Hefei Synchrotron Research Articles

Self-reaction of C2H5O2 and its cross-reaction with HO2 studied with vacuum ultraviolet photoionization mass spectrometry

We present a study of the self-reaction of C2H5O2 and its cross-reaction with HO2 with VUV photoionization mass spectrometry. Hefei synchrotron radiation and a krypton discharge lamp are combined to ionize species. Key products including CH3CHO, C2H5OH, C2H5O and C2H5OOH formed from the reactions are directly observed and confirmed. In particular, the radical product C2H5O from the self-reaction is detected for the first time. The ionization energies of C2H5O and C2H5OOH are determined and the Franck-Condon factors are calculated to fit the photoionization spectra. Moreover, kinetic experiments are performed to confirm the products’ assignment and provide detailed reaction mechanism.

Laboratory-based reflectometer using line spectra of an RF-induced gas-discharge lamp in 30- to 200-nm wavelength range

A laboratory-based reflectometer designed for characterizing the reflectivity of optical coatings in 30- to 200-nm wavelength range was recently developed at IPOE. An RF-produced gas-discharge light source is applied to generate characteristic lines. The light source is mounted on a grazing incident monochromator with a 146-deg deviation angle between the incident and diffracted arms. By precisely adjusting the toroidal grating inside the monochromator chamber, monochromatic lights are acquired through the exit slit. A collimator mirror and two sets of collimation slits with 2 mm × 2 mm dimension are utilized for reducing the divergence of the beam incident on the sample. A high-precision six-axis translation stage, which allows a heavy sample with a maximum diameter of 100 mm, is used to control positions of the samples and the detector. A chopper disk used both for incident light intensity monitor and signal modulation is placed with an incidence angle of 70 deg relative to the incident light beam. The configuration, adjustment process, and test results of the reflectometer are presented in detail. The experimental reflectivity results for Al / LiF / MgF2 film obtained from our laboratory and BESSY-II Synchrotron as well as Hefei Synchrotron Light Source are given and compared for demonstrating the reliability of the system.

Vacuum Ultraviolet Negative Photoion Spectroscopy of Chloroform

Negative ions Cl(-), Cl(2)(-), CCl(-), CHCl(-), and CCl(2)(-) are observed in vacuum-ultraviolet ion-pair photodissociations of chloroform (CCl(3)H) using the Hefei synchrotron radiation facility, and their ion production efficiency curves are recorded in the photon energy range of 10.00-21.50 eV. Two similar spectra of the isotope anions (35)Cl(-) and (37)Cl(-) indicate the following: Besides the strong bands corresponding to the electron transitions from valence to Rydberg orbitals converging to the ionic states, some additional peaks can be assigned with the energetically accessible multibody fragmentations; a distinct peak at photon energy 14.55 eV may be due to a cascade process (namely, the Cl(2) neutral fragment at the highly excited state D'2(3)Π(g) may be produced in the photodissociation of CCl(3)H, and then the Cl(-) anions are produced in the pulsed-field induced ion-pair dissociations of Cl(2) (D'2(3)Π(g))); two vibrational excitation progressions, nν(2)(+) and nν(2)(+) + ν(3)(+), and nν(4)(+) and nν(4)(+) + ν(2)(+), are observed around C̃ (2)E and D̃ (2)E ionic states, respectively. The enthalpies of the multibody fragmentations to Cl(2)(-), CCl(-), CHCl(-), and CCl(2)(-) are calculated with the thermochemistry data available in the literature, and these multibody ion-pair dissociation pathways are tentatively assigned in the respective anion production spectra.

Anion Mass Spectrometry Study of Ion-Pair Photodissociation of CO2 in the XUV Energy 19.70–22.24 eV

We demonstrate anion mass spectrometry using the Hefei synchrotron radiation source to investigate the ion-pair dissociation processes of molecules. The efficiency curve of the O− anionic product via ion-pair dissociations of CO2 is recorded with tunable extreme vacuum ultraviolet photons (energy: 19.70–22.24 eV) and compared with the spectrum available in the literature. The possible dynamics of CO2 + hv → CO+ + O− in this energy range is discussed.

A proposed injection system for HLS

Hefei synchrotron radiation Light Source (HLS) presently has three kickers for electron injection. It is a lattice-dependent system, and different lattices will form different shapes of bump orbits. In the upgrading of HLS, a compact, lattice-independent injection system will be adopted. This paper looks into the possibilities of using quadrupole-magnet trim coils to produce assistant DC injection bumps and then to decrease the required amplitude of kicker bump. Some calculation results of injection schemes are discussed.

