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The operational calendar for 2003 has scheduled 6552 hours of operation of which 4920 hours dedicated to User operation. Beam energy for the calendar year is 2.0 GeV for 74% of the time and 2.4 GeV for the remaining time. The overall User uptime to date has been 90.4% (92.1 excluding storms) with the main causes of downtime due to storms, the commissioning of the third harmonic cavity, linac and difficulties with refills. Of the many activities performed during the machine shutdowns the most notable has been the putting into operation of the third harmonic cavity that has significantly improved operational behaviour and, together with the fast multi-bunch feedbacks, the quality of the beam. A further important shutdown activity, to be performed during the last quarter of the year, is the measurement and re-alignment of the storage ring magnets.

Many improvements have also been made to accelerator systems during the year. On the side of control electronics and software there has been the continued upgrade to a two level architecture that adopts new CPU boards for the front-end computers. The upgrade renews control hardware that is becoming obsolete and adds new features. Two complete subsystems, insertion devices and the radio-frequency (RF) plants, have been equipped with the new controllers and an additional seven vacuum controllers will be installed by the end of the year. In the control room the high-level software program 1bm (one button machine) has been redesigned and rewritten. 1bm automates and optimises the long sequence of operations required during a refill, that includes, magnet cycling, injection, energy ramping, orbit correction and insertion device management, to mention a few. The new version has improved performance and robustness. The electronics controlling the RF phase and higher order mode (HOM) shifters have been upgraded. The RF plants have also been equipped with mains stabilisers that increase the stability of the amplitude and phase of the RF output power. An upgrade of the phase loop electronics has started that allow an increase of the correction factor of the loop, permit increased bandwidth and the possibility to perform phase modulation of the RF signals for beam manipulation. An important improvement of the effectiveness of the correction of residual closed orbit distortions from insertion devices has been initiated. For this the correction coils, associated power supplies and feedforward control hardware for section 2, 3 and 6 insertion devices will be upgraded. Moreover, the upgrade will permit correction of individual modules of the full insertion device.

For what regards mechanical upgrades, the vacuum chamber in straight section 7 was replaced during the June shutdown. Together with the new thinner three-meter long NEG-coated aluminium vacuum chamber the straight section includes two new low-gap beam position monitors (BPM) for orbit feedback systems, two additional BPMs dedicated to the multi-bunch feedback systems and the machine scrapers. The latter were removed from straight section 11 following the installation of the superconducting wiggler.

Activities on photon sources have principally concentrated on the insertion devices for the second X-ray and IUVS beamlines and modifications to the bending magnet chamber for the infra-red beamline. During the year the installation and final commissioning of the second Figure-8 undulator module for the IUVS beamline took place. No significant perturbation is observed on storage ring beam dynamics when closing the insertion device to the minimum gap of 19 mm and undulator control is freely allowed to beamline users. Radiation spectra measured at the experimental station show good agreement with the predicted peak wavelength and intensity.

The superconducting wiggler (manufactured in BINP, Novosibrisk) will produce 14 times more photon flux at 25 keV compared to the present permanent magnet device for the second X-ray diffraction beamline. The wiggler installed in the autumn of 2002 has been studied under differing operational conditions. Both the power mode (where the magnet is permanently connected to its power supplies) and the persistent current mode (where a stationary current is circulating in the superconducting coils) were successfully tested. An upgrade to the vacuum chamber (modifications to the tapers and copper liner) will be performed during the next quarter to lower the consumption of liquid helium. The wiggler has been installed in section 11 of the storage ring next to the superconducting third harmonic cavity. A future upgrade to both cryogenic systems foresees to deliver liquid Helium from the cavity liquefier to the wiggler dewar and a combined helium recovery scheme.

The installation of the new infrared beamline, which is foreseen in the early 2004, has required the development of new type of exit port for the beamline itself. Modification to machine components has centred on the bending magnet vacuum chamber, the photon absorber and the photon shutter. These modifications will allow a horizontal acceptance angle of 70 mrad and 25 mrad in the vertical plane. The horizontal acceptance allows both edge and main magnet infrared radiation. The requirements of the new beamline, in particular the vertical acceptance, have also required a new vacuum chamber design based on previous experience with aluminium constructs. While the photon absorber was just modified, the shutter component has been completely redrawn for the layout requirements of the beamline.

