Compact Electron Storage Ring Research Articles

A compact electron storage ring for lithographical applications

A compact electron storage ring for lithographical applications

“Spiral COSAMI” — A Multi-Undulator Compact Source for Actinic Mask Inspection in the extreme ultraviolet range

A compact electron storage ring provides a bright, stable and reliable source of extreme ultraviolet (EUV) radiation for metrology applications in semiconductor industry. The COSAMI concept (COmpact Synchrotron for Actinic Mass Inspection) applied design principles and technology of modern diffraction limited light source storage rings to an EUV facility operating at 13.5 nm wavelength. Since floor space is an important issue in an industrial environment, we propose a lattice configuration where three (or more) recirculation turns are stacked vertically. We present a facility, called Spiral-COSAMI, which simultaneously serves multiple (three or more) EUV beamlines within about the same floor space of the original COSAMI, and using the same type of injector and the same set of diagnostics, radio-frequency and pulsed magnet devices. The increased period of revolution of the multiple turns mitigates the problem of ion trapping and relaxes specifications of injection kickers.

Transverse resonance island buckets for synchrotron-radiation based electron time-of-flight spectroscopy.

At the Metrology Light Source (MLS), the compact electron storage ring of the Physikalisch-Technische Bundesanstalt (PTB) with a circumference of 48 m, a specific operation mode with two stable closed orbits for stored electrons was realized by transverse resonance island buckets. One of these orbits is closing only after three turns. In combination with single-bunch operation, the new mode was applied for electron time-of-flight spectroscopy with an interval of the synchrotron radiation pulses which is three times the revolution period at the MLS of 160 ns. The achievement is of significant importance for PTB's future programs of angular-resolved electron spectroscopy with synchrotron radiation and similar projects at other compact electron storage rings. The scheme applied here for selecting the photons originating from a particular orbit by optical imaging has been used before in fs slicing applications and may be relevant for the BESSY VSR project of the Helmholtz-Zentrum Berlin.

Design of a 4.8-m ring for inverse Compton scattering x-ray source

In this paper we present the design of a 50 MeV compact electron storage ring with 4.8-meter circumference for the Tsinghua Thomson scattering x-ray source. The ring consists of four dipole magnets with properly adjusted bending radii and edge angles for both horizontal and vertical focusing, and a pair of quadrupole magnets used to adjust the horizontal damping partition number. We find that the dynamic aperture of compact storage rings depends essentially on the intrinsic nonlinearity of the dipole magnets with small bending radius. Hamiltonian dynamics is found to agree well with results from numerical particle tracking. We develop a self-consistent method to estimate the equilibrium beam parameters in the presence of the intrabeam scattering, synchrotron radiation damping, quantum excitation, and residual gas scattering. We also optimize the rf parameters for achieving a maximum x-ray flux.

Monochromatic computed tomography with a compact laser-driven X-ray source

A laser-driven electron-storage ring can produce nearly monochromatic, tunable X-rays in the keV energy regime by inverse Compton scattering. The small footprint, relative low cost and excellent beam quality provide the prospect for valuable preclinical use in radiography and tomography. The monochromaticity of the beam prevents beam hardening effects that are a serious problem in quantitative determination of absorption coefficients. These values are important e.g. for osteoporosis risk assessment. Here, we report quantitative computed tomography (CT) measurements using a laser-driven compact electron-storage ring X-ray source. The experimental results obtained for quantitative CT measurements on mass absorption coefficients in a phantom sample are compared to results from a rotating anode X-ray tube generator at various peak voltages. The findings confirm that a laser-driven electron-storage ring X-ray source can indeed yield much higher CT image quality, particularly if quantitative aspects of computed tomographic imaging are considered.

Development of advanced radiation sources at KAERI

The KAERI Center for Quantum Beam-Based Radiation Research, was founded in 2011. The center pursues the development of advanced radiation sources and their applications in biology, material science, and nuclear physics. There are two main research topics in the development of advanced radiation sources: a system with high-power T-ray pump and an ultrashort X-ray probe system and a compact electron storage ring based on a laser-accelerated electron beam.

Study of electron transport in a compact storage ring after interaction with target materials

A compact electron storage ring has been studied with tools for 3D electromagnetic field simulation. To produce an intense hard X-ray beam, the electrons interact with a target inside the system. If the impact on the electron trajectory after interaction is small, it is possible to reuse the electron several times as in a conventional synchrotron storage ring. We tracked the electrons in the 3D electromagnetic fields of the storage ring. From our numerical experiments we can determine the maximum thickness of the target materials.