Current status of HESYRL lithography beam line

A lithography beam line, as the first of possibly six or more, has been installed in the Hefei Synchrotron Radiation Laboratory (HESYRL). A scanning mirror is used to cut off shorter wavelengths and to expand exposure dimensions vertically. The scanning mirror is oscillated by a stepping motor while an in-situ Moirè fringe grating system measures motor speed uniformity. Some testing results are given. In the first part of the beam line, there is a beryllium window to block longer wavelength light, a laser alignment unit to align the beam line and a special exposure shutter, which is controlled by another stepping motor. An exposure chamber with vacuum of 5 × 10−7 torr is located 7 meters downstream from the source point. Because there is no window at the entrance of the chamber, a differential pumping system is needed. The chamber is equipped with a mask-wafer system, driven by a third stepping motor.

VUV-SX spherical grating monochromator beam lines at BEPC and HESYRL

Two VUV-SX spherical grating monochromator (SGM) beam lines have been designed and constructed for laboratories in China; one for the Beijing Electron-Positron Collider (BEPC) and one for the Hefei Synchrotron Radiation Laboratory (HESYRL). Each of them will cover a wide spectral range, approximately 10–1000 eV, with four or five spherical laminar gratings. Tuning of the wavelength in the monochromators is achieved by rotation of the grating and translation of a pair of stepping-motor-driven slits to follow the Rowland circle to improve the monochromator's performance. The prefocusing mirrors are different on the BEPC and HESYRL beam lines. To accept 20 mrad of the synchrotron radiation horizontally from the 800-MeV HESYRL ring, a combined Kirkpatrick-Baez-type mirror set has been developed. The 1240-mm-long horizontal prefocusing mirror consists of four 310 mm × 70 mm × 40 mm gold-coated Zerodur spherical mirrors, each of which is independently adjustable in three dimensions. In the BEPC SGM beam line, a toroidal nickel-coated aluminum prefocusing mirror intercepts up to 4.5 mrad at a distance of 12 m from the source. A heat-pipe cooling system has also been designed for this mirror to accommodate the higher power from the 2.2–2.8 GeV beam stored in BEPC in its dedicated SR mode. The optical ray tracing results, the mechanics, and control systems are described in this paper.

Hefei National Synchrotron Radiation Laboratory

The Hefei Synchrotron Radiation Laboratory attached to the University of Science and Technology of China is a dedicated VUV and soft X-ray synchrotron radiation light source. In the present work the design of the machine is presented and the main parameters listed.

Soft X-ray microscopy at the Hefei synchrotron radiation laboratory

Scanning soft X-ray microscopy and contact microscopy are planned at HFSYRL, USTC. The design of a scanning X-ray microscope in which a microzoneplate will be acting as a focusing element and the specimen will be scanned through the focal spot mechanically under computer control is discussed. We have performed some studies with a homebuilt stationary soft X-ray source. The equipment will be interfaced to a SR are in future.

The Major Accelerator Projects in China

The development of accelerators in China began after the founding of the Republic in 1949. Among the milestones are a Van de Graaff of 2.3 MV in 1959, a 25 MeV betatron in 1963, a 1.2m cyclotron and an electron linear accelerator of 30 MeV together with its 14 MW high power klystron in 1964, and a 10 MeV proton linac in 1982. Some medium and high energy accelerators are currently under construction. The major projects are the Beijing Electron Positron Collider of 2.2 to 2.8 GeV, the Lanzhou Heavy Ion Research Facility of 100-5 MeV/A, and the Hefei Synchrotron Radiation Laboratory of 800 MeV. These projects and their purposes are described.

Preliminary design of a 6 pole, 5 T wiggler for the Hefei synchrotron light source

The preliminary design of a 6 pole, 5 tesla wiggler for the Hefei synchrotron light source is described and the expected performance is considered.

The Hefei Synchrotron Radiation Laboratory (HESYRL): An 800 MeV electron storage ring and its synchrotron radiation experiment area

A group of physicists and engineers at the University of Science and Technology of China (USTC), to which we belong, is now planning a synchrotron radiation facility. The project has recently been authorized by the Chinese Academy of Science and is going to be put in to construction at Hefei, an East-China city, in a few months. The facility will be an intermediate-energy electron accelerator dedicated to synchrotron radiation research. It will be operated by a newly-established laboratory, to be called the Hefei Synchrotron Radiation Laboratory, or HESYRL for short, and guided by the USTC. This is the first serious effort made by Chinese scientists to join the world in this flourishing and fruitful research field.