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An important result of the last few months is the successful operation of the storage ring free electron laser (FEL) in the so-called Q-switching mode. This is performed by periodically modulating the main RF oscillator in such a way that laser pulses are generated with a regular time structure (following the RF signal modulation) and with increased output intensity. This is believed to be particularly useful for the planned time-resolved experiments that would benefit from the more predictable macro-temporal structure compared to the natural regime. A procedure to energy down-ramp the storage ring was also tested and enabled to lase for the first time at 750 MeV. The advantage of low beam energy consists in a corresponding reduction of synchrotron radiation power that is responsible for the fast degradation of mirrors used in the optical cavity.

On-going synchrotron radiation tests of different single and multi-layer mirror samples are an important part of the European collaboration (EUFELE contract). The characterization of these samples before and after exposure allows a significant database of material properties to be built up. The database is then used to optimise the production process and the choice of materials that lead to FEL compliant mirrors for the VUV spectral region.

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A common problem of all intermediate energy third generation light sources is the short beam lifetime that arises from a small beam emittance. Such machines have high bunch densities and correspondingly increased elastic intra-beam collisions that lead to particle loss, i.e., the Touschek effect. To circumvent this effect the bunch is diluted by increasing its length while maintaining the all-important transverse emittance. A cavity operating at a higher harmonic of the main RF system, when appropriately phased, will lengthen the bunch without introducing increased energy spread. A superconducting third harmonic cavity was chosen and put into operation during the year. The system provides both an increase in lifetime, through bunch lengthening, and the Landau damping of longitudinal multi-bunch instabilities. The system installed during the later half of 2002 underwent a series of adjustments by the manufacturer followed by a period of commissioning early this year. The cavity is now in routine operation at 2.0 GeV and 320 mA, where the improvement in beam lifetime attains to more than a factor of three and a full damping of longitudinal beam instabilities is provided. The cavity has been activated also during user’s run at 2.4 GeV, 140 mA, where it provides an increase in lifetime up to 50% of the nominal value.

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Activities with the transverse multi-bunch feedback system have progressed with the putting into operation of the second system acting in the horizontal plane. Prior to this system, horizontal instabilities were suppressed by acting on the harmonic sextupoles to provide Landau damping. The sextupole settings, however, were not optimal for a long beam lifetime. The two transverse multi-bunch feedback systems have enhanced the effectiveness of User operation through a considerable gain in beam lifetime. Machine operation with the systems allows nominal optics to be used with a consequent increase also in dynamic aperture. In this configuration together with the operation of the third harmonic cavity, a beam free of coupled-bunch instabilities is delivered to Users also at 2.0 GeV. Since installation, the operational behaviour of the two systems has been effective and reliable. They are integrated into the control system with initialisation, run and standby routines that are fully automatic and easily activated from standard control room panels. 

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First extensive tests of the longitudinal multi-bunch feedback were performed during the start of the year. The longitudinal feedback digital processing electronics take advantage of the same kind of hardware developed for the already operating transverse feedback, so that individual digital filters are executed for each of the 432 2-ns spaced bunches. Principal differences exist on the front end (detector electronics) and the back end (RF modulator, RF amplifier and kicker). Commissioning results have been positive and by activating the system from the beginning of the injection process up to 280 mA of longitudinally stable beam at 0.9 GeV have been accumulated. At present the system is not used for User operation since the third harmonic cavity naturally damps longitudinal instabilities when operating in bunch lengthening mode. The system has, however, been effectively operated for the suppression of longitudinal instabilities of the 4-bunch beam used by the storage ring FEL.