Tsinghua Thomson scattering X-ray source

We proposed the Tsinghua Thomson scattering X-ray (TTX) source as an ultra-fast, high flux source for advanced X-ray imaging studies and applications. A linac system, which consists of an S-band photocathode RF gun, a SLAC type 3 m traveling wave tube and two X-band structures, generates ultra-short, high brightness electron pulses to scatter with tera-watt femto-second laser pulses. A compact low energy electron storage ring is also designed to dramatically enhance the average X-ray flux. In this paper, we present the simulation studies and optimized parameters of the electron and X-ray pulses. The construction and commissioning status of TTX is also reported.

Suppressing the X-Y coupling effect in compact electron storage rings.

The x-y coupling effect, especially the tilt of the beam profiles, in the Super-ALIS compact electron storage ring has been effectively eliminated. The main feature of this method is the suppression of the most harmful Fourier components of the skew-quadrupole perturbation by using just one thin skew-quadrupole magnet. Therefore, the method should be simple and effective for coupling suppression in compact storage rings that have little space for correction instruments.

High-performance beamline for vacuum-ultraviolet-excited material processing

A high-performance beamline dedicated to vacuum-ultraviolet (VUV)-excited semiconductor processing has been constructed on the compact electron storage ring “Super ALIS”. The first toroidal mirror accepts photons (emitted at a bending magnet) for 70 mrad in the horizontal direction, and the reflected parallel beam is focused onto the specimen surface by the second toroidal mirror. A brilliant VUV beam (with a photon density of 1.3×1016 s−1 mm−2 when the ring current is 300 mA) illuminates a circular field (10 mm in diameter) on the target surface. The eight 5-m-long differential pumping stages allow the reactant gas to be introduced into the reaction chamber at pressures up to 0.1 Torr. The processing is monitored in real time by using ultraviolet phase-modulated spectroscopic ellipsometry, and VUV-stimulated evaporation of SiO2 film has been demonstrated.

Landau damping effect due to the trapped ions in a compact electron storage ring

Abstract Theoretical analysis and experimental results show that the Landau damping due to trapped ions is greatly enhanced in the low-energy beams in compact electron storage rings. This enhancement originates mainly from the decrease in beam size in the low-energy region. This effect must indeed be the main reason why the recently developed compact rings can store a large current even though they have a low injection energy. In the typical energy region of compact rings, more positive utilization of this effect could make the damping rate of a lower-energy beam far larger than that of a higher-energy one. Therefore, if we could control the effect of the trapped ions, we might prefer to adopt lower energy in order to inject a large current in a compact ring.

Field measurements of superconducting bending magnets for compact storage ring

We have constructed 180 degree superconducting bending magnets for compact electron storage rings and tests of magnetic field qualities of the magnets have been performed. Measured field qualities are; (1) high field homogeneity (normalized field errors are less than 1/spl times/10/sup -3/ over the electron beam aperture), (2) high field stability (the decay of the field is less than 0.1%/year) at persistent current mode of 3.5 T, (3) small gradient of coil axis (the averaged value is 0.5 mrad), and (4) small difference of the fields between two magnets (the difference is less than /spl plusmn/1/spl times/10/sup -3/). From the tests of field qualities, we confirm that the magnets have good performance for electron beam storage. An electron beam of 600 MeV can be stored.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Undulator radiation source NIJI-II for photo-excited processes

An undulator radiation source using a compact electron storage ring was developed for photo-excited processes. Quasi-monochromatic radiation has been available and the wavelength of the radiation is tunable from 65 to 1000 nm. The full width at half maxima (FWHM) was measured by a Seya-Namioka type monochromator and the photon fluence was measured using an ionization chamber. We present here an intense vacuum ultraviolet light source which emits a photon fluence exceeding 10 15 photons/s.

