FEL2011 - List of Authors (Miyahara, F.)

Paper	Title	Page
THPA17	Study of the Back-bombardment Effect in the ITC-Rf Gun for t-ACTS Project at Tohoku University	503
	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
	A specially designed thermionic RF gun which consists of two independently tunable cells [1] (ITC) is used to produce sub-picoseconds electron pulses as the source for coherent terahertz radiation at Tohoku University. Simulations of particle motion show that the back-bombardment effect on the LaB6 cathode surface is serious and should be controlled carefully. Using EGS5 [2] the power deposition of the back-bombardment inside the cathode can be calculated by using the information of back-streaming electrons derived from GPT [3] simulation, and further used to evaluate the temperature increase on the cathode surface by numerically solving a 2-dimentional equation for heat conduction. In the 2D model, the back-streaming electrons are treated as external heat source as well as the cathode heater that heats the cathode from its side along with thermal radiation from its surface. In addition, some methods will be proposed to reduce the back-bombardment effect and we will also compare the simulation results with experimental data. [1] H. Hama et al., New J. Phys. 8 (2006) 292 [2] Electron Gamma Shower, http://rcwww.kek.jp/research/egs/egs5.html [3] General Particle Tracer, http://www.pulsar.nl/gpt

THPA31	Commissioning of ITC-RF Gun for t-ACTS Project at Tohoku University	547
	F. Hinode, H. Hama, S. Kashiwagi, M. Kawai, X. Li, T. Muto, K. Nanbu, Y. Tanaka Tohoku University, Research Center for Electron Photon Science, Sendai, Japan F. Miyahara KEK, Ibaraki, Japan
	Funding: This work is partially supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (S), Contract #20226003. A test accelerator as the coherent terahertz source project (t-ACTS) is in progress at Tohoku University, in which an isochronous ring and a bunched free electron laser will provide the intense terahertz radiation by dint of the sub-picoseconds electron pulses [1, 2]. A thermionic RF gun with two independently-tunable cells (ITC), an alpha magnet and a 3 m accelerating structure are employed in the t-ACTS injector for the short pulse generation. Tracking simulations show that very short electron pulse less than 100 fs with a bunch charge of about 20 pC can be obtained by means of the velocity bunching scheme [2]. Although the usable amount of the extracted beam from the ITC-RF gun is quite small comparing with photo-injectors, there seem to be distinct features such as the better stability and the multi-bunch capability. High power RF processing for the gun has already been accomplished, and then the beam commissioning will be started soon. We will report results of beam commissioning of the ITC-RF gun and also present the current status of t-ACTS project. [1] H. Hama et al., New J. Phys. 8 (2006) 292, [2] H. Hama and M. Yasuda, Proc. of FEL2009, TUPC69, (2009) 394 [3] F. Miyahara et al., Proc. of IPAC'10, THPD094, (2010) 4509

Paper

Title

Page

Study of the Back-bombardment Effect in the ITC-Rf Gun for t-ACTS Project at Tohoku University

503

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

A specially designed thermionic RF gun which consists of two independently tunable cells [1] (ITC) is used to produce sub-picoseconds electron pulses as the source for coherent terahertz radiation at Tohoku University. Simulations of particle motion show that the back-bombardment effect on the LaB6 cathode surface is serious and should be controlled carefully. Using EGS5 [2] the power deposition of the back-bombardment inside the cathode can be calculated by using the information of back-streaming electrons derived from GPT [3] simulation, and further used to evaluate the temperature increase on the cathode surface by numerically solving a 2-dimentional equation for heat conduction. In the 2D model, the back-streaming electrons are treated as external heat source as well as the cathode heater that heats the cathode from its side along with thermal radiation from its surface. In addition, some methods will be proposed to reduce the back-bombardment effect and we will also compare the simulation results with experimental data.
[1] H. Hama et al., New J. Phys. 8 (2006) 292
[2] Electron Gamma Shower, http://rcwww.kek.jp/research/egs/egs5.html
[3] General Particle Tracer, http://www.pulsar.nl/gpt

THPA31

Commissioning of ITC-RF Gun for t-ACTS Project at Tohoku University

547

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

Funding: This work is partially supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (S), Contract #20226003.
A test accelerator as the coherent terahertz source project (t-ACTS) is in progress at Tohoku University, in which an isochronous ring and a bunched free electron laser will provide the intense terahertz radiation by dint of the sub-picoseconds electron pulses [1, 2]. A thermionic RF gun with two independently-tunable cells (ITC), an alpha magnet and a 3 m accelerating structure are employed in the t-ACTS injector for the short pulse generation. Tracking simulations show that very short electron pulse less than 100 fs with a bunch charge of about 20 pC can be obtained by means of the velocity bunching scheme [2]. Although the usable amount of the extracted beam from the ITC-RF gun is quite small comparing with photo-injectors, there seem to be distinct features such as the better stability and the multi-bunch capability. High power RF processing for the gun has already been accomplished, and then the beam commissioning will be started soon. We will report results of beam commissioning of the ITC-RF gun and also present the current status of t-ACTS project.
[1] H. Hama et al., New J. Phys. 8 (2006) 292,
[2] H. Hama and M. Yasuda, Proc. of FEL2009, TUPC69, (2009) 394
[3] F. Miyahara et al., Proc. of IPAC'10, THPD094, (2010) 4509