| Paper | Title | Page |
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| MOPPP036 | Progress in Reducing the Back-bombardment Effect in the ITC-RF gun for t-ACTS Project at Tohoku University | 643 |
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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 |
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| MOPPR025 | The BPM DAQ System Upgrade for SuperKEKB Injector Linac | 834 |
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| The non-destructive beam position monitor (BPM) is indispensable diagnostic tool for the stable beam operation. In the KEK Linac, approximately nineteen BPMs with the strip-line type electrodes are used for the beam orbit measurement and feedback. In addition, some of them are also used for the beam energy feedback loops. The current DAQ system consists of the fast digital oscilloscopes. A signal from each electrode is analyzed with a predetermined response function up to 50 Hz. The beam position resolution of current system is limited to about 0.5 mm because of ADC resolution. Towards SuperKEKB project, we have a plan to upgrade the BPM DAQ system since the Linac should provide the smaller emittance beam. We will report the system description of the new DAQ system and the results of performance test in detail. | ||
| TUPPR051 | Development of L-Band Positron Capture Accelerating Structure with Kanthal-coated Collinear Load for SuperKEKB | 1933 |
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| In order to achieve a luminosity of 8x1035 cm-2 s-1, the SuperKEKB injector is required to provide both e+e− beams higher in intensity by a factor 4-5 than those for KEKB, and with a low emittance of about 20 um. A damping ring is used to fulfill this low emittance requirement for e+, but the intensity increase is realized by a larger yield from the conversion target to the damping ring. To this end, the L-band capture system is adopted to increase the transverse and longitudinal acceptance. The capture section consists of a Tungsten conversion target with flux concentrator followed by two L-band 2.4m-long accelerating structures and continuing to the large aperture S-band 2m-long ones. The L-band frequency of 1.3 GHz, 5/11 times S-band one, was adopted to suppress the satellite bunches in the S-band system. This L-band system is surrounded by a solenoid magnet producing 4kG on axis. To compose compact magnet system, the output coupler of the L-band accelerating structure is replaced by the Kanthal coated collinear load section. In this paper, we will discuss the design of the accelerating structure and present the studies of Kanthal layer coated on copper. | ||
| TUPPR005 | Linac Upgrade in Intensity and Emittance for SuperKEKB | 1819 |
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| The SuperKEKB is designed to produce 40 times luminosity than that of the KEKB. In order to realize such a high luminosity, the injector linac should provide both electron and positron beams of about 4-5 nC/bunch, which is several times higher than before. In addition, their emittance requirement of the injection beam to the rings is 20 microns, which is a factor of a few tens smaller than before. The intensity and emittance of the electron beam are realized directly by developing the photo RF gun. In contrast, the positron intensity is increased by adopting a higher capture efficiency system with flux concentrator followed by large-aperture accelerators, while its emittance is reduced by a damping ring. For preserving such a low emittance of both beams toward the injection to the rings, the suppression of the emittance growth is crucial. To this end, the alignment of the accelerator components should be a few tens of microns, where we need an improvement by more than a factor 10. The beam-based alignment is definitely needed with better-resolution BPMs. In the present paper are reviewed the overall progress and perspective of the design and the associated component developments. | ||