Development of a compact high brightness X-ray source

Based on the concept of interacting electron with intense light stored in a supercavity, a compact and high brightness soft X-ray source has been proposed for lithography at ILT/ILE. For the purpose of enhancing the collision frequency of electron-photon beams, the idea of a combination of a supercavity pumped by a cw diode laser with an electrostatic dc accelerator has been put forward, for which a high average spectral brightness of 1.79×10 17 with a wavelength of 9.8 Å, and a bandwidth of 0.17% can be expected. Two other upgraded systems for the production of high peak brightness X-ray radiation and high brightness γ-ray radiation have also been proposed, which are based on an ultrahigh power laser (2 TW, 5 ps) and a compact electron storage ring (300 MeV/89.3 mA). Meanwhile, the prototype laser undulator system and the current experiments on photon storage in a Fabry-Perot cavity pumped by a high power mode-locked Nd:YAG laser (25 MW, 89.25 MHz) are introduced.

Synchrotron radiation sources and condensers for projection x-ray lithography

The design requirements for a compact electron storage ring that could be used as a soft-x-ray source for projection lithography are discussed. The design concepts of the x-ray optics that are required for collecting and conditioning the radiation in divergence, uniformity, and direction to illuminate the mask correctly and the particular x-ray projection camera used are discussed. Preliminary designs for an entire soft-x-ray projection lithography system that uses an electron storage ring as a soft-x-ray source are presented. It is shown that, by combining the existing technology of storage rings with large collection angle condensers, a powerful and reliable source of 130-A photons for production line projection x-ray lithography is possible.

電子蓄積リング“ＮＩＪＩ ＩＶ”による自由電子レーザー発振技術の研究

We have constructed a racetrack-type compact electron storage ring “NIJI-IV” for UV FEL. The ring has a hexagonal configuration with two 7.25 m-long straight sections, though its circumference is 29.6 m. A 6.3 m optical klystron (OK) for high FEL gain was installed in one of the long straight sections. The experimental setup for FEL lasing was started at the end of April 1992. The setup on the ring with the OK and the cavity mirror alignment have been completed. The FEL lasings using the NIJI-IV were accomplished at 595589 nm on August 18, 1992 and at 488 nm on September 18, 1992. The final development target is stable FEL lasing in the UV range

Synchrotron radiation X-ray lithography for the fabrication of sub-quartermicron large-scale-integrated circuits.

Recent developments in a wide range of technologies, involving compact electron storage rings, exposure systems, masks, and resist materials, have moved synchrotron radiation x-ray lithography much closer to a viable method for manufacturing sub-quartermicron large-scale integrated circuits. This paper demonstrates NTT's recent progress in synchrotron radiation lithography and presents the successful results of sub-quartermicron Bi-CMOS device fabrication. An overview of the lithography system and resist process is presented with emphasis on patterning and overlay performance.

A New Method for Measuring the Neutralization Factor in a Compact Electron Storage Ring

Response of trapped ions when a clearing voltage was turned off was observed with a charge coupled device (CCD), detecting the time variation of the synchrotron radiation (SR) intensity from the central density of electrons in the stored beam. This enabled us to estimate the neutralization factor and compare it to that obtained from measurements of the betatron tune shift. It is expected that this new method will contribute to the study of ion trapping.

Photodesorption from copper, beryllium, and thin films

Ever increasing circulating currents in electron-positron colliders and light sources demand lower and lower photodesportion (PSD) from the surfaces of their vacuum chambers and their photon absorbers. This is particularly important in compact electron storage rings and B meson factories where photon power of several kW cm−1 is deposited on the surfaces. Given the above factors we have measured PSD from 1 m long bars of (a) solid copper and solid beryllium, and (b), TiN, Au, and C thin films deposited on solid copper bars. Each sample was exposed to about 1023 photons/m with a critical energy of 500 eV at the vacuum ultraviolet ring of the National Synchrotron Light Source. PSD was recorded for two conditions: after a 200 °C bakeout and after an Ar glow discharge cleaning. In addition, we also measured reflected photons, photoelectrons, and desorption as functions of normal, 75, 100, and 125 mrad incident photons.

Present status of a 500 MeV compact electron storage ring for UV FEL experiments

Abstract We have constructed a racetrack-type compact electron storage ring “NIJI-IV” for UV FEL experiments. The ring has a hexagonal configuration with a circumference 29.6 m. consisting of the two-cell structure of the triple-bend achromat lattice. The length of the straight section is 7.25 m in which a 6.3 m insertion device can be installed. A stored current higher than 200 mA is expected. The first storage of electrons was achieved on February 15, 1991, with an injection energy of 270 MeV. At present, a stored current higher than 70 mA with a lifetime of 20 to 30 min is obtained at full bunch operation (the harmonic number is sixteen).