[en] BXERL is a proposal for a test facility (Beijing X-ray Energy Recovery Linac), which requires its injector to provide an electron beam of 5 MeV, 77 pC/bunch at a repetition rate of 130 MHz (average current of 10 mA). In this paper, we present the design of the injector, which consists of a 500 kV photocathode DC gun equipped with a GaAs cathode preparation device, a 1.3 GHz normal conducting RF buncher, two solenoids,and one cryo module containing two 1.3 GHz 2-cell superconducting RF cavities as the energy booster. The detailed beam dynamics show that the injector can generate electron bunches with a RMS normalized emittance of 1.49 πmm·mrad, a bunch length of 0.67 mm, a beam energy of 5 MeV and an energy spread of 0.72%. (authors)

[en] The emittance compensation technology will be used on the photo-cathode RF gun for Shanghai SDUV-FEL. The space charge force and its effect on electron beam transverse emittance in RF gun is studied, the principle of emittance compensation in phase-space is discussed. The authors have designed a compensation solenoid and calculated its magnetic field distribution. Its performance has been studied by the code PARMELA. A simulation result indicates that the normalized transverse RMS emittance for electron beam of 1.5 nC is 1.612 π mm·mrad, electron energy E = 5.71 MeV

[en] In photo-cathode RF gun, the Schottky effect in process of photoemission and electron longitudinal accelerating process bring forth a linear work range in which electron charge out of gun is linear proportion to laser injection phase. According to the result, the authors develop a method that can be used to measure time jitter between laser pulse and RF wave. The method can attain to high precision and small error. On general photo-injector condition, the precision is almost 1.15 fs, the error is almost 0.23 fs

[en] The graphite and carbon fibre composites used as plasma facing components in fusion devices are composed of graphitic crystallites, connected by intercrystalline voids. The porous structure gives rise to great complexity to understand the hydrogen transport behaviour in graphite. In this work dynamic Monte Carlo simulations are carried out to understand the dependence of the hydrogen retention, re-emission, and thermal desorption on the void fraction of graphite. The results show that the void fraction plays an important role in hydrogen retention and release behaviour. (author)

[en] In a photo-cathode radio-frequency (rf) gun, the micro-bunched charge output from the gun is dependent linearly on the laser injection phase, due to the Scottay effect in the process of photoemission and the procedure of the electron longitudinal acceleration. Based on this principle, a new method is proposed, which should be utilized to measure the time jitter between the driving laser pulse and the rf phase with a very high resolution of a few tens of femto-seconds

[en] The authors have synchronized a 102 MHz ultrafast self-mode-locked Ti: sapphire laser to a 2856 MHz RF source with the sample-locking technology. The relative root-mean-square time-jitter is 0.57 ps and the maximum time jitter is 2.60 ps. This is the first time to accomplish the synchronization between the ultrafast laser pulse and the S-band microwave in China. Potential applications include synchronization of lasers and RF power sources in particle accelerator experiments and high-resolution pump-probe experiments. (author)

[en] We report on the measurement of the laser–rf phase jitter in a photocathode rf gun with femtosecond precision. In this experiment four laser pulses with equal separation are used to produce electron bunch trains; then the laser–rf phase jitter is obtained by measuring the variations of the electron bunch spacing with an rf deflector. Furthermore, we show that when the gun and the deflector are powered by the same rf source, it is possible to obtain the laser–rf phase jitter in the gun through measurement of the beam–rf phase jitter in the deflector. Based on these measurements, we propose an effective time-stamping method that may be applied in MeV ultrafast electron diffraction facilities to enhance the temporal resolution.

[en] The authors synchronized a 102-MHz ultrafast self-mode-locked Ti:sapphire laser to a 2856-MHz rf source with the sample-locking technology. The relative root-mean-square time-jitter is 0.57 ps and the maximum time jitter is 2.60 ps. This is the first time that synchronization between the ultrafast laser pulse and the s-band microwave has been accomplished in China. Potential applications include synchronization of lasers and rf power sources in particle accelerator experiments and high-resolution pump-probe experiments

[en] A simple laser technology is proposed to generate a laser pulse sequence with a pulse rate of 2 THz frequency. The laser pulse sequence is used as the driving laser for a photocathode radio frequency (RF) gun. The RF gun generates the pre-bunched electron beams into an undulator for immediate superradiation. Terahertz (THz) radiation, based on a free electron laser (FEL) at a megawatt (MW) level, could be achieved from a compact FEL facility. We describe the laser handling technology for a 16-pulse laser. The detailed calculation of the bunching factor due to the injection phase, beam charge, and bunch number, as well as the differences in the time spacing and energy spread among the laser pulses, are also presented.

[en] The Laser Undulator Compact X-ray source (LUCX) is a test bench for a compact high brightness X-ray generator, based on inverse Compton Scattering at KEK, which requires high intensity multi-bunch trains with low transverse emittance. A photocathode RF gun with emittance compensation solenoid is used as an electron source. Much endeavor has been made to increase the beam intensity in the multi-bunch trains. The cavity of the RF gun is tuned into an unbalanced field in order to reduce space charge effects, so that the field gradient on the cathode surface is relatively higher when the forward RF power into gun cavity is not high enough. A laser profile shaper is employed to convert the driving laser profile from Gaussian into uniform. In this research we seek to find the optimized operational conditions for the decrease of the transverse emittance. With the uniform driving laser and the unbalanced RF gun, the RMS transverse emittance of a 1 nC bunch has been improved effectively from 5.46 πmm.mrad to 3.66 πmm·mrad. (authors)