Maintaining a transversely stable closed orbit is of fundamental importance. Towards this goal high resolution and high accuracy beam position monitors (low gap BPM’s) have been developed for insertion device straight sections. The installation of these monitors is being systematically pursued. At the same time upgraded detector electronics are being tested on both the standard rhomboidal and low gap BPM’s to be used in either local or global orbit feedback systems. One such complete feedback sub-station is being used for the local orbit correction tests in sections 1 and 2, where both the ‘old-type’ rhomboidal and low-gap BPMs are respectively installed. In section 2, in particular, the feedback has been positively closed on both the horizontal and vertical planes using a PID (Proportional, Integral, Derivative) controller. Beam noise induced by the mains at 50 Hz and at higher harmonics is removed by specific harmonic suppressors. The feedback software, which runs on a PowerPC CPU board under the Linux operating system with a real-time extension, can manage system saturation and periodically transfers the accumulated DC correction contribution to the already existing DC orbit correction schemes.

The upgrade of the storage ring RF system is necessary to handle the RF power requirements of the full set of insertion devices and to allow operational overhead. The first phase of the upgrade is the substitution of one of the original 60 kW amplifiers with a 150 kW plant. The substituted plant will be used to power the booster RF system. The detailed evaluation of the offers received in reply to the call for tender has been completed. The upgrade, based on Inductive Output Tubes (IOT’s), will use two 80 kW tubes combined by means of a switchless combiner and allows the operation of each IOT in stand-alone mode if necessary. This option has been preferred compared to the use of three 50 kW tubes for reasons of cost and space. The cooling and electrical supplies for the new plant will also be upgraded. The RF cavity, an improved version of the original and already power conditioned, will replace the one in section 9. The new cavity features an upgraded cooling system that allows operation at a higher gap voltage corresponding to 60 kW wasted power on the cavity walls. The newly designed input power-coupler also doubles the RF power to the cavity from the present 60 to 120 kW. Finally also the HOM frequency shifter is of the new concept, free of RF contacts, which will allow use of the full shifting range, at full cavity power (60 kW). Installation will be performed during the last quarter of 2003.

The full energy injector for the storage ring is composed of a 100 MeV pre-injector linac and a 2.5 GeV booster synchrotron with a repetition frequency of 3 Hz. The 100 MeV pre-injector linac for the booster is presently being assembled using two 50 MeV accelerating sections donated by CERN. The in house construction of the modulator for the klystron of the pre-injector has been completed and undergoing tests. Specifications and signal handling for the pre-injector control system are well established and will adopt a voltage-to-frequency conversion technique. After the successful test of the prototypes series production has started. Progress is also well underway for the electronics of the gun.

The system for beam injection into the booster is composed of a septum magnet and a fast kicker magnet, while extraction is performed by a set of bumper magnets, kickers and an extraction septum. The call for tender for the septum magnets for injection and extraction from the booster and those for the upgrade of injection into the storage ring was made early this year. Delivery of all three systems is foreseen in the coming six months. The booster will be built to operate in top-up mode necessitating reliable operation of all parts. In view of this, tests to identify critical components of the septum magnet power circuit were performed on a prototype and the six units of the series production are now being assembled.

The design of the fast kicker magnets, based on in-vacuum ferrite magnets, is progressing A prototype will then be constructed along with a prototype of the kicker high voltage pulsed power supply to perform tests on a complete unit. The booster synchrotron is a two-fold symmetric lattice with long straight sections for injection and extraction. The lattice is composed of bending magnets, two types of quadrupoles and sextupoles. Specifications for the bending and quadrupole magnets have been reviewed and are now available in their final version together with the specification for the steerer magnets. The RF system for the booster is composed of a DESY type five cell cavity powered by one of the storage ring amplifiers that will be available after the RF upgrade. The cavity was delivered at the end of May and is currently being measured in the RF laboratory and will soon undergo full RF power tests. Development activities for other systems, such as power supplies, controls, interlocks, access control, diagnostics and vacuum have also advanced. For the diagnostics a new version of the fluorescent screen is being developed and a prototype constructed, with a combined thermal and mechanical design, for use in both transfer lines and the booster. The associated image acquisition and analysis system after being tested in the laboratory is being installed on the storage ring synchrotron radiation profile monitor where it will upgrade the existing system. The first detectors adopted for the booster BPMs have been installed on the ELETTRA linac and transfer line for characterisation with beam.

Civil engineering activities are going ahead with the construction of the second part of the new injector building that is scheduled in the coming months. This part of the building includes the electrical service area, the bridge connecting the existing control room and a part of the booster tunnel in the injection area.

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