J. Kishiro

First result of the KEK X-band free electron laser in the ion channel guiding regime

Abstract Recent experimental results are reported for an induction-driven X-band FEL, with ion channel guiding inside the wiggler. Power in excess of 10 MW at 9.4 GHz, has been observed with a beam energy of 750 keV and a current of 520 A. Maximum gain is 22 dB/m, with no saturation after 15 wiggler periods. A self-amplified spontaneous power of 4 kW was also measured. Data for the detuning curve, field evolution and current transmission are presented and discussed.

Superbunch Hadron Colliders

A novel concept of a high luminosity hadron collider is proposed. This would be a typical application of an induction synchrotron being newly developed. Extremely long bunches, referred to as superbunches, are generated by a multibunch stacking method employing barrier buckets at the injection into the collider and are accelerated with a step voltage induced in the induction gaps. Superbunches intersect with each other, yielding a luminosity of more than 10(35) cm(-2) sec(-1). A combination of vertical crossing and horizontal crossing must be employed in order to avoid any significant beam-beam tune shift.

X-band prebunched FEL amplifier

Abstract We have designed and constructed a prebunched FEL amplifier consisting of a prebuncher and a standard FEL. Microwave power saturation with a short wiggler length has been realized by a prebunched beam. We have also examined microwave phase evolutions. It has been demonstrated the adjustable range of the output microwave phase by changing the input microwave phase is restricted within a narrow band due to spontaneous emission radiated by the prebunched beam.

Experimental results on the 1.5 MeV ion-channel guided X-band free-electron laser

Abstract Experiments on the ion-channel guided X-band free-electron laser amplifier (IXFEL) generated peak microwave power exceeding 100 MW at 9.4 GHz with a gain of 21 dB/m. Saturation in the evolution curve has been achieved and a frequency spread of 0.9% was observed. The amplified microwaves were separated from the driving beam line and extracted without breakdown.

Experimental studies of microwave amplification in the ion-focused regime

Studies of microwave amplification with an in-focused electron beam drawn from an induction injector are reported. A free-electron laser (FEL) operating at 9.4 GHz and employing ion-focusing within the interaction region has achieved power in excess of 30 MW at 9.4 GHz, with a beam energy of 0.8 MeV and current of 0.7 kA. Peak gain is 20 dB/m, with no saturation after 15 wiggler periods. Also reported are the first evolution and detuning data for an ion-channel laser/maser (ICL). Two shortcomings of the prematurely halted ICL studies are poor frequency discrimination and a large axial plasma gradient. Prospects for operation with an upgraded 1.6 MeV accelerator are discussed. >

Sensitivity calculation of beam position monitor using boundary element method

Abstract The position sensitivity for two types of beam position monitors has been calculated using the boundary element method (BEM). A cylindrical beam position monitor was first chosen to compare between BEM and analytical calculations. The results of the BEM fall within 1% of the analytical calculations. Next we applied the BEM to aracetrack type position monitor and compared the BEM results with measured values.

Proposal for an X-band single-stage FEL

Abstract A single-stage X-band FEL with a high repetition rate (∼ kHz) has been designed and is now under construction at the KEK FEL facility. The microwave FEL will be driven with a 1 MeV, 1 kA electron beam which is generated in the induction gun energized by magnetic switches. A 9.4 GHz microwave signal introduced from the 50 kW magnetron is expected to be amplified to ∼ 300 MW as a result of the interaction with the electron beam in the undulating tapered planar wiggler field. Details of the design including the induction gun, a post-accelerator, a wiggler magnet and an rf measuring system are described. The status and the preliminary operation of the pulsed power system is presented.

1.5 MeV ion‐channel guided x‐band free‐electron laser amplifier

Experiments on the ion‐channel guided x‐band free‐electron laser amplifier generated peak microwave power exceeding 100 MW at 9.4 GHz with a gain of 21 dB/m. Saturation in the evolution curve has been achieved and a frequency spread of 0.9% was observed. The amplified microwave was separated from the driving beam line and extracted without breakdown.

X-band ion-focused free-electron laser

Abstract To assess the feasibility of a free-electron laser two-beam accelerator (TBA/FEL), an induction driven FEL test stand in the X-band microwave regime has been constructed and the energy of the driving beam is being increased year by year. The FEL operating at 9.4 GHz and employing ion focusing even in the interaction region has achieved a power in excess of 30 MW and a gain of 20 dB/m for a 0.6 kA, 0.8 MeV beam. We have found that FEL performance is strongly limited by longitudinal space charge. To mitigate space charge effects, the injector of the test stand has been upgraded to 1.6 MeV and the FEL is under test operation. The outline of the test stand is described and its preliminary experimental results and expected performance are discussed.

Induction System for a Proton Bunch Acceleration in Synchrotron

Recently the first induction acceleration of a single proton bunch of 2.3E10ppp was demonstrated [1], where it was accelerated from 500MeV to 8GeV in 1.9sec in KEK-PS. This paper describes the induction system for a synchrotron and a beam confinement experiment as a second step of the proof-of principle (PoP) experiments of a “induction synchrotron” [2], where a proton beam with a bunch length of 500ns was longitudinally confined by the induction barriers for 500msec, is introduced..