hama et al., New J. Phys. 8 (2006) 292

MOPPP074

Magnetic Field Measurement for a THz Undulator Using the Vibrating Wire Method

732

S. Kashiwagi, H. Hama, F. Hinode, M. Kawai, X. Li, T. Muto, K. Nanbu, Y. Tanaka
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan

Funding: This work is supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (S), Contract #20226003.
We constructed the undulator that is a basically a Halbach planer type for a generation of intense coherent terahertz radiation from the very short electron bunch. The period length of the undulator and the number of periods are 100 mm and 25, respectively. Its maximum magnetic field is 0.41 T and the K-value is 3.82 with 54 mm gap. The vibrating wire method is studied to measure the periodic magnetic field of the undulator. By measuring amplitudes and phases of standing waves excited on the wire by the Lorentz force between AC current and magnetic field, we can reconstruct the magnetic field distribution along the wire. The theoretical analysis has been performed for the THz undulator and derived a relation between a reproducibility of undulator field and the number of the harmonic mode to use for the reconstruction. A model experiment was demonstrated using 20cm wire and one pair of permanent magnet block. The theoretical study and the results of model experiment using the vibrating wire method will be shown in this conference.