BESSY II

The construction of the main building is well advanced, and is expected to be complete in Dec. '96. The installation of the 10 Hz 1.9 GeV booster is now in progress and commissioning will start in a few months, aiming for a full energy beam in April 1997. The storage ring main magnets are being measured and the main magnet power supplies are being tested and delivered. The DORIS r.f. cavities will be installed in the next few months. The technique of explosion bonding copper to stainless steel has successfully been used for the construction of the vacuum chamber radiation absorbers. It has been found that stringent quality control is very important to eliminate some defects that were observed. The first ID structures are being mechanically tested and an ID of 49 mm period length will be ready in the following weeks. First beam is being aimed for mid 1998 with user operation in January 1999. Six beamlines from insertion devices and eight from bending magnets should be available at an early stage of the project. The present plan is that BESSY I will run in parallel with BESSY II for about two years and then be shutdown in 2001.

ANKA

The "green light" for the ANKA project was given on March 12th 1996. The facility, (50 MeV microtron/500 MeV 10 Hz booster/2.5 GeV storage ring) will be housed in a large 60 m x 60 m building. The lattice is presently being defined along with the power supplies, radio frequency components, vacuum and injection. For the control system two possibilities are being examined, the ESRF system and a field bus concept using PC's. The lattice is a "double DBA" type, recently modified to be asymmetric with two long (6.8 m) and two short (3.8 m) straight sections. The circumference is 103.2 m and the emittance 88 nmrad with zero dispersion, or 45 nmrad with non-zero dispersion in the long straights, at the same working point. The dynamic aperture is sufficient in either case even without using harmonic sextupoles. The main magnets have been redesigned and the quadrupoles are the same as BESSY II. Four ELETTRA type cavities will be placed in the dispersive sections, one in each arc, which will be sufficient for a beam current of 200 mA. A new solution with two cavities fed by a 250 kW klystron is being considered. For 400 mA two more cavities are required. A simple design for the booster having four 90° bending magnets is being examined.

SLS

Changes to the lattice design have resulted in an increase of the circumference to 288 m. There are now 3 long straight sections of 12 m, 3 of 7 m and 6 short sections of length 4m, the latter with low b values for small gap and high field insertion devices. The original 16 m long straights have been reduced to 12 m on the advice of the Scientific Advisory Committee. The emittance is 2.8 nmrad, 1.9 nmrad with non-zero dispersion in the shorter straight sections. The energy acceptance has been increased to 6%. The required r.f. voltage of 4 MV is obtained with a two phase r.f. system: ELETTRA-type normal conducting cavities will provide 2.2 MV, augmented by a passive superconducting cavity. The possibility of including superconducting bends in the TBA lattice is still open, but there is also the option of superconducting wavelength shifters in the short straights.

The injection system is made up of a 100 MeV linac and a 2.4 GeV maximum energy booster synchrotron. The booster is a combined function machine housed in the storage ring tunnel with a low 5 nmrad emittance that would be beneficial for topping-up. A simple 20 mm steel vacuum chamber without reinforcement is proposed; work is in progress to reduce the cost of the vacuum pumps for the long, poor conductance chamber. A 2 MeV r.f. gun is already working delivering half of the required current. Conventional and laser driven cathode guns are also being examined.

A final version of the building design will be ready by mid December 1996, selected from four competitive proposals. The service gallery and control room will be housed inside the building. The floor is a 50 cm reinforced slab, with no expansion joints, based on the APS philosophy. To lower the costs steel pillars and a wooden roof will be used.

The present preparation phase is funded by the PSI running budget. The final Parliamentary decision is expected in June '97, when it is hoped to start the ordering of components.

SOLEIL

Construction of SOLEIL is expected to commence in 1999 and begin operations in 2003. In 2001 the present machines at LURE will stop operation. Several major design options have recently been revised. The injector will now be exclusively an electron machine rather than positron; the shorter linac implies that the linac and booster can now be placed inside the storage ring. The ring energy has been increased from 2.15 GeV to 2.5 GeV so that the requirement for 10 keV photons can be met more easily with a 15 mm gap undulator (U3.4) rather than the previous 4 mm (U1.6). The change in energy requires an increase in the length of the dipole magnets, which are already 1.6 T. In addition, the lattice has been modified to recover an emittance of 3 nmrad. The 16-cell lattice will provide 4 long straight sections of 14 m (required for the FEL) and 12 of 7 m. The r.f. system will be based on mono-mode 353 MHz superconducting cavities, providing an accelerating voltage of 2.3 MV, giving an energy acceptance of 4%. The cavities will be developed by a collaboration between CERN, ESRF, SOLEIL and DIAMOND; a full power test of a cavity is planned for the end of '98. Additional developments foresee the use of individual power supplies for the storage ring quadrupoles, thinner vacuum chamber, transverse orbit feedback, IR-FEL. The ESRF-DESY beamline control system will be used. The r.f. frequency of the booster has been changed from 100 MHz to 353 MHz; a decision has yet to be made on the repetition frequency, either 1 or 10 Hz.

SRS Upgrade

The SRS upgrade is seen as a "technology demonstrator" for the DIAMOND project, and involves the installation of two 9-pole 2T multipole wigglers providing up to 20-30 keV photons for 4 new experimental stations. The project has been approved and funding should start in Jan. 1997. The placement of the wigglers requires a complete relocation of the r.f. system. The novel vacuum chambers for the devices will be constructed from titanium (1.2 m flange to flange) with a beam stay clear of 15 mm and magnet gap of 19 mm.

DIAMOND

The present 3 GeV racetrack lattice has 2 long (20 m) and 14 short (5 m) straight sections with an emittance of 14 nmrad. Six families of harmonic sextupoles are required to give a dynamic aperture that exceeds the ±20 mm horizontal aperture, however this is reduced significantly at 3 % momentum deviation. Steerer magnets will be provided by additional coils in the sextupole magnets. Extensive studies show little reduction of dynamic aperture due to the insertion devices. A superconducting r.f. system (cf. SOLEIL) is being considered. Various options for replacing pairs of conventional dipole with 4.3 T superconducting dipoles have been studied. The design of the full energy booster synchrotron is based on a double FODO cell structure with sextupoles in alternate straights. Current work involves finalising the feasibility report, including a detailed costing, reviewing the super-long straights and considering other machine symmetries, as well as identifying possible funding sources and mechanisms.

LSB

The 2.5 GeV, 12-cell TBA lattice and its main components have now been fixed. The lattice provides low emittance (8 nmrad) and potential for future upgrades: an increase in energy to 3.0 GeV, inclusion of super-conducting bending magnets and low-beta sections. The momentum acceptance is 2.3%. A laboratory is being built for magnetic measurements and there are plans for the construction of a prototype bending magnet and insertion device. A first set of generic beamlines are being studied. A feasibility study should be produced by Sep./Oct. 1997.

prepared by C.J. Bocchetta and R.P. Walker