A high brightness photoelectron injector must be developed as a part of the BERLinPro ERL program [1, 2]. The injector is designed to produce an electron beam with 100 mA average current and a normalized emittance of 1 mm mrad. Prior to reaching the final gun/cathode design a staged SRF gun development program has been undertaken which began with the operation of a fully superconducting injector utilizing a lead photocathode. This will be followed by a normal conducting CsK2Sb cathode capable of generating high current beams. In the first stage we have measured the fundamental beam parameters bunch charge, beam energy and energy spread with a special focus on the measurement of the transverse beam profiles. We will also discuss our plans for the beam characterization at high currents.

Optical lithography has been actively used over the past decades to produce more and more dense integrated circuits. To keep with the pace of the miniaturization, light of shorter and shorter wavelength was used with time. The capabilities of the present 193-nm UV photolithography were expanded time after time, but it is now believed that further progress will require deployment of extreme ultraviolet (EUV) lithography based on the use of 13.5-nm radiation. However, presently no light source exists with sufficient average power to enable high-volume manufacturing. We report here the results of a study that shows the feasibility of a free-electron laser EUV source driven by a multiturn superconducting energy-recovery linac (ERL). The proposed 40 x 20 m(2) facility, using MW-scale consumption from the power grid, is estimated to provide about 5 kW of average EUV power. We elaborate the self-amplified spontaneous emission (SASE) option, which is presently technically feasible. A regenerative-amplifier option is also discussed. The proposed design is based on a short-period (2-3 cm) undulator. The corresponding electron beam energy is about 0.5-1.0 GeV. The proposed accelerator consists of a photoinjector, a booster, and a multiturn ERL.

One of the main problems of contemporary high power FELs is the mirror heating. One of the possible solutions of this problem is the use of electron outcoupling [N.G. Gavrilov, et al., Nucl. Instr. and Meth. A 304 (1991) 63; G.N. Kulipanov, A.S. Sokolov, N.A. Vinokurov, Nucl. Instr. and Meth. A 375 (1996) 576]. In this case the mirrors of optical resonator are not transparent and the coherent radiation from an additional undulator in the FEL magnetic system is used. To provide the output of this radiation the electron beam in the auxiliary undulator is deflected from the optical resonator axis. To save bunching it is preferable to use the achromatic deflecting bend. The project of electron outcoupling for the Novosibirsk FEL is described. Simulation results are presented.

High power THz applications on the Novosibirsk terahertz free electron laser are described.

Different mode regimes versus the extent modulation instability stabilization were investigated with a complex diagnostics system. Slippage due to frequency detuning of electron and light pulses turned out to be the main stabilization factor. Spectral and time parameters of the laser, especially the radiation of high harmonics, have been shown to strongly depend on the stabilization.

Ring FELs [N.A. Vinokurov, O.A. Shevchenko, Nucl. Instr. And Meth. A 528 (2004) 491] were proposed mainly to improve the quality of radiation of X-ray FELs. Their main advantage is the absence of mirrors. It appears that this advantage is also useful for high-power FELs. Another reason to build infrared ring FEL is the proof of principle for shorter wavelength FELs. Therefore, we considered the scheme of infrared ring FEL which requires ERL with beam energy 50MeV. Using extensive simulations we developed requirements for electron beam parameters and magnetic system of ring FEL. In spite of rather compact design such FEL may provide more than 10kW average power.

The first stage of Novosibirsk high power free electron laser (FEL) is in operation since 2003. One orbit for 11MeV energy with terahertz FEL lies in vertical plane. Other four orbits lie in the horizontal plane. The beam is directed to these orbits by switching on of two round magnets. In this case electrons pass four times through accelerating RF cavities, obtaining 40-MeV energy. Then, (at fourth orbit) the beam is used in FEL, and then is decelerated four times. At the second orbit (20 MeV) we have bypass with third FEL. When magnets of bypass are switched on, the beam passes through this FEL. The length of bypass is chosen to provide the delay, which necessary to have deceleration instead of acceleration at the third passage through accelerating cavities. Now two of four horizontal orbits are assembled and commissioned. The electron beam was accelerated twice and then decelerated down to low injection energy. Project average current 9 mA was achieved. First multiorbit ERL operation was demonstrated successfully. INTRODUCTION A source of terahertz radiation was commissioned in Novosibirskin 2003 [1]. It is CW FEL based on an accelerator–recuperator, or an energy recovery linac (ERL). It differs from other ERL-based FELs [2, 3] in the low frequency non-superconducting RF cavities and longer wavelength operation range. Full-scale Novosibirsk free electron laser facility is to be based on the four-orbit 40 MeV electron accelerator-recuperator (see Fig. 1). It is to generate radiation in the range from 5 micrometer to 0.24 mm [4, 5]. Figure 1: Scheme of the accelerator-recuperator based FEL. 1 injector, 2 accelerating RF structure, 3 180degree bends, 4 – undulator, 5 – beam dump, 6 – mirrors of the optical resonator. THE FIRST STAGE OF NOVOSIBIRSK ERL The first stage of the Novosibirsk free electron laser (Fig. 2.), based on the energy-recovery linac, generates coherent radiation tunable in the range 120-240 micron as a continuous train of 40-100 ps pulses at the repetition rate of 2.8-22.5 MHz. Maximum average output power is 500 W, the peak power is more than 1 MW [6,7]. The minimum measured linewidth is 0.3%, which is close to the Fourier-transform limit. Four user stations are in operation now. Two other are in progress.

Novosibirsk energy recovery linac (ERL) facility is planned to use the same RF system and electron gun to run three different FELs. First FEL, installed on the ERL orbit, which lies in the vertical plane, is in operation since 2003. It provides average power up to 500 W in the wavelength range 110 – 240 micron and since 2004 works for users. Four orbits in the horizontal plane were added this year. It is planned to have two additional FELs at the second (20 MeV) and fourth (40 MeV) tracks of ERL. The operation mode with one of three FELs may be chosen by switching of some magnets. Recently the twoorbit mode of ERL (for the second FEL operation) was commissioned successfully. The beam passed four times through the accelerating RF cavities and was absorbed in the beam dump. Thus, the first in the world two-orbit ERL is in operation now. Some details of design, status of the facility and plans are discussed. INTRODUCTION A source of terahertz radiation was commissioned in Novosibirskin 2003 [1]. It is CW FEL based on an accelerator–recuperator, or an energy recovery linac (ERL). It differs from other ERL-based FELs [2, 3] in the low frequency non-superconducting RF cavities and longer wavelength operation range. Full-scale Novosibirsk free electron laser facility is to be based on the four-orbit 40 MeV electron accelerator-recuperator (see Fig. 1). It is to generate radiation in the range from 5 micrometer to 0.24 mm [4, 5]. Figure 1: Scheme of the accelerator-recuperator based FEL. 1 injector, 2 accelerating RF structure, 3 180degree bends, 4 – undulator, 5 – beam dump, 6 – mirrors of the optical resonator. THE FIRST STAGE OF NOVOSIBIRSK ERL The first stage of the Novosibirsk free electron laser (Fig. 2.), based on the energy-recovery linac, generates coherent radiation tunable in the range 110-240 micron as a continuous train of 40-100 ps pulses at the repetition rate of 2.8-22.5 MHz. Maximum average output power is 500 W, the peak power is more than 1 MW [6,7].